Powder Silicon Carbide Research Articles

Taguchi Optimization of Fracture Toughness of Silicon Carbide Extracted from Agricultural Wastes

In India, agricultural wastes such as palm ash and rice husk, which are abundant which have a high potential for usage as usable renewable energy and silica. Silicon carbide (SiC) is utilized for various applications due to its high hardness, compressive strength, and good wear resistance. In this work, a cleaner and green methodology was adopted to produce SiC from various agricultural wastes like peanut shells, rice husks, sugar cane extracts, and corn cob. Pyrolysis experiments were carried out by varying parameters such as heating temperature (600 to 800 °C), heating time (160 to 180 min), and quantity of waste (450 to 550 g) to convert agricultural wastes into powder SiC. X-ray diffraction, Raman, Fourier transform infrared spectroscopy and Scanning electron microscope confirms the formation of SiC phase in SiC. The sintering process parameters such as heating rate (5 to 15°C/min), cooling rate (5 to 15 °C/min), and pressure (60 to 80 MPa) were selected for finding fracture toughness of sintered SiC. The process parameters for the pyrolysis and sintering process were optimized by the Taguchi optimization technique. Confirmations tests were conducted with optimum process parameters and the results indicated that confirmations results are correlated with predicted results.

Effect of MWCNTs on Improvement of Fracture Toughness of Spark Plasma Sintered SiC Nano-Composites

Background: Silicon carbide (SiC) ceramics are promising engineering material due to its phenomenal properties, such as strong corrosion resistance, high-temperature hardness, wear resistance, high thermal conductivity and high stability in aggressive environment. The key problem of SiC is low fracture toughness due to its brittle nature and to circumvent this, herein high ductile material like MWCNT was used as reinforcement by different proportions. Methods: Nanocrystalline powdered Silicon Carbide (SiC) of particle size of 40 nm and x % weight ratio of SiC (x = 95%, 90% and 85%) + y % weight ratio of multiwalled carbon nanotubes (MWCNTs) of particle size of 20 nm (y= 5%, 10% and 15%) composites were ball milled and fabricated using spark plasma sintering process with temperature rate of 100 oC/min and external pressure of 50 MPa. The sintered samples were tested according to ASTM standards to verify the mechanical properties of the samples. Further, lattice strain, crystalline size was determined by XRD and crack bridging mechanism was studied by FESEM. Results: It was observed that the uniform distributions of MWCNTs were achieved through ultrasonication and ball milling processes, which play a predominant role in increasing fracture toughness. The fracture toughness of the composite improves drastically from 3.71 MPa m1/2 (100% SiC) to 10.21 MPa m1/2 (85% SiC-15% MWCNT). The theoretical and relative densities of the materials were gradually reduced due to the increase in MWCNTs which is due to the lower density of the reinforcement material and an increase in porosity of the samples. Conclusion: The MWCNTs act as a bridging aid in sintered samples, FESEM image signifies some pull-outs and crack branching mechanism of MWCNTs which is the reason for increase in the fracture toughness of SiC.

Low temperature gas-phase technology cladding powdered silicon carbide

Low temperature gas-phase technology cladding powdered silicon carbide

New Unconventional Additives in Concrete Technology for Expansion its Functionality

Functional enhancement of concrete, giving it heat-resistant properties becomes possible while adding mill ground additions based on silicon carbide materials of the region. The selection of silicon carbide waste and secondary production materials as a filler for the production of concrete with heat-resistant properties was based on the following principles: dispersion, the chemical composition, phase composition that reflect the chemical activity of the material in relation to the concrete binder. The thermal resistance of concrete has increased fivefold. In forming concrete structures with addition of silicon carbide occurs embedding into the structure of hydrates fine powder silicon carbide cyclone dust, with the chemical processes behaviour in the boundary contact zone between binder and filler. The increase of thermal resistance can attribute the resulting concrete composition to the category of heat-resistant concretes, and that significantly expands the functionality of concrete.

Microwave Flash Pyrolysis

In a microwave reactor, graphite heats rapidly to high surface temperatures; applications of graphite thermal "sensitization" have been described previously. We report here that microwave thermal sensitization with graphite, carbon nanotubes, or silicon carbide can be used to carry out reactions more typically accomplished by flash vacuum pyrolysis (FVP) and which usually require temperatures much higher than the nominal limit of a microwave reactor. The graphite-sensitized microwave reaction of azulene in the solid phase at temperatures of 100 to 300 degrees C affords rapid rearrangement to naphthalene, a reaction typically observed by FVP at 700-900 degrees C. Multiwall carbon nanotubes give similar results when used as a thermal sensitizer. Other graphite-sensitized reactions that we have observed include the following: conversion of 2-ethynylbiphenyl to phenanthrene, fragmentation of phthalic anhydride to benzyne, cleavage of iodobenzene to phenyl radical, aryl-aryl bond cleavage, and a variety of cycloaromatizations. An advantage is seen for less volatile substrates. Rearrangement of azulene and generation of benzyne from phthalic anhydride have also been observed on powdered silicon carbide. Because of the high temperature, rapid heating, and frequent ejection of material from the irradiation zone, we refer to this general method as microwave flash pyrolysis (MFP).

Solid-state 13C and 29Si MAS NMR spectroscopy of silicon carbide

The solid-state NMR spectroscopy of bulk and powdered silicon carbide, silicon carbide fibers, and materials fabricated with silicon carbide fibers is discussed. Specifically, the NMR spectroscopy of fiber mats indicates that the fabrication process produces silicon-carbon oxides and certain structural changes that are evident as small shifts of the resonances.

A new electrothermal vaporization device for direct sampling of ceramic powders for inductively coupled plasma optical emission spectrometry

In spite of many important advantages of electrothermal vaporization of solid samples combined with inductively coupled plasma spectrometry (ETV-ICP-OES) the method has not been exploited to its full potential as a routine analysis mainly due to unsatisfactory reproducibility. The design of the system which transports the analytes into the plasma is recognized as one of the main factors influencing effective transport. Development of a reliable means of combining an ETV device with an ICP would be very useful when direct analysis of trace elements in ceramic powders is needed. This paper describes the construction of an ETV-ICP system for direct analysis of ceramic powders through in situ thermochemical processing. The system is based on in-line electrical resistive heating of a graphite crucible with powdered silicon carbide mixed with a CoF 2 + BaO modifier in a proportion 1 : 1 : 1. The transport path was shortened to 9 mm from the orifice of the crucible to the bottom of a modified injector tube. No material was deposited on the injector tube based on washing the tube and analyzing the solution by ICP-OES. Initial assessment by peak area integration of emisison signals of 5 mg silicon carbide powder shows that the level of detection lies approximately in pg level for Ti, V, Al and Fe. The system has no memory effect. The ETV unit could be used both by ETV-ICP-OES and ETV-ICP-MS.

Direct determination of impurities in powdered silicon carbide by electrothermal atomic absorption spectrometry using the slurry sampling technique

A direct method of analysis of powdered silicon carbide for the determination of Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Ti, V and Zn based on electrothermal atomic absorption spectrometry (ETAAS) using the slurry sampling technique is described. Possible spectral interferences caused by the refractory matrix components were studied. The technique was optimized with regard to sample preparation, dispensing, thermal pre-treatment and atomization parameters. The accuracy was checked by comparison of the results with those obtained by ETAAS and inductively coupled plasma atomic emission spectrometry involving decomposition of the sample, and by instrumental neutron activation analysis. For most of the elements investigated the achievable limits of detection are at the sub-microgram per gram level.

Acid resistance ofα- andβ-SiC

Powdered silicon carbide of theα- andβ-modifications obtained by crushing pure single crystals of this compound, do not decompose under the action of HF and mixtures of HF, sulfuric, and nitric acids, and in terms of resistance to these reagents, are exactly the same. Information of the low stability ofβ-SiC in these acids [1] apparently is due to the low quality of the product investigated.