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Catalytic synthesis of SiC nanowires in an open system
摘要： SiC nanowires (NWs) are usually synthesized in a closed vacuum reaction system which limits the yield of SiC NWs. In this work, SiC NWs and carbon nanotubes were synthesized in an open tube furnace at 1550 ℃ with Si powder as silicon sources, ethanol as carbon sources and ferrocene as catalyst. The as-synthesized products were ultralong β-SiC NWs with the diameter about 80-100 nm and the length up to several tens micrometers. The diameter of the carbon nanotubes was about 20-30 nm. The carbon nanotube yarns about 20 cm in length were obtained at the end of the tube furnace. The growth mechanism of SiC NWs and carbon nanotubes were proposed. Compared with the traditional synthetic techniques in the high vacuum closed system, the novel synthesis method in the open system provided a new approach to the synthesis of SiC NWs.
关键词： Carbon nanotubes,SiC nanowires,Open reaction system,Growth mechanism
更新于2025-09-23 15:22:29
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Magnetic Field Effect of Near-Field Radiative Heat Transfer for SiC Nanowires/Plates
摘要： The SiC micro/nano-scale structure has advantages for enhancing nonreciprocal absorptance for photovoltaic use due to the magneto optical effect. In this work, we demonstrate the near-?eld radiative transfer between two aligned SiC nanowires/plates under different magnetic ?eld intensities, in which Lorentz-Drude equations of the dielectric constant tensor are proposed to describe the dielectric constant as a magnetic ?eld applied on the SiC structure. The magnetic ?eld strength is quali?ed in this study. Using local effective medium theory and the ?uctuation-dissipation theorem, we evaluate the near-?eld radiation between SiC nanowires with different ?lling ratios and gap distances under an external magnetic ?eld. Compared to the near-?eld heat ?ux between two SiC plates, the one between SiC nanowires can be enhanced with magnetic ?eld intensity, a high ?lling ratio, and a small gap distance. The electric ?eld intensity is also presented for understanding light coupling, propagation, and absorption nature of SiC grating under variable incidence angles and magnetic ?eld strengths. This relative study is useful for thermal radiative design in optical instruments.
关键词： near-?eld radiation,SiC nanowires,magnetic ?eld effect
更新于2025-09-11 14:12:44
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Assembly of β-SiC Nanowires film and humidity sensing performance
摘要： β‐SiC materials have been seen as the third‐generation semiconductor widely used in kinds of photoelectric device, high temperature electronics, and other fields. Compared with ordinary semiconductors, β‐SiC materials have huge potential application in replacing monocrystalline silicon in extreme environments because of their numerals extraordinary chemical and physical properties. Based on this, β‐SiC nanowires obviously are more desirable in any way. Here, we present a modified chemical vapor deposition (CVD) method to synthesis β‐SiC nanowires, which needs no protect gas, and transfer it to Si/SiO2 substrates equipped with Au electrodes. The microstructure of the as‐prepared samples is tested by field emission scanning electron microscopy (FESEM). The humidity sensing performance of electronic device is measured by electrochemical workstation test equipment. It shows that the resistance of β‐SiC nanowires increases with increasing environment humidity within very short response/recovery time‐0.5 seconds/0.5 seconds and also performs excellent cycling stability. Such advantage superiorities make it highly possible to apply β‐SiC nanowires into various environments.
关键词： β-SiC nanowires,CVD,electrodes,humidity sensing
更新于2025-09-10 09:29:36
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Heterogeneity governs diameter-dependent toughness and strength in SiC nanowires
摘要： Using a combination of density functional theory and molecular dynamics simulations, this paper reveals the atomistic origin of diameter-dependent extreme mechanical behavior of [111] 3C-SiC nanowires obtained from an energy-based framework. Our results suggest that heterogeneity in atomic stress and variations in diameter-dependent potential-energy density have a profound impact on extreme mechanical properties in the nanowires. The heterogeneity in stress evolves from the nonuniform bond lengths mediated by low coordinated surface atoms—and it penetrates the entire cross section in thinner nanowires and constitutes the atomistic basis for their large reduction in fracture strain, toughness, and strength. Although stress heterogeneity is substantially higher in ultrathin nanowires, its intensity drops and saturates rapidly in larger nanowires following a nonlinear dependence on diameter. The maximum stress heterogeneity in a cross section localizes crack nucleation at the core in ultrathin nanowires but near the surface in larger nanowires. Moreover results show that stiffness, toughness, strength, and fracture strain of the nanowires increase nonlinearly with increasing diameter and saturate at a lower value compared to bulk SiC. In addition to resolving wide discrepancies in the reported values of the ?rst-order elastic modulus in SiC nanowires, the ?ndings highlight heterogeneity as a critical factor for inducing diameter-dependent extreme mechanical behavior in brittle nanowires.
关键词： heterogeneity,atomic stress,strength,toughness,potential-energy density,fracture strain,SiC nanowires,diameter-dependent,mechanical properties
更新于2025-09-09 09:28:46
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Synthesis and characterization of carbon-poor SiC nanowires via vapor-liquid-solid growth mechanism
摘要： Nanowires growth via vapor-liquid-solid mechanism leads to high-quality SiC nanowires. C content is key issue affecting the morphology and composition of SiC nanowires. Here, we report the synthesis and growth mechanism of 3C-SiC nanowires containing reduced amount of C, which are grown on single-crystal Si via pyrolysis of polycarbosilane (PCS) by adjusting pyrolysis temperature and precursor. SiC nanowires have a diameter of 50 nm, while their thickness is 43.75 μm. High-temperature stability of precursors with multiple side-chain groups has an impact on the reaction rate, in result the solid precursor state and pyrolysis temperature at 1350°C are beneficial to the formation of pure carbon-poor SiC nanowires.
关键词： precursor state,vapor-liquid-solid growth mechanism,SiC nanowires,pyrolysis temperature
更新于2025-09-04 15:30:14