JPH03112900A - Production of ceramic form and raw material form for production thereof - Google Patents

Abstract

PURPOSE:To provide the title production method by CVD technique. so designed that a groove is provided so as to surround the joint between a raw material form and a support to mitigate the residual stress in a laminated ceramic film leading to prevention of the crack propagation therein. CONSTITUTION:A groove 16 is provided on a raw material form 10 so as to surround the joint between a support 12 and the raw material form 10. This raw material form 10 is then heated in a reaction furnace to laminate the raw material form 10 with a ceramic by CVD technique. Thence, the resulting ceramic film 18 laminated is separated from the raw material form 10, thus obtaining the objective ceramic form consisting of the ceramic film 18.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the production of a ceramic molded body by depositing a ceramic coating on a raw material body, and specifically relates to the production of a ceramic molded body formed by depositing a ceramic coating on a raw material body, and specifically relates to the production of a ceramic molded body formed by depositing a ceramic film on a raw material body. In the process of manufacturing ceramic molded bodies such as BN by chemical vapor phase reaction method (hereinafter referred to as CVD method), this is caused by the difference in coefficient of thermal expansion between the ceramic molded body deposited on the raw material body and the raw material body. The present invention relates to the production of a ceramic molded body using a raw material that can prevent scratches on the ceramic molded body and has excellent peelability between the ceramic molded body and the raw material.

[Prior Art] Ceramic molded bodies such as Sf, Si3N4, BN, etc. are industrial materials with excellent properties such as high melting point, inertness, high thermal stability, and high thermal conductivity, and are widely used in various fields. It is being It is widely known that such ceramic molded bodies can be manufactured by the CVD method using gas as a raw material.For example, BN is manufactured using boron halide gas and ammonia gas as raw materials, at a reaction temperature of 1450°C to 2300°C,
It can be produced by reacting at a pressure of 1 to 50 Torr.

Normally, when producing such a ceramic molded body by the CVD method, a device is used in which a vacuum reaction chamber heated by a heater or the like is installed in the vacuum chamber, and a material of a predetermined shape is placed inside the reaction chamber using a support. With the material supported and fixed and heated to a predetermined temperature, raw material gas is introduced into the reaction chamber through a nozzle, etc., and a ceramic layer (coating) is precipitated (deposited) on the material under a specific pressure. After that, the raw material is removed from the support, and the raw material and the ceramic coating deposited on the raw material are separated to obtain a ceramic molded body.

[Problems to be Solved by the Present Invention] At this time, in order to facilitate separation of the raw material and the ceramic molded body, a material having a coefficient of thermal expansion different from that of the ceramic to be precipitated is used as the raw material. When ceramics are precipitated by this method, they are deposited in the form of a ceramic film over the entire surface of the material and support, and the ceramic film covers the entire material rod.For this reason, after the deposition, the ceramic film is deposited on the material and the surface layer of the material. Residual stress exists in the ceramic coating because the stress in the ceramic coating due to the difference in thermal expansion coefficient with the (deposited) ceramic coating is relaxed. Due to this residual stress, cracks may appear in the ceramic *S during the cooling process after precipitation, or the ceramic film may be damaged during the cutting process during separation, which has been a manufacturing problem. In particular, since the deposition surface changes rapidly at the joint between the material and the support, the ceramic coating on the joint is prone to cracking due to concentration of stress due to strain energy, etc. As a result, cracks that enter the ceramic coating propagate over a wide area to the ceramic coating on the material.

This caused major damage to the ceramic coating, creating a major problem.

The purpose of the present invention is to alleviate the stress in the ceramic coating caused by the difference in thermal expansion coefficient between the material and the precipitated ceramic coating, and to prevent the propagation of cracks derived from the joint between the material and the support. It is an object of the present invention to provide a method for manufacturing a ceramic molded body and a material for manufacturing which can solve the above-mentioned problems by preventing.

[Means for Solving the Problems] In order to solve the above-mentioned problems and achieve the above-mentioned objectives, the present inventor conducted intensive research on the material used in the process of manufacturing ceramic molded bodies by the CVD method. As a result, by providing a groove in the material that surrounds the joint between the material and the support, it is possible to alleviate the residual stress in the ceramic coating deposited on the material, and to reduce the residual stress that is generated at the joint between the material and the support. The inventors have discovered that it is possible to prevent cracks from propagating over a wide range of ceramic coatings, leading to the present invention.

In the method for manufacturing a ceramic molded body according to the first embodiment #i of the present invention, a raw material gas is introduced into a reaction system in which a raw material is placed on a support using a nozzle, and then the raw material gas is deposited on the raw material by a CVD method. In the process of manufacturing a ceramic molded body by depositing a ceramic film on the material and then separating the material and the ceramic film, a ceramic film of a specific width and a specific depth is formed so as to surround the joint between the material and the support. Place the lecture on the material body.

Furthermore, in the method for manufacturing a boron nitride molded body according to the second embodiment of the present invention, the ceramic coating deposited on the material body in the first embodiment is formed of boron nitride.

Further, in the raw material for producing a ceramic molded body according to the third embodiment of the present invention, the gap surrounding the joint between the raw material and the support is at least 2.5 mm and no more than 3°5 mm, and has a depth of 1 mm.
It has a dimension of 5 mm or more and 25 mm or less.

[Function] The raw material for producing a ceramic molded body according to the present invention has a shape that matches the shape of the ceramic/yx molded body to be formed thereon. Therefore, if this material body is formed according to the shape of the molded body to be manufactured, by separating the ceramic coating formed by depositing ceramics,
A desired ceramic molded body is obtained.

The ceramic coating and the raw material are separated by cutting with a lathe along the cutting line on the side of the raw material away from the joint.

The distance between this cutting line and the joint is often shorter than the propagation distance of a crack generated at the joint, and for this reason, the ceramic molded bodies that are separated often have cracks. However, in the present invention, since a gap is provided between the cutting line and the joint, the propagation of cracks is stopped by this gap, and cracks are prevented from entering the ceramic molded body to be separated. . Specifically, when the ceramic is deposited, a discontinuous portion is created in the ceramic film due to cleaning, and the propagation of cracks is stopped here.

In this way, the grooves surrounding the joint prevent cracks from propagating to the ceramic molded body.
In order to obtain this effect, the width and depth of the gap must be within a certain range.In other words, for ceramics deposited by the CVD method, the width of the gap should be between 2.5 mm and 3.5 mm. This is because if the thickness is less than 2.5 mm, the grooves will be blocked by the ceramics deposited in the solution, and a discontinuous portion of the ceramic coating will not be obtained, so the desired effect of the present invention cannot be obtained. , 3.5mm
This is because if the grooves are bent, gas will flow into the grooves, and ceramics will accumulate in the grooves, making it impossible to obtain discontinuous portions of the ceramic coating, and thus making it impossible to prevent the propagation of cracks.

Furthermore, the depth of the groove should be 15 mm or more, because if it is less than 15 mm, ceramics will accumulate in the groove, and as in the case where the width is too small, discontinuous parts of the ceramic coating will be formed. This is so that you will not be affected. On the other hand, setting the depth of the clearing to 25 mm or less means that even if it exceeds 25 mm,
This is because although the effect remains the same, the manufacturing process of the material requires a large amount of labor, which is unreasonable from an economic standpoint.

[Example] Next, an example of the raw material for producing a ceramic molded body according to the present invention will be described with reference to the drawings.

In the embodiment shown in FIG. 1, a cylindrical material 10 is used, and in the case shown in FIG. Also, the material body 10 has a screw 6 that receives the tip of the support body 12, and is joined and supported by screwing. 4 The material body 10 shown is cylindrical, or the material body 10 is a mold to be manufactured. It can take various shapes to suit your body. Moreover, the materials of the support body 12 and the material body 10 can be selected from materials such as graphite according to needs.

At the point where the support 12 enters the material body 10, that is, at the joint 14, the surface changes rapidly, so the deposited ceramic film is susceptible to strain energy and cracks are likely to occur in the ceramic film. There is a risk that the particles may spread to the part where the ceramic molded body is separated. Therefore, in the case of the present invention, the material body 10 includes a groove 1 surrounding the joint portion 14.
6 is provided, and the groove width of eraser 16 is 2.5 mm or more and 3.5 mm.
mm or less, and the depth is 15 mm or more and 25 mm or less.

Regarding the position of the groove, the distance from the joint 14 to the groove 16 and the manner in which the joint 14 is surrounded can be varied depending on each case. However, the outer peripheral edge of the material 10 and the support 12
If there is a spring near the edge of the screw hole to insert the material 1
It should be noted that these edges are fragile during molding. Furthermore, if the blower 16 is placed on the cylindrical side surface of the material body 10, the blower 16 will be easily clogged with the products of the reaction gas, so the spring 16 should be placed on a flat surface with a screw hole into which the support 12 is inserted, as shown in the figure. It is good to have one.

When the material body 10 as described above is used and ceramics are deposited thereon by the CDV method, a ceramic coating 18 is formed over the entire material body 10 as shown in FIG. However, in the groove 16, no ceramic is deposited only in the recess, and the ceramic-covered pA 18 has a discontinuous portion there. For this purpose, the joint 14
It is possible to prevent cracks generated in the groove from propagating beyond the groove 16.

In addition, in order to emphasize the ceramic coating 18 in FIG.
The thickness of the ceramic coating 18 is shown exaggerated with respect to the size of the material body 10.

In this way, the ceramic coating 18 formed on the entire material body 10 is cut out from the material body 10 along a predetermined cutting line. When the ceramic coating 18 above and below the cutting line is separated, the coating 18 easily separates from the material 10 and becomes a molded body. In the case shown in FIG. 0, since the material 10 is cylindrical, the separated ceramic coating 18 is cylindrical. It becomes a crucible shape. Further, along the cylindrical side surface of the material body 10, two
If the annular cutting lines of the book are inserted, a tubular ceramic molded body can be obtained with the ceramic coating between these cutting lines.

Next, an example for determining the width and depth of the material body 10 will be described.

A cylindrical graphite reaction chamber installed in a resistance heating reactor (
A graphite material body 10 (diameter 96 mm, length 100 mm) is placed in the center of a support body 1 (inner diameter 120 mm, length 200 mm).
2, using a graphite nozzle (outer diameter 10 mm, inner diameter 8 mm) to inject boron trichloride gas and ammonia gas,
Introduced from below, reaction temperature 1900°C, pressure 2 Tor
The reaction was carried out under conditions of r for 15 hours, and boron nitride was deposited on the material body 10 as shown in FIG. The boron nitride coating formed by this deposition Il! A boron nitride molded body was obtained by separating 18 from the raw material 10. At this time, as shown in FIG.
A well 16 of various dimensions (width and depth) was provided at a radius of 20 rom around 4, and after the boron nitride molded body was taken out, the propagation state of the crack that occurred at the joint 14 surrounded by the clear 16 was investigated. Examined.

Table 1 shows the results when the width and depth were varied (width Amm, depth Bmm).

(Margins below this page) Table 1 As can be seen from Table 1, there is a specific dimension surrounding the joint 14 on the material body 10. It can be seen that by providing 1116, propagation of cracks generated at the joint 14 can be prevented.

That is, if the width of the dip 16 is less than 2.5 mm, the groove 16 will be blocked during manufacturing due to boron nitride deposition, and discontinuous portions of the boron nitride coating 18 will not be obtained, so that the desired effect of the present invention will not be achieved. On the other hand, if it exceeds 3.5 mm, gas will flow into the groove 16 and boron nitride will accumulate in the groove 16, making it impossible to obtain a discontinuous part of the boron nitride coating 18, resulting in cracks. It is not possible to prevent the transmission of feudal domains.

Therefore, the width of the groove 16 is preferably 2.5 mm or more and 3.5 mm or less.

Furthermore, if the depth of the clearing 16 is less than 15 mm, the clearing 16
If the width of the boron nitride coating 18 is too small, discontinuous portions of the boron nitride coating 18 will not be obtained.Conversely, even if the depth of the coating 16 exceeds 25 mm, the effect will not be obtained. Although there is no change, the manufacturing process of the material body 10 requires a large amount of labor, which is unreasonable from an economic point of view. Therefore, the depth of the groove 16 is preferably 15 mm or more and 25 mm or less.

It has been found that the specific dimensions of Eraser 16 can be applied to ceramics other than boron nitride.

Next, Examples 1 and 2 are shown together with comparative examples so that the present invention can be understood more clearly.

(Example 1) As shown in FIG. 1, a graphite cylindrical material lO with a diameter of 96 mm and a length of 100 mm has a width of 3 mm. Om, m, depth 20mm
A graphite rod-shaped support 12 with a diameter of 20 mm is provided.
The graphite material body 10 was supported by. Then, the graphite material 10 was fixed with a graphite support 12 in the center of a graphite cylindrical reaction chamber (inner diameter 120 mm, length 200 mm) installed in a resistance heating furnace. Boron trichloride gas and ammonia gas were introduced into this reaction chamber using a graphite nozzle, and the reaction temperature was 1900°C and the pressure was 2 T.
The reaction was carried out for 15 hours under the conditions of Orr to deposit boron nitride on the material body 10 to form a boron 9ide coating [18,
When the boron nitride coating 18 was taken out, the joint portion 14
The propagation of the crack that occurred at 7f416 was prevented. Thus, the deposited boron nitride film 1
8 from the material body 10, the inner diameter is 96 mm.
, obtain a high quality crucible-shaped boron nitride molded body with a length of 95 mm and a thickness of 1 mm.

(Example 2) In a reaction system similar to (Example 1), a diameter 3.
A titanium boride material 10 with a diameter of 0 mm and a length of 155 mm is supported in a reaction chamber by a support 12, boron trichloride gas and ammonia scum are introduced into the reaction chamber, and the reaction temperature is 19.
Boron nitride is deposited on the material body 10 by reacting for 6 hours at 50° C. and a pressure of Horr to form a boron nitride coating 18.
was formed. When the boron nitride coating 18 was taken out, it was found that the propagation of the cracks that had occurred at the joint 14 had been prevented at the bulges 16. By separating the deposited boron nitride JIi 18 from the material body 10 in this way,
A high quality tubular boron nitride molded body having an inner diameter of 30 mm, a length of 150 mm, and a thickness of 0.5 mm was obtained.

(Comparative example) A boron nitride film was formed by depositing a boron nitride film under the same conditions using a graphite material body 10 of the same type as in Example 1 except that the tube 16 was not installed. When the film was taken out, it was found that a crack had occurred at the joint 14 and that the crack had propagated from the joint 14 over a radius of 40 mm. When this boron nitride coating was cut and an attempt was made to separate it from the material body 10, the boron nitride coating burst during cutting.

[Effects of the Invention] According to the present invention, when manufacturing a ceramic molded body by the CVD method, by providing a specific groove on the raw material body surrounding the joint between the raw material body and the support body, the deposited Residual stress within the ceramic coating can be alleviated, and cracks caused by stress concentration at the joint can be prevented from propagating over a wide range.

Therefore, in the manufacturing process of ceramic molded bodies such as boron nitride, damage to the ceramic coating due to the propagation of cracks generated at the joint, which has traditionally been a problem, and damage to the ceramic coating during the separation process from the raw material, Damage to the ceramic coating caused by residual stress can be avoided. Therefore, extremely excellent effects such as improved manufacturing efficiency and reduced manufacturing cost of ceramic molded bodies are recognized.

[Brief explanation of drawings]

FIG. 1 is a schematic sectional view of a raw material for producing a ceramic molded body and a support according to an embodiment of the present invention. FIG. 2 is a plan view of the material body and support body of FIG. 1. FIG. 3 is a schematic cross-sectional view after a ceramic coating is formed on the material body and support body shown in FIG. 1. 0 2 4 6 8 Material, support, joint, clear, ceramic coating,

Claims (3)

[Claims] (1) The material supported by the support was heated in a reactor, a reaction gas was introduced into the reactor, and ceramics were deposited on the material using a chemical vapor phase reaction method to form a ceramic coating. After that, in the step of separating the raw material and the ceramic coating to produce a ceramic molded body made of the ceramic coating, a groove is provided in the raw material so as to surround the joint between the support and the raw material. A method for manufacturing a ceramic molded body. (2) The method for manufacturing a ceramic molded body according to claim 1, wherein the ceramic coating is formed of boron nitride. (3) A material used in the manufacturing method according to claim 1, characterized in that the groove surrounding the joint has a width of 2.5 mm or more and 3.5 mm or less, and a depth of 15 mm or more and 25 mm or less. material body.