Silicon Carbide Content Research Articles

Temperature-dependent charge property of silicone rubber/SiC composites under lightning impulse superimposed DC voltage

Field grading materials (FGMs) with nonlinear conductivity, which can form a uniform local field in high-voltage direct current (HVDC) cables, have received considerable attention. This paper focuses on the temperature-dependent charge transport property of an FGM based on high-temperature vulcanized (HTV) silicone rubber (SiR). A nonlinearity in the conductivity is achieved by mixing silicon carbide (SiC) particles with the SiR matrix. The conductivities of the samples are measured at temperatures of 30–90 °C. In addition, the surface potential decay is analyzed. The experimental results show that the nonlinear conductivity is suppressed at high temperatures. Increased temperature can cause a lattice vibration, which scatters carriers and reduces the conductivity. With an increase in the homopolar impulse voltage, all samples experiences a rise in the initial surface potential. The increase in SiC content and the increase in impulse voltage can both accelerate the decay process. The heteropolar impulse voltage not only intensifies the accumulation of surface charge but also slows down the decay process. Neutralization occurs immediately between heterocharges. The positive charges are captured by traps, and the attraction between heterocharges is thought to be the reason for the observed phenomena.

Influence of SiC Content on Microstructure and Tribological Properties of Friction Stir-Processed SiC/AA5083 Surface Composites

The present work aims to produce silicon carbide (SiC) particles-reinforced AA5083 surface composites through friction stir processing (FSP). The influence of SiC content on the microstructure and tribological properties of the friction stir-processed (FSPed) AA5083/SiC surface composites was investigated. The results reveal that the distribution of SiC particles within the stirred zone was homogeneous, irrespective of location, and SiC particle volume fraction. Good SiC/AA5083 interfacial bonding was obtained for all surface composites with refined grains. Electron backscattered diffraction results revealed that the stir zones comprised dynamically recrystallized, fine-grained, and equiaxed microstructures. Transmission electron microscopy revealed that dislocations rearranged to form high-angle grain boundaries upon dynamic recrystallization. The worn surface showed that an increase in SiC volume fraction transforms the wear from severe plowing, and delamination to light abrasive wear. The surface composites showed a substantial decrease in wear rate with an increase in SiC volume fraction due to the homogeneous distribution of SiC particles, grain refinement, and improved hardness. The wear debris of AA5083 alloy showed large flakes as a sign of severe plastic deformation whereas, surface composite samples comprised of fine wear debris.

Silicon nitride ceramics with light-melting sintering additive in CaO-TiO2 system

The aim of this work was to obtain Si3N4/SiC composites, where silicon nitride served as the matrix, and the silicon carbide content varied from 3 to 50wt.%. To reduce the sintering temperature (hot pressing) of the ceramic, it is used a sintering additive of calcium aluminate eutectic. The charge was prepared as follows: the silicon nitride powder was mixed with 10 wt.% sintering calcium aluminates, then the charge was added over 100 % of silicon carbide in an amount of 3, 5, 7, 10, 15, 20 and 50 wt.% in a planetary mill. Ceramic materials were hot pressed at 1660°C, the pressure was 30 MPa for 60 minutes in N2 atmosphere. The 10 wt.% SiC composite has highest properties: 3.16 g/cm3 density, 650 MPa bending strength, 22 GPa microhardness.

Morphology-controlled synthesis of hollow Si/C composites based on KI-assisted magnesiothermic reduction for high performance Li-ion batteries

Magnesiothermic reduction of silicon oxide (SiO2) is thought to be an effective method for preparing nanostructured silicon (Si). However, the magnesiothermic reduction can hardly maintain the original shape of the SiO2 due to the harsh reaction condition. Carbon coating is an efficient strategy to prevent the original structure collapse and improve its conductivity, while the by-product silicon carbide (SiC) is prone to form due to the over-heating phenomenon during the process, which is useless to the Li-ion storage. Herein, potassium iodide (KI) is used as heat scavenger for the first time to control the formation of SiC, in which the melt of KI can absorb excess heat during the harsh reduction process. Ideally, hollow Si/C nanospheres and nanorods with little content of SiC are successfully synthesized by the KI-assisted magnesiothermic reduction from carbon coated SiO2 precursors. These novel hollow Si/C nanospheres and nanorods endow it with an excellent electrochemical performance as anodes for Li-ion battery. In detail, Si/C nanospheres achieve a specific capacity of 1792 mAh g−1 after 100 cycles at 1 A g−1, and 1271 mAh g−1 even at a high current density of 3 A g−1 after 200 cycles. This novel strategy provides an effective and facile way to reduce SiC generation during magnesiothermic reduction reaction and can be applied to obtain Si/C composites with various morphology.

Effects of Silicon Carbide (SiC) Reinforcement on the Microstructure and Mechanical Properties of Laser Deposited Al-Sn-SiC/Ti-6Al-4V Composite Coatings

Titanium and titanium alloys have a large array applications attributed to its low density, good corrosion resistance and high specific strength. Damage to the surface can be improved by surface modification for extended application. Direct laser metal deposition (DLMD) technique can be used to address the limitations associated with titanium alloy. This is mostly achieved by integration of reinforcement materials into the main matrix to form coating. Thereby inducing microstructural changes to the material. The morphology and also the hardness property of the various composite coatings were examined. The hardness of the composite coating was found to range between 450.64 and 638.22 HV, and the hardness obtained for 10% SiC reinforcement coating was 638.22 HV. For all the coatings, the hardness was established to be much higher than that of the substrate, which was averaged 304.21 HV. Hardness value increases with increase in SiC content. The enhanced hardness values were due to refined grains and intermetallics in the microstructure of the coatings. Moreover, the highest tensile and yield strengths was found at 10 wt.% SiC due to the uniform particle dispersion that can impede dislocation movement. The uniform distribution of SiC particles in the Al-Sn matrix had a good effect on its mechanical properties.

Evaluation of Microstructure, Mechanical, Thermal and Erosive Wear Behavior of Aluminum-Based Composites

In the present study, we have shown the effect of a varying content of silicon carbide (SiC, 0, 10 and 15 wt.%) on the microstructure, mechanical, thermal and erosive wear behavior aluminum alloy (LM13). The erosive wear response was thoroughly studied by the sample rotation technique using slurry pot erosion tester. The influence of critical parameters; speed, sand content and slurry environment on the wear behavior have been studied. In order to examine the influence of the SiC particle, matrix alloy was also characterized under identical conditions. The microstructural studies of the composite suggest that there is the presence of significant interaction between the matrix and SiC particles. In the composite, the SiC particles were uniformly distributed, but dispersing SiC particles eventually deteriorate the tensile and fatigue life under the present domain of experiments. The composite exhibited minimum wear rate than the matrix alloy in an acidic and saline medium, however, the matrix showed enhanced wear resistance in the basic media (when compared to that of SiC reinforced composites). The rate of material loss is found to be higher with increased sand concentration due to an increase in the impinging action of the sand particles. The study reveals that the loss of material was due to the combined effect of corrosive, erosive and abrasive actions of the slurry medium. Erosion mechanism is found to be a predominant in the acidic medium, whereas corrosion is responsible in the case of the basic medium.

The effect of silicon carbide on the mechanical and thermal behavior of spark plasma sintered silicon nitride ceramics with Al2O3 and Y203 additives

Silicon nitride-silicon carbide composite ceramics were spark plasma sintered with yttrium oxide and aluminium oxide as additives while varying the percentage weight of silicon carbide from 3 to 12%. Relative density together with Vickers hardness and fracture toughness of the material were measured. Furthermore, holes were drilled using Nd;YAG laser to investigate the thermal stability of the materials. From the results, it was observed that the relative density of the material depended highly on the silicon carbide composition with 99.997% relative density obtained at 12% silicon carbide composition. The Vickers hardness and the fracture toughness slightly increased with increase in the silicon carbide composition from 1943 HV and 8.5 MPa·√m at 3% to 1971 HV and 8.991 MPa·√m at 12%. A huge impact of the silicon carbide composition was observed with thermal behavior in a manner that as the silicon carbide content increased, the material was becoming more thermally stable in high laser energy parameters.

A study of the heat insulation performance of pre-oxidized fiber felts of silica aerogel/silicon carbide composite coatings

In this article, pre-oxidized fiber felts of silica aerogel/silicon carbide composite coatings were prepared by the coating process and then compounding silica aerogel with silicon carbide powder as the infrared sunscreen on the pre-oxidized fiber felts. The influence of the ratio of the contents of the silica aerogel and silicon carbide as the infrared sunscreen on the heat insulation performance of coating composites of pre-oxidized fiber felts was discussed, and their mechanical properties were investigated. The results show that with increasing silicon carbide content in the composite coating, the coefficient of thermal conductivity increases gradually; when the working temperatures were 100, 150 and 200 °C, the coating composites of pre-oxidized fiber felts had the best heat insulation performance when the mass ratio of the silica aerogel and silicon carbide was 4:7. The working temperature and the steady-state temperature difference of the coating composites shows a linear relationship, so simple calculation methods of the coefficient of thermal conductivity for the coating composites were given at higher temperatures.

The effect of Cu addition on wear mechanisms and tribological properties of aluminium matrix composites reinforced with SiC

The article discusses the results of research on the effect of 4 wt.% Cu addition on the tribological properties of composites based on aluminium matrix reinforced with SiC particles. The research also included the analysis of the microstructure and the hardness. The composites were made of elementary powders in a rigid die on a single-action compaction press and then sintered under the nitrogen atmosphere. The silicon carbide content was: 2.5; 5; 7.5; 10 and 15 wt.%. The tests of tribological properties were carried out using a block-on-ring T05 tester under the technically dry friction conditions, and the counter-sample was made of 100 Cr6 steel. The research covered the determination of mass losses, coefficients of friction as well as friction coefficient changes as the function of process duration and material. The obtained results proved that the addition of 4 wt.% Cu helps to reduce the friction coefficient and for composites that contain above 7.5 wt.% SiC also improves their wear resistance. It was also demonstrated that both the addition of Cu as well as an increase of SiC content in the composites have a positive effect on friction by reducing the adhesive wear share in the friction process.

Effect of Silicon Carbide (SiC) Nanoparticles on the Spectroscopic Properties and Performance of PMMA/PC Polymer Blend

Films of polymethyl methacrylate (PMMA)/polycarbonate (PC) polymer blend doped silicon carbide (SiC) nanopowder are synthesized by the casting method. The study for the structural, optical and electrical behavior of PMMA/PC blend without and with low contents (≤0.8 wt%) of SiC is done. The change of the structure is investigated from X-ray spectra. After the addition of SiC, the intensity of the main X-ray halo peak at 2θ = 20.26° of PMMA/PC is decreased, attributed to an interaction between PMMA/PC. It’s clear that SiC is causing an increase in the amorphous regions inside the PMMA/PC blend. The peaks related to SiC are not found attributed using a small amount of SiC with complete dissolution of SiC. The shift of the intensity for IR bands has supported an interaction between all components. The values of the optical band gap from UV-Vis spectra using indirect transition are decreased with the increase of SiC. The values of the electrical conductivity are low at low frequency attributed to the charge accumulation at the electrode which takes place. The conductivity is increased as the increase of frequency due to the mobility of charge carriers. Furthermore, the conductivity is increased with the increase of SiC contents. The values of ε' and ε'' are very high at the lower frequency and they decrease when the frequency is increased attributed to the effect. The plot of both Z' and Z'' shows dramatic decrease with the increase of frequency.

Evaluation of Mechanical, Microstructure and Sliding Wear Characteristics of Different Al-Zn Alloy and Composite: A Comparative Research

Plain bearings are extensively used in many engineering application. The wear loss of bearing material is the one of the major parameter that affects the performance of bearing. In this investigation, four Al-25Zn alloy samples reinforced with silicon carbide and graphite content were fabricated using stir casting technique. The mechanical properties, microstructure and sliding wear characteristics of fabricated specimens were studied. Dry sliding wear characteristic of specimens was investigated using a pin on disc tribometer with EN24 shaft steel disc at three speeds 1.0472m/s, 2.0944m/s and 3.1416m/s and three different applied pressures 0.3747MPa, 0.7584MPa and 1.1421MPa as per Taguchi L9 orthogonal array. The microstructure examinations of the worn surfaces were carried out using a scanning electron microscope (SEM). The hardness, tensile strength and wear resistance of Al-25Zn alloy with the addition of silicon carbide particles is found to be increased. The addition of graphite particles in Al-25Zn alloy enhances the wear resistance and tensile strength of the composite, in spite of the substantial decrease of hardness. The worn surfaces show the presence of delamination and abrasive wear mechanisms in the localized region.

Composite material Si3N4/SiC with calcium aluminate additive

The aim of this work was to obtain Si3N4/SiC composites, where silicon nitride served as the matrix, and the silicon carbide content varied from 3 to 50 % by weight. To reduce the sintering temperature (hot pressing) of the ceramic, a sintering additive of calcium aluminate eutectic. The charge was prepared as follows. The silicon nitride powder was mixed with 10 wt.% sintering calcium aluminate. Then the charge was added over 100 % of silicon carbide in an amount of 3, 5, 7, 10, 15, 20 and 50 % by weight in a planetary mill. Ceramic materials were obtained by hot pressing at a temperature of 1660°C, a pressure of 30 MPa, for 60 minutes in an atmosphere of N2. The highest properties were achieved on the material with 10 wt.% SiC: density of 3.16 g/cm3, bending strength 650 MPa, microhardness 22 GPa.

Polymer-Derived Nano-Sized SiC-Containing ZrB<sub>2</sub> Composites: Densification, Microstructure and Flexural Strength

Silicon carbide (SiC)-containing zirconium diboride (ZrB2) composites have become an important class of ultra-high temperature ceramic materials for the thermal protection systems of re-entry hypersonic vehicles with sharp leading edge profiles. Previous studies in ZrB2-SiC composites showed that nano-sized SiC particles-containing ZrB2 composites had a greater strength and a better oxidation resistance compared to ZrB2-beased composites with micron-sized SiC particles. However, it is difficult for obtaining a homogenous microstructural ZrB2-based composite with nano-sized SiC particles because of agglomerates of the SiC particles. In this study, homogenously dispersed nano-sized SiC particles-containing ZrB2 composites were prepared using polymer-derived SiC-dispersed ZrB2 composite powders followed by hot pressing at different temperatures between 1750°C and 1900°C. The microstructure of the resulting composites was characterized by field emission scanning electron microscopy. Four-point flexural strength of the obtained composites was measured at room temperature. The effects of the sintering temperatures and SiC content on the microstructure and the flexural strength of the composites were discussed.

An analytical model for elastic modulus calculation of SiC whisker-reinforced hybrid metal matrix nanocomposite containing SiC nanoparticles

In the present work, elastic modulus of a hybrid aluminum matrix nanocomposite (HAMNC) reinforced with silicon carbide (SiC) whiskers and SiC nanoparticles is analyzed. To this end, a new multi-scale analytical model is developed to calculate the effective elastic modulus of the HAMNC. The SiC nanoparticle aggregation into the HAMNC, frequently encountered in real engineering situations, is simulated. The elastic modulus of HAMNC estimated by the analytical micromechanical model is compared with that directly measured by the experimental method and a good agreement is found between the two sets of results. The effects of volume fraction, aspect ratio and dispersion type of SiC whiskers as well as volume fraction, size and aggregation degree of SiC nanoparticles on the HAMNC elastic modulus are extensively investigated. It is found that the elastic modulus of the SiC whisker-reinforced composite is significantly improved due to the addition of SiC nanoparticles. The results show that the nanoparticle aggregation has a damaging effect on the HAMNC elastic modulus. It is observed that the HAMNC elastic modulus can be enhanced by (i) increasing SiC content, (ii) aligning the SiC whiskers, (iii) increasing the SiC whisker aspect ratio (iv) decreasing the SiC nanoparticle size and (v) uniform dispersion of SiC nanoparticles into the hybrid nanocomposite. The reported results by means of the analytical model can be actually useful to guide design of general hybrid metal matrix nanocomposites with superior effective properties.

Effect of technological parameters on densification of reaction bonded Si/SiC ceramics

Si/SiC composite ceramics was produced by reaction sintering method in process of molten silicon infiltration into porous C/SiC preform fabricated by powder injection molding followed by impregnation with phenolic resin and carbonization. To optimize the ceramics densification process, effect of slurry composition, debinding conditions and the key parameters of all technological stages on the Si/SiC composite characteristics was studied. At the stage of molding the value of solid loading 87.5% was achieved using bimodal SiC powder and paraffin-based binder. It was found that the optimal conditions of fast thermal debinding correspond to the heating rate of 10 °C/min in air. The porous C/SiC ceramic preform carbonized at 1200 °C contained 4% of pyrolytic carbon and ∼25% of open pores. The bulk density of Si/SiC ceramics reached 3.04 g/cm3, silicon carbide content was 83–85 wt.% and residual porosity did not exceed 2%.

Branched sulfonated polyimide/functionalized silicon carbide composite membranes with improved chemical stabilities and proton selectivities for vanadium redox flow battery application

Silicon carbide (SiC) was pretreated and functionalized by using α, ω-diaminopropyl polydimethylsiloxane (PDMS) to obtain a novel inorganic filler SiC (PDMS). Then, a series of branched sulfonated polyimide/SiC (PDMS) (bSPI/SiC (PDMS)) composite membranes with different contents of SiC (PDMS) were fabricated for vanadium redox flow battery (VRFB) application. Fourier transform infrared spectra, X-ray diffraction, and field emission scanning electron microscope demonstrate the successful preparation of SiC (PDMS) and bSPI/SiC (PDMS) membranes. The thermogravimetric analysis shows that bSPI/SiC (PDMS)-1.5% membrane has better thermal stability than pure bSPI, bSPI/SiC-1.5%, and Nafion 117 membranes. The ex situ chemical stability test results show that bSPI/SiC (PDMS)-0.5–2.5% composite membranes have better chemical stabilities than pure bSPI membrane. The physicochemical properties of bSPI/SiC (PDMS) membranes, including water uptake, swelling ratio, ion exchange capacity are investigated. Thereinto, bSPI/SiC (PDMS)-1.5% membrane has the highest proton selectivity (S: 2.99 × 105 S min cm−3) and was chosen as an optimum VRFB membrane. And the VRFB assembled with bSPI/SiC (PDMS)-1.5% membrane exhibits better battery performance than that assembled with Nafion 117 membrane during 500-time cyclic charge–discharge test at 20–60 mA cm−2. Above results indicate that as-optimized bSPI/SiC (PDMS)-1.5% membrane has great potential for VRFB application.

Microwave-induced shape-memory poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks chemically linked to SiC nanoparticles

Microwave (MW)-induced shape-memory poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) interpenetrating polymer networks (SMP-IPNs) were prepared through in situ polymerization. Silicon carbide (SiC) nanoparticles were modified by 3-(methacryloyloxy) propyltrimethoxysilane (KH570). 3-(Methacryloyloxy) propyltrimethoxysilane was covalently bonded on the surface of SiC through the reaction of silanol and the methoxy groups. The polymerization of acrylic acid (AA) using N,N′-methylenebis (2-propenamide) (MBA) as cross-linker in PVA solution was initiated through the double bonds of KH-570 grafted on SiC, leading to a PAA polymer network cross-linked with MBA. The PVA molecular chains run through the PAA cross-linking network and form an IPN structure. Therefore, SiC as a strong MW absorbing material could be chemically cross-linked into polymer matrix. The effect of composition on the properties of SMP-IPN was studied using dynamic mechanical analysis, dielectric properties and shape memory effect (SME) test. The results showed that the introduction of SiC in IPNs not only provided samples with excellent MW-induced shape memory effect (SME), but also caused a higher equilibrium temperature under MW irradiation. Moreover, both SiC content and applied MW power affected the shape recovery properties of PVA/PAA interpenetrating composites. MW-induced SMPs offered great advantages such as fast recovery, high recovery rate, and remote actuation. This study provides the potential applications of the fast and environmentally friendly SMPs used as MW-responsive sensors, implantable devices, etc.

Temperature-dependent nonlinear conductivity and carrier mobility of silicone rubber/SiC composites

An electrical field distorted by the complicated cable accessory structure and non-uniform temperature distribution is a significant threat to high voltage direct current (HVDC) cable. Thus, the field grading material (FGM) with nonlinear conductivity which can uniform local field receives attention. This paper focuses on the temperature-dependent nonlinear conductivity of the FGM based on high temperature vulcanized (HTV) silicone rubber (SiR). The nonlinearity was achieved by mixing silicon carbide (SiC) particles with the SiR matrix. The conductivities of the samples were measured at temperatures of 30–90 °C. In addition, the carrier mobility and trap distribution of different samples at different temperatures were obtained by analyzing the surface potential decay (SPD). The experiment results showed that the SiR/SiC composites had nonlinear conductivity when the SiC content exceeded 30 phr in the entire temperature interval. The conductivity increased, and the threshold field of conductivity decreased at high temperature. In the SiC mixed samples, a convergence trend appeared at high field at temperatures below 70 °C. The trap distribution moved to a higher energy level, and a higher shallow trap proportion appeared at high temperature. The mobility increased with the increase in temperature. This trend became more obvious at high temperature. In addition, compared with voltage, the temperature had a more remarkable effect on the carrier mobility.

High temperature oxidation behavior of silicon carbide-carbon coated nanostructured ferritic alloy composites in air + water vapor environment

Oxidation behavior of silicon carbide (SiC) - carbon coated nanostructured ferritic alloy (C@NFA) composites was investigated in an air + 45 vol% H2O atmosphere at 500–1000 °C. All the composites show an oxidation structure with an outer Fe-rich layer and an inner Cr-rich layer, as well as internal oxidation along grain boundaries. Oxidation resistance increases with SiC addition. The corresponding fundamental mechanism is proposed. The improved oxidation resistance for the higher SiC content composites is attributed to a delay in ‘breakaway oxidation’ due to improved kinetics for the formation of dense Cr2O3 and SiO2 protective layers.

Structural, thermal, dielectric spectroscopic and AC impedance properties of SiC nanoparticles doped PVK/PVC blend

Abstract Nanocomposite films based on poly (N-vinylcarbazole)/polyvinylchloride (PVK/PVC) blend doped with different concentrations of Silicon Carbide (SiC) nanoparticles have been prepared. The X-ray diffraction, Ultra violet-visible spectroscopy, thermogravimetric analysis and electrical spectroscopic has been used to characterize these nanocomposites. The X-ray analysis confirms the semi‐crystalline nature of the films. The intensity of the main X-ray peak is decreased due to the interaction between the PVK/PVC and SiC. The main SiC peaks are absent due to complete dissolution of SiC in polymeric matrices. The UV–Vis spectra indicated that the band gap optical energy is affected by adding SiC nanoparticles because the charges transfer complexes between PVK/PVC with amount of SiC. The thermal stability is improved and the estimated values of e′ and e″ are increased with increasing for SiC content due to the free charge carriers which in turn increase the ionic conductivity of the doped samples. The plots of tan δ with frequency are studied. A single peak from the plot between tan δ and Log (f) is appeared and shifted towards the higher frequency confirmed the presence of relaxing dipoles moment.