A study on the growth enhancement effects of chlorine on carbon nanotube forest in chloride-mediated chemical vapor deposition

autho

Effect of Annealing and Diameter on Tensile Property of Spinnable Carbon Nanotube and Unidirectional Carbon Nanotube Reinforced Epoxy Composite

publishe

Evaluation of the effect of diameter of multi-walled carbon nanotube on the tensile strength by using sonication-induced fragmentation

出版者版タイトル：Evaluation of the effect of diameter of multi-walled carbon nanotube on the tensile strength using sonication-induced fragmentationautho

Effect of Annealing and Diameter on Tensile Property of Spinnable Carbon Nanotube and Unidirectional Carbon Nanotube Reinforced Epoxy Composite

Carbon nanotubes (CNTs) are thought to have higher elastic modulus and strength than carbon fibers. The recent development of spinnable multi-walled carbon nanotubes (MWNTs) enables us to produce unidirectional MWNT reinforced polymer-based composites with a higher volume fraction of CNTs. The results of tensile tests of spinnable MWNTs in scanning electron microscopes show, however, that Young’s modulus and tensile strength of MWNTs are not as high as expected. Annealing and developing thinner spinnable MWNTs will be the solution to improving the tensile property. In this study, as-produced and annealed untwisted yarns composed of MWNTs with three different diameters were prepared, and the tensile properties of spinnable MWNTs were estimated from the tensile properties of the untwisted yarns to investigate the effect of annealing and diameter on the overall tensile property of MWNTs. Furthermore, tensile tests of unidirectional MWNT reinforced epoxy composites were conducted and the contribution of the tensile property of MWNTs to the bulk tensile property of the composite was discussed. As a result, it was found that MWNTs with thinner diameters had higher Young’s modulus and tensile strength and annealing improved Young’s modulus of MWNTs, in addition to that the bulk tensile property of unidirectional MWNT reinforced epoxy composites was primarily determined by the tensile property of MWNTs. The results support previous findings from a limited number of tensile tests in SEM/TEM, and also reveal the validity of estimating the tensile properties of individual CNTs by tensile testing of untwisted yarns. In addition, the discussion on composite materials suggests that the tensile property of composite materials can be enhanced by improving the tensile property of MWNTs

Evaluation of the effect of diameter of multi-walled carbon nanotube on the tensile strength by using sonication-induced fragmentation

出版者版タイトル：Evaluation of the effect of diameter of multi-walled carbon nanotube on the tensile strength using sonication-induced fragmentationautho

Semimetallic properties of SnTe/PbSe type-II superlattices

AbstractWe prepared the SnTe/PbSe superlattices, and measured electrical and optical properties at room temperature. The superlattice showed semimetallic properties resulting from type-II band offset between SnTe and PbSe. Though nondope SnTe had hole concentration around 3×1020 cm−3, nondope SnTe/PbSe superlattices with thin SnTe layers showed n-type conduction with carrier concentrations less than 2×1018 cm−3 and carrier mobility comparable or higher than that of PbSe, keeping semimetallic properties in the optical transmission spectra. These properties are discussed with the band offset of SnTe/PbSe heterojunction

Property improvement of CNT spun yarns and their composites through pressing, stretching and tensioning

Untwisted multi-walled carbon nanotube (CNT) yarn was spun from vertically aligned CNT arrays by solid-state drawing CNT webs through a ceramic die. CNT yarn-reinforced epoxy composites were developed using a resin drop method. Waviness and poor packing of CNTs in the untwisted spun yarns have limited the mechanical properties of the yarns and their composites. Therefore, pressing along with sliding was applied to create thin-twisted yarns with dense packing of the CNTs. Besides, stretching and tensioning techniques were applied to the twisted yarns to reduce twist angle as well as waviness of the CNTs and their bundles. Stretching and tensioning of the press-slid yarns under constant loads of 0.15, 0.25, 0.35 N enhanced the mechanical properties of the yarns significantly. Moreover, stretching and tensioning of the press-slid CNT yarns increased the mechanical properties of the yarn composites considerably. However, tensioning of the press-slid yarns is more effective than their stretching