Abstract: The present invention relates to: a novel process for the preparation of mesophasic polyborazylene. Said process is of particular value in that it affords a quality product from an appropriate polyborazylene, rapidly (virtually instantaneously), reproducibly and with a good yield. Furthermore, said process is easy to carry out. Said process comprises the preparation of polyborazylene by the polycondensation of borazine in a closed reactor and the addition, to said polyborazylene obtained by polycondensation, of a solvent selected from aromatic solvents, borazine solvents and mixtures thereof, mesophasic polyborazylene which is novel in that it is in the presence of a particular solvent and/or by virtue of its quality, the use of said polyborazylene of the invention, and/or prepared according to the invention, as a boron nitride precursor.

Abstract: A boron and silicon oxynitride obtained by preparing a polyborosiloxane precursor, conducting nitriding pyrolysis of the precursor to obtain an amorphous boron and silicon oxynitride, and optionally conducting additional pyrolysis to obtain a crystallized boron and silicon oxynitride. The polyborosiloxane precursor is prepared by condensation, in the presence of a catalyst, of (2) a polychlorosilane represented by the formula R3R4SiCl2 in which the substituents R3 and R4 are identical or different and each represents a hydrogen atom, a chlorine atom, a linear or branched alkyl or alkenyl or alkynyl radical having 5 or less carbon atoms, or an aryl or aralkyl radical having 6 to 18 carbon atoms, with (2) an alkyl borate represented by the formula (R5O)3B in which R5 represents a linear or branched alkyl radical having 1 to 5 carbon atoms.

Abstract: Infusible and insoluble polycarbosilanes, readily pyrolyzed into silicon carbide ceramic materials, e.g., SiC fibers, are produced by hardening a fusible polycarbosilane containing at least two .tbd.SiH groups per molecule via intimately contacting such fusible polycarbosilane with an effective hardening amount of the vapors of sulfur.

Abstract: Silicon carbonitride ceramic materials are produced by (a) hardening a fusible polycarbosilane containing at least two .tbd.SiH groups per molecule by intimately contacting such fusible polycarbosilane with an effective hardening amount of the vapors of sulfur, next (b) heat treating the infusible polycarbosilane which results under an ammonia atmosphere to such extent as to introduce nitrogen into the infusible polycarbosilane without completely removing the carbon therefrom, and then (c) heat treating the nitrogenated polycarbosilane in a vacuum or in an inert atmosphere to such extent as to essentially completely convert it into a ceramic silicon carbonitride.

Abstract: Extrudable pre-ceramic polycarbosilanes are prepared by intimately contacting a crude polycarbosilane containing a fraction of high molecular weight polymers (e.g., molecular weights greater than about 25,000) with ethyl acetate, whereby selectively dissolving desired extrudable polycarbosilane essentially devoid of such fraction of high molecular weight polymers in the ethyl acetate, and then recovering such dissolved polycarbosilane from the ethyl acetate solvent.

Abstract: Silicon nitride ceramic materials are produced by (a) hardening a fusible polycarbosilane containing at least two .dbd.SiH groups per molecule by intimately contacting such fusible polycarbosilane with an effective hardening amount of the vapors of sulfur, and then (b) pyrolyzing the infusible polycarbosilane which results under an ammonia atmosphere.

Abstract: The present invention relates to copolymers containing --Si--N-- and --Si--Si-- bonds, which are obtained by the polycondensation ofat least one silane of the formula RR.sub.1 SiCl.sub.2and at least one disilazane of the formula ##STR1## in which formulae: R.sub.2 is a halogen atom, preferably Br and Cl, andR, R.sub.1 and R.sub.3, which are identical or different, represent a hydrogen atom or an alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, aryl, alkylaryl or alkenylaryl hydrocarbon radical which may be functional,to a process for the preparation of the said copolymers,to the polycarbosilazanes obtained by thermolysis of the said copolymers and to the silicon carbonitrides obtained by heating the said polycarbosilazanes.

Abstract: The present invention relates to functional 1,3-dihydrogeno disilazanes of formula: ##STR1## in which: R and R.sub.1, identical or different, represent an atom of hydrogen or a hydrocarbon such as an alkyl, alkenyl or alkynyl, cycloalkyl or cycloalkenyl, aryl, alkylaryl, alkenylaryl, alkynylaryl, arylalkyl, arylalkenyl or arylalkynyl radical, possibly functional, R also being able to represent a radical ##STR2## and R.sub.2 represents an atom of halogen, an OR group or an --NRR.sub.1 group, when R and R.sub.1 are both hydrocarbon radicals.

Abstract: The present invention relates to a process for preparing disilylmethanes, wherein the magnesian reaction is carried out between methylene chloride and at least one chlorosilane in a donor solvent.

Abstract: A process for preparing hydrogenosilanes by hydrogenating disilanes, especially halogenated disilanes, under relatively mild reaction conditions is disclosed. The hydrogenation is effected in the presence of a catalytic system containing an aprotic compound and a nickel catalyst which consists essentially of finely divided nickel and is obtained by preliminary or in situ reduction of a nickel compound.