Method of producing a composite material having a high SiO2 content, composite material obtained according to the method, and permanent mold made thereof

摘要

Known is a method of producing a composite material having an SiO2-containing matrix in which quartz glass grains are embedded, wherein a suspension is prepared from a particle mixture of finely divided SiO2 powder having at least two different particle fractions and of the quartz glass grains, a green compact is formed therefrom and said compact is sintered. To permit an inexpensive production of a composite material having a high resistance to temperature changes together with a high density, it is suggested according to the invention that the matrix should have an SiO2 content of at least 99% by wt. and should be formed from at least a first (33) and a second (35) particle fraction, each of the particle fractions being present as granules of nanoscale, amorphous, synthetically produced SiO2 primary particles (2) having a mean primary particle size of less than 100 nm. The composite material produced according to the method is characterized by an SiO2-containing matrix which has an SiO2 content of at least 99% by wt. It is particularly suited for applications where temperature strength, density and high purity are of importance, e.g. as a starting material for producing a permanent mold for melting solar silicon.