Ceramic Oxide Powders and the Formation Thereof
The invention is concerned with ceramic oxide powders, formed from one or more ceramic oxide precursors, which have utility as ceramic oxides of high strength and low thermal expansion coefficient. The ceramic oxide powders are formed in a counterflow diffusion flame burner using a fuel stream comprising a gaseous fuel and an inert gas diluent, and an oxidizing gas stream comprising oxygen and an inert gas diluent. The gaseous fuel may be, for example, hydrogen, methane, ethane, ethylene, acetylene, or mixtures thereof. The preferred fuel is hydrogen. The inert gas in both the fuel stream and the oxidizing gas stream may be, for example, nitrogen, one of the rare gases such as helium, neon, argon, krypton, xenon, or mixtures thereof. A convenient oxidizing gas stream is air which essentially comprises oxygen and nitrogen. Description (Set) Proposed Use (Set) This invention is characterized by ceramic oxide powders having unique properties and a method for their preparation. More particularly, the invention is concerned with ceramic oxide powders formed by a flame process in a counterflow diffusion flame burner from at least one ceramic oxide precursor. By varying reaction conditions, it is possible to control particle size, morphology, and crystalline form of the ceramic oxide powders. The flame conditions, e.g., temperature and gas flow rate, and precursor concentration ratios are parameters which determine the ceramic oxide particle growth processes. A strong temperature dependence is apparent. Patent (Set) 5,268,337; 5,650,130
Katz, Joseph L.
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