Synthesis Of SiC Nanowires Research Articles

Synthesis of SiC nanowires from retired wind turbine blades and their microwave-absorbing property

Retired wind turbine blades (RWTBs) mainly consist of glass fibers and resins, which have abundant of carbon and silicon resources. This study synthesized SiC nanowires (SiC NWs) by using the RWTBs for the first time. The RWTBs were grinded into powders and pyrolyzed at 600 °C for 2 h, the pyrolysis solid residues (P-RWTBs) mixed with apricot shell char (ASC) and silicon powder in a stoichiometric ratio (C/Si = 4), and then the mixture calcined at 1550 °C for 4 h in an argon atmosphere. XRD, FTIR and XPS results indicating that SiC NWs had been successfully synthesized. SEM and TEM micrographs show that the produced SiC NWs exhibit a worm-like shape, with diameters of 50–100 nm, and interweave into a 3D network body. The minimum reflection loss (RLmin) of the SiC NWs 3D network body reached −18.17 dB at the thickness of 4.8 mm, which meet the requirements of microwave-absorbing materials. Its good microwave-absorption property is due to the various loss types of the electromagnetic waves that caused by the special structure. This study provides a new approach for high-value utilization of the RWTBs, which is of great significance in realizing the "green retirement" of glass fiber reinforced polymers.

Synthesis of SiC nanowires on biochar surfaces by a simple direct method

Demand for air filters is crucially required due to PM 2.5. So, SiC nanowire networks are directly grown on biochar surfaces that serve strength and filtering purposes. The nanowires were prepared by spraying silicon powder on Lesser bulrush and Grey sedge biochars which acted as carbon sources and heating up to 1300℃ to 1500℃ for 1 h in Ar atmosphere. As a result, silicon powder evaporated and diffused on biochar surfaces. Meanwhile, CO vapor was generated from biochar reacted with O2 in the chamber. The evaporated silicon reacted with both C(s) and CO(g) to form cubic SiC nanowires. At the early stage of the reaction, large nuclei of SiC nanowires were formed at 1300℃. Those nuclei became smaller to promote nanowires when a higher temperature was applied before being disappeared at 1500℃. At such temperature, the obtained network structure SiC nanowires with 10 nm to 30 nm diameters on the outer and inner surfaces of biochars were completed, facilitating superior strength and filtering purposes. Comparatively, the Lesser bulrush provided higher strength than those of the Grey sedge ones, thus it was selected for the filtering efficiency test. The results showed that particulate filter efficiency was up to 97% but it was still over the range of pressure drop at 30 in H2O.

Ultra-fine beta SiC nanowires Isothermally converted from high activated silica by Carbothermic Reduction and Carburization at low temperature

This work was focused primarily on the investigation of the parameters effecting the formation of β-SiC and their crystallite diameter. Previous works revealed that the preparation of silica used as a precursor was the key factor on the resulting particle features. Therefore, the work aimed to achieve obtaining ultrafine silica precursor with superfine crystallites at relatively low temperatures. In the result, a clear difference was observed between the finally obtained SiC powders in terms of conversion and particle morphology according to the preparation process. The use of a modified high energy ball milling system resulted in a considerable reduction in the size of the starting particle's diameter (>100 nm). The FTIR transmission spectra of the yielded nanowires confirmed the SiC composition with the peak near 950 cm−1, which represents the LO stretching Si–C bond. The precursor preparation process improved the efficiency of Carbothermic Reduction and Carburization process used in the synthesis of SiC nanowires. The XRD findings indicated that all the precursors consisted of only amorphous silica, and the modified high energy ball milling system thermodynamically supported the crystal to amorphous conversion. The SEM micrographs revealed that the SiC nanowires had diameters of 50–100 nm with hundreds of microns in length. The SiC nanowire composed of ultrafine crystalline cubic SiC in beta form. As a result, the silica conversion to silicon carbide was successfully completed at a faster reduction rate and relative lower temperature (1475 °C for 4 h).

Synthesis of SiC Nanowires via Controllable Anodic Etching Time

Porous SiC (PSC) was successfully synthesized via UV-assisted pulsed current anodic etching of hexagonal n-type silicon carbide (6H–SiC) substrate using different etching times. The micromorphological and structural characterizations of PSC were reported. Field-emission scanning electron microscopy (FESEM) results established that the etching time can be considered as a significant etching parameter that controls the micromorphology aspects of the porous SiC specimens. Furthermore, the adjustment of etching time can convert SiC pores into nanowire structures. Raman spectroscopy characterization was performed as well, where the shape of the Raman spectra was analyzed, in precise the transverse optical E1 (TO) and the longitudinal optical A1 (LO) peaks, which correlate powerfully with the porous SiC micromorphology. This simplistic synthesis may be considered as a potential and affordable technique to synthesize SiC nanowires for extensive applications.

Synthesis of SiC nanowires by a simple chemical vapour deposition route in the presence of ZrB2

The SiC nanowires (NWs) were fabricated by a simple chemical vapour deposition (CVD) method at high temperature using Si, phenolic resin, and ZrB2 powder. The morphologies of the fabricated SiC NWs included SiC/SiO2 chain-beads and straight wires with core-shell structures. The fabricated SiC NWs were micrometre-to-millimetre in length, with chains 100–300 nm in diameter and beads with diameters of less than 1 μm. The core-shell-structured SiC NWs consisted of crystalline SiC cores and thin amorphous SiO2 shells. SiC crystals grew in the [111] direction governed by a vapour-solid (VS) mechanism. The added ZrB2 promotes the generation of gaseous species at higher gas pressures, which contributes to the formation of SiC NWs by CVD. The fabricated SiC NWs exhibited good photoluminescence properties due to many stacking faults and the presence of amorphous SiO2.

Controlling the catalytic synthesis of SiC nanowires, carbon nanotubes, and graphene from a multilayer film precursor

A simple and effective strategy is introduced for the direct growth of SiC nanowires, carbon nanotubes (CNTs), and graphene on target substrates via a solid-state process based on the use of a solid amorphous carbon source. The desired products were synthesized in large quantities via the thermal treatment of laminated sandwich film precursors at 900 °C under a protective Ar atmosphere. The growth mechanisms and evolution models of the SiC nanowires, CNTs, and graphene were studied in detail and were proposed to be a combination of a dissolution–precipitation process and a confined reaction from a laminated sandwich film precursor. The combination of this fabrication process (which also enables the simultaneous patterning of the proposed nanostructures) with the inherent properties of SiC nanowires, CNTs, and graphene therefore represents significant progress in the functional patterning of nanomaterials for use in a range of potential applications.

In situ synthesis of SiC nanowire porous layer on carbon/carbon composites

AbstractSiC nanowire porous layer was synthesized in situ by a simple two‐step technique involving slurry painting and high temperature heat‐treatment without catalyst assist. The proposed method is effective and low‐cost, which can prepare plentiful and high‐purity SiC nanowires (SiCNWs). The microstructure of SiCNWs and the effects of heat‐treatment temperatures on the synthesis of SiCNWs were investigated in detail. Results show that the as‐synthesized NWs consisted of 3C–SiC, with the length of up to several hundred micrometers and the diameter of 50‐100 nm at 1500°C. Meanwhile, the diameter of SiCNW increases with the increasing of heat‐treatment temperature. The growth process of the SiCNWs can be controlled by the vapor‐solid growth mechanism. After introducing SiCNWs into the SiC coating prepared by pack cementation, the elastic modulus of the nanowire‐toughened SiC coating was increased by 35% compared to SiC coating without SiCNWs.

Synthesis of SiC nanowires via catalyst-free pyrolysis of silicon-containing carbon materials derived from a hybrid precursor

SiC nanowires were successfully synthesized without catalyst by pyrolysis of silicon-containing pitch-derived carbon materials in a closed graphite crucible. These silicon-containing carbon materials were obtained by homogenization and co-carbonization of a hybrid precursor consisting of the toluene soluble fraction of coal tar pitch with polycarbosilane (PCS). The composition, morphology and structure of the nanowires were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The influence of pyrolysis temperature on the growth of the nanowires was investigated by Fourier transform infrared spectroscopy (FTIR) and thermo-gravimetry coupled with mass spectroscopy (TG-MS) analysis. The results indicate that the growth of the SiC nanowires starts at around 1200 °C. As the pyrolysis temperature increases to 1300–1500 °C, a large quantity of nanowires are formed on the top surface of the pitch-derived carbon substrate. In addition, increasing the pyrolysis temperature leads to an increase in the average diameter and a change in the typical morphology produced. The synthesized SiC nanowires have single-crystalline structure and are grown along the [111] direction with numerous stacking faults and twins. The vapor-solid (VS) mechanism may be responsible for the growth process of the SiC nanowires.

SiC NWs Grown on Silicon Substrate Using Fe as Catalyst

We report on the synthesis of SiC nanowires (NWs) using iron as catalyst. The NWs were grown on silicon substrate by vapour-liquid-solid (VLS) mechanism with propane and silane as precursors, both 3% diluted in hydrogen, and hydrogen as carrier gas. The growth temperature was 1250°C, to reach the eutectic values of the Si-Fe alloy and to permit the VLS mechanism. The as-grown SiC nanowires were characterized by scanning and transmission electron microscopy. The nanowires are from 30 to 100 nm in diameter and several μm in length, with <111> growth direction.

Novel synthesis and characterization of silicon carbide nanowires on graphite flakes

Silicon carbide nanowires were synthesized on the surface of graphite by partially reacting with silicon powders in NaF–NaCl based salt at 1150–1400°C in argon. The effects of temperature and time of heat treatment as well as Si/graphite ratio on synthesis of SiC nanowires were studied. The results showed that the formation of SiC nanowires started at about 1200°C, and the amounts of SiC nanowires increased in the resultant powders with increasing temperature. Their morphologies were characterized by scanning electron microscopy and high-resolution transmission electron microscopy. It was found that β-SiC nanowires with diameter of 10–50nm and various lengths grew along their preferred direction perpendicular to (111). The zeta potential of graphite was also increased after coating with silicon carbide nanowires. SiC nanowires that formed on the graphite surface acted as an anti-oxidant to a certain extent, and they protected the inner graphite from oxidation.

Large‐scale synthesis of SiC nanowires from polysiloxane and wood powder composites

AbstractLarge‐scale SiC nanowires were prepared by directly annealing polysiloxane and wood powder composites without catalyst assistant at 1420 °C under argon atmosphere. SiC nanowires are up to tens of micrometers in length and the diameters are in the range of 30–150 nm. Most nanowires are smooth and straight in morphology. High‐resolution TEM image shows that SiC nanowires grow along the [111] direction. The vapor–solid mechanism was proposed to explain the growth procedure of SiC nanowires. The present work provides an efficient and simple strategy for large‐scale production of SiC nanowires.

Synthesis of SiC nanowires by thermal evaporation method without catalyst assistant

In this paper, SiC nanowires were successfully synthesized on Si substrate by the thermal evaporation method without the assistance of a metal catalyst. The phase composition, morphology and microstructure of the SiC–SiO2 core–shell nanowires were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The SiC nanowires produced grew along the [111] direction and had diameters of 50–100nm with lengths of several hundreds of microns. The SiC nanowire was composed of a single-crystalline SiC core with a thin amorphous SiO2 shell. The growth mechanism of the nanowires can be explained by the vapor–solid (VS) process.

Morphology-Controlled Synthesis of SiC Nanowires by Catalyst-Assisted Pyrolysis of Polymeric Precursor

Two different types of morphology are observed in synthesis of SiC nanowires by catalyst-assisted pyrolysis of polymeric precursor while Au acts as the catalyst. Both two types of SiC nanowires are well oriented and uniform in diameter. The results indicate that longer (~20 μm) and slimmer (~100 nm) nanowires are tends to be produced in high temperature (1450°C), while shorter (~10 μm) and thicker (200~300 nm) ones are tends to be produced in low temperature (1420°C). Then we make a discussion on the mechanism of the growth of SiC nanowires based on the VLS (Vapor-Liquid-Solid) process.

Synthesis of SiC nanowires and nanotubes sheathed with BN

SiC nanowires and nanotubes sheathed with BN were synthesized by annealing C-SiC and SiC nanotubes at 1600 °C for 5 h with BN powder in Ar gas. According to TEM observation, the BN coating was very thin and the layer number of BN coating was less than 15. The BN coating on the surface of SiC nanotubes was not produced by the heat treatment at 1500 °C. This result revealed that BN on the surface of SiC nanomaterials was produced by heat treatment of higher than 1600 °C.

Synthesis of SiC Nanowires with Silica Sol and Carbon Black

Nanometer-sized β-SiC were synthesized by carbothermal reduction of silica sol with acetylene carbon black at 1600 °C for 2h. Three kinds (straight, bamboo-like, branch-like) of SiC nanowires were deposited on the graphite plate, while SiC particle agglomerates and nanowires were formed in the graphite crucible. All the nanowires were formed via VS mechanism through the reaction between gaseous SiO and CO produced from the process of carbothermal reduction.

Growth of Ultra-High Density 3C-SiC Nanowires via Single Source CVD

ABSTRACTSilicon carbide (SiC) nanostructures attract interest due to their applications in optoelectronic devices, sensors, and high-power/high temperature electronics. The synthesis of SiC nanowires by chemical vapor deposition using hexamethyldisilane (HMDS) as a source material on SiO2/Si substrate has been investigated. Various catalyst materials, including iron (film and nanoparticles), nickel (film and nanoparticles), and cobalt nanoparticles have been used. The growth runs have been carried out at temperatures between 900 and 1100°C under H2 as carrier gas. 3C-SiC nanowires have successfully been grown at even lower temperatures despite the lower efficiency of source decomposition at low temperatures. The SiC nanowire diameters are in the range of 8 nm to 60 nm, as determined by transmission electron microscopy (TEM). In general, the efficiency of nanowire growth has increased with temperature except the growth on Ni film, which has occasionally resulted in SiC flowers. Higher nanowire density at high temperatures can be attributed to more efficient decomposition of the source at higher temperatures. Further, optical properties of the nanowires have been studied by Fourier transform infrared spectroscopy (FTIR). The fabricated nanowires have also been characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray diffraction (XRD).

Synthesis of SiC nanowires from gaseous SiO and pyrolyzed bamboo slices

Bamboo slices have been pyrolyzed by heat treatment in an inert atmosphere at 1000°C. The reaction of gaseous SiO and pyrolyzed bamboo slices at 1300°C resulted in the formation of SiC nanowires. Microstructure characterization of the SiC nanowires was carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). XRD analysis showed that the reaction product is crystalline β-SiC. The diameter and the length of the SiC nanowires is ranging from 20∼70nm to 10∼20μm. Most of the SiC nanowires possess straight and smooth morphology. SiC nanowires have a preferential growth axis parallel to the [111] direction.

Synthesis of SiC nanowires through reaction between Si nanopowders and CH4 gas

Synthesis of SiC nanowires through reaction between Si nanopowders and CH4 gas