Pyrogenic oxides and process for the preparation thereof

Pyrogene Oxide mit einer BET-Oberfläche zwischen 30 und 150 m /g weisen in einer wäßrigen Suspension eine Viskosität von weniger als 2500 mPas auf. Sie werden hergestellt, indem man bei der Hochtemperaturflammenhydrolyse das Wasserstoffverhältnis gamma und das Sauerstoffverhältnis lambda unter eins einstellt. Die pyrogenen Oxide werden bei der CMP-Anwendung in der Elektronikindustrie eingesetzt. A process for pyrogenic oxide production by high temperature flame hydrolysis employs a central tube raw material gas mixture which has a hydrogen ratio ( gamma ) of less than 1 (preferably 0.7-0.9) and an oxygen ratio ( lambda ) of optionally less than 1 (preferably 0.7-0.9), where gamma is the ratio of supplied hydrogen (including hydrogen from the raw materials) to the stoichiometrically required hydrogen and lambda is the ratio of supplied oxygen to the stoichiometrically required oxygen. Also claimed are: (i) a pyrogenic metal or metalloid oxide (preferably silicon dioxide) produced under the above conditions; (ii) a pyrogenic silicon dioxide produced by the above process and having a BET surface of 30-150 m /g and, when in the form of a 19% aqueous suspension, a viscosity of less than 2500 (preferably less than 1000) mPa.secs.; and (iii) a pyrogenic silicon dioxide produced by the above process and having a BET surface of 30-150 m /g and a fractal BET dimension of less than 2.605 (as determined by N2 adsorption in the pressure range p/p0 = 0.5 to 0.8, according to the fractal BET theory for multilayer adsorption by the method of Pfeifer, Obert and Cole, Proc. R. Soc. London, A 423, 169 (1989)).