Central Glass Company, Limited

Naoki Okada

Shinsuke Nakagawa

Soichi Asagao

Noboru Murata

Yoshiyuki Takahara

Hiroshi Ueda

Masaru Nakatani

Midori Kawahara

Yasushi Kita

Shoichi Tsujioka

Hiromi Sugimoto

Takamitsu Enomoto

Seizi Yoshikawa

Takamitsu Eonomoto

The invention relates to water-repellent composite grains. Each composite grain includes: a first grain; and a low molecular weight polytetrafluoroethylene (PTFE) covering the first grain. The first grain is higher than the PTFE in mechanical strength. With this, the composite grains are improved in mechanical strength. A water-repellent article is produced by anchoring the composite grains to a substrate through an adhesive layer formed on the substrate. The composite grains are partly exposed on the adhesive layer and partly submerged in the adhesive layer. With this, the water-repellent article is made minutely rough. The water-repellent article is improved in mechanical strength and water repellency.

Water-repellent composite grains, method for producing same, and

To produce a modified barium titanate ceramic which is semiconductive and sufficiently high in breakdown voltage and has a low specific resistance at room temperature and a high positive temperature coefficient (PTC) of resistance, the invention provides a powder composition comprising (A) a basic mixture consisting of 45-85 mol % of BaTiO.sub.3 powder, 1-20 mol % of SrTiO.sub.3 powder, 5-20 mol % of CaTiO.sub.3 powder and 1-20 mol % of PbTiO.sub.3 powder, (B) a source of a dopant element such as Nb, Sb, Y, La or Ce to render the ceramic semiconductive, (C) a source of Mn such as MnC.sub.2 O.sub.4 and/or a source of Cu such as CuO added such that the total amount of Mn and Cu is not more than 0.06 mol % on the basis of the quantity of the mixture (A) with proviso that the amount of Mn is not more than 0.025 mol % and (D) SiO.sub.2 amounting to 0.1-2.0 mol % on the basis of the quantity of the mixture (A). The BaTiO.sub.3 powder and the SrTiO.sub.3 powder are produced by calcining BaTiO(C.sub.2 O.sub.4).sub.2 and SrTiO(C.sub.2 O.sub.4).sub.2, respectively, and in each of these powders very fine primary particles agglomerate to constitute porous and coarse secondary particles (about 100-200 .mu.m). The PbTiO.sub.3 powder may be produced by calcining PbTiO(C.sub.2 O.sub.4).sub.2 so as to have nearly the same structure as the BaTiO.sub.3 and SrTiO.sub.3 powders. The aimed ceramic is produced by compacting the powder composition into a green body and sintering it at 1300.degree.-1400.degree. C.

Powder composition for sintering into modified barium titanate

A modified lead barium titanate ceramic which has a fundamental composition of (Ba.sub.1-x-y Sb.sub.y Pb.sub.x)TiO.sub.3, where x is not greater than 0.9 and usually not smaller than 0.6 and y is from 0.001 to 0.1, and has a high positive temperature coefficient of resistivity (PTCR) over a range of temperature higher than about 350.degree. C. at the lower boundary, is produced by using a metal salt of an organic acid such as lead titanate salt of oxalic acid as the source of Pb and by adding at least one of BaCO.sub.3, SiO.sub.2, BN and TiO.sub.2 to the raw materials of the above fundamental composition. After thermally decomposing the organic acid metal salt the mixture of the raw materials including the additive(s) is compacted and sintered. By this method the sintering is achieved with good reproducibility and with little dissipation of lead, and the obtained titanate ceramic is good and durable in the PTCR characteristics and hence is useful as the material of a PTC thermistor functioning at medium-to-high temperatures.

Method of producing modified lead barium titanate ceramic useful as PTC

An economically advantageous method of recovering uranium from a wet process phosphoric acid solution through the steps of making hemihydrate gypsum contact with the acid solution thereby transferring uranium from the acid solution into the gypsum, dispersing the U-containing gypsum separated from the acid solution in water to convert the gypsum to dihydrate accompanied by the transfer of uranium into water, separating the obtained U-containing aqueous solution from the dihydrate gypsum, and adding precipitant such as an inorganic base to the aqueous solution to form a precipitate comprising an insoluble uranium compound. The contact of hemihydrate gypsum with the phosphoric acid solution is preferably preceded by reduction of hexavalent uranium in the acid solution to tetravalent uranium, and can be achieved either by adding hemihydrate gypsum to the acid solution or by converting dihydrate gypsum to hemihydrate within the acid solution preferably preceded by the addition of sulfuric acid.

Method of recovering uranium from wet process phosphoric acid

A process for preparing crystalline ammonium dihydrogen phosphate, comprises the steps of (a) adding a sequestering agent into ammonium hydrogen phosphate aqueous solution, the sequestering agent reacting with metallic ions contained in the aqueous solution to form water solouble compounds, (b) heat-treating the aqueous solution at a temperature of 70.degree. C. or more after addition of the sequestering agent, and (c) crystallizing ammonium dihydrogen phosphate out of the aqueous solution after the heat-treating, so that crystalline ammonium dihydrogen phosphate can be obtained in high whiteness and in the form of columnar crystals.

Process for preparing crystalline ammonium dihydrogen phosphate

A process for preparing crystalline ammonium dihydrogen phosphate, comprises the steps of (a) adding a sequestering agent into ammonium hydrogen phosphate aqueous solution, the sequestering agent reacting with metallic ions contained in the aqueous solution to form water soluble compounds, (b) heat-treating the aqueous solution at a temperature of 70.degree. C. or more after addition of the sequestering agent, and (c) crystallizing ammonium dihydrogen phosphate out of the aqueous solution after the heat-treating, so that crystalline ammonium dihydrogen phosphate can be obtained in high whiteness and in the form of columnar crystals.

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Ube, Japan

Naoki Okada