JPH04108680A - Method and device for vapor-phase impregnation - Google Patents

Abstract

PURPOSE:To uniformly deposit a matrix component on the surface and inside of a porous formed body by vertically moving the formed body with respect to a matrix component depositing region formed in a reaction furnace. CONSTITUTION:A cylindrical holder 2, into which a gas inlet pipe 3 isolated from the outside by a seal 4 is inserted, is set in a reaction furnace A surrounded by heaters 6a-6c, and a porous formed body 1 is placed on the holder 2. The temps. of the heaters 6a-6c are then controlled to ta>tb>=tc and to ta>=T, where T is the lowest temp. at which the matrix component is deposited in order to form a matrix component depositing region B. The holder 2 is raised through a table 5 to position the optional part of the formed body 1 in the region B, and a matrix forming gas is then introduced into the holder 2 from the gas inlet pipe 3, passed through the formed body 1 to deposit the matrix component and then discharged from an outlet 7.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a method for producing a dense body with excellent mechanical properties by depositing a matrix component in the voids of a porous molded body by a gas phase method. This invention relates to a phase impregnation method and its manufacturing apparatus.

(Prior art) In recent years, ceramics such as non-oxide ceramics such as silicon nitride, silicon carbide, and sialon, and oxide ceramics such as aluminum oxide and zirconium oxide have been used as high-strength and high-temperature materials in place of conventional metal materials. are attracting attention, and various research and development efforts are being carried out. For example, silicon nitride, silicon carbide, etc. are being applied to high-temperature mechanical parts such as gas turbine parts and diesel engines due to their excellent mechanical properties and high-temperature properties. is in progress.

However, all of the above-mentioned ceramics are known to be brittle materials, and they lack reliability because they break at the slightest defect, which hinders their application to structural materials that require high strength. The current situation is that

Therefore, in order to solve these problems, research and development of so-called fiber-reinforced ceramics, in which toughness is imparted to ceramics by mixing whiskers, carbon fibers, and other inorganic fibrous substances, has been actively conducted. There is.

Specifically, the second type of fiber-reinforced ceramics is one made by adding inorganic fibers to ceramic powder and firing it, or by chemical vapor deposition (CVD) using a specific ceramic 7.x on the surface of the reinforcing fibers. Vapor-phase method (CVD method)
The so-called vapor phase impregnation method (Chemical V
There are known methods such as those based on apor infiltration.

Among these, those using the vapor phase impregnation method are attracting particular attention because they can produce materials with extremely superior toughness compared to other methods, such as A+++.

Ceram, Soc, Bull,, 65 [2]
345-50.1986 by David P, 5te
It has been proposed by Nton et al.

FIG. 4 shows this conventional method. The device used here basically includes a porous molded body 21, a holder 22 for holding this porous molded body 21,
Gas inlet 2 for introducing matrix forming gas
3. It consists of a heater 24 and a water cooling jacket 25 for cooling one side of the support means. According to this device, a high temperature region is formed by the heating means 24,
A porous molded body 21 and a holder 22 are placed in this high temperature region. When a matrix-forming gas is introduced into the porous molded body 21 through the gas inlet 23, matrix components are precipitated in the voids inside the molded body. However, if the molded body is in a complete soaking area, the matrix will precipitate on the surface of the molded body 21 before the inside of the molded body, and the matrix cannot be deposited inside the molded body 21. Therefore, in this method, The gas inlet side of the molded body 2 is cooled to a low temperature by the water cooling jacket 25 to form a temperature gradient inside the molded body 21, and the matrix is gradually precipitated from the bottom of the molded body 21, thereby forming the molded body. A matrix is deposited over the entire body 21.

(Problems to be Solved by the Invention) However, in the method of using a cooling means such as a water cooling jacket 25 for cooling one side of the molded body 21 in order to form a temperature gradient inside the molded body 21, the configuration of the device is It has its own limitations, and even if you consider uniform cooling on one side, it can only be applied to small molded products and simple shaped products such as disks and flat plates, and it cannot be used to create complex shaped products or large shaped products. was almost difficult. In addition, when the matrix is deposited on a large compact when the furnace is uniformly heated,
There was a problem that precipitation occurred preferentially on the surface, and therefore precipitation could not occur inside the molded body.

(Means for Solving the Problems) As a result of repeated studies on the above problems, the present invention has been developed to create a matrix in a specific area by forming a temperature gradient in the furnace and inside the molded body by controlling the heating means. The matrix component is precipitated in any part of the molded body by forming a region where the components can be precipitated and supporting a molded body support means so that the porous molded body can be moved to any position relative to this matrix precipitation region. The inventors have discovered that this allows the matrix component to be uniformly precipitated inside and on the surface of a large molded product or a molded product with a complex shape, without requiring any cooling means.

That is, in the gas phase impregnation method of the present invention, a porous molded body is placed in a reaction furnace, and the voids in the molded body are filled by passing a matrix-forming gas through the molded body and heating the molded body at the same time. This is a gas phase impregnation method in which a matrix component is precipitated in the furnace, and a matrix component detection region is formed in the furnace, the molded body is movably held with respect to the precipitation region,
The method is characterized in that a matrix component is precipitated in any part of the molded body, and according to the vapor phase impregnation apparatus, a porous molded body and a holding means for holding the molded body are placed in a furnace. , comprising a gas introducing means for introducing a matrix-forming gas into the molded body and a heating means, and at the same time as introducing the gas into the molded body, the heating means heats the molded body to a predetermined temperature. In the vapor phase impregnation apparatus for depositing a matrix component in the voids in the molded body, the heating means is controlled so that a matrix component deposition region is formed in a specific region in the furnace, and the matrix component is deposited in a specific region in the furnace. It is characterized in that the holding means is movable so that the molded body can be held at any position with respect to the exit area.

(Example) An example of the manufacturing method and manufacturing apparatus of the present invention will be described below with reference to FIGS. 1 to 4.

FIG. 1 is a schematic diagram of a gas phase impregnation apparatus according to the present invention. According to No. 1111, inside the reactor A, a porous molded body 1 is supported by a holder 2.

The holder 2 itself is composed of a cylindrical body made of a heat-resistant material such as graphite, and the molded body 1 is supported at the upper part of the cylindrical body. A gas introduction pipe 3 for introducing a matrix-forming gas from the outside of the reactor is installed inside the holder 2, and the inside of the holder 2 is substantially sealed from the outside by a seal 4. Furthermore, the holder 2 is installed outside the reactor 1 and is equipped with a motor (not shown).
The holder 2 and the molded body 1 are connected to a table 5 which is moved up and down by means of a vertical movement of the table 5, so that the holder 2 and the molded body 1 can also be moved up and down in the reactor.

On the other hand, heaters 6a, 6b, and 6C are installed at the outer periphery of the inside of the reactor A, which can independently control the temperature of each part of the reactor.

According to this device, the matrix-forming gas is introduced into the holder 2 from the gas introduction pipe 3 and then the porous molded body 1
As it passes through the interior, it is heated by a heater to react appropriately and precipitate matrix components, and then is discharged to the outside of the holder 2, and finally exhausted from an exhaust lower provided at the bottom of the furnace.

Next, a method for impregnating a porous molded body with a predetermined matrix component in a vapor phase according to the present invention using the above-mentioned apparatus will be described.

First, in the above device, the temperature of each heater 6 is controlled as follows. According to the present invention, when the set temperatures of the heaters 6a, 6b, and 6c are ta, tb, and tc, ta
It is important to control the temperature so that the relationship of >t b≧tc is satisfied, and thereby the temperature inside the furnace has the temperature distribution shown in FIG. 2. In Figure 2, the vertical axis is the distance in the longitudinal direction of the furnace,
The horizontal axis shows the temperature at the center of the furnace at each position. At this time, the temperature ta is ta≧T with respect to the lowest temperature T at which matrix components are precipitated from the matrix forming gas by a gas phase reaction.
is set to be. As a result, a matrix component detection region B is formed near the high temperature side from the intersection of the temperature distribution curve and the temperature T in FIG.

Next, FIGS. 3a, 3b, and 3c illustrate a process for precipitating matrix components in the voids in the porous molded body.

First, in the initial process, as shown in FIG. position to reach. At this time, based on the temperature gradient in the furnace, a temperature gradient is formed inside the porous compact in which the gas discharge side is higher in temperature than the gas introduction side. When the matrix-generating gas is supplied from the gas inlet pipe, the matrix-generating gas does not react on the low-temperature gas inlet side when passing through the porous molded body having a temperature gradient, and reaches the matrix-generating region B. , the matrix is deposited in the void inside the molded body above the molded body that satisfies the matrix precipitation conditions.

The residue is deposited. Specifically, when the molded body is composed of a fibrous material, the matrix component first precipitates on the surface of the fibrous body, and as the amount of precipitation increases, all the voids in the molded body are filled. Furthermore, the deposited matrix itself becomes a heat transfer medium, and the matrix deposition region moves from the gas outlet side to the gas inlet side. At this time, if the molded object is small in shape, it is possible to deposit the matrix over the entire molded object through this chain of matrix precipitation, but for large shaped molded objects, there is a limit to heat transfer. Because of this, it is impossible to deposit the matrix over the entire molded body.

Therefore, according to the present invention, as shown in FIG. 2b, by raising the table 5, the matrix precipitation area B is removed.
moves to the gas introduction side of the molded body 1, thereby making further precipitation of the matrix possible.

After ascending this table 5 appropriately, the final stage 2
As shown in Figure c, by locating the matrix precipitation region at the lowest part of the molded body 1, the matrix can be deposited throughout the interior of the molded body.

This movement of the matrix generation region by movement of the table 5 can be performed intermittently or continuously depending on the precipitation rate of the matrix component and the size of the molded body.

According to the above-described apparatus and method, the porous molded body may be a two-dimensional fabric made of carbon fibers such as carbon or SiC, a laminate of fabrics, a three-dimensional fabric, or a porous molded body such as SiC whiskers, 5izN4 whiskers, AhO:t whiskers, etc. A molded body made of ceramic whiskers or the like can be used, and silicon carbide, pyrolytic carbon, silicon nitride, sialon, alumina, etc. can be used as the matrix component to fill the voids of this porous molded body.

Among these, a structure having high temperature strength and high toughness can be produced by impregnating a porous molded body made of silicon carbide fibers with silicon carbide in a vapor phase.

Further, the fibers constituting the porous molded body are suitably those having an average diameter (minor diameter) of 1 to 30 μm, and plain weave or three-dimensional weave of these is suitable. In addition, trichloromethylsilane, silicon tetrachloride, methane, and aluminum trichloride are used as reaction gases for precipitating the matrix, and these gases are supplied mixed with a carrier gas such as hydrogen.

The precipitation temperature during matrix formation varies depending on the type of matrix to be precipitated, but in the case of precipitating silicon carbide, it is preferably 900°C to 950°C, and in this range β-3iC is precipitated and the precipitation rate is low. On the other hand, at a temperature of 1000°C to 1150°C, two phases of β-3iC and Si are precipitated, so high purity SiC is not produced, and 120°C is slow and easy to control.
This is because β-3iC precipitates at 0°C to 1300°C, but the precipitation rate is too fast to form a sufficient matrix inside the molded body.

Further, the pressure within the reactor is greatly related to the precipitation rate of the matrix, and the higher the concentration, the faster the precipitation rate. According to this gas phase impregnation method, when depositing a matrix in a porous molded body, if the rate is too fast, sufficient matrix cannot be formed, so it is better to slow down. Preferably it is 100 Torr or less. In addition, gas concentration is also a major factor that determines the deposition rate, especially 0.4
It is desirable to mix the above-mentioned predetermined gases at a ratio of ~10% by volume.

The present invention will be explained below based on specific examples.

Example porous molded body whose size is 100×10100×
In step 5, a plain weave of carbonaceous long fibers was prepared. This molded body was set in the holder 2 in the gas phase impregnation apparatus shown in FIG.

Then, the temperature of heaters 6a, 6b, and 6C is set to 12
The temperature was set at 00°C, 1950°C, and 1750″C.

After confirming that the temperature inside the furnace had become uniform, the temperature distribution inside the furnace was measured, and the temperature difference between the highest and lowest temperatures was 450°C. It was confirmed that the temperature gradient within the molded body due to this was a maximum of 220°C.

Next, the molded body l is adjusted to the position shown in Fig. 3a with respect to the matrix component deposition formation area B in the furnace, and H2 gas containing CH3SicIz gas at a ratio of 1% by volume is used as the matrix forming gas. was introduced into the furnace.

At this time, when introducing the reaction gas, the pressure is increased to 760 torr inside the cylindrical holder 2 with the molded body 1 as a boundary.
The atmosphere outside the holder 2 was set at 25 torr to form a pressure gradient.

In this state, the reaction starts and β-
A matrix consisting of 3iC was deposited.

Subsequently, the table 5 is slowly raised step by step until it reaches the position shown in FIG.
It was controlled to be in the position shown in the figure.

This enabled the matrix component to be precipitated over the entire molded body.

The obtained molded body had a theoretical density ratio of 85%, and 5ENB
As a result of measuring the fracture toughness by the method, it was 21MPa-m""
Met.

Note that the fracture toughness of conventional SiC monolithic materials is approximately 5 MPa-m''.

(Effects of the Invention) As detailed above, according to the present invention, by setting a matrix generation region in a specific region in the furnace and supporting the porous molded body so as to be able to move up and down with respect to this region, By adjusting the positions of the porous molded body and the matrix generation region according to the size of the molded body, it is possible to easily handle large-sized molded bodies or complex-shaped molded bodies without the need for any cooling means. The matrix components can also be uniformly deposited inside and on the surface. This makes it possible to put into practical use the production of various structural materials by vapor phase impregnation, and to greatly expand the field of application.

[Brief explanation of drawings]

Fig. 1 is a schematic explanatory diagram of the vapor phase impregnation apparatus of the present invention, Fig. 2 is a diagram showing the temperature distribution in the furnace, and Figs. 3a to 3c are the final steps for explaining the vapor phase impregnation method of the present invention. FIG. 4 is a schematic diagram for explaining a conventional gas phase impregnation apparatus. A... Gas phase impregnation device B... Matrix component analysis appearance area 1... Porous molded body 2... Holder 3... Gas inlet 5... Movable table 6a to 6c... Heater Patent applicant (663) Kyocera Corporation

Claims (6)

[Claims] (1) A porous molded body is placed in a reaction furnace, and a matrix-forming gas is passed through the molded body and the molded body is heated at the same time, so that matrix components are precipitated in the voids within the molded body. The phase impregnation method is characterized in that a matrix component deposition region is formed in the furnace, the molded body is movably held with respect to the precipitation region, and the matrix component is deposited on any part of the molded body. Gas phase impregnation method. (2) The vapor phase impregnation method according to claim 1, wherein the porous molded body is made of carbonaceous fiber. (3) The vapor phase impregnation method according to claim 1, wherein the matrix component comprises silicon carbide. (4) A porous molded body, a holding means for holding the molded body, a gas introduction means for introducing a matrix-forming gas into the molded body, and a heating means are provided in the furnace, and the molded body In a gas phase impregnation apparatus, a matrix component is precipitated in the voids within the molded body by introducing gas into the body and simultaneously heating the molded body to a predetermined temperature by the heating means, the matrix component is precipitated in the voids within the molded body. The heating means is controlled so that a component deposition region is formed, and the holding means is made movable so that the molded body can be held at an arbitrary position with respect to the matrix component deposition region. Characteristic gas phase impregnation equipment. (5) Claim 4, wherein the molded body is made of carbonaceous fiber.
The vapor phase impregnation device described. (6) The vapor phase impregnation device according to claim 4, wherein the matrix component is made of silicon carbide.