3C-SiC Powders Research Articles

Size-dependent electromagnetic wave absorption of 3C–SiC particles

1. The reaction pathways for synthesizing micrometer-scale 3C–SiC powders under an N2 atmosphere. 2. The electromagnetic wave absorption mechanism of 3C–SiC powders.

Preparation of SiC/multilayer graphene composite ceramic with improved properties catalyzed by Ni nanoparticle

The 3C–SiC powder or the 3C–SiC/multilayer graphene composite powder was synthesized after 3 h carbothermal reduction reaction in flowing Ar at 1673 K using expanded graphite and Tetraethyl orthosilicate (TEOS) as raw materials and Ni(NO3)2·6H2O as catalyst precursor. Based on these findings, 3C–SiC/multilayer graphene composite ceramics were prepared using a one-step spark plasma sintering(SPS) method. The results showed that the reaction temperature could be reduced to 1673 K when adding 1 wt.% Ni. Furthermore, the thickness of the multilayer graphene generated in situ was approximately 3.5 nm with C/SiO2 molar ratio of 3.5:1. In addition, the water wettability of the 3C–SiC/multilayer graphene composite powders was significantly improved. Furthermore, the hardness of the 3C–SiC/multilayer graphene composite ceramic prepared by the addition of Ni catalyst was enhanced compared to the situation without any catalyst and there was no obvious agglomeration in the ceramic structure. The method of in situ ceramic phase dispersing graphene could solve the agglomeration and high costs of preparation and extended to develop a wide range of applications of graphene.

Investigation of the formation of defects under fast neutrons and gamma irradiation in 3C–SiC nano powder

In this work cubic phase, silicon carbide nano-powders were irradiated at the high-flux pulsed reactor IBR–2 (Dubna, Russia). The 3C–SiC powder was irradiated with neutron doses up to 1015 n/cm2. The irradiated samples were then analyzed using X-ray diffraction, Raman spectroscopy, Positron annihilation spectroscopy, and Fourier Transform Infrared Spectroscopy. The XRD analysis showed a slight decrease in the lattice parameters with the increase in neutron fluences. The results obtained from positron annihilation measurements were compared to the theoretical calculations, to recognizing the type of structural defect in the samples. A positron lifetime component 355 ps associated with the calculated values for clusters containing of 13–21 vacancies was identified. The concentration of these defects was estimated to be in the region of 5 ppm, and was very similar to the one identified on the unirradiated sample. The results also indicate high irradiation resistivity of the 3C–SiC after irradiation.

Highly Selective Photocatalytic CO2 Reduction to CH4 by Ball-Milled Cubic Silicon Carbide Nanoparticles under Visible-Light Irradiation.

The ultimate goal of photocatalytic CO2 reduction is to achieve high selectivity for a single product with high efficiency. One of the most significant challenges is that expensive catalysts prepared through complex processes are usually used. Herein, gram-scale cubic silicon carbide (3C-SiC) nanoparticles are prepared through a top-down ball-milling approach from low-priced 3C-SiC powders. This facile mechanical milling strategy ensures large-scale production of 3C-SiC nanoparticles with an amorphous silicon oxide (SiOx) shell and simultaneously induces abundant surface states. The surface states are demonstrated to trap the photogenerated carriers, thus remarkably enhancing the charge separation, while the thin SiOx shell prevents 3C-SiC from corrosion under visible light. The unique electronic structure of 3C-SiC tackles the challenge associated with low selectivity of photocatalytic CO2 reduction to C1 compounds. In conjugation with efficient water oxidation, 3C-SiC nanoparticles can reduce CO2 into CH4 with selectivity over 90%.

Synthesis and Characterization of N-Doped SiC Powder with Enhanced Photocatalytic and Photoelectrochemical Performance

Solar-light-driven N-doped 3C–SiC powder was synthesized via a simple one-step combustion route. SiC–N2 photocatalysts exhibited 205.3 μL/(g·h) hydrogen evolution rate, nearly 2 times that of SiC–Ar(120.1 μL/(g·h)), and was much higher than that of SiC nanowires (83.9 μL/(g·h)), SiC nanoparticles (82.8 μL/(g·h)) as well as the B-doped SiC photocatalysts(166 μL/(g·h)). In cyclic tests, N-doped SiC also performed excellent photocatalytic durability and good structural stability. It can be concluded that the influence of N-doping introduced defects into the SiC photocatalyst by occupation and mixed phase structure, transformed the band structure into the direct band gap, and formed a shallow donor level for trapping holes. Consequently, higher photocatalytic activities and lower recombination was achieved. Furthermore, the carbon on the photocatalyst which was yielded from the substitution of N or which remained after combustion would build constructed efficient interfacial contact with SiC for the quickening of light-driven electron transfer to the surface, and simultaneously strengthen the adsorption capacity and light-harvesting potential.

New designed procedure for G/SiO2/SiC nano-heterojunctions growth on recycled 3C-SiC powder

New designed procedure for G/SiO2/SiC nano-heterojunctions growth on recycled 3C-SiC powder

Synthesis and Photocatalytic Properties of Iron Disilicide/SiC Composite Powder

ABSTRACTSemiconducting iron disilicide (β-FeSi2) island grains of 50-100 nanometers in size were formed on the surface of Au-coated 3C-SiC powder by metal-organic chemical vapor deposition. On the surface of 3C-SiC powder, the Au-Si liquidus phase was obtained via a Au-Si eutectic reaction, which contributed to the formation of the β-FeSi2 island grains. This β-FeSi2/SiC composite powder could evolve hydrogen (H2) from methyl-alcohol aqueous solution under irradiation of visible light with wavelengths of 420-650 nm.

Preparation of SiC Powders by Carbonthemal Reduction Method at Low Temperature

The stable slurry was prepared by ball-milling with a certain proportion of silica fume as silicon source,glucose as carbon source and metal niobium (Nb) as additives mixed with alcohol water. After the slurry was dried and pulverized, put the powder into a tubular furnace heated to 650℃ for 2h under nitrogen atmosphere to prepare precursor, the heating rate was 5℃/min. Treated the precursor under vacuum by carbothermal reduction method to prepare silicon carbide (SiC) powder. The effect of temperature and additive content on the morphology of synthesised silicon carbide and the impurity removal order on product purity were explored. After firing at 1300℃,1400℃,1500℃ for 2 h, the 3C-SiC powders are detected, and as the temperature increased, the crystallinity of the product become better. When the content of the additive is 1% of the quality of the silica fume, the particle size of the silicon carbide synthesized at the temperature of 1500℃ is even and the dispersion is better. As for the impurity removal order, removed SiO2 first, then removed C can effectively remove the impurities in the product.

Synthesis and characterization of 3C-SiC by rapid silica carbothermal reduction

In this work, rapid carbothermal reduction of silica in a homemade electric arc furnace is reported to produce silicon carbide intended for photovoltaic applications. The influence of carbothermal conditions on the composition and size of the obtained particles is studied. We demonstrate that the variation of the temperature and the atmosphere makes it possible to produce 3C-SiC powders during a short time. Morphological properties of the elaborated SiC powder were investigated using laser granulometry and scanning electron microscopy (SEM). The obtained samples are composed of agglomerated particles of different shapes with micrometric sizes. X-ray diffraction (XRD), fourier transform infrared (FTIR), and Raman spectroscopy analyses show that carbothermal reduction of silica depends on the experimental conditions. Especially, the sample elaborated during 120 s at 1700 °C under CO atmosphere does not present any SiO2 peaks but only pure crystallized cubic silicon carbide (β-SiC) with crystallite size around 44 nm as a result of a complete carbo-reduction of silica. The purity of synthesized SiC is investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES) giving rise to purity about 97.9927%.

Synthesis, microstructure, and luminescence properties of 3C-SiC powders

3C-SiC powders are synthesized successfully by using metallic Na, Si powder and CHI3 as raw materials. The samples are characterized by XRD, FTIR, Raman, TEM, SEM, and luminescence spectroscopy. The XRD patterns, FTIR and Raman spectra indicate that the obtained samples have the cubic phase. The SEM and TEM images suggest that the samples are nano-wires and micro-polyhedra, when different chemical reagents are added in the synthesis. The mean diameter of nano-wires is about 20 nm and the length is about several µm. And the sizes of micro-polyhedra are in the range of 2–5 µm. The two samples show emission band peaking at 395 and 433 nm under the excitation of 220 nm.

Influence of mole ratio of Si: C on the magnetic property of undoped and vanadium carbide doped 3C-SiC

Ferromagnetism (FM) of 3C-SiC powders have been studied by tuning the mole ratio of Si: C. The results of magnetic measurements show that with increasing Si: C, the saturation magnetization (Ms) of undoped 3C-SiC is hardly varied while the Ms of vanadium carbide (VC) doped 3C-SiC is reduced. The introduction of VC mainly leads to the decrease of divacancies (VSiVC) concentration which is the FM origin, and this effect is enhanced with increasing Si: C. Furthermore, the increase of carrier concentration hardly influences the FM of 3C-SiC at VC doping concentration of 0.1wt.%.

Investigation of room temperature ferromagnetism of 3C-SiC by vanadium carbide doping

Undoped and vanadium carbide (VC) doped 3C-SiC powders have been prepared, and an in-depth study is performed on the VC-doping dependence of room temperature ferromagnetism (FM). It is demonstrated that the FM originates in vacancy defects. The saturation magnetization (Ms) of VC is about 800 times than that of undoped 3C-SiC, while the Ms of VC-doped 3C-SiC is even smaller than that of the undoped one. The increase of doping concentration would result in the decrease of vacancy concentration and the increase of carrier concentration, suggesting that the FM of 3C-SiC is related to both vacancy and carrier concentrations.

First principles calculation of electronic structure for Al-doped 3C-SiC and its microwave dielectric properties

The electronic structure and permittivity of Al-doped 3C-SiC are studied by using the first principles plane-wave pseudopotential method based on the density functional theory, and compared with those of undoped 3C-SiC. Results show that the Fermi energy level introduced into valence band and band gap is slightly widened through Al doping for 3C-SiC, and that the permittivity is greatly improved in a frequency range of 8.2-12.4 GHz. Al doped 3C-SiC powder absorber is prepared by combustion synthesis, and the permittivities of the samples are measured in the frequency range of 8.2-12.4 GHz by vector network analyzer, which validates the results of theoretical calculation. The mechanism of microwave loss is discussed.

A Simple Method to Synthesize Nano-Sized 3C-SiC Powder Using Hexamethyldisilane in a CVD Reactor

In this paper, we report a novel route to synthesize nano-sized cubic silicon carbide (3CSiC) powder by a chemical vapor deposition (CVD) technique in a resistance-heated furnace. The nanoparticles were deposited on the relatively cold region of a hot-wall quartz reactor. Hexamethyldisilane (HMDS) was used as the source material for both silicon and carbon. The presence of crystalline 3C-SiC was identified using powder x-ray diffraction (XRD) technique. From the XRD data, the crystallite size was also estimated to be in the range of nanometers (nm). A clear evidence of the particle size (~ 10 - 30 nm) was obtained by transmission electron microscopy (TEM). Selected area electron diffraction (SAED) was carried out on the nanoparticle assembly. The ring shaped pattern is a clear indication of polycrystalline particle formation. High resolution TEM (HRTEM) of nanoparticles was performed to study the crystal structure in detail. The nanoparticles were also characterized by Raman spectroscopy at room temperature. Finally, the influence of the growth parameters is also reported in the present study.