Preparation of Si/C/Al/N ceramics by pyrolysis of polyaluminasilazanes

Polyaluminasilazanes were prepared quantitatively by reaction of oligosilaz anes (RSi(H)NH)(n) (R = Me, Et) with various amounts of either trimethylalu minum, (CH3)(3)Al, or dimethylaluminum amide, (CH3)(2)AlNH2, The products w ere characterized by IH,Si-29 and Al-27 NMR and IR spectroscopy. Alkylation of the Si-H groups was observed when trimethylaluminum was used. Their pyr olysis was carried out under argon or ammonia. Ceramic residues were obtain ed in high yield and were characterized by elemental analysis and X-ray pow der diffraction, Formation of mixed ceramics containing silicon nitride, si licon carbide and/or aluminum nitride was observed depending on the precurs or and the experimental procedure that was used, The thermal decomposition of the polyaluminasilazane between 50 and 700 degrees C was investigated by IR analysis of the gas evolved during the pyrolysis, Molecular aluminasila zanes were studied as model compounds. Copyright (C) 1999 John Wiley & Sons , Ltd.