Abstract A process for preparing ceramic materials with reduced carbon levels is described. The process involves treating a silicon-containing preceramic polymer with ammonia at a temperature of 550-800°C. for a time sufficient to reduce the carbon content prior to pyrolysis at 900-1500°C. Another process also involves the pyrolysis of a silicon-containing preceramic polymer in an ammonia atmosphere. The carbon level of ceramic materials produced by this invention can be controlled to a given, desired level by varying the process conditions. Suitable silicon-containing preceramic polymers include polycarbosilanes, polysilazanes, polysilanes, organosilsesquioxane-containing sol-gels, and organopolysiloxanes which are capable of being converted to ceramic materials when fired to elevated temperatures. Ceramic fibers can be prepared by the processes disclosed which contain less than 0.25 weight percent carbon.
A process for preparing a ceramic material with reduced carbon level comprising: (A) heating a silicon-containing preceramic polymer at a temperature of about 550-800°C. in an ammonia-containing atmosphere for a time sufficient to reduce the carbon level of the silicon-containing preceramic polymer wherein said ammonia-containing atmosphere contains 0-99 volume percent inert atmosphere and 1-100 volume percent ammonia, and, then, (B) heating the material formed in step (A) to a temperature of 900-1500°C. in an inert atmosphere, vacuum, or in the presence of ammonia gas until a ceramic material with reduced carbon level is obtained.
Claim 2
Dependent Claim
94 words
A process for preparing a ceramic material with reduced carbon level comprising: (A) heating a silicon-containing preceramic polymer at a temperature of about 550-800°C. in an ammonia-containing atmosphere for a time sufficient to reduce the carbon level of the silicon-containing preceramic polymer wherein said ammonia-containing atmosphere contains 0-99 volume percent inert atmosphere and 1-100 volume percent ammonia, and, then, (B) heating the material formed in step (A) to a temperature of 900-1500°C. in an inert atmosphere, vacuum, or in the presence of ammonia gas until a ceramic material with reduced carbon level is obtained.
Claim 3
Dependent Claim
22 words
A process as defined in claim 1, wherein said ammonia-containing atmosphere contains 0-78 volume percent inert gas and 22-100 volume percent ammonia.
Claim 4
Dependent Claim
15 words
A process as defined in claim 1, wherein said silicon-containing preceramic polymer is a polycarbosilane.
Claim 5
Dependent Claim
15 words
A process as defined in claim 2, wherein said silicon-containing preceramic polymer is a polycarbosilane.