@article{kungsadalpipob_lubna_bradford_2024, title={Novel three-dimensional printed continuous Zylon yarn reinforced polylactic acid composites utilizing compatible sizing}, ISSN={["2363-9520"]}, DOI={10.1007/s40964-023-00549-x}, journal={PROGRESS IN ADDITIVE MANUFACTURING}, author={Kungsadalpipob, Patrapee and Lubna, Mostakima M. and Bradford, Philip D.}, year={2024}, month={Jan} }
 @article{zhang_kowalik_mao_damirchi_zhang_bradford_li_duin_zhu_2023, title={Joint Theoretical and Experimental Study of Stress Graphitization in Aligned Carbon Nanotube/Carbon Matrix Composites}, volume={15}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.3c03209}, abstractNote={Stress graphitization is a unique phenomenon at the carbon nanotube (CNT)-matrix interfaces in CNT/carbon matrix (CNT/C) composites. A lack of fundamental atomistic understanding of its evolution mechanisms and a gap between the theoretical and experimental research have hindered the pursuit of utilizing this phenomenon for producing ultrahigh-performance CNT/C composites. Here, we performed reactive molecular dynamics simulations along with an experimental study to explore stress graphitization mechanisms of a CNT/polyacrylonitrile (PAN)-based carbon matrix composite. Different CNT contents in the composite were considered, while the nanotube alignment was controlled in one direction in the simulations. We observe that the system with a higher CNT content exhibits higher localized stress concentration in the periphery of CNTs, causing alignment of the nitrile groups in the PAN matrix along the CNTs, which subsequently results in preferential dehydrogenation and clustering of carbon rings and eventually graphitization of the PAN matrix when carbonized at 1500 K. These simulation results have been validated by experimentally produced CNT/PAN-based carbon matrix composite films, with transmission electron microscopy images showing the formation of additional graphitic layers converted by the PAN matrix around CNTs, where 82 and 144% improvements of the tensile strength and Young's modulus are achieved, respectively. The presented atomistic details of stress graphitization can provide guidance for further optimizing CNT-matrix interfaces in a more predictive and controllable way for the development of novel CNT/C composites with high performance.}, number={27}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Zhang, Liwen and Kowalik, Malgorzata and Mao, Qian and Damirchi, Behzad and Zhang, Yongyi and Bradford, Philip D. and Li, Qingwen and Duin, Adri C. T. and Zhu, Yuntian T. T.}, year={2023}, month={Jun}, pages={32656–32666} }
 @article{marashi_bradford_peters_2023, title={Laser Doppler vibrometry measurements of acoustic attenuation in optical fiber waveguides}, volume={62}, ISSN={["2155-3165"]}, DOI={10.1364/AO.483827}, abstractNote={Fiber Bragg grating (FBG) sensors have been widely applied for structural health monitoring applications. In some applications, remote bonding of the optical fiber is applied, where ultrasonic waves are coupled from the structure to the optical fiber and propagated along the fiber to the FBG sensor. The distance that this signal can propagate along the optical fiber without decaying below a threshold value can be critical to the area of the structure that can be monitored per sensor. In this paper, we develop a method to measure the acoustic mode attenuation of fiber waveguides based on laser Doppler vibrometry (LDV) that is independent of the fiber type. In order to validate the method, we compare attenuation measurements on single-mode optical fibers using both the LDV and FBG sensor methods. Once the method is validated, experimental measurements of different coated and uncoated optical fibers are performed to quantify the role of the fiber diameter on the attenuation coefficient. As the radius of the waveguide decreases, the signal attenuation increases exponentially.}, number={16}, journal={APPLIED OPTICS}, author={Marashi, Cameron Sepehr and Bradford, Philip and Peters, Kara}, year={2023}, month={Jun}, pages={E119–E124} }
 @article{hossain_lubna_bradford_2023, title={Multifunctional and Washable Carbon Nanotube-Wrapped Textile Yarns for Wearable E-Textiles}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.2c19826}, abstractNote={Carbon nanotube (CNT) yarns are promising for wearable electronic applications due to their excellent electromechanical and thermal properties and structural flexibility. A spinning system was customized to produce CNT-wrapped textile yarns for wearable applications. By adjusting the spinning parameters and core yarn, a highly tailored hybrid CNT yarn could be produced for textile processing, e.g., knitting and weaving. The electrical resistance and mechanical properties of the yarn are influenced by the core yarn. The high flexibility of the yarn enabled state-of-the-art three-dimensional (3D) knitting of the CNT-wrapped yarn for the first time. Using the 3D knitted technology, CNT-wrapped textile yarns were seamlessly integrated into a wrist band and the index finger of a glove. The knitted structure exhibited a large resistance change under strain and precisely recorded the signal under the different movements of the finger and wrist. When the knitted fabric was connected to a power source, rapid heating above skin temperature was observed at a low voltage. This work presents a novel hybrid yarn for the first time, which sustained 30 washing cycles without performance degradation. By changing the core yarn, a highly stretchable and multimodal sensing system could be developed for wearable applications.}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Hossain, Md Milon and Lubna, Mostakima M. and Bradford, Philip D.}, year={2023}, month={Jan} }
 @article{hossain_li_sennik_jur_bradford_2022, title={Adhesive free, conformable and washable carbon nanotube fabric electrodes for biosensing}, volume={6}, ISSN={["2397-4621"]}, DOI={10.1038/s41528-022-00230-3}, abstractNote={Abstract Skin-mounted wearable electronics are attractive for continuous health monitoring and human-machine interfacing. The commonly used pre-gelled rigid and bulky electrodes cause discomfort and are unsuitable for continuous long-term monitoring applications. Here, we design carbon nanotubes (CNTs)-based electrodes that can be fabricated using different textile manufacturing processes. We propose woven and braided electrode design using CNTs wrapped textile yarns which are highly conformable to skin and measure a high-fidelity electrocardiography (ECG) signal. The skin-electrode impedance analysis revealed size-dependent behavior. To demonstrate outstanding wearability, we designed a seamless knit electrode that can be worn as a bracelet. The designed CNT-based dry electrodes demonstrated record high signal-to-noise ratios and were very stable against motion artifacts. The durability test of the electrodes exhibited robustness to laundering and practicality for reusable and sustainable applications.}, number={1}, journal={NPJ FLEXIBLE ELECTRONICS}, author={Hossain, Md. Milon and Li, Braden M. M. and Sennik, Busra and Jur, Jesse S. S. and Bradford, Philip D. D.}, year={2022}, month={Dec} }
 @article{li_vallabh_bradford_kim_seyam_2022, title={Development of hull material for high-altitude airship: A parametric study}, volume={1}, ISSN={["1530-7964"]}, DOI={10.1177/07316844211054852}, abstractNote={The development of hull material with ideal properties to meet all the operation requirements has posed the greatest challenge to flying the airship at high altitude for extended periods. Materials developed in our previous study with a laminated structure achieved high strength-to-weight ratio and excellent gas barrier property at a relatively low total weight. To optimize this novel design and obtain a more comprehensive understanding of the laminate properties, a parametric study involving lamination process parameters (temperature and time), and laminate structural parameter (reinforcement fabric construction), was conducted. The effects of lamination parameters on tensile, peel, tear and helium permeability tests were carried out to assess the laminates. It was found that the tensile strength of the laminate is predominantly determined by the fabric reinforcement material properties. The peel and tear strength results showed that increasing the lamination temperature from 185°C to 200°C improved respective strength values. Additionally, the analysis of failure modes and tear propagation suggested that laminate samples with progressive failure have better tear resistant property over those with brutal failure. Extremely low helium permeability was achieved, yet the gas barrier property was not affected by the lamination process parameters and fabric type.}, journal={JOURNAL OF REINFORCED PLASTICS AND COMPOSITES}, author={Li, Ang and Vallabh, Rahul and Bradford, Philip D. and Kim, David and Seyam, Abdel-Fattah M.}, year={2022}, month={Jan} }
 @article{suh_twiddy_mahmood_ali_lubna_bradford_daniele_gluck_2022, title={Electrospun Carbon Nanotube-Based Scaffolds Exhibit High Conductivity and Cytocompatibility for Tissue Engineering Applications}, volume={7}, ISSN={["2470-1343"]}, url={https://doi.org/10.1021/acsomega.2c01807}, DOI={10.1021/acsomega.2c01807}, abstractNote={Carbon nanotubes (CNTs) are known for their excellent conductive properties. Here, we present two novel methods, “sandwich” (sCNT) and dual deposition (DD CNT), for incorporating CNTs into electrospun polycaprolactone (PCL) and gelatin scaffolds to increase their conductance. Based on CNT percentage, the DD CNT scaffolds contain significantly higher quantities of CNTs than the sCNT scaffolds. The inclusion of CNTs increased the electrical conductance of scaffolds from 0.0 ± 0.00 kS (non-CNT) to 0.54 ± 0.10 kS (sCNT) and 5.22 ± 0.49 kS (DD CNT) when measured parallel to CNT arrays and to 0.25 ± 0.003 kS (sCNT) and 2.85 ± 1.12 (DD CNT) when measured orthogonally to CNT arrays. The inclusion of CNTs increased fiber diameter and pore size, promoting cellular migration into the scaffolds. CNT inclusion also decreased the degradation rate and increased hydrophobicity of scaffolds. Additionally, CNT inclusion increased Young’s modulus and failure load of scaffolds, increasing their mechanical robustness. Murine fibroblasts were maintained on the scaffolds for 30 days, demonstrating high cytocompatibility. The increased conductivity and high cytocompatibility of the CNT-incorporated scaffolds make them appropriate candidates for future use in cardiac and neural tissue engineering.}, number={23}, journal={ACS OMEGA}, publisher={American Chemical Society (ACS)}, author={Suh, Taylor C. and Twiddy, Jack and Mahmood, Nasif and Ali, Kiran M. and Lubna, Mostakima M. and Bradford, Philip D. and Daniele, Michael A. and Gluck, Jessica M.}, year={2022}, month={Jun}, pages={20006–20019} }
 @article{yan_zhou_cheng_orenstein_zhu_yildiz_bradford_jur_wu_dirican_et al._2022, title={Interconnected cathode-electrolyte double-layer enabling continuous Li-ion conduction throughout solid-state Li-S battery}, volume={44}, ISSN={["2405-8297"]}, DOI={10.1016/j.ensm.2021.10.014}, abstractNote={All-solid-state lithium (Li) batteries with high energy density are a promising solution for the next-generation energy storage systems in large-scale devices. To simultaneously overcome the challenges of poor ionic conduction of solid electrolytes and shuttling of active materials, we introduce a functional electrolyte-cathode bilayer framework with interconnected LLAZO channels from the electrolyte into the cathode for advanced solid-state Li-S batteries. Differing from the traditional solid-state batteries with separated layer compositions, the introduced bilayer framework provides ultrafast and continuous ion/electron conduction. Instead of transferring Li+ across the polymer and garnet phases which involve huge interfacial resistance, Li+ is directly conducted through the LLAZO channels created continuously from the cathode layer to the solid electrolyte layer, significantly shortening the diffusion distance and facilitating the redox reaction of sulfur and sulfides. A stable cycle life is demonstrated in the prototype Li-S solid-state batteries assembled with the introduced [email protected] interconnected bilayer framework. High capacity is obtained at room temperature, indicating the superior electrochemical properties of the bilayer framework that result from the unique design of the interconnected LLAZO garnet phase.}, journal={ENERGY STORAGE MATERIALS}, author={Yan, Chaoyi and Zhou, Ying and Cheng, Hui and Orenstein, Raphael and Zhu, Pei and Yildiz, Ozkan and Bradford, Philip and Jur, Jesse and Wu, Nianqiang and Dirican, Mahmut and et al.}, year={2022}, month={Jan}, pages={136–144} }
 @article{yildiz_lubna_ramesh_ozturk_bradford_2022, title={Microporous vertically aligned CNT nanocomposites with tunable properties for use in flexible heat sinks}, volume={7}, ISSN={["2468-2179"]}, DOI={10.1016/j.jsamd.2022.100509}, abstractNote={Effective thermal management of electronic systems depends on the heat transfer efficiency or the heat dissipation capability and the thermal conductivity of heat sink components, which has a critical impact on the performance of the devices. The rapidly growing field of microelectronics creates an enormous need for next-generation flexible, lightweight heat sinks. In this work, flexible, microporous nanocomposites are fabricated utilizing a unique yet easily tunable processing method, targeting heat-sink applications. The highly porous and low-density nanohybrid structures were fabricated in a unique processing technique using conformally pyrolytic carbon (PyC) coated vertically aligned carbon nanotube (VACNT) arrays and polydimethylsiloxane (PDMS) infiltration. Simply by varying the concentration of the PDMS in the VACNT structure, the microporosity can be tuned from 50% to 93%, and at the same time, the density of the structure varies from 0.11 g/cm3 to 0.51 g/cm3. The through-thickness thermal conductivity of the VACNT – PDMS nanocomposites did not vary substantially with increasing PDMS concentration, and the highest performance samples exhibited 14.1 W/mK thermal conductivity. The highly flexible nanocomposite structure also showed excellent mechanical resiliency and exhibited complete recovery from 80% compressive strain. The final heat-sink structure with fins was fabricated by a controlled laser etching technique. Analysis of the flexible VACNT array heat sink showed a significant ∼27% reduction in thermal resistance with an air velocity of 1.5 m/s and about ∼40% improvement in the output performance of a thermoelectric generator (TEG) on which it was mounted. The high thermal conductivity of VACNTs and the large surface area provided by the microporous structure, as well as the laser-etched fins, all together contributed to better thermal management performance.}, number={4}, journal={JOURNAL OF SCIENCE-ADVANCED MATERIALS AND DEVICES}, author={Yildiz, Ozkan and Lubna, Mostakima M. and Ramesh, Viswanath P. and Ozturk, Mehmet and Bradford, Philip D.}, year={2022}, month={Dec} }
 @article{garmabi_elamin_bradford_pankow_2022, title={Understanding the role of bond point strain in the mechanical response of nonwoven polypropylene materials}, ISSN={["1530-793X"]}, DOI={10.1177/00219983221087332}, abstractNote={A method was developed to study micromechanics of a bond point in nonwoven polypropylene materials. The micromechanical behavior of the thermal bonded nonwovens was studied using the digital image correlation (DIC) technique to understand the bond points deformation during mechanical stretching. An electrospray technique was used as a fast and reliable method to create the speckle pattern on the nonwovens. Various parameters of the electrospraying and their influence on the pattern accuracy and repeatability was studied and the best pattern in terms of dot size and distribution was determined from experimentation. Plasma treatment also proved to be essential to enhance the uniform distribution and adherence of the particles on the surface. Unloaded DIC experiments were carried out and proved the accuracy of technique with errors of lower than 0.5% strain. An automated high-resolution tensile apparatus was built and loaded DIC experiments were carried out using the device. The fabric was tested in Machine Direction (MD) direction and Cross Direction (CD) directions, both showing good correlation with low errors. Average strain values in bond points were plotted against total strain in fabric and the results showed noticeable amounts of strains developed in the bond points, contradictory to most of the FEM models which consider no deformation in the bond points. Results also indicated that in MD direction deformation, bond points can experience more than 30% of the overall strain presented in the fabric.}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Garmabi, Alireza and Elamin, Mohamed A. and Bradford, Philip D. and Pankow, Mark}, year={2022}, month={Apr} }
 @article{aly_muhuri_bradford_2021, title={Fabrication of scalable, aligned and low density carbon nanotube/silicon carbide hybrid foams by polysilazane infiltration and pyrolysis}, volume={41}, ISSN={["1873-619X"]}, DOI={10.1016/j.jeurceramsoc.2020.12.035}, abstractNote={Polymer-derived ceramic (PDC) process is an attractive technique that has high ceramic yield. This versatile method allows for fabrication of porous carbon nanotube (CNT)/ silicon carbide (SiC) hybrid materials that is important high temperature structural applications. Although several forms of CNT assemblies have been used with the PDC approach, the fabricated CNT/ceramic nanocomposites were either one or two dimensional. Herein, we report, for the first time, the fabrication of a low density, three-dimensional (3D) and scalable CNT/SiC structure using PDC technique. It was synthesized by impregnating preceramic polysilazane (PSZ) into ultralow density, anisotropic, and highly aligned CNT foams, followed by thermosetting and pyrolysis processes. The ceramic phase conformally coated the CNTs. The X-ray diffraction (XRD) diffractogram confirmed the presence of β-SiC crystalline phase. The resulting hybrid foam inherited the morphology and form factor of the original CNT foam, and possessed mechanical robustness, improved electrical properties, and extraordinary thermal stability.}, number={6}, journal={JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, author={Aly, Karim and Muhuri, Abir K. and Bradford, Philip D.}, year={2021}, month={Jun}, pages={3303–3313} }
 @article{zhang_ma_zhang_bradford_zhu_2021, title={Length-dependent carbon nanotube film structures and mechanical properties}, volume={32}, ISSN={["1361-6528"]}, DOI={10.1088/1361-6528/abef92}, abstractNote={We investigated the microstructures of carbon nanotube (CNT) films and the effect of CNT length on their mechanical performance. 230 μm-, 300 μm-, and 360 μm- long CNTs were grown and used to fabricate CNT films by a winding process. Opposite from the length effect on CNT fibers, it has been found that the mechanical properties of the CNT films decrease with increasing CNT length. Without fiber twisting, short CNTs tend to bundle together tightly by themselves in the film structure, resulting in an enhanced packing density; meanwhile, they also provide a high degree of CNT alignment, which prominently contributes to high mechanical properties of the CNT films. When CNTs are long, they tend to be bent and entangled, which significantly reduce their packing density, impairing the film mechanical behaviors severely. It has also been unveiled that the determinant effect of the CNT alignment on the film mechanical properties is more significant than that of the film packing density. These findings provide guidance on the optimal CNT length when attempting to fabricate high-performance macroscopic CNT assemblies.}, number={26}, journal={NANOTECHNOLOGY}, author={Zhang, Liwen and Ma, Xiaolong and Zhang, Yongyi and Bradford, Philip D. and Zhu, Yuntian T.}, year={2021}, month={Jun} }
 @article{aly_lubna_bradford_2021, title={Low density, three-dimensionally interconnected carbon nanotube/silicon carbide nanocomposites for thermal protection applications}, volume={41}, ISSN={["1873-619X"]}, DOI={10.1016/j.jeurceramsoc.2020.06.020}, abstractNote={Synthesis of silicon carbide (SiC) nanostructures and their composites has been a topic of interest for the scientific community due to the unique properties that can be obtained with nanoscale features. Herein, we report the scalable fabrication of anisotropic and low density, carbon nanotube/SiC (CNT/SiC) core-shell structures synthesized via chemical vapor infiltration (CVI) of silicon on aligned CNT foams followed by heat treatment at 1350 °C. Structures made of CNT/SiC nanotube networks with a thickness of 1 cm and length of 9 cm were prepared in the present work. Upon the removal of the CNT foam via calcination of the hybrid nanocomposite in air, a free-standing mechanically robust three-dimensional network of pure SiC nanotubes was left behind. The density of the synthesized CNT/SiC is the lowest reported for any C/SiC structure. Furthermore, the CNT/SiC hybrid nano-architecture demonstrated superb heat resistance and stability in ultrahigh temperature environment.}, number={1}, journal={JOURNAL OF THE EUROPEAN CERAMIC SOCIETY}, author={Aly, Karim and Lubna, Mostakima and Bradford, Philip D.}, year={2021}, month={Jan}, pages={233–243} }
 @article{aly_aboubakr_bradford_2021, title={One-step fabrication of bulk nanocomposites reinforced by carbon nanotube array fragments}, volume={10}, ISSN={["1548-0569"]}, url={https://doi.org/10.1002/pc.26359}, DOI={10.1002/pc.26359}, abstractNote={Abstract Vertically aligned carbon nanotube (VACNT) array growth is an established process where high aspect ratio carbon nanotubes (CNTs) are produced. This work demonstrates one‐step approach to fabricate bulk polymer nanocomposites using CNT array fragments'. Here, 4.5 mm long CNTs were collected post VACNTs synthesis. Next, CNT array fragments were coated with pyrolytic carbon (PyC) and infused with polydimethylsiloxane (PDMS) matrix to create porous CNT/PDMS nanocomposite with a CNT weight fraction of 20%. Achieving similar weight fraction with super long bundled CNTs using dispersion techniques is extremely difficult. The compression and dynamic mechanical behaviors and piezoresistive response of the PDMS filled nanocomposite were assessed. The results revealed the potential of the synthesized structure to serve as fatigue‐resistant pressure sensors with high damping and self‐sensing capabilities. The proposed fabrication technique is versatile, as it can work with thermosetting and thermoplastic polymers in addition to allowing for mass production of PDMS filled nanocomposites.}, journal={POLYMER COMPOSITES}, publisher={Wiley}, author={Aly, Karim and Aboubakr, Sherif H. and Bradford, Philip D.}, year={2021}, month={Oct} }
 @article{spencer_yildiz_kamboj_bradford_augustyn_2021, title={Toward Deterministic 3D Energy Storage Electrode Architectures via Electrodeposition of Molybdenum Oxide onto CNT Foams}, volume={35}, ISSN={["1520-5029"]}, DOI={10.1021/acs.energyfuels.1c02352}, abstractNote={Three-dimensional (3D) deterministic design of electrodes could enable simultaneous high energy and power density for electrochemical energy storage devices. The goal of such electrode architectures is to provide adequate charge (electron and ion) transport pathways for high power, while maintaining high active material loading (>10 mg cm–2) for high areal and volumetric capacities. However, it remains a challenge to fabricate such electrodes with processes that are both scalable and reproducible. Toward this end, here, we demonstrate how the fabrication of such an electrode is made possible by combining tunable, free-standing, and aligned carbon nanotube (CNT) foams with aqueous electrodeposition of a model intercalation-type transition metal oxide, MoO3. Morphological characterization including X-ray microcomputed tomography indicates that the obtained composite is homogeneous. Electrodes with an active mass loading of up to 18 mg cm–2 reached near-theoretical Li-ion intercalation capacities within 1.7 h. The highest-mass loading electrodes also led to areal and volumetric capacities of 4.5 mA h cm–2 and 290 mA h cm–3, respectively, with 55% capacity retention for charge/discharge times of 10 min. Overall, this work demonstrates a scalable, deterministic 3D electrode design strategy using electrodeposition and free-standing, aligned CNT foams that lead to high areal and volumetric capacities and good rate performance due to well-distributed charge transport pathways.}, number={19}, journal={ENERGY & FUELS}, author={Spencer, Michael A. and Yildiz, Ozkan and Kamboj, Ishita and Bradford, Philip D. and Augustyn, Veronica}, year={2021}, month={Oct}, pages={16183–16193} }
 @article{vallabh_li_bradford_kim_seyam_2021, title={Ultra-lightweight fiber-reinforced envelope material for high-altitude airship}, volume={6}, ISSN={["1754-2340"]}, DOI={10.1080/00405000.2021.1948695}, abstractNote={Abstract In this work, fiber-reinforced laminates for the envelope (hull) of high-altitude airships were developed using a novel design concept utilizing ethylene vinyl alcohol (EVOH) as the adhesive component layer with high gas barrier properties. The other component layers of the laminates included poly(p-phenylene benzobisoxazole) (Zylon®) fabric, metalized Mylar® (polyester) and metallized Kapton® (polyimide). The envelope materials were developed in two different strength categories. In the first category, three laminate designs were developed with strength ranging from 945–970 N/cm. The second group had one laminate design with a strength of 702 N/cm. These laminates with basis weights ranging from 103–113 g/m2, are the lightest envelope materials developed to date. As a function of their high strength and low basis weights, the new envelope materials have significantly higher specific strength (ranging from 911–925 kN.m/kg) compared to other envelope constructions published in the open literature. Other outstanding properties of the laminates include low helium permeability ranging from 0.4–8.0 cc/m2.24 hr.1 atm, high tear strength, UV and visible light (UV–Vis) resistance, and high creep resistance.}, journal={JOURNAL OF THE TEXTILE INSTITUTE}, author={Vallabh, Rahul and Li, Ang and Bradford, Philip D. and Kim, David and Seyam, Abdel-Fattah M.}, year={2021}, month={Jun} }
 @article{kim_ramalingam_balakumar_zhang_gao_son_bradford_2020, title={Chemically interconnected ternary AgNP/polypyrrole/functionalized buckypaper composites as high-energy-density supercapacitor electrodes}, volume={739}, ISSN={["1873-4448"]}, DOI={10.1016/j.cplett.2019.136957}, abstractNote={In this study, a chemically interconnected composite, called EBP-PPY-AgNP, was fabricated to develop high-performance hybrid supercapacitor electrodes. The composite consists of epoxide-functionalized buckypaer (EBP), polypyrrole (PPY), and silver nanoparticles (AgNP). The structure was characterized using Raman spectroscopy, X-ray photon spectroscopy (XPS), and scanning electron microscopy (SEM). Also, cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) analyses were conducted to estimate the electrochemical performance. The results were more excellent than those of the other electrodes not chemically interconnected. Finally, the energy density was calculated, and the value was higher than in previous studies that examined electrodes with similar materials.}, journal={CHEMICAL PHYSICS LETTERS}, author={Kim, Hyungjoo and Ramalingam, Manivannan and Balakumar, Vellaichamy and Zhang, Xiangwu and Gao, Wei and Son, Young-A and Bradford, Philip D.}, year={2020}, month={Jan} }
 @article{wang_yildiz_li_aly_qiu_jiang_pui_chen_bradford_2020, title={High temperature carbon nanotube - Nanofiber hybrid filters}, volume={236}, ISSN={["1873-3794"]}, DOI={10.1016/j.seppur.2019.116255}, abstractNote={Novel hybrid filters composed of aligned carbon nanotube (CNT) sheets, sandwiched between electrospun polyimide (PI) nanofiber membranes serving as the supporting layers, were fabricated for the capture of fine particles. The CNT sheets and PI nanofiber membranes were thermally bonded together by melting electrospun polyetherimide (PEI) nanofibers. Two different kinds of filter structures were prepared, where multiple layers of aligned CNT sheets were either stacked together on top of each other or separated from each other by a PEI layer. The filtration performance tests showed that the filtration efficiency increased with increasing number of CNT sheets. The maximum filtration efficiency reached 99.99% at 5.3 cm/s face velocity for 0.3 μm particles by the 4-layer CNT filter, while the pressure drop was only 120 Pa. In mechanical testing, the CNT sheets also reinforced the hybrid filters, even though the PI nanofiber membrane already had relatively high mechanical properties. The tensile strength of the 4-layer CNT hybrid filters was 9 MPa, reaching the highest tier of strength reported for nanofiber membranes. In addition to high efficiency and low pressure drop, the hybrid all-nanofiber filters are also targeted for use in hot gas filtration applications where temperatures reach 200–250 °C.}, journal={SEPARATION AND PURIFICATION TECHNOLOGY}, author={Wang, Qiannan and Yildiz, Ozkan and Li, Ang and Aly, Karim and Qiu, Yiping and Jiang, Qiuran and Pui, David Y. H. and Chen, Sheng-Chieh and Bradford, Philip D.}, year={2020}, month={Apr} }
 @article{li_yildiz_mills_flewwellin_bradford_jur_2020, title={Iron-on carbon nanotube (CNT) thin films for biosensing E-Textile applications}, volume={168}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2020.06.057}, abstractNote={Conductive carbon nanotube-thermoplastic polyurethane (CNT-TPU) composite thin films are patterned and integrated onto knitted textile substrates to form electronic textile (E-Textile) dry electrodes. Vertically aligned CNT arrays are mechanically drawn into thin CNT sheets and infiltrated with a TPU solution to form the CNT-TPU thin films. The CNT-TPU thin films are then heat laminated onto knitted textile substrates to form dry E-Textile electrodes. To understand the wearability of our CNT-TPU thin films we perform an in-depth analysis of the films’ electromechanical properties, electrical impedance, and electrocardiogram (ECG) sensing performance. The electromechanical coupling between the CNT thin films and knitted textile substrates show a strong anisotropic dependence between the CNT film alignment and textile knit structure. Further analysis into the CNT thin films reveal that larger electrode sizes with a larger number of CNT sheet layers in the film, lead to more favorable impedance behaviors and ECG sensing capabilities. As a wearable demonstration, we fabricate a textile arm sleeve integrated with CNT thin film electrodes to form an ECG sensing E-Textile system. The proposed E-Textile sleeve demonstrates the practicality of our CNT thin films and show promise for other E-Textile and wearable applications.}, journal={CARBON}, author={Li, Braden M. and Yildiz, Ozkan and Mills, Amanda C. and Flewwellin, Tashana J. and Bradford, Philip D. and Jur, Jesse S.}, year={2020}, month={Oct}, pages={673–683} }
 @article{aksu_bradford_jur_2020, title={Microfluidic Behavior of Alumina Nanotube-Based Pathways within Hydrophobic CNT Barriers}, volume={36}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.0c01096}, abstractNote={The use of porous micro-and nanostructured materials within microfluidic devices provides opportunities for unique fluid transport characteristics. In this paper we investigate the microfluidic behavior of hybrid alumina nanotube-based pathways within hydrophobic carbon nanotube (CNT) barriers. These hybrid systems provide unique benefits toward the potential liquid transport control in porous structures with real-time sensing of those fluids. Specifically, we examine how the alignment of the alumina nanostructures with high internal porosity enables increasing capillary action and the sensitivity of detection. Based on the Lucas and Washburn model (LW) and modified LW models, the microfluidic behavior of these systems is detailed. The predictions from the models for the time exponent for capillary transport in porous media is shown to be ≤ 0.5. The experimental results demonstrate that the average capillary rise in nanostructured media driven by capillary force follows t0.7. The hydrophilic/electrically insulating and hydrophobic/electrically conductive patterned structures of the device are applied toward electronic measurement within the microfluidic channels. The device structure enables detection of fluid samples of very low analyte concentrations (1 µM) that can be achieved due to the very high surface area of the hybrid structure combined with the electrical conductivity of CNT support structure.}, number={30}, journal={LANGMUIR}, author={Aksu, Cemile and Bradford, Philip D. and Jur, Jesse S.}, year={2020}, month={Aug}, pages={8792–8799} }
 @article{wee_hackney_wells_bradford_peters_2020, title={Ultrasonic Lamb wave measurement sensitivity of aligned carbon nanotube coated fiber Bragg grating}, volume={2}, ISSN={["2515-7647"]}, DOI={10.1088/2515-7647/ab525e}, abstractNote={Fiber Bragg grating (FBG) sensors are typically bonded on the surface of a structure using an adhesive to collect ultrasonic waves for damage detection in structural health monitoring applications. However, the ultrasonic wave transfer from structure to optical fiber suffers signal attenuation due to the adhesive bond layer, which has a significantly different acoustic impedance than the optical fiber. Therefore, this paper develops a systematic procedure to fabricate an aligned carbon nanotube (CNT)-wrapped FBGs for acoustic impedance matching. Specifically, we first develop an automated CNT winding system to fabricate CNT-wrapped FBGs with varying CNT layer thickness, which are bonded to an aluminum plate for ultrasonic sensitivity testing. We demonstrate that CNT wrapped FBGs do not necessarily produce an increased sensitivity as compared to a reference polyimide-coated FBG, however some outliers are observed with a significant improvement. Using a scanning electron microscopy we examine the cross-section of CNT/adhesive layers, identifying a unique CNT/adhesive bonding morphology with a stiff exterior shell and a relatively compliant inner layer. Finite element simulation validates that this two-layered bonding geometry is most likely the source of the increased FBG ultrasonic sensitivity for the outliers.}, number={1}, journal={JOURNAL OF PHYSICS-PHOTONICS}, author={Wee, Junghyun and Hackney, Drew and Wells, Brian and Bradford, Philip D. and Peters, Kara}, year={2020}, month={Jan} }
 @article{kim_ramalingam_balakumar_zhang_gao_son_bradford_2019, title={AgNP/crystalline PANI/EBP-composite-based supercapacitor electrode with internal chemical interactions}, volume={136}, ISSN={["1097-4628"]}, url={https://publons.com/publon/26924632/}, DOI={10.1002/app.48164}, abstractNote={ABSTRACT}, number={44}, journal={JOURNAL OF APPLIED POLYMER SCIENCE}, author={Kim, Hyungjoo and Ramalingam, Manivannan and Balakumar, Vellaichamy and Zhang, Xiangwu and Gao, Wei and Son, Young-A and Bradford, Philip D.}, year={2019}, month={Nov} }
 @article{yildiz_dirican_fang_fu_jia_stano_zhang_bradford_2019, title={Hybrid Carbon Nanotube Fabrics with Sacrificial Nanofibers for Flexible High Performance Lithium-Ion Battery Anodes}, volume={166}, ISSN={["1945-7111"]}, url={https://publons.com/publon/26924627/}, DOI={10.1149/2.0821902jes}, abstractNote={Silicon is one of the most promising anode materials for lithium-ion batteries because of its highest known theoretical charge capacity (4,200 mAh g−1). However, it has found limited application in commercial batteries because of the significant volume change (up to 400%) of silicon during cycling, which results in pulverization and capacity fading. Here, we present a new method to develop a silicon - carbon nanotube (CNT) hybrid anode architecture using CNT-polymer nanofiber hybridization method. The anode material is produced by electrospinning PMMA-Si nanofibers onto aligned CNT sheets, which are drawn on a grounded, rotating take-up roller, and then subsequently decomposing the PMMA electrospun fibers at elevated temperature to create a uniform distribution of Si particles within the CNT sheets. The whole structure is then coated with pyrolytic carbon via chemical vapor deposition (CVD). The architecture provides sufficient space to accommodate the volume expansion of the Si nanoparticles. The CVD pyrolytic carbon coating helps to anchor the Si nanoparticles within CNT sheets and stabilize solid-electrolyte-interface (SEI) formation. The novel freestanding, binder free CNT-Si-C sheet hybrid exhibited improved performance in terms of excellent cycling capacity (1470 mAh g−1), high coulombic efficiency (98%), and good capacity retention of 88% after 150 cycles.}, number={4}, journal={JOURNAL OF THE ELECTROCHEMICAL SOCIETY}, author={Yildiz, Ozkan and Dirican, Mahmut and Fang, Xiaomeng and Fu, Kun and Jia, Hao and Stano, Kelly and Zhang, Xiangwu and Bradford, Philip D.}, year={2019}, month={Feb}, pages={A473–A479} }
 @article{aly_bradford_2019, title={Real-time impact damage sensing and localization in composites through embedded aligned carbon nanotube sheets}, volume={162}, ISSN={["1879-1069"]}, url={https://doi.org/10.1016/j.compositesb.2018.12.104}, DOI={10.1016/j.compositesb.2018.12.104}, abstractNote={Carbon nanotubes (CNTs) have shown potential as a good candidate for performing strain and damage sensing in composites, however, the number of studies that have examined CNTs piezoresistive response under impact is limited. This paper investigates a novel technique for real-time damage sensing during and after impact strikes on composite laminates. In this technique, aligned CNT sheets layers are distributed through the thickness to monitor the developing damage in the host structure's impact side, mid-plane and non-impact side. This is accomplished through measuring the CNT sheets' in-plane electrical resistance changes simultaneously and linking them to the impact damage modes in the structure. The experimental results demonstrate the CNT layers' ability to detect, locate and quantify impact damage when the host structure undergoes different types of impacts. The results highlight the CNT sensing layers high sensitivity to damage accumulation.}, journal={COMPOSITES PART B-ENGINEERING}, publisher={Elsevier BV}, author={Aly, Karim and Bradford, Philip D.}, year={2019}, month={Apr}, pages={522–531} }
 @article{ho_yildiz_bradford_zhu_fedkiw_2018, title={A silicon-impregnated carbon nanotube mat as a lithium-ion cell anode}, volume={48}, ISSN={["1572-8838"]}, DOI={10.1007/s10800-017-1140-8}, abstractNote={Silicon is a widely researched material for the anodes of lithium-ion batteries due to its high practical charge capacity of 3600 mAh g−1, which is ~ 10 times the specific capacity of conventional graphitic materials. However, silicon degrades rapidly in use due to its volumetric changes during charge/discharge of the battery, which makes it necessary to use complicated or costly methods to ameliorate capacity loss. Here, we report a novel silicon anode fabrication technique, which involves winding an aligned carbon nanotube (CNT) sheet and commensurately infiltrating it in situ with an aqueous solution containing silicon nanoparticles and hydroxypropyl guar binder. The resulting infiltrated felts were processed, evaluated, and compared to conventional silicon–carbon black anodes with the same carbon, silicon, and binder content as a proof of concept study. The felts had a large initial reversible capacity and promising rate capability. It is likely that the conductive CNT structure improved the charge transfer properties while lessening the effects of silicon volumetric expansion during lithiation. The results demonstrate that this novel anode fabrication method is viable and may be explored for further optimization. A novel fabrication method is described for the negative electrode for a lithium-ion battery: a CNT mat is formed by a drawing operation from a CNT vertical array while simultaneously being impregnated with a solution containing silicon nanoparticles and hydroxypropyl guar gum binder. The resulting CNT–Si anode structure shows improved lifetime cycling performance compared to traditional slurry-based silicon anodes.}, number={1}, journal={JOURNAL OF APPLIED ELECTROCHEMISTRY}, author={Ho, David N. and Yildiz, Ozkan and Bradford, Philip and Zhu, Yuntian and Fedkiw, Peter S.}, year={2018}, month={Jan}, pages={127–133} }
 @article{wee_hackney_bradford_peters_2018, title={Effect of continuous optical fiber bonding on ultrasonic detection using fiber Bragg grating}, volume={10598}, ISSN={["1996-756X"]}, DOI={10.1117/12.2295833}, abstractNote={For laboratory demonstrations, Lamb wave detection using fiber Bragg grating (FBG) sensors is typically performed with only the grating location spot bonded and with the fiber axis aligned with the ultrasonic propagation direction. However, in reality, the entire length of fiber is often bonded to protect the fiber from any environmental damage, referred to here as continuous bonding. Theoretically, the Lamb wave signal can couple to the guided traveling wave in the optical fiber at any adhered location, which could potentially produce output signal distortion. In this paper, we investigate the impact of continuously bonding a long length of optical fiber on the measured Lamb wave signal detected by an FBG. Therefore, an experiment is performed to measure the Lamb wave signals excited from a PZT actuator using a surface bonded FBG with varying optical fiber bond length, indicating that the output FBG response remains constant with changing length. The second experiment investigates the FBG angular response to the traveling wave in the optical fiber, and compares to the conventional case where FBG directly measures the Lamb waves with varying angle. Specifically, the optical fiber is bonded to the plate at a distance away from the FBG. The Lamb wave is launched to the bond location with varying angles, which is coupled to traveling wave, then measured with FBG. The results indicate that the mechanism of the Lamb wave transfer to the directly bonded FBG is through displacement matching, whereas that of the traveling wave is through a forced excitation.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2018}, author={Wee, Junghyun and Hackney, Drew and Bradford, Philip and Peters, Kara}, year={2018} }
 @article{wee_hackney_bradford_peters_2018, title={Experimental Study on Directionality of Ultrasonic Wave Coupling Using Surface-Bonded Fiber Bragg Grating Sensors}, volume={36}, ISSN={["1558-2213"]}, DOI={10.1109/jlt.2017.2769960}, abstractNote={Recent studies demonstrated the potential of increasing the Lamb wave detection sensitivity of fiber Bragg grating (FBG) sensors by bonding the optical fiber away from the grating location, instead of the conventional method of bonding the FBG directly. The FBG located at a remote location further along the optical fiber collects the guided traveling wave in the optical fiber generated from the Lamb wave signal. This remote bonding method could potentially be extended to a series of multiplexed FBGs. However, previous experiments also detected coupling to guided traveling waves in both directions in the optical fiber, which could have significant effects on multiplexed signals. In this paper, we measure the coupled signal amplitudes in both forward and backward directions, when ultrasonic waves couple from a thin plate to an optical fiber and from an optical fiber to a thin plate. The forward- and backward-induced modes are measured in both the optical fiber and the plate. The same experiment is then performed for the case when ultrasonic signal is coupled from the optical fiber to the plate. In addition, two different types of bonding, cyanoacrylate adhesive and frictional bond, are explored to investigate how the signal conversion depends on the bonding method. The results demonstrate that the coupling of ultrasonic waves from a thin structure to an optical fiber and from an optical fiber to the structure is complex. The coupling does not only occur in the direction of the wave propagation, but can be coupled into both forward and backward modes, depending on the bonding configuration used.}, number={4}, journal={JOURNAL OF LIGHTWAVE TECHNOLOGY}, author={Wee, Junghyun and Hackney, Drew and Bradford, Philip and Peters, Kara}, year={2018}, month={Feb}, pages={932–938} }
 @article{aksu_ingram_bradford_jur_2018, title={Laser-etch patterning of metal oxide coated carbon nanotube 3D architectures}, volume={29}, ISSN={["1361-6528"]}, DOI={10.1088/1361-6528/aac79d}, abstractNote={This paper describes a way to fabricate novel hybrid low density nanostructures containing both carbon nanotubes (CNTs) and ceramic nanotubes. Using atomic layer deposition, a thin film of aluminum oxide was conformally deposited on aligned multiwall CNT foams in which the CNTs make porous, three-dimensional interconnected networks. A CO2 laser was used to etch pure alumina nanotube structures by burning out the underlying CNT substrate in discrete locations via the printed laser pattern. Structural and morphological transitions during the calcination process of aluminum oxide coated CNTs were investigated through in situ transmission electron microscopy and high-resolution scanning electron microscopy. Laser parameters were optimized to etch the CNT away (i.e. etching speed, power and focal length) while minimizing damage to the alumina nanotubes due to overheating. This study opens a new route for fabricating very low density three dimensionally patterned materials with areas of dissimilar materials and properties. To demonstrate the attributes of these structures, the etched areas were used toward anisotropic microfluidic liquid flow. The demonstration used the full thickness of the material to make complex pathways for the liquid flow in the structure. Through tuning of processing conditions, the alumina nanotube (etched) regions became hydrophilic while the bulk material remained hydrophobic and electrically conductive.}, number={33}, journal={NANOTECHNOLOGY}, author={Aksu, Cemile and Ingram, Wade and Bradford, Philip D. and Jur, Jesse S.}, year={2018}, month={Aug} }
 @article{faraji_stano_akyildiz_yildiz_jur_bradford_2018, title={Modifying the morphology and properties of aligned CNT foams through secondary CNT growth}, volume={29}, ISSN={["1361-6528"]}, DOI={10.1088/1361-6528/aac03c}, abstractNote={In this work, we report for the first time, growth of secondary carbon nanotubes (CNTs) throughout a three-dimensional assembly of CNTs. The assembly of nanotubes was in the form of aligned CNT/carbon (ACNT/C) foams. These low-density CNT foams were conformally coated with an alumina buffer layer using atomic layer deposition. Chemical vapor deposition was further used to grow new CNTs. The CNT foam’s extremely high porosity allowed for growth of secondary CNTs inside the bulk of the foams. Due to the heavy growth of new nanotubes, density of the foams increased more than 2.5 times. Secondary nanotubes had the same graphitic quality as the primary CNTs. Microscopy and chemical analysis revealed that the thickness of the buffer layer affected the diameter, nucleation density as well as growth uniformity across the thickness of the foams. The effects of secondary nanotubes on the compressive mechanical properties of the foams was also investigated.}, number={29}, journal={NANOTECHNOLOGY}, author={Faraji, Shaghayegh and Stano, Kelly and Akyildiz, Halil and Yildiz, Ozkan and Jur, Jesse S. and Bradford, Philip D.}, year={2018}, month={Jul} }
 @article{wee_hackney_bradford_peters_2017, title={Bi-directional ultrasonic wave coupling to FBGs in continuously bonded optical fiber sensing}, volume={56}, ISSN={["2155-3165"]}, DOI={10.1364/ao.56.007262}, abstractNote={Fiber Bragg grating (FBG) sensors are typically spot-bonded onto the surface of a structure to detect ultrasonic waves in laboratory demonstrations. However, to protect the rest of the optical fiber from any environmental damage during real applications, bonding the entire length of fiber, called continuous bonding, is commonly done. In this paper, we investigate the impact of continuously bonding FBGs on the measured Lamb wave signal. In theory, the ultrasonic wave signal can bi-directionally transfer between the optical fiber and the plate at any adhered location, which could potentially produce output signal distortion for the continuous bonding case. Therefore, an experiment is performed to investigate the plate-to-fiber and fiber-to-plate signal transfer, from which the signal coupling coefficient of each case is theoretically estimated based on the experimental data. We demonstrate that the two coupling coefficients are comparable, with the plate-to-fiber case approximately 19% larger than the fiber-to-plate case. Finally, the signal waveform and arrival time of the output FBG responses are compared between the continuous and spot bonding cases. The results indicate that the resulting Lamb wave signal output is only that directly detected at the FBG location; however, a slight difference in signal waveform is observed between the two bonding configurations. This paper demonstrates the practicality of using continuously bonded FBGs for ultrasonic wave detection in structural health monitoring (SHM) applications.}, number={25}, journal={APPLIED OPTICS}, author={Wee, Junghyun and Hackney, Drew and Bradford, Philip and Peters, Kara}, year={2017}, month={Sep}, pages={7262–7268} }
 @article{aly_li_bradford_2017, title={Compressive piezoresistive behavior of carbon nanotube sheets embedded in woven glass fiber reinforced composites}, volume={116}, ISSN={["1879-1069"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85006298233&partnerID=MN8TOARS}, DOI={10.1016/j.compositesb.2016.11.002}, abstractNote={Due to the difficulties associated with performing compression tests and the complex nature of compression failure, the number of studies that have examined the piezoresistive response of carbon nanotube (CNT) sensing networks in composites under compression loading has been limited. This paper introduces a novel technique for embedding aligned sheets of two millimeter long, interconnected CNTs into the interlaminar region of laminated composite structures to assess the potential of the CNT sheets to function as strain sensing materials for composite structures subjected to axial compression loading. Quasi-static and cyclic compression mechanical loading tests were accompanied by real time electrical resistance change data acquisition and the results suggested that the CNT sheet sensing material composed of six CNT sheets layers exhibited improved sensitivity, stability and repeatability which are vital properties for any successful health monitoring technique. The coupons with six CNT sheets layers embedded exhibited piezoresistivity that showed some linearity in tension and was nonlinear in compression. This piezoresistive response was characterized as anti-symmetric around zero strain all the way until fracture.}, journal={COMPOSITES PART B-ENGINEERING}, author={Aly, Karim and Li, Ang and Bradford, Philip D.}, year={2017}, month={May}, pages={459–470} }
 @article{he_yoo_meng_yildiz_bradford_park_gao_2017, title={Engineering biorefinery residues from loblolly pine for supercapacitor applications}, volume={120}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2017.05.056}, abstractNote={Recycling agricultural waste biomass into high-value-added products is of great importance to offset the cost of biofuel production. Here, we make biochar-based activated carbons (BACs) from loblolly pine chips via different carbonization recipes and chemical activations. BACs were then assembled into electrochemical double-layer capacitors (EDLCs) as electrode materials. Surprisingly, pyrolysis at lower temperatures (300 °C and 350 °C) rendered better electrochemical performance of BACs than those done at higher temperatures (500 °C and 700 °C). This is mainly due to the large surface area and high pore volume generated at the lower temperatures. Among all the pyrolysis recipes, flash pyrolysis at 300 °C produced the BAC with the highest specific capacitance (74 F g−1 at 20 mV s−1), exceeding the specific capacitance of commercial activated carbon (NORIT®) by 45%. This report demonstrates the great potential of our refinery recipe to engineer BACs from the sustainable, affordable, and abundant natural wastes for energy-storage applications, which opens the door for a group of biorefinery residues for value-added applications.}, journal={CARBON}, author={He, Nanfei and Yoo, Seunghyun and Meng, Jiajia and Yildiz, Ozkan and Bradford, Philip D. and Park, Sunkyu and Gao, Wei}, year={2017}, month={Aug}, pages={304–312} }
 @article{fang_li_yildiz_shao_bradford_ghosh_2017, title={Enhanced anisotropic response of dielectric elastomer actuators with microcombed and etched carbon nanotube sheet electrodes}, volume={120}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2017.05.067}, abstractNote={Dielectric elastomers (DE), also known as dielectric electroactive polymers offer tremendous potential in a wide-ranging applications including microrobotics and wearable responsive systems. The real-world application of DEs, however, has been limited by a number of factors, including facile means of producing directional stress/strain. As a critical component of the DE actuator, the electrodes should have high electrical conductance under finite in-plane deformation, good electromechanical stability, and ease of shaping based on the design requirements. In this work we investigate highly aligned carbon nanotube (CNT) sheets as electrodes in DE actuators to yield anisotropic electromechanical response. The morphology of CNT sheets were altered by microcombing and selective laser etching to enhance mechanical anisotropy. The enhancement of CNT sheets alignment results in almost pure unidirectional strain of 33% at a relatively moderate electric field. The results demonstrate that the deformation anisotropy of DE actuators can be significantly improved by directional laser etching of the electrodes rather than microcombing alone.}, journal={CARBON}, author={Fang, Xiaomeng and Li, Ang and Yildiz, Ozkan and Shao, Huiqi and Bradford, Philip D. and Ghosh, Tushar K.}, year={2017}, month={Aug}, pages={366–373} }
 @article{wells_kumar_reynolds_peters_bradford_2017, title={Highly anisotropic magneto-transport and field orientation dependent oscillations in aligned carbon nanotube/epoxy composites}, volume={111}, ISSN={["1077-3118"]}, DOI={10.1063/1.4999503}, abstractNote={Carbon nanotubes (CNTs) have been widely investigated as additive materials for composites with potential applications in electronic devices due to their extremely large electrical conductivity and current density. Here, highly aligned CNT composite films were created using a sequential layering fabrication technique. The degree of CNT alignment leads to anisotropic resistance values which varies >400× in orthogonal directions. Similarly, the magnetoresistance (MR) of the CNT composite differs depending upon the relative direction of current and the applied magnetic field. A suppression of negative to positive MR crossover was also observed. More importantly, an overall positive magnetoresistance behavior with localized +/− oscillations was discovered at low fields which persists up to room temperature when the current (I) and in-plane magnetic field (B) were parallel to the axis of CNT (B∥I∥CNT), which is consistent with Aharonov-Bohm oscillations in our CNT/epoxy composites. When the current, applied magnetic field, and nanotube axis are aligned, the in-plane MR is positive instead of negative as observed for all other field, current, and tube orientations. Here, we provide in-depth analysis of the conduction mechanism and anisotropy in the magneto-transport properties of these aligned CNT-epoxy composites.}, number={26}, journal={APPLIED PHYSICS LETTERS}, author={Wells, Brian and Kumar, Raj and Reynolds, C. Lewis, Jr. and Peters, Kara and Bradford, Philip D.}, year={2017}, month={Dec} }
 @article{yu_zhang_yildiz_deng_zhao_bradford_li_zhu_2017, title={Investigation of microcombing parameters in enhancing the properties of carbon nanotube yarns}, volume={134}, ISSN={["1873-4197"]}, DOI={10.1016/j.matdes.2017.08.035}, abstractNote={Microcombing has been reported as a novel processing approach for reducing waviness and improving alignment of carbon nanotubes (CNTs), which effectively enhances the performance of materials made from CNT sheets. In this study, we have systematically investigated the effects of microcombing parameters on the properties of CNT yarns. It is found that the electrical and mechanical properties of CNT yarns first improved with increasing degree of microcombing and then degraded with over-combing. At the optimum degree of microcombing, the electrical conductivity, tensile strength, and Young's modulus of the CNT yarns were improved to 140%, 140%, and 230%, respectively, over those of uncombed yarns. The enhanced yarn properties were resulted from reduced nanotube waviness, improved CNT alignment and denser packing structure, which led to a more uniform yarn structure. On the other hand, over-combing degraded structural uniformity, resulting in lower electrical and mechanical properties. These observations are expected to help with future selection of microcombing parameters for producing high-quality CNT yarns and polymer-CNT composite yarns for superior electrical and mechanical properties.}, journal={MATERIALS & DESIGN}, author={Yu, Yingying and Zhang, Liwen and Yildiz, Ozkan and Deng, Haotian and Zhao, Changhao and Bradford, Philip D. and Li, Jianying and Zhu, Yuntian}, year={2017}, month={Nov}, pages={181–187} }
 @article{gigax_bradford_shao_2017, title={Ion Beam Modification of Carbon Nanotube Yarn in Air and Vacuum}, volume={10}, ISSN={["1996-1944"]}, DOI={10.3390/ma10080860}, abstractNote={We studied the effects ion beam irradiation on carbon nanotube (CNT) yarns. CNT yarn was fabricated by drawing and spinning CNT sheets from a vertically aligned CNT forest. The yarn was irradiated by 2.5 MeV protons in either vacuum or air. Irradiation in air was achieved by directing the proton beam through a 0.025 mm thick Ti window. Irradiation in vacuum occurred at a pressure of <10−6 torr at room temperature and at an elevated temperature of 600 °C. Tensile testing revealed that CNT yarn irradiated in air increased in tensile strength with increasing proton fluence. For yarn irradiated in vacuum, however, the strength decreased with increasing fluence. We believe that irradiation-induced excitation and trapping/bonding of gas atoms between tubes may play a role for the mechanical property changes.}, number={8}, journal={MATERIALS}, author={Gigax, Jonathan G. and Bradford, Philip D. and Shao, Lin}, year={2017}, month={Aug} }
 @article{wee_hackney_bradford_peters_2017, title={Mechanisms of signal coupling to optical fiber for FBG sensor detection of Lamb waves}, volume={10323}, ISSN={["1996-756X"]}, DOI={10.1117/12.2263278}, abstractNote={One of the major challenges when using fiber Bragg grating sensors (FBGs) to detect Lamb wave or acoustic emission signals in structures is the low sensitivity of these sensors to surface waves propagating in the structure. The authors have previously demonstrated that remote bonding of the optical fiber away from the FBG can increase the measured signal amplitude. In this paper we investigate the potential mechanisms for this increase through finite element simulations and demonstrate that the shear lag effect through the adhesive is the major source of the signal amplitude difference between the direct and remote bonding cases.}, journal={2017 25TH INTERNATIONAL CONFERENCE ON OPTICAL FIBER SENSORS (OFS)}, author={Wee, Junghyun and Hackney, Drew and Bradford, Philip and Peters, Kara}, year={2017} }
 @article{he_yildiz_pan_zhu_zhang_bradford_gao_2017, title={Pyrolytic-carbon coating in carbon nanotube foams for better performance in supercapacitors}, volume={343}, ISSN={["1873-2755"]}, url={https://publons.com/publon/19584407/}, DOI={10.1016/j.jpowsour.2017.01.091}, abstractNote={Nowadays, the wide-spread adoption of supercapacitors has been hindered by their inferior energy density to that of batteries. Here we report the use of our pyrolytic-carbon-coated carbon nanotube foams as lightweight, compressible, porous, and highly conductive current collectors in supercapacitors, which are infiltrated with chemically-reduced graphene oxide and later compressed via mechanical and capillary forces to generate the active electrodes. The pyrolytic carbon coatings, introduced by chemical vapor infiltration, wrap around the CNT junctions and increase the surface roughness. When active materials are infiltrated, the pyrolytic-carbon coatings help prevent the π-stacking, enlarge the accessible surface area, and increase the electrical conductivity of the scaffold. Our best-performing device offers 48% and 57% higher gravimetric energy and power density, 14% and 23% higher volumetric energy and power density, respectively, and two times higher knee frequency, than the device with commercial current collectors, while the “true-performance metrics” are strictly followed in our measurements. We have further clarified the solution resistance, charge transfer resistance/capacitance, double-layer capacitance, and Warburg resistance in our system via comprehensive impedance analysis, which will shed light on the design and optimization of similar systems.}, journal={JOURNAL OF POWER SOURCES}, publisher={Elsevier BV}, author={He, Nanfei and Yildiz, Ozkan and Pan, Qin and Zhu, Jiadeng and Zhang, Xiangwu and Bradford, Philip D. and Gao, Wei}, year={2017}, month={Mar}, pages={492–501} }
 @article{faraji_yildiz_rost_stano_farahbakhsh_zhu_bradford_2017, title={Radial growth of multi-walled carbon nanotubes in aligned sheets through cyclic carbon deposition and graphitization}, volume={111}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2016.10.012}, abstractNote={Carbon coated aligned multi-walled carbon nanotube (AMWCNT/C) sheets were used for studying the controlled radial growth of MWCNTs. Pyrolytic carbon (PyC) was deposited on the surface of nanotubes using multiple cycles of chemical vapor infiltration. Morphological and structural characterization showed that when graphitization was done in one step, after the deposition of multiple cycles of PyC, the presence of a large amount of disordered carbon on the surface of nanotubes led to a poorly graphitized coating structure that did not resembled nanotube walls anymore. Graphitization of the AMWCNT/C sheets after each deposition cycle prevented the development of disordered carbon during the subsequent PyC deposition cycles. Using the cyclic-graphitization method, thick PyC coating layers were successfully graphitized into a crystalline structure that could not be differentiated from the original nanotube walls. TEM observation and X-ray data confirmed radial growth of nanotubes, while spectra collected from Raman spectroscopy revealed that radially grown CNTs had the same quality as graphitized pristine nanotubes. The focus of this study was to compare the effect of cyclic graphitization with a one-step graphitization method to gain insight on the necessary parameters needed to radially grow high quality CNTs.}, journal={CARBON}, author={Faraji, Shaghayegh and Yildiz, Ozkan and Rost, Christina and Stano, Kelly and Farahbakhsh, Nasim and Zhu, Yuntian and Bradford, Philip D.}, year={2017}, month={Jan}, pages={411–418} }
 @article{gigax_bradford_shao_2017, title={Radiation-induced mechanical property changes of CNT yarn}, volume={409}, ISSN={["1872-9584"]}, DOI={10.1016/j.nimb.2017.04.050}, abstractNote={Stimulated by the previous findings that ion beam can induce carbon nanotube (CNT) welding, we studied the irradiation effects on CNT yarns by proton irradiation. A 2.5 MeV proton beam was transmitted through a 25 μm thick Ti window and irradiated CNT yarn in air. The yarn, of about 40 μm in diameter, was fabricated by pulling and spinning CNT bundles from a CNT aligned film. After irradiation to an ion fluence of 5 × 1012, 1 × 1013, 1 × 1014, and 1 × 1015 cm−2, Raman spectroscopy was performed to study defect behavior by comparing intensity changes to the D and G bands at 1350 cm−1 and 1560 cm−1, respectively. The analysis revealed a decreasing defect level up to 1 × 1013 cm−2, followed by an increasing defect level with increasing fluence. The mechanical properties of the yarns are characterized by using a tensile tester with a strain rate of 0.2 mm/min at room temperature. The maximum tensile strength occurred at a fluence of 1 × 1013 cm−2. With increasing proton fluencies, the fracture strain shows gradual enhancement.}, journal={NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS}, author={Gigax, Jonathan G. and Bradford, Philip D. and Shao, Lin}, year={2017}, month={Oct}, pages={268–271} }
 @article{wee_hackney_bradford_peters_2017, title={Simulating increased Lamb wave detection sensitivity of surface bonded fiber Bragg grating}, volume={26}, ISSN={["1361-665X"]}, DOI={10.1088/1361-665x/aa646b}, abstractNote={Fiber Bragg grating (FBG) sensors are excellent transducers for collecting ultrasonic wave signals for structural health monitoring (SHM). Typically, FBG sensors are directly bonded to the surface of a structure to detect signals. Unfortunately, demodulating relevant information from the collected signal demands a high signal-to-noise ratio because the structural ultrasonic waves have low amplitudes. Our previous experimental work demonstrated that the optical fiber could be bonded at a distance away from the FBG location, referred to here as remote bonding. This remote bonding technique increased the output signal amplitude compared to the direct bonding case, however the mechanism causing the increase was not explored. In this work, we simulate the previous experimental work through transient analysis based on the finite element method, and the output FBG response is calculated through the transfer matrix method. The model is first constructed without an adhesive to assume an ideal bonding condition, investigating the difference in excitation signal coherence along the FBG length between the two bonding configurations. A second model is constructed with an adhesive to investigate the effect of the presence of the adhesive around the FBG. The results demonstrate that the amplitude increase is originated not from the excitation signal coherence, but from the shear lag effect which causes immature signal amplitude development in the direct bonding case compared to the remote bonding case. The results also indicate that depending on the adhesive properties the surface-bonded optical fiber manifests varying resonant frequency, therefore resulting in a peak amplitude response when the input excitation frequency is matched. This work provides beneficial reference for selecting adhesive and calibrating sensing system for maximum ultrasonic detection sensitivity using the FBG sensor.}, number={4}, journal={SMART MATERIALS AND STRUCTURES}, author={Wee, J. and Hackney, D. A. and Bradford, P. D. and Peters, K. J.}, year={2017}, month={Apr} }
 @article{stano_faraji_yildiz_akyildiz_bradford_jur_2017, title={Strong and resilient alumina nanotube and CNT/alumina hybrid foams with tuneable elastic properties}, volume={7}, ISSN={["2046-2069"]}, DOI={10.1039/c7ra02452e}, abstractNote={Alumina foams from anisotropic structured carbon nanotube structures are studied for their unique mechanical and thermal performance characteristics.}, number={45}, journal={RSC ADVANCES}, author={Stano, Kelly L. and Faraji, Shaghayegh and Yildiz, Ozkan and Akyildiz, Halil and Bradford, Philip D. and Jur, Jesse S.}, year={2017}, pages={27923–27931} }
 @article{stahl_bogdanovich_bradford_2016, title={Carbon nanotube shear-pressed sheet interleaves for Mode I interlaminar fracture toughness enhancement}, volume={80}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2015.10.014}, abstractNote={Failure of composite laminates is often the result of “secondary” transverse stresses causing delamination. One well known approach to prevent such failure is to incorporate a distinct interleaf material into the interlaminar region in order to increase its fracture toughness and, consequently, its resistance to delamination. In the recent years various carbon nanotube (CNT) interleaves gained much attention. This work presents experimental study of the Mode I progressive fracture of carbon/epoxy composite laminates modified with high volume fraction, aligned, non-functionalized and functionalized CNT interleaves. The interleaves used here are thin solid sheets produced from vertically grown multiwalled CNT arrays by shear pressing method. A dry or resin infused sheet is integrated between prepreg plies prior to the laminate cure. The obtained results show that both dry and pre-infused CNT interleaves significantly, up to two times, increase the critical strain energy release rate of the baseline non-interleaved laminate. Two methods of functionalizing CNTs within the preform are explored: O2/CF4 plasma and H2SO4/KnO4 wet chemical treatments. Both methods maintain the high alignment and aspect ratio of the CNTs. Although, functionalization results in no additional GIC toughening compared to the non-functionalized interleaves, the characteristics of the fracture surfaces are dramatically different.}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Stahl, James J. and Bogdanovich, Alexander E. and Bradford, Philip D.}, year={2016}, month={Jan}, pages={127–137} }
 @article{zhu_yildirim_aly_shen_chen_lu_jiang_kim_tonelli_pasquinelli_et al._2016, title={Hierarchical multi-component nanofiber separators for lithium polysulfide capture in lithium-sulfur batteries: an experimental and molecular modeling study}, volume={4}, ISSN={["2050-7496"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84984804707&partnerID=MN8TOARS}, DOI={10.1039/c6ta04577d}, abstractNote={A multi-functional nanofiber membrane significantly improves the overall performance of Li–S batteries.}, number={35}, journal={JOURNAL OF MATERIALS CHEMISTRY A}, publisher={Royal Society of Chemistry (RSC)}, author={Zhu, Jiadeng and Yildirim, Erol and Aly, Karim and Shen, Jialong and Chen, Chen and Lu, Yao and Jiang, Mengjin and Kim, David and Tonelli, Alan E. and Pasquinelli, Melissa A. and et al.}, year={2016}, pages={13572–13581} }
 @article{wee_wells_hackney_bradford_peters_2016, title={Increasing signal amplitude in fiber Bragg grating detection of Lamb waves using remote bonding}, volume={55}, ISSN={["2155-3165"]}, DOI={10.1364/ao.55.005564}, abstractNote={Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves using FBG sensors requires a high signal-to-noise ratio because the Lamb waves are of low amplitudes. This paper compares the signal transfer amplitudes between two adhesive mounting configurations for an FBG to detect Lamb waves propagating in an aluminum plate: a directly bonded FBG and a remotely bonded FBG. In the directly bonded FBG case, the Lamb waves create in-plane and out-of-plane displacements, which are transferred through the adhesive bond and detected by the FBG sensor. In the remotely bonded FBG case, the Lamb waves are converted into longitudinal and flexural traveling waves in the optical fiber at the adhesive bond, which propagate through the optical fiber and are detected by the FBG sensor. A theoretical prediction of overall signal attenuation also is performed, which is the combination of material attenuation in the plate and optical fiber and attenuation due to wave spreading in the plate. The experimental results demonstrate that remote bonding of the FBG significantly increases the signal amplitude measured by the FBG.}, number={21}, journal={APPLIED OPTICS}, author={Wee, Junghyun and Wells, Brian and Hackney, Drew and Bradford, Philip and Peters, Kara}, year={2016}, month={Jul}, pages={5564–5569} }
 @article{zhang_wang_li_li_bradford_zhu_2016, title={Microcombing enables high-performance carbon nanotube composites}, volume={123}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2015.12.012}, abstractNote={A processing approach, microcombing, has been reported recently to produce dry carbon nanotube (CNT) films with superior mechanical and electrical properties by taking advantage of its efficiency in straightening the wavy CNTs and aligning the strands. Here, we report the fabrication of CNT composite films with aligned CNTs and CNT strands, reduced waviness, high CNT weight fraction, and relatively uniform CNT distribution, using poly(vinyl alcohol) (PVA) as a model matrix. These structural features give the micro-combed CNT/PVA composite films electrical conductivity of 1.84 × 105 S/m, Young's modulus of 119 GPa, tensile strength of 2.9 GPa, and toughness of 52.4 J/cm3, which improve over those of uncombed samples by 300%, 100%, 120%, and 200%, respectively, and are also much higher than those obtained by other processing approaches. Moreover, this method is expected to be applicable to various polymer matrices as long as they can be dissolved in the solution.}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Zhang, Liwen and Wang, Xin and Li, Ru and Li, Qingwen and Bradford, Philip D. and Zhu, Yuntian}, year={2016}, month={Feb}, pages={92–98} }
 @article{qiu_wang_su_tang_zheng_zhu_wang_norris_bradford_zhu_et al._2016, title={Remarkably enhanced thermal transport based on a flexible horizontally-aligned carbon nanotube array film}, volume={6}, ISSN={["2045-2322"]}, DOI={10.1038/srep21014}, abstractNote={Abstract}, journal={SCIENTIFIC REPORTS}, author={Qiu, L. and Wang, X. T. and Su, G. P. and Tang, D. W. and Zheng, X. H. and Zhu, J. and Wang, Z. G. and Norris, P. M. and Bradford, P. D. and Zhu, Y. T. and et al.}, year={2016}, month={Feb} }
 @article{wee_hackney_peters_wells_bradford_2016, title={Sensitivity of contact-free fiber Bragg grating sensors to ultrasonic Lamb waves}, volume={9803}, ISSN={["1996-756X"]}, DOI={10.1117/12.2218924}, abstractNote={Networks of fiber Bragg grating (FBG) sensors can serve as structural health monitoring (SHM) systems for large-scale structures based on the collection of ultrasonic waves. The demodulation of structural Lamb waves requires a high signal-to-noise ratio because Lamb waves have a low amplitude. This paper investigates the signal transfer between Lamb waves propagating in an aluminum plate collected by an optical fiber containing a FBG. The fiber is bonded to the plate at locations away from the FBG. The Lamb waves are converted into longitudinal and flexural traveling waves propagating along the optical fiber, which are then transmitted to the Bragg grating. The signal wave amplitude is measured for different distances between the bond location and the Bragg grating. Bonding the optical fiber away from the FBG location and closer to the signal source produces a significant increase in signal amplitude, here measured to be 5.1 times that of bonding the Bragg grating itself. The arrival time of the different measured wave coupling paths are also calculated theoretically, verifying the source of the measured signals. The effect of the bond length to Lamb wavelength ratio is investigated, showing a peak response as the bond length is reduced compared to the wavelength. This study demonstrates that coupling Lamb waves into guided traveling waves in an optical fiber away from the FBG increases the signal-to-noise ratio of Lamb wave detection, as compared to direct transfer of the Lamb wave to the optical fiber at the location of the FBG.}, journal={SENSORS AND SMART STRUCTURES TECHNOLOGIES FOR CIVIL, MECHANICAL, AND AEROSPACE SYSTEMS 2016}, author={Wee, Junghyun and Hackney, Drew and Peters, Kara and Wells, Brian and Bradford, Philip}, year={2016} }
 @article{aly_li_bradford_2016, title={Strain sensing in composites using aligned carbon nanotube sheets embedded in the interlaminar region}, volume={90}, ISSN={["1878-5840"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84983749060&partnerID=MN8TOARS}, DOI={10.1016/j.compositesa.2016.08.003}, abstractNote={This paper introduces a novel technique for embedding aligned sheets of two millimeters long, interconnected CNTs into the interlaminar region of composite structures. The potential of these embedded CNT sheets to function as damage detecting and strain sensing elements was demonstrated via various mechanical tests that were accompanied by real time electrical resistance change data acquisition. The experimental results suggested that the CNT sheet sensitivity could be further enhanced by an oxygen plasma treatment and also by pre-straining the CNT sheets before embedding them. The samples containing two CNT sheets layers exhibited long term stability, sensitivity and repeatability which are vital features for health monitoring.}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Aly, Karim and Li, Ang and Bradford, Philip D.}, year={2016}, month={Nov}, pages={536–548} }
 @article{stano_faraji_hodges_yildiz_wells_akyildiz_zhao_jur_bradford_2016, title={Ultralight Interconnected Metal Oxide Nanotube Networks}, volume={12}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201503267}, abstractNote={Record-breaking ultralow density aluminum oxide structures are prepared using a novel templating technique. The alumina structures are unique in that they are comprised by highly aligned and interconnected nanotubes yielding anisotropic behavior. Large-scale network structures with complex form-factors can easily be made using this technique. The application of the low density networks as humidity sensing materials as well as thermal insulation is demonstrated.}, number={18}, journal={SMALL}, author={Stano, Kelly L. and Faraji, Shaghayegh and Hodges, Ryan and Yildiz, Ozkan and Wells, Brian and Akyildiz, Halil I. and Zhao, Junjie and Jur, Jesse and Bradford, Philip D.}, year={2016}, month={May}, pages={2432–2438} }
 @article{stano_faraji_hodges_yildiz_wells_akyildiz_zhao_jur_bradford_2016, title={Ultralight Materials: Ultralight Interconnected Metal Oxide Nanotube Networks (Small 18/2016)}, volume={12}, ISSN={1613-6810}, url={http://dx.doi.org/10.1002/SMLL.201670090}, DOI={10.1002/SMLL.201670090}, abstractNote={On page 2432, a novel templating process for the creation of ultralow density metal oxide nanostructures is demonstrated by P. D. Bradford, and co-workers. The alumina structures are unique in that they are comprised of highly aligned and interconnected nanotubes yielding anisotropic behavior. Large-scale network structures with complex form-factors can easily be made using this technique. Application of the low density networks as humidity sensing materials as well as thermal insulation is demonstrated.}, number={18}, journal={Small}, publisher={Wiley}, author={Stano, Kelly L. and Faraji, Shaghayegh and Hodges, Ryan and Yildiz, Ozkan and Wells, Brian and Akyildiz, Halil I. and Zhao, Junjie and Jur, Jesse and Bradford, Philip D.}, year={2016}, month={May}, pages={2387–2387} }
 @article{bhanushali_bradford_2016, title={Woven Glass Fiber Composites with Aligned Carbon Nanotube Sheet Interlayers}, volume={2016}, ISSN={["1687-4129"]}, DOI={10.1155/2016/9705257}, abstractNote={This investigation describes the design, fabrication, and testing of woven glass fiber reinforced epoxy matrix laminates with aligned CNT sheets integrated between plies in order to improve the matrix dominated through thickness properties such as the interlaminar fracture toughness at ply interfaces. Using aligned CNT sheets allows for a concentration of millimeter long CNTs at the most likely point of laminate failure. Mode I and Mode II interlaminar fracture toughness of various CNT modified samples were investigated using double cantilever beam (DCB) and end notched flexure (ENF) experiments, respectively. Short beam strength (SBS) and in-plane tensile properties of the CNT modified samples were also investigated. Moderate improvement was observed in Mode I and Mode II fracture toughness at crack initiation when aligned CNT sheets with a basis weight of 0.354 g/m2were used to modify the ply interface. No compromise in the in-plane mechanical properties of the laminate was observed and very little improvement was observed in the shear related short beam strength of the CNT modified laminates as compared to the control samples. Integration of aligned CNT sheets into the composite laminate imparted in-plane and through thickness electrical properties into the nonconductive glass fiber reinforced epoxy composite laminates.}, journal={JOURNAL OF NANOMATERIALS}, author={Bhanushali, Hardik and Bradford, Philip D.}, year={2016} }
 @article{li_bogdanovich_bradford_2015, title={Aligned carbon nanotube sheet piezoresistive strain sensors}, volume={24}, ISSN={["1361-665X"]}, DOI={10.1088/0964-1726/24/9/095004}, abstractNote={Carbon nanotubes (CNTs) have a unique set of properties that may be useful in the production of next generation structural health monitoring composites. This research introduces a novel CNT based material system for strain and damage sensing applications. An aligned sheet of interconnected CNTs was drawn from a chemical vapor deposition grown CNT array and then bonded to the surface of glass fiber/epoxy composite coupons. Various types of mechanical tests were conducted, accompanied by real-time electrical data acquisition, in order to evaluate the electro-mechanical behavior of the developed sensing material. Specimens were loaded in the longitudinal and transverse CNT sheet orientations to investigate the anisotropy of the piezoresistive effect. The CNT sheets exhibited good sensing stability, linearity, sensitivity and repeatability within a practical strain range; which are crucial sensor features for health monitoring. It was also demonstrated that the CNT orientation in the sheet had a dramatic effect on the sensitivity, thus validating the usefulness of this sensing material for directional strain/damage monitoring. Finally, pre-straining of the CNT sheet sensors was conducted to further enhance the linearity of electro-mechanical response and long-term stability of the sensors during cyclic loading.}, number={9}, journal={SMART MATERIALS AND STRUCTURES}, author={Li, Ang and Bogdanovich, Alexander E. and Bradford, Philip D.}, year={2015}, month={Sep} }
 @article{cakmak_fang_yildiz_bradford_ghosh_2015, title={Carbon nanotube sheet electrodes for anisotropic actuation of dielectric elastomers}, volume={89}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2015.03.011}, abstractNote={The performance of dielectric electroactive polymer (D-EAP) based actuators depends critically on the electrode characteristics. Among the most challenging issues in the application of D-EAPs is the device-level complexity in producing sufficient directional actuation at acceptably low electric fields. In this work, a simple carbon nanotube (CNT) based electrode for D-EAP actuators is demonstrated that vastly improves directional strain response originating from the mechanical anisotropy of the electrode material. In this novel approach, highly aligned carbon nanotube (CNT) sheet electrodes are applied on acrylate adhesive films show high directed linear actuation strain of greater than 40% at a relatively low electric field (100 V μm−1). The fiber-oriented CNT sheet applied around the D-EAP film, exhibits strong interaction between CNT fibers in the electrode and the D-EAP film to produce a robust conductive-nanolayer at the interface, on actuation cycling. The design paradigm provides a great potential for the fabrication of soft linear actuators.}, journal={CARBON}, author={Cakmak, Enes and Fang, Xiaomeng and Yildiz, Ozkan and Bradford, Philip D. and Ghosh, Tushar K.}, year={2015}, month={Aug}, pages={113–120} }
 @article{yildiz_stano_faraji_stone_willis_zhang_jur_bradford_2015, title={High performance carbon nanotube - polymer nanofiber hybrid fabrics}, volume={7}, ISSN={["2040-3372"]}, url={https://publons.com/publon/26924675/}, DOI={10.1039/c5nr02732b}, abstractNote={A novel hybridization process combining carbon nanotube sheet drawing and electrospinning is a versatile way to produce multifunctional, binder free fabrics which contain ultra high aspect ratio carbon nanotubes intermingled with polymer nanofibers.}, number={40}, journal={NANOSCALE}, publisher={Royal Society of Chemistry (RSC)}, author={Yildiz, Ozkan and Stano, Kelly and Faraji, Shaghayegh and Stone, Corinne and Willis, Colin and Zhang, Xiangwu and Jur, Jesse S. and Bradford, Philip D.}, year={2015}, pages={16744–16754} }
 @article{zhang_wang_xu_zhang_li_bradford_zhu_2015, title={Strong and Conductive Dry Carbon Nanotube Films by Microcombing}, volume={11}, ISSN={["1613-6829"]}, DOI={10.1002/smll.201500111}, abstractNote={In order to maximize the carbon nanotube (CNT) buckypaper properties, it is critical to improve their alignment and reduce their waviness. In this paper, a novel approach, microcombing, is reported to fabricate aligned CNT films with a uniform structure. High level of nanotube alignment and straightness was achieved using sharp surgical blades with microsized features at the blade edges to comb single layer of CNT sheet. These microcombs also reduced structural defects within the film and enhanced the nanotube packing density. Following the microcombing approach, the as‐produced CNT films demonstrated a tensile strength of up to 3.2 GPa, Young's modulus of up to 172 GPa, and electrical conductivity of up to 1.8 × 105 S m−1, which are much superior to previously reported CNT films or buckypapers. More importantly, this novel technique requires less rigorous process control and can construct CNT films with reproducible properties.}, number={31}, journal={SMALL}, author={Zhang, Liwen and Wang, Xin and Xu, Weizong and Zhang, Yongyi and Li, Qingwen and Bradford, Philip D. and Zhu, Yuntian}, year={2015}, month={Aug}, pages={3830–3836} }
 @article{faraji_stano_yildiz_li_zhu_bradford_2015, title={Ultralight anisotropic foams from layered aligned carbon nanotube sheets}, volume={7}, ISSN={["2040-3372"]}, DOI={10.1039/c5nr03899e}, abstractNote={A novel nanofabrication method is demonstrated to produce large size, elastically resilient, ultra-low density carbon nanotube foams (3.8 mg cm−3) with anisotropic and tunable properties. Potential applications of this unique material are explored.}, number={40}, journal={NANOSCALE}, author={Faraji, Shaghayegh and Stano, Kelly L. and Yildiz, Ozkan and Li, Ang and Zhu, Yuntian and Bradford, Philip D.}, year={2015}, pages={17038–17047} }
 @article{fu_lu_dirican_chen_yanilmaz_shi_bradford_zhang_2014, title={Chamber-confined silicon-carbon nanofiber composites for prolonged cycling life of Li-ion batteries}, volume={6}, ISSN={["2040-3372"]}, url={https://publons.com/publon/26924684/}, DOI={10.1039/c4nr00518j}, abstractNote={Silicon is confined within the empty chambers of carbon nanofibers, in which the volume expansion of Si can be buffered and SEI formation is controlled. This self-supported composite is a promising electrode candidate for use in flexible batteries.}, number={13}, journal={NANOSCALE}, publisher={Royal Society of Chemistry (RSC)}, author={Fu, Kun and Lu, Yao and Dirican, Mahmut and Chen, Chen and Yanilmaz, Meltem and Shi, Quan and Bradford, Philip D. and Zhang, Xiangwu}, year={2014}, pages={7489–7495} }
 @article{stano_carroll_padbury_mccord_jur_bradford_2014, title={Conformal Atomic Layer Deposition of Alumina on Millimeter Tall, Vertically-Aligned Carbon Nanotube Arrays}, volume={6}, ISSN={["1944-8244"]}, DOI={10.1021/am505107s}, abstractNote={Atomic layer deposition (ALD) can be used to coat high aspect ratio and high surface area substrates with conformal and precisely controlled thin films. Vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) with lengths up to 1.5 mm were conformally coated with alumina from base to tip. The nucleation and growth behaviors of Al2O3 ALD precursors on the MWCNTs were studied as a function of CNT surface chemistry. CNT surfaces were modified through a series of post-treatments including pyrolytic carbon deposition, high temperature thermal annealing, and oxygen plasma functionalization. Conformal coatings were achieved where post-treatments resulted in increased defect density as well as the extent of functionalization, as characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Using thermogravimetric analysis, it was determined that MWCNTs treated with pyrolytic carbon and plasma functionalization prior to ALD coating were more stable to thermal oxidation than pristine ALD coated samples. Functionalized and ALD coated arrays had a compressive modulus more than two times higher than a pristine array coated for the same number of cycles. Cross-sectional energy dispersive X-ray spectroscopy confirmed that Al2O3 could be uniformly deposited through the entire thickness of the vertically aligned MWCNT array by manipulating sample orientation and mounting techniques. Following the ALD coating, the MWCNT arrays demonstrated hydrophilic wetting behavior and also exhibited foam-like recovery following compressive strain.}, number={21}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Stano, Kelly L. and Carroll, Murphy and Padbury, Richard and McCord, Marian and Jur, Jesse S. and Bradford, Philip D.}, year={2014}, month={Nov}, pages={19135–19143} }
 @article{zhou_wang_faraji_bradford_li_zhu_2014, title={Mechanical and electrical properties of aligned carbon nanotube/carbon matrix composites}, volume={75}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2014.04.008}, abstractNote={To synthesize carbon nanotube/carbon matrix (CNT/C) composites rivaling or exceeding the mechanical and electrical properties of current carbon fiber/carbon matrix composites, it is essential to align carbon nanotubes in the composite. In this work, we fabricated CNT/polyacrylonitrile (PAN) precursor composites with high degree of CNT alignment, and carbonized and graphitized them at high temperatures. Carbonizing the precursor composites significantly improved their elastic modulus, strength, and electrical conductivity. The matrix was uniformly carbonized and highly graphitized. The excellent mechanical and electrical properties make the CNT/C composites promising for many high temperature aerospace applications.}, journal={CARBON}, author={Zhou, Zhou and Wang, Xin and Faraji, Shaghayegh and Bradford, Philip D. and Li, Qingwen and Zhu, Yuntian}, year={2014}, month={Aug}, pages={307–313} }
 @article{li_chen_fu_white_zhao_bradford_zhang_2014, title={Nanosized Ge@CNF, Ge@C@CNF and Ge@CNF@C composites via chemical vapour deposition method for use in advanced lithium-ion batteries}, volume={253}, ISSN={["1873-2755"]}, url={https://publons.com/publon/11652066/}, DOI={10.1016/j.jpowsour.2013.12.017}, abstractNote={Three distinct Ge nanoparticle-filled carbon nanofiber (CNF) composites, [email protected], [email protected]@CNF and [email protected]@C, were fabricated by chemical vapor deposition (CVD) and electrospinning techniques. These different structures were prepared by: 1) dispersing Ge nanoparticles into CNF, 2) adding carbon-coated Ge nanoparticles ([email protected]) prepared by CVD into CNF, and 3) depositing CVD carbon onto [email protected], respectively. Compared with the [email protected] composite, both [email protected]@CNF and [email protected]@C had additional amorphous carbon coating fabricated by the CVD method. The three composites were studied as binder-free electrodes for rechargeable lithium-ion batteries. Raw Ge anode materials suffered from serious volume changes and nanoparticle aggregations during cycling, resulting in pulverization and capacity loss. However, carbon nanofiber and the supplemental CVD carbon layer in these nanofiber composites could help preserve the structural integrity of the alloy anode materials during repeated cycling, and consequently, lead to improved cycling stability. In this work, it was found that among the three composites, [email protected]@C exhibited the highest capacity retention of 89% at the 50th cycle due to the structurally-durable thorn-like Ge morphology and the additional CVD carbon confinement. [email protected] and [email protected]@CNF encountered rapid capacity loss because large Ge clusters were formed and jeopardized the integrity of the electrode structure during cycling.}, journal={JOURNAL OF POWER SOURCES}, publisher={Elsevier BV}, author={Li, Shuli and Chen, Chen and Fu, Kun and White, Ryan and Zhao, Chengxin and Bradford, Philip D. and Zhang, Xiangwu}, year={2014}, month={May}, pages={366–372} }
 @article{thiagarajan_wang_bradford_zhu_yuan_2014, title={Stabilizing carbon nanotube yarns using chemical vapor infiltration}, volume={90}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2013.10.008}, abstractNote={Carbon nanotube (CNT) yarns exhibit high strength, low density, and relatively good conductivity and piezoresistivity, which makes them an ideal candidate for many advanced applications such as reinforcements for multifunctional composites. However, CNT yarns usually lack the required property stability under load. In this paper a method for stabilizing CNT yarn using chemical vapor infiltration (CVI) to infiltrate and deposit pyrocarbon into CNT yarns is reported. The deposited pyrocarbon effectively binds neighboring CNTs to inhibit inter-nanotube sliding under load, which consequently stabilize the CNT yarns. Relaxation tests showed that compared to pristine CNT yarns, the stabilized yarns have higher electrical stability as well as load retention (∼93% versus ∼61%). There was also a concomitant increase in density along with improved electrical conductivity, mechanical strength and stiffness. Furthermore, under sonication the CVI treated yarns resisted disintegration, making them suitable for electrochemical applications.}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Thiagarajan, V. and Wang, X. and Bradford, P. D. and Zhu, Y. T. and Yuan, F. G.}, year={2014}, month={Jan}, pages={82–87} }
 @article{faraji_stano_rost_maria_zhu_bradford_2014, title={Structural annealing of carbon coated aligned multi-walled carbon nanotube sheets}, volume={79}, ISSN={0008-6223}, url={http://dx.doi.org/10.1016/J.CARBON.2014.07.049}, DOI={10.1016/j.carbon.2014.07.049}, abstractNote={Sheets of aligned multi-walled carbon nanotubes (AMWCNTs) were used to study the structural annealing of pyrolytic carbon (PyC) coatings with various thicknesses on MWCNTs. PyC was deposited using chemical vapor infiltration and the thickness was controlled via the infiltration time. Structural annealing of the PyC coated AMWCNT (AMWCNT/C) sheets at 2150 °C provided different results for different thickness coatings. Transmission electron microscopy images showed that the carbon deposited from acetylene formed laminar PyC coatings, resembling rough tube walls, on the CNT surfaces. Following the high temperature heat treatment, coatings from short PyC deposition times changed their structure, resulting in radial growth of the MWCNTs. Raman and X-ray diffraction measurements also revealed that the radially grown MWCNTs had graphitic quality very close to pristine nanotubes after annealing. Electrical conductivity of AMWCNT/C sheets after high temperature heat treatment was twice that of pristine AMWCNT sheets. The focus of this study was to determine the PyC coating thickness at which a rough PyC coating would no longer change its structure into new CNT walls. The samples treated longer than 30 min had much more disordered PyC deposited on the surface and the additional material did not form additional tube walls after thermal annealing.}, journal={Carbon}, publisher={Elsevier BV}, author={Faraji, Shaghayegh and Stano, Kelly and Rost, Christina and Maria, Jon-Paul and Zhu, Yuntian and Bradford, Philip D.}, year={2014}, month={Nov}, pages={113–122} }
 @article{fu_li_dirican_chen_lu_zhu_li_cao_bradford_zhang_et al._2014, title={Sulfur gradient-distributed CNF composite: a self-inhibiting cathode for binder-free lithium-sulfur batteries}, volume={50}, ISSN={["1364-548X"]}, url={https://publons.com/publon/26924687/}, DOI={10.1039/c4cc04970e}, abstractNote={A novel sulfur gradient cathode was developed with a high specific capacity and improved cycling stability for Li–S batteries.}, number={71}, journal={CHEMICAL COMMUNICATIONS}, publisher={Royal Society of Chemistry (RSC)}, author={Fu, Kun and Li, Yanpeng and Dirican, Mahmut and Chen, Chen and Lu, Yao and Zhu, Jiadeng and Li, Yao and Cao, Linyou and Bradford, Philip D. and Zhang, Xiangwu and et al.}, year={2014}, pages={10277–10280} }
 @article{fu_yildiz_bhanushali_wang_stano_xue_zhang_bradford_2013, title={Aligned Carbon Nanotube-Silicon Sheets: A Novel Nano-architecture for Flexible Lithium Ion Battery Electrodes}, volume={25}, ISSN={["1521-4095"]}, url={https://publons.com/publon/7178364/}, DOI={10.1002/adma.201301920}, abstractNote={Aligned carbon nanotube sheets provide an engineered scaffold for the deposition of a silicon active material for lithium ion battery anodes. The sheets are low-density, allowing uniform deposition of silicon thin films while the alignment allows unconstrained volumetric expansion of the silicon, facilitating stable cycling performance. The flat sheet morphology is desirable for battery construction.}, number={36}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Fu, Kun and Yildiz, Ozkan and Bhanushali, Hardik and Wang, Yongxin and Stano, Kelly and Xue, Leigang and Zhang, Xiangwu and Bradford, Philip D.}, year={2013}, month={Sep}, pages={5109–5114} }
 @article{yildiz_bradford_2013, title={Aligned carbon nanotube sheet high efficiency particulate air filters}, volume={64}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2013.07.066}, abstractNote={Aerosol filters, made with conventional micro-fiber fabrics, are designed to efficiently capture small particles from the air. Filters constructed of nano-fiber fabric structures provide even greater filtration efficiency than conventional micro-fiber fabrics due to their higher surface area and smaller pore size. Carbon nanotubes (CNTs) are very small diameter fibers that have the potential to be integrated into filters to further increase particle capture efficiency. In this study, CNT sheets, drawn from millimeter tall CNT arrays, were integrated between traditional micro-fiber fabrics to produce aerosol filters. The filtration performance of the novel filters showed that when the number of CNTs layers increased, the filtration efficiency increased dramatically, while the pressure drop also increased. In order to meet high efficiency particulate air (HEPA) filter requirements with a reasonable pressure drop, CNTs were laid in a cross-plied structure within the filter. The results demonstrated that the three layer cross-ply structure provided 99.98% filtration efficiency at 0.3 μm particle size at a 10 cm/s face velocity, making it a viable method for producing low basis weight HEPA filters utilizing CNTs as the main filtration component.}, journal={CARBON}, author={Yildiz, Ozkan and Bradford, Philip D.}, year={2013}, month={Nov}, pages={295–304} }
 @article{stano_chapla_carroll_nowak_mccord_bradford_2013, title={Copper-Encapsulated Vertically Aligned Carbon Nanotube Arrays}, volume={5}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/AM402964E}, DOI={10.1021/AM402964E}, abstractNote={A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites.}, number={21}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Stano, Kelly L. and Chapla, Rachel and Carroll, Murphy and Nowak, Joshua and McCord, Marian and Bradford, Philip D.}, year={2013}, month={Oct}, pages={10774–10781} }
 @article{fu_xue_yildiz_li_lee_li_xu_zhou_bradford_zhang_et al._2013, title={Effect of CVD carbon coatings on Si@CNF composite as anode for lithium-ion batteries}, volume={2}, ISSN={["2211-3282"]}, url={https://publons.com/publon/7178363/}, DOI={10.1016/j.nanoen.2013.03.019}, abstractNote={Lithium-ion battery (LIB) anodes with high capacity and binder free structure were synthesized from carbon nanofibers that contained silicon nanoparticles (Si@CNF). The particle filled nonwoven structures were produced by an electrospinning and subsequent carbonization process. Pristine Si@CNF composites had Si nanoparticles exposed on the fiber surface. As produced, the Si nanoparticles could become detached from the nanofiber surface during cycling, causing severe structural damage and capacity loss. In order to prevent Si from detaching from the nanofiber surface, the Si@CNF composite was then treated with a thermal chemical vapor deposition (CVD) technique to make Si completely coated with a carbon matrix. The carbon coated Si@CNF (Si@CNF-C) composites were synthesized with different Si contents (10, 30, and 50 wt%) for different CVD treatment times (30, 60, and 90 min). It was found that the initial coulombic efficiency of Si@CNF-C could be increased via the amorphous carbon by stabilizing solid-electrolyte-interface (SEI) formation on surface. The capacity and cyclic stability were improved by the CVD carbon coating, especially for the 30 wt% Si@CNF-C composite with 90 min CVD coating, a CVD amorphous carbon coating of less than 1% by weight on Si@CNF composites contributed to more than 200% improvement in cycling performance. Results indicate that the CVD carbon coating is an effective approach to improve the electrochemical properties of Si@CNF composites making this a potential route to obtain high-energy density anode materials for LIBs.}, number={5}, journal={NANO ENERGY}, author={Fu, K. and Xue, L. G. and Yildiz, O. and Li, S. L. and Lee, H. and Li, Y. and Xu, G. J. and Zhou, L. and Bradford, P. D. and Zhang, Xiangwu and et al.}, year={2013}, month={Sep}, pages={976–986} }
 @article{liu_zhao_inoue_wang_bradford_kim_qiu_zhu_2012, title={Poly(vinyl alcohol) reinforced with large-diameter carbon nanotubes via spray winding}, volume={43}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2011.12.029}, abstractNote={For practical application of carbon nanotube (CNT)/polymer composites, it is critical to produce the composites at high speed and large scale. In this study, multi-walled carbon nanotubes (MWNTs) with large diameter (∼45 nm) and polyvinyl alcohol (PVA) were used to increase the processing speed of a recently developed spraying winding technique. The effect of the different winding speed and sprayed solution concentration to the performance of the composite films were investigated. The CNT/PVA composites exhibit tensile strength of up to 1 GPa, and modulus of up to 70 GPa, with a CNT weight fraction of 53%. In addition, an electrical conductivity of 747 S/cm was obtained for the CNT/PVA composites. The good mechanical and electrical properties are attributed to the uniform CNTs and PVA matrix integration and the high degree of tube alignment.}, number={4}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Liu, Wei and Zhao, Haibo and Inoue, Yoku and Wang, Xin and Bradford, Philip D. and Kim, Hyungsup and Qiu, Yiping and Zhu, Yuntian}, year={2012}, month={Apr}, pages={587–592} }
 @article{wang_yong_li_bradford_liu_tucker_cai_wang_yuan_zhu_2012, title={Ultrastrong, Stiff and Multifunctional Carbon Nanotube Composites}, volume={1}, ISSN={2166-3831}, url={http://dx.doi.org/10.1080/21663831.2012.686586}, DOI={10.1080/21663831.2012.686586}, abstractNote={Carbon nanotubes (CNTs) are an order of magnitude stronger than any other current engineering fiber. However, for the past two decades, it has been a challenge to utilize their reinforcement potential in composites. Here, we report CNT composites with unprecedented multifunctionalities, including record high strength (3.8 GPa), high Young's modulus (293 GPa), electrical conductivity (1230 S·cm −1), and thermal conductivity (41 W m −1 K −1). These superior properties are derived from the long length, high volume fraction, good alignment and reduced waviness of the CNTs, which were produced by a novel-processing approach that can be easily scaled up for industrial production.}, number={1}, journal={Materials Research Letters}, publisher={Informa UK Limited}, author={Wang, X. and Yong, Z.Z. and Li, Q.W. and Bradford, P.D. and Liu, W. and Tucker, D.S. and Cai, W. and Wang, H. and Yuan, F.G. and Zhu, Y.T.}, year={2012}, month={Oct}, pages={19–25} }
 @article{wang_krommenhoek_bradford_gong_tracy_parsons_luo_zhu_2011, title={Coating Alumina on Catalytic Iron Oxide Nanoparticles for Synthesizing Vertically Aligned Carbon Nanotube Arrays}, volume={3}, ISSN={1944-8244 1944-8252}, url={http://dx.doi.org/10.1021/am201082m}, DOI={10.1021/am201082m}, abstractNote={To synthesize long and uniform vertically aligned carbon nanotube (VACNT) arrays, it is essential to use catalytic nanoparticles (NPs) with monodisperse sizes and to avoid NP agglomeration at the growth temperature. In this work, VACNT arrays were grown on chemically synthesized Fe(3)O(4) NPs of diameter 6 nm by chemical vapor deposition. Coating the NPs with a thin layer of Al(2)O(3) prior to CNT growth preserves the monodisperse sizes, resulting in uniform, thick and dense VACNT arrays. Comparison with uncoated NPs shows that the Al(2)O(3) coating effectively prevents the catalyst NPs from sintering and coalescing, resulting in improved control over VACNT growth.}, number={11}, journal={ACS Applied Materials & Interfaces}, publisher={American Chemical Society (ACS)}, author={Wang, Xin and Krommenhoek, Peter J. and Bradford, Philip D. and Gong, Bo and Tracy, Joseph B. and Parsons, Gregory N. and Luo, Tzy-Jiun M. and Zhu, Yuntian T.}, year={2011}, month={Oct}, pages={4180–4184} }
 @article{wang_bradford_liu_zhao_inoue_maria_li_yuan_zhu_2011, title={Mechanical and electrical property improvement in CNT/Nylon composites through drawing and stretching}, volume={71}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2011.07.023}, abstractNote={The excellent mechanical properties of carbon nanotubes (CNTs) make them the ideal reinforcements for high performance composites. The misalignment and waviness of CNTs within composites are two major issues that limit the reinforcing efficiency. We report an effective method to increase the strength and stiffness of high volume fraction, aligned CNT composites by reducing CNT waviness using a drawing and stretching approach. Stretching the composites after fabrication improved the ultimate strength by 50%, 150%, and 190% corresponding to stretch ratios of 2%, 4% and 7%, respectively. Improvement of the electrical conductivities exhibited a similar trend. These results demonstrate the importance of straightening and aligning CNTs in improving the composite strength and electrical conductivity.}, number={14}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Wang, Xin and Bradford, Philip D. and Liu, Wei and Zhao, Haibo and Inoue, Yoku and Maria, Jon-Paul and Li, Qingwen and Yuan, Fuh-Gwo and Zhu, Yuntian}, year={2011}, month={Sep}, pages={1677–1683} }
 @article{liu_zhang_xu_bradford_wang_zhao_zhang_jia_yuan_li_et al._2011, title={Producing superior composites by winding carbon nanotubes onto a mandrel under a poly(vinyl alcohol) spray}, volume={49}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2011.06.089}, abstractNote={A simple method for processing high-performance carbon nanotube (CNT)/poly(vinyl alcohol) (PVA) composites by coupling the spraying of a PVA solution with the continuous winding of CNT sheets from an array onto a rotating mandrel is reported. This method allows the CNT composites to have a high CNT volume fraction, while having a high degree of alignment, long CNTs, and good integration with the matrix, which are extremely difficult to realize simultaneously by other processes. As a result, the composites have a toughness, strength and electrical conductivity up to 100 J/g, 1.8 GPa and 780 S/cm, respectively. Such a one-step synthesis process is promising for industrial productions and also works for different types of polymers.}, number={14}, journal={CARBON}, author={Liu, Wei and Zhang, Xiaohua and Xu, Geng and Bradford, Philip D. and Wang, Xin and Zhao, Haibo and Zhang, Yingying and Jia, Quanxi and Yuan, Fuh-Gwo and Li, Qingwen and et al.}, year={2011}, month={Nov}, pages={4786–4791} }
 @article{bradford_wang_zhao_zhu_2011, title={Tuning the compressive mechanical properties of carbon nanotube foam}, volume={49}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2011.03.012}, abstractNote={A post-growth chemical vapor deposition (CVD) treatment was used to tune the compressive mechanical properties of carbon nanotube (CNT) arrays. Millimeter tall CNT arrays with low compressive resilience were changed to a foam-like material with high compressive strength and almost complete recovery upon unloading. The foam was tuned to provide a range of compressive properties for various applications. The treated arrays demonstrated compressive strength up to 35× greater than the as-grown CNT array. Unlike polymeric foams, the CNT foam did not decompose after exposure to high temperatures. Investigation of the foam structure revealed that the CVD treatment increased CNT diameter through radial growth, while increasing the CNT surface roughness. The morphological changes help to explain the increase in CNT array compressive strength and the transition from permanent array deformation to foam-like recovery after compressive loading.}, number={8}, journal={CARBON}, author={Bradford, Philip D. and Wang, Xin and Zhao, Haibo and Zhu, Y. T.}, year={2011}, month={Jul}, pages={2834–2841} }
 @article{bradford_wang_zhao_maria_jia_zhu_2010, title={A novel approach to fabricate high volume fraction nanocomposites with long aligned carbon nanotubes}, volume={70}, ISSN={["1879-1050"]}, DOI={10.1016/j.compscitech.2010.07.020}, abstractNote={Conventional micro-fiber-reinforced composites provide insight into critical structural features needed for obtaining maximum composite strength and stiffness: the reinforcements should be long, well aligned in a unidirectional orientation, and should have a high reinforcement volume fraction. It has long been a challenge for researchers to process CNT composites with such structural features. Here we report a method to quickly produce macroscopic CNT composites with a high volume fraction of millimeter long, well aligned CNTs. Specifically, we use the novel method, shear pressing, to process tall, vertically aligned CNT arrays into dense aligned CNT preforms, which are subsequently processed into composites. Alignment was confirmed through SEM analysis while a CNT volume fraction in the composites was calculated to be 27%, based on thermogravimetric analysis data. Tensile testing of the preforms and composites showed promising mechanical properties with tensile strengths reaching 400 MPa.}, number={13}, journal={COMPOSITES SCIENCE AND TECHNOLOGY}, author={Bradford, Philip D. and Wang, Xin and Zhao, Haibo and Maria, Jon-Paul and Jia, Quanxi and Zhu, Y. T.}, year={2010}, month={Nov}, pages={1980–1985} }
 @article{zhao_bradford_wang_liu_luo_jia_zhu_yuan_2010, title={An intermetallic Fe-Zr catalyst used for growing long carbon nanotube arrays}, volume={64}, ISSN={["1873-4979"]}, DOI={10.1016/j.matlet.2010.05.045}, abstractNote={Metallic nanoparticles containing single and binary components have been known for their catalytic properties to grow carbon nanotube (CNT) arrays. In this paper, an intermetallic catalyst consisting of iron and zirconium was used to grow millimeter long, well aligned arrays. The Fe–Zr catalysts enabled the growth of 1.7 mm-long carbon nanotube arrays in 45 min. A comparison with pure iron catalyst indicated that adding Zr to iron can stabilize the Fe catalyst at the CNT growth temperature and moderate its reactivity. SEM images showed the different growth behaviors for Fe–Zr and Fe catalysts. The long, uniform CNT arrays grown here have potential applications in many advanced composites.}, number={18}, journal={MATERIALS LETTERS}, author={Zhao, Haibo and Bradford, Philip D. and Wang, Xin and Liu, Wei and Luo, Tzy Jiun Mark and Jia, Quanxi and Zhu, Yuntian and Yuan, Fuh-Gwo}, year={2010}, month={Sep}, pages={1947–1950} }
 @article{bogdanovich_bradford_2010, title={Carbon nanotube yarn and 3-D braid composites. Part I: Tensile testing and mechanical properties analysis}, volume={41}, ISSN={["1878-5840"]}, DOI={10.1016/j.compositesa.2009.10.002}, abstractNote={Macroscopic textile preforms were produced with a multi-level hierarchical carbon nanotube (CNT) structure: nanotubes, bundles, spun single yarns, plied yarns and 3-D braids. The 3-D braided preform was the first of its kind produced by textile processing technique and used as a composite reinforcement consisting solely of carbon nanotubes. Four different epoxy systems that possessed a wide range of mechanical properties (owed to an added modifier) were infused into the CNT yarns and 3-D braids. Mechanical characterization of the resulting composites was conducted through the use of tensile testing. It was found that the tensile strength, stiffness and, especially, strain-to-failure values for each preform type were close regardless of the properties of the matrix whose strain-to-failure values ranged from 3.6% to 89%. This is hypothetically attributed to the nano-scale interaction between individual nanotubes and polymeric macromolecules in the composites. This hypothesis is validated by the Dynamic Mechanical Analysis results in Part II.}, number={2}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Bogdanovich, Alexander E. and Bradford, Philip D.}, year={2010}, month={Feb}, pages={230–237} }
 @article{bradford_bogdanovich_2010, title={Carbon nanotube yarn and 3-D braid composites. Part II: Dynamic mechanical analysis}, volume={41}, ISSN={["1359-835X"]}, DOI={10.1016/j.compositesa.2009.10.003}, abstractNote={Macroscopic textile preforms were produced with a multi-level hierarchical carbon nanotube (CNT) structure: nanotubes, bundles, spun single yarns, plied yarns and 3-D braids. In tensile tests, reported in Part I, composites produced from the 3-D braids exhibited unusual mechanical behavior effects. The proposed physical hypotheses explained those effects by molecular level interactions and molecular hindrance of the epoxy chains with individual carbon nanotubes occupying about 40% of the composite volume. Dynamic mechanical analysis was used in this Part II to study the molecular transitions of neat epoxy resin samples and their corresponding CNT yarn composite samples with varying matrix properties. Dramatic effects on the intensity and temperature at which α-transitions occured, were recorded, as well as a marked effect on the smaller segmental motions, or β-transitions. These changes in the matrix assist in explaining the mechanical test data presented in Part I and the proposed physical explanation of those data.}, number={2}, journal={COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING}, author={Bradford, Philip D. and Bogdanovich, Alexander E.}, year={2010}, month={Feb}, pages={238–246} }
 @article{zhao_zhang_bradford_zhou_jia_yuan_zhu_2010, title={Carbon nanotube yarn strain sensors}, volume={21}, ISSN={["1361-6528"]}, DOI={10.1088/0957-4484/21/30/305502}, abstractNote={Carbon nanotube (CNT) based sensors are often fabricated by dispersing CNTs into different types of polymer. In this paper, a prototype carbon nanotube (CNT) yarn strain sensor with excellent repeatability and stability for in situ structural health monitoring was developed. The CNT yarn was spun directly from CNT arrays, and its electrical resistance increased linearly with tensile strain, making it an ideal strain sensor. It showed consistent piezoresistive behavior under repetitive straining and unloading, and good resistance stability at temperatures ranging from 77 to 373 K. The sensors can be easily embedded into composite structures with minimal invasiveness and weight penalty. We have also demonstrated their ability to monitor crack initiation and propagation.}, number={30}, journal={NANOTECHNOLOGY}, author={Zhao, Haibo and Zhang, Yingying and Bradford, Philip D. and Zhou, Qian and Jia, Quanxi and Yuan, Fuh-Gwo and Zhu, Yuntian}, year={2010}, month={Jul} }
 @article{bradford_bogdanovich_2008, title={Electrical conductivity study of carbon nanotube yarns, 3-D hybrid braids and their composites}, volume={42}, ISSN={["1530-793X"]}, DOI={10.1177/0021998308092206}, abstractNote={ Long continuous yarns consisting solely of carbon nanotubes may be the future of specialty composites requiring unique multi-functional properties. Many of such yarns were incorporated in a hybrid composite here, to demonstrate for the first time, their effect on increasing the electrical conductivity of an otherwise insulating composite. Six-ply nanotube yarns produced by University of Texas at Dallas were used as a raw material in this study. Thirty-six ends of such yarn were utilized in a 3-D braiding process along with nine axial bundles of glass fibers. The experimental study of the electrical conductivity of the produced nanotube yarns, 3-D braids and composites made thereof is described; the results for different tested materials are mutually compared and discussed. Some non-trivial effects attributed to the complex multi-level hierarchy and nano-scale building blocks of the studied materials are revealed. Special attention is paid to a proper interpretation of the obtained experimental results, because the tested materials represent complex discrete networks of numerous electrically conductive elements. }, number={15}, journal={JOURNAL OF COMPOSITE MATERIALS}, author={Bradford, Philip D. and Bogdanovich, Alexander E.}, year={2008}, month={Aug}, pages={1533–1545} }
 @article{bogdanovich_bradford_mungalov_fang_zhang_baughman_hudson_2007, title={Fabrication and mechanical characterization of carbon nanotube yarns, 3-D braids, and their composites}, volume={43}, number={1}, journal={SAMPE Journal}, author={Bogdanovich, A. and Bradford, P. and Mungalov, D. and Fang, S. L. and Zhang, M. and Baughman, R. H. and Hudson, S.}, year={2007}, pages={6–19} }