JP2012211071A - METHOD FOR MANUFACTURING Si-SiC COMPOSITE MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Si-SiC composite material having sufficiently high strength at high temperature, in a low cost.SOLUTION: The Si-SiC composite material is manufactured by the following procedure: an SiC molded body and metal Si are arranged in such a way that metal Si melted by heating comes in contact with the SiC molded body, the metal Si is heat-treated at 1,400-1,800°C in an Ar gas atmosphere under ordinary pressure in a coexistence state with a mixture containing a readily oxidizable metal (e.g., metal Al) comprising an element having a larger negative absolute value of the standard free energy of oxide than that of Si, and the SiC molded body is impregnated with the metal Si melted by the heat treatment.

Description

  The present invention relates to a method for producing a Si—SiC composite material.

  Si-SiC based composite materials are known as high thermal conductivity, high strength at high temperatures, excellent oxidation resistance, and lightweight materials. As a method for producing this Si-SiC composite material, the following three methods are roughly classified. For example, a SiC porous sintered body obtained by recrystallizing and sintering SiC powder is impregnated with molten Si (Patent Document 1), and a porous sintered body obtained by sintering a mixture of SiC and carbon black is melted with Si. (Patent Document 2), a molded body made of a mixture of SiC and carbon black was impregnated with molten Si and reacted with Si and carbon to form SiC, and the SiC material as a whole did not react with carbon Examples include a method of impregnating Si (Patent Document 3).

Here, a SiO ₂ layer is formed on the surface of the SiC powder, and this SiO ₂ layer has poor wettability with the metal Si and prevents the metal Si from being impregnated into the shaped body of the SiC powder. In Patent Documents 1 and 2, a SiC sintered body obtained by sintering a sintered SiC powder is impregnated with molten Si, but the SiO ₂ layer is removed simultaneously with the sintering. It becomes easy to impregnate with molten Si. In Patent Document 3, by impregnating the metal Si at a high temperature of 2000 ° C. or higher in the molded body made of SiC and carbon, and removing the SiO ₂ layer.

  On the other hand, a material in which a SiC fired body is impregnated with a molten metal composed of Si and Al is also disclosed (Patent Document 4, particularly Example 2). When SiC is impregnated with only Si, volume expansion occurs when molten Si solidifies. Therefore, Si may be ejected from the surface of the sintered body, but by adding Al, volume shrinkage occurs when Al solidifies. Therefore, the molten metal is prevented from being ejected.

Japanese Patent Publication No.54-10825 Japanese Patent Laid-Open No. 2000-103677 JP-A-56-129684 Special table 2003-505329 gazette

  However, in Patent Documents 1 and 2, when an SiC sintered body is obtained by sintering an SiC compact, the SiC sintered body is impregnated with metal Si, so that the SiC compact is impregnated with metal Si. In comparison, there are problems that man-hours are large and costs are high. In Patent Document 3, the SiC compact is impregnated with metal Si. However, since it is necessary to perform the treatment at a high temperature of 2000 ° C. or higher, there is a problem that the energy consumption is large and the cost is increased. Further, in Patent Document 4, since the impregnation can be performed at a relatively low temperature, the cost is not so high. However, since a material containing about 50% by weight of Si and about 50% by weight of Al is used as the penetrating material, it is obtained. It is considered that the strength at high temperature of the Si-SiC based composite material is remarkably lowered.

  The present invention has been made to solve such problems, and it is a main object of the present invention to provide a Si—SiC composite material that is inexpensive and sufficiently high in strength at high temperatures.

  The manufacturing method of the Si—SiC based composite material of the present invention employs the following means in order to achieve the main object described above.

  That is, in the method for producing a Si—SiC composite material according to the present invention, metal Si and a SiC molded body are arranged so that Si melted after heating comes into contact with the SiC molded body, and the standard free energy of formation of the oxide is negative. In a state where an oxidizable metal composed of an element whose absolute value is larger than Si or a mixture containing the same coexisted, heat treatment is performed at 1400 to 1800 ° C. in an inert gas atmosphere under normal pressure to obtain molten metal Si. Is impregnated into the SiC molded body.

In this manufacturing method, when heat treatment is performed in an inert gas atmosphere under normal pressure, the SiO ₂ layer formed on the surface of the SiC powder constituting the SiC molded body volatilizes from the SiC molded body as SiO gas. In addition, the oxidizable metal takes away the oxygen element of the SiO gas, Si and an oxide of the oxidizable metal are generated, and the SiO gas in the system is reduced. It is thought that volatilization of is promoted. As a result, the SiC molded body is almost free of SiO ₂ , so that the metal Si easily impregnates the SiC molded body even under normal pressure, and a Si—SiC based composite material is generated. Further, since the SiO ₂ layer is formed on the surface of the metallic Si, since the SiO ₂ layer formed on the surface of the metal Si volatilized similarly, metal Si also in a state containing little SiO _2, Metal Si is more easily impregnated into the SiC molded body.

  According to this manufacturing method, since the SiC molded body is impregnated with metal Si, the SiC molded body is sintered to obtain a SiC sintered body, and then compared with the case where the SiC sintered body is impregnated with metal Si. Less man-hours and costs. Further, since the impregnation of metal Si is performed at 1400 to 1800 ° C., energy consumption is small and cost is not required as compared with the case where it is performed at 2000 ° C. or higher. Furthermore, when impregnating metal Si, since a large amount of metal components other than Si are not impregnated, the strength of the obtained Si—SiC composite material at high temperature does not decrease. Furthermore, since this manufacturing method impregnates the SiC molded body with metal Si without sintering the SiC molded body, after obtaining the SiC sintered body by sintering the SiC molded body, Compared with the case where metal Si is impregnated, the dimensional change from the SiC molded body to the Si-SiC composite material is small because there is no shrinkage accompanying the sintering of the SiC molded body. Therefore, if the final product dimensions are finished at the stage of the porous and easy-to-process SiC molded body, the finishing process at the stage of the dense, hard and difficult to process Si-SiC composite material after impregnation is reduced, or Can be eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a layout view of SiC molded bodies and the like in Example 1, (a) is a plan view, and (b) is an AA cross-sectional view. 6 is a plan view illustrating an arrangement of SiC molded bodies and the like in Example 3. FIG. 10 is a plan view illustrating an arrangement of SiC molded bodies and the like in Example 8. FIG. It is arrangement | positioning figures, such as a SiC molded object in the comparative example 1, (a) is a top view, (b) is BB sectional drawing.

  In the method for producing a Si-SiC composite material of the present invention, the metal Si and the SiC molded body are arranged so that the molten Si after heating is in contact with the SiC molded body. In a state where an easily oxidizable metal composed of an element having a value larger than Si or a mixture containing the same coexisted, heat treatment is performed at 1400 to 1800 ° C. in an inert gas atmosphere under normal pressure, whereby the molten metal Si is The SiC molded body is impregnated.

  In the production method of the present invention, the SiC compact may be a mixture of two or more types of SiC particles having different average particle diameters, or may be one obtained by molding SiC particles having one average particle diameter. What is necessary is just to set an average particle diameter suitably in the range of 2-500 micrometers, for example. The SiC molded body may contain carbon, a binder, or the like. In addition, a binder well-known in this field | area can be used. It is preferable to degrease the SiC molded body containing the binder in a nitrogen atmosphere or an air atmosphere. The shape of such a SiC molded body is not particularly limited. For example, various shapes such as a solid solid columnar body, a hollow columnar body, a cylindrical body, a spherical shape, a circular plate, and a polygonal plate are used. Can do. Considering the ease of impregnation with metal Si, it is preferable that a large number of holes are formed, for example, a honeycomb structure is preferable.

In the manufacturing method of the present invention, the metal Si may be formed by molding Si metal powder into a predetermined shape, or may be an Si ingot. As a method for forming the Si metal powder, uniaxial press, CIP, extrusion and the like are applicable, and dry uniaxial press and dry CIP are preferable. The Si ingot is a lump before being pulverized to produce a Si metal powder, and has a smaller surface area and less oxidation than the Si metal powder, and thus has a lower SiO ₂ content than the Si metal powder. Since the smaller the amount of SiO ₂ contained in the metal Si, the easier it is to impregnate the SiC molded body, it is preferable to use an Si ingot as the metal Si. The Si ingot preferably has an oxygen content of 0.1% by weight or less. The weight of the metal Si can be set according to the amount to be filled in the voids inside the SiC compact, and when it is made dense, it is sufficient to dispose more Si than is necessary for filling the gap. Although there is no restriction | limiting in particular in the shape of metal Si, The shape which can arrange | position metal Si in contact on a SiC molded object is more preferable. Metal Si should just be arrange | positioned so that Si fuse | melted after a heating may contact with a SiC molded object, and does not necessarily need to be in contact in the stage before a heating. The metal Si may be directly placed on the SiC molded body, or the metal Si may be floated using a jig before heating, and the molten Si may contact the SiC molded body during heating. Moreover, you may put metal Si in the state contacted beside or under the SiC molded object.

In the production method of the present invention, elements whose negative absolute value of standard free energy of formation of oxide is larger than Si are, for example, Al, Zr, Ti, Group 2 elements (Be, Mg, Ca, Sr, Ba, etc.) And one or more elements selected from the group consisting of rare earth elements (Y, Ce, La, Yb, etc.). When heat treatment is performed in an inert gas atmosphere under normal pressure without coexistence of an easily oxidizable metal, SiO ₂ volatilizes from the SiC molded body or metal Si as SiO gas. Is not reached. When heat treatment was performed in the presence of an easily oxidizable metal, the oxygen element of the volatilized SiO gas was taken away by the easily oxidizable metal, Si and an oxide of the easily oxidizable metal were generated, and the SiO gas in the system was reduced. Along with this, volatilization of SiO gas from the SiC molded body and metal Si is further promoted. As a result, the SiC molded body and the metal Si are almost free of SiO ₂ , so that the metal Si easily impregnates the SiC molded body even under normal pressure. As the easily oxidizable metal, Al, Zr, Ti, and Mg are preferable. Here, Mg may be scattered as a gas at the temperature during the heat treatment or cause a gas phase reaction. Al also has such a fear, but it is not as much as Mg, so Al is preferable to Mg. Zr and Ti maintain a liquid state at the temperature during the heat treatment, and there is no fear of scattering like Mg. Therefore, Zr and Ti are more preferable than Mg. Zr and Ti are also preferable in this respect because they are difficult to be mixed into the sintered body, but are not preferable in terms of cost because they are expensive. The amount of the easily oxidizable metal is preferably an amount that reacts with oxygen contained in the Si and SiC raw materials and the atmosphere. The form of the easily oxidizable metal is preferable because the powder has a larger surface area and easily deprives the SiO gas, but a lump, plate, or foil may be used. Moreover, only an easily oxidizable metal may be arrange | positioned and the mixture containing an easily oxidizable metal may be arrange | positioned.

In the production method of the present invention, the metal Si, the SiC molded body, and the oxidizable metal are allowed to coexist. As a coexistence method, the effect of the present invention can be obtained by arranging the SiC molded body and the easily oxidizable metal in the same furnace. In order to enhance the effect of the present invention, it is more preferable to place the SiC compact and the oxidizable metal in the same sheath and cover the sheath. This is because the oxygen supply from the outside is more restricted in the sealed space, and the easily oxidizable metal more easily takes the oxygen element from the SiC molded body or metal Si. Further, it is more preferable to dispose an easily oxidizable metal so as to surround the SiC molded body. As a specific arrangement method, for example, an oxidizable metal may be arranged at approximately equal intervals at two or more places around the SiC molded body, or it may be easy to surround the SiC molded body. You may arrange | position the ring-shaped molded object containing an oxidizable metal. When placing the oxidizable metal in only one place around the SiC molded body, SiC compacts and metal Si are SiO ₂ tends to escape from the portion facing the oxidizable metal, but easily oxidizable metal It may be difficult for SiO ₂ to escape from a portion that does not face. If an easily oxidizable metal is disposed so as to surround the SiC molded body, SiO ₂ can easily escape from the entire SiC molded body and metal Si, and the entire SiC molded body can be easily impregnated with metal Si uniformly. The best coexistence method is to place an easily oxidizable metal in the same sheath so as to surround the SiC molded body and the SiC molded body, and to cover the sheath.

In the production method of the present invention, when the oxidizable metal is arranged around the SiC molded body, the oxidizable metal or a mixture containing the oxidizable metal or a mixture containing the oxidizable metal or a mixture containing the oxidizable metal and It is preferable to arrange a molded body containing aggregate. When the easily oxidizable metal is disposed alone, the easily oxidizable metal may melt and flow toward the SiC molded body during the heat treatment, and may come into contact with the SiC molded body. However, when an easily oxidizable metal or a mixture containing the same is disposed on the base, the melt of the easily oxidizable metal remains on the base, and therefore the molten oxidizable metal may come into contact with the SiC molded body. There is no. In particular, when a porous body is used as the base, a melt of easily oxidizable metal permeates into the base, which is more preferable. In addition, when a molded body including an easily oxidizable metal and an aggregate is disposed, the aggregate maintains the skeleton of the molded body and prevents the molten metal of the easily oxidizable metal from flowing out. There is no possibility that the molten metal comes into contact with the SiC molded body. Examples of the material for the base and aggregate include carbon and ceramic (SiC, Al ₂ O _3, etc.). The average particle diameter of the aggregate is preferably 1 to 300 μm, and the ratio of the aggregate in the molded body containing the oxidizable metal and the aggregate is preferably 40 to 95% by volume ratio.

In the production method of the present invention, the normal pressure refers to a pressure when neither depressurizing nor pressurizing, and a pressure equal to atmospheric pressure (approximately 1 atm). Moreover, an inert gas means noble gases, such as argon and helium, and does not contain nitrogen gas. The oxygen partial pressure is preferably about the oxygen partial pressure of an inert gas that is generally available and available (for example, 10 ⁻⁴ atm or less). However, if the oxygen concentration is high, the oxidizable metal may be increased.

In the production method of the present invention, when Al is used as the easily oxidizable metal, an alumina reaction product is formed around the green compact after impregnation. There are various shapes such as fiber, whisker, plate, and lump, but fiber or whisker-like reaction products are not preferable from the viewpoint of work safety. Therefore, when Al is used, it is preferable to add an auxiliary agent for the purpose of controlling the form of the reaction product. By adding an auxiliary agent, the formation of a fiber-like or whisker-like reaction product is suppressed, and a lump-like product is easily formed, thereby improving work safety. The element constituting the auxiliary agent may be any element that reacts with Al ₂ O ₃ to have a low melting point and hardly reacts with metal Si or Al. For example, alkaline earth metals such as Ca, Sr, and Ba preferable. The auxiliary agent is preferably an alkaline earth metal salt from the viewpoint of ease of handling, of which carbonate is more preferable, and CaCO ₃ is particularly preferable. The amount of auxiliary agent added is preferably from 1 to 3 times by weight with respect to Al.

In the production method of the present invention, the temperature during the heat treatment is set to 1400 to 1800 ° C. because sintering of the SiC molded body and impregnation with metal Si proceed simultaneously within this temperature range. Such heat treatment is performed by, for example, arranging a SiC molded body in which metal Si is placed in a sheath, placing an easily oxidizable metal around the sheath, closing the lid, and covering the sheath with a carbon furnace or furnace in which the furnace material is made of carbon. The material is placed in an oxide furnace (such as an alumina furnace) made of an oxide. For the sheath and the lid, for example, those made of oxide (such as alumina) are used. Further, it is preferable to lay oxide powder (alumina powder or the like) on the bottom surface of the sheath. If it carries out like this, Si-SiC type composite material can be taken out easily after completion | finish of heat processing. The firing step includes three steps of a temperature raising step, a maximum temperature holding step, and a temperature lowering step. In the temperature raising step, a step of holding at a predetermined temperature for removing SiO ₂ may be added. The temperature increase / decrease rate may be set in consideration of the ability of the furnace to be used, suppression of uneven temperature distribution in the furnace, and prevention of cracking of the sheath used. The temperature of the maximum temperature holding step is preferably 1400 to 1800 ° C., and the holding time is preferably 1 to 20 hours. However, since it depends on the size and shape of the molded body, the amount of easily oxidizable metal to be coexisted, etc. It is desirable to set it by conducting experiments etc. as appropriate.

  The production method of the present invention is suitable for obtaining a Si—SiC composite material in which SiC is 57 to 85% by weight, Si is 14.4 to 43% by weight, and Al is 0.6% by weight or less. Moreover, it is suitable for obtaining a Si—SiC composite material having an open porosity of 0 to 5%, a thermal conductivity of 130 to 170 W / mK, a room temperature strength of 200 to 250 MPa, and a strength at 1000 ° C. of 180 to 230 MPa. Yes.

[Example 1]
70% by weight of SiC powder with an average particle size of 45 μm, 10% by weight of SiC powder with an average particle size of 35 μm, 20% by weight of SiC powder with an average particle size of 5 μm, and 4% by weight of binder (that is, 100 parts by weight of SiC powder) 4 parts by weight) and water were mixed and kneaded using a kneader to obtain a kneaded product. This kneaded material was put into a vacuum kneader to produce a columnar clay. Next, a die having grid-like slits was attached to the extruder, and columnar clay was put into the extruder to produce a honeycomb formed body having a columnar shape and a plurality of cells. The honeycomb formed body had a total length of 20 mm, an outer diameter of 44 mm, an outer peripheral wall thickness of 2 mm, a partition wall thickness of 0.3 mm, and a cell density of 25 cells / cm ² . After drying this, degreasing was performed at 500 ° C. for 5 hours in a nitrogen atmosphere to obtain a SiC molded body (weight: about 20 g).

  The metal Si compact was weighed with Si powder (oxygen content of about 0.6% by weight) to 85 parts by weight with respect to 100 parts by weight of the SiC compact, and then uniaxially pressed into pellets with a diameter of 50 mm. Molded to produce.

  The green compact containing an easily oxidizable metal was weighed and mixed with Al powder and Si powder so that the weight ratio was Al: Si = 7: 3. 8.5 g).

Then, as shown in FIG. 1, 150 mm square, prepared sheath 10 is made of Al ₂ O ₃ container height 50 mm, lined with laid powder 12 (Al ₂ O ₃ powder) on the bottom. This spread powder 12 is for facilitating removal of the product after firing. A SiC compact 14 is placed in the center of the sheath 10, a metal Si compact 16 is placed thereon, and a green compact 18 containing an oxidizable metal is placed at the four corners of the sheath 10 so as to surround the periphery. One by one. In order to prevent the Al—Si molten metal from spreading into the sheath 10, SiC powder is formed into a pellet with a diameter of 30 mm by uniaxial pressing under the green compact 18 containing an easily oxidizable metal, and this pellet is the base. 20 was arranged. Thereafter, the sheath 10 is covered with an Al ₂ O ₃ lid, placed in a carbon furnace, and subjected to heat treatment at 1450 ° C. for 4 hours under normal pressure in an Ar atmosphere, thereby impregnating the SiC compact with metallic Si. The SiC molded body was sintered to obtain a honeycomb sintered body made of a Si-SiC composite material. The temperature rising rate was 200 ° C./h.

When the obtained honeycomb sintered body was cut and the impregnation state of metal Si was examined, it was impregnated uniformly. Further, the bulk density, porosity, Al content, Si content, SiC content, thermal conductivity and strength were measured. The measuring method is as follows. The measurement results are shown in Table 1. As is clear from Table 1, while maintaining the same thermal conductivity as that of Comparative Example 2 (details will be described later), the Al content can be reduced as compared with Comparative Example 2, and the decrease in material strength at high temperatures can be suppressed. I was able to.
(1) Bulk density: measured by Archimedes method.
(2) Porosity a: The sample was polished to remove irregularities, scratches and dirt, and then photographed at three arbitrary locations at a magnification of 50 times. When the density histogram of each image is created, each peak of pores, SiC, Al, and Si appears in order from the dark side. Therefore, the position of the valley between the pores and the peak of SiC is set as a threshold value to 2 in the pores and other parts. Priced. The porosity was calculated from the area ratio, and the average value at three locations was defined as the porosity.
(3) Porosity b: It was calculated using the bulk density according to Archimedes method and the true density measured by a density meter (manufactured by Shimadzu Corporation, dry automatic density meter Accupic 1330) by pulverizing the sample.
(4) Content of Al, Mg, Ti, Zr: measured by ICP emission spectroscopic analysis (based on JIS R 1616).
(5) Si, SiC content: When Al is used as the oxidizable metal, the bulk density, the porosity, the measured value of the Al content, and the literature value of the true density (Si: 2.33 g / cc, (SiC: 3.21 g / cc, Al: 2.7 g / cc) and assuming that the Si-SiC composite material is composed of only Si, SiC, Al, and pores, the content of Si and SiC is calculated. did. When Mg, Ti, or Zr was used as the easily oxidizable metal, the same calculation was performed. The literature values for true density are Mg: 1.7 g / cc, Ti: 4.5 g / cc, Zr: 6.5 g / cc.
(6) Thermal conductivity: The same material as that of the SiC molded body was extruded into a plate shape having a thickness of 2 mm or more, and a material impregnated by the same method as in Examples was measured by a laser flash method (based on JIS R 1611).
(7) Strength: The same material as the SiC molded body was extruded into a plate having a thickness of 3 mm or more, and impregnated by the same method as in the examples was measured by a four-point bending test (based on JIS R 1601 and JIS R 1604).

[Example 2]
Instead of using the green compact and base containing the easily oxidizable metal of Example 1, the Al powder and the SiC powder were weighed and mixed so that the weight ratio was Al: SiC = 1: 1, and then uniaxial press A green compact containing an easily oxidizable metal prepared by molding into a 30 mm diameter pellet (weight: about 9.7 g) was used. Since this green compact keeps the skeleton of the molded body even if Al is melted and prevents the molten Al from spreading into the sheath, no SiC pellets are placed underneath. Other conditions were the same as in Example 1. Also in this case, a honeycomb sintered body in which the metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results of the same parameters as in Example 1. As can be seen from Table 1, while maintaining the same thermal conductivity as that of Comparative Example 2, the Al content could be reduced as compared with Comparative Example 2, and a decrease in material strength at high temperatures could be suppressed.

[Example 3]
Instead of the green compact containing the oxidizable metal of Example 2, Al powder (weight: about 5 g), which is an oxidizable metal, was placed in an Al ₂ O ₃ boat having a width of 17 mm, a height of 12 mm, and a length of 102 mm. Two things were arrange | positioned so that the molded object for impregnation might be surrounded. Other conditions were the same as in Example 2. The layout at this time is shown in FIG. The reference numerals in FIG. 2 represent the same as those in the first embodiment. Also in this case, a honeycomb sintered body in which the metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results of the same parameters as in Example 1. As can be seen from Table 1, while maintaining the same thermal conductivity as that of Comparative Example 2, the Al content could be reduced as compared with Comparative Example 2, and a decrease in material strength at high temperatures could be suppressed.

[Example 4]
Instead of the metal Si molded body of Example 2, a Si lump (ingot) having an oxygen content of 0.1% by weight or less was weighed to be 85 parts by weight with respect to 100 parts by weight of the SiC molded body. Using. Other conditions were the same as in Example 2. Also in this case, a honeycomb sintered body in which the metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results of the same parameters as in Example 1. As can be seen from Table 1, while maintaining the same thermal conductivity as that of Comparative Example 2, the Al content could be reduced as compared with Comparative Example 2, and a decrease in material strength at high temperatures could be suppressed.

[Example 5]
The honeycomb formed body of Example 2 was degreased at 400 ° C. for 4 hours in an air atmosphere. Other conditions were the same as in Example 2. Also in this case, a honeycomb sintered body in which the metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results of the same parameters as in Example 1. As is clear from Table 1, a material having the same characteristics as in Example 2 was obtained even when the degreasing atmosphere condition was changed from nitrogen to air.

[Example 6]
The heat treatment in the carbon furnace of Example 2 was performed in an oxide furnace (alumina furnace) under normal pressure and in an Ar atmosphere at 1450 ° C. for 4 hours. Other conditions were the same as in Example 2. Also in this case, a honeycomb sintered body in which the metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results of the same parameters as in Example 1. As is clear from Table 1, a material having the same characteristics as in Example 2 was obtained even in the impregnation with an oxide furnace.

[Example 7]
After blending 87% by weight of SiC powder with an average particle size of 45 μm and 13% by weight of SiC powder with an average particle size of 35 μm, 4% by weight of binder and water, and rotation / revolution using a rotation / revolution mixer = 600 For about 4 minutes at 1800 rpm. After drying at 100 ° C. for 15 hours, the mixture was pulverized and passed through a 30 μm sieve to produce a raw material powder. This raw material powder was molded with a uniaxial press, then CIP-treated with 3 tons to produce a φ50 mm pellet, and degreased at 500 ° C. for 5 hours in a nitrogen atmosphere to obtain a SiC molded body (weight of about 32 g). The green compact containing an easily oxidizable metal was weighed and mixed with Mg powder and Si powder so that the weight ratio was Mg: Si = 77: 33, and then pellets having a diameter of 30 mm (weight: about 10 g) by uniaxial pressing. It was formed by molding. Then, one SiC molded body is placed on the opposite corner of the 150 mm square and 50 mm high Al ₂ O ₃ sheath, and the same metal Si molded body as in Example 1 is placed thereon, and the rest of the sheath One green compact containing an easily oxidizable metal was placed in two corners, and heat treatment was performed under the same conditions as in Example 1. Also in this case, a sintered body in which metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results of the same parameters as in Example 1. As is apparent from Table 1, even when Mg was used as the oxidizable metal, a material having the same characteristics as when Al was used as the oxidizable metal was obtained.

  In Example 7, the SiC molded body was in the form of a pellet instead of a honeycomb. However, even when the honeycomb shaped SiC molded body used in Example 1 was used, metal Si was completely impregnated. A honeycomb sintered body was obtained.

[Example 8]
In Example 2, one SiC molded body is placed at one corner of an Al ₂ O ₃ sheath of 150 mm square and 50 mm height, and a metal Si molded body is placed thereon, and the SiC molded body and the diagonal side One green compact formed so as to have a weight ratio of Al: SiC = 1: 1 was placed at the corner of the sheath. In addition, one green compact molded so as to have a weight ratio of Mg: Si = 77: 33 was placed in another sheath, and the sheath was not covered. The other conditions were the same as in Example 2. FIG. 3 shows a layout diagram of the eighth embodiment. Of the two sheaths, one sheath 10 is the same as that of the first embodiment, and therefore, the same reference numerals as those of the first embodiment are given and the description thereof is omitted. As for the other sheath 110, the spread powder 112 (Al ₂ O ₃ powder) was spread on the bottom surface, and the green compact 118 was arranged in the center thereof. Also in this case, a honeycomb sintered body in which the metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results for each parameter.

[Example 9]
Instead of using the green compact of Example 7, Ti powder and SiC powder were weighed and mixed so that the weight ratio of Ti: SiC = 1: 4, and then a 30 mm diameter pellet prepared by uniaxial pressing was used. Were heated in the same manner as in Example 7. Also in this case, a sintered body in which metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results for each parameter.

[Example 10]
Instead of the green compact of Example 7, Zr powder and SiC powder were weighed and mixed so that the weight ratio was Zr: SiC = 1: 4, and then pellets with a diameter of 30 mm prepared by uniaxial pressing were used. Were heated in the same manner as in Example 7. Also in this case, a sintered body in which metal Si was uniformly impregnated was obtained. Table 1 shows the measurement results for each parameter.

[Comparative Example 1]
In Example 1, one SiC compact was placed on a 150 mm square, 50 mm high Al ₂ O ₃ sheath, and a metal Si compact was placed thereon. No oxidizable metal was placed. The other conditions were the same as in Example 1. FIG. 4 shows a layout diagram of the first comparative example. Since the reference numerals are the same as those in the first embodiment, the description is omitted here. In this case, metal Si was not impregnated.

[Comparative Example 2]
A SiC molded body was produced in the same manner as in Example 1. Then, an impregnated metal molded body was produced instead of the oxidizable metal compact. That is, the impregnated metal formed body was weighed and mixed with Al and Si so that the weight ratio Si: Al = 9: 1, and then uniaxially pressed so as to be 85 parts by weight with respect to 100 parts by weight of the SiC formed body. An impregnated metal molded body was formed by forming into pellets having a diameter of 50 mm. Then, a SiC molded body is placed in the center of a 90 mm square, 50 mm high Al ₂ O ₃ sheath, and an impregnated metal molded body is placed thereon, in a carbon furnace at normal pressure in an Ar atmosphere at 1450 ° C. Impregnation was performed for 4 hours. In this case, the entire SiC molded body was impregnated with metal, but the metal contained about 10% by weight of Al, so that the strength was inferior to the products of the examples. Table 1 shows the measurement results of the same parameters as in Example 1. As is clear from Table 1, the Al content was higher than in Examples 1 to 7, and the strength reduction at high temperatures was remarkable.

[Example 11]
When Ti or Zr was used as the oxidizable metal (Examples 9 and 10), no fiber was observed around the green compact after impregnation, but when Al was used as the oxidizable metal (implementation) Examples 1 to 6, 8) Alumina fibers were generated around the green compact after impregnation. Such a fiber is not preferable from the viewpoint of work safety. Therefore, CaCO ₃ was added as an auxiliary agent to examine whether or not there was an effect of agglomerating the fiber. Specifically, a honeycomb sintered body was obtained in the same manner as in Example 1 except that instead of the pellets in Example 1, pellets containing CaCO ₃ were used. The pellet containing CaCO ₃ was produced as follows. That is, Al powder and SiC powder are weighed and mixed so that Al: SiC = 1: 4 by weight ratio, and then CaCO ₃ powder is added thereto so that Al: CaCO ₃ = 2: 5 by weight ratio. did. After the addition, the mixture was further mixed to produce a 30 mm diameter pellet (weight: about 14 g) by uniaxial pressing. Also in this case, a sintered body in which the metal Si was uniformly impregnated was obtained without inhibiting the impregnation. Furthermore, almost no alumina fiber was observed around the green compact after impregnation, and an aluminous mass was formed. This lump is thought to be agglomerated by the reaction of alumina fibers. Table 1 shows the measurement results for each parameter.

  The Si—SiC composite material obtained by the production method of the present invention can be used for parts such as automobiles, semiconductor production apparatuses, machine tools, and production facilities. For example, it can be used for heat exchange parts for exhaust heat recovery and cooling applications utilizing the characteristics of high heat conduction, and is not particularly limited to the automotive field, the industrial field, and the like. When used in the automobile field, a heat exchanger for exhaust heat recovery and an EGR cooler are considered as examples, and in this case, it can be used for improving the fuel consumption of the automobile and reducing NOx. In addition, it can be applied to kiln tools, etc. by taking advantage of high strength at high temperatures and excellent oxidation resistance.

10 pods, 12 spread powder, 14 SiC molded body, 16 metal Si molded body, 18 oxidizable metal green compact, 20 base, 110 pod, 112 spread powder, 118 oxidizable metal green compact.

Claims (10)

  The metal Si and the SiC molded body are arranged so that the molten Si after heating is in contact with the SiC molded body, or an easily oxidizable metal composed of an element whose negative absolute value of the standard free energy of formation of the oxide is larger than Si. Of Si-SiC composite material in which molten metal Si is impregnated into a SiC compact by heat treatment at 1400-1800 ° C. in an inert gas atmosphere under normal pressure in the presence of a mixture containing Method.   2. The method for producing a Si—SiC composite material according to claim 1, wherein the element is at least one element selected from the group consisting of Al, Zr, Ti, a Group 2 element, and a rare earth element.   The method for producing a Si-SiC composite material according to claim 1 or 2, wherein the element is Al, Zr, Ti, or Mg.   The method for producing a Si-SiC composite material according to any one of claims 1 to 3, wherein the SiC compact has a honeycomb structure.   The method for producing a Si-SiC composite material according to any one of claims 1 to 4, wherein the metal Si is a Si ingot.   The manufacturing method of the Si-SiC type composite material according to any one of claims 1 to 5, wherein a molded body containing the oxidizable metal and an aggregate is used as the mixture containing the oxidizable metal.   In coexistence of the metal Si, the SiC molded body, and the oxidizable metal or a mixture containing the same, the metal Si, the SiC molded body, and the oxidizable metal or a mixture including the same in the same sheath. The manufacturing method of the Si-SiC type composite material according to any one of claims 1 to 6, wherein the Si-SiC composite material is disposed and covered with a sheath.   The Si-SiC according to any one of claims 1 to 7, wherein the oxidizable metal is disposed so as to surround the SiC molded body when the SiC molded body and the oxidizable metal coexist. Method for manufacturing a composite material. As the mixture, a mixture containing an oxidizable metal composed of Al and a salt of an alkaline earth metal is used.
The manufacturing method of the Si-SiC type composite material of any one of Claims 1-8. The alkaline earth metal salt is carbonate;
The manufacturing method of the Si-SiC type composite material of Claim 9.

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