Features of formation of composite ceramics from SiC-Si-Mo at high pressure (original) (raw)
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Ultra-high pressure densification and properties of nanostructured SiC
Materials Letters, 2016
Cubic SiC nano-powder particles were synthesized by a sol-gel process with an average grains size of 9.5 nm which were subsequently densified by using a high-pressure "anvil-type with hollows" apparatus at a pressure of 4 GPa in order to obtain nanostructured bulk ceramic compacts. The density obtained was 4 98% at a sintering temperature of 1500°C with a holding time of only 60 s. The calculation of the average crystallite size (D) was performed on the basis of the full width at half maximum intensity (FWHM) of the XRD peaks. Williamson-Hall plots were used to separate the effect of the size and strain in the nanostructured SiC compacts. Sintered nanostructured SiC ceramic exhibits hardness and elastic modulus of 32-420 GPa respectively. Wear properties were investigated and the average value of dynamic friction coefficient obtained was 0.16.
Micro-Structural Characterization of Si-SiC Ceramic Derived from C/C-SiC Composite
American Journal of Materials Science, 2012
The main objective of the present work is to processing the porous Si-SiC ceramic by the oxidation of C/C-SiC composite. Phase studies are performed on the oxidized porous composite to examine the changes due to the high temperature oxidation. Further, various characterization techniques are performed on Si-SiC ceramic in order to study the material's microstructure.
Journal of the European Ceramic Society, 2012
The heat treatment of SiC powders, SiC-2 mol% SiO 2 powder mixtures, and bimodal SiC powder mixtures has been studied with a quadrupole mass spectrometer linked by capillary tube to a special heat treatment reactor. Silica release was monitored on the CO(g) vaporized flow and the samples were analyzed by Raman spectroscopy and Scanning Electron Microscopy after the experiments. The present study showed that silica release by vaporization-first step in heating processes-is needed before any SiC growth process could start. The second step involving active SiC oxidation conditions by the remaining oxygen was conducive to the growth of "neck-like" connections between SiC grains and growth process was observed in the 1273-1600 K range. When the CO(g) release decreased as a result of higher temperatures or longer treatment times, carbon precipitation at the SiC surface was observed as the third step in the mass loss process.
Current status and recent research achievements in SiC/SiC composites
The silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) composite system for fusion applications has seen a continual evolution from development a fundamental understanding of the material system and its behavior in a hostile irradiation environment to the current effort which is directed at a broad-based program of technology maturation program. In essence, over the past few decades this material system has steadily moved from a laboratory curiosity to an engineering material, both for fusion structural applications and other high performance application such as aerospace. This paper outlines the recent international scientific and technological achievements towards the development of SiC/SiC composite material technologies for fusion application and discusses future research directions. It also reviews the materials system in the larger context of progress to maturity as an engineering material for both the larger nuclear community and broader engineering applications.
SYNTHESIS OF A CERAMIC COMPOSITE MATERIAL: SiC-(W,Mo)Si2
The presence of residual silicon in RBSC pieces reduces their mechanical properties at temperatures higher than 1300 ºC (mp of Si = 1410 ºC). This work presents the study of the substitution of silicon by a refractory silicide (W,MoSi 2 ). The preparation variables have been the carbon source (activated carbon, graphite and coke), the particle size and the experimental conditions used. The best results were obtained when a coke of small particle size was used; in this case, even the preparation of pieces of only SiC-Coke (without using of silicide precursor) with no residual silicon was possible. The use of silicide precursor in the preforms allows the synthesis of SiC-(WMo)Si 2 pieces that have no residual silicon. In all cases the mechanical properties of pieces are enhanced when silicon is replaced by silicide.
Journal of the Ceramic Society of Japan, 2010
Influence of SiC composition with different particle size on mechanical properties and microstructure of reaction-bonded SiC have been investigated using infiltration process of liquid Si. SiC specimens were prepared by reaction-bonding sintering at 1620°C in vacuum using different SiCC composition. Reaction-bonded SiC specimens show dense with 3.03.05 gr/cm 3 of density. SiC specimens with bi-modal SiC composition show a fine microstructure than those of uni-modal SiC composition. In addition, in the specimens with bi-modal SiC composition, the microstructure of the sample with use of fine SiC starting powders is finer rather than those of use of relatively coarse SiC starting powders. The flexural strength and fracture toughness of specimens with bi-modal SiC composition are higher than those of uni-modal SiC composition. The main fracture mode of specimens with a high strength is intergranular fracture.
Status and prospects for SiC SiC composite materials development for fusion applications
Silicon carbide (SIC) composites are very attractive for fusion applications because of their low afterheat and low activation characteristics coupled with excellent high temperature properties. These composites are relatively new materials that will require material development as well as evaluation of hermiticity, thermal conductivity, radiation stability, high temperature strength, fatigue, thermal shock, and joining techniques. The radiation stability of SIC-SIC composites is a critical aspect of their application as fusion components and recent results will be reported. Many of the non-fusion specific issues are under evaluation by other ceramic composite development programs, such as the US national continuous fiber ceramic composites.