Abstract: The siloxane compounds represented by the following formula: SiOa(OH)b(OR1)c(OR2)d wherein 1.0≦a≦1.6, 0≦b<0.3, 0.2≦c≦2.0, 0≦d≦1.4, 2a+b+c+d=4, R1 is a methyl or ethyl group, and R2 is an organic group different from R1.

Abstract: A polyalkoxysiloxane of the following rational formula: SiOa(OR)b(OH)c wherein R is a C1-4 alkyl group, a=0.86 to 1.30, b=2.18 to 1.30, and c≦0.10.

Abstract: A process for producing synthetic quartz powder which comprises calcining silica gel powder to produce a synthetic quartz glass powder, wherein dry air is used in the calcining process at least in the process of cooling from 800.degree. C. to 200.degree. C. This process enables efficient production of synthetic quartz glass powder on an industrial scale.

Abstract: A synthetic quartz glass powder obtained by sol-gel method, wherein the number of black spot particles is at most 5 particles per 50 g, provides a high quality quartz glass shaped product with low bubble content when fused.

Abstract: A curable composition comprising an aged mixture of tetramethoxysilane with water added in excess of the theoretical amount sufficient for the hydrolysis and condensation of 100% of the silane and a reactive organic compound having at least two functional groups capable of condensing with the product of hydrolysis and condensation of the silane in the above mixture.

Abstract: A synthetic silica glass powder obtained by calcining a silica gel powder obtained by hydrolysis of a tetraalkoxysilane, said synthetic silica glass powder containing from 1.times.10.sup.-1 to 1.times.10.sup.-4 ppm of boron and having an internal silanol group concentration of at most 150 ppm and an isolated silanol group concentration of at most 5 ppm.

Abstract: An alumina fiber structure of a flat shape composed of alumina fibers having an alumina content of at least 65% by weight, the majority of said fibers being oriented substantially in parallel with the flat surfaces of the structure, and a number of fiber strands composed of the same alumina fibers extending inwardly from the flat surfaces of the structure, said structure having a thickness of from 4.8 mm to less than 10 mm, a density of from 0.07 to 0.3 g/cm.sup.3, a tensile strength of at least 0.5 kg/cm.sup.2 and a peeling strength of at least 0.5 kg/m.

Abstract: Alumina fiber structures prepared by (i) preparing precursor fibers by spinning a viscous spinning solution containing compounds of metals including aluminum and an organic polymer compound in which the proportion of alumina in the total metals in the solution is at least 65% by weight of alumina when all metals are calculated as their oxides; (ii) laying the precursor fibers into a mat; (iii) applying a lubricant which is a solution of higher fatty acid ester in a hydrocarbon solvent to the fibers either before or after forming the mat; (iv) needling the lubricated mat; and (v) burning the obtained structure to convert the precursor fibers to alumina fibers, possess high tensile strengths and high peel strengths.

Abstract: An inorganic fiber composed essentially of fine crystals of an aluminum compound, which contains at least 10% by weight of aluminum nitride and the rest of the aluminum compound being alumina.

Abstract: An alumina fiber structure of a flat shape composed of alumina fibers having an alumina content of at least 65% by weight, the majority of said fibers being oriented substantially in parallel with the flat surfaces of the structure, and a number of fiber strands composed of the same alumina fibers extending inwardly from the flat surfaces of the structure, said structure having a thickness of at least 10 mm, a density of from 0.07 to 0.3 g/cm.sup.3, a tensile strength of at least 0.5 kg/cm.sup.2 and a peeling strength of at least 0.5 kg/m.

Abstract: A process for treating a gas containing a fluorine compound which comprises the steps of contacting said gas with an aqueous solution as an absorbent containing aluminum fluoride and sulfate radical at a concentration of 3 to 30 g/l to absorb the fluorine compound, producing a solid phase including aluminum fluoride hydrate and/or basic aluminum fluoride by adding aluminum hydroxide and/or alumina to the resultant aqueous solution obtained in the absorbing step, and separating said solid phase from a slurry containing said solid phase obtained in the producing step.