Abstract: An anti-corrosion ceramic member having a substrate made of a ceramic material, a surface layer made of a fluoride and formed on the substrate, and an intermediate layer formed between the substrate and the surface layer and having the ceramic material of the substrate and the fluoride.

Abstract: A base member made of a metal in which aluminum is included, ceramics in which an aluminum element is included, or a composition member constructed by a metal in which aluminum and ceramics are included, is provided in a container in which a solid fluorine compound such as NaHF2 is filled. Then, the container is heated at a temperature higher than a decomposition temperature of the solid fluorine compound. After that, the base member is subjected to a heat treatment with the decomposed gas of the solid fluorine compound to form a fluoride layer on a surface of the base member. In this manner, it is possible to obtain an anti-corrosion member which shows a high corrosion property with respect to the corrosion gas of halogen series and its plasma, particularly with respect to chlorine gas and its plasma.

Abstract: A method for producing a silicon carbide body, includes the steps of forming a silicon carbide mass by chemical vapor deposition, and thermally treating the silicon carbide mass under vacuum or in an inert gas atmosphere at a temperature not less than 2000° C., the silicon carbide article having an electric resistivity higher than that of the silicon carbide mass having not been thermally treated.

Abstract: An anti-corrosion ceramic member having a substrate made of a ceramic material, a surface layer made of a fluoride and formed on the substrate, and an intermediate layer formed between the substrate and the surface layer and having the ceramic material of the substrate and the fluoride.

Abstract: A sintered ceramic part to be exposed to a corrosive gas, a surface of said ceramic part being machined, wherein each of grains exposed to the machined surface of the ceramic part is formed with a machined surface, and en edge of the machined surface of each of these grains is made round by material transfer. A process for producing such a sintered ceramic part includes the steps of: obtaining a machined body having a given shape by at least grinding a surface of a ceramic sintered body, and annealing the machined body.

Abstract: A process is disclosed for producing a corrosion-resistant ceramic member, which process includes the steps of preparing a sintered body made of a ceramic material containing at least aluminum, immersing the ceramic sintered body in hydrofluoric acid, and forming a film of aluminum fluoride at a surface layer portion of the ceramic sintered body by heating the ceramic sintered body.

Abstract: A silicon nitride sintered material includes silicon nitride and rare earth element compounds. Y and Yb are contained as the rare earth elements in a total amount of 5-7 mole % in terms of oxides, Yb/Y is 4/6 to 9/1 in terms of molar ratio of oxides, and the crystal phases of grain boundary contain a H phase and a J phase with the proportion of the H phase being larger than that of the J phase. A process for producing a silicon nitride sintered material includes the steps of mixing a Si.sub.3 N.sub.4 powder with Y.sub.2 O.sub.3 and Yb.sub.2 O.sub.3 both as a sintering aid, the total amount of Y.sub.2 O.sub.3 and Yb.sub.2 O.sub.3 being 5-7 mole % and the molar ratio of Yb.sub.2 O.sub.3 /Y.sub.2 O.sub.3 being 4/6 to 9/1, molding the resulting mixture, sintering the molded material in a nitrogen atmosphere at 1,850-1,950.degree. C., and heat-treating the sintered material in air at 1,000-1,500.degree. C. for 0.5-10 hours.

Abstract: A gas-tight article includes a sintered body composed mainly of a silicon carbide, and a film of silicon carbide formed on a surface of the sintered body by chemical vapor deposition and covering said surface of the sintered body, wherein cracks are formed in the film of the silicon carbide, and the cracks are filled with metallic silicon.

Abstract: A method of forming a film of boron carbide on a substrate is provided, which comprises the steps of forming the boron carbide film on a surface of a substrate by plasma spraying, and heating the film at 1100.about.2400.degree. C. in a non-oxidizing atmosphere, whereby boron oxide contained in the boron carbide film is removed.

Abstract: A silicon nitride sintered material includes silicon nitride and rare earth element compounds. Y and Yb are contained as the rare earth elements in a total amount of 5-7 mole % in terms of oxides, Yb/Y is 4/6 to 9/1 in terms of molar ratio of oxides, and the crystal phases of grain boundary contain a H phase and a J phase with the proportion of the H phase being larger than that of the J phase. A process for producing a silicon nitride sintered material includes the steps of mixing a Si.sub.3 N.sub.4 powder with Y.sub.2 O.sub.3 and Yb.sub.2 O.sub.3 both as a sintering aid, the total amount of Y.sub.2 O.sub.3 and Yb.sub.2 O.sub.3 being 5-7 mole % and the molar ratio of Yb.sub.2 O.sub.3 /Y.sub.2 O.sub.3 being 4/6 to 9/1, molding the resulting mixture, sintering the molded material in a nitrogen atmosphere at 1,850-1,950.degree. C., and heat-treating the sintered material in air at 1,000-1,500.degree. C. for 0.5-10 hours.

Abstract: A process for the production of a lanthanum chromite film, including the steps of preparing a plasma spray powder by mixing 1-15 parts by weight of powdery chromium oxide powder to 100 parts by weight of powdery lanthanum chromite, this lanthanum chromite having a composition ratio of A sites to B-sites being in a range of 1:1 to 1:0.9, forming a plasma sprayed film by plasma spraying the plasma spray powder onto a substrate, and forming the lanthanum chromite film by heat treating the resulting plasma sprayed film. The plasma spray powder may be produced by preparing a mixed powder by adding 1-15 parts by weight of powdery chromium oxide to 100 parts by weight of a synthesis powder capable of producing the lanthanum chromite film by heat treatment, the synthesis powder containing at least chromium oxide and lanthanum chromite and the lanthanum chromite film having a composition ratio of A-sites to B-sites being in a range of 1:1 to 1:0.