Abstract: The ceramic composites consisting of sintered alumina comprising a polycrystalline alumina matrix having a grain size of from 0.5 to 10 .mu.m, and fine particles of TiB.sub.2 2 .mu.m or less in diameter being dispersed in the alumina grains, the composite alumina ceramic containing from 15 to 40% by volume of TiB.sub.2 ; or a ceramic composites comprising a polycrystalline alumina matrix as above, fine particles of TiB.sub.2, and fine particles of SiC, the fine particles of TiB.sub.2 and SiC being each 2 .mu.m or less in diameter and being dispersed in the alumina grains, the ceramic composites containing from 5 to 30% by volume of TiB.sub.2 and from 5 to 30% by volume of SiC.

Abstract: A ceramics composites prepared by dispersing any one of the following materials (i) to (viii) in Al.sub.2 O.sub.3 which as a matrix-containing crystalline grains having a grain size of 0.5 to 100 .mu.m. (i) 3 to 40% by volume of fine TiN particles having a particle size of not more than 2 .mu.m and 3 to 40% by volume of fine SiC particles having a particle size of not more than 2 .mu.m. (ii) 3 to 40% by volume of fine TiN particles having a particle size of not more than 2 .mu.m and 3 to 40% by volume of fine Si.sub.3 N.sub.4 particles having a particle size of not more than 2 .mu.m. (iii) 2 to 35% by volume of fine TiC particles having a particle size of not more than 2 .mu.m and 5 to 40% by volume of SiC whiskers having a diameter of 0.05 to 2 .mu.m. (iv) 2 to 35% by volume of fine TiC particles having a particle size of not more than 2 .mu.m and 5 to 40% by volume of Si.sub.3 N.sub.4 whiskers having a diameter of 0.1 to 2 .mu.m.

Abstract: There is provided a method of monitoring a firing condition in a cement kiln, by measuring an intensity of spectrum of a radiation which radiation is emitted from a clinker being fired in a cement kiln, and processing the intensity of the spectrum to produce a parameter for monitoring the condition in the kiln, by correcting the intensity profile of the spectrum by interpolating a profile (range) which is deformed by the absorption with alkali atom(s) in an atmosphere of the kiln. Further, the absorption intensity of the spectrum at a sodium absorption wavelength and potassium absorption wavelength should be continuously measured and corrected by interpolating so as to produce a parameter for monitoring.