Mixture Of SiC Research Articles

Microstructure and wear property of the Ti5Si3/TiC reinforced Co-based coatings fabricated by laser cladding on Ti-6Al-4V

Ti5Si3/TiC reinforced Co-based composite coatings were fabricated on Ti-6Al-4V titanium alloy by laser cladding with Co42 and SiC mixture. Microstructure and wear property of the cladding coatings with different content of SiC were investigated. During the cladding process, the original SiC dissolved and reacted with Ti forming Ti5Si3 and TiC. The complex in situ formed phases were found beneficial to the improvement of the coating property. Results indicated that the microhardness of the composite coatings was enhanced to over 3 times the substrate. The wear resistance of the coatings also showed distinct improvement (18.4–57.4 times). More SiC gave rise to better wear resistance within certain limits. However, too much SiC (20wt%) was not good for the further improvement of the wear property.

Phase Relations in Si-Al-M-O-C (M = Zr, Mg) Systems

The present work determined the phase relations in Si-Al-M-O-C (M = Zr, Mg) systems, involving SiC-Al2O3-ZrO2, SiC-Al2O3-MgO, SiC-SiO2-Al2O3-ZrO2 and SiC-SiO2-Al2O3-MgO systems by XRD phase analyses of the solid-state reacted samples from powder mixtures of SiC, Al2O3, ZrO2, MgO and SiO2. Within these systems, SiC was respectively compatible with other neighboring phases, forming a set of four-phase compatibility tetrahedrons. The subsolidus phase diagrams of the SiC-SiO2-Al2O3-ZrO2 and SiC-SiO2-Al2O3-MgO quaternary systems were presented.

Fabrication of Cu-30 vol% SiC Composites by Pressureless Sintering of Polycarbosilane Coated SiC and Cu Powder Mixtures

Cu-30 vol% SiC composites with relatively densified microstructure and a sound interface between the Cu and SiC phases were obtained by pressureless sintering of PCS-coated SiC and Cu powders. The coated SiC powders were prepared by thermal curing and pyrolysis of PCS. Thermal curing at 200 °C was performed to fabricate infusible materials prior to pyrolysis. The cured powders were heated treated up to 1600 °C for the pyrolysis process and for the formation of SiC crystals on the surface of the SiC powders. XRD analysis revealed that the main peaks corresponded to the α-SiC phase; peaks for β-SiC were newly appeared. The formation of β-SiC is explained by the transformation of thermally-cured PCS on the surface of the initial α-SiC powders. Using powder mixtures of coated SiC powder, hydrogen-reduced Cu-nitrate, and elemental Cu powders, Cu-SiC composites were fabricated by pressureless sintering at 1000 °C. Microstructural observation for the sintered composites showed that the powder mixture of PCS-coated SiC and Cu exhibited a relatively dense and homogeneous microstructure. Conversely, large pores and separated interfaces between Cu and SiC were observed in the sintered composite using uncoated SiC powders. These results suggest that Cu-SiC composites with sound microstructure can be prepared using a PCS coated SiC powder mixture.

Oxidation behaviour of ZrB2–SiC (Al/Y) ceramics at 1700 °C

ZrB2–SiC(Al/Y) ceramic composites were prepared by hot-pressing a mixture of ZrB2 and polymer-derived SiC doped with either aluminium or yttrium (SiC(Al/Y)). The obtained composites were oxidized at 1700°C in air. The weight change as a function of the oxidation time was measured to study the oxidation kinetics. It was found that the ZrB2–SiC(Al/Y) composites exhibited significantly improved oxidation resistance, as compared to the composite of ZrB2 with un-doped SiC. The structure of the oxide resulted from the oxidation of the composites was characterized by scanning electron microscopy and X-ray diffraction. The results suggested that the improvement can be attributed to the formation of yttrium/aluminium-doped silica and/or yttrium disilicate, which effectively protect the composites.

Effect of SiC and GR Reinforcement Particles on the Structure and Functional Properties of Composite Casting E43 MMC Reinforced with SiC Particles

The aim of the study was to describe the structure of composites based on the AlSi7Mg2Sr0.03 alloy matrix reinforced with SiC particles added in an amount of 10% and with a mixture of SiC and GR particles added in a total amount of 20%. Studies of the composite structure, were carried out by scanning electron microscopy (SEM). Based on the results of chemical analysis in microregions, an increased content of elements such as Mg, O and Si and of the precipitates was observed at the interface. In many places in the examined sample, GR particles formed partly disintegrated conglomerates with well developed boundaries. The effect of the content of particles of the reinforcing phase on the functional properties of the composite was investigated during studies of abrasion. The lowest mass loss of 5,33mg was obtained for the AlSi7Mg2Sr0.03 alloy reinforced with 10% SiC particles.

Manufacturing of cast A356 matrix composite reinforced with nano- to micrometer-sized SiC particles

In this study, large micron-sized SiC particles were fragmented via ball-milling process in the presence of iron and nickel powders, separately, to fabricate composite powders of Fe–SiC and Ni–SiC. Continuous fracturing of brittle SiC powders leads to the formation of multi-modal-sized SiC powders with size of from 50 nm to slightly higher than 10 µm after 36-h ball milling. The milled powders were then incorporated into the semisolid melt of A356 aluminum alloy to ease the incorporation of fine SiC particles by using iron and nickel as their carrier agents. The final as-cast composites were then extruded at 500 °C with a reduction ratio of 9:1. Lower-sized composite powders with slight agglomeration are obtained for the 36-h milled Ni–SiC mixture compared to that of Fe–SiC powders, leading to incorporation of SiC particles into the melt with a lower size and suitable distribution for the Ni–SiC mixture. It is found that lower-sized composite particles could release the fine SiC particles into the melt more easily, while large agglomerated composite particles almost remain in its initial form, resulting in sites of stress concentration and low-strength aluminum matrix composites. Ultimate tensile strength (UTS) and yield strength (YS) values of 243 and 135 MPa, respectively, are obtained for the aluminum matrix composite in which nickel acts as the carrier of fine ceramic particles.

The Effect of Compression Aided by Additional Shear Stress on Microstructure of Composites Reinforced with Ceramic Particles

The paper presents a new method for processing of cast composites reinforced with ceramic particles in order to improve the microstructure homogeneity and material properties. The presented forming method consists in compression aided by additional shear stress that is caused by transverse motion of a punch. As a result, severe plastic deformation can be obtained in a workpiece. A series of experiments was conducted for previously cast Al-Mg-Cu matrix composites containing 15% reinforcement in a form of the mixture of SiC and glassy carbon particles. It was found that the applied method allows to refine the particles and to obtain a good-quality bonding on the particle-matrix interface.

Utilization of Chemically Synthesized Fine Powders of SiC/Al2O3 Composites for Sintering

Fine powders of (Al2O3)100–x(SiC)x (0 ≤ x ≤ 50) composites were prepared by chemical route (named as pyrophoric technique) to achieve a uniform mixture of SiC in an alumina matrix. The chemically synthesized fine SiC/Al2O3 composite powders were sintered to form composites at 1450°C which is well below the sintering temperature of SiC. Sintering was performed in an argon atmosphere. Highly dense SiC/Al2O3 microstructures were achieved. An improvement in bulk density and hardness has been achieved for SiC/Al2O3 composites with 20 wt% of SiC. Hexagonal-shaped grains have been obtained in (Al2O3)50(SiC)50 composite with well-connected grain boundaries. The peak position of alumina in SiC/Al2O3 composites shifts toward lower wavenumbers in Fourier transform infrared spectroscopy and higher wavenumbers in Raman spectroscopy due to the incorporation of SiC in the composites. The optical band gap decreases with the addition of SiC and the composite behaves more like a semiconductor rather than an insulator. These properties make SiC/Al2O3 composites attractive for various industrial applications.

Characterization of Lightweight Earthenware Tiles using Foaming Agents

Green bodies of earthenware tile were prepared from a mixture of earthenware tile powder and SiC as forming agents by applying a conventional process. Granule powder for tile samples was prepared using the spray drying method with commercial earthenware raw material with a quantity of SiC of 0.3 wt%. The applied pressure was 250 kg·f/㎡ and the firing temperature was 1050-1200℃. The effects of the SiC particle size and sintering temperature on the open porosity and total porosity were investigated and the correlative mechanism was also discussed. While total porosity was not significantly changed by decreasing the SiC particle size, the open porosity showed a gradual decrease, which represents an increase of the closed porosity. As the sintering temperature increased, coarsening was made among the pores due to excessive oxidation. The volume shrinkage and bending strength were demonstrated for the sintered tile samples. The sintered bulk density was also measured to determine the weight reduction value.

Phase relations in the SiC–Al2O3–Y2O3 system

Phase relations in the SiC–Al2O3–Y2O3 system were determined by phase analyses of the solid-state reacted samples from powder mixtures of SiC, Al2O3 and Y2O3. The phase diagram at 1700°C of the ternary system was presented. SiC was compatible with each of the three yttrium aluminates of Y4Al2O9 (YAM), YAlO3 (YAP) and Y3Al5O12 (YAG). Stability of the YAP phase and possible effect of the SiO2 impurities on the phase relations in the system were discussed.

Improved Wear Resistance of Al-Mg Alloy with SiC and Al2O3 Particle Reinforcement

Al-3.73Mg alloy was reinforced with a different ratio of SiC and Al2O3 particulate mixtures, and their corresponding wear properties were investigated by pin-on-disk method. The investigation revealed that the mass loss of the hybrid composite at different loads and sliding velocities reduced with the increase of the SiC volume. Only 6% particulate reinforcement in the Al-Mg matrix was enough to reduce the wear of the surface by one-fourth. The wear mechanism was also investigated by examining the worn surface with a scanning electron microscope.

Effect of wet oxidation on recovery of silicon from wire saw slurry by liquid–liquid extraction

Recovering high purity silicon from wire saw slurry generated in silicon wafer production is of great importance, and process suitable for large scale application is yet to be developed. Liquid–liquid extraction method using kerosene as the oil phase was explored in the present study. Wet oxidation of the samples was carried out to find its effect on the purity of recovered Si and its yield. We found that the liquid–liquid extraction is an effective method to recover Si from the slurry if it is wet oxidized to an appropriate degree. When the fraction of Si consumed in oxidation is around 0.034, it can be recovered with high purity and yield. This corresponds to an oxygen content in the Si–SiC mixture which follows the relation {O}wt%=4.0×10-3(1+9Siwt%). The mechanism for the effect of wet oxidation on the recovery of Si and the rationality for the existence of optimal degree of oxidation were discussed.

Cast High-Manganese Steel – the Effect of Microstructure on Abrasive Wear Behaviour in Miller Test

Abstract The results of the modification of austenitic matrix in cast high-manganese steel containing 11÷19% Mn with additions of Cr, Ni and Ti were discussed. The introduction of carbide-forming alloying elements to this cast steel leads to the formation in matrix of stable complex carbide phases, which effectively increase the abrasive wear resistance in a mixture of SiC and water. The starting material used in tests was a cast Hadfield steel containing 11% Mn and 1.34% C. The results presented in the article show significant improvement in abrasive wear resistance and hardness owing to the structure modification with additions of Cr and Ti.

In situ reactive fabrication of ZrC–SiC coating on Cf/ZrC–SiC composite

ZrC–SiC coating on Cf/ZrC–SiC composite was fabricated via in situ reaction using zirconium powder, silicon powder, and phenolic resin as raw materials. The coated composites exhibited excellent oxidation performance. In particular, the coating closely adhered onto the composites, and had a uniform thickness of approximately 90 μm and did not show significant cracking. Even after 30 min of oxidation at 1700 °C in a muffle furnace, the coating thickness of 90 μm remained. Meanwhile, the density of the coating was increased with oxidation because the pores on the surface were filled with the mixtures of ZrC, ZrO2, and SiC. Three distinct layers were formed in the composite, namely, surface oxide, intermediate and unoxidised layers. Therefore, the coating effectively protected the composites from oxidation.

Phase separation of a microsized powder mixture of Si and SiC by Cu–Si alloying

In this paper, a novel Cu–Si alloying method has been studied to separate Si from a microsized Si and SiC powder mixture based on the difference in the melting point and density between solid SiC powders and a liquid Cu–Si alloy. The principle of this method is that Si and Cu powders selectively melt to form a liquid phase at a certain temperature, while SiC powders remain in a solid phase and flow up to the surface due to its lower density relative to the liquid Cu–Si phase. Effects of Si/SiC ratios and Cu fractions in the mixture on separation efficiencies of Si were investigated. For Si/SiC mixtures with an 80wt% ( and above) Si, the highest separation efficiency was achieved when the mass ratio of Cu to Si was between 5 and 9. Under these conditions, a solid Cu–Si alloy ingot and up-floated green SiC powders were obtained. The microstructure of alloy ingots comprised of a predominant Cu3Si phase and a scattered pure Si phase. There were not SiC inclusions in the ingot and the carbon content was only 102ppmw. The recovery ratio of Si was about 90%. The Cu–Si alloying method can separate Si from SiC/Si mixtures effectively, and is a potential approach to recycle Si from cutting slurries in the photovoltaic industry.

Sintering behavior, microstructure and mechanical properties of vacuum sintered SiC/spinel nanocomposite

A mixture of SiC and spinel (MgAl2O4) nanopowder was prepared through the ball milling of talc, aluminum and graphite powder. The powder was uniaxially pressed into the form of pellets and the prepared specimens were annealed at various temperatures for different holding times. The prepared samples were investigated through X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), nanoindentation test, cold crushing strength (CCS) test and Archimedes principle test. The obtained results showed that the hardness, CCS and bulk density did not follow the same trend at different temperatures due to the interaction among various parameters. The detailed investigation of microstructure, phase changes and experimental conditions revealed the mechanisms behind these behaviors. The best sample obtained after annealing at 1200°C for 1h in vacuum had the mean hardness of 1.6GPa and the mean CCS of 118MPa.

Preparation of biomorphic silicon carbide–mullite ceramics using molten salt synthesis

Biomorphic silicon carbide–mullite ceramics were prepared from beech wood using liquid Si infiltration and molten salts synthesis. The resulting mullite whiskers coating, as well as the growth mechanism in molten Al2(SO4)3–Na2SO4 environment, have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) techniques. The biomorphic SiC ceramics derived from the beech wood template have coarse pore walls consisting of β-SiC grains with diameters ranging from 5 μm to 20 μm. After the molten salts reactions between biomorphic SiC substrate and mixture molten salts (Al2(SO4)3–Na2SO4), porous Silicon carbide–mullite ceramics with cilia-like microstructure were obtained. This unique structure has potential application in hot gases filters. An oxidation–dissolution cycle was proposed to explain the mullite whiskers growth in molten salts environment.

Fabrication of Al–2 vol% Al2O3/SiC hybrid composite via accumulative roll bonding (ARB): An investigation of the microstructure and mechanical properties

An Al/Al2O3/SiC hybrid metal matrix composite was fabricated by accumulative roll bonding (ARB). A mixture of Al2O3 and SiC (2vol%) powders was poured between four Al layers during the first two ARB cycles. The process was continued up to eight cycles without adding the powders in subsequent cycles. For comparison, non-reinforced (monolithic) Al was also processed by ARB under the same conditions. At the initial stages, particle free zones as well as particle clusters were observed on the microstructure of the composite. After eight ARB cycles, a composite with a uniform distribution of particles was produced. At this stage, the tensile strength of the hybrid composite and the monolithic Al reaches to about 195MPa and 150MPa, respectively, about 5.3 and 4 times larger than that of annealed Al. The hardness of the composite and the monolithic Al was measured as 83 and 58 VHN, respectively. Fracture surface after tensile testing revealed dimples at some regions after eight ARB cycles.

Separation and Recovery of SiC Particles Discharged from Silicon Wafer Production Process

In the slicing process of silicon wafer from silicon single crystal, it has been the general way to cut silicon by wire saws with the lubricant mixture of silicon carbide, as SiC, particles and wrapping oil. After slicing the silicon single crystal, the waste liquor containing SiC and silicon powders is discharged from the process. The particle sizes of SiC and Si are about 10μm and 1μm, respectively and the weight ratio is about 9:1. The particles discharged from slicing waste liquor become the mixture of SiC and SiO2, when the waste liquor is burned after treating the lubricant oil by a filter press. In terms of the minimization of wastes and environment, it is preferable to separate and recover the valuable SiC from SiO2. In order to solve the problem mentioned above, flotation method can be applied to accomplish the separation of SiC from SiO2. The cationic surfactants of dodecyl-tri-methyl-ammonium chloride (abbreviated as DTMAC hereafter) and tri-methyl-octyl-ammonium chloride (abbreviated as TMOAC hereafter) were used in this study. The adsorption amount of surfactants on SiC and SiO2 particles was measured. The flotation behaviors of SiC and SiO2 were investigated by changing pH, gas flow rate and flotation time in the presence of DTMAC. The purity and yield of SiC were also discussed in the flotation process comprising of roughing, cleaning and scavenging steps. A series of flotation process for SiC gave the purity and yield of 99.7% and 96.7%, respectively.

ChemInform Abstract: In situ Grafted Carbon on Sawtooth‐Like SiC Supported Ni for High‐Performance Supercapacitor Electrodes.

AbstractA new C—Ni—SiC composite is prepared by hydrothermal growth of Ni(OH)2 on sawtooth‐like SiC from a mixture of SiC, Ni(NO3)2 solution, cetyltrimethyl ammonium bromide, and urea (autoclave, 150 °C, 12 h) followed by calcination at 450 °C for 4 h to obtain NiO/SiC composite.