Silicon nitride-containing material with self-glazing surface and process for its production

DETAILED DESCRIPTION The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows: 1.
A process for the production of a silicon nitride-containing material with a gas-tight surface and improved oxidation resistance which comprises admixing 3-25 percent by weight based on the weight of the resulting admixture of at least one powdered ceramic, silicate-containing additive having a particle size of less than 20 m.
mu.
and the silicon raw material, subjecting the admixture to standard nitriding condition and subjecting the nitrided admixture to a heat treatment between 1,000.
degree.
C and 1,500.
degree.
C in an oxygen-containing atmosphere, wherein said admixture is heated to said temperature at a rate exceeding 100.
degree.
C per minute, nitride-containing material.
2.
Process for the production of a silicon nitride-containing material according to claim 1, characterized in that the heat treatment is effected in air.
3.
Process for the production of a silicon nitride-containing material according to claim 1, characterized in that the additive is magnesium aluminum silicate in an amount of 10-15 weight percent.
4.
Process for the production of a silicon nitride-containing material according to claim 1, characterized in that lithium aluminum silicate is an amount of 5-10 weight percent.
5.
A silicon nitride-containing body having a gas tight surface and improved resistance to oxidation produced by the process of claim 1.




Description:
BACKGROUND OF THE INVENTION Gas-tight and oxidation resistant silicon nitride materials are often required in machines and in plants in recuperators, pipe lines, tanks, etc.
, wherein there are high application temperatures.
There is interest in improving the oxidation resistance of silicon nitride materials used where gas tightness is absolutely necessary, for example, in combustion chambers, turbine blades and distributors.
Processes are known for producing gas-tight silicon nitride and for reducing its porosity