A novel method for synthesis of α-Si 3 N 4 nanowires by sol-gel route (original) (raw)
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Synthesis and characterization of Si3N4 wires from binary carbonaceous silica aerogels
Powder Technology, 2014
Silicon nitride ultrafine powders were synthesized from a binary sol-gel route, in which tetraethoxysilane (TEOS) and saccharose were used to prepare a carbonaceous silica xerogel, and ferric nitrate was employed as an additive. The influence of reaction temperature and mass ratio of C to Si (C Si = 0.1, 0.5, 1) on the synthesis of Si 3 N 4 wires was studied. After purification, the Si 3 N 4 sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrum and Fourier transform infrared spectroscopy. The results show that the Si 3 N 4 was fully formed with two kinds of morphologies including globular and wire with a diameter of 100-500 nm and a length of several microns at reaction temperature of 1400°C for 10 h in nitrogen flow (200 ml/min) by employing the mass ratio of C Si = 0.5.
Ceramic Engineering and Science Proceedings, 2007
By varying the final heating temperature in the range 1050°C -1300°C, cubic silicon carbide (P~SiC) and/or trigonal silicon nitride (a-SiaN^ nanowires (NWs) were prepared by direct thermal treatment under nitrogen, of commercial silicon powder and graphite. Long and highly curved p-SiC NWs were preferentially grown below 1200°C, while straight and short a-SiaN4 NWs were formed above 1300°C. Between these two temperatures, a mixture of both nanowires was obtained. The structure and chemical composition of these nanostructures have been investigated by SEM, HRTEM, EDX and EELS.
Synthesis and characterization of silicon carbide, silicon oxynitride and silicon nitride nanowires
World Scientific series in 20th century chemistry, 2003
Several methods have been employed to synthesize SiC nanowires. The methods include heating silica gel or fumed silica with activated carbon in a reducing atmosphere, the carbon particles being produced in situ in one of the methods. The simplest method to obtain b-SiC nanowires involves heating silica gel with activated carbon at 1360 uC in H 2 or NH 3. The same reaction, if carried out in the presence of catalytic iron particles, at 1200 uC gives a-Si 3 N 4 nanowires and Si 2 N 2 O nanowires at 1100 uC. Another method to obtain Si 3 N 4 nanowires is to heat multi-walled carbon nanotubes with silica gel at 1360 uC in an atmosphere of NH 3. In the presence of catalytic Fe particles, this method yields a-Si 3 N 4 nanowires in pure form.
Synthesis of silicon nitride nanowires directly from the silicon substrates
Chemical Physics Letters, 2003
We present a novel method to synthesize high-density silicon nitride nanowires directly from the silicon substrates via a catalytic reaction under ammonia or hydrogen flow at 1200°C. Gallium, gallium nitride, and iron nanoparticles deposited on the silicon substrate were used as catalysts. Gallium nitride can act as a nitrogen source under hydrogen flow. The average diameter of the nanowires is 40 nm and their length is about 300 lm. The silicon nitride nanowires consist of a defect-free single-crystalline a-phase crystal grown with various growth directions.
Applied Physics Letters, 2005
A simple and most promising oxide-assisted catalyst-free method is used to prepare silicon nitride nanowires that give rise to high yield in a short time. After a brief analysis of the state of the art, we reveal the crucial role played by the oxygen partial pressure: when oxygen partial pressure is slightly below the threshold of passive oxidation, a high yield inhibiting the formation of any silica layer covering the nanowires occurs and thanks to the synthesis temperature one can control nanowire dimensions.
Journal of Crystal Growth, 2009
Ordered arrays of high-quality single-crystalline a-Si 3 N 4 nanowires (NWs) have been synthesized via thermal evaporation and detailed characteristics of the NWs have been analyzed by employing scanning electron microscope (SEM) along with energy dispersive spectroscopy (EDS), high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), X-ray photospectroscopy (XPS), infrared (IR), photoluminescence (PL) and in situ I-V measurements by STM/TEM holder. The microscopic results revealed that the NWs having diameter in the range of $30-100 nm and length in microns. Furthermore, the NWs are found to be single crystalline grown along [0 0 1] direction. The elemental composition and valence states of elements are analyzed by EDS and XPS. The room temperature PL spectra exhibit a broad range visible emission band. The electron transport property of a single NW illustrates the symmetric I-V curve of a semiconductor. The possible growth mechanism is also briefly discussed.
Kinetic study of the oxide-assisted catalyst-free synthesis of silicon nitride nanowires
physica status solidi (a), 2006
The synthesis of Si 3 N 4 nanowires from the reaction of silicon nanoparticles with N 2 in the 1200-1440ºC temperature range is reported. The nitridation conditions are such that the reaction with nitrogen is favoured by the presence of silicon oxide in the particles and by the active oxidation of silicon without a catalyst. It is shown that the Si to Si 3 N 4 conversion rate depends on the amount of silicon particles used in the experiments and that, in general, the reaction slows down for greater amounts. This trend is explained by particle stacking, which restricts the exchange of gases between the furnace atmosphere and the atmosphere around the inner particles. In a first stage, local oxygen partial pressure increases around the inner particles and inhibits nitridation locally. If the amount of reactant Si nanoparticles is small enough, this extrinsic effect is avoided and the intrinsic nitridation kinetics can be measured.
Nanotechnology, 2008
Plasma-enhanced low temperature growth (<300 • C) of silicon nanowires (SiNWs) and hierarchical structures via a vapor-liquid-solid (VLS) mechanism are investigated. The SiNWs were grown using tin and indium as catalysts prepared by in situ H 2 plasma reduction of SnO 2 and ITO substrates, respectively. Effective growth of SiNWs at temperatures as low as 240 • C have been achieved, while tin is found to be more ideal than indium in achieving a better size and density control of the SiNWs. Ultra-thin (4-8 nm) silica nanowires, sprouting from the dendritic nucleation patterns on the catalyst's surface, were also observed to form during the cooling process. A kinetic growth model has been proposed to account for their formation mechanism. This hierarchical structure combines the advantages of the size and position controllability from the catalyst-on-top VLS-SiNWs and the ultra-thin size from the catalyst-on-bottom VLS-ScNWs.
One-step synthesis route of the aligned and non-aligned single crystalline α-Si3N4 nanowires
Science in China Series E: Technological Sciences, 2009
This paper reports the bulk synthesis route of the aligned and non-aligned high-quality α-Si 3 N 4 nanowires (NWS) which were grown directly from the Si substrate by vapor phase deposition at 1050℃. The as-grown products were characterized by employing XRD, SEM, HRTEM and photoluminescence. The microscopic results revealed that the products consist of single crystalline aligned and nonaligned α-Si 3 N 4 NWs having a same diameter range of 30-100 nm and different lengths of about hundreds of microns. The XRD observation revealed that the products consist of α-phase Si 3 N 4 NWs. The room temperature PL spectra indicated that the NWs have good emission property. The non-aligned NWs were formed at lower temperature as compared with aligned NWs. Our method is a simple and one-step procedure to synthesize the bulk-quantity and high-purity aligned and non-aligned α-Si 3 N 4 NWs at a relatively low temperature. The possible growth mechanism was also briefly discussed.
Comparison of Silicon Nitride Nanofibers Synthesized Using Silica Nanopowders and Silica Gel
Materials Sciences and Applications, 2012
Nanofibers of alpha silicon nitride were grown by a vapor-solid mechanism at 1450˚C, through the carbothermal reduction process. Two different precursor silica sources were used: silica nanopowders and silica gel. The effect of processing geometry, particularly the stacking orientations of the graphite substrates, silica pellets, and crucibles, on the density of nanofiber growth was also explored. The silicon nitride nanofibers appear with a predominantly rectangular cross section from silica nanopowder precursors and with a circular cross section for silica gel precursors. Silica gel precursors produce nanofiber products that are smaller in cross section but greater in length than the products from silica nanopowder precursors. The processing geometry must be suitably designed such that the vapor-solid mechanism that is responsible for the formation of the nanofibers is not disrupted.