CA1077969A - Method for producing a composite consisting of continuous silicon carbide fibers and metallic silicon - Google Patents
Method for producing a composite consisting of continuous silicon carbide fibers and metallic siliconInfo
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- CA1077969A CA1077969A CA264,032A CA264032A CA1077969A CA 1077969 A CA1077969 A CA 1077969A CA 264032 A CA264032 A CA 264032A CA 1077969 A CA1077969 A CA 1077969A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C49/00—Alloys containing metallic or non-metallic fibres or filaments
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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
- C04B35/56—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
- C04B35/571—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 from Si-containing polymer precursors or organosilicon monomers
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- Engineering & Computer Science (AREA)
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- Organic Chemistry (AREA)
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- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
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- Ceramic Products (AREA)
- Inorganic Fibers (AREA)
- Manufacture Of Alloys Or Alloy Compounds (AREA)
- Laminated Bodies (AREA)
Abstract
Abstract of the Disclosure Fiber composites having high hardness, mechanical strength, heat resistance, oxidation resistance and corrosion resistance consisting of continuous silicon carbide fibers and metallic silicon.
Description
107~g~;~
The present invention relates to a method for producing a fiber composite consisting of continuous silicon carbide fibers and metallic silicon and more particularly, a method for producing a three dimensional fiber composite having a high strength and maintaining excellent properties of novel continuous silicon carbide fibers having extremely excellent hardness, mechanical strength, heat resistance, oxidation resistance and corrosion resistance by using metallic silicon for said continuous silicon carbide fibers as a binder.
Heretofore, as refractory materials having a high strength, use has been made of ceramics sintered articles having a high melting point, cermets or ceramics composite materials reinforced with ceramics fibers or whiskers having a high melting point. However, the ceramics sintered articles are usually weak in the mechanical shock, particu- `
larly are poor in the mechanical strength at a high tempera-ture. Furthermore, since the cermets contain a metal as the matrix, they have a relatively high resistance against the mechanical shock but when the cermets are used under an oxidizing atmosphere at a high temperature, the metal is readily oxidized and softened, so that the life for maintain-ing the properties at a high temperature is short and the scope of application is considerably limited.
The ceramics composite materials reinforced by fibers or whiskers are considerably influenced in the property or practicability by the reinforcing fibers or whiskers.
Namely, the reinforcing effect due to the fibers or whiskers is increased by arranging said fibers or whiskers in a certain direction but when short fibers or whiskers are used, the
The present invention relates to a method for producing a fiber composite consisting of continuous silicon carbide fibers and metallic silicon and more particularly, a method for producing a three dimensional fiber composite having a high strength and maintaining excellent properties of novel continuous silicon carbide fibers having extremely excellent hardness, mechanical strength, heat resistance, oxidation resistance and corrosion resistance by using metallic silicon for said continuous silicon carbide fibers as a binder.
Heretofore, as refractory materials having a high strength, use has been made of ceramics sintered articles having a high melting point, cermets or ceramics composite materials reinforced with ceramics fibers or whiskers having a high melting point. However, the ceramics sintered articles are usually weak in the mechanical shock, particu- `
larly are poor in the mechanical strength at a high tempera-ture. Furthermore, since the cermets contain a metal as the matrix, they have a relatively high resistance against the mechanical shock but when the cermets are used under an oxidizing atmosphere at a high temperature, the metal is readily oxidized and softened, so that the life for maintain-ing the properties at a high temperature is short and the scope of application is considerably limited.
The ceramics composite materials reinforced by fibers or whiskers are considerably influenced in the property or practicability by the reinforcing fibers or whiskers.
Namely, the reinforcing effect due to the fibers or whiskers is increased by arranging said fibers or whiskers in a certain direction but when short fibers or whiskers are used, the
- 2 -107',~9~9 length is short, so that it is difficult to arrange these materials in the uniform direction throughout the whole matrix and the matrix is readily broken at end portion of the fibers or whiskers owing to the concentration of shearing stress of the matrix and further the arranging step is complicated, so that there is a defect that the production cost becomes high.
Moreover, the length of the whiskers is up to about 20 mm and the fineness is not constant and the whiskers having constant properties are difficult to be obtained. In addition, the production step is fairly complicated, so that the production cost becomes high.
There is a process for improving the above described arranging ability and preventing the shear breakage by using ceramics continuous fibers and as these continuous fibers, use has been made of the fibers composed of fused quartz, alumina single crystal or carbon.
However, the fused quartz fibers are poor in Young's modulus, alumina fibers are high in the production cost and poor in the thermal shock resistance and carbon fibers cannot endure use in an oxidizing atmosphere at a high temperature and therefore the respective fiber is limited in the use application.
Furthermore, concerning the carbon fibers, a process wherein carbon fibers are immersed in fused Si at a temperature lower than 1,500C to concurrently conduct the conversion of carbon fibers into silicon carbide and the formation of SiC-Si composite, has been described in "THE
ENGINEER", for Nov. 1974. However, the carbon fibers are complicated in the production step, so that the production ~(~77969 cost is high, and said fibers include a fairly large amount of pores and amorphous carbon and consequently the homogeneity in properties and the uniformity are poor, so that the silicon carbide fibers obtained by immersing the fibers in the fused metallic silicon are uneven in the fineness and the strength is locally different. Furthermore, when metallic silicon penetrated into pores in the above described carbon fibers solidifies and contracts, the adhesion of silicon in the pores and the newly formed fibrous silicon carbide becomes weak resulting into lowering of the strength. Accordingly, the composite material composed of silicon carbide fibers and metallic silicon, which is formed of carbon fibers and the fused metallic silicon, is not only high in the cost but also the strength is low and is not uni-form.
; An object of the present invention is to provide a method for producing SiC-Si composite material having homogeneity in properties and high strength in a low production cost which obviates various defects of the above described SiC-Si composite material produced from the carbon fibers and metallic silicon.
The method of the present invention will be explained in more detail.
The present invention can provide SiC-Si composite materials having a high strength, which are composite materials of continuous fibers having a high strength, by forming piles of a bundle form, a network form, a rope form, a layer form and the like from high strength continuous silicon carbide fibers and filling spaces in the pile with fused silicon to tightly adhere the fibers and silicon.
; The term "pile" used herein means the above described "bundle form", "network form", "rope form" and "layer form" and the like of the continuous silicon carbide fibers.
"High Strength continuous silicon carbide fibers" which can be advantageously used in the present invention may be produced by the ~077969 production method disclosed in Canadian Patent Application No. 250,637 already filed by the inventors of the present invention. More particularly, in o:rder to produce such fibers organosilicon low molecular weight compounds of the following groups (1)-(10) can be used as the starting material.
(1) Compounds having only Si-C bond.
(2) Compounds having Si-H bond in addition to Si-C bond.
Moreover, the length of the whiskers is up to about 20 mm and the fineness is not constant and the whiskers having constant properties are difficult to be obtained. In addition, the production step is fairly complicated, so that the production cost becomes high.
There is a process for improving the above described arranging ability and preventing the shear breakage by using ceramics continuous fibers and as these continuous fibers, use has been made of the fibers composed of fused quartz, alumina single crystal or carbon.
However, the fused quartz fibers are poor in Young's modulus, alumina fibers are high in the production cost and poor in the thermal shock resistance and carbon fibers cannot endure use in an oxidizing atmosphere at a high temperature and therefore the respective fiber is limited in the use application.
Furthermore, concerning the carbon fibers, a process wherein carbon fibers are immersed in fused Si at a temperature lower than 1,500C to concurrently conduct the conversion of carbon fibers into silicon carbide and the formation of SiC-Si composite, has been described in "THE
ENGINEER", for Nov. 1974. However, the carbon fibers are complicated in the production step, so that the production ~(~77969 cost is high, and said fibers include a fairly large amount of pores and amorphous carbon and consequently the homogeneity in properties and the uniformity are poor, so that the silicon carbide fibers obtained by immersing the fibers in the fused metallic silicon are uneven in the fineness and the strength is locally different. Furthermore, when metallic silicon penetrated into pores in the above described carbon fibers solidifies and contracts, the adhesion of silicon in the pores and the newly formed fibrous silicon carbide becomes weak resulting into lowering of the strength. Accordingly, the composite material composed of silicon carbide fibers and metallic silicon, which is formed of carbon fibers and the fused metallic silicon, is not only high in the cost but also the strength is low and is not uni-form.
; An object of the present invention is to provide a method for producing SiC-Si composite material having homogeneity in properties and high strength in a low production cost which obviates various defects of the above described SiC-Si composite material produced from the carbon fibers and metallic silicon.
The method of the present invention will be explained in more detail.
The present invention can provide SiC-Si composite materials having a high strength, which are composite materials of continuous fibers having a high strength, by forming piles of a bundle form, a network form, a rope form, a layer form and the like from high strength continuous silicon carbide fibers and filling spaces in the pile with fused silicon to tightly adhere the fibers and silicon.
; The term "pile" used herein means the above described "bundle form", "network form", "rope form" and "layer form" and the like of the continuous silicon carbide fibers.
"High Strength continuous silicon carbide fibers" which can be advantageously used in the present invention may be produced by the ~077969 production method disclosed in Canadian Patent Application No. 250,637 already filed by the inventors of the present invention. More particularly, in o:rder to produce such fibers organosilicon low molecular weight compounds of the following groups (1)-(10) can be used as the starting material.
(1) Compounds having only Si-C bond.
(2) Compounds having Si-H bond in addition to Si-C bond.
(3) Compounds having Si-Ha~ bond.
(4) Compounds having Si-N bond.
(5) Compounds having Si-OR ~R is alkyl or aryl group) bond.
(6) Compounds having Si-OH bond.
~7) Compounds having Si-Si bond.
(8) Compounds having Si-O-Si bond.
~9) Esters of organosilicon compounds.
(10) Peroxides of organosilicon compounds.
From at least one of the organosilicon low molecular weight compounds belongingtothe above described groups (1)-(10), organosilicon high molecular weight compounds having silicon and carbon as the main skeleton components, for example, the compounds having the following molecular \
~77~6~
structures, are produced by polycondensation reaction using at least one process of irradiation, heating and addition of a catalyst for the poly-condensation (al ~Si.(C)n-Si-O-~b2 Si-O-CC)n-O-CC1 -Sl~ (Cln~
(d~ The compounds having the above described skeleton c~mponents (a)~(c~ as at least one of partial structures in linear, ring and three dimensional structures or mixtures of the compounds having the above described skeleton components ` (a~-(c~
From at least one of the organosilicon high molecular weight compounds containing at least one of the above described molecuiar structures, if necessary added with or reacted with a small amount of at least one of oTganic metal compounds, metal complexes and organic polymers other than the above described two compounds, is prepared a spinning liquid and then ; the spinning liquid can be spun into fibers having various lengths and uniform fineness. The spun fibers are heated at a low temperature within a temperature range of 50-400C under an oxidi~ing atmosphere and then preliminarily heated at a temperature of 600-1,000C under at least one atmosphere of vacuum, inert gases, C0 gas, hydrocarbon compound gas, organosilicon compound gas and hydrogen gas to form the preliminarily ~ .
~ ~ -6_ :
~0779G9 heated continuous silicon carbide fibers. Ilowever, the above described preliminary heating is able to get along even under the above described atmosphere containing at least one of an oxidizing gas, a hydrocarbon compound gas and hydrogen gas in a partial pressure of less than 10 mmHg.
The above described preliminarily heated fibers are baked at a temperature of 1,000-2,000C under at least one of atmos-pheres of vacuum, inert gases, CO gas, CO2 gas, hydrocarbon compound gas, organosilicon compound gas and hydrogen gas to form continuous silicon carbide fibers.
Various properties of SiC fibers having a fineness of about 10 ~ obtained by baking at 1,300C under vacuum according to the above described method of the prior invention are shown in ~he following Table 1. A bundle of the continuous SiC fibers is shown in a photograph.
Table 1 Size of crystal grain Average diameter 33 Density 2.5 - 3.1 g/cm3 Hardness 9 (Mohs) Tensile strength 300 - 500 Kg/mm2 _ Young's modulus (2.0-4.0)X10 4 Kg/mm2 Even if the fibers are kept at Oxidation resistance 1,300C for 100 hours in air, the weight variation is not observed.
Even if rapid heating and quenching Thermal shock cycle of 25C t 1,000C is repeated resistance more than 1,000 times, the texture does not vary.
10779~g In the above described silicon carbide fibers obtained by baking the spun fibers consisting mainly of the organosilicon high molecular weight compound, free carbon of more than 0.01% usually remains and the remaining amount varies depending upon various conditions, such as the baking tempera-ture, baking time and baking atmosphere. This free carbon reacts with the fused silicon to form SiC at the boundary of SiC fibers and Si. Therefore, the bonding of SiC fibers to the Si is promoted by the tight adhesion owing to the local chemical reaction due to the free carbon at the boundary of SiC fibers and the metallic Si in addition to the adhesion due to the wettability and the more strong bonding can be attained, so that the above described free carbon acts a very advantageous function in the formation of SiC-Si composite material. Furthermore, in SiC fibers produced as above, the size of the crystal grains is several ten A as shown in the above described Table 1, so that a number of microscopic unevenness (projection and recess) on the surface of the fiber becomes very large per unit area and the fused silicon gets into the uneven portions and the contact area becomes considerably larger and the adhesion of the fibers and the metallic silicon becomes very strong due to the wettability and this is a great characteristic of the present invention.
The merit of the present invention that the spaces of SiC fiber pile are filled with Si consists in the following points. Si is different from the other metals and even if silicon in the fused state contacts with SiC mainly constituting the fibers, the fused silicon does not cause any reaction by which the properties of SiC fibers are deteriorated and further has a good wettability and the very tight bonding between Sic fibers and Si can be obtained owing to the mutual diffusion of Sic and Si.
As a further advantage if fibers are used as produced as described above, free carbon usually remaining in such fibers reacts with Si to form Sic and this Sic has the function that the bonding of SiC fibers and Si is greatly i~creased. Furthermore, silicon itself is relatively small in decrease of ~077969 the toughness and strength even at a high temperature and silicon is preferable as the metal capable of maintaining the above described pro-perties of the composite material to a high temperature. As mentioned above, it has been found that the fibers and the silicon to be used in the present invention are the most preferable raw materials for constituting the composite material for production of the fiber composite having a high strength due to strong adhesion.
Although there are various processes for production of metal-fiber composite material, it is advantageous to form a composite material from the fibers to be used in the present invention and silicon through either of the following four processes.
(1) The fiber pile is merely immersed in the fused Si under vacuum or an inert gas.
(2) This process is similar to the above process (1) but the fibers are passed through a vessel containing the fused silicon and are pulled up or pulled down to form a fiber bundle.
(3) Each fiber or the fiber pile is coated with the fused Si and then the fibers are subjected to a hot press.
11~7~9~9 (4) The fibers are put in a mold and then the fused silicon is poured into the mold or the fibeTs and the solid Si are put in a mold and then the mold is heated to a tempe~ature higher than the melting point of t:he Si to foTm the composite molding.
In these processes, it is more effective that the fibers and the fused silicon are integrated under a reduced pressure and then the atmosphere is changed into a pressed state, whereby the bonding degree is more increased.
By using the above described processes, it is possible to obtain the homo-geneous and strong fiber composites without forming pores and hollow gaps between the fibers and the metal.
It is preferable that a content of the silicon in the fiber composites according to the present invention is 5-35% by weight. When the content is less than 5%, the spaces in the fiber pile cannot be fully filled, so that it is impossible to obtain a satisfactory fiber composite composed of the fibers and the metal and the homogeneity and strength of the composite material are not satisfied On the other hand, when the content is more than 35%, the space in the fiber pile becomes too broad and the influence due to the property of the silicon is larger than that of the fibers, so that the high strength and heat resistance of the fibers cannot be maintained.
The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof~
107796~
Example 1 An example for producing the continuous silicon carbide fibers to be used in the present invention will be explained hereinafter.
Dimethyldichlorosilane and sodium were reacted to produce dimethylpolysilane. 250 g of dimethylpolysilane was charged in an autoclave having a capacity of 1 Q and air in the autoclave was substituted with argon gas and then the reaction was effected at 470C for 14 hours. After comple-tion of the reaction, the formed polycarbosilane was discharged as N-hexane solution. This N-hexane solution was filtrated to remove impurities and then N-hexane was evaporated under a reduced pressure, after which the residue was heated in an oil bath at 280C under vacuum for 2 hours to effect concen-tration. Polycarbosilane was obtained in an yield of 40 based on dimethyldichlorosilane. A number average molecular weight of the formed polycarbosilane was 1,700. By using a usual spinning apparatus, the polycarbosilane was heated and melted at 330C under argon atmosphere to form a spinning melt and the spinning melt was spun at a spinning rate of 200 m/min to obtain polycarbosilane fibers. The fibers were heated by raising the temperature from 20C to 190C in air in 6 hours and this temperature was kept for l hour to effect an unfusing treatment. The thus treated fibers were heated to 1,300C at a temperature raising rate of 100C/hr under vacuum of lxlo-3 mmHg and this temperature was kept for 1 hour to form SiC fibers. The formed SiC fibers had an average diameter of 15 ~, an average tensile strength of 350 Kg/mm2, an average Young's modulus of 23x103 Kg/mm2 and a specific gravity of 2.70 g/cm3.
1~779~
From silicon and the silicon carbide fibers produced as described above, fiber composites were produced by varying the content of the metallic silicon as shown in the following Table 2~
The fibers produced as described above and having a length of 50 m~ were formed into a bundle and said bundle was s~t in an alumina crucible C12~xSOL~m3~ This c~ucible was suspended at an uppeT portion of a heating vessel under vacuum of lx10-3 mnHg. At the lower portion in this vessel was placed a tank made of alumina for charging the fused metallic silicon and the tank was heated and the metallic silicon in the tank was kept at the fused state at 1,500C~ Then the cTucible w~s put down and immersed in the fused metal in the tank and the immersing was kept for 5 minutes~ Thereafter, 10 atmospheric pressures of argon gas was applied to the vessel and said pressure was kept for 10 minutes and then the c~ucible was taken out from the tank. The thus formed fiber composite was worked into a rod having lO~x40Lmm and said rod was tested with respect to various properties~ ~:
The content of the silicon in each fiber composite and the properties of this composite are shown in the following Table 2~
:-1077g~9 Table 2 '~ Content of _ \ metallic \ ilicon 5 10 20 30 . Property \ __ _ Density (g/cm3) 2.7 2.6 2.5 2.4 Hardness (Mohs) 9 8_~ 8_9 8 __ _ _ Tensile strength ~Kg/mm23 320-460 30a-410 270 330 250-300 Young's modulus . _ (Kg/mm2) (10-15)x10 (8-13)x10 (7-ll)x10 (6-10)x10 Oxidation resist- _ ance. Weight increase in air nearly 0 0-1 1-2 2-3 at 1,000C for 50 hours (%) As seen from the above Table 2, continuous SiC fiber composites produced by using silicon are composites having various excellent propeTties.
Example 2 Silicon carbide fibers obtained in Example 1 were formed into a network having a mesh area of 0.1 0.3 mm2 and an outer size of 30mmX30mmXlmm~
This network was placed on a bottom of dies (female die) for a hot press made of alumina and then metallic silicon powders were deposited in a thickness of about 3 mm on the ~etwork and the assembly was heated at 1,450C under vacuum of lx10 4 mmHg~ As soon as the temperature was raised to 1,450C, the temperature was decreased at a rate of 5C/min, while applying a pressure of 100 Kg~cm . However, the dies have been previously designed so that when the fused metallic silicon was pressed by the male die, the 1~779~9 superfluous fused silicon other than the fused si]icon which fills the mesh, was overflowed into the space between the male die and the female die~ A composite sheet in which silicon carbide fibers of the network are included in the metallic silicon was produced. The content of the fibers in this sheet was about 80% by weight as the result of analysis~ The stsength and the other properties of this composite sheet were similar to those of the corresponding composition shown in Table 2 but it has been found that this sheet is excellent particularly in elastic modulus for bending~ Therefore, this sheet can be used as a heat resistant sheet under a temperature up to 1,350C
Example 3 In such a silicon carbide mold that a pipe having an outer diameter of 30 mm, an inner diameter of 25 mm and a length of 15 mm can be obtained, were arranged continuous silicon carbide fibers having a length of 100-150 mm produced in Example 1 and the mold was placed under yacuum of lxlO 3 mnHg. Into this mold was poured silicon previously fused by heating at l,500C. In this manner, a cylindrical silicon carbide fiber composite molding was obtained. The content of the fibers in this composite was 70% by weight and the strength and the other pro-perties of this composite were similar to those of the coTresponding composition shown in the above described Table 2. Such a molding is excellent in the elasticity, so that even if the molding has an oval form, such a lding is not easily broken, so that this molding is advantageously used as a ~lexible circular pipe for a high temperature.
~14-Example 4 Silicon previously fused in argon gas was charged in a continuous casting vessel ~50cmx50c~x50cm~ and about 200 continuous SiC fibers produced in Example l were passed downwards through said vessel and passed through a hole provided at the center of the bottom of the vessel to collect the fibers and wound up at a rate of 1 m/min in such a manner that Si fiber bundle was twisted~ Before the winder, a cooling coil was provided and the twisted fiber bundle coated with the fused silicon was passed through said coil, whereby the superfluous fused silicon was taken away and said ibeT bundle was cooled and the fused metallic silicon was solidified.
The weight ratio of the fibers in the formed SiC fiber composite having a rope form was about 90% and the properties of this composite are equal to those of the corresponding composition in the above Table 2. Such a fiber composite having a rope form was relatively excellent in the elastic modulus for bending, so that this composite seems to endure the use under a stress at a high te~perature.
The above described examples showed a few embodiments having the typical shapes, which can be obtained as the continuous SiC fiber composite, ~ut in addition to these embodiments, the composites having various shapes 2~ can be obtained depending upon the shape of the fiber piles or the shape of the mold.
As mentioned above, the continuous silicon carbide fiber composites having excellent mechanical strength, heat resistance, oxidation resistance and corro~ion resistance ~15 can be obtained in a relatively low cost according to the present invention and it can be expected that these compo-sites can be very advantageously used in many fields where use must be made under severe conditions, such as super high temperature, super high pressure and corrosive atmosphere. -For example, these composites can be used for various crucibles, various nozzles, turbine blades, engine con-stituting materials, wear resistant parts, heat resistant materials, aircraft materials and the like.
,
~7) Compounds having Si-Si bond.
(8) Compounds having Si-O-Si bond.
~9) Esters of organosilicon compounds.
(10) Peroxides of organosilicon compounds.
From at least one of the organosilicon low molecular weight compounds belongingtothe above described groups (1)-(10), organosilicon high molecular weight compounds having silicon and carbon as the main skeleton components, for example, the compounds having the following molecular \
~77~6~
structures, are produced by polycondensation reaction using at least one process of irradiation, heating and addition of a catalyst for the poly-condensation (al ~Si.(C)n-Si-O-~b2 Si-O-CC)n-O-CC1 -Sl~ (Cln~
(d~ The compounds having the above described skeleton c~mponents (a)~(c~ as at least one of partial structures in linear, ring and three dimensional structures or mixtures of the compounds having the above described skeleton components ` (a~-(c~
From at least one of the organosilicon high molecular weight compounds containing at least one of the above described molecuiar structures, if necessary added with or reacted with a small amount of at least one of oTganic metal compounds, metal complexes and organic polymers other than the above described two compounds, is prepared a spinning liquid and then ; the spinning liquid can be spun into fibers having various lengths and uniform fineness. The spun fibers are heated at a low temperature within a temperature range of 50-400C under an oxidi~ing atmosphere and then preliminarily heated at a temperature of 600-1,000C under at least one atmosphere of vacuum, inert gases, C0 gas, hydrocarbon compound gas, organosilicon compound gas and hydrogen gas to form the preliminarily ~ .
~ ~ -6_ :
~0779G9 heated continuous silicon carbide fibers. Ilowever, the above described preliminary heating is able to get along even under the above described atmosphere containing at least one of an oxidizing gas, a hydrocarbon compound gas and hydrogen gas in a partial pressure of less than 10 mmHg.
The above described preliminarily heated fibers are baked at a temperature of 1,000-2,000C under at least one of atmos-pheres of vacuum, inert gases, CO gas, CO2 gas, hydrocarbon compound gas, organosilicon compound gas and hydrogen gas to form continuous silicon carbide fibers.
Various properties of SiC fibers having a fineness of about 10 ~ obtained by baking at 1,300C under vacuum according to the above described method of the prior invention are shown in ~he following Table 1. A bundle of the continuous SiC fibers is shown in a photograph.
Table 1 Size of crystal grain Average diameter 33 Density 2.5 - 3.1 g/cm3 Hardness 9 (Mohs) Tensile strength 300 - 500 Kg/mm2 _ Young's modulus (2.0-4.0)X10 4 Kg/mm2 Even if the fibers are kept at Oxidation resistance 1,300C for 100 hours in air, the weight variation is not observed.
Even if rapid heating and quenching Thermal shock cycle of 25C t 1,000C is repeated resistance more than 1,000 times, the texture does not vary.
10779~g In the above described silicon carbide fibers obtained by baking the spun fibers consisting mainly of the organosilicon high molecular weight compound, free carbon of more than 0.01% usually remains and the remaining amount varies depending upon various conditions, such as the baking tempera-ture, baking time and baking atmosphere. This free carbon reacts with the fused silicon to form SiC at the boundary of SiC fibers and Si. Therefore, the bonding of SiC fibers to the Si is promoted by the tight adhesion owing to the local chemical reaction due to the free carbon at the boundary of SiC fibers and the metallic Si in addition to the adhesion due to the wettability and the more strong bonding can be attained, so that the above described free carbon acts a very advantageous function in the formation of SiC-Si composite material. Furthermore, in SiC fibers produced as above, the size of the crystal grains is several ten A as shown in the above described Table 1, so that a number of microscopic unevenness (projection and recess) on the surface of the fiber becomes very large per unit area and the fused silicon gets into the uneven portions and the contact area becomes considerably larger and the adhesion of the fibers and the metallic silicon becomes very strong due to the wettability and this is a great characteristic of the present invention.
The merit of the present invention that the spaces of SiC fiber pile are filled with Si consists in the following points. Si is different from the other metals and even if silicon in the fused state contacts with SiC mainly constituting the fibers, the fused silicon does not cause any reaction by which the properties of SiC fibers are deteriorated and further has a good wettability and the very tight bonding between Sic fibers and Si can be obtained owing to the mutual diffusion of Sic and Si.
As a further advantage if fibers are used as produced as described above, free carbon usually remaining in such fibers reacts with Si to form Sic and this Sic has the function that the bonding of SiC fibers and Si is greatly i~creased. Furthermore, silicon itself is relatively small in decrease of ~077969 the toughness and strength even at a high temperature and silicon is preferable as the metal capable of maintaining the above described pro-perties of the composite material to a high temperature. As mentioned above, it has been found that the fibers and the silicon to be used in the present invention are the most preferable raw materials for constituting the composite material for production of the fiber composite having a high strength due to strong adhesion.
Although there are various processes for production of metal-fiber composite material, it is advantageous to form a composite material from the fibers to be used in the present invention and silicon through either of the following four processes.
(1) The fiber pile is merely immersed in the fused Si under vacuum or an inert gas.
(2) This process is similar to the above process (1) but the fibers are passed through a vessel containing the fused silicon and are pulled up or pulled down to form a fiber bundle.
(3) Each fiber or the fiber pile is coated with the fused Si and then the fibers are subjected to a hot press.
11~7~9~9 (4) The fibers are put in a mold and then the fused silicon is poured into the mold or the fibeTs and the solid Si are put in a mold and then the mold is heated to a tempe~ature higher than the melting point of t:he Si to foTm the composite molding.
In these processes, it is more effective that the fibers and the fused silicon are integrated under a reduced pressure and then the atmosphere is changed into a pressed state, whereby the bonding degree is more increased.
By using the above described processes, it is possible to obtain the homo-geneous and strong fiber composites without forming pores and hollow gaps between the fibers and the metal.
It is preferable that a content of the silicon in the fiber composites according to the present invention is 5-35% by weight. When the content is less than 5%, the spaces in the fiber pile cannot be fully filled, so that it is impossible to obtain a satisfactory fiber composite composed of the fibers and the metal and the homogeneity and strength of the composite material are not satisfied On the other hand, when the content is more than 35%, the space in the fiber pile becomes too broad and the influence due to the property of the silicon is larger than that of the fibers, so that the high strength and heat resistance of the fibers cannot be maintained.
The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof~
107796~
Example 1 An example for producing the continuous silicon carbide fibers to be used in the present invention will be explained hereinafter.
Dimethyldichlorosilane and sodium were reacted to produce dimethylpolysilane. 250 g of dimethylpolysilane was charged in an autoclave having a capacity of 1 Q and air in the autoclave was substituted with argon gas and then the reaction was effected at 470C for 14 hours. After comple-tion of the reaction, the formed polycarbosilane was discharged as N-hexane solution. This N-hexane solution was filtrated to remove impurities and then N-hexane was evaporated under a reduced pressure, after which the residue was heated in an oil bath at 280C under vacuum for 2 hours to effect concen-tration. Polycarbosilane was obtained in an yield of 40 based on dimethyldichlorosilane. A number average molecular weight of the formed polycarbosilane was 1,700. By using a usual spinning apparatus, the polycarbosilane was heated and melted at 330C under argon atmosphere to form a spinning melt and the spinning melt was spun at a spinning rate of 200 m/min to obtain polycarbosilane fibers. The fibers were heated by raising the temperature from 20C to 190C in air in 6 hours and this temperature was kept for l hour to effect an unfusing treatment. The thus treated fibers were heated to 1,300C at a temperature raising rate of 100C/hr under vacuum of lxlo-3 mmHg and this temperature was kept for 1 hour to form SiC fibers. The formed SiC fibers had an average diameter of 15 ~, an average tensile strength of 350 Kg/mm2, an average Young's modulus of 23x103 Kg/mm2 and a specific gravity of 2.70 g/cm3.
1~779~
From silicon and the silicon carbide fibers produced as described above, fiber composites were produced by varying the content of the metallic silicon as shown in the following Table 2~
The fibers produced as described above and having a length of 50 m~ were formed into a bundle and said bundle was s~t in an alumina crucible C12~xSOL~m3~ This c~ucible was suspended at an uppeT portion of a heating vessel under vacuum of lx10-3 mnHg. At the lower portion in this vessel was placed a tank made of alumina for charging the fused metallic silicon and the tank was heated and the metallic silicon in the tank was kept at the fused state at 1,500C~ Then the cTucible w~s put down and immersed in the fused metal in the tank and the immersing was kept for 5 minutes~ Thereafter, 10 atmospheric pressures of argon gas was applied to the vessel and said pressure was kept for 10 minutes and then the c~ucible was taken out from the tank. The thus formed fiber composite was worked into a rod having lO~x40Lmm and said rod was tested with respect to various properties~ ~:
The content of the silicon in each fiber composite and the properties of this composite are shown in the following Table 2~
:-1077g~9 Table 2 '~ Content of _ \ metallic \ ilicon 5 10 20 30 . Property \ __ _ Density (g/cm3) 2.7 2.6 2.5 2.4 Hardness (Mohs) 9 8_~ 8_9 8 __ _ _ Tensile strength ~Kg/mm23 320-460 30a-410 270 330 250-300 Young's modulus . _ (Kg/mm2) (10-15)x10 (8-13)x10 (7-ll)x10 (6-10)x10 Oxidation resist- _ ance. Weight increase in air nearly 0 0-1 1-2 2-3 at 1,000C for 50 hours (%) As seen from the above Table 2, continuous SiC fiber composites produced by using silicon are composites having various excellent propeTties.
Example 2 Silicon carbide fibers obtained in Example 1 were formed into a network having a mesh area of 0.1 0.3 mm2 and an outer size of 30mmX30mmXlmm~
This network was placed on a bottom of dies (female die) for a hot press made of alumina and then metallic silicon powders were deposited in a thickness of about 3 mm on the ~etwork and the assembly was heated at 1,450C under vacuum of lx10 4 mmHg~ As soon as the temperature was raised to 1,450C, the temperature was decreased at a rate of 5C/min, while applying a pressure of 100 Kg~cm . However, the dies have been previously designed so that when the fused metallic silicon was pressed by the male die, the 1~779~9 superfluous fused silicon other than the fused si]icon which fills the mesh, was overflowed into the space between the male die and the female die~ A composite sheet in which silicon carbide fibers of the network are included in the metallic silicon was produced. The content of the fibers in this sheet was about 80% by weight as the result of analysis~ The stsength and the other properties of this composite sheet were similar to those of the corresponding composition shown in Table 2 but it has been found that this sheet is excellent particularly in elastic modulus for bending~ Therefore, this sheet can be used as a heat resistant sheet under a temperature up to 1,350C
Example 3 In such a silicon carbide mold that a pipe having an outer diameter of 30 mm, an inner diameter of 25 mm and a length of 15 mm can be obtained, were arranged continuous silicon carbide fibers having a length of 100-150 mm produced in Example 1 and the mold was placed under yacuum of lxlO 3 mnHg. Into this mold was poured silicon previously fused by heating at l,500C. In this manner, a cylindrical silicon carbide fiber composite molding was obtained. The content of the fibers in this composite was 70% by weight and the strength and the other pro-perties of this composite were similar to those of the coTresponding composition shown in the above described Table 2. Such a molding is excellent in the elasticity, so that even if the molding has an oval form, such a lding is not easily broken, so that this molding is advantageously used as a ~lexible circular pipe for a high temperature.
~14-Example 4 Silicon previously fused in argon gas was charged in a continuous casting vessel ~50cmx50c~x50cm~ and about 200 continuous SiC fibers produced in Example l were passed downwards through said vessel and passed through a hole provided at the center of the bottom of the vessel to collect the fibers and wound up at a rate of 1 m/min in such a manner that Si fiber bundle was twisted~ Before the winder, a cooling coil was provided and the twisted fiber bundle coated with the fused silicon was passed through said coil, whereby the superfluous fused silicon was taken away and said ibeT bundle was cooled and the fused metallic silicon was solidified.
The weight ratio of the fibers in the formed SiC fiber composite having a rope form was about 90% and the properties of this composite are equal to those of the corresponding composition in the above Table 2. Such a fiber composite having a rope form was relatively excellent in the elastic modulus for bending, so that this composite seems to endure the use under a stress at a high te~perature.
The above described examples showed a few embodiments having the typical shapes, which can be obtained as the continuous SiC fiber composite, ~ut in addition to these embodiments, the composites having various shapes 2~ can be obtained depending upon the shape of the fiber piles or the shape of the mold.
As mentioned above, the continuous silicon carbide fiber composites having excellent mechanical strength, heat resistance, oxidation resistance and corro~ion resistance ~15 can be obtained in a relatively low cost according to the present invention and it can be expected that these compo-sites can be very advantageously used in many fields where use must be made under severe conditions, such as super high temperature, super high pressure and corrosive atmosphere. -For example, these composites can be used for various crucibles, various nozzles, turbine blades, engine con-stituting materials, wear resistant parts, heat resistant materials, aircraft materials and the like.
,
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for producing fiber composites consisting of continuous silicon carbide fibers and silicon, which comprises filling spaces in a pile of high strength continuous silicon carbide fibers with fused silicon to tightly adhere said fiber pile and silicon.
2. The method as claimed in claim 1, wherein a content of the silicon in the fiber composite is 5-35% by weight.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP50127380A JPS5252122A (en) | 1975-10-24 | 1975-10-24 | Process for producing composite consisting of silicon carbide filament and metallic silicon |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1077969A true CA1077969A (en) | 1980-05-20 |
Family
ID=14958545
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA264,032A Expired CA1077969A (en) | 1975-10-24 | 1976-10-25 | Method for producing a composite consisting of continuous silicon carbide fibers and metallic silicon |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5252122A (en) |
| CA (1) | CA1077969A (en) |
| DE (1) | DE2647862C3 (en) |
| FR (1) | FR2347463A1 (en) |
| GB (1) | GB1562504A (en) |
| IT (1) | IT1069056B (en) |
| SE (1) | SE429549B (en) |
| SU (1) | SU680639A3 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1158259A (en) * | 1980-07-17 | 1983-12-06 | Francis J. Frechette | Composite material of silicon carbide and silicon and methods of producing |
| JPS63297277A (en) * | 1987-05-29 | 1988-12-05 | Tokai Kounetsu Kogyo Kk | Sic whisker-reinforced metallic composite material and production thereof |
| DE102015104943A1 (en) * | 2015-03-31 | 2016-10-06 | Universität Paderborn | Process for producing a nano- or microstructured foam |
-
1975
- 1975-10-24 JP JP50127380A patent/JPS5252122A/en active Granted
-
1976
- 1976-10-21 GB GB4365376A patent/GB1562504A/en not_active Expired
- 1976-10-22 SU SU762415457A patent/SU680639A3/en active
- 1976-10-22 DE DE19762647862 patent/DE2647862C3/en not_active Expired
- 1976-10-22 SE SE7611744A patent/SE429549B/en not_active IP Right Cessation
- 1976-10-22 FR FR7631920A patent/FR2347463A1/en active Granted
- 1976-10-22 IT IT5184676A patent/IT1069056B/en active
- 1976-10-25 CA CA264,032A patent/CA1077969A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE2647862B2 (en) | 1978-07-20 |
| SU680639A3 (en) | 1979-08-15 |
| SE429549B (en) | 1983-09-12 |
| FR2347463A1 (en) | 1977-11-04 |
| GB1562504A (en) | 1980-03-12 |
| DE2647862A1 (en) | 1977-09-08 |
| SE7611744L (en) | 1977-04-25 |
| JPS5549034B2 (en) | 1980-12-09 |
| DE2647862C3 (en) | 1979-03-22 |
| JPS5252122A (en) | 1977-04-26 |
| FR2347463B1 (en) | 1979-09-28 |
| IT1069056B (en) | 1985-03-25 |
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