Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/515—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics
  • C04B35/56—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides
  • C04B35/565—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides based on silicon carbide
  • C04B35/573—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on carbides or oxycarbides based on silicon carbide obtained by reaction sintering or recrystallisation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/90—Carbides
  • C01B32/914—Carbides of single elements
  • C01B32/956—Silicon carbide
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/90—Carbides
  • C01B32/914—Carbides of single elements
  • C01B32/956—Silicon carbide
  • C01B32/963—Preparation from compounds containing silicon
  • C01B32/97—Preparation from SiO or SiO2
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/10—Solid density
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/12—Surface area
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2006/00—Physical properties of inorganic compounds
  • C01P2006/80—Compositional purity

Definitions

• This invention relates to silicon carbide bodies a in particular, to the production of bodies of self-bond silicon carbide by reaction sintering of a preformed mixture of particles of silicon carbide and carbon in the presence of molten silicon.
• reaction sintering is hereinafter referred to as "siliconising” and one method of siliconising is described in UK patent Specification 1,180,918.
• the present invention consists in a self-bonded silicon carbide body produced by siliconising a preformed mixture of particles of carbon and silicon carbide wherein the silicon carbide in the mixture is in the beta form and the silicon carbide in the body has a mean grain size in the range 0.1-5 microns.
• Tb.e present invention also consists in a method of producing a self-bonded silicon carbide body by siliconising a preformed mixture of particles of carbon and silicon carbide in the beta form, the silicon carbide particles having a mean surface area in the range 0.5-20 square metres per gram, and in a self-bonded silicon carbide body so produced.
• a self-bonded silicon carbide body in accordance with the invention when compared with a self-bonded silicon carbide body produced using particles of aloha silicon carbide has improved properties, in particular in the extent and nature of deformation and microcracking around indentations. For example in 500g load knoop indentation tests cracking was much more localised and damage far less extensive. Also there is a greater dependence of hardness on load and may be higher hardness at low loads. These results indicate that bodies in accordance with the invention will behave in general in a more plastic manner have less tendency to crack catastrophically and show greater wear resistance and surface toughness.
• the coherent mixture of silicon carbide and carbon may be formed prior to siliconising by any convenient method such as extrusion, injection moulding, slipcasting or pressing.
• the fine silicon carbide particles in beta form are preferably produced by passing silicon monoxide through a bed of particulate carbon which is converted to silicon carbide powder, the silicon monoxide vapour being generated by heating a mixture of silica and silicon separately from the bed of particulate carbon.
• the silicon carbide powder had a surface area of 3.7 m 2 /g and the carbon powder consisted of crystallites which formed agglomerates with a surface area of about 6 m 2 /g.
• the pellet was extruded through a profiled die to form components of uniform cross-section and the extrudate was cut and heated to 400°C to volatilise the binder.
• Example 2 A mix containing carbon and beta-silicon carbide powders of the same size as in Example 1 but in the ratio 0.25:1 by weight, and sufficient polymeric binder to form a hard rigid body on compaction, was pressed isostatically at about 100 MN/m 2 to form a component which was subsequently 'green machined', using a diamond tool. The 'green' material was heated to 400°C to volatilise the binder an was then fired at 1650°C in the presence of molten silicon to convert it to a 90% dense silicon carbide containing free silicon.
• Example 3 A mix containing carbon and beta-silicon carbide powders of the same size as in Example 1 but in the ratio 0.25:1 by weight, and sufficient polymeric binder to form a hard rigid body on compaction, was pressed isostatically at about 100 MN/m 2 to form a component which was subsequently 'green machined', using a diamond tool. The 'green' material was heated to 400°C to volatilise the bin
• Beta silicon carbide powder surface area 2 m 2 /g, was mixed with carbon black, surface area 5 m /g, in the ratio 1:0.4 by weight.
• An aqueous slip was made up and a slip-cast slab was made.
• the slab was dried and siliconised at 1650oC for 2 hours in a vacuum of 1 torr. After cooling excess silicon was removed from the surface by abrasive blasting and the density of the slab was found to be 3.04g/cm 3 that is, it contained 19% by volume free silicon.
• the mean grain size in the slab was approximately 0.7 micro
• Example 4 Beta silicon carbide powder, surface area 4.4 m 2 /g vss mixed with carbon black, surface area 6 m 2 /g, in the ratio of 1:0.3.
• a slab was formed as in Example 3 and siliconised at 1600oC for 30 minutes.
• the density was 2.92 g/cm 3 (33% by volume free silicon) and the mean grain size was 0.5 microns.
• Example 5 A beta silicon carbide powder, surface area 0.8 m 2 /g was mixed with graphite powder, surface area 60 m /g in the ratio 1:0.4 by weight. Binder and lubricants were mixed in and rods 4 mm in diameter were extruded. After removal of the binder the rods were siliconised at 1650°C for 2 hours in a vacuum of 1 torr. Density of the rod was 3.12 g/

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• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
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• 1980
  • 1980-10-27 JP JP55502388A patent/JPS57501578A/ja active Pending
  • 1980-10-27 DE DE803050618A patent/DE3050618A1/de not_active Withdrawn
  • 1980-10-27 WO PCT/GB1980/000182 patent/WO1982001545A1/en active Application Filing
  • 1980-10-27 EP EP80901959A patent/EP0063112A1/de not_active Withdrawn

Non-Patent Citations (1)

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