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135 results on '"Zhao, Jingna"'

4. Vibration Damping of Carbon Nanotube Assembly Materials

Author

Zhao, Jingna, Wang, Fulin, Zhang, Xin, Liang, Linjie, Yang, Xueqin, Li, Qingwen, and Zhang, Xiaohua

Subjects
Condensed Matter - Materials Science
Abstract

Vibration reduction is of great importance in various engineering applications, and a material that exhibits good vibration damping along with high strength and modulus has become more and more vital. Owing to the superior mechanical property of carbon nanotube (CNT), new types of vibration damping material can be developed. This paper presents recent advancements, including our progresses, in the development of high-damping macroscopic CNT assembly materials, such as forests, gels, films, and fibers. In these assemblies, structural deformation of CNTs, zipping and unzipping at CNT connection nodes, strengthening and welding of the nodes, and sliding between CNTs or CNT bundles are playing important roles in determining the viscoelasticity, and elasticity as well. Towards the damping enhancement, strategies for micro-structure and interface design are also discussed.

Published
2017
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5. Evaluating the System Compliance in Testing Carbon Nanotube Fibers

Author

Jiang, Chunyang, Zhang, Xin, Zhao, Jingna, Zou, Jingyun, and Zhang, Xiaohua

Subjects
Condensed Matter - Materials Science
Abstract

System compliances of two testing machines (Keysight T150 and Instron 3365) were studied for the tensile testing of carbon nanotube (CNT) fibers. Due to the different gripping methods, the T150's system compliance was nearly zero, while that of the Instron was nonnegligible. By analyzing the data dispersion with the Weibull theory, a safe gauge length of >10 mm was suggested for CNT fibers. Therefore, a standard test procedure should involve the compliance evaluation, choice of gauge length, and Weibull statistical analysis., Comment: 7 pages, 5 figures

Published
2017

6. Assembly-Dependent Interfacial Property of Carbon Nanotube Fibers with Epoxy and Its Enhancement via Generalized Surface Sizing

Author

Lei, Chaoshuai, Zhao, Jingna, Zou, Jingyun, Jiang, Chunyang, Li, Min, Zhang, Xiaohua, Zhang, Zuoguang, and Li, Qingwen

Subjects
Condensed Matter - Materials Science
Abstract

In building up composite structures using carbon nanotube (CNT) fibers, the fiber-to-matrix interfacial shear strength (IFSS) is one of the most important issues. Originating from the assembly characteristics of CNT fiber, the IFSS strongly depends on the fiber's twisting level and densification level. Furthermore, there are rich ways to modify the fiber surface and thus enhance the IFSS, including the physical and chemical modification on fiber surface, the infiltration of matrix resin into CNT fiber, and the introduction of silane coupling agent. A new feature differing from carbon fibers is that all these treatments either change the fiber's surface structure or form a several-hundreds-nm-thick interphase inside rather than around the fiber. These "generalized" treatments obviously extend the common concept of surface sizing and can be used for various forms of CNT assembly structures., Comment: 7 pages, 5 figures

Published
2015
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7. Bio-Inspired Aggregation Control of Carbon Nanotubes for Ultra-Strong Composites

Author

Han, Yue, Zhang, Xiaohua, Yu, Xueping, Zhao, Jingna, Li, Shan, Liu, Feng, Gao, Peng, Zhang, Yongyi, Zhao, Tong, and Li, Qingwen

Subjects
Condensed Matter - Materials Science
Abstract

High performance nanocomposites require well dispersion and high alignment of the nanometer-sized components, at a high mass or volume fraction as well. However, the road towards such composite structure is severely hindered due to the easy aggregation of these nanometer-sized components. Here we demonstrate a big step to approach the ideal composite structure for carbon nanotube (CNT) where all the CNTs were highly packed, aligned, and unaggregated, with the impregnated polymers acting as interfacial adhesions and mortars to build up the composite structure. The strategy was based on a bio-inspired aggregation control to limit the CNT aggregation to be sub 20--50 nm, a dimension determined by the CNT growth. After being stretched with full structural relaxation in a multi-step way, the CNT/polymer (bismaleimide) composite yielded super-high tensile strengths up to 6.27--6.94 GPa, more than 100% higher than those of carbon fiber/epoxy composites, and toughnesses up to 117--192 MPa. We anticipate that the present study can be generalized for developing multifunctional and smart nanocomposites where all the surfaces of nanometer-sized components can take part in shear transfer of mechanical, thermal, and electrical signals.

Published
2015
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8. Wide-Range Tunable Dynamic Property of Carbon Nanotube-Based Fibers

Author

Zhao, Jingna, Zhang, Xiaohua, Pan, Zhijuan, and Li, Qingwen

Subjects
Condensed Matter - Materials Science
Abstract

Carbon nanotube (CNT) fiber is formed by assembling millions of individual tubes. The assembly feature provides the fiber with rich interface structures and thus various ways of energy dissipation, as reflected by the non-zero loss tangent (>0.028--0.045) at low vibration frequencies. A fiber containing entangled CNTs possesses higher loss tangents than a fiber spun from aligned CNTs. Liquid densification and polymer infiltration, the two common ways to increase the interfacial friction and thus the fiber's tensile strength and modulus, are found to efficiently reduce the damping coefficient. This is because the sliding tendency between CNT bundles can also be well suppressed by the high packing density and the formation of covalent polymer cross-links within the fiber. The CNT/bismaleimide composite fiber exhibited the smallest loss tangent, nearly as the same as that of carbon fibers. At a higher level of the assembly structure, namely a multi-ply CNT yarn, the inter-fiber friction and sliding tendency obviously influence the yarn's damping performance, and the loss tangent can be tuned within a wide range, as similar to carbon fibers, nylon yarns, or cotton yarns. The wide-range tunable dynamic properties allow new applications ranging from high quality factor materials to dissipative systems.

Published
2015
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16. Scalp acupuncture plus low-frequency rTMS promotes repair of brain white matter tracts in stroke patients: A DTI study

Author

Ning Zhao, Jingna Zhang, Mingguo Qiu, Chunrong Wang, Yun Xiang, Hui Wang, Jingwen Xie, Shu Liu, Jing Wu

Subjects
tract-based spatial statistics, scalp acupuncture, low frequency repetitive transcranial magnetic stimulation, stroke, white matter tracts, Neurosciences. Biological psychiatry. Neuropsychiatry, RC321-571
Abstract

To study the clinical effects of scalp acupuncture plus low frequency rTMS in hemiplegic stroke patients. A total of 28 hemiplegic stroke patients were recruited and randomly assigned to the experimental group (scalp acupuncture low frequency rTMS routine rehabilitation treatment) or the control group (scalp acupuncture routine rehabilitation treatment). All patients received a diffusion tensor imaging examination on the day of admission and on the fourteenth day. Compared with pre-treatment, the upper limb motor function score and ability of daily life score increased significantly in the two groups, and motor function improvement was much greater in the experimental group. Fractional anisotropy values significantly increased in white matter tracts, such as the corticospinal tract, forceps minor, superior longitudinal fasciculus and uncinate fasciculus in the two groups. Compared with pre-treatment, the fractional anisotropy values increased and mean diffusion values decreased synchronously in the forceps minor, left inferior fronto-occipital fasciculus, left inferior longitudinal fasciculus, left superior longitudinal fasciculus and left uncinate fasciculus in the experimental group. Before and after treatment, there were no significant differences in the changes of fractional anisotropy values between the two groups, but the changes of the mean diffusion values in the experimental group were much greater than those in the control group in the left superior longitudinal fasciculus and the left uncinate fasciculus ($p

Published
2018
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36. Knotted carbon nanotube fibers and its interfacial properties with epoxy resin.

Author

ZHANG Jie, LI Wenya, XU Anchang, ZHAO Jingna, ZHANG Xiaohua, and LI Qingwen

Subjects
EPOXY resins, INTERFACIAL bonding, SHEAR strength, SURFACE area, SURFACE morphology, STRUCTURAL design
Abstract

Due to the excellent mechanical properties and interface effect of carbon nanotube (CNT) fiber, it is considered to be the high strength fiber in the next generation. The structure- activity relationship between the surface morphology and mechanical properties of carbon nano- tube fibers and the boundary between fiber and epoxy resin were studied. The mechanical properties of CNT fibers with oriented structure and twist structure were analyzed by structural design. Knot method is used to design the knotted fiber, and the influence of kink on the mechanical properties of fibers was analyzed. The strengthening mechanism of kinks on the interfacial bonding between fiber and epoxy resin was discussed by microdrop embedding method. The results show that the mechanical properties of aligned CNT fibers are better than those of twisted CNTs, and the tensile strength of the fiber decreases after knotting. In the aspect of interfacial bonding properties, the interfacial shear strength between fiber and epoxy resin increases from 15 MPa to 35 MPa due to the increase of contact area and surface roughness between CNT fiber and epoxy resin. [ABSTRACT FROM AUTHOR]

Published
2020
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42. Cooperative In Situ Impregnation of PEG and Au Nanoparticles into Expanded CNT Network Toward Composite Phase Change Fibers with High Storage Capacity and Photothermal Conversion.

Author

Liao, Tanqian, Li, Wenya, Zhao, Jingna, Yang, Xiaoyu, Zhang, Wentao, Zou, Jingyun, Zhao, Bing, Zhang, Xiaohua, and Li, Qingwen

Subjects
*PHOTOTHERMAL conversion, *GOLD nanoparticles, *POLYETHYLENE glycol, *PHASE transitions, *FIBERS, *PHASE change materials, *CARBON nanotubes
Abstract

Phase change fibers with multifunctionalities are a promising material for thermal management applications, however, it is still challenging to simultaneously give the fiber high energy conversion and storage capacity. Here, a cooperative in situ impregnation strategy is reported, to introduce Au nanoparticles (NPs) and polyethylene glycol (PEG) together into carbon nanotube (CNT) network during the expansion process, resulting in a CNT/Au/PEG composite phase change fiber. The obtained composite fiber have the characteristics of high loading (up to 88.0–98.6%) and uniform distribution of Au NPs, and thus exhibits superior mechanical, electrical, and thermal properties. The presence of Au NPs plays more important role in not only improving the PEG crystallinity and phase change enthalpy, but also enhancing the photothermal conversion efficiency (up to 88.2%). There is also a new feature of precise regulation of the phase change temperatures, e.g., from 9.5 to 20.5 °C for the solidification temperature. More importantly, due to the strong confinement of PEG and Au NPs inside the CNT network, the composite fiber also shows excellent thermal stabilities, including the anti‐leakage behavior and cycling phase change ability. [ABSTRACT FROM AUTHOR]

Published
2024
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49. Vibration Damping of Carbon Nanotube Assembly Materials.

Author

Zhao, Jingna, Wang, Fulin, Zhang, Xin, Liang, Linjie, Yang, Xueqin, Li, Qingwen, and Zhang, Xiaohua

Subjects
CARBON nanotubes, MECHANICAL behavior of materials, VISCOELASTICITY
Abstract

Vibration reduction is of great importance in various engineering applications, and a material that exhibits good vibration damping along with high strength and modulus has become more and more vital. Owing to the superior mechanical property of carbon nanotube (CNT), new types of vibration damping material can be developed. This paper presents recent advancements, including our progresses, in the development of high‐damping macroscopic CNT assembly materials, such as forests, gels, films, and fibers. In these assemblies, structural deformation of CNTs, zipping and unzipping at CNT connection nodes, strengthening and welding of the nodes, and sliding between CNTs or CNT bundles are playing important roles in determining the viscoelasticity, and elasticity as well. Toward the damping enhancement, strategies for micro‐structure and interface design are also discussed. [ABSTRACT FROM AUTHOR]

Published
2018
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