Reaction sintering zircon

Khor K A, Yu L G, Li Y. Spark plasma reaction sintering of Zr02 mullite composites from plasma sphe-roidized zircon/ alumina powers. Mater Sci Eng A, 2003, 339 (12) 286-296,... 

Garrido L B, Aglietti E F. Reaction-sintered mullite-zirconia composites by colloidal processing of alumina-zircon-Ce02 mixtures. Mater Sci Eng A, 2004, 369 (12) 250-257. 

Figure 11.57 Sintering and reaction schedule for reaction sintering of zircon-AI2O3 powder mixtures. At A, only zircon and AI2O3 are detected by x-ray analysis at B, the reaction to produce mulUte and ZrC>2 is completed. (From Ref. 94.)...

Figure 11.58 Bright field transmission electron micrograph of a Zr02-muUite material produced by reaction sintering of zircon-Al203 powder mixtures. The material was annealed for 1 h. Larger twinned particles are monoclinic Z1O2 and the smaller particles (T) are tetragonal Zr02. Note the considerable stress contours in the mulUte matrix. (From Ref. 94.).

Reaction-sintering, sintering (q.v.) of a two-component powder, in which a chemical reaction also takes place to produce a dense single phase or a multiphase material. Ceramic-ceramic composites may be thus produced - e.g. dense mullite zirconia composites from zircon and alumina. See also reactive HOT-PRESSING. 

P. Pena, J.S. Moya, S. Aza, E. Cardinal, F. Cambier, C. Leblud, and M.R. Anseau, Effect of Magnesia Additions on the Reaction Sintering of Zircon/Alumina Mixtures to Produce Zirconia... 

Anseau, M.R., Leblud, C. and Cambier, F., Reaction Sintering [RS] of Mixed Zircon-Based Powders as a Route for Producing Ceramics Containing Zirconia with Enhanced Mechanical Properties. J. Mat. Sci. Lett 2, %6-370 (1983). 

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. 

Fhiosilicate fusion has been used in the Soviet Union [SI] to produce feed for separation of hafnium from zirconium by fractional crystallization of KjMF . Zircon is ground to pass 200 medi and mixed with potassium fluosilicate and potassium chloride (to act as promoter). The mixture is sintered in a rotary furnace at 650 to 700°C. The following reaction takes place ... 

A properly chosen support may stabilize a catalyst against sintering. In the case of NijS2 catalysts such supports are commonly used. Supports of this type include refractory oxides which do not react appreciably with hydrogen sulfide, for example alumina, silica, thoria, zirconia, and titania, as well as certain silicates, aluminates, thorates, zirconates, and titanates. Active carbon can be used as a support for NiS or NiaS2 catalysts for reactions which do not involve oxygen. 

Claussen and Jahn ° were the Erst researchers to show that the mechanical properties of mullite could be improved by the dispersion of zirconia particles. Fracture toughness improved from 2.0 to 4.5 MPa-ml4 and the strength doubled to 400 MPa. They were able to fabricate the dense (>98% theoretical density (T.D.)) mullite-zirconia composite at relatively low sintering temperatures of 1575-1600 °C by the in-silu reaction of alumina and zircon to form mullite with approximately 25 vol% zirconia ... 

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