WO1994010101A1 - Procede pour la fabrication de pieces moulees en carbure de silicium infiltre de silicium et lie par reaction ainsi que matiere a mouler par compression utilisee comme produit intermediaire - Google Patents

Procede pour la fabrication de pieces moulees en carbure de silicium infiltre de silicium et lie par reaction ainsi que matiere a mouler par compression utilisee comme produit intermediaire Download PDF

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Publication number
WO1994010101A1
WO1994010101A1 PCT/EP1993/003027 EP9303027W WO9410101A1 WO 1994010101 A1 WO1994010101 A1 WO 1994010101A1 EP 9303027 W EP9303027 W EP 9303027W WO 9410101 A1 WO9410101 A1 WO 9410101A1
Authority
WO
WIPO (PCT)
Prior art keywords
silicon carbide
silicon
water
amount
organic compound
Prior art date
Application number
PCT/EP1993/003027
Other languages
German (de)
English (en)
Inventor
Albert Kerber
Mehmet Kara
Karl-Ludwig Eckert
Original Assignee
Lonza-Werke G.M.B.H.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lonza-Werke G.M.B.H. filed Critical Lonza-Werke G.M.B.H.
Publication of WO1994010101A1 publication Critical patent/WO1994010101A1/fr

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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
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
    • C04B35/632—Organic additives
    • C04B35/634—Polymers
    • C04B35/63404—Polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C04B35/63416—Polyvinylalcohols [PVA]; Polyvinylacetates
    • 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

Definitions

  • the present invention relates to a process for the production of moldings from reaction-bonded, silicon-infiltrated silicon carbide. It further relates to a finished mass based on silicon carbide as an intermediate in the process according to the invention.
  • Silicon infiltrated silicon carbide is a ceramic composite material that is becoming increasingly important due to its extreme hardness and wear resistance, its resistance to oxidation and corrosion (in the acidic, neutral and weakly basic range) and its good resistance to temperature changes and high temperatures as well as its gas tightness.
  • Applications for silicon infiltrated silicon carbide are, for example, mechanical seals and bearings for pumps, combustion chambers, welding nozzles, flame tubes etc. (see, for example, M. Blecha et al., Conference room 123, 263-268 (1990)).
  • Shaped bodies made of reaction-bound, silicon-infiltrated silicon carbide are usually produced by molding a green body from silicon carbide grain which contains a certain proportion of elemental carbon and has an open porosity. The green body is then infiltrated with liquid silicon, which reacts with the free carbon and forms silicon carbide. Ideally, the finished molded body contains neither pores nor unreacted carbon, and the spaces between the particles are filled with metallic silicon.
  • the shaping in the production of green bodies can in principle be carried out by all methods customary in ceramics, preferably by molding. For this it is necessary to add temporary binders and plasticizers in order to achieve sufficient strength of the green body and sufficient formability.
  • temporary binders and plasticizers in order to achieve sufficient strength of the green body and sufficient formability.
  • organic polymers in the form of thermoplastics or resins or thermosets which harden during the pressing process or subsequently harden
  • resins M. Blecha et al., Loc.
  • the object is achieved by the method according to claim 1 and the molding compound according to claim 11.
  • Such mixtures are known per se, their structure is advantageously optimized depending on the intended use, size and shape of the molded body to be produced. This procedure is known to the person skilled in the art.
  • good results were obtained with mixtures of more than 15% by weight, preferably more than 20% by weight, of very fine grain with an average particle size of 1-10 ⁇ m and a "coarse grain" proportion with average particle sizes in the range 25- 150 ⁇ m achieved.
  • Graphite is preferably used as the carbon source, soot can also be used. It is also within the scope of the invention to use another carbon source with a high carbon content, for example petroleum coke.
  • the carbon source is expediently used in an amount of 4-20% by weight, calculated as carbon and based on the amount of silicon carbide. Particularly good results are achieved with graphite in amounts of 6-8% by weight if the coarse grain fraction of the SiC offset is at an average grain size of approximately 50 ⁇ m.
  • polyvinyl alcohol carboxymethyl cellulose, polyethylene glycols, alginates or dextrins can be used as water-soluble polymers.
  • Polyvinyl alcohol is particularly preferred.
  • the wax used as a pressing aid according to the invention is expediently used as an aqueous emulsion.
  • Such wax emulsions are commercially available, for example from Zschimmer & Schwarz, Lahnstein / Rhein.
  • a hygroscopic organic compound is used as a further pressing aid.
  • a polyol ie a dihydric or polyhydric alcohol, is preferably used for this.
  • Glycols such as, for example, ethylene glycol, diethylene glycol, triethylene glycol or propylene glycol or compounds with three or more alcohol functions such as glycerol or the so-called sugar alcohols such as mannitol, sorbitol etc. are particularly suitable for this purpose.
  • the combination of temporary binder and pressing aids according to the invention is preferably used in a total amount (without the water used as solvent or for the preparation of the emulsion) of less than 10% by weight, based on the amount of silicon carbide. Amounts of less than 5% by weight are particularly preferred.
  • the mixture of silicon carbide grains and binder / pressing aid combination is produced in a manner known per se; it is advantageously concluded with a granulation and drying step.
  • the molding compound or granules obtained in this way is also the subject of the present invention. Under normal conditions, it can be kept practically indefinitely and can be pressed in without further pretreatment.
  • the pressing process is known per se. Pressures in the order of magnitude of 1000 bar (100 MPa) to 2500 bar (250 MPa) are advantageously used.
  • an isostatic post-compression can advantageously be connected to the (uniaxial) compression molding process. This procedure is also known per se.
  • green bodies with densities of 2.45 to 2.57 g / cm- * - * can be obtained in this way. Comparative tests with water-soluble polymer alone gave only green densities up to 2.44 g / cm * - *.
  • the green bodies produced according to the invention can be subjected to silicon infiltration even without special heat treatment because of their low content of coking organic substance.
  • the heat treatment can be carried out in one step, temperatures of from 200 to 400 ° C. being expediently maintained.
  • the temperature is preferably 220 to 300.degree.
  • the heat treatment can take place in air, whereby the air can either freely enter or the air access is controlled by a powder bed. Silicon carbide powder is preferably used as the powder bed. This ensures an even temperature distribution and prevents contamination of the green bodies by foreign material.
  • This heat treatment enables final densities of approx. 3J0 g / cm * - 5 to be achieved in the subsequent silicon infiltration.
  • the infiltration as such is carried out in a manner known per se, as is any post-processing that may be required.
  • a binder performance was set up according to the following recipe and mixed thoroughly.
  • the raw materials were premixed dry in an Eirich mixer according to the following recipe:
  • Silicon carbide F230 (FEPA standard) 1600 g
  • the compacts obtained according to Example 3 were heated to 300 ° C. in air in a powder bed made of silicon carbide (grain size 0.2-0.5 mm). Alternatively, some of the compacts were heated free-standing to 300 ° C or 260 - 280 ° C.
  • the pre-treated compacts were placed in a graphite crucible, the bottom of which had previously been coated with an approx. 10 mm thick layer of SiC (grain size 0.5 - 1 mm) and a 5 - 10 mm thick layer of a mixture of 75% by weight SiC (grain size 0 - 0.2 mm) and 25% by weight of silicon powder.
  • the temperature of 1480 ° C. was maintained for a further 10 hours, then the mixture was cooled to room temperature.
  • the samples infiltrated in this way had the following densities:

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Structural Engineering (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Ceramic Products (AREA)

Abstract

Des pièces moulées en carbure de silicium infiltré de silicium et lié par réaction sont fabriquées en utilisant du graphite ou de la suie comme source de carbone. Comme liant temporaire, on utilise un mélange d'un polymère organique hydrosoluble, d'une émulsion de cire et d'un composé organique hydroscopique. Avant l'infiltration de silicium, les pièces crues obtenues par moulage par compression sont soumises à un traitement thermique contrôlé. Ce procédé permet d'obtenir des densités de pièces crues et des densités de pièces infiltrées élevées. Ces pièces moulées conviennent par exemple comme anneaux de glissement et paliers pour pompes, buses de soudage ou tubes-foyers.
PCT/EP1993/003027 1992-11-02 1993-10-29 Procede pour la fabrication de pieces moulees en carbure de silicium infiltre de silicium et lie par reaction ainsi que matiere a mouler par compression utilisee comme produit intermediaire WO1994010101A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH03400/92-8 1992-11-02
CH340092 1992-11-02

Publications (1)

Publication Number Publication Date
WO1994010101A1 true WO1994010101A1 (fr) 1994-05-11

Family

ID=4255162

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP1993/003027 WO1994010101A1 (fr) 1992-11-02 1993-10-29 Procede pour la fabrication de pieces moulees en carbure de silicium infiltre de silicium et lie par reaction ainsi que matiere a mouler par compression utilisee comme produit intermediaire

Country Status (1)

Country Link
WO (1) WO1994010101A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009021976A1 (de) * 2009-05-19 2010-11-25 Skz - Kfe Ggmbh Kunststoff-Forschung Und -Entwicklung Verfahren zur Herstellung eines Bauteils

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2104103A (en) * 1981-08-21 1983-03-02 Shinetsu Chemical Co Forming shaped silicon carbide bodies

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2104103A (en) * 1981-08-21 1983-03-02 Shinetsu Chemical Co Forming shaped silicon carbide bodies

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102009021976A1 (de) * 2009-05-19 2010-11-25 Skz - Kfe Ggmbh Kunststoff-Forschung Und -Entwicklung Verfahren zur Herstellung eines Bauteils

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