Alumina silicon carbides

High -performance engineering ceramics Diamond Dense alumina Silicon carbide Silicon nitride Zirconia Sialons... 

Note The principal reinforcement, with respect to quantity, is glass fibers, but many other types are used (cotton, rayon, polyester/TP, nylon, aluminum, etc.). Of very limited use because of their cost and processing difficulty are whishers (single crystals of alumina, silicon carbide, copper, or others), which have superior mechanical properties. 

Abrasive modifiers are used in several types of friction materials. Very hard materials such as alumina, silicon carbide, and kyanite [1302-76-7] are used in fine particle sizes in organic, semimetallic, and cermet materials that are generally less than 74 im (200 mesh). Particle size is limited by the fact that large particles of such hard materials would groove cast-iron mating surfaces. Larger particle sizes are possible for harder mating surfaces in the special steel rotors used with sintered materials. 

These comments on whiskers apply roughly equally to alumina, silicon carbide, and silicon nitride, the three types on which the most work has been done. 

Meschke, F., Alves-Riccardo, P., Schneider, G.A. and Claussen, N. Failure behavior of alumina and alumina/silicon carbide composites with natural and artificial flaws , J. Mat. Res. 12 (1997) 3307-3315. 

Wu, H.Z., Roberts, S.G. and Derby, B. Residual stress and subsurface damage in machined alumina and alumina/silicon carbide nanocomposite ceramics , Acta Mater. 49 (2001) 507-517. 

Hoffman, M., Rodel, J., Stemitzke, M. et al., Fracture toughness and subcritical crack growth in alumina/silicon carbide nanocomposites , Fracture Mechanics of Ceramics, 1996, 12 179. 

Collin, K.M., Rowcliffe, D.J. (2001), Influence of thermal conductivity and fracture toughness on the thermal shork resistance of alumina-silicon-carbide-whisker compositer Journal of the American Ceramic Society, 84(6), 1334—1340. 

Maensiri, S., Roberts, S.G. (2002), Thermal shock resistance of sintered alumina/silicon carbide nanocomposites evaluated by indentation techniques , J. Am. Ceram. Soc., 85(8), 1971-1978. 

Care has to be taken in selecting materials for the die and punches. Metals are of little use above 1000 °C because they become ductile, and the die bulges under pressure so that the compact can only be extracted by destroying the die. However, zinc sulphide (an infrared-transparent material) has been hot pressed at 700 °C in stainless steel moulds. Special alloys, mostly based on molybdenum, can be used up to 1000 °C at pressures of about 80 MPa (5 ton in-2). Alumina, silicon carbide and silicon nitride can be used up to about 1400 °C at similar pressures and are widely applied in the production of transparent electro-optical ceramics based on lead lanthanum zirconate as discussed in Section 8.2.1. 

L. X. Han and S. Suresh, High Temperature Failure of an Alumina-Silicon Carbide Composite under Cyclic Loads Mechanisms of Fatigue Crack-Tip Damage, J. Am. Ceram. Soc., 72[7], 1233-1238 (1989). 

Many nonoxide ceramics form gaseous reaction products when oxidized. For example, when an alumina/silicon carbide composite is exposed to an oxidizing environment, SiC will oxidize, forming carbon monoxide via the following reaction ... 

Glass, Carbon, organic fibers, Alumina, Silicon Carbide]... 

Refractoriness (Melting Temperature). Instantaneous grinding temperatures may exceed 3500°C at the interface between an abrasive and the workpiece being ground (14). Hence melting temperature is an important property. Additionally, for alumina, silicon carbide, B4C, and many other materials, hardness decreases rapidly with increasing temperature (7). Fortunately, ferrous metals also soften with increasing temperatures and do so even more rapidly than abrasives (15). 

Narcarb. [NortiiAirtR actories] Resin bonded alumina silicone carbide plastics and ram mixes. 

Ramak. [Ntxth Am. Refractories] Pitch bonded alumina silicon carbide idastics and ram mixes. 

Ohji, T., A. Nakahira, T. Hirano, and K. Niihara. 1995. Tensile creep behavior of alumina/silicon carbide nanocomposite. Journal of the American Ceramic Society 77(12) 3259-3262. ... 

Nylon, polyester (unsaturated) and, currently, aromatic Nylons (aramides) like Kevlar. High-performance (and expensive) reinforcing fillers include carbon (mainly graphite) fibers, alumina, silicon, carbide, nitrite, boron, beryllium and other metals. Producing extremely high strength and stiffness, these specific fibers have been developed for space, aviation and military use. 

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