Louis Gates Mahone

Bio: Louis Gates Mahone is an academic researcher from Dow Corning. The author has contributed to research in topics: Ceramic & Sintering. The author has an hindex of 5, co-authored 7 publications receiving 106 citations.

Redistribution reactions in the chemistry of silicon

Abstract: In recent years there has been what could be described as a renaissance in the redistribution reaction, and the growing interest in the chemistry of the metalloids has been partially responsible for this renewed interest. The generality and potential synthetic utility of this reaction in the chemistry of silicon, germanium, tin, boron, and phosphorus has necessitated a better understanding of this type of chemical transformation. With the advancement of modern computation and instrumental analytical techniques, this need is slowly being realized. Of the above mentioned elements, the chemistry of silicon has probably been the most intensely studied during recent years and, thus, it is not surprising that the chemistry of silicon provides the most comprehensive picture of the redistribution reaction. The redistribution reaction has been the subject of recent reviews by Moedritzer'\" and by Lockhart3 which cover quite comprehensively the general application of this reaction to silicon chemistry. In this current brief review, we shall confine our attention to the simplest form of this reaction; namely, that involving the redistribution of monodentate ligands about a central silicon atom.

Sintering alpha silicon carbide powder with multiple sintering aids

Abstract: This invention relates to the preparation of highly densified ceramic bodies by the pyrolysis of a mixture comprising a carbon source, alpha silicon carbide powder, a source of boron and a source of aluminum. Such highly densified ceramic bodies are prepared by sintering under pressure or by a pressureless sintering process.

Stable methylpolydisilylazane polymers

Abstract: A method for producing methylpolydisilylazane polymers of reduced chloride content that exhibit no increase in pyrophoricity and exhibit improved shelf life. The methylpolydisilylazane polymers of reduced chloride content are useful in the production of silicon nitride and sil STATEMENT OF GOVERNMENT RIGHTS The United States Government has rights in this invention pursuant to Contract Number F33615-85-C-5006 awarded by the United States Air Force.

Method for producing functional silazane polymers

Abstract: The present invention relates to a method of producing silazane polymers with silicon functional groups attached to the nitrogen. The method comprises treating a silazane polymer containing an N-H bond with an alkyllithium and then reacting the resultant silazane polymer with a chlorosilane. The invention also relates to novel silazane polymers produced by the above process as well as the use of these polymers to form ceramic materials.

Redistribution Reactions on Silicon Catalyzed by Transition Metal Complexes

Abstract: Publisher Summary This chapter discusses redistributions catalyzed by transition-metal complexes. Redistribution, or disproportionation, constitutes an important class of reactions in organosilicon chemistry. Redistributions on silicon may be initiated by thermolysis or by catalytic activation at somewhat lower temperatures. In the gas phase, methyl is transferred from Me n SiH 4–n , to CH 3 + almost as readily as hydrogen. Silacyclobutanes with metal substituents may also be polymerized to give novel polymers with pendant metal groups. By using chiral silyl hydrides, it has been demonstrated that the exchanges occur with the retention of configuration at silicon. The complete lack of isomerization of the p -tolyl group during the disproportionation of Ar 3 SiH is noteworthy. Similarly, the vinyl group of trimethylvinylsilane is hydrolyzed by a catalytic amount of Zeise's salt [(C 2 H 4 )PtC1 3 ] - in moist acetone. The redistribution reactions of hydridodisilanes of the type R 3 SiSiR 2 H are more varied than those of the corresponding monosilanes. In redistribution reactions catalyzed by transition-metal complexes, di- or polysiloxanes are expected to share some characteristics of both monosilanes and di- or polysilanes. Thus, the availability of the four-membered metallacycle in the catalytic cycle greatly enhances the rate of disproportionation of tetramethyldisiloxane. Some of these catalytic cycles lead to products that appear to arise from divalent silylenoid species.

Preparation of Silicon Carbonitrides from an Organosilicon Polymer: I, Thermal Decomposition of the Cross-linked Polysilazane

Abstract: The conversion of a solid copolymer (ViSiHNH)x─(MeSiHNH)y into a ceramic was studied in the 20–1450°C temperature range under different atmospheres (inert or oxidative). The ceramic yield, the ceramic composition, and the gaseous evolution directly depend on the heating rate, the pyrolysis atmosphere, and the duration of pyrolysis. The implications of these observations to the pyrolysis mechanism are discussed. The silicon carbonitride obtained after pyrolysis is amorphous up to 1400°C with high carbon content. It will be shown in Parts II and III that either SiC or Si3N4 could be selectively crystallized depending upon processing conditions.

Photochemistry of Organopolysilanes

Abstract: Publisher Summary This chapter discusses the recent results on the photochemical generation and reactions of the silylenes and silicon–carbon double-bonded intermediates. The photochemical behavior of monosilanes has been investigated by mercury-sensitized photolysis, flash photolysis, vacuum ultraviolet photolysis, and matrix photolysis. All of the cyclic and acyclic permethylpolysilanes with the exception of hexamethyldisilane readily undergo photolysis on irradiation with ultraviolet light to give shorter chain compounds with the concurrent generation of the divalent silicon intermediate, dimethylsilylene. The silylene species generated during photolysis are thought to polymerize in the absence of a trapping agent. The photolysis of branched permethylpolysilanes is of considerable interest, because a novel silylene intermediate––trimethylsilylmethylsilylene––is produced. The photolysis of phenyl-substituted polysilanes also affords a convenient method for the generation of silylene species. The stereochemistry of photochemical generation of dimethylsilylene is reported. Hydrosilanes are one of the most suitable silylene trapping agents and are often used in photolysis. The yields of the silacyclopropanes are highly dependent on the structure of the olefins used. When tetramethylethylene is used as a quencher, only a trace of the methoxysilane is obtained along with small amounts of the silylalkenes.

Ceramics from Hydridopolysilazane

Abstract: The Advanced Ceramics Based on Polymer Processing Program is sponsored by the Defense Advanced Research Projects Agency (Materials Science Division). The objectives of the program include development of a family of Si-C, Si-N, and Si-C-N ceramic fibers which may be used for reinforcement in ceramic, metal and plastic matrices, and development of economical process technology for fabricating ceramic matrix composites with high fracture toughness, high temperature performance and no inherent limitations to forming complex shapes. Attainment of these objectives would circumvent two limitations of existing ceramic material technology - lack of design reliability due largely to catastrophic failure related to brittleness, and inability to fabricate complex shapes [1].