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Dive into the research topics where Yan Ren is active.

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Featured researches published by Yan Ren.


Nano Letters | 2009

High-Strength Composite Fibers: Realizing True Potential of Carbon Nanotubes in Polymer Matrix through Continuous Reticulate Architecture and Molecular Level Couplings

Wenjun Ma; Luqi Liu; Zhong Zhang; Rong Yang; Gang Liu; Taihua Zhang; Xuefeng An; Xiaosu Yi; Yan Ren; Zhiqiang Niu; Jinzhu Li; Haibo Dong; Weiya Zhou; Pulickel M. Ajayan; Sishen Xie

Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks, but their potential has not been fully realized in composite materials due to weakness at the interfaces. Here we demonstrate that through load-transfer-favored three-dimensional architecture and molecular level couplings with polymer chains, true potential of CNTs can be realized in composites as initially envisioned. Composite fibers with reticulate nanotube architectures show order of magnitude improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. The molecular level couplings between nanotubes and polymer chains results in drastic differences in the properties of thermoset and thermoplastic composite fibers, which indicate that conventional macroscopic composite theory fails to explain the overall hybrid behavior at nanoscale.


Advanced Materials | 2009

Monitoring A Micromechanical Process In Macroscale Carbon Nanotube Films And Fibers

Wenjun Ma; Luqi Liu; Rong Yang; Taihua Zhang; Zhong Zhang; Li Song; Yan Ren; Jun Shen; Zhiqiang Niu; Weiya Zhou; Sishen Xie

The evaluation of mechanical properties of carbon nanotube (CNT) fibers is inherently difficult. Here, Raman scattering-a generic methodology independent of mechanical measurements-is used to determine the interbundle strength and microscopic failure process for various CNT macroarchitectures. Raman data are used to predict the moduli of CNT films and fibers, and to illustrate the influences of the twisting geometries on the fibers mechanical performances.


Journal of Materials Chemistry | 2009

Synthesis of large-scale periodic ZnO nanorod arrays and its blue-shift of UV luminescence

Xiaoxian Zhang; Dongfang Liu; Lihuan Zhang; Wenliang Li; Min Gao; Wenjun Ma; Yan Ren; Qingsheng Zeng; Zhiqiang Niu; Weiya Zhou; Sishen Xie

We demonstrate a promising route to fabricate large scale hexagonally patterned, vertically aligned ZnO nanorod arrays with small diameter. By adding 3-mercaptopropyltriethoxysilane (MPTES) molecules as a connection between catalyst and substrate the large size dispersion resulting from the removal of catalyst pattern is avoided, thus the catalyst particle pattern with tiny size dispersion and regular shape is obtained; the size can be tuned in a large range from 50 nm to 300 nm. Using this technique, ZnO nanorod arrays with tunable spacings and diameters are achieved, which also have uniform shape and length, good crystal quality, and vertical alignment on the substrate. Moreover, a pronounced blue-shift of ultraviolet (UV) luminescence spectra of ZnO nanorods with their diameters decreasing is observed. Combining the temperature-dependent photoluminescence (PL), we suggest that a materially decreased exciton-phonon interaction with the reduced diameter of ZnO nanorods is the main reason for the blue-shift of UV luminescence.


Applied Physics Letters | 2008

Temperature dependence of Raman spectra in single-walled carbon nanotube rings

Li Song; Wenjun Ma; Yan Ren; Weiya Zhou; Sishen Xie; Ping-Heng Tan; Lianfeng Sun

The temperature-dependent Raman frequency shift in single-walled carbon nanotube (SWCNT) rings in the range of 80–550K is investigated. We observe that the frequency decreases with increasing temperature for all Raman peaks of the nanotube rings. Furthermore, compared to the nanotubes with linear structure, the temperature coefficients of the radial breathing mode and G-mode frequencies of the nanotube rings are much smaller, which means the nanotube rings have more stable thermal ability. We attribute the better thermal stability to the high bending strain energy along the nanotube rings induced by the sidewall curvature.


Nanoscale | 2011

High performance, freestanding and superthin carbon nanotube/epoxy nanocomposite films

Jinzhu Li; Yun Gao; Wenjun Ma; Luqi Liu; Zhong Zhang; Zhiqiang Niu; Yan Ren; Xiaoxian Zhang; Qingshen Zeng; Haibo Dong; D.X. Zhao; Le Cai; Weiya Zhou; Sishen Xie

We develop a facile, effective and filter free infiltration method to fabricate high performance, freestanding and superthin epoxy nanocomposite films with directly synthesized Sing-Walled Carbon Nanotubes (SWNTs) film as reinforcement skeleton. It is found that the thicknesses of the nanocomposite films can be easily controlled in the range of 0.5-3 μm by dripping target amount of acetone diluted epoxy through the skeleton film. The consequent measurements reveal that the mechanical and electrical properties of SWNTs/epoxy nanocomposite films could be tailored in a quite wide range. For examples, the Youngs modulus of nanocomposite films can be tuned from 10 to 30 GPa, and the electrical conductivity can be ranged from 1000 S·cm(-1) to be insulated. Moreover, high load transfer efficiency in the nanocomposite films is demonstrated by the measured ultrahigh Raman bands shift rate (-30 ± 5 cm(-1)/% strain) under strain. The high effective modulus is derived as 774 ± 70 GPa for SWNTs inside this nanocomposite film.


Nano Letters | 2009

Coulomb explosion: a novel approach to separate single-walled carbon nanotubes from their bundle.

Guangtong Liu; Yuanchun Zhao; Kaihong Zheng; Zheng Liu; Wenjun Ma; Yan Ren; Sishen Xie; Lianfeng Sun

A novel approach based on Coulomb explosion has been developed to separate single-walled carbon nanotubes (SWNTs) from their bundle. With this technique, we can readily separate a bundle of SWNTs into smaller bundles with uniform diameter as well as some individual SWNTs. The separated SWNTs have a typical length of several microns and form a nanotree at one end of the original bundle. More importantly, this separating procedure involves no surfactant and includes only one-step physical process. The separation method offers great conveniences for the subsequent individual SWNT or multiterminal SWNTs device fabrication and their physical properties studies.


Applied Physics Letters | 2007

Secondary growth of small ZnO tripodlike arms on the end of nanowires

Zengxing Zhang; Y. Liu; Dongfang Liu; Shudong Luo; Jun Shen; Lifeng Liu; Wenjun Ma; Yan Ren; Yanjuan Xiang; Weiya Zhou; Sishen Xie; Kaihong Zheng; Yuanchun Zhao; Lianfeng Sun; Chenxia Zou; Dapeng Yu

Small zinc oxide tripodlike arms were assembled at the end of nanowires through thermal evaporation of zinc powder in a horizontal tube furnace. These arms are hundreds of nanometers in length, and they are tens of nanometers in diameter, similar to that of the based nanowires. High-resolution transmission electron microscopy investigation exhibits that they are wurtzite structure and have clear twin planes at the junction of the arms and the based nanowires. The growth mechanism, Raman, and photoluminescence properties were discussed.


Energy and Environmental Science | 2011

Compact-designed supercapacitors using free-standing single-walled carbon nanotube films

Zhiqiang Niu; Weiya Zhou; Jun Chen; Guoxing Feng; Hong Li; Wenjun Ma; Jinzhu Li; Haibo Dong; Yan Ren; D.X. Zhao; Sishen Xie


Nano Letters | 2007

Directly synthesized strong, highly conducting, transparent single-walled carbon nanotube films

Wenjun Ma; Li Song; Rong Yang; Taihua Zhang; Yuanchun Zhao; Lianfeng Sun; Yan Ren; Dongfang Liu; Lifeng Liu; Jun Shen; Zhengxing Zhang; Yanjuan Xiang; Weiya Zhou; Sishen Xie


Journal of Physical Chemistry C | 2008

Highly efficient direct electrodeposition of Co-Cu alloy nanotubes in an anodic alumina template

Lifeng Liu; Weiya Zhou; Sishen Xie; Li Song; Shudong Luo; Dongfang Liu; Jun Shen; Zengxing Zhang; Yanjuan Xiang; Wenjun Ma; Yan Ren; Chaoying Wang; Gang Wang

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Sishen Xie

Chinese Academy of Sciences

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Weiya Zhou

Chinese Academy of Sciences

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Zhiqiang Niu

Nanyang Technological University

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Li Song

University of Science and Technology of China

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Haibo Dong

Chinese Academy of Sciences

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Jinzhu Li

Chinese Academy of Sciences

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Jun Shen

Chinese Academy of Sciences

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Lianfeng Sun

Chinese Academy of Sciences

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Dongfang Liu

Chinese Academy of Sciences

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