GB742469A - Improvements relating to ceramic pipes and tubes, and other hollow ceramic articles - Google Patents

Abstract

A slurry for moulding thin-walled ceramic tubes and pipes and other hollow articles comprises a finely divided ceramic raw material and a hydrolysable organic silicate in an aqueous medium. In an example 500 cc. of an ethyl silicate containing the equivalent of 40 to 42 per cent by weight of silica, and prepared by the reaction of silicon tetrachloride with ethyl alcohol containing 5 per cent water, was shaken with 100 cc. of 1 per cent aqueous HCl until the temperature of the mixture ceased to rise. 1400 cc. of distilled water was then added and the soda cooled to room temperature. Fused alumina (100 g.) of fineness passing a 200-mesh B.S. sieve and light magnesia powder of fineness passing a 300-mesh B.S. sieve were mixed together and the ethyl silicate medium (22 cc.) stirred in to form the final mixture. In another example, zircon sand was used in place of alumina. Specifications 674,137, [Group IV (b)], and 722,425 are referred to.ALSO:In a process for the production of thin-walled ceramic pipes, tubes, and other hollow articles, a slurry of a finely divided ceramic raw material (e.g. alumina, sillimanite, zircon) and a hydrolyzable organic silicate in aqueous medium is shaped in a cored mould; the shaped product is withdrawn from the mould when it has formed an elastic gel, but before it has set rigid, and is then dried and fired. In an example, an ethyl silicate treated with hydrochloric acid and diluted with distilled water, was stirred into a fine mixture comprising fused alumina and light magnesia powder and the slurry obtained was poured into a greased mould consisting of an inner core of plaster of paris and an outer glass tube, the cavity having an outer diameter of 2 inches, length 10 inches and thickness 1/8 inch. After gelation, the core was withdrawn and the jelly casting pushed or pressed from the outer mould wall. The tube obtained was hardened at room temperature for 12 hours, dried in an oven at 80 DEG C. for 4 hours, heated 1 hour to 1500 DEG C. and held at this temperature for 1 hour before being allowed to cool for 18 hours. Specifications 674,137 and 722,425, [Group IV(a)], are referred to.