| 摘要 |
The invention relates to a novel sinterable ceramic powder, to its preparation and to its further processing to give a silicon nitride ceramic, and to this material itself and its use. The sinterable ceramic powder is produced by melting a polysilazane or dissolving it in an organic solvent, suspending a powdered sinter aid in this melt or solution, then pyrolyzing the melt, or the residue obtained after evaporation of the solvent, at 500 DEG to 1600 DEG C. in a protective gas atmosphere, the polysilazane either A) being obtainable by reacting at least one of the oligosilazanes of the formula (I) <IMAGE> +TR <IMAGE> in which a, b, c and d are the mole fractions of the respective structural units and where 0</=a</=1, 0</=b</=1, 0</=c</=0.7, 0</=d</=0.7, 0.3</=a+b, c+d</=0.7 and n is approximately 2 to approximately 12, with at least one of the chlorosilanes R6R7SiCl2, R8SiCl3, Cl2R9Si-CH2CH2-SiR9Cl2 and Cl3Si-CH2CH2SiR10Cl2 at 30 DEG to 300 DEG C., where, independently of one another, R1, R2, R4, R6, R7 and R8 are H, C1-C6-alkyl or C2-C6-alkenyl and R3, R5, R9 and R10 are C1-C6-alkyl or C2-C6-alkenyl, or B) having the following formula <IMAGE> in which R and R* can be identical or different and R and R* are C1-C4-alkyl, vinyl or phenyl and R' is C1-C4-alkyl and x and y are the mole fractions of the two structural units, where x+y=1 and x=0.7-0.95. A molded article can be formed from the ceramic powder thus obtained and a silicon nitride ceramic then produced by sintering. However, a molded article can also be formed from the solidified melt or the still unpyrolyzed residue obtained after evaporating the solvent and this article can then by pyrolyzed and sintered. Components subject to severe mechanical, thermal and corrosive stress can be produced from the ceramic obtained. |
