Massachusetts Institute of Technology

Other

The Dow Chemical Company

Akzo Nobel N.v.

Dietmar Seyferth

Yuan-Fu Yu

Timothy Grant Wood

Pawel Czubarow

Ralf Wyrwa

Gary H Wiseman

Tom S Targos

Joanne M Schwark

Henry J Tracy

Andrzej M Piotrowski

Jere D Fellmann

Philip E Garrou

Uli W Franz

Toshiya Sugimoto

William S Rees, Jr

David P Workman

Dennis F Taylor

Christine A Sobon

Christian C Prud'Homme

Sigurd Becke

Jutta Borm

Howard P Withers, Jr

Herbert Plenio

Gudrun E Koppetsch

Jennifer L Robison

Nathan Bryson

Group 4 metal-containing organosilicon dendrimers are described. Also described are methods for synthesizing the dendrimers. The dendrimers can be useful in several applications including as olefin polymerization and copolymerization catalysts and as silane polymerization catalysts.

Olefin polymerization with group 4 metal-containing organosilicon dendrimers

A process is provided that involves reductive coupling of polysilane precursors to form polysilane in the presence of ultrasonification. The resulting precursors, upon pyrolysis, lead to improved SiC ceramic product. Ultrasonification can be used to produce oligosilanes from precursors thereof, or polysilanes from monomers, dimers, trimers, or oligomers. Precursors can include Si:C in a ratio of about 1:1, and the invention allows formation of SiC having a Si:C ratio of about 1:1.

Sonichemical synthesis of silicon carbide precursors and methods for

Group 4 metal-containing organosilicon dendrimers and method for

Bromomagnesium tetrakis(fluorophenyl) borate reactible intermediates can be formed by reacting at least four equivalents of fluorophenyl magnesium bromide with every one equivalent of boron trifluoride in ether solvent using a sufficient amount of heat to drive the reaction to completion. This type of reactible intermediate can then be reacted with a salt containing a suitable cation, such as ammonium, trityl or onium, preferably substituted with phenyl or alkyl, such as lower alkyl, to form the desired combination of weakly coordinating boron anion and activating cation.

Process for forming a bromomagnesium tetrakis (fluorophenyl) borate

The invention provides a method for in-situ powder metallurgy processing of a functionally gradient material (FGM) which uses a preceramic polymer binder system with the metal and/or ceramic powders used to produce the intermediate layers of the composite. The invention also provides a method for controlling shrinkage of the functionally gradient material during processing while still preserving the desired density of the intermediate layers by controlling the preceramic polymer binder content within the functionally gradient material.

Method for preparation of a functionally gradient material

Ceramic compositions can be formed by the pyrolysis of a particulate metal, which forms a component of the ceramic, and another metal, which forms another component of the ceramic.

Ceramic synthesis by pyrolysis of metal-containing polymer and metal

A method of forming modified preceramic polymers comprising mixing organopolysilanes having a plurality of Si--H functional groups with an effective amount of a metallocene compound, and allowing the mixture to undergo a dehydrogenative reaction is disclosed. Pyrolysis of the modified polymer provides in high yields ceramic residues that approach stoichiometric SiC in composition. Preferably the organopolysilane starting material contains a plurality of tertiary Si--H bonds and has the general formula of [(RSiH).sub.x (RSi).sub.y ].sub.n where the sum of the coefficients x and y equal 1, n is an integer greater than 1, R is a lower alkyl group having from 1 to about 8 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 8 carbon atoms, a cycloalkyl group having from 3 to about 10 carbon atoms, substituted or unsubstituted aryl group having from 6 to about 10 carbon atoms. More preferably R is a lower alkyl group having from 1 to about 8 carbon atoms, and still more preferably R is methyl so that the molar ratio of carbon to silicon of the polymer is about 1. The organopolysilanes can be prepared from silyl halides by alkali metal condensation reactions.

Preparation of silicon carbide ceramics from the modification of an Si-H

Preceramic polymers are prepared by mixing an organosilicon oligomer or polymer containing a multiplicity of Si--H and/or Si--N functional groups with a borane in an organic solvent for a sufficient time for the reactants to react, wherein the molar ratio of the organosilicon polymer repeat unit to borane is 15 or less.

Preceramic organosilicon-boron polymers

Organosilicon-metal polymers are prepared by mixing an organosilicon polymer containing a multiplicity of Si-H and/or Si-Si functional groups with a sufficient quantity of a metal carbonyl for the metal carbonyl to be incorporated into the organosilicon polymer. These polymers can be used to prepare ceramics.

Preceramic organosilicon-metal carbonyl polymers

New soluble preceramic polymers formed by reacting B.sub.10 H.sub.14-n R.sub.n, (where R is a lower alkyl group having from 1 to about 8 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 8 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 8 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and n is a number from zero to about six) with a diamine in an organic solvent are disclosed. Preferably the diamine has the formula

Lewis base adducts of decaborane for forming new preceramic polymers,

A method of forming preceramic polymers using a organopolysilane of the formula [(RSiH).sub.x (RSi).sub.y ].sub.n, where R is a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbons atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group and n is an integer greater than 1, and reacting it with alkali metal amides or silylamides in catalytic quantities is disclosed. Preferably, the alkali metal amide is a polymeric alkali metal silylamide of the formula [(R.sup.1 SiHNH).sub.a (R.sup.1 SiN).sub.b (R.sup.1 SiHNM).sub.c ].sub.m where a+b+c=I; R.sup.1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted alkenyl group having from 2 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group or a di(lower)alkylamino group; M is an alkali metal or one-half equivalent of an alkaline earth metal; and n and m are integers greater than I. Novel preceramic polymers formed by this method are also disclosed.

Method for forming new preceramic polymers for SiC and Si.sub.3 N4/SiC

A method of protecting carbon/carbon composites against oxidation at high temperatures is disclosed. This comprises coating the composite with a hybrid metal alkoxide/organosilicon polymer. The hybrid polymer is prepared by a method comprising mixing an organosilicon polymer having a plurality of Si-H functional groups with a sufficient quantity to undergo a hydrosilylation reaction of a metal alkenoxide, wherein the metal alkenoxide comprises a metal, metalloid or silicon alkoxide containing at least one alkenoxy group; and initiating the hydrosilylation reaction to form the hybrid polymer.

Hybrid polymers derived from Si-H containing organosilicon polymers and

A method of forming preceramic polymers using an organosilicon polymer containing Si--H repeat units by reacting it with alkali metal amide or silylamide is disclosed. Preferably, the silylamide is a polymeric silylamide formed by reacting in solution anhydrous ammonia with a mixture of R.sup.1 SiHX.sub.2 (where R.sup.1 is a lower alkyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms; and X is a halogen) and R.sup.2 SiX.sub.3 (where R.sup.2 is H, a lower alkenyl group having from 1 to about 6 carbon atoms, a substituted or unsubstituted cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower alkenyl group having from 2 to about 6 carbon atoms or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms). The Si--H containing organosilicon polymer is preferably selected from the group consisting of organopolysilanes of the formula [(RSiH).sub.x (RSi).sub.y ].sub.n (where R is a lower alkyl group having from 1 to about 6 carbon atoms, a lower alkenyl group having from 2 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and n is greater than 1), a polycarbosilane having repeat units of the formula [R.sup.a Si(H)--(CH.sub.2).sub.q ] (where R.sup.a is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, q is an integer 1 or greater), and a polysiloxane having repeat units of the formula [R.sup.b Si(H)O].sub.n (where R.sup.b is a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, or a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, and n is an integer greater than 1). Novel preceramic polymers formed by this method are also disclosed.

Method for converting organosilicon polymers containing SIH repeat units

A method for preparing preceramic polymers is disclosed. This method includes the steps of

Organopolysilazane precursors to silicon nitride-rich mixed SiC/Si.sub.3

A method of forming preceramic polymers by mixing (A) an organic polysilane, preferably either a methylpolysilane of the formula [(RSiH).sub.x (RSi).sub.y ].sub.n, (where R is a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, a tri(lower)alkyl- or di(lower)alkylsilyl group x+y=1, (x and y are each &gt;0 and also x=1, y=0), and n is an integer greater than 1) or a polycarbosilane having repeat units of the formula [R.sup.a Si(H)--(CH.sub.2).sub.q ], [R.sup.a Si(H)--CH.dbd.CH], and [R.sup.a Si(H)--C.tbd.C] (where R.sup.a is H, a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, q is an integer 1 or greater), with (B) an organic or organisilicon compound having at least two alkenyl groups and allowing the mixture to react is disclosed. Preferably, the alkenyl group is a vinyl group. The reaction is preferably initiated by the generation of reactive free radicals. Novel preceramic polymers formed by this method are also disclosed.

Growing community of inventors

Lexington, MA, United States of America

Dietmar Seyferth