@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{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{wang_epstein_tzeng_2014, title={Analysis of Gene-Gene Interactions Using Gene-Trait Similarity Regression}, volume={78}, ISSN={["1423-0062"]}, DOI={10.1159/000360161}, abstractNote={Objective: Gene-gene interactions (G×G) are important to study because of their extensiveness in biological systems and their potential in explaining missing heritability of complex traits. In this work, we propose a new similarity-based test to assess G×G at the gene level, which permits the study of epistasis at biologically functional units with amplified interaction signals. Methods: Under the framework of gene-trait similarity regression (SimReg), we propose a gene-based test for detecting G×G. SimReg uses a regression model to correlate trait similarity with genotypic similarity across a gene. Unlike existing gene-level methods based on leading principal components (PCs), SimReg summarizes all information on genotypic variation within a gene and can be used to assess the joint/interactive effects of two genes as well as the effect of one gene conditional on another. Results: Using simulations and a real data application to the Warfarin study, we show that the SimReg G×G tests have satisfactory power and robustness under different genetic architecture when compared to existing gene-based interaction tests such as PC analysis or partial least squares. A genome-wide association study with approx. 20,000 genes may be completed on a parallel computing system in 2 weeks.}, number={1}, journal={HUMAN HEREDITY}, author={Wang, Xin and Epstein, Michael P. and Tzeng, Jung-Ying}, year={2014}, pages={17–26} }
 @misc{di_wang_xing_zhang_zhang_lu_li_zhu_2014, title={Dry-processable carbon nanotubes for functional devices and composites}, volume={10}, number={22}, journal={Small (Weinheim An Der Bergstrasse, Germany)}, author={Di, J. T. and Wang, X. and Xing, Y. J. and Zhang, Y. Y. and Zhang, X. H. and Lu, W. B. and Li, Q. W. and Zhu, Y. T. T.}, year={2014}, pages={4606–4625} }
 @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{jiang_wang_zhu_hui_qiu_2014, title={Mechanical, electrical and thermal properties of aligned carbon nanotube/polyimide composites}, volume={56}, ISSN={["1879-1069"]}, DOI={10.1016/j.compositesb.2013.08.064}, abstractNote={Carbon nanotubes (CNTs) have high strength and modulus, large aspect ratio, and good electrical and thermal conductivities, which make them attractive for fabricating composite. The poly(biphenyl dianhydride-p-phenylenediamine) (BPDA/PDA) polyimide has good mechanical and thermal performances and is herein used as matrix in unidirectional carbon nanotube composites for the first time. The strength and modulus of the composite increase by 2.73 and 12 times over pure BPDA–PDA polyimide, while its electrical conductivity reaches to 183 S/cm, which is 1018 times over pure polyimide. The composite has excellent high temperature resistance, and its thermal conductivity is beyond what has been achieved in previous studies. The improved properties of the composites are due to the long CNT length, high level of CNT alignment, high CNT volume fraction and good CNT dispersion in polyimide matrix. The composite is promising for applications that require high strength, lightweight, or high electrical and thermal conductivities.}, journal={COMPOSITES PART B-ENGINEERING}, author={Jiang, Qian and Wang, Xin and Zhu, Yuntian and Hui, David and Qiu, Yiping}, year={2014}, month={Jan}, pages={408–412} }
 @article{schmidt_wang_zhu_sombers_2013, title={Carbon Nanotube Yarn Electrodes for Enhanced Detection of Neurotransmitter Dynamics in Live Brain Tissue}, volume={7}, ISSN={["1936-086X"]}, DOI={10.1021/nn402857u}, abstractNote={This work demonstrates the potential of nanoscale carbon electrode materials for improved detection of electroactive neurotransmitter dynamics in the brain. Individual multiwalled carbon nanotubes were synthesized via chemical vapor deposition, spun into yarns, and used in the fabrication of disk microelectrodes that were subsequently characterized using scanning electron and atomic force microscopies. The carbon nanotube yarn electrodes were coupled with fast-scan cyclic voltammetry and used to discriminately detect rapid neurotransmitter fluctuations in acute brain slices. The results demonstrate that the distinct structural and electronic properties of the nanotubes result in improved selectivity, sensitivity, and spatial resolution, as well as faster apparent electron transfer kinetics when compared to the conventional carbon-fiber microelectrodes typically used in vivo.}, number={9}, journal={ACS NANO}, author={Schmidt, Andreas C. and Wang, Xin and Zhu, Yuntian and Sombers, Leslie A.}, year={2013}, month={Sep}, pages={7864–7873} }
 @article{wang_jiang_xu_cai_inoue_zhu_2013, title={Effect of carbon nanotube length on thermal, electrical and mechanical properties of CNT/bismaleimide composites}, volume={53}, ISSN={["1873-3891"]}, DOI={10.1016/j.carbon.2012.10.041}, abstractNote={Multi-wall carbon nanotubes (MWCNTs) with lengths of 0.65–1.3 mm were used to fabricate aligned and continuous MWCNT/bismaleimide composites. We found that longer CNTs resulted in higher thermal and electrical conductivities of the composites. The tensile strength and Young’s modulus, however, exhibited no CNT length dependency. Investigation of the CNT morphology by transmission electron microscopy revealed that the average nanotube diameter and wall number also increased with the CNT length, while the aspect ratio remained nearly unchanged. The structural changes significantly affected the phonon and electron transport in the composite structure, but the interplay of increased CNT length and diameter led to no appreciable change in the mechanical properties of the composites.}, journal={CARBON}, author={Wang, Xin and Jiang, Qian and Xu, Weizong and Cai, Wei and Inoue, Yoku and Zhu, Yuntian}, year={2013}, month={Mar}, pages={145–152} }
 @article{liu_zhao_yong_xu_wang_xu_hui_qiu_2013, title={Improving mechanical and electrical properties of oriented polymer-free multi-walled carbon nanotube paper by spraying while winding}, volume={53}, ISSN={["1879-1069"]}, DOI={10.1016/j.compositesb.2013.05.043}, abstractNote={In this study, a new method is introduced for fabricating carbon nanotube (CNT) paper, in which the solvent is sprayed on the CNT sheet while it is wound on a rotating mandrel. As the solvent evaporated, the capillary force pulls CNT closer together, resulting in a CNT paper with a high degree of alignment and a high packing density. Three batches of multi-walled CNTs with different wall thicknesses, tube diameters and lengths are utilized for synthesizing highly oriented CNT papers. It is found that CNTs with smallest diameter of 8 nm form strongest CNT paper with a tensile strength of 563 MPa and a tensile modulus of 15 GPa, while that made with CNTs of 10 nm diameter shows the highest electrical conductivity of 5.5 × 104 S/m.}, journal={COMPOSITES PART B-ENGINEERING}, author={Liu, Wei and Zhao, Haibo and Yong, Zhenzhong and Xu, Geng and Wang, Xin and Xu, Fujun and Hui, David and Qiu, Yiping}, year={2013}, month={Oct}, pages={342–346} }
 @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{xu_wang_zhu_zhu_2012, title={Wavy Ribbons of Carbon Nanotubes for Stretchable Conductors}, volume={22}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.201102032}, abstractNote={Abstract}, number={6}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Xu, Feng and Wang, Xin and Zhu, Yuntian and Zhu, Yong}, year={2012}, month={Mar}, pages={1279–1283} }
 @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} }