Sri International

United States of America As Represented by the Administrator of Nasa

University of California

Osaka Gas Company Limited

Sylvia M Johnson

Michael I Gusman

Angel Sanjurjo

Yigal Dov Blum

Gareth Thomas

David J Rowcliffe

Margaret M Stackpoole

Matthew J Gasch

John W Lawson

Ian W Hamby

Timothy R Dinger

Thomas H Squire

Gilbert Tong

Robert Lamoreaux

Hajime Nakano

Michael W Olson

Gopala Krishnan

A thermal protection system (TPS) comprising a mixture of silicon carbide and SiOthat has been converted from Si that is present in a collection of diatom frustules and at least one diatom has quasi-periodic pore-to-pore separation distance d(p-p) in a selected range. Where a heat shield comprising the converted SiC/SiOfrustules receives radiation, associated with atmospheric (re)entry, a portion of this radiation is reflected so that radiation loading of the heat shield is reduced.

Biologically inspired radiation reflector

A tough ultra-high temperature ceramic (UHTC) composite comprises grains of UHTC matrix material, such as HfB, ZrBor other metal boride, carbide, nitride, etc., surrounded by a uniform distribution of acicular high aspect ratio reinforcement ceramic rods or whiskers, such as of SiC, is formed from uniformly mixing a powder of the UHTC material and a pre-ceramic polymer selected to form the desired reinforcement species, then thermally consolidating the mixture by hot pressing. The acicular reinforcement rods may make up from 5 to 30 vol % of the resulting microstructure.

In-situ formation of reinforcement phases in ultra high temperature ceramic composites

A method is provided for preparing ceramic precursors from hydridosiloxane starting materials and then pyrolyzing these precursors to give rise to silicious ceramic materials. Si--H bonds present in the hydridosiloxane starting materials are catalytically activated, and the activated hydrogen atoms may then be replaced with nonhydrogen substituents. These preceramic materials are pyrolyzed in a selected atmosphere to give the desired ceramic product. Ceramic products which may be prepared by this technique include silica, silicon oxynitride, silicon carbide, metal silicates, and mullite.

Hydridosiloxanes as precursors to ceramic products

The present invention relates to an improved process to produce an essentially carbon-free nitrate of an alkali metal, alkaline earth metal, transition metal, lanthanide metal, actinide metal, metal, or mixtures thereof, which process comprises:

Carbonate-free inorganic nitrates or oxides and process thereof

The present invention pertains to a method of preparing particles of superconducting ceramic powders, which method comprises:

Cryochemical method of preparing ultrafine particles of high-purity

Production of carbide shapes of silicon, titanium or vanadium by reaction of carbon with the metal in liquid phase such being carried out by heating a mixture of particles of carbon and particles of the metal rapidly to the melting point of the metal, thereby minimizing solid state reaction, and holding at a temperature and for a time sufficient to cause reaction. The metal and carbon particles are about 0.05 to 10 mm in diameter. An organic binder is used which volatilizes or dissociates upon heating.

Production of metal carbides

An improved process for forming a dense silicon nitride compact having improved high temperature properties comprises: forming a glass using compounds, containing Al, Si, O, N, and a rare-earth element, known to form one or more crystalline phases; mixing this preformed glass in particulate form with silicon nitride powder; and densifying the mixture at an elevated temperature; and then forming one or more crystalline intergranular phases from the glass to thereby improve the high temperature characteristics of the resultant dense silicon nitride compact. In a preferred embodiment, the process includes heating the dense compact to a first temperature to form nucleates; and then heating the dense compact at a second temperature to grow the desired one or more crystalline intergranular phases on the nucleates. In another embodiment, the crystallization may be carried out by controlled direct cooling of the compact from the sintering temperature. The use of particles of a preformed glass, made from compounds known to form one or more crystalline phases, as the desification material provides a homogeneous mixture to ensure subsequent formation of the desired crystalline intergranular phases.

Method of producing a dense refractory silicon nitride (SI.sub.3

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Piedmont, CA, United States of America

Sylvia M Johnson