CERAMIC COMPOSITE BODY AND PRODUCTION THEREOF

Abstract: The ceramic composite body comprises a sintered ceramic body bonded to another sintered ceramic body or to a metal body by an intermediate layer of a ductile metal and a group IVa transition metal nitride.

Description: This invention relates to a novel bonded ceramic product having great bonded strength and suffering hardly from cracks or breaking in the vicinity of the bonded interface even when receiving heat shock, and also to a method of producing the same. Heretofore, as the method for bonding a metal member to a sintered ceramic body such as of alumina, there has been generally employed a method in which molybdenum paste is baked onto the surface of a sintered ceramic body, metallizing treatment is applied thereon and thereafter nickel plating is conducted, followed by soldering to effect bonding. However, this method involves a drawback that the pre-treatment procedures are very complicated. In recent years, as substitute for such a method, studies have been made about a simpler method to bond a metal member directly to a sintered ceramic body. For example, there has been developed a method in which a metal member is brought into contact with a metal member and heated in a gas atmosphere containing a binding agent such as oxygen, or a method in which a metal member containing a binding agent is brought into contact with a sintered ceramic body and heated in a non-oxidative atmosphere. However, according to such ceramics-metal bonded products of the prior art, the pre-treatment steps are complicated in all the methods. Besides, as compared with the coefficient of linear expansion of a sintered ceramic body, for example, that of Si₃N₄ which is as small as 2.46 to 4.1 x 10⁻⁶/ o C, that of conventionally employed iron is very great as 10 to 15 x 10⁻⁶/ o C, and therefore difficulties were involved in that cracks may be formed in the vicinity of the bonded interface of ceramics, even resulting in breaking in some cases. On the other hand, as the method for bonding a sintered ceramic body to a sintered ceramic body, other than the metallizing treatment as described above, development has been made about direct bonding between a sintered ceramic body and a sintered ceramic body through a copper foil or a metal foil of the group IVa transition metal (disclosed in U.S. Patent No. 2,857,663). However, according to the bonding method using copper foil, the bonding strength is insufficiently not higher than 10 kg/mm², and according to any method, when abrupt heat shock is given, cracks are liable to be formed in the vicinity of the bonded surface, until it may be broken disadvantageously. DE-B-16 46 934 describes a bonded ceramic product which comprises a sintered ceramic body bonded to another body by a ductile metal and a group IV transition metal nitride interposed therebetween. The present inventors have made extensive studies in order to cancel the drawbacks of the prior art, and consequently found that a bonded ceramic product having a great bonded strength and suffering hardly from generation of cracks at the bonded interface by heat shock can be obtained by allowing a ductile metal and a nitride of a group IV transition metal to exist between a sintered ceramic body and another sintered ceramic body or a metal member to be bonded; more specifically, it can be obtained by heating, for instance, a sintered nitride ceramic body and another sintered nitride ceramic body or a metal member with a ductile metal and a transition metal of the group IV interposed therebetween. This invention has been accomplished on the basis of such a finding, and it is intended to provide a bonded ceramic product having a great bonded strength and being also free from cracks or breaking even by abrupt heat shock. More specifically, the bonded ceramic product of this invention is characterized in that a sintered ceramic body is bonded to another sintered ceramic body or a metal member through a ductile metal and a group IV transition metal nitride interposed therebetween, as defined in the claims. The bonded ceramic product can be prepared by allowing a ductile metal and a nitride of a group IVa transition metal to exist between a sintered ceramic body and another sintered ceramic body or a metal member to be bonded, for example, according to either of the following embodiments. The invention includes: a) A bonded ceramic product comprising a sintered nitride ceramic body bonded to another sintered nitride ceramic body by a group IV transition metal nitride, produced by interposing layers, comprising a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between a foil of a ductile metal provided between the sintered nitride ceramic bodies and the sintered nitride ceramic bodies and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the ceramic bodies and the metal foil occurs. b) A bonded ceramic product comprising a sintered nitride ceramic body bonded to a ductile metal member by a group IV transition metal nitride, produced by interposing a layer, comprising a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between the sintered nitride ceramic body and the metal member and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the ceramic body and the metal member occurs. c) A bonded ceramic product comprising a sintered nitride ceramic body bonded to another sintered nitride ceramic body or a metal member by a group IV transition metal nitride, produced by interposing a compact comprising a mixed powder of powder of a ductile metal with powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal between the sintered nitride ceramic body and the other sintered nitride ceramic body or the metal member, and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the one ceramic body and the other ceramic body or the metal member occurs. In a preferred embodiment of the product a) or b) the group IV transition metal powder or the group IV transition metal compound powder is provided in a locally non-uniformly or intermittently distributed fashion. In a further specific embodiment of the product a) or b) this product is produced by a method wherein a wire of a group IV transition metal is used instead of the powder. The product of c) can be modified in that it is produced by a method wherein group IV transition metal fibers are mixed into the ductile metal powder or by a method wherein group IV transition metal fibers are embedded in both surfaces of a compact of ductile metal powder. Figs. 1 through 3 are enlarged side sectional views for illustration of the structure of the bonded ceramic products according to Examples of this invention; Fig. 4 is a perspective view of the same; and Figs. 5 and 6 are enlarged perspective views of the pressurized powder to be used in Examples of this invention. As shown in Fig. 1, on the bonding faces of sintered nitride ceramic bodies 1, 1, and on the surfaces of a ductile metal foil 2, a slurry prepared by dispersing in an organic solvent a powder of a group IV transition metal or a powder of a group IV transition metal compound capable of reacting with nitrogen, for example, is applied by coating and heat-dried to form layers 3 of the group IV transition metal powder or the group IV transition metal compound powder capable of reacting with nitrogen, which group IV transition metal powder layers 3 are superposed face to face, followed by heating in an inert atmosphere at a temperature not lower than the melting point of the intermediary layers to effect integration. When employing a ductile metal such as copper or a copper alloy as the metal member, the method can be embodied as follows: As shown in Fig. 2, at the bonding face between a sintered nitride ceramic body 1 and a metal member 4, a slurry prepared by dispersing a group IV transition metal powder in an organic solvent, for example, is applied by coating and heat-dried to form a group IV transition metal powder layer 3. Thereafter, the group IV transition metal powder layer 3 and the ductile metal member 4 are superposed face to face, followed by heating in an inert atmosphere and at a temperature not lower than the melting point of the intermediary layer. As shown in Fig. 3, a minute (for example, passing through 325 mesh (0.34 mm)) ductile metal powder together with a powder of a group IV transition metal powder or a powder of a group IV transition metal compound capable of reacting with nitrogen are mixed in an organic solvent such as an alcohol, and the resultant slurry is dried and press molded to a desired shape to mold a compact 5 with a thickness of about 0.1 to 5 mm. The mixing ratio of the ductile metal powder and the group IV transition metal powder is suitably within the range of ductile metal : group IV transition metal powder = 95 : 5 to 70 : 30. Next, between the sintered nitride ceramic bodies 1, 1, the compact 5 is sandwiched and heating is carried out at a temperature not lower than the melting point of the compact 5 to effect integration. As shown in Fig. 4, for instance, between a sintered nitride ceramic bodies 1, 1 and a ductile metal foil 2, a group IV transition metal is provided in a locally, ununiformly or intermittently distributed fashion, for example, by weaving of group IV transition metal wires, by bending thereof repeatedly on the same plane, by arrangement of a plural number of the wires in parallel, by provision of a large number of punches provided on a IV transition metal foil, or by scattering the group IV transition metal (in the drawing, there is shown a group IV transition metal wire which is repeatedly bent), on which another sintered ceramic body or a metal member is superposed through a ductile metal (not necessary when a metal member comprising a group IV metal is to be bonded), followed by heating at a temperature not lower than the melting points of the group IV transition metal and the ductile metal to effect integration. As shown in Fig. 5, in place of the compact 5 comprising the ductile metal powder and the group IV metal powder mentioned in the method of Fig. 3, a compact prepared by press molding similarly as in the method of Fig. 3 where the ductile metal powder 7 having the group IV transition metal fiber 8 mixed into the metal member powder is employed, or, as shown in Fig. 6, nets 9 comprising ductile metal fibers are arranged on both surfaces of a compact of the metal powder 7, followed again by pressurization to have a part of the nets embedded in the compact, and the resultant product is employed. The compounding ratio of the ductile metal to the group IV transition metal is made within the same range as the method of Fig. 3. At the interface of the bonded ceramic product thus bonded, nitrides of the group IV transition metal are formed through the reaction of the nitrogen in the sintered nitride ceramic body with the group IV transition metal or the group IV transition metal compound capable of reacting with nitrogen, or nitrides may be formed through the group IV transition metal nitride itself. The nitrides at the interface may be formed in various fashions, i.e., in a uniformly or evenly distributed fashion in the cases according to the methods shown in Fig. 1-3, and in a locally distributed fashion such that they are distributed in a continuous or discontinuous linear fashion, in a net fashion or in a scattered fashion in the cases according to the methods shown in Fig. 4-6. Moreover, the ductile metal is formed into alloy uniformly or locally with the group IV transition metal to form alloy layers with various compositions. The sintered ceramic bodies to be used in this invention may include sintered nitride ceramic bodies containing nitrides such as silicon nitrides, aluminum nitride, titanium nitride and complexes thereof, or oxynitrides such as sialon (Si-Al-O-N), etc. When the group IV transition metal nitride is used as the intermediary material, the sintered ceramic body may be comprised of sintered oxide type ceramic bodies such as of alumina, magnesia, etc. In particular, this invention is applicable to a dense product obtainable by pressureless sintering or hot pressed sintering. Also, the ductile metal which can be used in this invention may suitably be copper and its alloy. These (soft materials) have the following elongations: Among them, brass is inexpensive and 60 % or more elongation can be obtained with a zinc content within the range of from 20 to 40 wt. %, and therefore it is particularly suitable for this invention. Further, the group IV transition metal to be used in this invention may include titanium, zirconium, hafnium and others. Also, its compound capable of forming nitride by reaction with nitrogen, such as titanium dioxide (TiO₂) may also be used. As the group IV transition metal, titanium is suitable from the standpoint of cost. The bonded ceramic product thus obtained has a great bonded strength over 10 kg/mm² due to the presence of the interface layer of a group IV transition metal nitride, and there is no fear of formation of crack or breaking in the vicinity of the bonded interface of the sintered ceramic body on account of relaxation of stress due to the presence of a ductile metal, even when an abrupt heat shock may be applied. In the respective methods as described above, the method of applying a slurry on the bonded surface according to the methods shown in Fig. 1-3 is suitable when bonding surfaces are of complicated shapes. Also, in the case of bonding locally or intermittently the bonding surfaces according to the methods shown in Fig. 4-6, the stress relaxation effect can be further improved, whereby generation of cracks by heat shock can effectively be prevented. This invention is further illustrated by the following Examples. Example 1 A metallic titanium net with a wire diameter of 300 µm ⊘, and a mesh interval of 1.5 mm was sandwiched between a sintered ceramic body comprising pressureless sintered silicon nitride and a copper plate and bonded by heating in vacuum at about 1050 o C for 5 minutes. The bonded ceramic product thus obtained had a strength of 25 kg/mm² by shear and fracture occurred at the portion of the sintered ceramic body. Example 2 At the bonded faces of two sintered ceramic bodies comprising pressureless sintered silicon nitride, a slurry of titanium powder dispersed in ethyl alcohol was applied by coating in scattered dots of 400 µm in diameter and, after drying at about 400 o C for 5 minutes, the coated faces were superposed on each other through a copper plate with a thickness of about 300 µm, followed by heating in an argon gas atmosphere at about 1050 o C to effect bonding. The bonded ceramic product thus obtained had a shear strength of about 12 kg/mm². At the bonded interface of the bonded product of this Example, no microcrack was observed at all. However, in a comparative example, in which bonding was effected in the same manner except for applying titanium over the entire face of the sintered ceramic product, formation of microcracks was observed at the bonded interface. Thus, the product formerly unavailable due to formation of crack became sufficiently useful by acquisition of sufficient strength. Example 3 After copper powder (passable through 325 mesh) and metallic titanium short fibers (fiber diamter: 300 µm ⊘, fiber length: 2 mm) were mixed in ethyl alcohol and dried. Then, the mixture was molded by a press into a compact of 500 µm in thickness and 10 mm in both length and width. Next, these compacts were sandwiched between two sintered ceramic bodies comprising pressureless sintered silicon nitride and bonded by heating in an argon gas atmosphere at about 1050 o C for 5 minutes. The thus prepared ceramics bonded product had a shear strength of 20 kg/mm², and fracture occurred at the portion of the sintered ceramic body.

Claims: A bonded ceramic product comprising a sintered nitride ceramic body bonded to another sintered nitride ceramic body by a group IV transition metal nitride, produced by interposing layers, comprising a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between a foil of a ductile metal provided between the sintered nitride ceramic bodies and the sintered nitride ceramic bodies and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the ceramic bodies and the metal foil occurs. A bonded ceramic product comprising a sintered nitride ceramic body bonded to a ductile metal member by a group IV transition metal nitride, produced by interposing a layer, comprising a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between the sintered nitride ceramic body and the metal member and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the ceramic body and the metal member occurs. A bonded ceramic product comprising a sintered nitride ceramic body bonded to another sintered nitride ceramic body or a metal member by a group IV transition metal nitride, produced by interposing a compact, comprising a mixed powder of powder of a ductile metal with powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between the sintered nitride ceramic body and the other sintered nitride ceramic body or the metal member, and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the one ceramic body and the other ceramic body or the metal member occurs. A bonded ceramic product according to claim 1 produced by providing the group IV transition metal powder or the group IV transition metal compound powder in a locally non-uniformly or intermittently distributed fashion. A bonded ceramic product according to claim 2 produced by providing the group IV transition metal powder or the group IV transition metal compound powder in a locally non-uniformly or intermittently distributed fashion. A bonded ceramic product according to claim 1 modified in that it is produced by a method wherein a wire of a group IV transition metal is used instead of the powder. A bonded ceramic product according to claim 2 modified in that it is produced by a method wherein a wire of a group IV transition metal is used instead of the powder. A bonded ceramic product according to claim 3 modified in that it is produced by a method wherein group IV transition metal fibers are mixed into the ductile metal powder. A bonded ceramic product according to claim 3 modified in that it is produced by a method wherein group IV transition metal fibers are embedded in both surfaces of a compact of ductile metal powder. A method for producing a bonded ceramic product comprising a sintered nitride ceramic body bonded to another sintered nitride ceramic body by a group IV transition metal nitride, which comprises interposing layers, comprising a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between a foil of a ductile metal provided between the sintered nitride ceramic bodies and the sintered nitride ceramic bodies and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the ceramic bodies and the metal foil occurs. A method for producing a bonded ceramic product comprising a sintered nitride ceramic body bonded to a ductile metal member by a group IV transition metal nitride which comprises interposing a layer, comprising a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between the sintered nitride ceramic body and the metal member and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the ceramic body and the metal member occurs. A method for producing a bonded ceramic product comprising a sintered nitride ceramic body bonded to another sintered nitride ceramic body or a metal member by a group IV transition metal nitride, which comprises interposing a compact, comprising a mixed powder of powder of a ductile metal with a powder of a group IV transition metal capable of reacting with nitrogen or of a compound of the group IV transition metal, between the sintered nitride ceramic body and the other sintered nitride ceramic body or the metal member, and heating in an inert or reducing atmosphere at a temperature at which melting of at least some of the material interposed between the one ceramic body and the other ceramic body or the metal member occurs.

Inventors: IKEDA, KAZUO KABUSHIKI KAISHA TOSHIBA, SAYANO, AKIO KABUSHIKI KAISHA TOSHIBA, TANAKA, SHUN-ICHIRO KABUSHIKI KAISHA TOSHIBA
Applicants: KABUSHIKI KAISHA TOSHIBA
Application year: 1984
Main classification: C04B37
IPC codes: C04B37, H05K3, H05K1, B23K20, B23K1