Papers by Author: San Qiang Shi

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Authors: Fan Yan Meng, Gui Sheng Wang, San Qiang Shi, Shigenobu Ogata
Abstract: We have developed a theoretical method to obtain a single-walled carbon nanotube (SWCNT) with a high density of topological defects. Carbon nanotubes (CNTs) sustain elastic elongation up to 15-30% at low temperature because of the sufficiently high barrier of bond rotations. A large number of topological defects are activated simultaneously and widely distributed over the entire tube wall after heating the stretched tube to an elevated temperature. This is driven by the internal energy of the strained carbon nanotubes. The manner in which topological defects are distributed is affected by the initial strain and the heating temperature. Nanotubes with a large number of topological defects achieve the elongation without breaking.
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Authors: Ka Keung Wong, San Qiang Shi, Alan Kin Tak Lau
Abstract: Although many studies have been conducted in the past few years on the possibility of using carbon nanotube (CNT) to improve the performance of polymer-based materials, some of the results were contradictory and lack of coherence. Thus, the in-depth understanding of CNT composites is required. In this paper, single-walled carbon nanotubes (SWNTs), which were functionalized by sonicating with nitric and sulfuric acids, will be used to fabricate a SWNT/epoxy composite. There are two reasons for functionalizing the SWNTs, they are (i) to improve the dispersion of the SWNTs in polymer, and (ii) to improve the interfacial bonding properties between the SWNTs and polymer matrix. Tensile property test and micro-hardness test will be carried out to examine the mechanical properties of the composites with different SWNT contents. Thermogravimetry Analysis (TGA) will be used to evaluate the thermal properties of the composites. Scanning Electron Microscope (SEM) will also be used to investigate the failure mechanism of the composites after tensile test. A comparison of the composites with functionalized and non-functionalized SWNTs will be given to elaborate the effect of nanotube functionalization.
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Authors: Yang Bai, Kai Ding, Guang Ping Zheng, San Qiang Shi, Lie Jie Qiao, Dong Guo
Abstract: We demonstrated the superior electrocaloric effect (ECE) in BaTiO3 multilayer structure. The sample fabricated by tape-casting process has 120 effective ferroelectric layers with average layer thickness of 1.7 μm. The ferroelectric hysteresis loops were measured in the temperature range from 30 to 180 oC, and then the temperature dependences of ECE adiabatic temperature change and heat absorption were obtained according to Maxwell relation. A peak ECE adiabatic temperature change of 0.027 K/V and heat absorption of 0.36 J/g were observed near the ferroelectric phase transition at 125 oC under Vmax=25 V. The BaTiO3 thick film can sustain an external electric field (>500 kV/cm) several times higher than bulk ferroelectric ceramics (~30 kV/cm). Although the EC coefficient of BaTiO3 is much lower than lead-based ferroelectric ceramics, the ultrahigh working electric field endows it a large ECE, higher than that of most reported lead-based ferroelectric ceramics. In addition, the lead-free composition provides it a promising future in solid-state cooling technology.
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