@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{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={Abstract}, 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{song_li_zhang_ma_guo_zhang_jiang_ma_2017, title={Decreasing bio-degradation rate of the hydrothermal-synthesizing coated mg alloy via pre-solid-solution treatment}, volume={10}, number={8}, journal={Materials}, author={Song, D. and Li, C. and Zhang, L. W. and Ma, X. L. and Guo, G. H. and Zhang, F. and Jiang, J. H. and Ma, A. B.}, year={2017} }
 @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{guo_song_jiang_ma_zhang_li_2016, title={Effect of synthesizing temperature on microstructure and electrochemical property of the hydrothermal conversion coating on Mg-2Zn-0.5Mn-Ca-Ce alloy}, volume={6}, number={3}, journal={Metals}, author={Guo, G. H. and Song, D. and Jiang, J. H. and Ma, A. B. and Zhang, L. W. and Li, C.}, year={2016} }
 @article{liu_ma_li_zhang_trimby_liao_li_zhao_zhu_2016, title={Effect of triple junctions on deformation twinning in a nanostructured Cu-Zn alloy: A statistical study using transmission Kikuchi diffraction}, volume={7}, journal={Beilstein Journal of Nanotechnology}, author={Liu, S. L. and Ma, X. L. and Li, L. Z. and Zhang, L. W. and Trimby, P. W. and Liao, X. Z. and Li, Y. S. and Zhao, Y. H. and Zhu, Y. T.}, year={2016}, pages={1501–1506} }
 @article{song_guo_jiang_zhang_ma_ma_chen_cheng_2016, title={Hydrothermal synthesis and corrosion behavior of the protective coating on Mg-2Zn-Mn-Ca-Ce alloy}, volume={26}, number={6}, journal={Progress in Natural Science}, author={Song, D. and Guo, G. H. and Jiang, J. H. and Zhang, L. W. and Ma, A. B. and Ma, X. L. and Chen, J. Q. and Cheng, Z. J.}, year={2016}, pages={590–599} }
 @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{fang_ma_zhang_zhu_2016, title={Nucleation of deformation twins in nanocrystalline fcc alloys}, volume={96}, ISSN={["1478-6443"]}, DOI={10.1080/14786435.2016.1240379}, abstractNote={Abstract An earlier dislocation model for predicting the grain size effect on deformation twinning in nanocrystalline (nc) face-centred-cubic (fcc) metals has been found valid for pure metals but problematic for alloys. The problem arises from the assumption that the stacking-fault energy (γSF) is twice the coherent twin-boundary energy (γfcc), which is approximately correct for pure fcc metals, but not for alloys. Here we developed a modified dislocation model to explain the deformation twinning nucleation in fcc alloy systems, where γSF ≠ 2γtwin. This model can explain the differences in the formations of deformation twins in pure metals and alloys, which is significant in low stacking-fault energy alloys. We also describe the procedure to calculate the optimum grain size for twinning in alloy systems and present a method to estimate γtwin.}, number={36}, journal={PHILOSOPHICAL MAGAZINE}, author={Fang, Xiaotian and Ma, Xiaolong and Zhang, Liwen and Zhu, Yuntian}, year={2016}, pages={3790–3802} }
 @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} }