Solid-State Sintered Alumina

Zuo, R. and Rddel, J. (2004) Temperature dependence of constitutive behavior for solid-state sintering of alumina, Acta Mater. 52, 3059. Includes a discussion of hot-forging of alumina. 

Figure 1. Relicts of hard powder granules (from spray drying) in pressureless sintered alumina ceramics (solid state sintering).

Krell A, Klimke J (2006) Effects of the homogeneity of particle coordination on solid-state sintering of transparent alumina. J Am Ceram Soc 89 1985-1992... 

The phase composition and texture of high-alumina cement produced by solid-state sintering will also be affected by the production process used, but to a lesser extent. 

The measures of solid state reactivity to be described include experiments on solid-gas, solid-liquid, and solid-solid chemical reaction, solid-solid structural transitions, and hot pressing-sintering in the solid state. These conditions are achieved in catalytic activity measurements of rutile and zinc oxide, in studies of the dissolution of silicon nitride and rutile, the reaction of lead oxide and zirconia to form lead zirconate, the monoclinic to tetragonal transformation in zirconia, the theta-to-alpha transformation in alumina, and the hot pressing of aluminum nitride and aluminum oxide. 

Thermal deactivation involves processes such as diffusion and solid-state reaction. In early three-way catalysts where both the active metal and ceria were dispersed onto high-surface-area Y-A1203, loss of contact between them, due to sintering of either one or both, could effectively eliminate oxygen storage. The temperature required for ceria to sinter, somewhat above 800°C, was typically not attained under normal operating conditions, although relatively harsh conditions, with temperatures well in excess of 800°C under rich exhaust gas, did exist in heavy-duty truck operation, and in this case, reaction between ceria and alumina at times produced stable, inert cerium aluminate. 

Preparation of Solid State Electrolytes 17.3.7.1. -Alumina Ceramic Electrolytes 17.3.7.1.3. Sintering (Densification) and Annealing. 

Various solid state reactions are involved in the process. In addition to those governing sintering, catalyst-support interactions may alter the nature and catalytic activity of the solid and may stabilise or destabilise the solid towards sintering. Thus, for example, the formation of nickel aluminate, NiAlgO, is well established in steam reforming catalysts [21,22], and this compound is catalytically inactive. However, its presence may affect the thermal stability of the solid [23], as is the case in cobalt-molybdenum and nickel-molybdenum based catalysts supported on alumina and used for hydro-treating [24]. 

For high purity calcium aluminate compositions, solid-state synthesis is still the norm [33, 34], Most CAC compounds are made by solid-state reactions between ground powders of calcium carbonate and purified alumina. The sintering temperatures depend on alumina content. More recently attempts have been made to synthesize CA compounds using processes with temperatures less than 900°C. These latter methods include sol-gel synthesis and precipitation and are important for production of high-purity homogenous powders with small grain size. 

The single-phase AlON powder used in this experiment was obtained at relatively low temperature by the solid-state reaction method with nanosized AIN powder and nanosized alumina powder [292]. The obtained powder was ground by ball milling and doped with Y2O3. Then, it was shaped into pellets. Transparent ceramics sintering was carried out at 2153 K (1880 °C) for 5, 10, and 20 h. Obtained... 

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