Abstract: This invention provides a protective member comprising a ceramic body comprising a plurality of first phases (2) composed mainly of silicon carbide and a plurality of second phases (3) having a composition different from the composition of the first phase (2) and containing at least boron, silicon and carbon. A part of the second phase is present in the first phase as a whole, and at least a part of the remaining part of the second phase is present between a plurality of the first phases.

Abstract: A boron carbide sintered body having a plurality of pores, comprises a boron carbide as a main component and a plurality of graphite particles dispersed in the sinter. The graphite particles is exposed to the pores or is in the vicinity of the pores.

Abstract: The compressive strength of a boron carbide sintered compact is improved by controlling crystals of the boron carbide to a polycrystalline structure having a grain size distribution in which coarse crystals with a grain size of 20 ?m or more and fine crystals with a grain size of 10 ?m or less are mixed in an appropriate ratio. Furthermore, a protective member having an improved compressive strength can be provided using the boron carbide sintered compact having a polycrystalline structure in which coarse crystals and fine crystals are mixed in an appropriate ratio or a boron carbide sintered compact containing graphite and silicon carbide.

Abstract: A boron carbide sintered body having a plurality of pores, comprises a boron carbide as a main component and a plurality of graphite particles dispersed in the sinter. The graphite particles is exposed to the pores or is in the vicinity of the pores.

Abstract: The compressive strength of a boron carbide sintered compact is improved by controlling crystals of the boron carbide to a polycrystalline structure having a grain size distribution in which coarse crystals with a grain size of 20 ?m or more and fine crystals with a grain size of 10 ?m or less are mixed in an appropriate ratio. Furthermore, a protective member having an improved compressive strength can be provided using the boron carbide sintered compact having a polycrystalline structure in which coarse crystals and fine crystals are mixed in an appropriate ratio or a boron carbide sintered compact containing graphite and silicon carbide.

Abstract: This invention relates to a corrosion-resistant member used in a region in which a gas or a plasma of a halogen-containing compound is used, in a process for producing semiconductors, especially a member used as jigs such as a supporter for supporting a material to be treated, or as an inner wall member in an apparatus for producing semiconductors, which has a high corrosion resistance to a fluorine type or a chlorine type corrosive gas, or a fluorine type or a chlorine type plasma. According to this invention, there are provided a corrosion-resistant member to be used ina region in which a gas or plasma of a halogen compound is used in a process of producing a semiconductor, wherein at least surface exposed to the gas or plasma is formed of a boron carbide sintered body having a relative density of at least 96% and containing 300 ppm or below, in a total amount, of an alkali metal, an alkalin earth metal and a transition metal, and a process for producing the same.

Abstract: Disclosed is a composite ceramic sintered material comprising a surface layer of a composition which contains the silicon nitride and carbon, and an internal portion of the silicon carbide or a combination of the silicon carbide, silicon nitride and carbon, the content of carbon or the content of the silicon nitride being greater in the surface layer than in the internal portion.

Abstract: A silicon nitride-silicon carbide composite sintered material which comprises 100 parts by weight of a silicon nitride component containing 92 to 99.5 mol % of silicon nitride including excessive oxygen and 0.5 to 8 mol % of the elements of Group IIIa in the Periodic Table as corresponding oxides thereof and 1 to 100 parts by weight of a silicon carbide component in a dispersed state, wherein the silicon nitride component has an average particle size of 1 .mu.m or less and an average aspect ratio of 2 to 10, and the silicon carbide component has an average particle size of 1 .mu.m or less, moreover, the total amount of Al, Mg, Ca respectively contained in the sintered material as calculated as oxides thereof is 0.5% by weight or less, and a manufacturing method thereof.According to the above-mentioned composite sintered material, it becomes possible to suppress deterioration of strength at 1400.degree. C. and realize excellent creep properties.

Abstract: Disclosed is a composite ceramic sintered material comprising a surface layer of a composition which contains the silicon nitride and carbon, and an internal portion of the silicon carbide or a combination of the silicon carbide, silicon nitride and carbon, the content of carbon or the content of the silicon nitride being greater in the surface layer than in the internal portion.