JP2009190950A - Silicon carbide composite material and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new silicon carbide composite material well reduced of its porosity and having enough strength. <P>SOLUTION: This silicon carbide composite material is produced by forming a silicon carbide-carbon molding, impregnating the molding with molten silicon to form a silicon-impregnated silicon carbide-carbon molding and sintering the silicon-impregnated silicon carbide-carbon molding in a non-oxidizing atmosphere, so as to compose the silicon carbide composite material including three phases of silicon carbide, silicon and silicon dioxide, where the silicon exists continuously in a network form. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel material having excellent strength and corrosion resistance and high elastic modulus, and can be used for many applications as a heat shock material, a mechanical shock material, a heat resistant material, a corrosion resistant material, etc. Is to provide.

  Since silicon carbide is excellent in oxidation resistance and heat resistance, it is used as a heat-resistant material for atmospheric furnaces, and it is expected that the range of use will be expanded if the properties are further improved. In particular, when nitrides, carbides, and borides are added, the mechanical properties of the obtained composite material can be greatly improved, and application to the fields of aircraft-related parts and gas turbine parts is expected.

  Originally, a silicon carbide-silicon composite material and a silicon carbide-silicon dioxide composite material are manufactured using techniques such as a reaction sintering method and a liquid phase sintering method. For example, in the reactive sintering method, a silicon carbide-silicon composite material is manufactured by sintering a mixture of carbon powder and silicon powder and reacting the elements with each other. However, in such a conventional manufacturing method, volume shrinkage occurs during the sintering process, and pores are generated at a relatively large rate. For this reason, the obtained silicon carbide-silicon composite material does not have sufficient strength.

In view of this point, Japanese Patent Application Laid-Open No. 2001-226174 discloses that silicon carbide-silicon composite material is manufactured by impregnating molten Si into pores of silicon carbide generated by reactive sintering. However, such a method has a problem that the manufacturing process becomes complicated because it involves two steps of sintering and impregnation. Furthermore, when the pore diameter of the silicon carbide is sufficiently small, impregnation with molten Si becomes difficult, and when the pore does not penetrate the surface, impregnation with molten Si cannot be performed. Therefore, even in the method as described above, the residual porosity rate is relatively large, and a silicon carbide material having sufficient strength cannot be provided.
JP 2001-226174 A

  In view of the above problems, an object of the present invention is to provide a novel silicon carbide composite material having a sufficiently reduced porosity and sufficient strength.

In order to solve the above object, one embodiment of the present invention provides:
The present invention relates to a silicon carbide composite material comprising three phases of silicon carbide, silicon, and silicon dioxide, wherein the silicon is continuously present in a network, and a method for producing the same.

  The inventors of the present invention have intensively studied to achieve the above object. As a result, the mixed powder of silicon carbide and carbon is subjected to a chemical reaction treatment by controlling the atmosphere, thereby comprising three phases of silicon carbide, silicon, and silicon dioxide, and the silicon appears to be continuously present in a network. Has been found to be able to produce complex composite materials. And it has been found that according to this composite material, the porosity is sufficiently low due to its structure, and therefore it has a sufficiently high strength.

  Therefore, according to the present invention, the corrosion resistance, the elastic modulus, the thermal shock resistance, the mechanical shock resistance, and the heat resistance are excellent due to the sufficiently low porosity and the inherent characteristics. A silicon carbide composite material and a method for producing the same can be provided.

  Hereinafter, other features and advantages of the present invention will be described based on the best mode for carrying out the invention.

(Silicon carbide composite material)
As described above, the silicon carbide composite material of the present invention includes three phases of silicon carbide, silicon, and silicon dioxide, and the silicon exists continuously in a network. When the silicon carbide composite material has such a composition and structure, the internal pores are sufficiently reduced. The “network state” here is defined to mean the following. That is, when the X-axis, Y-axis, and Z-axis are virtually set as three-dimensional coordinates in the silicon carbide composite material of the present invention, silicon is continuously uninterrupted in both the X-axis direction and the Y-axis direction. Furthermore, it means that the Z-axis direction is also connected, in other words, it is continuous in a so-called mesh shape.

  In the silicon carbide composite material, it is preferable that at least a part of the silicon dioxide exists as a surface layer. By adopting such a configuration, it is possible to reduce the porosity of the silicon carbide composite material, in particular, the ratio of the porosity opened to the surface, and to suppress the internal entry of corrosive substances through the pores, and its corrosion resistance Can be further improved.

  For the same purpose, the thickness of the surface layer containing silicon dioxide is preferably 0.01 μm or more and 300 μm or less.

  Furthermore, it is preferable that the volume ratios of the silicon carbide, the silicon, and the silicon dioxide are 55 to 90%, 8 to 40%, and 0.1 to 5%, respectively. Thereby, the silicon carbide composite material having the above-described configuration can be obtained, and the porosity can be further reduced to increase its strength.

  For the same purpose, the amount of impurities contained in the silicon carbide composite material is preferably 10 ppm or more and less than 5%. Further, the particle size of the silicon carbide is preferably 0.1 μm or more and 10 μm or less.

  When the silicon carbide composite material has the configuration and characteristics described above, the porosity can be reduced to a range of 0.01% or more and less than 2%. In particular, the porosity of the surface layer containing the silicon dioxide can be reduced to a range of 0.01% or more and less than 2%. Such a silicon carbide composite material having a low porosity has not been obtained by the prior art, and has been realized for the first time in the present invention. Therefore, it has a sufficiently high strength as compared with a conventional silicon carbide composite material or the like.

  Furthermore, since the silicon carbide composite material of the present invention has a particularly small proportion of pores that are open on the surface, in addition to its inherent properties, it can effectively suppress the intrusion of corrosive substances and exhibits high corrosion resistance. Will be able to.

(Method for producing silicon carbide composite material)
Although the manufacturing method of the silicon carbide composite material of the structure and composition as mentioned above is not specifically limited, For example, it can form by the following methods.

  First, silicon carbide powder and carbon powder are prepared, mixed and granulated, and then formed into a predetermined shape using a CIP method or the like. Next, the obtained molded body is impregnated with molten silicon. Next, the impregnated molded body thus obtained is sintered in a non-oxidizing atmosphere such as an inert gas atmosphere or a vacuum atmosphere. Then, silicon carbide is produced by the reaction between silicon carbide and oxygen constituting the molded body, oxygen present in a minute amount in the carbon, and oxygen remaining in a minute amount in the atmosphere and the silicon.

  On the other hand, in the above sintering process, the impregnated silicon melts and enters into the cavities (pores) of the molded body in the sintering process. Therefore, the obtained sintered body includes three phases of silicon carbide, silicon, and silicon dioxide, and the silicon continuously exists in a network form. As a result, the above-described silicon carbide composite material of the present invention can be obtained.

  The silicon dioxide is formed near the surface due to the reaction process described above, and in particular, a surface layer containing a relatively large amount of the silicon dioxide is formed. Therefore, as described above, the silicon carbide that can reduce the ratio of the porosity particularly open to the surface, suppress the internal entry of the corrosive substance through the pores, and can further improve the corrosion resistance. A composite material can be provided.

  Further, in order to cause the reaction as described above, the sintering temperature is preferably set to 1400 ° C to 1800 ° C.

  In addition, the sintered body manufactured as described above can be appropriately machined in order to obtain a component or member for a target application, and further appropriately removed in order to remove strain caused by the machining. Annealing treatment or the like can be performed.

(Use of silicon carbide composite materials)
The silicon carbide composite material of the present invention is excellent in corrosion resistance, elastic modulus, thermal shock resistance, mechanical shock resistance, and heat resistance due to its low porosity and its inherent characteristics. Therefore, it can be applied to various uses having such characteristics. For example, it can be used for heat exchanger members for chemical plants, mirror surface members, mirror surface structural members, semiconductor manufacturing equipment parts, mechanical seal parts, sliding parts, gas turbine parts and decorative articles.

  Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.

(Examples 1-12)
(1) Raw material In the present Example, it tested using each component powder of silicon carbide, carbon, and silicon so that the sintered compact of the material composition ratio shown in Table 1 may be obtained.
(2) Method First, after mixing and granulating each component powder of silicon carbide and carbon having various average particle diameters shown in Table 1, a predetermined shape is obtained using a cold isostatic pressing method (CIP). Molded into. Next, the obtained molded body is impregnated with molten silicon, heated to 1400 to 1800 ° C. under reduced pressure or in an argon gas atmosphere, and subjected to reactive sintering for 1 hour. Obtained. This sintered body was processed into various test pieces shown below, and then annealed in the atmosphere. In addition, it shows in Table 1 regarding the characteristic of the obtained test piece.
(3) Evaluation Three-point bending strength test method defined in JIS R1601, high-temperature three-point bending test method defined in JIS R1604, thermal shock test method defined in JIS R1648, respectively, for room temperature strength, high temperature strength, thermal shock resistance, and corrosion resistance. And the corrosion test method defined in JIS R1614. Regarding each measured value of the obtained test piece, the value is shown in Tables 1 and 2.

(Comparative Examples 1-3)
In this comparative example, the amount of molten silicon to be impregnated in the above-described example was reduced, and a test piece was obtained through the same method as described above. It shows in Table 2 regarding the characteristic of the obtained test piece. Also, each evaluation value obtained through a test similar to the example is also shown in Table 2.

  As apparent from Table 1, the test pieces according to Examples 1 to 12 obtained according to the present invention include three phases of silicon carbide, silicon, and silicon dioxide, and the silicon is present continuously in a network. As a result, it can be seen that all exhibit a porosity of less than 2% and exhibit high evaluation values, that is, strength, high-temperature strength, thermal shock resistance, and corrosion resistance.

  On the other hand, unlike the present invention, in Comparative Examples 1 to 3 in which silicon is not formed in a network shape or contains no silicon, each evaluation value of the test piece, that is, strength, high temperature strength, thermal shock resistance, corrosion resistance In any case, it can be seen that the test pieces shown in the above examples are inferior. Therefore, it can be seen that the silicon carbide composite material of the present invention is excellent in various properties such as corrosion resistance, elastic modulus, thermal shock resistance, and heat resistance.

  As mentioned above, the present invention has been described in detail based on the best mode for carrying out the invention by showing specific examples. However, the present invention is not limited to the above contents, and unless it departs from the scope of the present invention. Any modification or change is possible.

Claims (17)

A silicon carbide composite material comprising three phases of silicon carbide, silicon, and silicon dioxide, wherein the silicon is continuously present in a network form.   The silicon carbide composite material according to claim 1, wherein at least a part of the silicon dioxide is present as a surface layer.   The silicon carbide composite material according to claim 2, wherein a thickness of the surface layer containing the silicon dioxide is 10 nm or more and 300 μm or less.   The silicon carbide composite material according to any one of claims 1 to 3, wherein the impurity amount is 10 ppm or more and less than 5%.   The volume ratio of the silicon carbide, the silicon, and the silicon dioxide is 55 to 90%, 8 to 40%, and 0.1 to 5%, respectively. The silicon carbide composite material described in 1.   6. The silicon carbide composite material according to claim 1, wherein the silicon carbide has a particle size of 0.1 μm or more and 10 μm or less.   The silicon carbide composite material according to any one of claims 1 to 6, wherein the porosity is 0.01% or more and less than 2%.   The silicon carbide composite material according to any one of claims 2 to 7, wherein the porosity of the surface layer containing the silicon dioxide is 0.01% or more and less than 2%.   A heat exchanger member for a chemical plant, comprising the silicon carbide composite material according to any one of claims 1 to 8.   The mirror surface member characterized by including the silicon carbide composite material as described in any one of Claims 1-8.   The mirror surface structural member characterized by including the silicon carbide composite material as described in any one of Claims 1-8.   A semiconductor manufacturing apparatus component comprising the silicon carbide composite material according to claim 1.   A mechanical seal component comprising the silicon carbide composite material according to claim 1.   A sliding component comprising the silicon carbide composite material according to claim 1.   A gas turbine component comprising the silicon carbide composite material according to claim 1.   A decorative article comprising the silicon carbide composite material according to claim 1. Forming a silicon carbide-carbon molded body comprising silicon carbide and carbon;
Impregnating the silicon carbide-carbon molded body with molten silicon to form a silicon-impregnated silicon carbide-carbon molded body;
The silicon-impregnated silicon carbide-carbon molded body is sintered in a non-oxidizing atmosphere to form a silicon carbide composite material containing three phases of silicon carbide, silicon, and silicon dioxide, and wherein the silicon is continuously present in a network form. And a process of
A method for producing a silicon carbide composite material, comprising: