Keramiske kuler og fremgangsmaate til deres fremstilling

摘要

Ceramic spheroids having: A. a core made by firing raw materials comprising about: 50-99.8 parts by weight mineral particulates; 0.1 to 50 parts by weight silicon carbide; and 0.1 to 15 parts by weight binder (e.g. bentonite); and B. an outer shell comprising Al2O3 or MgO. More alumina or magnesium oxide is contained in the outer shell than in the core. The core of the ceramic spheroid has closed cell microporosity. The inventive spheroids are characterized by a density less than 2.2 g/cc and can be readily made to have a density less than 1 g/cc. These ceramic spheroids combine high strength (due to the tough outer shell) with low density (due to the closed cell microporosity) and have applications (among others) as buoyant water filtration media and low density fillers.