Abstract: A process for producing a glass having a rod refractive index distribution, which includes pressing a glass at a temperature below the glass transition temperature to form a glass having a density increased towards the surface layer thereof, or alternatively includes heating a glass at a temperature around the transition temperature at the lowest to prepare glass having a uniformly enhanced density and heating the treated glass under a pressure lower than the applied pressure at a temperature below the glass transition temperature of the glass to prepare a rod glass having a density increased towards the central portion.

Abstract: A process for producing a rod glass having a refractive index distribution, which includes pressing a glass at a temperature below the glass transition temperature to form a glass having a density increased towards the surface layer thereof, or alternatively includes heating a glass at a temperature around the transition temperature at the lowest to prepare glass having a uniformly enhanced density and heating the treated glass under a pressure lower than the applied pressure at a temperature below the glass transition temperature of the glass to prepare a glass having a density increased towards the central portion.

Abstract: A process for the preparation of a micro-cellular porous ceramic body is disclosed, in which an .alpha.-olefin oligomer is added as a molding assistant to an ultrafine ceramic powder in an amount of 65 to 330% by weight based on the ultrafine ceramic powder, the mixture is kneaded, the kneaded mixture is compression-molded to give a molded body, and the molded body is fired.

Abstract: A method for the adhesion of oxide type ceramics and copper or a copper alloy is provided by this invention, which method comprises placing the oxide type ceramics and the copper or copper alloy in mutual contact, heating them in an oxidative atmosphere thereby effecting adhesion thereof, and rapidly cooling the resultant composite of adhesion. The adhesive strength of the composite of adhesion so produced is about 40% higher than the adhesive strength of a similar composite of adhesion obtained by the conventional method involving gradual cooling.

Abstract: A composition of at least one member selected from the group consisting of sodium fluoride and calcium fluoride and optionally containing kaolin is powerful adhesive for ceramic articles which is used by interposing the adhesive intimately between the opposed surfaces for union of the ceramic articles and heating the adhesive to a temperature equal to or higher than the decomposition temperature of the fluoride used.

Abstract: An adhesive having as its active component at least one fluoride selected from the group consisting of alkali metal fluorides except for sodium fluoride and alkaline earth metal fluorides except for calcium fluoride or a combination of the aforementioned at least one fluoride with kaolin and an adhesive having as its active component a combination of at least one member selected from the group consisting of yttria and alkaline earth metal compounds except for fluorides, an alkali metal fluoride, and at least one member selected from the group consisting of kaolin and alkaline earth metal fluorides both provide fast adhesion easily between two ceramic articles by a method which comprises the steps of interposing the adhesive between the ceramic articles and heating the ceramic articles with the adhesive therebetween to a temperature equal to or higher than the decomposition temperature of the fluoride in the adhesive.

Abstract: A method for providing strong adhesion of two ceramic articles to each other or one ceramic article to an article of metallic copper, which method comprises applying, in the former adhesion, a powder mixture of CuS-LaCrO.sub.3 -SiO.sub.2 -Cu to the opposed surfaces of the two ceramic articles or, in the latter adhesion, a powder mixture of CuS-LaCrO.sub.3 -SiO.sub.2 to the opposed surfaces of the ceramic article and the article of metallic copper and, thereafter, heating the pair of articles in the air at a temperature of from 1000.degree. to 1200.degree. C.

Abstract: A method for providing strong adhesion of two ceramic articles to each other or one ceramic article to an article of metallic copper, which method comprises applying, in the former adhesion, a powder mixture of CuS--LaCrO.sub.3 --SiO.sub.2 --Cu to the opposed surfaces of the two ceramic articles or, in the latter adhesion, a powder mixture of CuS--LaCrO.sub.3 --SiO.sub.2 to the opposed surfaces of the ceramic article and the article of metallic copper and, thereafter, heating the pair of articles in the air at a temperature of from 1000.degree. to 1200.degree. C.

Abstract: A thin coating of silver is formed fast on the surface of a nitride type ceramic article by coating the surface of the ceramic article with a mixture consisting of copper sulfide and kaolin, subjecting the coated article to a thermal treatment in a nitrogen-containing atmosphere at a temperature in the range of from 900.degree. to 1300.degree. C., then overcoating the thermally treated ceramic article with silver carbonate and heating the overcoated article again in the nitrogen-containing atmosphere at a temperature in the range of from 700.degree. to 900.degree. C.

Abstract: Arc electrodes formed of the sinter of lanthanum chromite or of a compound having a part of the lanthanum component of lanthanum chromite replaced by at least one member selected from the group consisting of calcium, magnesium and strontium.