Abstract: A thermal protection system (TPS) comprising a mixture of silicon carbide and SiOx that 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/SiOx frustules receives radiation, associated with atmospheric (re)entry, a portion of this radiation is reflected so that radiation loading of the heat shield is reduced.

Abstract: A tough ultra-high temperature ceramic (UHTC) composite comprises grains of UHTC matrix material, such as HfB2, ZrB2 or 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.

Abstract: A Porous ceramic filter and its method of production are disclosed. The ceramic filter has at least one porous layer (or skin) made of a binder formed of a cured ceramic powder and a preceramic or pyrolyzed ceramic precursor optionally containing a source of zirconia. In some embodiments, the binder is formed of the zirconia source only. The presence of the zirconia gives a skin with good mechanical strength and corrosion resistance to both acidic and basic solutions.

Abstract: 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.

Abstract: 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:Contacting an anhydrous composition of an alkali metal, alkaline earth metal, transition metal, lanthanide metal, actinide metal, or mixtures thereof substituted with an organic or an inorganic carbon-containing substitute with flowing nitrogen dioxide, dinitrogen tetroxide or mixtures thereof at a temperature of between about 40.degree. to 150.degree. C. under anhydrous conditions for a time and at a pressure effective to form the nitrate of the alkaline metal, alkaline earth metal, transition metal, lanthanide metal, actinide metal, or mixtures thereof, essentially free of any carbon containing contaminant. Materials produced by this improved process are useful as electrical superconductors, e.g. YBa.sub.2 Cu.sub.3 O.sub.

Abstract: The present invention pertains to a method of preparing particles of superconducting ceramic powders, which method comprises:(a) dissolving the soluble salts of the cations in aqueous medium;(b) obtaining a solution having pH of between about 4 and 7 by optionally treating the aqueous medium with ammonia, or ammonium hydroxide;(c) atomizing the solution of step (b) onto liquid nitrogen at about -196.degree. C.;(d) removing the liquid nitrogen by evaporation;(e) removing the water by sublimation at reduced pressure;(f) heating the solid residue of step (e) at 40-60.degree. C. at reduced pressure;(g) calcining the solid residue in flowing oxygen or air at temperature of between about 200.degree. to 895.degree. C.; and(h) cooling the solid at a temperature of between about 900.degree. C. and ambient temperature in sufficient air or oxygen and recovering the superconducting powder having an average diameter of between about 0.1 and 10 microns.

Abstract: 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.

Abstract: 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.