Atochem

Elf Atochem S.a.

Max-planck-institut Fur Metallforschung

Christian Colombier

Jean-Pierre Cuer

Jean-Pierre Disson

Gilbert Fantozzi

Richard J Brook

Gerd Passing

Ralf Riedel

Maurice Gonon

Metal and/or metalloid nitride and/or carbide powders, e.g., amorphous or crystalline spherical particulates having a mean diameter greater than 0.2 .mu.m 90% of which being less than 0.4 .mu.m in size, well suited for the production of ceramic shaped articles exhibiting good thermomechanical properties and useful, for example, in the automotive and aeronautic fields, are prepared by flash pyrolyzing coarse drops of a precursor compound convertible into such nitride and/or carbide, at an elevated temperature and for such period of time as to convert the precursor compound into said amorphous or crystalline powder.

Metal/metalloid nitride/carbide ceramic powders prepared by flash

Crack-free, dense and either amorphous or crystalline, nonoxide monolithic ceramic shaped articles are produced at relatively low temperatures, by shaping a powder (P) of an infusible, organometallic ceramic precursor polymer (Pi) into a green body having a relative density of at least 65%, and thence pyrolyzing such shaped green body.

Production of nonoxide monolithic ceramic shaped articles

Novel high viscosity polyhydrosilazanes containing recurring structural units of the formula: ##STR1## are prepared by reacting a halosilane with ammonia and/or an amine, and then reacting the ammonolysate thus produced with a hydrazine compound.

Hydrazino/polyhydrosilazanes

Polysilazane-based ceramic precursor compositions, well adapted for high yield pyrolytic conversion into ceramic shaped articles, include a polysilazane component derived from ammonia and a polysilazane component derived from a hydrazine.

Polysilazane ceramic precursors and ceramic shaped articles produced by

A process for the preparation of novel polysiloxazane compositions which comprises reacting at least one halosilane having the formula (R.sub.1).sub.a (R.sub.2).sub.b Si(Y).sub.4-(a+b) with at least one hydrazine having the formula NHR.sub.3 -NHR.sub.4 and water, wherein R.sub.1 and R.sub.2 are a hydrogen atom or a methyl, ethyl, vinyl or phenyl radical; R.sub.3 and R.sub.4 are hydrogen atoms, Y is a halogen atom and (a+b) is an integer between 0 and 3 and preferably 2. Polysiloxazane polymer compositions formed with polysiloxazanes prepared by the process described above comprise units of formula: ##STR1## combined with units of formula: ##STR2## and, if desired, units of formula: ##STR3## and, if desired, with units of formula: ##STR4## wherein radicals R.sub.1, R.sub.2, R.sub.3 and R.sub.4, which may be identical or different, may denote a hydrogen atom, a saturated or unsaturated aliphatic hydrocarbon radical or a mono- or polycyclic aryl, alkylaryl or arylalkyl radical, and wherein these radicals have a total molecular mass greater than 350.

Growing community of inventors

Lyons, France

Christian Colombier