CA1139791A - Sintered silicon carbide-aluminum nitride articles and method of making such articles - Google Patents
Sintered silicon carbide-aluminum nitride articles and method of making such articlesInfo
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- CA1139791A CA1139791A CA000323720A CA323720A CA1139791A CA 1139791 A CA1139791 A CA 1139791A CA 000323720 A CA000323720 A CA 000323720A CA 323720 A CA323720 A CA 323720A CA 1139791 A CA1139791 A CA 1139791A
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- 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
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- 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
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- 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
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Abstract
ABSTRACT
Sintered ceramic products comprised of from about 55 to about 99.5 percent by weight of silicon carbide co-sintered with from about 0.5 to about 45 percent by weight aluminum nitride are described. The sintered products have a bulk density of at least 75 percent of the theoretical density of siliconcarbide. The products are produced by sintering under substantially pressure-less conditions, mixtures of silicon carbide, carbon, or carbon source material,and aluminum nitride. The aluminum nitride componet, in reanges of from about 3.0 to about 45 percent, may be initially mixed with the silicon carbide and carbon or carbon source material. In ranges of from about 0.5 to about 3.0 percent, the aluminum nitride component may be added to the mixture in vapor form during sintering.
Sintered ceramic products comprised of from about 55 to about 99.5 percent by weight of silicon carbide co-sintered with from about 0.5 to about 45 percent by weight aluminum nitride are described. The sintered products have a bulk density of at least 75 percent of the theoretical density of siliconcarbide. The products are produced by sintering under substantially pressure-less conditions, mixtures of silicon carbide, carbon, or carbon source material,and aluminum nitride. The aluminum nitride componet, in reanges of from about 3.0 to about 45 percent, may be initially mixed with the silicon carbide and carbon or carbon source material. In ranges of from about 0.5 to about 3.0 percent, the aluminum nitride component may be added to the mixture in vapor form during sintering.
Description
' .~11 ~39'7 1 ¦SINTERE1) S~1.ICON CARBIDE - ALUMIN~M NITRIDE ARTICLES
2 ¦AND
3METHOI)()I~ MAXING SUCH ARTICLES
~BACKGROUND OF T~IE INVENrION
7Silicon carbide, a crystalline compound of silicon ~nd car~on, has 8long been known for its hardness, its strength, and its e~ce~lent resistanGe to 9 ¦oxidation an.l corrosion. Silicon carbide has a low coefficient of expansion, 0 ¦good heat transfer properties, and maintains lligll strength at elevated tempera-11 ¦tures. In recent years, the art of producing high density silicon carbide ~2 bodies from silicon carbide powders has been developed. Methods include reac-13 ¦tion bonding, chemical vapor deposition, hot pressing, and pressureless sinter~
4 ing ~initially formin~ the article and subsequently sintering). `2xamples of ¦these methods are described in U. S. Patents Nos. 3,~53,566; 3,~52,099;
16 3,954,q83; and 3,960~577. The high density silicon carbide bodies so produced 17 ¦are excellent engineering materials and find utility in fabrication of compo-8 ¦nents for turbines, heat exchange units, pumps, and other equipment or tools that are exposed to severe wear a~d/or operation un(ler high temperature condi-tions.
In order to obtain high density and high strength,silicon carbide 22 ceramic materials, ~arious additives ha~e been utilized. For example, a method 23 of hot pressing silicon carbide to densities in order of 98 percent of theore-24 tical by addition of aluminum and iron as densification aids is disclosed by Z5Alliegro, etal, J. Ceram. Soc., Vol. 39, No. 11, Nov., 1965, pages 386 to 3~9.
6 They foun(l that a dense silicon carbide could be produced from a powder mixture ~1 containing 1 percent by we;ght of aluminum. ~heir product had a modulus of rup-28 ture of 54,000 psi at room temperaturc and 70,000 psi at 1371 C.
2~Alumi1lum nitride, a crystalline compound of aluminum and nitrogen, is widely used as a refractory ma~erial. Aluminum nitride exhibits an e~oellent . ~L3~'7~
1 resistance to molten metals and is an especially useful refrac~ory for molten 2 aluminum. Aluminum nitride has ~ood thermal shock resistance, good stren~th,
3METHOI)()I~ MAXING SUCH ARTICLES
~BACKGROUND OF T~IE INVENrION
7Silicon carbide, a crystalline compound of silicon ~nd car~on, has 8long been known for its hardness, its strength, and its e~ce~lent resistanGe to 9 ¦oxidation an.l corrosion. Silicon carbide has a low coefficient of expansion, 0 ¦good heat transfer properties, and maintains lligll strength at elevated tempera-11 ¦tures. In recent years, the art of producing high density silicon carbide ~2 bodies from silicon carbide powders has been developed. Methods include reac-13 ¦tion bonding, chemical vapor deposition, hot pressing, and pressureless sinter~
4 ing ~initially formin~ the article and subsequently sintering). `2xamples of ¦these methods are described in U. S. Patents Nos. 3,~53,566; 3,~52,099;
16 3,954,q83; and 3,960~577. The high density silicon carbide bodies so produced 17 ¦are excellent engineering materials and find utility in fabrication of compo-8 ¦nents for turbines, heat exchange units, pumps, and other equipment or tools that are exposed to severe wear a~d/or operation un(ler high temperature condi-tions.
In order to obtain high density and high strength,silicon carbide 22 ceramic materials, ~arious additives ha~e been utilized. For example, a method 23 of hot pressing silicon carbide to densities in order of 98 percent of theore-24 tical by addition of aluminum and iron as densification aids is disclosed by Z5Alliegro, etal, J. Ceram. Soc., Vol. 39, No. 11, Nov., 1965, pages 386 to 3~9.
6 They foun(l that a dense silicon carbide could be produced from a powder mixture ~1 containing 1 percent by we;ght of aluminum. ~heir product had a modulus of rup-28 ture of 54,000 psi at room temperaturc and 70,000 psi at 1371 C.
2~Alumi1lum nitride, a crystalline compound of aluminum and nitrogen, is widely used as a refractory ma~erial. Aluminum nitride exhibits an e~oellent . ~L3~'7~
1 resistance to molten metals and is an especially useful refrac~ory for molten 2 aluminum. Aluminum nitride has ~ood thermal shock resistance, good stren~th,
3 and excellent rcsistance to most chemicals.
4 A num~er of proposals have been made to cornbine silicon carbide and aluminum nitride ~o produce an improved high density body which may be fahrica-6 ted into articles which will withstand severe operatin~ conditions, or into 7 refractory materials which offer the stren~th of silicon carbide and the inert-8 ness of aluminum nitride. Such combinations have been proposed to improve the 9 electrical conducti~ity of silicon carbide resistance elements and better the o resistance of silicon carbide to corrosion at elevated temperatures. Examples ll of such mixtures are found in U. S. Patents Nos. 3,259,509, 3,287,478; and 12 3,492,153. However, $he previously proposed products are mixtures of silicon 3 carbide and aluminum nitride which do not sinter to produce a high density, ~4 co-sintered prodllct. One negative characteristic of aluminum nitride is that it is soluble in warm water. This characteristic has lessened the use of aluminum 16 nitride in many applications in wllich it would otherwise be utili~ed to an 17 ~ a~lvantage. The mixtures proposed in the prior art have not substantially reme-8 died the solubility of aluminum nitride in warm water. I~ has now been found that a co sintered silicon carbi~e - aluminllm nitride product~ containing up to about 95 percent by weight aluminum nitride, may be produced which has the posi-21 tive attributes of both silicon carbide and aluminum nitride and which is sub-2 stantially insoluble in warm water.
BRIEF DESCRIPTION OF THE INVENTION
The sinterable mixtures of the present invention comprise silicon 26 carbide, carbon an~ aluminum nitride. The mixtures are particularly adapted to 27 use in pressureless sintering operations to produce hard, dense, sintered 28 ceramic l)ro~ucts. The sintered ceramic product of the present invention com-2~ prises a mixture of co-sintered silico~n carbide and aluminum nitride. The sin-; 30 tcred ceramic prl)duct contains rrom abolt 5r) to al)out 9'3.5 percent by weight I~ !IL3~'7~3 l silicon carbide co-sintered with from about 0.5 to about ~15 percent by weight 2 luminum nitride. Although tl1e final sintered product is comprised substan-3 ially completely oi co-sintered slilicon carbide and aluminum nitride! minor 4 mounts, usually less than about l.0 percent by weight, of excess carbon or intering aids, or residue from sintering aids, may be present without dele-6 terious effect.
7 The theoretical density of silicon carbide is 3.21 gm/cc. The sin-~ tered silicon carbide - aluminum nitride products of the present invention 9 typically have a density g~eater than 75 percent of theoretical and usually greater than 85 percent. Co-sintered ceramic products having densities over 90 ll percent of theroetical may be prQduced by the presen~ invention. The sintered 12 products undergo a shrinka~e of about lO percent dur~' ng the sintering process.
~3 The sintered products may be utili~.ed in the form or shape in which they are 4 sintere~, or they may be mad~ned or processed into more complicated shapes.
The components utilized to produce the sinterèd products of the l~ present invention are silicon carbide, aluminum nitri~le, and combinable carbon, 7 or a combinable carbon source material. Sinterin~ aids, such as boron or a 18 boron source material, may also be present to aid in the sintering step. Gene-19 rally, the components are present in amounts ranging from about 55.0 percent to 2~ about 99.0 percent by weight silicon carbide, from about 0.5 to about 45.0 per-21 cent by weight aluminum nitride, and from about 0.5 to about 6.0 percent by 22 wei~ht carbon. In preparing ceramic materials use~ul as bricks, crucibles, or 23 furnace components, the starting composition preferably contains higher amounts 2~ of aluminl1m nitride, usually in the range of from about 3.0 to about ~5.0 per-cent by weight. In preparing a ceramic material useful for the fabrication of 26 articles such as turbine blades or high temperature tools, the starting composi-2~ tion pre~erably contains higher amounts of silicon carbide, usually in the range 28 of from about 90.0 to about 99.0 percent by weight.
29 The sinterable mixtures of the present invention are particularly 3D adapted to use in pressureless sintering processes. In one mode of the inven-.,11 ~ 3~'7' 1 ¦ tion, the starting components are admixed, the mixture cold pressed to form a 2 ¦ green body, and the green body subsequently sintered to form dense, hard pro-3 ¦ ducts. In another mode, only the silieon carbide and carbon components are 4 admixed, cold pressecl, and sintered in an atmosphere containing aluminum ni-¦ tride~ In either mode, the silicon carbide component and the aluminum nitride6 component are co-sintered to produce a hard, dense product ha~ing the property 7 ¦ of being substantially insoluble in warm water.
8 ¦ The silieon carbide starting material may suitable be selected from alpha or beta phase silicon carbide. Mixtures or alpha and beta phase mate-0 rials may be utilized. The silicon carbide startin~ material of the present 11 invention does not re~uire separation or purification of phases to obtain a 2 sinterable material. ~inor amounts of amorphous silicon carbide may be ineluded ~3 without ~leleterious effect.
1~ The silicon carbide starting material is preferably utilizcd in ¦ finely-divided form. A suitable finely-divided material may be produced by 16 ¦ grinding, ball milling, or jet milling larger particles of silicon carbide and 17 ¦ subsequently classifying or separating a component suited to use in the present 18 ¦ invention. Preferably, the silicon carbide starting material has a maximum 19 particle size of about 5 microns and an average particle size of about 0.10 to about 2.50 mierons. It is diffieult to obtain accurate partiele size distrilbu-tion for silieon earbide powders having a size less than about 1 micron in size,22 and therefore, surfaee area may be considered relevant in determining suitable 23 material. Accordingly, the preferred silicon carbide ~articles for use in the 24 present powders have a surface area of from about 1 to about 100 m2/g. Within ~5 this range, it is more prefo~re~ that the surface area of the particles range 26 botween about 2 an(l about 50 m2/g, and, within that range, a range from about 27 2 to about 20 m~/g has been found em;nently useful.
2a The aluminum nitride oomponent of the present invention may be uti-2~ li%ed in the form of finely-divided powdor, if it is to be initially mixe(l with ¦ tho o~he coml)ononts. ~rel~rab1y, a partic10 siYe Or 1ess ~han 5 micrnns is ~L~L3~ L
I ¦utilized, ancl, more prcferably, a particle size less than about 2 microns is 2 ¦desirable. If it is to be utili%ed to supply a sintcring atmosphere of aluminum 3 nitride, it may be utilized in the form of pressed pellets or bodies placed in 4 the sinterin~ furnace. Alternatively, aluminum nitride may be produced in situ in the sintering furnace; however, this method is generally not preferred be-6 cause of the difficulty in controlling the amount of aluminum nitride in the 7 product an~ the problem of maintaining furnace conditions conducive to both8 sintering and to the production of aluminum nitride. A preferred method of providing an aluminum nitride atmosphere in the sintcring furnace is by merely o positioning compacts or pellets of aluminum nitride of a known weight in the sintering furnace and allowing the aluminum nitride to vaporize ~uring the sin-2 tering operation. Suitably, aluminum nitride may be produced by nitriding a3 mixture of 75 percent by weight aluminuln powder and ~5 percent by weight alumi-4 num fluoride at a temperature of 1000 C in an atmosphere of ~0 percent nitrogen and 20 percent hydrogen. The nitride product is suitably crushed and may sub-16 sequently be pelleted to obtain a useful source of aluminum nitride.
1 The present compositions also contain excess or combinable carbon in 8 amounts from about 0.5 to about h.0 percent by weight. The carbon component1~ facilitates the subsequcnt sintering operation and aids in reducing the amounts of oxides that might otherwise remain in the finished sintered product. In pre-Zl ferred compositions, the combinable carbon is present in amounts between about 22 2.0 and about 5.0 percent by weight of the silicon carbide material. ~he carbon ~3 component may be utilized in any form that facilitates mixing of the carbon com-24 ponent with the silicon carbide component to obtain a dispersion of carbonthrouyhout the mixture. If the carban component is utilized in fine~y-divided 26 form, it su;tably may be in the form of colloidal graphite. However, a parti-27 cularly useful form of carbon is a carbon source material, which suitably may be 28 a carbonizable organic material. Such materials may be easily dispersed 2~ -thrpughout the silicon carbide component, utilized as a binder in an initial cold pressing or forming operation, and subsequently provide the required I!
I ~L39'7~3~
l ¦excess or combinable carbon by decomposition during the sintering operation.
2 ¦ Of particular use are c~rbonizable organic materials such as phenolic resins, 3 ¦ acrylic resins, and polyphenylene resins. Generally, such carboni~able organic 4 materials will provide from about 30 ~o about 50 percent of their ori~inal S ¦weight in combinable carbon.
6 In one mode of carrying out the present invention, the silicon carbide 7 ¦component, the carbon component, and the aluminum nitride component are admixed, ¦preferably by dispersing a c`arbon source material throughout the silicon carbide 9 and aluminum nitride components. The mixture is then cold pressed at a pressure between about 12,000 and about 18,000 psi to form a green body. The green body 11 is subsequently sintered under substantially pressureless sintering conditions 12 ¦to pro~uce a co-sintered product. This mode is particularly adapted to use when 13 the composition contains large, from about 3 to about 45 percent by weight, 14 amounts of aluminum nitride. Such sintered compositions find use in the fabri-cation of crucibles, refractory bricks, or furnace components.
16 In another mo~e of the invention, the sintered product contains a 1~ ~ lesser amount of aluminum nitride, usually from about 0.5 to about 3.0 percent 18 by weight. Such products are suitably produced by initially mixing the silicon 19 carbide and carbon components, cold pressing to form a green body, and sintering the green body in an atmosphere of aluminum nitride. The atmosphere of aluminum 21 nitride may be produced by heating a source of aluminum nitri~e to a temperature 22 above its vapori~ation point during the sintering step, or aluminum nitride may 23 be produced in situ during the sintering step. The products of this mode are 24 particularly adap~ed to use in the fabrication of components for equipment or 25 Laols that are to be used un(ler severe wear, high temperature, or corrosive 26 con~litions.
2~ The startin~J mixtures of the present invention may also contain minor 28 amounts of materials that act as sintering aids, for examplel boron or boron-29 conta;ning compoun-ls. Sintering aids are generally effective in the range of from about 0.3 to about 3.0 percent by weight of the aid, for example, boron, as compared to ~he wcight o the silicon carbide componcnt. A boron-containing ;
-t)-~3~3'7~3.~
l ¦atmosphere may be provided ;n the furnace durin~ sintering to aid in densifica-2 ¦tion. In such mode, boron gas may be utilized in sintering atmosphere or a3 ¦boron source~ for example, H2~03 or ~ 03, may be placed in ~he furnace and 4 allowed to decompose during the sintcring opera~ion. In either mode~ partial p.essure of at least about 10 7 atmospheres of boron is preferably maintained 6 durin~J the sintering operation.
7 The sintered ceramic products of the present invention are o high 8 density and high strength, substantially non-por,ous, and eminently useful in 9 en~ineering applications. If desired, the high-density, high-stren~th silicon o ¦carbide product may subsequently be machined~ by diamond grinding, electro-11 chemical machining, ultrasonic machining, or by electrical discharge machining 12 techniques to provide tools or machine components requiring clase tolerances.
14 DETAII~ED DESCRIPTION OF THE INVEllTION
The sintered ceramic products of the present invention are comprised 16 of from about 55 to about 99.5 percent by weight of silicon carbide co-sintered 17 with from about 0.5 to about 45 percent by weight of aluminum nitride. The pro-ducts are substantially insoluble in warm water. The sintered products have a 1~ bulk density of at least 75 percent of the theoretical density of silicon car-bide. For many applications, a density of at least ~5 percent of theoretical is ~ dcsirable, and densities of over 90 percent are obtainable with the mixtures of z the present invention.
23 The silicon carbide startin~ maeerial is preferably utilized in 24 finely-divided form having a particle size of less than about 5 microns and, more preferably, less than about 2 microns. The silicon carbide starting mate-26 rial has a surface area greater than ~.0 m2/g, and material having a surface 27 area ~reater than about 20 m2/g is eminently useful.
2~ The carbon component, present in amounts of from about 0.5 to about 2~ 6.0 percent by wei~ht, may be utilized in a fine1y-divided form with a particle size less than abou~ 5 microns and, preferably, less than about 2.0 microns.
` `I ~L~IL3~7g.~
1 llowcver, ;~ is preferre(l to utilize a carbon source material such as a carboni-2 zable organic material which scrves the dual purpose of acting as a binder 3 during the cold pressiny operation and subsequently as a source of carbon when 4 it carboniæes during the sinteriny operation. Particularly useful in this mode are organic resins which provide resi~ual carbon in amounts of from about 30 to6 about 50 percent by weight after carbonizing.
7 The silicon carbide starting material and the carbo~lor carbon source màterial are thoroughly mixed eO obtain a dispersion of the carbon or carbon 9 source matcrial throughout the silicon carbide material.
0 In one mode of the present invention, particularly where the amount of ~t aluminum nitride desired in the sintered product is between about ~,O!a~d;~b~ut 95.0 percent by weight, based on the total weight of the mixture, the aluminum 13 nitrid~ componen~ in finely-divided form is admixed with the silicon carbicle and 1 14 carbon or carbon source material componen~s. A particle siæe of less than lO
m;crons in preferrecl. Eminently useful is a particle size of less than 5 16 microns, and, for ease of even distribution, a particle size of less than about 17 2 microns is particularly useful.
8 In another mode of -the invention, particularly when the amount of aluminum nitride desired in the sintered product is bctwecn about 0.5 and about 0 3.0 percent by weight of the mixture, the aluminum nitride component may be 21 added to the silicon carbide - carbon mixture in the vapor state duriny sinter-22 ing. In this mode, the silicon carbide and carbon or carbon source components 23 are admixed, shapcd by cold pressing, and subsequently sintered in an atmosphere 24 containing betwecn about 5-10 and about l-lO 3 atmospheres of aluminum nitride .
The aluminum nitride atmosphere may suitably be provided by the inclusion of 26 solid aluminum niLride in the furnace which vaporizes duriny the sintering 27 process Alternatively, aluminum ni~ride may be produced in situ in the furnace 28 during sintering.
29 The cold pressing step is suitably carried out in a metal die at pressllres between ahout 12,000 and about l~,000 psi. Generally, pressures abov ~L~3~3'~
I ahnut 1',500 psi are useful. Pressures above about 1~,000 psi may be utiliæed;
2 however, minimal h~neficial results in the final sintered product are obtained.
3 A second pressing of the present mixture results in an improvement in 4 the density of the final product. In such process, the mixture is initially cold pressed, crushed to about a ~0 mesh si%e powder, and re-pressed. It is 6 postulated that this process is effective in removing air from the powder par-7 ticles which yields a higher green body density and, in turn, a higher sintered 8 product density. However, double pressing is not critical to the present 9 invention, and the improvement is not substantial enough to warrant two o pressings as a procedure to be employed ln all cases.
11 The pressed product, green body, typically has a density ranging 2 between about 1.79 and about 1.95 g/cc. The porosity of the green bodies pro-3 duced by mixtures of the present invention typically range from about 39.3 to 4 about ~5.8 percent.
The sintering step is suitably carried out utilizing a graphite resis-6 tance element furnace. Temperatures between about 1900 and about 2250 C. are 11 eminently useful. Usually, when temperatures less than about 1~00 C. are 18 employed, the sintering process does not proceed to produce a desired den6e1~ product, Usually, when temperatures over about 225n C. are employed, deterio-zo ration of the sintered product may occur.
2~ The sintering step is preferably carried out in an atmosphere that is 2~ inert to the mixtures being sintered. Inert gases such as argon, helium, and 23 nitrogen may be employed. An atmosphere of ammonia may be utilized. A vacuum 24 in the order of about 10-3 torr may also be utilized.
Generally, the mixtures of the present invention sinter under the 26 foregoirlg conditions to prodllce the desired co-sintered product when sintering 21 times between about ~ to about 6 hours are employed. ~sually, sintering times 28 between about ~ to about 2 hours are sufficient.
29 ~he present invention may be more fully illustrated by the following ~o ¦ exal s which mre not ~o be intorpreted as limiting. ~nless othe~wise indi~ ¦
39'791 1 ¦ cated, all parts and percenta~es are by weigh~, and all temperatures are in 2 degrees Celsius.
S A mixture containing 95 parts of alpha phase silicon carbide havin~
6 an average particle size of less than 5 microns, 1 part of aluminum nitride also 7 ¦having an average particle si~e of less than 5 microns, and 4 parts of carbon 8 ¦using a phenolic resin, a product designated as B178 Resin by Varcum Chemical 9 ¦Division, Reichhold Che~icals, Inc., was made by ball milling the components in o ¦an acetone slurry for a period of 8 hours. The mixture was then dried at room Il ¦tempe~ature o~er a period of about twelve hours. The dry mixture was then 12 ¦crushed by dry ball milling and screened through a 80 mesh screen~
13 The screened powder was then cold pressed at lS,000 psi using a metal 14 die to produce a green body ~" in diameter and Y2" in height. The green body ¦had a density of 1.8fl g/cc. The body was then allowed to dry at room ~empera-6 ~ture and subsequently was heated at 110 C. in air for a period of 1 hour to 17 ¦cure the phenolic resin composition.
18 ¦ The green body was then sintered in a graphite resistance element 1~ furnace at a temperature of 2150 C. for a period of 3D minutes in an argon atmosphere, The co-si'ntered product was found to have undergane a linear 2l shrinkage of 10.93%. The product had a porosity of 2.91% and a bulk density of 22 3.00 ~/cc, which corresponds to 93.30% of the theoretical density of silicon 23 carbide.
24 This example is shown in the following table as Example 1. Examples 26 2 throu~h 10 were conductcd in a similar manner.
Il ~3~'7~3~
I
I c~ O~ r o o o 1 '~ ~ o o~ ~ ~ CD n n In 4 ~ 'i `
I 1~ ~ O ~ C~
o In 3 7 a~ ~7 ~ ~ ~ c~
B
t~ c~
I o c~
Il I a~
I ~ :: c~
12 I ~ a~ c~ ~ In~ a~ o~ ~ ~l a~ cr I ~ O
13 ¦ s ~ o ~ o o ~ o a:
~4 ~6 I ~ Q ~ -I .-1 ~ ,_, 11 ¦ .q 18 I L) C ~
I .,, l" ~ J O ~ ~ ~ ~ "~ s ,:: s~
I ~ Q OOOOOOOOOO
C . ~ ~
22 c) ~ ~
2~ z o o O o o o o o O o ~ ta C~ r ,, ~ * *
q~ * *
26 e ~ ~ ~ ~ n ~ -- a: 3 ~ .
3.1L
l ¦ EXAMPLE ll 2 ¦ A mixture of 96.0 parts alpha phase silicon carbide having an average ¦particle si~.e less than ') microns and 4.0 parts of carbon using a B-~7~1 phenolic 4 ¦resin composition was made by ball milling the silicon carbide and resin compo-¦nents in a slurry of acetone for a period of eight llours~ Thc ~ixture was dried 6 at room temperature and processed as ;n Æxample l to produce a green body. The 7 green body was placed in the sintering furnace along with a pellet of aluminum 8 nitride. A sintering temperature of 1950 C. was maintained for a period of 30 9 minutes with an argon atmosphere~ The partial pressure of aluminum nitride was o calculated to be about ~5-lO-~ atmospheres. The sintercd product was found to have a porosity of 4.25% and a bulk density of 2.62:g/cc, corresponding to 2 ~l.62% of the theoretical density of silicon carbide.
3 Example ll is shown in Table II as Example ll. Examples 12 through ~ 16 we conducted in a similar mann-r.
, 1 ~ i ~9 ll l 3~ '7i'~
I
4 I ~ n 6 ¦ a ~ o o~ n o ~r ~ `D
7 _ ~`; N C~
~ ~ .~ ~~ In 10 1 3~
11 o ~
12 ~ ~ ~ ~r a) m 13 1 ~ ~ o o~
14 ¦ H
16 l h ~ ~ 3 0~
17 1 ~3 .~
18 ~ C O O O O s~
1~ U~ C1` C~ 0` ` ,~
0 1 ~ 1 3 21 o ~ ¦
22 ~ c~
~: Zl " * **
2~ ~ o ~ * *
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~7 I
.11 ~ ~3~
1 It w;ll be appreciated ~hat the present invention is not to be consi-2 ¦dered as limited to the specific examples and embodiments given in the foregoing 3 ~and that various modifications may be ma~e within the ordinary skill of the art 6 withou-t departing from the spirit and scope of the invention.
9 . .
2 .
~3 1 1~ .
8 .
26 l 28 .
. -l~1-
BRIEF DESCRIPTION OF THE INVENTION
The sinterable mixtures of the present invention comprise silicon 26 carbide, carbon an~ aluminum nitride. The mixtures are particularly adapted to 27 use in pressureless sintering operations to produce hard, dense, sintered 28 ceramic l)ro~ucts. The sintered ceramic product of the present invention com-2~ prises a mixture of co-sintered silico~n carbide and aluminum nitride. The sin-; 30 tcred ceramic prl)duct contains rrom abolt 5r) to al)out 9'3.5 percent by weight I~ !IL3~'7~3 l silicon carbide co-sintered with from about 0.5 to about ~15 percent by weight 2 luminum nitride. Although tl1e final sintered product is comprised substan-3 ially completely oi co-sintered slilicon carbide and aluminum nitride! minor 4 mounts, usually less than about l.0 percent by weight, of excess carbon or intering aids, or residue from sintering aids, may be present without dele-6 terious effect.
7 The theoretical density of silicon carbide is 3.21 gm/cc. The sin-~ tered silicon carbide - aluminum nitride products of the present invention 9 typically have a density g~eater than 75 percent of theoretical and usually greater than 85 percent. Co-sintered ceramic products having densities over 90 ll percent of theroetical may be prQduced by the presen~ invention. The sintered 12 products undergo a shrinka~e of about lO percent dur~' ng the sintering process.
~3 The sintered products may be utili~.ed in the form or shape in which they are 4 sintere~, or they may be mad~ned or processed into more complicated shapes.
The components utilized to produce the sinterèd products of the l~ present invention are silicon carbide, aluminum nitri~le, and combinable carbon, 7 or a combinable carbon source material. Sinterin~ aids, such as boron or a 18 boron source material, may also be present to aid in the sintering step. Gene-19 rally, the components are present in amounts ranging from about 55.0 percent to 2~ about 99.0 percent by weight silicon carbide, from about 0.5 to about 45.0 per-21 cent by weight aluminum nitride, and from about 0.5 to about 6.0 percent by 22 wei~ht carbon. In preparing ceramic materials use~ul as bricks, crucibles, or 23 furnace components, the starting composition preferably contains higher amounts 2~ of aluminl1m nitride, usually in the range of from about 3.0 to about ~5.0 per-cent by weight. In preparing a ceramic material useful for the fabrication of 26 articles such as turbine blades or high temperature tools, the starting composi-2~ tion pre~erably contains higher amounts of silicon carbide, usually in the range 28 of from about 90.0 to about 99.0 percent by weight.
29 The sinterable mixtures of the present invention are particularly 3D adapted to use in pressureless sintering processes. In one mode of the inven-.,11 ~ 3~'7' 1 ¦ tion, the starting components are admixed, the mixture cold pressed to form a 2 ¦ green body, and the green body subsequently sintered to form dense, hard pro-3 ¦ ducts. In another mode, only the silieon carbide and carbon components are 4 admixed, cold pressecl, and sintered in an atmosphere containing aluminum ni-¦ tride~ In either mode, the silicon carbide component and the aluminum nitride6 component are co-sintered to produce a hard, dense product ha~ing the property 7 ¦ of being substantially insoluble in warm water.
8 ¦ The silieon carbide starting material may suitable be selected from alpha or beta phase silicon carbide. Mixtures or alpha and beta phase mate-0 rials may be utilized. The silicon carbide startin~ material of the present 11 invention does not re~uire separation or purification of phases to obtain a 2 sinterable material. ~inor amounts of amorphous silicon carbide may be ineluded ~3 without ~leleterious effect.
1~ The silicon carbide starting material is preferably utilizcd in ¦ finely-divided form. A suitable finely-divided material may be produced by 16 ¦ grinding, ball milling, or jet milling larger particles of silicon carbide and 17 ¦ subsequently classifying or separating a component suited to use in the present 18 ¦ invention. Preferably, the silicon carbide starting material has a maximum 19 particle size of about 5 microns and an average particle size of about 0.10 to about 2.50 mierons. It is diffieult to obtain accurate partiele size distrilbu-tion for silieon earbide powders having a size less than about 1 micron in size,22 and therefore, surfaee area may be considered relevant in determining suitable 23 material. Accordingly, the preferred silicon carbide ~articles for use in the 24 present powders have a surface area of from about 1 to about 100 m2/g. Within ~5 this range, it is more prefo~re~ that the surface area of the particles range 26 botween about 2 an(l about 50 m2/g, and, within that range, a range from about 27 2 to about 20 m~/g has been found em;nently useful.
2a The aluminum nitride oomponent of the present invention may be uti-2~ li%ed in the form of finely-divided powdor, if it is to be initially mixe(l with ¦ tho o~he coml)ononts. ~rel~rab1y, a partic10 siYe Or 1ess ~han 5 micrnns is ~L~L3~ L
I ¦utilized, ancl, more prcferably, a particle size less than about 2 microns is 2 ¦desirable. If it is to be utili%ed to supply a sintcring atmosphere of aluminum 3 nitride, it may be utilized in the form of pressed pellets or bodies placed in 4 the sinterin~ furnace. Alternatively, aluminum nitride may be produced in situ in the sintering furnace; however, this method is generally not preferred be-6 cause of the difficulty in controlling the amount of aluminum nitride in the 7 product an~ the problem of maintaining furnace conditions conducive to both8 sintering and to the production of aluminum nitride. A preferred method of providing an aluminum nitride atmosphere in the sintcring furnace is by merely o positioning compacts or pellets of aluminum nitride of a known weight in the sintering furnace and allowing the aluminum nitride to vaporize ~uring the sin-2 tering operation. Suitably, aluminum nitride may be produced by nitriding a3 mixture of 75 percent by weight aluminuln powder and ~5 percent by weight alumi-4 num fluoride at a temperature of 1000 C in an atmosphere of ~0 percent nitrogen and 20 percent hydrogen. The nitride product is suitably crushed and may sub-16 sequently be pelleted to obtain a useful source of aluminum nitride.
1 The present compositions also contain excess or combinable carbon in 8 amounts from about 0.5 to about h.0 percent by weight. The carbon component1~ facilitates the subsequcnt sintering operation and aids in reducing the amounts of oxides that might otherwise remain in the finished sintered product. In pre-Zl ferred compositions, the combinable carbon is present in amounts between about 22 2.0 and about 5.0 percent by weight of the silicon carbide material. ~he carbon ~3 component may be utilized in any form that facilitates mixing of the carbon com-24 ponent with the silicon carbide component to obtain a dispersion of carbonthrouyhout the mixture. If the carban component is utilized in fine~y-divided 26 form, it su;tably may be in the form of colloidal graphite. However, a parti-27 cularly useful form of carbon is a carbon source material, which suitably may be 28 a carbonizable organic material. Such materials may be easily dispersed 2~ -thrpughout the silicon carbide component, utilized as a binder in an initial cold pressing or forming operation, and subsequently provide the required I!
I ~L39'7~3~
l ¦excess or combinable carbon by decomposition during the sintering operation.
2 ¦ Of particular use are c~rbonizable organic materials such as phenolic resins, 3 ¦ acrylic resins, and polyphenylene resins. Generally, such carboni~able organic 4 materials will provide from about 30 ~o about 50 percent of their ori~inal S ¦weight in combinable carbon.
6 In one mode of carrying out the present invention, the silicon carbide 7 ¦component, the carbon component, and the aluminum nitride component are admixed, ¦preferably by dispersing a c`arbon source material throughout the silicon carbide 9 and aluminum nitride components. The mixture is then cold pressed at a pressure between about 12,000 and about 18,000 psi to form a green body. The green body 11 is subsequently sintered under substantially pressureless sintering conditions 12 ¦to pro~uce a co-sintered product. This mode is particularly adapted to use when 13 the composition contains large, from about 3 to about 45 percent by weight, 14 amounts of aluminum nitride. Such sintered compositions find use in the fabri-cation of crucibles, refractory bricks, or furnace components.
16 In another mo~e of the invention, the sintered product contains a 1~ ~ lesser amount of aluminum nitride, usually from about 0.5 to about 3.0 percent 18 by weight. Such products are suitably produced by initially mixing the silicon 19 carbide and carbon components, cold pressing to form a green body, and sintering the green body in an atmosphere of aluminum nitride. The atmosphere of aluminum 21 nitride may be produced by heating a source of aluminum nitri~e to a temperature 22 above its vapori~ation point during the sintering step, or aluminum nitride may 23 be produced in situ during the sintering step. The products of this mode are 24 particularly adap~ed to use in the fabrication of components for equipment or 25 Laols that are to be used un(ler severe wear, high temperature, or corrosive 26 con~litions.
2~ The startin~J mixtures of the present invention may also contain minor 28 amounts of materials that act as sintering aids, for examplel boron or boron-29 conta;ning compoun-ls. Sintering aids are generally effective in the range of from about 0.3 to about 3.0 percent by weight of the aid, for example, boron, as compared to ~he wcight o the silicon carbide componcnt. A boron-containing ;
-t)-~3~3'7~3.~
l ¦atmosphere may be provided ;n the furnace durin~ sintering to aid in densifica-2 ¦tion. In such mode, boron gas may be utilized in sintering atmosphere or a3 ¦boron source~ for example, H2~03 or ~ 03, may be placed in ~he furnace and 4 allowed to decompose during the sintcring opera~ion. In either mode~ partial p.essure of at least about 10 7 atmospheres of boron is preferably maintained 6 durin~J the sintering operation.
7 The sintered ceramic products of the present invention are o high 8 density and high strength, substantially non-por,ous, and eminently useful in 9 en~ineering applications. If desired, the high-density, high-stren~th silicon o ¦carbide product may subsequently be machined~ by diamond grinding, electro-11 chemical machining, ultrasonic machining, or by electrical discharge machining 12 techniques to provide tools or machine components requiring clase tolerances.
14 DETAII~ED DESCRIPTION OF THE INVEllTION
The sintered ceramic products of the present invention are comprised 16 of from about 55 to about 99.5 percent by weight of silicon carbide co-sintered 17 with from about 0.5 to about 45 percent by weight of aluminum nitride. The pro-ducts are substantially insoluble in warm water. The sintered products have a 1~ bulk density of at least 75 percent of the theoretical density of silicon car-bide. For many applications, a density of at least ~5 percent of theoretical is ~ dcsirable, and densities of over 90 percent are obtainable with the mixtures of z the present invention.
23 The silicon carbide startin~ maeerial is preferably utilized in 24 finely-divided form having a particle size of less than about 5 microns and, more preferably, less than about 2 microns. The silicon carbide starting mate-26 rial has a surface area greater than ~.0 m2/g, and material having a surface 27 area ~reater than about 20 m2/g is eminently useful.
2~ The carbon component, present in amounts of from about 0.5 to about 2~ 6.0 percent by wei~ht, may be utilized in a fine1y-divided form with a particle size less than abou~ 5 microns and, preferably, less than about 2.0 microns.
` `I ~L~IL3~7g.~
1 llowcver, ;~ is preferre(l to utilize a carbon source material such as a carboni-2 zable organic material which scrves the dual purpose of acting as a binder 3 during the cold pressiny operation and subsequently as a source of carbon when 4 it carboniæes during the sinteriny operation. Particularly useful in this mode are organic resins which provide resi~ual carbon in amounts of from about 30 to6 about 50 percent by weight after carbonizing.
7 The silicon carbide starting material and the carbo~lor carbon source màterial are thoroughly mixed eO obtain a dispersion of the carbon or carbon 9 source matcrial throughout the silicon carbide material.
0 In one mode of the present invention, particularly where the amount of ~t aluminum nitride desired in the sintered product is between about ~,O!a~d;~b~ut 95.0 percent by weight, based on the total weight of the mixture, the aluminum 13 nitrid~ componen~ in finely-divided form is admixed with the silicon carbicle and 1 14 carbon or carbon source material componen~s. A particle siæe of less than lO
m;crons in preferrecl. Eminently useful is a particle size of less than 5 16 microns, and, for ease of even distribution, a particle size of less than about 17 2 microns is particularly useful.
8 In another mode of -the invention, particularly when the amount of aluminum nitride desired in the sintered product is bctwecn about 0.5 and about 0 3.0 percent by weight of the mixture, the aluminum nitride component may be 21 added to the silicon carbide - carbon mixture in the vapor state duriny sinter-22 ing. In this mode, the silicon carbide and carbon or carbon source components 23 are admixed, shapcd by cold pressing, and subsequently sintered in an atmosphere 24 containing betwecn about 5-10 and about l-lO 3 atmospheres of aluminum nitride .
The aluminum nitride atmosphere may suitably be provided by the inclusion of 26 solid aluminum niLride in the furnace which vaporizes duriny the sintering 27 process Alternatively, aluminum ni~ride may be produced in situ in the furnace 28 during sintering.
29 The cold pressing step is suitably carried out in a metal die at pressllres between ahout 12,000 and about l~,000 psi. Generally, pressures abov ~L~3~3'~
I ahnut 1',500 psi are useful. Pressures above about 1~,000 psi may be utiliæed;
2 however, minimal h~neficial results in the final sintered product are obtained.
3 A second pressing of the present mixture results in an improvement in 4 the density of the final product. In such process, the mixture is initially cold pressed, crushed to about a ~0 mesh si%e powder, and re-pressed. It is 6 postulated that this process is effective in removing air from the powder par-7 ticles which yields a higher green body density and, in turn, a higher sintered 8 product density. However, double pressing is not critical to the present 9 invention, and the improvement is not substantial enough to warrant two o pressings as a procedure to be employed ln all cases.
11 The pressed product, green body, typically has a density ranging 2 between about 1.79 and about 1.95 g/cc. The porosity of the green bodies pro-3 duced by mixtures of the present invention typically range from about 39.3 to 4 about ~5.8 percent.
The sintering step is suitably carried out utilizing a graphite resis-6 tance element furnace. Temperatures between about 1900 and about 2250 C. are 11 eminently useful. Usually, when temperatures less than about 1~00 C. are 18 employed, the sintering process does not proceed to produce a desired den6e1~ product, Usually, when temperatures over about 225n C. are employed, deterio-zo ration of the sintered product may occur.
2~ The sintering step is preferably carried out in an atmosphere that is 2~ inert to the mixtures being sintered. Inert gases such as argon, helium, and 23 nitrogen may be employed. An atmosphere of ammonia may be utilized. A vacuum 24 in the order of about 10-3 torr may also be utilized.
Generally, the mixtures of the present invention sinter under the 26 foregoirlg conditions to prodllce the desired co-sintered product when sintering 21 times between about ~ to about 6 hours are employed. ~sually, sintering times 28 between about ~ to about 2 hours are sufficient.
29 ~he present invention may be more fully illustrated by the following ~o ¦ exal s which mre not ~o be intorpreted as limiting. ~nless othe~wise indi~ ¦
39'791 1 ¦ cated, all parts and percenta~es are by weigh~, and all temperatures are in 2 degrees Celsius.
S A mixture containing 95 parts of alpha phase silicon carbide havin~
6 an average particle size of less than 5 microns, 1 part of aluminum nitride also 7 ¦having an average particle si~e of less than 5 microns, and 4 parts of carbon 8 ¦using a phenolic resin, a product designated as B178 Resin by Varcum Chemical 9 ¦Division, Reichhold Che~icals, Inc., was made by ball milling the components in o ¦an acetone slurry for a period of 8 hours. The mixture was then dried at room Il ¦tempe~ature o~er a period of about twelve hours. The dry mixture was then 12 ¦crushed by dry ball milling and screened through a 80 mesh screen~
13 The screened powder was then cold pressed at lS,000 psi using a metal 14 die to produce a green body ~" in diameter and Y2" in height. The green body ¦had a density of 1.8fl g/cc. The body was then allowed to dry at room ~empera-6 ~ture and subsequently was heated at 110 C. in air for a period of 1 hour to 17 ¦cure the phenolic resin composition.
18 ¦ The green body was then sintered in a graphite resistance element 1~ furnace at a temperature of 2150 C. for a period of 3D minutes in an argon atmosphere, The co-si'ntered product was found to have undergane a linear 2l shrinkage of 10.93%. The product had a porosity of 2.91% and a bulk density of 22 3.00 ~/cc, which corresponds to 93.30% of the theoretical density of silicon 23 carbide.
24 This example is shown in the following table as Example 1. Examples 26 2 throu~h 10 were conductcd in a similar manner.
Il ~3~'7~3~
I
I c~ O~ r o o o 1 '~ ~ o o~ ~ ~ CD n n In 4 ~ 'i `
I 1~ ~ O ~ C~
o In 3 7 a~ ~7 ~ ~ ~ c~
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t~ c~
I o c~
Il I a~
I ~ :: c~
12 I ~ a~ c~ ~ In~ a~ o~ ~ ~l a~ cr I ~ O
13 ¦ s ~ o ~ o o ~ o a:
~4 ~6 I ~ Q ~ -I .-1 ~ ,_, 11 ¦ .q 18 I L) C ~
I .,, l" ~ J O ~ ~ ~ ~ "~ s ,:: s~
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22 c) ~ ~
2~ z o o O o o o o o O o ~ ta C~ r ,, ~ * *
q~ * *
26 e ~ ~ ~ ~ n ~ -- a: 3 ~ .
3.1L
l ¦ EXAMPLE ll 2 ¦ A mixture of 96.0 parts alpha phase silicon carbide having an average ¦particle si~.e less than ') microns and 4.0 parts of carbon using a B-~7~1 phenolic 4 ¦resin composition was made by ball milling the silicon carbide and resin compo-¦nents in a slurry of acetone for a period of eight llours~ Thc ~ixture was dried 6 at room temperature and processed as ;n Æxample l to produce a green body. The 7 green body was placed in the sintering furnace along with a pellet of aluminum 8 nitride. A sintering temperature of 1950 C. was maintained for a period of 30 9 minutes with an argon atmosphere~ The partial pressure of aluminum nitride was o calculated to be about ~5-lO-~ atmospheres. The sintercd product was found to have a porosity of 4.25% and a bulk density of 2.62:g/cc, corresponding to 2 ~l.62% of the theoretical density of silicon carbide.
3 Example ll is shown in Table II as Example ll. Examples 12 through ~ 16 we conducted in a similar mann-r.
, 1 ~ i ~9 ll l 3~ '7i'~
I
4 I ~ n 6 ¦ a ~ o o~ n o ~r ~ `D
7 _ ~`; N C~
~ ~ .~ ~~ In 10 1 3~
11 o ~
12 ~ ~ ~ ~r a) m 13 1 ~ ~ o o~
14 ¦ H
16 l h ~ ~ 3 0~
17 1 ~3 .~
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0 1 ~ 1 3 21 o ~ ¦
22 ~ c~
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~7 I
.11 ~ ~3~
1 It w;ll be appreciated ~hat the present invention is not to be consi-2 ¦dered as limited to the specific examples and embodiments given in the foregoing 3 ~and that various modifications may be ma~e within the ordinary skill of the art 6 withou-t departing from the spirit and scope of the invention.
9 . .
2 .
~3 1 1~ .
8 .
26 l 28 .
. -l~1-
Claims (14)
1. A method of producing a co-sintered silicon carbide-aluminum nitride product which comprises the steps of:
(a) forming a mixture of from about 55.0 to about 99.0 percent by weight finely-divided silicon carbide, from about 0.5 to about 45.0 percent by weight aluminum nitride, and from about 0.5 to about 6.0 percent by weight carbon, or a carbon source material, (b) shaping said mixture into a green body by cold pressing, (c) sintering said green body under substantially pressureless conditions in an inert atmosphere at a tempera-ture between about 1900° and about 2250°C, and (d) recovering a co-sintered silicon carbide-aluminum nitride product having a density of at least 75 percent of the theoretical density of silicon carbide.
(a) forming a mixture of from about 55.0 to about 99.0 percent by weight finely-divided silicon carbide, from about 0.5 to about 45.0 percent by weight aluminum nitride, and from about 0.5 to about 6.0 percent by weight carbon, or a carbon source material, (b) shaping said mixture into a green body by cold pressing, (c) sintering said green body under substantially pressureless conditions in an inert atmosphere at a tempera-ture between about 1900° and about 2250°C, and (d) recovering a co-sintered silicon carbide-aluminum nitride product having a density of at least 75 percent of the theoretical density of silicon carbide.
2. The method of claim 1 wherein the particle size of the silicon carbide, aluminum nitride, and carbon com-ponents is less than 5 microns.
3. The method of claim 1 wherein the carbon component is in the form of a carbonizable organic material.
4. The method of claim 3 wherein the carbonizable organic material is a phenolic resin.
5. The method of claim 1 wherein the cold pressing step is carried out at pressures between about 12,000 and about 18,000 psi.
6. The method of claim 1 which includes a sintering aid of boron or a boron source material added to the initial mixture in an amount of from about 0.3 to about 3.0 percent by weight of the silicon carbide component.
7. The method of claim 1 wherein the atmosphere during sintering contains at least about 10 7 atmospheres boron.
8. A method of producing a co-sintered silicon carbide-aluminum nitride product which comprises the steps of:
(a) forming a mixture of from about 55.0 to about 99.0 percent by weight finely-divided silicon carbide, from about 0.5 to about 45.0 percent by weight aluminum nitride, and from about 0.5 to about 6.0 percent by weight carbon, or a carbon source material, (b) shaping said mixture into a green body by cold pressing, (c) sintering said green body under substantially pressureless conditions in an inert atmosphere containing from about 5 x 10 5 to about 1 x 10 3 atmospheres of aluminum nitride at a temperature between about 1900° and about 2250°C, and (d) recovering a co-sintered silicon carbide-aluminum nitride product having a density of at least 75 percent of the theoretical density of silicon carbide.
(a) forming a mixture of from about 55.0 to about 99.0 percent by weight finely-divided silicon carbide, from about 0.5 to about 45.0 percent by weight aluminum nitride, and from about 0.5 to about 6.0 percent by weight carbon, or a carbon source material, (b) shaping said mixture into a green body by cold pressing, (c) sintering said green body under substantially pressureless conditions in an inert atmosphere containing from about 5 x 10 5 to about 1 x 10 3 atmospheres of aluminum nitride at a temperature between about 1900° and about 2250°C, and (d) recovering a co-sintered silicon carbide-aluminum nitride product having a density of at least 75 percent of the theoretical density of silicon carbide.
9. The method of claim 8 wherein the particle size of the silicon carbide, aluminum nitride, and carbon com-ponents is less than 5 microns.
10. The method of claim 8 wherein the carbon component is in the form of a carbonizable organic material.
11. The method of claim 10 wherein the carbonizable organic material is a phenolic resin.
12. The method of claim 8 wherein the cold pressing step is carried out at pressures between about 12,000 and about 18,000 psi.
13. The method of claim 3 which includes a sintering aid of boron or a boron source material added to the initial mixture in an amount of from about 0.3 to about 3.0 percent by weight of the silicon carbide component.
14. The method of claim 8 wherein the atmosphere during sintering contains at least about 10 atmospheres of boron.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US91564478A | 1978-06-15 | 1978-06-15 | |
| US915,644 | 1978-06-15 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1139791A true CA1139791A (en) | 1983-01-18 |
Family
ID=25436053
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000323720A Expired CA1139791A (en) | 1978-06-15 | 1979-03-19 | Sintered silicon carbide-aluminum nitride articles and method of making such articles |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS62275063A (en) |
| CA (1) | CA1139791A (en) |
| DE (1) | DE2923729A1 (en) |
| FR (1) | FR2432004B1 (en) |
| GB (1) | GB2023185B (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2082165B (en) * | 1980-07-17 | 1984-03-28 | Asahi Glass Co Ltd | Silicon carbide ceramic |
| FR2500438A1 (en) * | 1981-02-24 | 1982-08-27 | Ceraver | METHOD FOR MANUFACTURING DENSE SILICON CARBIDE PARTS |
| US4382837A (en) * | 1981-06-30 | 1983-05-10 | International Business Machines Corporation | Epitaxial crystal fabrication of SiC:AlN |
| JPS5855377A (en) * | 1981-09-28 | 1983-04-01 | 株式会社東芝 | Manufacture of aluminum nitride sintered body |
| US4539298A (en) * | 1981-11-25 | 1985-09-03 | Tokyo Shibaura Denki Kabushiki Kaisha | Highly heat-conductive ceramic material |
| JPS59107975A (en) * | 1982-12-08 | 1984-06-22 | 旭硝子株式会社 | Silicon carbide sintered body |
| GB2170511B (en) * | 1984-12-17 | 1989-06-07 | Toshiba Ceramics Co | Sintered body of silicon carbide |
| GB2177421B (en) * | 1985-05-20 | 1989-07-19 | Toshiba Ceramics Co | Sintered body of silicon carbide and method for manufacturing the same |
| DE4000298A1 (en) * | 1989-01-09 | 1996-05-02 | Fmc Corp | Ceramic composite prodn. for use as cutting tools, nozzles etc. |
| US8097548B2 (en) | 2006-05-22 | 2012-01-17 | Zhang Shi C | High-density pressurelessly sintered zirconium diboride/silicon carbide composite bodies and a method for producing the same |
| US20070270302A1 (en) | 2006-05-22 | 2007-11-22 | Zhang Shi C | Pressurelessly sintered zirconium diboride/silicon carbide composite bodies and a method for producing the same |
| CN101541461B (en) | 2007-07-24 | 2012-07-18 | 布林克曼泵业K.H.布林克曼两合公司 | Method for producing a machine housing with a surface-hardened fluid chamber |
| WO2023286038A1 (en) * | 2021-07-16 | 2023-01-19 | John Crane Inc. | Rotating seal ring material |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US235193A (en) * | 1880-12-07 | Adolph baeyee | ||
| US3259509A (en) * | 1962-01-26 | 1966-07-05 | Allis Chalmers Mfg Co | Refractory materials and method of making same |
| FR1328788A (en) * | 1962-07-13 | 1963-05-31 | Norton Co | Refractory product containing metal carbide and aluminum nitride and process for its manufacture |
| US3492153A (en) * | 1964-09-03 | 1970-01-27 | North American Rockwell | Silicon carbide-aluminum nitride refractory composite |
| US3287478A (en) * | 1964-10-30 | 1966-11-22 | Allis Chalmers Mfg Co | Method of sintering aluminum nitride refractories |
| US3649310A (en) * | 1968-10-25 | 1972-03-14 | Paul C Yates | DENSE, SUBMICRON GRAIN AlN-SiC BODIES |
| US3852099A (en) * | 1972-11-27 | 1974-12-03 | Gen Electric | Dense silicon carbide ceramic and method of making same |
| US3853566A (en) * | 1972-12-21 | 1974-12-10 | Gen Electric | Hot pressed silicon carbide |
| GB1478898A (en) * | 1973-10-24 | 1977-07-06 | Gen Electric | Silicon carbide ceramic |
| US3954483A (en) * | 1974-01-08 | 1976-05-04 | General Electric Company | Dense polycrystalline silicon carbide |
| US3960577A (en) * | 1974-01-08 | 1976-06-01 | General Electric Company | Dense polycrystalline silicon carbide |
| US4312954A (en) * | 1975-06-05 | 1982-01-26 | Kennecott Corporation | Sintered silicon carbide ceramic body |
| JPS5919903B2 (en) * | 1976-05-19 | 1984-05-09 | 日本特殊陶業株式会社 | Hot press manufacturing method of SiC sintered body |
| US4081284A (en) * | 1976-08-04 | 1978-03-28 | General Electric Company | Silicon carbide-boron carbide sintered body |
| DE2809278A1 (en) * | 1978-03-03 | 1979-09-06 | Kempten Elektroschmelz Gmbh | DENSE POLYCRYSTALLINE MOLDED BODY MADE OF ALPHA-SILICON CARBIDE AND THE PROCESS FOR THEIR PRODUCTION THROUGH PRESSURE-FREE SINTERING |
-
1979
- 1979-03-19 CA CA000323720A patent/CA1139791A/en not_active Expired
- 1979-06-11 GB GB7920262A patent/GB2023185B/en not_active Expired
- 1979-06-12 DE DE19792923729 patent/DE2923729A1/en active Granted
- 1979-06-14 FR FR7915280A patent/FR2432004B1/en not_active Expired
-
1987
- 1987-04-01 JP JP62077635A patent/JPS62275063A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62275063A (en) | 1987-11-30 |
| FR2432004A1 (en) | 1980-02-22 |
| DE2923729C2 (en) | 1989-07-20 |
| FR2432004B1 (en) | 1985-08-23 |
| DE2923729A1 (en) | 1980-01-03 |
| GB2023185B (en) | 1983-03-30 |
| GB2023185A (en) | 1979-12-28 |
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| MKEX | Expiry |