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
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/009—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone characterised by the material treated
• • 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
  • C04B35/58—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 borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
  • C04B35/581—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 borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on aluminium nitride
• • 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
  • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/64—Burning or sintering processes
  • C04B35/65—Reaction sintering of free metal- or free silicon-containing compositions
  • C04B35/652—Directional oxidation or solidification, e.g. Lanxide process
• • 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
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/45—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements
  • C04B41/50—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials
  • C04B41/5053—Coating or impregnating, e.g. injection in masonry, partial coating of green or fired ceramics, organic coating compositions for adhering together two concrete elements with inorganic materials non-oxide ceramics
  • C04B41/5062—Borides, Nitrides or Silicides
  • C04B41/5063—Aluminium nitride
• • 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
  • C04B41/00—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone
  • C04B41/80—After-treatment of mortars, concrete, artificial stone or ceramics; Treatment of natural stone of only ceramics
  • C04B41/81—Coating or impregnation
  • C04B41/85—Coating or impregnation with inorganic materials
  • C04B41/87—Ceramics
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/10—Alloys containing non-metals
  • C22C1/1036—Alloys containing non-metals starting from a melt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/16—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on nitrides

Definitions

• the present invention relates to a new method for the preparation of composite materials comprising aluminium nitride and aluminium metal.
• Composite materials of ceramic particles or fibres with metallic matrix have been used for various purposes for decades.
• the materials are often prepared powder metallurgically, by preparing a powder mixture of the components in question, shaping the articles by known shaping methods and then sintering the articles at optimal temperatures in a furnace atmosphere with the desired gas composition and total pressure.
• the ceramic particles may be blended in liquid metal and the material then shaped for instance by casting.
• a third method - which is used particularly for fiber containing composites - is infiltration of liquid metal in a fibre matrix packed to the desired density in a container (preform) .
• the present invention there is provided a method for the preparation of articles of composite materials comprising aluminium nitride and aluminium metal.
• the method is characterized in that a porous silicon nitride article is infiltrated with liquid aluminium, and reaction between silicon nitride and penetrated aluminium is accomplished at a temperature above the melting point of aluminium.
• the present invention is based on coversion in situ of silicon nitride to aluminium nitride by addition of liquid aluminium, as illustrated by the reaction equation:
• the silicon nitride starting material may be prepared by various methods, however, it is preferred to let silicon metal react with nitrogen at an elevated temperature, as per se known.
• the silicon powder may suitably be given a shape similar to the desired final shape, whereafter sintering and nitriding are carried out. It is not necessary that all the silicon is nitrided, as possible residues of Si in the silicon nitride do not have any adverse effects. In some cases it even seems as if it is advantageous for the following conversion.
• a greatly cost-increasing step in the production is often the post treatment of the sintered ceramics or ceramic/metal composite. This is due to the fact that most of these materials are very hard and are difficult to process with traditional abrasive and machinery means.
• processing problems may be essentially simplified if the sintering is carried out in two steps. First, partial sintering and nitriding is carried out at 1100-1200°C, then the necessary machining is done and the final nitriding is carried out at about 1400°C. The nitriding entails only insignificant changes in the outer dimensions.
• Another advantage obtained by the described preparation method is that in the finished product, • there are strong direct-bonds between the individual aluminium nitride particles, so that the mechanical strength is not dramatically changed at temperatures above the melting point of the metal phase. These bonds are established by the nitriding of silicon during the preparation of the silicon nitride article, and the bonds seem to be maintained during the conversion to aluminium nitride.
• the electrical conductivity of the material is strongly dependant i.a. on the amount ratio between nitride and metal phase.
• the electrical conductivity may be varied within broad ranges, for instance by choosing silicon nitride materials with different porosity and pore distribution. If the composite material in question primarily is to serve as an electrically conducting material, it would be correct to use a relatively porous silicon nitride material. However, if the material primarily is to serve as a construction material, it is logical to make the conversion with a more dense and strong silicon nitride material.
• the silicon nitride starting material instead of carrying out the infiltration of the silicon nitride starting material with aluminium, it may also be done with an aluminium alloy, and numerous alloying elements are then possible, for instance magnesium, copper, zinc etc. A better penetration of the silicon nitride starting material may then be obtained, and also certain desired properties such as increased conductivity may be obtained.
• a test piece of sintered silicon nitride (RBSN) with dimensions of about 10 x 9 x 24 mm was placed in a graphite crucible with about 40 g of aluminium metal and was heated to 900°C in a laboratory furnace with a furnace atmosphere consisting of argon. The crucible with its content was kept at 900°C for 7 days. The test piece was then removed from the crucible with aluminium melt, and the mineral composition was analysed qualitatively by x-ray diffraction. The x-ray diffractogrammes for the test piece before and after the exposure respectively, show that a practically complete conversion of silicon nitride to aluminium nitride has taken place.
• the volume weight of the test piece before and after the conversion was 2.32 g/cm 3 and 3.09 g/cm 3 .
• the total porosity of the silicon nitride test piece was about 25%, open porosity was 17%.
• the open porosity of converted material was 1-2%.
• the x-ray diffractogram of exposed material shows that practically all the Si 3 N has been reacted.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Ceramic Engineering (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Structural Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Inorganic Chemistry (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Ceramic Products (AREA)
• Materials Applied To Surfaces To Minimize Adherence Of Mist Or Water (AREA)
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Cited By (5)

Citations (7)

• 1990
  • 1990-02-15 NO NO900726A patent/NO169646C/no unknown
• 1991
  • 1991-02-13 WO PCT/NO1991/000020 patent/WO1991012350A1/en unknown
  • 1991-02-13 AU AU72380/91A patent/AU7238091A/en not_active Abandoned

Patent Citations (7)

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