High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for...High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.展开更多
Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon ...Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon molecular sieve(CMS) membranes with ultrahigh permselectivity for hydrogen purification were fabricated by high-temperature(700–900 ℃) pyrolysis of polymeric precursor of phenolphthaleinbased cardo poly(arylene ether ketone)(PEK-C). The evolution of the microstructural texture and ultramicroporous structure and gas separation performance of the CMS membrane were characterized via TG-MS, FT-IR, XRD, TEM, CO2 sorption analysis and gas permeation measurements. CMS membranes prepared at 700 ℃ exhibited amorphous turbostratic carbon structures and high H2 permeability of 5260 Barrer with H2/CH4, H2/N2 and H2/CO selectivities of 311, 142, 75, respectively. When carbonized at900 ℃, the CMS membrane with ultrahigh H2/CH4 selectivity of 1859 was derived owing to the formation of the dense and ordered carbon structure. CMS membranes with ultrahigh permselectivity exhibit an attractive application prospect in hydrogen purification.展开更多
With recent improvements in carbon nanotube separation methods, the accurate determination of residual metallic carbon nanotubes in a purified nanotube sample is important, particularly for those interested in using s...With recent improvements in carbon nanotube separation methods, the accurate determination of residual metallic carbon nanotubes in a purified nanotube sample is important, particularly for those interested in using semiconducting single-walled carbon nanotubes （SWCNTs） in electronic device applications such as thin-film transistors （TFTs）. This work demonstrates that Raman microscopy mapping is a powerful characterization tool for quantifying residual metallic carbon nanotubes present in highly enriched semiconducting nanotube networks. Raman mapping correlates well with absorption spectroscopy, yet it provides greater differentiation in purity. Electrical data from TFTs with channel lengths of 2.5 and 5μ m demonstrate the utility of the method. By comparing samples with nominal purities of 99.0% and 99.8%, a clear differentiation can be made when evaluating the current on/off ratio as a function of channel length, and thus the Raman mapping method provides a means to guide device fabrication by correlating SWCNT network density and purity with TFT channel scaling.展开更多
Due to its remarkable electrical and optical capabilities,optoelectronic devices based on the semiconducting single-walled carbon nanotube(s-SWCNT)have been studied extensively in the last two decades.First,s-SWCNT is...Due to its remarkable electrical and optical capabilities,optoelectronic devices based on the semiconducting single-walled carbon nanotube(s-SWCNT)have been studied extensively in the last two decades.First,s-SWCNT is a direct bandgap semiconductor with a high infrared absorption coefficient and high electron/hole mobility.In addition,as a typical one-dimensional material,there is no lattice mismatch between s-SWCNT and any substrates.Another advantage is that the optoelectronic devices of s-SWCNT can be processed at low temperatures.s-SWCNT has intriguing potential and applications in solar cells,light-emitting diodes(LEDs),photodetectors,and three-dimensional(3D)optoelectronic integration.In recent years,along with the advancement of solution purification technology,the high-purity s-SWCNTs film has laid the foundation for constructing large-area,homogenous,and high-performance optoelectronic devices.In this review,optoelectronic devices based on s-SWCNTs film and related topics are reviewed,including the preparation of high purity s-SWCNTs film,the progress of photodetectors based on the s-SWCNTs film,and challenges of s-SWCNTs film photodetectors.展开更多
Semiconducting single-walled carbon nanotubes (s-SWCNTs) are the foundation of CNT-based electronics and optoelectronics. For practical applications, s-SWCNTs should be produced with high purity, high structural quali...Semiconducting single-walled carbon nanotubes (s-SWCNTs) are the foundation of CNT-based electronics and optoelectronics. For practical applications, s-SWCNTs should be produced with high purity, high structural quality, low cost, and high yield. Currently conjugated polymer wrapping method shows great potential to fulfill these requirements due to its advantages of simple operation process, high purity separation, and easy scaling-up. However, only a small portion of both CNTs and polymers go into the final solution, and most of them are discarded after a single use, resulting in high cost and low yield. In this paper, we introduce a closed-loop recycling strategy, in which raw materials (CNTs and polymers) and solvents were all recycled and reused for multiple separation cycles. In each cycle, high-purity (> 99.9%) s-SWCNTs were obtained with no significant change of structural quality. After 7 times of recycling and separation, the material cost was reduced to ∼ 1% in comparison with commercially available products, and total yield was increased to 36% in comparison with 2%–5% for single cycle separation. Our proposed closed-loop recycling strategy paves the way for low-cost and high-yield mass production of high-quality s-SWCNTs.展开更多
文摘High purity silicon carbide （SIC） powder was synthesized in-situ by chemical reaction between silicon and carbon powder. In order to ensure that the impurity concentration of the resulting SiC powder is suitable for high-resistivity SiC single crystal growth, the preparation technology of SiC powder is different from that of SiC ceramic. The influence of the shape and size of carbon particles on the morphology and phase composition of the obtained SiC powder were discussed. The phase composition and morphology of the products were investigated by X-ray diffraction, Raman microspectroscopy and scanning electron microscopy. The results show that the composition of resulting SiC by in-situ synthesis from Si/C mixture strongly depends on the nature of the carbon source, which corresponds to the particle size and shape, as well as the preparation temperature. In the experimental conditions, flake graphite is more suitable for the synthesis of SiC powder than activated carbon because of its relatively smaller particle size and flake shape, which make the conversion more complete. The major phase composition of the full conversion products is β-SiC, with traces of α-SiC. Glow discharge mass spectroscopy measurements indicated that SiC powder synthesized with this chemical reaction method can meet the purity demand for the growth of high-resistivity SiC single crystals.
基金the National Key R&D Program of China(2017YFB0603403)National Natural Science Foundation of China(21676044,21878033,21978034)+1 种基金High Level Innovation Team of Liaoning Province(XLYC1908033)Fundamental Research Funds for the Central Universities(DUT19ZD211,DUT 2018TB02)for the financial support。
文摘Hydrogen is a green clean fuel and chemical feedstock. Its separation and purification from hydrogencontaining mixtures is the key step in the production of hydrogen with high purity(>99.99%). In this work, carbon molecular sieve(CMS) membranes with ultrahigh permselectivity for hydrogen purification were fabricated by high-temperature(700–900 ℃) pyrolysis of polymeric precursor of phenolphthaleinbased cardo poly(arylene ether ketone)(PEK-C). The evolution of the microstructural texture and ultramicroporous structure and gas separation performance of the CMS membrane were characterized via TG-MS, FT-IR, XRD, TEM, CO2 sorption analysis and gas permeation measurements. CMS membranes prepared at 700 ℃ exhibited amorphous turbostratic carbon structures and high H2 permeability of 5260 Barrer with H2/CH4, H2/N2 and H2/CO selectivities of 311, 142, 75, respectively. When carbonized at900 ℃, the CMS membrane with ultrahigh H2/CH4 selectivity of 1859 was derived owing to the formation of the dense and ordered carbon structure. CMS membranes with ultrahigh permselectivity exhibit an attractive application prospect in hydrogen purification.
文摘With recent improvements in carbon nanotube separation methods, the accurate determination of residual metallic carbon nanotubes in a purified nanotube sample is important, particularly for those interested in using semiconducting single-walled carbon nanotubes （SWCNTs） in electronic device applications such as thin-film transistors （TFTs）. This work demonstrates that Raman microscopy mapping is a powerful characterization tool for quantifying residual metallic carbon nanotubes present in highly enriched semiconducting nanotube networks. Raman mapping correlates well with absorption spectroscopy, yet it provides greater differentiation in purity. Electrical data from TFTs with channel lengths of 2.5 and 5μ m demonstrate the utility of the method. By comparing samples with nominal purities of 99.0% and 99.8%, a clear differentiation can be made when evaluating the current on/off ratio as a function of channel length, and thus the Raman mapping method provides a means to guide device fabrication by correlating SWCNT network density and purity with TFT channel scaling.
基金This work was supported by the National Key Research&Development Program(No.2020YFA0714703)National Science Foundation of China(Nos.62071008 and U21A6004)Ji Hua Laboratory(No.2021B0301030003).
文摘Due to its remarkable electrical and optical capabilities,optoelectronic devices based on the semiconducting single-walled carbon nanotube(s-SWCNT)have been studied extensively in the last two decades.First,s-SWCNT is a direct bandgap semiconductor with a high infrared absorption coefficient and high electron/hole mobility.In addition,as a typical one-dimensional material,there is no lattice mismatch between s-SWCNT and any substrates.Another advantage is that the optoelectronic devices of s-SWCNT can be processed at low temperatures.s-SWCNT has intriguing potential and applications in solar cells,light-emitting diodes(LEDs),photodetectors,and three-dimensional(3D)optoelectronic integration.In recent years,along with the advancement of solution purification technology,the high-purity s-SWCNTs film has laid the foundation for constructing large-area,homogenous,and high-performance optoelectronic devices.In this review,optoelectronic devices based on s-SWCNTs film and related topics are reviewed,including the preparation of high purity s-SWCNTs film,the progress of photodetectors based on the s-SWCNTs film,and challenges of s-SWCNTs film photodetectors.
基金This work was supported by the National Key Research and Development Program(No.2016YFA0201902)the National Natural Science Foundation of China(No.51991341)+1 种基金Young Talents Program of Beijing(No.2018000020028G349)the Open Research Fund of Key Laboratory of Space Utilization,Chinese Academy of Sciences(No.LSU-KFJJ-2020-06).
文摘Semiconducting single-walled carbon nanotubes (s-SWCNTs) are the foundation of CNT-based electronics and optoelectronics. For practical applications, s-SWCNTs should be produced with high purity, high structural quality, low cost, and high yield. Currently conjugated polymer wrapping method shows great potential to fulfill these requirements due to its advantages of simple operation process, high purity separation, and easy scaling-up. However, only a small portion of both CNTs and polymers go into the final solution, and most of them are discarded after a single use, resulting in high cost and low yield. In this paper, we introduce a closed-loop recycling strategy, in which raw materials (CNTs and polymers) and solvents were all recycled and reused for multiple separation cycles. In each cycle, high-purity (> 99.9%) s-SWCNTs were obtained with no significant change of structural quality. After 7 times of recycling and separation, the material cost was reduced to ∼ 1% in comparison with commercially available products, and total yield was increased to 36% in comparison with 2%–5% for single cycle separation. Our proposed closed-loop recycling strategy paves the way for low-cost and high-yield mass production of high-quality s-SWCNTs.
