Synthesis Of Silicon Carbide Research Articles

Low-temperature mechanochemical synthesis of nanosized silicon carbide

The methods of X-ray diffraction analysis, scanning electron microscopy, synchronous thermal analysis, and adsorption are used to study the mechanochemical synthesis of silicon carbide through the reaction Si + C → β-SiC. The reaction is found to take place in several stages. At the first stage, i.e., at activation doses below approximately 5 kJ/g, the powders of the components are independently ground to increase the specific surface area of the mixture to 145 m2/g, graphite is amorphized, and the sizes of the coherent-scattering regions of silicon drastically diminish. At the second stage (doses of 5–15 kJ/g), dense Si/C aggregates are formed and two fractions (coarse and fine) with different particle sizes arise in silicon crystallites. As the activation dose is enhanced, the amount of the fine fraction rises, while the sizes of coherent-scattering regions decrease to 2–3 nm. When samples are heated at 800°C, the fine fraction of silicon interacts with carbon to yield silicon carbide with crystallite sizes of 3–4 nm, whereas the coarse fraction of silicon recrystallizes. At the third stage, i.e., at doses of higher than 15 kJ/g, the mechanochemical synthesis of SiC occurs through the following scheme: fine fraction Si + C → amorphous SiC → crystallization of SiC.

Ion-beam synthesis and photoluminescence of SiC nanocrystals assisted by MeV-heavy-ion-beam annealing

This work explored a novel way to synthesize silicon carbide (SiC) nanocrystals for photoluminescence. Carbon ions at 90keV were implanted in single crystalline silicon wafers at elevated temperature, followed by irradiation using xenon ion beams at an energy of 4MeV with two low fluences of 5×1013 and 1×1014ions/cm2 at elevated temperatures for annealing. X-ray diffraction, Raman scattering, infrared spectroscopy and transmission electron microscopy were used to characterize the formation of nanocrystalline SiC. Photoluminescence was measured from the samples. The results demonstrated that MeV-heavy-ion-beam annealing could indeed induce crystallization of SiC nanocrystals and enhance emission of photoluminescence with violet bands dominance due to the quantum confinement effect.

Numerical Simulation Analysis of Temperature Field on Silicon Carbide Synthesis Furnace

Based on heat percolation theory and thermal coefficient equation of various layer-compositors, the effective thermal conductivity of silicone carbide（SiC）synthetic material was obtained, and the effective heat capacity under the complicated thermal effect in the process of raising temperature figured out in the present investigation. Based on the experimental results and using the finite element numerical model of nonlinear dynamic heat transfer process, the temperature field in SiC synthesis furnace was simulated by open source finite element software-FECsoft. And the dynamic laws of temperature distribution and thermal gradient of the furnace, the relation between the furnace core’s temperature and the energy consumption and output were obtained. Based on the above analysis, some measures to save energy and increasing output of the silicon carbide synthesis furnace were proposed in this paper.

Simulation and Optimization on Silicon Carbide Synthesis Furnace Power Curve

Based on the analysis of production process in three phases and finite element analysis of silicon carbide (SiC) furnace temperature field, 2D thermal-seepage coupled finite element model was built to know production practical situation by temperature distribution and pressure distribution. The relation of SiC furnace inside pressure and power was obtained by pressure distribution as well. Then this paper built power curve optimization model that minimizing product energy consumption is objective function with extreme pressure of spouting as one constraint condition, and simplified optimal algorithm plan was proposed based on three production phases. To verify the optimization results, the powers of before optimization and after optimization were employed on the basis of actual industrial furnace data. Results show that energy consumption decreases about 5% and the SiC output increases about 10%. Besides, production period is nearly unchanged after optimization. All stated illustrate the effectiveness of the proposed method.

SILICON CARBIDE NANOWIRES FROM POLYVINYL ALCOHOL/SILICA ELECTROSPUN NANOFIBERS

The catalyst-free synthesis of silicon carbide (SiC) nanowires was carried out from polyvinyl alcohol (PVA)/silica electrospun nanofibers at high temperature. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and thermogravimetery analysis (TGA) were employed to study morphology and formation of SiC nanowires. Based on the TGA analysis, the carbon yield was increased when inert gas flow rate and heating rate decreased and polymeric nanofibers has been stabilized. The XRD and TEM results showed that the produced nanowires were crystalline β- SiC and rather homogeneous in thickness with an average diameter around 50 to 70 nm and a length of more than 10 μm. Finally, a possible growth mechanism of β- SiC nanowire based on a vapor–solid (VS) mechanism was proposed.

Synthesis and Characterization of Crystalline Silicon Carbide Nanoribbons

In this paper, a simple method to synthesize silicon carbide (SiC) nanoribbons is presented. Silicon powder and carbon black powder placed in a horizontal tube furnace were exposed to temperatures ranging from 1,250 to 1,500°C for 5–12 h in an argon atmosphere at atmospheric pressure. The resulting SiC nanoribbons were tens to hundreds of microns in length, a few microns in width and tens of nanometers in thickness. The nanoribbons were characterized with electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy, and were found to be hexagonal wurtzite–type SiC (2H-SiC) with a growth direction of . The influence of the synthesis conditions such as the reaction temperature, reaction duration and chamber pressure on the growth of the SiC nanomaterial was investigated. A vapor–solid reaction dominated nanoribbon growth mechanism was discussed.

Synthesis and properties of porous SiC ceramics

Porous silicon carbide (SiC) ceramics are produced using carbon matrices derived from natural wood. Such material is especially promising as it is environmentally friendly with attractive physical properties, including a high level of biocompatibility, chemical inertness, and mechanical strength. We have developed a forced impregnation process with further synthesis of SiC using natural wood as well as a variety of industrial carbon materials and compared the properties of these ceramics. The structure and composition of the materials obtained were investigated by Raman scattering spectroscopy. The hardness of the samples was estimated using the Vickers technique. It was shown that the phase composition and mechanical properties of synthesized SiC ceramics can be effectively controlled by the initial Si contents and temperature of the synthesis process. A large variety of options are demonstrated for materials development taking into account an optimal porosity selection for various practical applications.

Effects of Starting Carbon Sources on the Carbothermal Synthesis of SiC Powders

Silicon carbide (SiC) powders have been prepared at 1200–1500°C by carbothermal reduction of two kind precursors of carbonl/silica mixtures: coked rice husk with high-carbon content, and gasified rice husk with low-carbon content mixed with carbon powders as an external carbon sources. The differences in nature of carbon matter in the external source and coked rice husk, and their effect on SiC synthesis have been studied by TG-DSC, TEM, XRD and laser diffraction technique. Experimental results show that the difference in nature of carbon source may affect the formation of SiC powders. The characteristics of the synthesized SiC particles strongly depend on the characteristics of the carbon sources.

Nanosized Silicon Carbide Obtained from Rice Husks

Two ways to obtain nanosized silicon carbide (SiC) powders from the products of thermal decomposition of rice hulls and posterior thermal and chemical treatment of SiO2-C precursors are shown in the present paper. The reagents and products were analyzed using BET, DTA, IR, XRD and SEM/TEM. Precursors obtained from rice husks containing pure SiO2 and a controlled SiO2-C ratio were used for the synthesis of SiC. The synthesis of SiC proceeded for 30-45 min in a graphite heater furnace under protective Ar atmosphere at relatively low temperatures (1450oC-1550oC). Nanosized dimensions of reagents obtained from rice husks and their high activity allow obtaining SiC in relatively milder thermal regimes. TEM and XRD analysis revealed synthesis of nanostructured mainly β-SiC with a mean crystallite size of 40-100 nm. Due to their purity and nano-scale properties, the products obtained are appropriate for production of bulk SiC or design of SiC–based ultra high-temperature materials using the methods of powder metallurgy.

English

The outer part of a tire is called tread. It can be manufactured by using styrene butadiene rubber. Here polystyrene is used for tire manufacturing due to its attractive properties when compared with styrene butadiene rubber. Silicon carbide synthesis is done by sol gel processing by using two different carbon precursors, called chitosan and graphin. Tetra ethyl ortho silicate is used as silicon precursor. Sol gel process needs 24hr aging of sol gel in the furnace at a temperature of 700 0 C. The characterization of silicon carbide nanoparticles is done by UV-visible spectrometer and Nanoparticle analyzer. The graph were obtained for two different samples using UV-visible spectrometer. The software used here is called WinASPECT PLUS. Particle size of the sample is analyzed by Nanoparticle Analyzer. The particle size of the silicon carbide is found that 14.7nm. After analyzing the samples, the samples were dried for the purpose of polystyrene thin film casting. Polystyrene film was formed by thin film casting method. Three samples were prepared for the testing, one is without adding silicon carbide and remaining two samples prepared by adding silicon carbide. The reagents used for polystyrene film are crystal polystyrene and benzene. Benzene has the ability to evaporate and thin film is formed.

Influence of mechanical activation on combustion synthesis of fine silicon carbide (SiC) powder

The influence of mechanical activation of powder mixtures of Si and C, via high energy attrition milling (up to 12 h), on combustion synthesis of SiC was experimentally investigated. β-SiC fine powder was successfully fabricated in 1.0 MPa N 2 atmosphere without other additional treatments, such as preheating, electric action, or chemical activation. Relatively weak peaks of α-SiC, α-Si 3N 4 and Si 2ON 2 were also found in the final products. The experimental results and their theoretical treatment showed that mechanical activation via high energy ball-milling provides to the initial Si/C powder mixture extra energy, which is needed to increase the reactivity of powder mixture and to make possible the ignition and the sustaining of combustion reaction to form SiC.

Combustion synthesis of silicon carbide assisted by a magnesium plus polytetrafluoroethylene mixture

In this study, the use of SiC combustion synthesis for immobilization of 14C was considered. Due to the low exothermicity of the reaction between silicon and graphite, a highly exothermic mixture (magnesium and polytetrafluoroethylene) was used both as a chemical oven and activate additive in the mixture. With this configuration the reaction between graphite and silicon was initiated and propagated on the whole sample. The self-propagating high temperature synthesis samples were characterized by using scanning electron microscopy and X-ray diffraction.

Synthesis of silicon carbide by exposure to solar radiation

Investigated is the possibility of synthesis of cubic silicon carbide from silica earth minerals (quartzite and quartz sand) by exposure to intense solar radiation. The influence of the intensity of the solar radiation flux on the silicon carbide formation process is studied in detail.

Synthesis of SiC Nanoparticles by Template Confined Method

A template confined method was selected to synthesize silicon carbide(SiC) nanoparticles(NPs),where ordered mesoporous silica molecular sieve SBA-15 was chosen as the template and sucrose as the carbon source.Experimental results show that the carbothermal reduction temperature and heating rate are the key parameters on synthesizing SiC NPs.Lower temperature,higher heating rate and shorter reaction time are beneficial to SiC NPs formation,whereas higher temperature,lower heating rate and longer reaction time lead to the formation of SiC nanowires.SiC NPs are obtained at carbothermal reduction temperature of 1400℃ and 75℃/min heating rate.The unique property of SiC NP provides new opportunities for the exploitation of SiC materials.It might substitute the traditional material to work in the rigorous environments.

Formation of silicon carbide and diamond nanoparticles in the surface layer of a silicon target during short-pulse carbon ion implantation

Synthesis of silicon carbide and diamond nanoparticles is studied during short-pulse implantation of carbon ions and protons into a silicon target. The experiments are carried out using a TEMP source of pulsed powerful ion beams based on a magnetically insulated diode with radial magnetic field Br. The beam parameters are as follows: the ion energy is 300 keV, the pulse duration is 80 ns, the beam consists of carbon ions and protons, and the ion current density is 30 A/cm2. Single-crystal silicon wafers serve as a target. SiC nanoparticles and nanodiamonds form in the surface layer of silicon subjected to more than 100 pulses. The average coherent domain sizes in the SiC particles and nanodiamonds are 12–16 and 8–9 nm, respectively.

Synthesis of SiC Based Fibers with Continuous Pore Structure by Melt- Spinning and Controlled Curing Method

Silicon carbide (SiC) based fibers with continuous pore structures were synthesized by the precursor method using a polycarbosilane (PCS) and polymethylhydrosiloxane (PMHS) polymer blends. The pore formation process can be explained by hydrogen gas dissolution in the polymer melt and desaturation process of the dissolved gas during the fiber spinning. We investigated the effect of PMHS additives with different chemical and physical natures on the obtained pore structures, because PMHS decomposition process played a role of hydrogen gas source. The individual polymer melts were characterized by viscosity measurement, gas chromatograph analysis and thermogravimetric (TG) analysis in order to obtain details of pore structure control.

Low Temperature Synthesis of Silicon Carbide Inert Matrix Fuel (IMF)

AbstractA process for the synthesis of silicon carbide (SiC) inert matrix fuels at a low temperature (1050 °C) is reported which utilized a liquid polymer precursor. As the polymer content increased, the theoretical density of the pellet at first increased and then reached a plateau. From the onset of the plateau, the packing of the one micron SiC particles in the green body was determined to be 64-68% at 600 MPa pressing pressure. As expected, mixing coarse and fine SiC particles gave a higher pellet density. The maximum density achieved was 80% of the theoretical density. Mercury porosimetry showed that the largest pore size was around 10% of the largest particle sizes present in the green body. SEM images showed that ceria, which was selected as a surrogate for PuO2 in the present study, was well distributed.

Synthesis of Non-Oxide Ceramic Fine-Powders from Organic Precursors

Synthesis of titanium carbide ceramic powders and control of particle size were tried by carbothermic reduction of a precursor, comparing synthesis of silicon carbide from a precursor. Metal alkoxides were used as a metal source and phenolic resin was done as a carbon source. Homogeneous sol-like mixture was obtained by mixing ethylsilicate and phenolic resin with alcohol. Gel-like precursor was formed by drying the sol-like mixture. Precipitation was formed by mixing titanium(IV) tetraisopropoxide and phenolic resin. The precursor was amorphous and ceramization occurred by heat treatment in argon flow. Growth of particles and phase formation were investigated.

Mathematical description of thermophysical processes in silicon-carbide materials synthesis in large solar furnace

A model is proposed and calculations are performed for thedescription of the technological processes in silicon carbide synthesis from organic raw materials under exposure to concentrated solar radiation.

Synthesis of silicon carbide in a nitrogen plasma torch: rotational temperature determination and material analysis

Experiments on silicon carbide synthesis were performed using a dc nitrogen plasma torch. Measurements of rotational temperature of nitrogen molecules by emission spectroscopy were performed, based on the band (0, 1) of the first negative system of nitrogen for the R branch. Three different plasma torch powers were studied in order to optimize the production of silicon carbide with our experimental set-up. The synthesized products were characterized by x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy.