Mullite silicon carbides

There are many types of mechanical grinding equipment available ball mills, ball and mortar sets, planetary mortars, impact mills, etc. These are available in a variety of materials steels, porcelain, agate, mullite, silicon carbide, tungsten carbide and others. Prices range from 200 to about 2,000. Unfortunately, the cost increases rather markedly as one goes to the harder materials, especially the carbides. 

Keywords, mullite, silicon carbide, porous materials, thermal shock resistance... 

K. Ando, K. Hurusawa, M. C. Chu, T. Hanagata, K. Tuji and S. Sato, Crack-healing behavior under stress of mullite silicon carbide ceramics and the resultant fatigue strength, J. Am. Ceram. Soc., 84, 2073-2078 (2001). 

Filters for Molten Metal Inclusions in molten metals, such as oxide skins, mold sand particles, inoculation reaction byproducts or furnace slags, can be efficiently removed by filtering through pressed cellular, extruded cellular, or foam ceramic filters manufactured from high-temperature-resistant, chemically inert alumina, and also mullite, silicon carbide, and stabilized zirconia. Alumina is particularly useful when filtering liquid aluminum alloys in the range of 750-850 °C, and copper-based alloys at 1000-1200°C (Matthews, 1996). These ceramic filters are designed for use in either batch or in-mold filtration ... 

Use of the ceramic honeycomb packing structure in the recuperator keeps fuel and air substantially isolated as they travel through the recuperator. Various ceramic materials such as cordierite, mullite, alumina and silicon carbide can be used to fabricate honeycomb beds. While metallic materials have the potential to be used in honeycomb bed, corrosion resistance is a major issue... 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

Some of the most common combinations used in the development of new ceramic composites involve the use of silicon carbide, silicon nitride, aluminum oxide, silicon dioxide, and mullite (a form of aluminum sulfate (Al2[S04]3). Each of these compounds can he used either as the reinforcement or as the matrix in a composite. 

Silicon carbide (SiC), boron carbide (B4C), titanium carbide (TiC) Mullite (3AI203.2Si02), spinel (Mg0.AI203)... 

Toropov and Leszczynski [67] also predicted the Young s modulus for metal oxides, nitrides, mullite, and silicon carbide by using a DCW descriptor defined as follows ... 

The descriptor was a product of the correlation weights, CW(Ik), calculated by the Monte Carlo method for each kth element of a special SMILES-like notation introduced by the authors. The notation codes the following characteristics the atom composition, the type of substance (bulk or not, ceramic or not), and the temperature of synthesis. The QSAR model constructed in this way was validated with the use of many different splits into training (n 21) and validation (n=8) sets. Individual sub-models are characterized by high goodness-of-fit (0.972 applicability domain of the model, it is not known if all the compounds (metal oxides, nitrides, mullite, and silicon carbide) can be truly modeled together. 

Materials such as aluminum titanate and silicon carbide appear to be promising for high-temperature catalytic combustion. However, problems such as extrudability, the application of washcoats, and reaction with deposited washcoats are not solved yet. For instance, when hexa-aluminate, presented in the introduction to this section, was applied to silicon carbide monoliths, solid-state reactions occurred at 1200-1400 C [76], causing exfoliation of the coating and the formation of new phases. The application of an intermediate mullite layer was suggested as an approach to hinder these solid-state reactions. 

Different supports are used, (see Section 10.6.4) with different geometry (discs or tubes), thickness, porosity, tortuosity, composition (alumina, stainless steel, silicon carbide, mullite, zirconia, titania, etc.), and symmetry or asymmetry in its stmcture. Tubular supports are preferable compared to flat supports because they are easier to scale-up (implemented as multichannel modules). However, in laboratory-scale synthesis, it is usually found that making good quality zeolite membranes on a tubular support is more difficult than on a porous plate. One obvious reason is the fact that the area is usually smaller in flat supports, which decreases the likelihood of defects. In Figure 10.1, two commercial tubular supports, one made of a-alumina (left side) and the other of stainless steel (right side) used in zeolite membrane synthesis, are shown. Both ends of the a-alumina support are glazed and both ends of the stainless steel support are welded with nonporous stainless steel to assure a correct sealing in the membrane module and prevent gas bypass. 

They are normally cast in the form of brick and are sometimes bonded to assure stability. The outstanding property of these materials is their ability to act as insulators. The most important are fireclay (aluminum silicates), silica, high alumina (70-80% ALjOj), mullite (clay-sand), magnesite (chiefly MgO), dolomite (CaO-MgO), forsterite (MgO-sand), carbon, chrome ore-magnesite, zirconia, and silicon carbide. (2) Characterizing the ability to withstand extremely high temperature, e.g., tungsten and tantalum are refractory metals, clay is a refractory earth, ceramics are refractory mixtures. 

A similar reaction route has been developed for reaction bonded mullite (RBM, aluminum silicate). In this case the powder formulation also includes a source of silicon (silicon metal, silicon carbide, or silica), in addition to aluminum metal and alumina, and the final product contains mullite as the major phase. The RBM process is frequently modified by additions of zircon (ZrSi04), which provide an additional source of silicon and result in a dispersion of fine zirconia particles in the product which restricts grain growth to ensure a fine uniform microstructure. It is again possible to reduce residual porosity while retaining the near-net-shape characteristics, but at the time of writing this process is still under development and some way from commercial exploitation. 

The fibers typically consist of carbon (C), silicon carbide (SiC), alumina (AI2O3), or mullite (Al203-Si02). For the matrix components, alumina, zirconium oxide, and silicon carbide are most commonly used. The terminology of CMC usually follows the principle t3q>e of fiber/t3q>e of matrix. C/SiC stands for a carbon-fiber-remforced silicon carbide. Today, the most important CMCs are C/C, C/C-SiC, C/SiC, and SiC/SiC. In some cases, the term is preceded with the abbreviation of the manufacturing process. 

Long-term oxidation protection requires multilayer protection coatings, where the car-bon/carbon or carbon/silicon carbide composite is protected for example with SiC layers and additional self-healing glass forming layers, based on oxides like mullite, alumina... 

A. Zangvil, C.-C. Lin, and R. Ruh, Microstructural Studies in Alkoxide-Derived Mullite/Zirconia/Silicon Carbide-Whisker-Composites, /. Am. Ceram. Soc., 75 [5] 1254-65 (1992). 

A. Hynes, R. H. Doremus, R. Ruh, Y. Xu, and A. Zangvil, Creep of Mullite Composites Containing Zirconia and Silicon Carbide Whiskers pp. 509-21 in Advances in Ceramic Matrix Composites III, Ceramic Transactions, Vol. 74. Edited by N. P. Bansal and J. P. Singh. The American Ceramic Society, Westerville, OH, 1996. 

IN-SITU REACTION SINTERING OF POROUS MULLITE-BONDED SILICON CARBIDE, ITS MECHANICAL BEHAVIOR AND HIGH TEMPERATURE APPLICATIONS... 

The present study aims at investigating the Reaction Bonded Silicon Carbide (RBSC) process to produce porous mullite-bonded SiC ceramics. Wu and Claussen (1991) reported a technique to produce mullite ceramics starting from Al, SiC and AI2O3 powder mixtures. However for the purpose of this study it was decided to use only SiC and Al 03 as the precursor powders with SiC as the major component so that after completion of the reaction the microstructure would be SiC bonded with mullite phase, with no residual alumina. This material was then tested for its mechanical properties like Young s modulus. Modulus of Rupture. Properties of Silicate-based SiC refractories have been reported to a certain extent by Reddy and others. Its potential use as a refractory material has been evaluated by measuring its thermal shock resistance. A sample refractory that has been designed in the... 

In-Situ Reaction Sintering of Porous Mullite-Bonded Silicon Carbide... 

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