W. R. Grace Co.-conn.

W. R. Grace Co.

Nicholas D Spencer

John Allen Rudesill

Jean Willem Beeckman

Wie-Hin Pan

Leonard E Dolhert

Wie H Pan

The invention process provides a metal oxide, or oxides of more than one more metal, wherein the oxides have a mean particle size less than 1 micron. The oxides are made by steps including (1) reacting an aqueous solution of a metal salt (or salts) that form insoluble carbonate(s), thereby to form a carbonate precipitate, followed by (b) recovering the precipitate, e.g., by filtration; (c) redispersing the precipitate in water to form a second very dilute slurry; (d) spray-drying said second slurry; (e) calcining the spray-dried product at a low temperature (e.g., 540.degree. C.), followed by a final calcination in atmosphere consisting of flowing oxygen initially under reduced pressure (e.g., 2 Torr). The spray-dried spheroids comprise particles having a mean particle size less than one micron, a property carried over into the products of both calcinations.

Synthesis of submicron powders under reduced oxygen pressure

Superior homogeneity in ceramic materials is achieved by reacting certain soluble metal salts with quaternary ammonium carbonates to form co-precipitated metal carbonates. The precipitate can be recovered and processed to make superconductors. For example, a solution of nitrates of yttrium, barium, and copper are treated with a solution of tetraethyl ammonium carbonate to form co-precipitated carbonates of Y, Ba, Cu. The precipitate is recovered and calcined to form a superconducting material.

Manufacturing method for superconducting ceramics and products thereof

Two or more superconductors are reacted together to form a non-superconducting phase encapsulating a residual superconducting phase. For example YBa.sub.2 Cu.sub.3 oxide is reacted with Bi.sub.2 Sr.sub.2 CaCu.sub.2 oxide to form a superconducting product containing a novel non-superconducting oxide of Y, Bi, and Ba. A superconducting YBa.sub.2 Cu.sub.3 oxide remains as an interconnected phase throughout the product. The new non-superconducting phase largely encapsulates and insulates the superconducting phase.

Superconducting oxide FCC oxide composite compositions and method of

An extremely pure oxide containing two or more metals, homogeneous at the atomic level, is prepared by (1) reacting in water, soluble salts of two or more metals with quaternary ammonium carbonate; the metals being those that form water-insoluble carbonates, thereby to precipitate mixed carbonates of the metals; (2) recovering and drying the precipitate; (3) calcining the precipitate to provide an oxide of mixed metals homogeneous at the atomic level and substantially free from extraneous contaminants. The calcined oxide can be shaped and compressed as greenware and sintered to form useful ceramic products.

Manufacturing method for ceramics and products thereof

Improved process for making Tl-Ca-Ba-Cu oxide superconductors. A solution of the nitrated of Ca, Ba, and Cu is reacted with a quaternary ammonium carbonate in a slurry (heel) of Tl.sub.2 O.sub.3. Carbonates of Ca, Ba, and Cu precipitate homogeneously on the Tl.sub.2 O.sub.3 particles. Solids are recovered, dried, and heated to make a superconductor. The method minimizes introdution of contaminants. Novel compositions result.

Ceramic composition

Improved process for making Bi-Pb-Sb-Sr-Ca-Cu oxide superconductors. A solution of the nitrates of Bi, Pb, Sr, Ca, and Cu is reacted with a quaternary ammonium carbonate in a dispersion (heel) of Sb.sub.2 O.sub.5. Carbonates of Bi, Pb, Sr, Ca, and Cu precipitate homogeneously on the Sb.sub.2 O.sub.5 particles. Solids are recovered, dried, and heated to make a superconductor. The method minimizes handling toxic antimony compounds and reduces introduction of contaminants. Novel compositions result.

An inorganic powder is vibrated while being calcined. The vibrations suspend the powder as in a conventional gas-fluidized system, without clumping, but without loss of fines. As applied to superconductor precursor powders, the treatment accelerates growth of the superconducting phase. The invention includes a novel furnace system for simultaneously heating and vibrating the powders.

Vibratory calcination of inorganic oxide superconductor precursor powders

Formaldehyde is made from methane and a molecular oxygen containing gas by using a silica supported catalyst having less than 350 parts per million by weight of sodium and having a catalytically effective amount of V.sub.2 O.sub.5. The low sodium form of the silica support can be made by washing silica gel or precipitated silica or by using a fumed silica. In general, the lower the sodium level, the better is the catalyst.

Process for the production of formaldehyde from methane

Formaldehyde is made from methane and a molecular oxygen containing gas by using a silica supported catalyst having less than 350 parts per million by weight of sodium and having a catalytically effective amount of MoO.sub.3. The low sodium form of the silica support can be made by washing silica gel or precipitated silica, by using a fumed silica or by making an ultrapure form of silica having a silica purity of at least 99.99% silica. The ultrapure form can be made by the hydrolysis of silicon tetraalkoxides. In general, the lower the sodium level, the better is the catalyst.

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Washington, DC, United States of America

Nicholas D Spencer