SiC Phase Research Articles

Growth of lamellar Ti3SiC2 in SiC matrix by the reaction of Si melt with C-TiC preform

The SiC-Ti3SiC2 matrix herein was prepared in situ by the melt infiltration (MI) method. The effects of the infiltration temperature and TiC content on the formation of Ti3SiC2 in the SiC matrix were investigated. The mechanism for Ti3SiC2 growth in SiC matrix was determined by investigating the infiltration path of the molten Si into the C-TiC preform. It was found that the Ti3SiC2 phase was mainly formed when the mass ratio of TiC to phenolic resin reached to 2.2, and upon infiltration at 1430 °C for 30 min. It was also demonstrated that the process of molten Si infiltrating into the C-TiC preform occurred through complicated chemical reactions and multicomponent diffusions. The phases of SiC and TiSi2 were preferentially formed during Si melt infiltration. A liquid Ti-Si eutectic appeared upon exceeding the Si-TiSi2 eutectic temperature. Ti3SiC2 was nucleated from the reaction between the TiC and liquid Ti-Si eutectic. The TiSi2 phase was precipitated from the liquid Ti-Si eutectic in the Si region during the cooling process. Moreover, the dissociative SiC grains in the Si region were also produced by the precipitation from the dissolution of the solid C in the liquid Si.

Role of carbon nanotubes on mechanical properties of SiC-B4C-Ni hybrid composites fabricated by reactive spark plasma sintering

The present study was conducted to investigate the microstructural and mechanical properties of SiC-45 vol%B4C-10 vol%Ni and SiC-45 vol% B4C-10 vol%Ni-5vol% CNT in-situ composites fabricated through reactive spark plasma sintering (SPS) method at 1650 °C for 5 min. The phase and microstructural characterization of the composites were evaluated utilizing x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Ultimately, microhardness, flexural strength, and fracture toughness of the composites were measured. Densification behavior of the samples revealed that the initial shrinkage of the composites took place at about 750 °C, which is related to the reaction between Ni and SiC phases. XRD results confirmed the formation of Ni2Si phase. The relative density of 98.3 ± 0.32% was achieved for the SiC-B4C-10Ni sample; this value was 97.8 ± 0.62% for the SiC-B4C-10Ni-5CNT sample. The flexural strength of 362 ± 23 MPa was achieved for the SiC-B4C-10Ni sample; this value was 369 ± 15 MPa for the SiC-B4C-10Ni-5CNT sample. The comparison between the fabricated composites concerning the fracture toughness indicated further fracture toughness of the SiC-B4C-10Ni-5CNT sample (5.82 ± 0.32 MPa m1/2) than that of the SiC-B4C-10Ni sample (3.35 ± 0.56 MPa m1/2). Formation of micro-cracks, crack path deflection, and CNT bridging was the main toughening mechanisms in the SiC-B4C-10Ni-5CNT sample.

Additive manufacturing of silicon carbide by selective laser sintering of PA12 powders and polymer infiltration and pyrolysis

In this work, we propose a novel hybrid additive manufacturing technique, which combines selective laser sintering (SLS) of polyamide powders and subsequent preceramic polymer infiltration and pyrolysis to manufacture Silicon Carbide components for complex architectures. By controlling the porosity of the sintered polymeric preform we are able to control the shrinkage upon the first infiltration and pyrolysis. This enabled the manufacturing of smaller features than those achievable with other manufacturing techniques. The mechanical strength of the resulting ceramic increased with the number of reinfiltration cycles up to 24 MPa, inversely the residual porosity decreased to 10 vol%. The microstructure showed two distinct phases of SiOC and SiC. The first was attributed to the interaction between the porous polyamide and the ceramic precursor during the first infiltration. SiC derived from the pyrolysis of the preceramic precursor alone.

Phase field modeling of diamond-silicon carbide ceramic composites with tertiary grain boundary phases

Phase field simulations are used to study effects of microstructure features on overall strength and ductility of polycrystalline ceramic composites. The material of present interest is a diamond-silicon carbide (SiC) blend with a grain boundary (GB) phase consisting of much smaller SiC grains, graphitic inclusions, and porosity. Homogenized properties—elastic moduli and surface energy—used in the phase field representation of the GB phase are obtained from a novel approach involving bounds from elastic homogenization theory. Extensive parametric calculations on synthetic microstructures with smoothed polyhedral grains are used to deduce trends in structure-property-performance relations. Results suggest that peak strength, for a fixed fraction of GB phase, can be increased by the following prescriptions: increasing bulk diamond content, reducing porosity, reducing graphite content, and distributing any unavoidable defects uniformly rather than randomly. For the assumed constitutive behavior of the GB phase, graphite appears less deleterious than pores of the same average volume fraction, and median defect concentration appears to be more important than randomization of distributions at low volume fractions. More complex interrelations among microstructures, model features, and material responses are also revealed, for example effects of anisotropic fracture, inelastic dilatation associated with crack opening, and twin variant selection in the SiC phase.

An investigation into the microstructural and mechanical properties of the ZrB2/SiC composites prepared by silicon infiltration

In this study, the synthesis of ZrB2/SiC composite was carried out via infiltration of silicon melt into a ZrSiO4/B4C preform, and the effect of different ratios of ZrSiO4/B4C and C/ZrSiO4 was investigated on phase and microstructural properties. For this purpose, stoichiometric ratios of raw materials and 10 wt% phenolic resin were used to induce the porosities in the preform. Then the powder mixture was milled and pressed. To perform pyrolysis reaction, it was placed in a vacuum-controlled atmosphere furnace with argon gas at 650 °C and then the Si infiltration process was performed at 1650 °C for 1 h. The hardness, density, and elastic modulus of the samples were measured. The optimum results were obtained for the composite sample with a ZrSiO4/B4C ratio of 4, which had a density of 5.28 g cm−3, elastic modulus of 423 GPa, and hardness of 33.28 GPa. Moreover, scanning electron microscopy and x-ray diffraction analyses confirmed a uniform distribution of ZrB2 and SiC phases and the absence of undesirable phases in the sample, respectively.

Preparation and characterization of pure SiC filters with an asymmetric structure

In this work, SiC filters with an asymmetric structure were successfully constructed, consisting of solid-state-sintered SiC (S–SiC) supports and in-situ synthesized SiC membranes. The S–SiC supports were prepared by a pressureless sintering technique. Following the preparation of the supports, SiC membranes ~30 μm in thickness were formed in-situ on their surfaces through a dip-coating process combined with carbothermal reduction. Using X-ray diffraction, only the peaks of the SiC phase were detected for both the S–SiC supports and the SiC membranes, indicating the high purity of the asymmetric SiC filters. The distribution of the pore throat size in the SiC membranes was narrow with an average value of ~130 nm, suggesting a high filtration precision. The flexural strengths of the S–SiC supports at room temperature and 1000 °C were 123.6 ± 18.1 MPa and 114.0 ± 4.5 MPa, respectively, enabling the asymmetric SiC filters to withstand high temperatures and high pressures during service. Moreover, asymmetric SiC filters presented excellent acid and alkali corrosion resistance, indicating their great potential for applications in corrosive environments.

Interfacial microstructure evolution and properties of Sn-0.3Ag-0.7Cu–xSiC solder joints

Abstract The impacts of SiC on the wettability, mechanical properties and growth of intermetallic compound (IMC) of the low silver Sn-0.3Ag-0.7Cu (SAC0307) –xSiC composite solders paste prepared by mechanical mixing were investigated. It is found that there is an improvement in the wettability and a large reduction in the thickness of IMC with increasing SiC content, such as the contact angle shrinks by 11.48% and the thickness of IMC at the interface decreases by 63% with 0.10 wt% SiC addition. Meanwhile, according to the fracture morphology analysis, the IMC grains are refined repeatedly with increasing SiC content before less than 0.06 wt%, then agglomerated SiC and brittle phase Ag3Sn appear with further increase in SiC content. As a result, the tensile strength of solders joint increased continuously up to the maximum value of 30.49 MPa with 0.06 wt% SiC addition.

Formation of Ferrosilicon Alloy at 1550°C via Carbothermic Reduction of SiO<sub>2</sub> by Coal and Graphite: Implication for Rice Husk Ash Utilization

Ferrosilicon alloy has been commercially produced in an electric furnace at 1700 - 1750 °C, using quartz as a silica source. With an aim to reduce production cost, rice husk ash (RHA) had been introduced to the process as a silica source. The present study reports an in-depth investigation on the ferrosilicon alloy formation at 1550 °C via carbothermic reduction using RHA with coal and graphite. Blend A: RHA/Fe2O3/Coal and B: RHA/Fe2O3/Graphite were prepared according to the C/O molar ratio of 1/1. The well-mixed samples were compacted into a pellet and then heated at 1550 °C in the tube furnace for 30 and 60 minutes while the argon flowing at the rate of 1 L/min. XRD and SEM results show that the bulk metal mainly composes of FeSi phase, while SiC and other slag phases adhere at the surface of the droplet. Characteristics of the carbonaceous materials, especially ash oxides content affect the kinetic of ferrosilicon formation. Silicon concentration in the produced metal droplets was measured using an ICP technique. For blend A, Si content in the metal was 18.3 wt% and 81.9 wt% after 30 and 60 minutes, respectively. While, Si recovery in the metal for blend B reached 88.4 wt% since 30 minutes. The experimental results show that the production of ferrosilicon alloy from RHA can be produced at 1550 °C, which the temperature lower than that of the commercial method by 150-200 °C. The finding in this research is beneficial for ferrosilicon and agricultural industries and thus promotes the sustainable steelmaking industry.

Densification, solid solution formation, and microstructural investigation of reactive pressureless sintered HfB2-TiB2-SiC-MoSi2 quadruplet composite

Dense HfB2-TiB2-SiC-MoSi2 quadruplet composite was produced by a reactive pressureless sintering method at 2050 °C for 5 h. The relative density was improved and reached 98% by in situ formation of SiC and MoSi2 phases. Microstructural studies proved that SiC and MoSi2 second phases were mostly formed during the sintering process. Moreover, the Sintering mechanism of the composite was investigated by HSC software. TiB2 co-matrix was improved the sinterability of the composite by the formation of (Hf,Ti,Mo)–B and (Hf,Ti,Mo)–C solid solutions.Mechanical properties such as Vickers hardness (23.2 GPa), fracture toughness (5.4 MPa m1/2), and elastic modulus (430 GPa) were effectively enhanced by tailoring the composite.

Effect of Co addition on microstructural and mechanical properties of WC–B4C–SiC composites

In this study, the effect of Co addition on microstructural and mechanical properties of WC-B4C–SiC composites sintered by spark plasma sintering (SPS) method was investigated. For this purpose, three batches of WC-B4C–SiC with different contents of Co (10 vol%, 15 vol%, and 20 Vol %) were sintered at 1400 °C. The results of X-ray diffraction (XRD) analysis of the samples indicated the formation of W2B5, W3CoB3 as well as the remained C phases and unreacted SiC phase. It was observed that by increasing the Co content, the amount of W2B5 phase reduces and W3CoB3 and C contents increase. Therefore, W2B5 peaks were not detected in the sample containing 20vol% Co. Relative density values above 97% were obtained for all the composites. However, a decrease was observed in relative density by increasing the Co content in the composites. The highest flexural strength (510 ± 42 MPa), fracture toughness (10.34 ± 0.82 MPa m1/2), and hardness (20.63 ± 0.75 GPa) were also obtained for the sample containing 10vol% Co compared to the other samples. In addition, Transgranular fracture of SiC as well as pulling out of W3CoB3 and W2B5 particles were observed in the fracture surface micrographs of the samples. The presence of micro-cracks in the SiC grains, fracture of W3CoB3 grains, and crack deflection was reported as dominant toughening mechanisms.

Microstructure and mechanical properties of bilayer B4C/Si-B4C composite

Bilayer B4C based composites, B4C/Si-B4C, consisting of B4C and B4C/Si two-layer, were obtained using hot pressing method. Effect of Si content on microstructure and mechanical properties of the B4C based layered composites was investigated. The B4C/Si-B4C samples showed good interfacial bonding with different Si additions (x = 4, 8, 12 and 16 wt.%) in the B4C/Si layer. Secondary phases SiC and/or TiB2 dispersed randomly in B4C matrices for both layers of the composite by SEM observation. Vickers hardness data for both layers were in a range from 33.1 to 35.2 GPa. Flexural strength and fracture toughness both first increased and then slightly decreased as Si content increased from 4 to 16 wt.%. The fracture toughness of the B4C/Si-B4C composite was significantly improved compared with that of pure B4C material.

Graphitic SiC: A potential anode material for Na‐ion battery with extremely high storage capacity

AbstractBulk SiC phases with tetrahedral arrangements have been identified several decades ago, and have been widely studied due to their potential applications. Until recently, Yaghoubi et al.'s experiment (Chem. Mater. 2018, 30, 7234) observed the existence of graphitic SiC with few SiC layers stacking, which implies the possible synthesis of such material in the future. In this work, we explored the potential application of graphitic SiC as the Na‐ion battery anode via the first‐principle simulation. Our results reveal that the theoretical capacity of graphitic SiC reaches up to 1339.44 mAh/g, which is almost the highest among the already known Na‐ion battery anodes. Together with the low diffusion barrier, moderate open circuit voltage and excellent electronic conductivity during the sodiation, we propose that the graphitic SiC is a potential material as Na‐ion battery anode. More importantly, we find that the intercalation strength of Na ions into C‐based multilayer materials (or the corresponding theoretical capacity, the operation voltage) could be enhanced by increasing the amount of covalent components in NaC bonds, which could be realized via doping by atom (such as Li, Be, B, Al, Si or P) with lower electronegativity than that of C atom.

Microstructure and properties of hot pressed TiB2 and SiC reinforced B4C–based composites

B4C ceramics were strengthened by introducing the hard second–phase particles TiB2 and SiC, and the effects of TiB2 and SiC contents on the microstructure and properties of the composites were investigated. B4C–TiB2 binary composites with TiB2 contents of 10, 20, 30, and 40 vol% were prepared by hot pressing. The microstructure, mechanical properties, and electrical properties of the composites with different TiB2 contents were investigated and compared. The results showed that the B4C–30 vol%TiB2 composite obtained the best comprehensive properties, with a relative density, hardness, bending strength, fracture toughness, and conductivity of 97.9 %, 29.5 GPa, 590 MPa, 6.41 MPa m1/2, and 7.6 × 104 S/m. The compressive stress generated on B4C, crack deflection induced by TiB2, and conductive network formed by TiB2 are of great significance in the context of the properties of the B4C–TiB2 composites. In addition, B4C–TiB2–SiC ternary composites with SiC contents of 0, 10, and 20 vol% were also fabricated by hot pressing. The effect of SiC content on the microstructure and mechanical properties, and the effect of SiC on the antioxidant properties of the composites were investigated. The results showed that the B4C–30 vol%TiB2–10 vol%SiC composite had the best comprehensive properties, with a relative density, hardness, flexural strength, fracture toughness, and residual flexural strength (1600 ℃) of 98.8 %, 29.5 GPa, 621 MPa, 6.80 MPa m1/2, and 465 MPa. The inhibition of the growth of SiC to other grains, removal of oxide impurities, and repair of damage by SiC oxidation products play an important role in the performance of the B4C–TiB2–SiC composites.

The effect of nanometer phase SiC addition on the microstructure and mechanical properties of Al0.6CrFe2Ni2 high entropy alloys

ABSTRACT To improve the strength of single FCC phase Al0.6CrFe2Ni2 high entropy alloy without reducing the plasticity, nano-phase SiC was selected as reinforcement phase. Aseries of as-cast SiC/Al0.6CrFe2Ni2 high entropy alloys with different SiC content (0, 1.25, 2.5, 3.75, 5 vol%) were prepared by vacuum arc melting furnace. And the effect of SiC addition on the microstructures and mechanical properties of Al0.6CrFe2Ni2 high entropy alloy was analysed by microstructure observation, element distribution analysis, compression tests and hardness tests. The results show that the Cr7C3 particles were found in the grain boundaries due to the decomposition of SiC in high temperature, the size and quantity of Cr7C3 particles grow and spread throughout the alloy gradually with the further increase of SiC content. When the added SiC content is 2.5 vol%, the alloy has better comprehensive properties, the yield strength and hardness are 618.43 MPa and 250.78 HV, respectively.

Combined role of SiC whiskers and graphene nano-platelets on the microstructure of spark plasma sintered ZrB2 ceramics

This research explores the sintering behavior and microstructure of ZrB2-based materials containing graphene nano-platelets (GNPs) and SiC whiskers (SiCw). Spark plasma sintering (SPS) process at 1900 °C was implemented to sinter the specimen, leading to a composite with 100% relative density. High-resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), field emission-electron probe microanalyzer (FE-EPMA), and high-resolution X-ray diffractometry (HRXRD) were employed to study the SPSed sample, along with the thermodynamics predictions. According to the HRXRD result and microstructural observations, the sintering process was non-reactive, which was endorsed with the XPS analysis. Furthermore, graphene presented a beneficial role for eradicating the oxide impurities in the sample during the sintering. Such oxide impurities were reduced to the original phases of SiC and ZrB2, contributing to porosity removal. Nanostructural investigations revealed the formation of ultrathin amorphous interfaces (~10 nm) between ZrB2/graphene phases, disordered atomic planes in graphene platelets, and dislocations in ZrB2 grains. One reason for generating crystalline defects in the microstructure was found out to be the mismatches amongst the elastic properties of the available compounds in the system.

Tuning of the high temperature behaviour of Si–C–N ceramics via the chemical crosslinking of poly(vinylmethyl-co-methyl)silazanes with controlled borane contents

The thermal stability, elemental/phase composition evolution and crystallization behaviour of Si–B–C–N ceramics obtained by the pyrolysis of a series of poly (vinylmethyl-co-methyl)silazanes displaying various boron contents were investigated through annealing in the temperature range 1000–1800 ​°C under nitrogen atmosphere. The increase of the boron content in the early stage of the process involved the nucleation of β-SiC, inhibited the crystallization of α-Si3N4 and modified the activity of the sp2-hybridised carbon phase in the derived ceramics obtained at 1000 and 1400 ​°C. At 1800 °C, low boron content Si–B–C–N ceramics gradually evolved toward a major SiC phase mainly formed via the carbothermal reaction of amorphous Si3N4 whereas high boron content Si–B–C–N ceramics led to highly stable materials with a complex microstructure made of SiC, Si3N4 and a BN-rich B(C)N phase that inhibited the activity of sp2-hybridised carbon toward the carbothermal reaction of amorphous Si3N4 and significantly reduced the SiC crystallization process.

Corrosion and chemical behavior of Mg97Zn1Y2-1wt.%SiC under different corrosion solutions

To explore the corrosion properties of magnesium alloys, the chemical behavior of a high strength Mg97Zn1Y2-1wt.%SiC alloy in different corrosion environments was studied. Three solutions of 0.2 mol·L−1 NaCl, Na2SO4 and NaNO3 were selected as corrosion solutions. The microstructures, corrosion rate, corrosion potential, and mechanism were investigated qualitatively and quantitatively by optical microscopy (OM), scanning electron microscopy (SEM), immersion testing experiment, and electrochemical test. Microstructure observation shows that the Mg97Zn1Y2-1wt.%SiC alloy is composed of α-Mg matrix, LPSO (Mg12ZnY) phase and SiC phase. The hydrogen evolution and electrochemical test results reflect that the Mg97Zn1Y2-1wt.%SiC in 0.2 mol·L−1 NaCl solution has the fastest corrosion rate, followed by Na2SO4 and NaNO3 solutions, and that the charge-transfer resistance presents the contrary trend and decreases in turn.

Retracted] A Comparative Study on Crack‐Healing Ability of Al2O3/SiC Structural Ceramic Composites Synthesized by Microwave Sintering and Conventional Electrical Sintering

This study was conducted to assess and compare the crack‐healing ability of conventional electrical sintered and microwave sintered Al2O3/x wt. % SiC (x = 5, 10, 15, and 20) structural ceramic composites. The crack‐healing ability of both conventional electrical sintered and microwave sintered specimens was studied by introducing a crack of ∼100 µm length by Vickers’s indentation and conducting a heat treatment at 1200°C for dwell time of 1 h in air. The flexural or bending strength of sintered, cracked, and crack‐healed specimens was determined by three‐point bending test, and the phase variations by X‐ray diffraction and SEM micrographs before and after crack‐healing of both the sintering methods were studied and compared. The results show that almost all the specimens recovered their strength after crack‐healing, but the strength of microwave sintered Al2O3/SiC structural ceramic composites has been shown to be better than that of conventional electrical sintered Al2O3/SiC structural ceramic composites. The microwave sintered crack‐healed Al2O3/10 wt. % SiC specimen shows higher flexural strength of 794 MPa, which was 105% when compared with conventional electrical sintered Al2O3/10 wt. % SiC and crack‐healed Al2O3/10 wt. % SiC specimen. It was found by X‐ray diffractogram that before crack‐healing, all the conventional electrical sintered samples have SiO2 phase which reduce the crack‐healing ability and microwave sintered samples with 15 and 20 wt. % SiC show lesser SiO2 phase and 5 and 10 wt. % SiC samples have no SiO2 phase before crack‐healing. However, after crack‐healing treatment, all the samples have distinct SiO2 phase along with Al2O3 and SiC phases. Microwave sintered Al2O3/10 wt. % SiC specimen cracks were fully healed which was evident in SEM micrographs.

Electronic band structure of Bi-intercalate layers in graphene and SiC(0001)

A potential way to tune the electronic band structure of graphene is to intercalate foreign atoms in the interface between graphene and substrate. However, such an intercalate layer covered by graphene is difficult to directly study with microscopic probes, and relatively little is known about its crystal and electronic structures. In this work, we study epitaxial graphene on SiC(0001) intercalated by bismuth atoms by means of angle-resolved photoemission spectroscopy. We reveal the electronic band structure of Bi-intercalate layers, from which we could identify two distinct phases, one is metallic and the other is insulating. The metallic phase composed of closely packed Bi atoms shows nearly free electron bands that are repeated to follow the period of SiC(0001)-(1 $$\times $$ 1). The lower coverage insulating phase shows characteristic flat bands in the period of SiC(0001)-( $$\sqrt{3} {\times } \sqrt{3}$$ )R30 $$^\circ $$ with respect to the surface lattice constant of SiC(0001). Even though there exists such two distinct phases in the Bi intercalate layer, the doping level of graphene is found to vary rather continuously with the coverage of Bi. Based on the observed band structures and Bi 5d core-level spectra, we suggest a structural model for the metallic and insulating phases of Bi-terminated SiC(0001).

Characterization and sliding wear behavior of CoMoCrSi + Flyash composite cladding processed by microwave irradiation

The present work deals with the development of CoMoCrSi + Flyash composite cladding on AISI 410 steel substrate using a domestic microwave oven with cladding process parameters of frequency 2.45 GHz, with the power of 900 W and processing time is 1800 s. The developed clad is characterized by metallographic and mechanical properties. Further, the substrate and cladding samples are tested for high-temperature sliding wear behaviour using a pin on disc apparatus. The clad specimen exhibits partial melting of particles and observed uniformity in thickness. X-Ray Diffraction analysis shows the presence of Cr3C2, Co3Ti, TiC, SiC, and Mo3Si hard phases that are formed during the cladding process, while excellent metallurgical bonding can be observed which provides improved hardness. The addition of flyash into the cobalt-base matrix enhanced high-temperature strength results in better wear resistance due to the formation of oxide layers.