15  4,675,424  16  37. The silicon nitride-containing ceramics prepared  from the silazane polymers of claim  31.  * * * * *  24.  The method of claim  aminosilane  reactants  are  23  wherein the starting  mixtures  of tris(dime- 23.  The method of claim  1  wherein the starting  aminosilane reactant comprises a mixture of polymers as  defmed by the aminosilane general formula tran› saminated with amine.  36.  The silicon nitride-containing ceramics prepared  from the silazane polymers of claim  30.  35.  The silicon nitride-containing ceramics prepared  from the silazane polymers of claim  29.  34.  The silicone nitride-containing ceramics prepared  from the silazane polymers of claim  28.  33.  The silicon nitride-containing ceramics prepared  from the silazane polymers of claim  27.  32. The silicon nitride-containing ceramics prepared  from the silazane polymers of claim  26.  31.  The silazane polymers produced by the method of  claim  1  wherein the starting aminosilane reactants are  mixtures of tris-(dimethylamino)silane and vinyl-tris(› dimethylamino)silane transaminated with CH3NH2.  30.  The silazane polymers produced by the method of  claim  1  wherein the starting aminosilane reactants are  mixtures of tris(dimethylamino)silane and vinyl-tri(- dimethylamino)silane transaminated with NH3.  22.  The method of claim  19  wherein the solvent is  toluene or xylene.  21.  The method of claim  19  wherein the solvent is 25  selected from the group consisting of alkanes and alkyl› ated benzenes having 6-10 carbon atoms wherein the  reaction products are soluble.  20.  The method of claim  19  wherein said solvent is  selected from the group consisting of alkanes and alkyl› ated benzenes having 6-20 carbon atoms wherein the  reaction products are insoluble.  19.  The method of claim  1  wherein the transaminat› ing reaction is run in a solvent which is largely unreac› tive under the reaction conditions.  29.  The silazane polymers produced by the method of  claim  1  wherein the starting reactant comprises a mix- ture of polymers as defined by the aminosilane general  formula transaminated with amine.  28.  The silazane polymers produced by the method of  claim  14.  27.  The silazane polymers produced by the method of  claim  1  wherein c= 1 or 2.  18.  The method of claim  17  wherein the mildly acidic  catalyst is para-toluene sulfonic acid.  17.  The method of claim  14  wherein, in the produc› tion of silazane polymers to be used as impregnants in  porous preformed ceramic parts, the transaminating  reaction is run at a temperature of 20’ -80’ C. in the  presence of a mildly acidic catalyst.  16.  The method of claim  15  wherein the strongly  acidic catalyst is H2S04.  26.  The silazane polymers produced by the method of  claim  1.  25.  The method of claim  23  wherein the starting  aminosilane  reactants  are  mixtures  of tris(dime- thylamino)silane and  vinyl-tris(dimethylamino)silane  transmitted with CH3 NH2  thylamino)silane and vinyltris(dimethyamino) silane  transaminated with NH3  15.  The method of claim  14  wherein, in the produc› tion of high purity silicone nitride, the transaminating  reaction is run at a temperature of 100’ -200" C. in the  presence of a strongly acid catalyst.  morphology desired on the final silicone nitride prod› uct. 