β-SiC Particles Research Articles

Comparison of oxidation resistance of high-entropy (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC composites prepared by different methods at 1300–1600 °C

Dense monolithic (Ti0.2Zr0.2Hf0.2Ta0.2Nb0.2)C/SiC (HEC/SiC) composites were prepared via single-source-precursor (SSP) and solid-state reaction (SSR) method, respectively. The SSP-method nanocomposite features HEC nanoparticles uniformly dispersed within β-SiC, while the SSR-method composite is a microcomposite containing micro-sized HEC and β-SiC particles. The oxidation tests at 1300–1600 ºC show that the HEC/SiC nanocomposites exhibit much better oxidation resistance than that of the HEC/SiC microcomposites. Firstly, the generated metal-containing complex oxides ((Zr,Hf)6Ta2O17, Ti(Ta,Nb)2O7, and Ta-doped rutile TiO2) become more facile for sintering due to the nano-scaled HEC phase. Secondly, the cracks resulting from the oxidation of HEC nanoparticles are fewer and smaller, decreasing the number of channels for oxygen to pass through and channels need to be healed by SiO2. Finally, the homogeneous distribution of the HEC nanoparticles within β-SiC ensures the homogeneity of the complex oxide layer, significantly reducing the cracks caused by volume expansion and preventing the oxide layer from peeling off.

In-situ synthesis and chemical bonding of the Al-doped β-SiC particles in Al-Si-C light alloys

In this work, the Al-doped β-SiC particles are in-situ synthesized in Al-20Si-5C alloys using the novel liquid–solid multiphase reaction method. The morphological evolution with changed Al doped β-SiC particles has been carefully investigated, and it is observed that the β-SiC transforms from the hexagonal flake to the truncated pyramid and finally evolves to the irregular polyhedral with the decrease of Al doping in SiC. The influence mechanism of the Al doped amount of SiC on the Brinell hardness and wear resistance of the Al doped SiCp reinforced aluminum matrix composites has been explored. Furthermore, the density functional theory (DFT) calculations of the chemical structures of doped SiCp with different Al doping levels indicate the covalent bond proportion in SiCp and the electron density around carbon atoms are all decreased as the increase of the Al doping content. It is also found that the Young’s modulus and Vickers hardness of doped SiCp decrease as the Al doping content increases by DFT calculations. It is proposed that this work paves a new way to improve the properties of aluminum matrix composites by regulating the doped level and chemical bonding of reinforcing particles for potential light weighting applications.

Graphene-coated pearl-chain-shaped SiC nanowires

In this work, graphene-coated SiC nanowires (SiCnw) were fabricated by SiC epitaxial growth method. Firstly, the centimeter-scale single crystal SiC nanowires were synthesized through carbothermal reduction without any catalysts. Secondly, the epitaxial graphene grows on the surface of the SiCnw in a high vacuum and high-temperature environment to obtain graphene-coated pearl-chain-shaped SiCnw. In addition to the observed graphene layer coated on the surfaces of SiCnw, the formed β-SiC particles are densely and orderly arranged along the SiCnw. The growth of graphene layer coated on the surfaces of SiCnw can be ascribed to the thermal evaporation of Si or SiO2 on the surfaces of SiCnw. The formation mechanism of SiC particles is speculated to be the carbothermic reduction between the SiO and the CO or residual carbon generated by decomposition of SiC nanowires. The graphene-coated pearl-chain-shaped SiCnw have many potential applications in ceramic reinforcement, optoelectronics, mid-infrared and EM wave absorption devices.

Microwave heating and mechanism for seed-induced synthesis of SiC

We prepared silicon carbide (SiC) through microwave heating using α-SiC particles, coal mineral particles, and tetraethoxysilane as seeds, carbon source, and silicon source, respectively. By characterising the phase and microstructure, the effects of different temperatures, holding time, and seed content on the growth of SiC crystals were studied. β-SiC and α-SiC particles were synthesised through microwave heating at 1100 °C for 10 min. An increasing holding time resulted in higher whisker yield. The crystal generation mode was through a vapor-vapor reaction, in which SiC crystallites formed on the surface of the α-SiC seeds via in situ nucleation and grain growth. The impedance matching between coal minerals and α-SiC seeds varied with the seed content, which also influenced the power redistribution, results in different heating rates, phases, and morphologies during microwave heating. The 15 wt% seed content was identified as the optimal value for both microwave heating effects and power redistribution, which promoted the formation of β-SiC whiskers. These results show that the rapid synthesis of SiC is achieved while coal as carbon source, which will greatly reduce cost to promote the commercialization of SiC via microwave heating.

Spark Plasma Sintering of Al-=SUB=-2-=/SUB=-O_3-SiC ceramics. Study of the Microstructure and Properties

The features of spark plasma sintering of submicron Al2O3 powders with different contents (0, 0.5, 1.5, 5 vol.%) of β-SiC nanoparticles have been studied. The microstructure and hardness of Al2O3 + 5 vol.% SiC ceramics obtained by sintering Al2O3 powders with β-SiC particles of various types (nanoparticles, submicron particles, fibers) have been studied. Sintering was carried out at heating rates (Vh) from 10 to 700oC/min. The sintering process of Al2O3 + SiC ceramics with low heating rates (V_h=10-50oC/min) has a complex three-stage character, with a flat area in the temperature range of 1200-1300oC. At high heating rates (V_h>250oC/min), the usual three-stage character of sintering is observed. The analysis of temperature dependences of compaction was carried out using the Young-Cutler model; It was found that the kinetics of powder sintering is limited by the intensity of grain boundary diffusion. It is shown that the dependence of the hardness of Al2O3 + SiC ceramics on Vh has a nonmonotonic character, with a maximum. In the case of pure alumina, an increase in Vh leads to a monotonic decrease in hardness Keywords: Alumina, silicon carbide, density, diffusion, hardness.

Effect of processing technology on structural stability of SiC/SiBCZr ceramic matrix composites

SiC/SiBCZr composites were prepared through polymer impregnation and pyrolysis process using the second generation SiC fibers as raw material. The effects of surface substrate removal, secondary densification, and deposition coating on the structure, mechanical properties, and high temperature stability of SiC/SiBCZr composites were investigated. Results showed that the porosity of SiC/SiC composites could be greatly diminished by the optimized treatment process, and the surface of SiC/SiBCZr composites is uniformly filled into the pores by β-SiC particles, thereby achieving the sealing effect. Meanwhile, the as-prepared SiC/SiBCZr composites had excellent high temperature structural stability. At the later stage of oxidation reaction, borosilicate oxidation products with moderate fluidity, fluid lava form and self repairing function generated from ceramic matrix can effectively inhibit the oxidation reaction and improve the high temperature structural stability of SiC/SiBCZr composites. The above-mentioned high temperature structural stability provided the foundation and technical support for improving the service life and expanding the application of SiC/SiBCZr composites.

Microwave Sintering Rapid Synthesis of Nano/Micron β-SiC from Waste Lithium Battery Graphite and Photovoltaic Silicon to Achieve Carbon Reduction

The paper describes one promising method and approach for the recycling, reuse, and co-resource treatment of waste photovoltaic silicon and lithium battery anode graphite. Specifically, this work considers the preparation of nano/micron silicon carbide (SiC) from waste resources. Using activated carbon as a microwave susceptor over a very short timeframe, this research paper shows that nano/micron β-SiC can be successfully synthesized using microwave sintering technology. The used sintering temperature is significantly faster and more energy-efficient than traditional processes. The research results show that the β-SiC particle growth morphology greatly affected by the microwave sintering time. In a short microwave sintering time, the morphology of the β-SiC product is in the form of nano/micron clusters. The clusters tended to be regenerated into β-SiC nanorods after appropriately extending the microwave sintering time. In the context of heat conversion and resource saving, the comprehensive CO2 emission reduction is significantly higher than that of the traditional SiC production method.

Polymer-derived silicon carbide micro powders through selective solvent precipitation of high molecular weight polycarbosilane

Synthetic route to β-SiC micro powders through selective solvent precipitation (SSP) of high-molecular-weight (HMF) polycarbosilane. (PCS) was developed. PCS (>3000 Da) was obtained through pyrolysis polycondensation of Polydimethylsilane. Spectral data confirmed that PCS could be fractionated and precipitated during the process without disturbing its molecular structure. Fractionated fine PCS powders were converted into crystalline β-SiC particles through ceramization at 1200–1450 °C under argon. XRD patterns revealed a strong and sharp peak at a diffraction angle of 35.8°, thereby confirm the β-SiC structure and purity. SEM analysis confirmed the particle morphology and aggregation of β-SiC particles. Particle size analysis results show that the SiC particles' size is in the range of 10–100 μm. Thermal data prove the high thermal stability of PCS-HMF. β-SiC particles were thermally inert up to 1000 °C and became reactive beyond 1000 °C.

Transformation of \u03b2-SiC from Charcoal, Coal, and Petroleum Coke to \u03b1-SiC at Higher Temperatures

SiC is one of the main intermediate compounds formed during the industrial production of silicon (Si). In the Si process, SiC is produced when carbon added to the raw materials reacts with the silicon monoxide gas (SiO(g)) formed in the furnace. Carbon materials used are either biomass-based (charcoal and wood chips) or based on fossil sources (coal, coke, petroleum coke). The most common forms of SiC prevailing at atmospheric pressure are the polytypes of α-SiC and β-SiC. β-SiC is formed at low temperatures and transforms to α-SiC at higher temperatures (> 2000 °C). In this study, β-SiC with elemental Si of varying amounts, formed from industrial carbon materials (charcoal, coal, and petroleum coke), were utilized to study the transformation of β-SiC to α-SiC. A graphite tube furnace efficient for high-temperature experiments was utilized for the heat treatment of β-SiC particles at temperatures ranging from 2100 °C to 2450 °C. The transformation to α-SiC was greatly influenced by the original carbon source. Charcoal-converted β-SiC particles easily transformed to α-SiC at 2100 °C, compared with β-SiC produced from coal and petroleum coke. Moreover, the amount of elemental Si in SiC particles enhanced the transformation to α-SiC at 2100 °C.

Non-Linear Conductivity Epoxy/SiC Composites for Emerging Power Module Packaging: Fabrication, Characterization and Application.

In this paper, SiC/epoxy resin composites containing different amounts of micro-sized SiC with different crystal morphologies were fabricated to study the effects of crystal morphology and temperature on non-linear conductivity characteristics. The research results illustrate that the β-SiC particles can provide a higher non-linear conductivity, compared with the α-SiC particles. The presence of temperature also affected the non-linear conductivity behaviors of the epoxy/SiC composites. When the α-SiC content was low, the non-linear conductivity coefficient of the composites increased rapidly as the temperature increased, but the non-linear conductivity decreased slightly as the temperature increased when the filler concentration was large enough. To reduce the influence of the electric field concentration effect by the increase in power density on the power module packaging, the voltage sharing application of the SiC/epoxy composites was simulated by COMSOL Multiphysics (v5.2a, COMSOL Inc., Stockholm, Sweden). The results show that the composites with non-linear conductivity can reduce the electric field stress. The emerging insulation material obtained by the SiC-modified epoxy resin can effectively promote electric field distribution uniformity, and ensure the safe operation of the power module.

Pulsed electrodeposition, mechanical properties and wear mechanism in Ni-W/SiC nanocomposite coatings used for automotive applications

In the present work, the dry sliding wear behaviour of electrodeposited Ni-W/SiC nanocomposite coatings after heat treatment was studied. For that purpose, Ni-14 (at%) W/SiC composite coatings with varying proportion of β-SiC particle content were deposited using pulsed current electrodeposition and subsequently heat-treated at 500 °C in vacuum. The coatings were analysed for its structure, surface topography, particle content in coating and inter-particle spacing. The mechanical properties of coatings were evaluated and correlated with SiC content in the respective coating. Sliding wear tests under dry condition were carried out (at room temperature) against WC-Co disc using pin-on-disc configuration. It has been observed that the mechanical properties of nanocomposite coatings follow the rule of mixtures (ROM). The wear rate of the nanocomposite system has demonstrated a linear relationship with the inter-particle spacing of SiC particles embedded in the Ni-W matrix. Specific wear rate and friction coefficient of nanocomposite coatings were rationalised through a mathematical model based on the inverse rule of mixtures (I-ROM).

Novel process for recrystallized silicon carbide through β-α phase transformation

A novel process was investigated to produce recrystallized silicon carbide through β-α phase transformation. The specimen was prepared from carbon and β-SiC powder mixture, first by infiltration with liquid silicon at 1500 °C to form β-SiC preform with a high density, and then by heating it further up to 2200 °C. When the β-SiC particles were transformed into α-SiC at 2200 °C, the rapid grain growth occurred of the α-SiC by consuming β-SiC particles, resulting in an interconnected network structure with huge and elongated α-SiC grains. The specimen recrystallized at 2200 °C had a measured density of 2.7 g/cm3 and strength of 134 MPa. The infiltration behavior, microstructure evolution and mechanical properties of the recrystallized silicon carbide were examined and discussed.

In-situ preparation and mechanical property analysis of SiC/SiBCN(O) nanocomposites

In this paper, the dense SiC/SiBCN(O) nanocomposite without obvious crack and/or void was prepared by employing SiBCN(O) amorphous ceramics as starting material. Via controlling heat treatment time of the raw material at 1400 °C, nano β-SiC grains were in situ generated and uniformly dispersed within the amorphous SiBCN(O) ceramic matrix, and the target materials were thus obtained, which may provide a new strategy for fabricating the dense SiBCN(O) based nanocomposties. The influence of dwelling time on chemical composition, grain precipitation and mechanical properties of the materials were also investigated. The experimental results showed that the prepared SiC/SiBCN(O) nanocomposite was dense and pore/crack free, and with the increase in holding time at 1400 °C, the chemical composition of the materials became more uniform and its mechanical properties were significantly improved as well. Particularly, after holding at 1400 °C for 8 h,a number of β-SiC particles with an average size of 28 nm were in-situ precipitated and homogeneously dispersed in the amorphous SiBCN(O) matrix, compared with their counterpart experienced 2 h heat treatment, its nano-hardness, micro-region elastic modulus, flexural stress and elastic modulus were enhanced from ~5 GPa, ~50 GPa, ~40 MPa and ~10.7 GPa, to ~25 GPa, ~190 GPa, ~145 MPa and ~22 GPa, respectively.

Fabrication of a 3D4d braided SiCf/SiC composite via PIP process assisted with an EPD method

Abstract In order to improve the thermal conductivity and full-fill the gaps between the fiber bundles for three-dimensional four-directional (3D4d) braided SiCf/SiC composites, 500 nm submicron-sized β-SiC particles were introduced into the 3D4d preform by an electrophoretic deposition (EPD) method. ζ-potential of the KD-Ⅱ SiC fibers and the aqueous suspension of the β-SiC particles were analyzed, as well as the efficiency of the deposition. After densified via PIP process, microstructure, three-point bending strength and thermal conductivity of the composite were investigated. The results showed that, SiC particles filled the gaps between the SiC fiber bundles efficiently, and thermal conductivity of the composites fabricated through PIP process assisted by EPD was 2.3 times that of the composites fabricated via PIP only. The bending strength of the EPD-composites was 647.08 ± 69.53 MPa, which decreased to 2/3 of that of the composites manufactured only by PIP, owing to the reduction of fiber volume fraction and the damages to the interface coatings and fibers under the action of the electric field.

Observation of the transformation of silica phytoliths into SiC and SiO2 particles in biomass-derived carbons by using SEM/EDS, Raman spectroscopy, and XRD

Scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction were successfully used to observe the location and morphology of the silica phytoliths in biomass-derived carbons and their transformation into SiC and SiO2 particles at high heat treatment temperatures (HTT). The analyses were conducted in chars derived from the endocarp of babassu coconut (EBC), which naturally contains 1.6 wt% of silica in its mineral matter. It was observed that EBC chars with 500–1200 °C HTT present globular echinate SiO2 phytoliths with sizes of 12–16 μm; these phytoliths are mostly concentrated around the surface of the submillimeter char fibers and also in the carbonaceous char matrix. No phytoliths are found in the interior of the char fibers. At 1200 °C HTT, the phytoliths begin to be rounded, and above 1300 °C HTT, most phytoliths decompose and silicon reacts with carbon-forming nanocrystalline β-SiC particles (~ 35 nm crystallite size). Numerous (tens to hundreds) micro- and sub-micro-amorphous or nanostructured SiO2 particles (with sizes predominantly below 2 µm) are then observed at the sites previously occupied by the phytoliths. Few rounded phytoliths survive at 1400 °C HTT, but disappear at higher HTTs (1600–2000 °C). It is likely that the ensembles of micro- and sub-micro-SiO2 particles observed in many sites correspond to the inner remaining part of the original phytoliths, whose most external SiO2 structures (at and near the surface) decompose and take part in the carbothermal reaction for the formation of SiC.

Development of bulk ultrafine grained Al-SiC nano composite sheets by a SPD based hybrid process: Experimental and theoretical studies

In the present work, a hybrid manufacturing route, combining stir casting with cryorolling, is proposed for production of Ultrafine grained (UFG) nano composite sheets using an Al 1050 matrix in combination with β-SiC particles (0.5 wt%, 1 wt%, 2 wt%). The method provides the scope for generating UFG microstructures with homogeneous distributions of nano particles that are difficult to achieve with existing manufacturing routes. The influence of the nano SiC reinforcement on the mechanical properties of the UFG nano composites were studied with an emphasis on the characterization of the microstructure. The results show that with an increasing content of reinforcement, the degree of grain refinement and strength of the UFG nano composite increases while the ductility reduces. The microstructural information and the obtained yield strengths of the UFG nano composites were validated with a mathematical model. For this, an existing dislocation density based model was modified to account for the effect of nano reinforcement and processing parameters.

Harmonized toughening and strengthening in pressurelessly reactive-sintered Ta0.8Hf0.2C-SiC composite

Ta0.8Hf0.2C-27 vol%SiC (99.0% in relative density) composite was toughened and strengthened via pressurelessly in-situ reactive sintering process. HfC and β-SiC particles were formed after reaction of HfSi2 and carbon black at 1650 °C. Ta0.8Hf0.2C was obtained from solid solutioning of HfC and commercial TaC. The β-α phase transformation of SiC proceeded below 2200 °C. High aspect ratio, platelet-like α-SiC grains formed and interconnected as interlocking structures. Toughness and flexural strength values of 5.4 ± 1.2 MPa m1/2 and 443 ± 22 MPa were measured respectively. The toughening mechanisms by highly directional growth of discontinuous α-SiC grains were crack branching, bridging and deflection behaviors.

Residual stress measurement in a metal microdevice by micro Raman spectroscopy

Large residual stress induced during the electroforming process cannot be ignored to fabricate reliable metal microdevices. Accurate measurement is the basis for studying the residual stress. Influenced by the topological feature size of micron scale in the metal microdevice, residual stress in it can hardly be measured by common methods. In this manuscript, a methodology is proposed to measure the residual stress in the metal microdevice using micro Raman spectroscopy (MRS). To estimate the residual stress in metal materials, micron sized β-SiC particles were mixed in the electroforming solution for codeposition. First, the calculated expression relating the Raman shifts to the induced biaxial stress for β-SiC was derived based on the theory of phonon deformation potentials and Hooke’s law. Corresponding micro electroforming experiments were performed and the residual stress in Ni–SiC composite layer was both measured by x-ray diffraction (XRD) and MRS methods. Then, the validity of the MRS measurements was verified by comparing with the residual stress measured by XRD method. The reliability of the MRS method was further validated by the statistical student’s t-test. The MRS measurements were found to have no systematic error in comparison with the XRD measurements, which confirm that the residual stresses measured by the MRS method are reliable. Besides that, the MRS method, by which the residual stress in a micro inertial switch was measured, has been confirmed to be a convincing experiment tool for estimating the residual stress in metal microdevice with micron order topological feature size.

Effects of SiC particle size on electrochemical and mechanical behavior of SiC-based refractory coatings

Refractory paints are designed to display good thermal resistance, as well as excellent corrosion and mechanical properties in service. The present work investigates the corrosion and mechanical performance of SiC-based refractory paints. Refractory paints containing varying amounts of silicon carbide (β-SiC) along with alkali inorganic binders were used. The alkali activator used was an aqueous solution of NaOH/Na2SiO3, with metakaolin used as the aluminosilicate material. Five samples with varying proportions of β-SiC particles of varying size fraction were used to prepare the bimodal β-SiC. The samples used were 100% micron, 70% micron + 30% nano, 50% micron + 50% nano, 30% micron + 70% nano, and 100% nano-SiC as the aggregate, and this was mixed with the binder and then applied on nickel-based super alloy (Inconel 738) and then cured at 80 °C for 24 h and then exposed to 1100 °C for 8 h. Abrasion, corrosion, and electrochemical tests were used to determine the properties of the coating. The analyses showed that by increasing the proportion of nano-SiC, the porosity decreased which in turn helped to enhance the corrosion and abrasion resistance.

Synthesis of silicon carbide nanopowders in free flowing plasma jet with different energy levels

Silicon carbide (SiC) nanopowders were produced by the synthesis in an electrodischarge plasma jet generated by a high-current pulsed coaxial magnetoplasma accelerator. The present work focuses on the experiments where the obtained hypersonic plasma jet flew into space of the reactor chamber without impact on a target. The energy level of experiments was changed from ∼10.0 to ∼30.0 kJ. Four experiments were carried out at different energy levels. The powder products synthesized by the plasmadynamic method were studied by such well-known methods: X-ray diffraction (XRD), transmission electron microscopy (TEM). All the powders mainly contain cubic silicon carbide (β-SiC) particles with clear crystal structures and triangular shapes. SiC content reaches its maximum value 95% at the energy level 21.0 kJ, then SiC content is decreased to 70% the energy level 27.8 kJ. The powder crystallites in different experiments have approximately the same average crystallite size because quasistationary time, which allows growing powder crystallites, is absent.