JP2002211985A - Method for C or SiC coating of SiC or C fiber - Google Patents

Abstract

(57) [Summary] [Object] To form SiC or C fiber / S by directly forming a SiC or C coating layer on a fiber preform.
SiC or C without delamination at the interface of iC matrix
Obtain a fiber / SiC composite. [Constitution] Maintain the same constant pressure on the reaction gas supply side and exhaust side of the SiC or C fiber preform stored in the reactor, and supply hydrocarbon gas such as methane, ethane, and propane at a maximum flow rate of 300 cc / min. Meanwhile, the hydrocarbon gas is thermally decomposed under the conditions of a pressure of 15 kPa or less and a maximum reaction temperature of 1100 ° C., and C as a pyrolysis product is precipitated around SiC or C fibers. When coating with SiC, the alkylchlorosilane is thermally decomposed under the conditions of a pressure of 10 kPa or more and a maximum reaction temperature of 1100 ° C. while supplying a mixed gas having a flow ratio of alkylchlorosilane / hydrogen of 60% by volume or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to SiC or C fiber / S
The present invention relates to a method of pre-coating SiC fibers with C or SiC when manufacturing an iC composite material.

[0002]

2. Description of the Related Art Ceramic materials having excellent heat resistance and wear resistance have attracted attention as materials used in special or extreme environments such as the nuclear and aerospace fields. Ceramic materials are also used as members for heat exchangers, mechanical seals, and the like exposed to severe conditions. Above all,
Non-oxide ceramics such as SiC and Si ₃ N ₄ are materials that maintain excellent strength even in a high-temperature atmosphere. In particular, SiC and C are superior in strength, heat resistance, high thermal conductivity, and wear resistance, and they do not produce long-lived radionuclides by neutron irradiation. It is a promising material in a wide range of fields up to the first partition of the furnace.

[0003] SiC has a high melting point and excellent high-temperature properties, but is itself a brittle material. Therefore, development of a composite material reinforced with C fibers or SiC fibers has been promoted. SiC or C-fiber / SiC composite material is reactive sintering,
Although it is manufactured by various methods such as a hot press method, there is an advantage that a gas-phase reaction permeation method (CVI) can be formed into an arbitrary shape close to the final product and high strength. In the gas phase reactive infiltration method (CVI), the internal voids of SiC or C fibers are filled with a SiC phase generated by thermal decomposition of alkylchlorosilane.

[0004]

The properties of the produced SiC or C fiber / SiC composite material are greatly influenced by the fiber / bulk interface structure. Therefore, C, SiC, BN
After pre-coating SiC or C fibers with the above, a gas phase reactive infiltration method is performed. The coating layer applied to the SiC or C fiber has a high affinity for SiC generated by the thermal decomposition reaction, and improves the bonding strength at the fiber / bulk interface.

However, since the conventional coating is applied to the yarn of SiC or C fiber, it is difficult not only to coat the coating itself but also to knit the coated SiC or C fiber into a woven fabric having a predetermined shape. . Even when knitted into a woven fabric, the coating layer may peel or fall off from the SiC or C fibers during pressure lamination or preform formation, and as a result, the improvement in affinity by the coating layer cannot be fully utilized.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been devised to solve such a problem. By controlling the thermal decomposition reaction, a uniform SiC or C fiber preform can be obtained. An object of the present invention is to provide a SiC or C fiber / SiC composite material in which a C coating layer is directly formed and the interface has high bonding strength and excellent thermal and mechanical properties.

[0007] In order to achieve the object, the C coating method of the present invention maintains the same constant pressure on the reaction gas supply side and the exhaust side of the SiC or C fiber preform accommodated in the reactor, and prepares methane and ethane. , While supplying hydrocarbon gas such as propane, pressure 20 kPa or less, maximum reaction temperature 1100
It is characterized in that hydrocarbon gas is thermally decomposed under the condition of ° C., and C as a pyrolysis product is deposited around SiC or C fiber.

When coating with SiC, the reaction gas supply side and the exhaust side of the SiC or C fiber preform accommodated in the reactor are maintained at the same constant pressure, and the flow ratio of alkylchlorosilane / hydrogen is 60% or less. While supplying a mixed gas of the above, the alkylchlorosilane is thermally decomposed under the conditions of a pressure of 10 kPa or more and a maximum reaction temperature of 1100 ° C., and SiC as a pyrolysis product is precipitated around the SiC or C fiber.

[0009]

In the method of coating SiC or C fiber with C, SiC, BN or the like in advance, as described above, the difficulty of the coating method itself is required when forming the coated SiC or C fiber into a fiber preform of a predetermined shape. And the adhesion of the coating layer to SiC or C fibers. Then, the present inventors investigated and examined a method of directly forming a SiC or C coating layer on a fiber preform molded into a predetermined shape. As a result, when the reaction conditions are controlled under the pressure conditions under which the reaction of generating C or SiC proceeds evenly inside the fiber preform, the formed fiber preform is coated with C or SiC in which the thickness variation is suppressed. It has been found that the layer is formed directly.

The rate of generation of C or SiC is determined by the concentration (pressure) and temperature of the reaction gas. Therefore, the reaction gas supply side and the exhaust side of the fiber preform are maintained at a constant pressure so that the generation reaction of C or SiC proceeds uniformly in any place of the fiber preform, and the individual fibers have the same concentration. Expose to reaction gas. When a difference occurs between the pressure on the reactive gas supply side and the pressure on the exhaust side of the fiber preform, the generation reaction of C or SiC on the high-pressure reactive gas supply side becomes active, and the reaction on the exhaust side is delayed. Therefore, the thickness of the coating layer formed on the fiber surface between the supply side and the exhaust side cannot be made uniform. The decrease in uniformity caused by the pressure difference becomes significant at a pressure difference of 0.5 kPa or more.

The reaction for forming C or SiC is promoted as the pressure is increased. However, if the pressure is too high, it is difficult to control the speed of the reaction for forming C or SiC, so the pressure is set to 20 kPa or less (preferably 15 kPa or less). Although the reaction of forming C or SiC is accelerated with an increase in the reaction temperature, if the reaction temperature is too high, a large difference in the reaction rate tends to occur depending on the location of the fiber preform. Therefore, the reaction temperature is set to 1100 ° C. or less in order to suppress the variation in the thickness of the coating layer formed on the fiber surface to 20% or less.

In the thermal decomposition reaction of alkylchlorosilane, Si
When C is deposited, the flow ratio of alkylchlorosilane: hydrogen is adjusted to 60% or less. If the flow ratio exceeds 60%, the amount of alkylchlorosilane becomes too large, and SiC
The formation reaction proceeds excessively, and it becomes difficult to control a very small thickness of the layer. Alkyl chlorosilane is 1 atm (0.1MPa)
Since it is a liquid underneath, the silane evaporated under reduced pressure is transported to the reaction vessel by hydrogen gas (carrier gas). At this time, if the pressure is too low, the flow rate of hydrogen decreases, and it becomes difficult to precisely control the alkylchlorosilane: hydrogen mixture ratio, and as a result, the thickness of the coating layer varies. Therefore, in order to precisely control the mixing ratio,
Pressure of mixed gas of alkylchlorosilane and hydrogen is 10k
Set to Pa or more.

[0013] Thus, the SiC is added to the fiber preform.
Alternatively, since the C coating layer is directly formed, the drawback of the conventional method, in which the coating layer is inevitably peeled and dropped during the molding of the fiber preform, is eliminated, and the effect of the SiC or C coating layer is developed, and it is generated in a subsequent process. S
The bonding strength of the iC phase to SiC or C fiber is improved,
A SiC fiber / SiC composite material having excellent thermal and mechanical properties can be obtained.

[0014]

EXAMPLES (Coating of SiC fiber with C) Plain weave Si
By stacking 7 layers of C fiber fabric, 2mm thick
Was prepared. Forming a SiC fiber preform fiber laminate into a disc shape with a diameter of 40 mm,
Housed in the reactor. After vacuum suction of the reactor to 0.1 Pa, the resin adhering to the fibers was decomposed and removed by heating to 1200 ° C. for 1 hour. Next, methane was fed into the reactor at a flow rate of 200 cc / min as a reaction gas, the internal pressure of the reactor was increased to 14.7 kPa, and C, which is a pyrolytic product of methane, was precipitated around the preform fibers. With respect to the fiber preform on which carbon was deposited, the layer thickness of C deposited was measured at a total of nine places on the upstream side, the center part, the downstream side in the cross-sectional direction, and both ends and the center part in the circumferential direction.

As can be seen from the measurement results of FIG.
At a reaction temperature of 0 ° C. or less, the variation in the layer thickness depending on the location was small, and the thickness of the C coating layer deposited at 950 ° C. × 1 hour varied only within 16%. Further, as shown in FIG. 2 showing the effect of the methane flow rate on the layer thickness distribution, the variation in the layer thickness was smaller as the methane flow rate was smaller. Further, the gas pressure is set to 15 kPa
When the thickness was set below, the variation in the layer thickness was within several tens of percent (FIG. 3). In FIG. 1, the methane flow rate = 200 c
c / min, pressure = 14.7 kPa, reaction time = 1 hour, in FIG. 2, reaction temperature = 950 ° C., gas pressure = 14.7 kPa,
The reaction time was 1 hour, in FIG. 3, the reaction temperature was 950 ° C., the methane gas flow rate was 200 cc / min, and the reaction time was 1 hour.

From the above results, the reaction temperature is 1100 ° C. or less, the methane flow rate is 300 cc / min or less, and the gas pressure is 15 kPa.
When the following reaction conditions are adopted, it is confirmed that a coating layer having a uniform layer thickness is formed around the SiC fiber even in a fiber preform molded into a predetermined shape.

(Coating of SiC Fiber with SiC) A similar SiC fiber preform is set in a reactor, and a mixed gas of methyltrichlorosilane (reaction gas) and hydrogen (reducing carrier gas) is introduced into the reactor. The SiC fibers were coated with SiC generated by thermal decomposition of methyltrichlorosilane.

With respect to the SiC fiber preform coated with SiC, the thickness of the SiC coating layer was similarly measured at nine measurement points. When the reaction temperature is 1100 ° C. or less, the variation in the layer thickness is small (FIG. 4). When the flow rate ratio of methyltrichlorosilane: hydrogen is 60% or less, the variation in the layer thickness is small (FIG. 5). The result that the variation in thickness was small (FIG. 6) was obtained. In addition,
FIG. 4 shows methyltrichlorosilane / hydrogen = 0.5 (volume ratio), hydrogen flow rate = 1 liter / min, gas pressure = 14.7 k
Pa, reaction time = 30 minutes, FIG. 5 shows reaction temperature = 1000
° C, hydrogen flow rate 1 liter / min, gas pressure 14.7 kPa,
Reaction time = 30 minutes, FIG. 6 shows methyltrichlorosilane / hydrogen = 0.5 (volume ratio), hydrogen flow rate = 1 liter / min, reaction temperature = 1000 ° C., reaction time = 30 minutes, and other reaction conditions were constant. This is the result when it is maintained.

From the above results, the flow rate ratio of methyltrichlorosilane / hydrogen is 60% by volume or less, and the gas pressure is 10 kPa
As described above, by setting the reaction temperature to 1100 ° C. or lower, even if the fiber preform is formed into a predetermined shape, the
It is confirmed that a SiC coating layer having a uniform thickness is formed around the C fibers.

(Production of SiC fiber / SiC composite material) A C coating layer having a thickness of 760 nm, SiC (250 n
m) + C (380 nm) multiple coating layers, C (8
0 nm) + SiC (150 nm) + C (70 nm) and SiC (170 nm) + C (10
Regarding the fiber preform on which the multilayer coating layer of 8 nm) + SiC (350 nm) + C (117 nm) was formed, the internal voids of the fiber preform were filled with a SiC phase by a gas phase reactive infiltration method (CVI). In the gas-phase reaction permeation method, a mixed gas of methyltrichlorosilane: hydrogen = 1: 4 (volume ratio) is fed into a fiber preform accommodated in the same reactor, and the reaction temperature is 1000 ° C. and the pressure is 13.3 kPa. To cause a thermal decomposition reaction of methyltrichlorosilane to precipitate the generated SiC in the internal voids of the fiber preform.

By continuing the gas phase reactive infiltration method for 20 hours, the internal voids of the fiber preform were filled with the SiC phase, and no delamination was detected at the SiC fiber / SiC bulk interface (FIG. 7). . Therefore, the S
iC fiber / SiC composite material has excellent bending strength and
The fiber / SiC-based material exhibited extremely excellent physical properties. In the above embodiment, the SiC fiber was used.
Similarly, when C fiber is used instead of SiC fiber,
A composite material without delamination at the fiber / SiC interface was produced.

[0022]

As described above, in the present invention, since the SiC or C coating layer is directly formed on the fiber preform formed into a predetermined shape, the conventional fiber preform is formed after forming the coating layer. The SiC or C coating layer is effectively used for improving the adhesion of the SiC bulk to the SiC or C fiber without the risk of the coating layer peeling or falling off as observed by the method. Therefore, the produced SiC or C fiber / SiC composite material is SiC
Or, there is no delamination at the interface of the C fiber / SiC matrix, and the SiC or C fiber / SiC-based original excellent heat resistance,
Utilizing its wear resistance, it is used as a high-performance material for aerospace, reactor bulkheads, heat exchanger parts, etc.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of reaction temperature on the thickness distribution of a C coating layer deposited by thermal decomposition of methane.

FIG. 2 is a graph showing an influence of a methane gas flow rate on a thickness distribution of a C coating layer deposited by thermal decomposition of methane.

FIG. 3 is a graph showing the effect of the pressure of a reaction gas on the thickness distribution of a C coating layer deposited by thermal decomposition of methane.

FIG. 4 is a graph showing the effect of reaction temperature on the thickness distribution of a SiC coating layer deposited by thermal decomposition of methyltrichlorosilane.

FIG. 5 is a graph showing the effect of the flow rate ratio of methyltrichlorosilane / hydrogen on the thickness distribution of the SiC coating layer deposited by thermal decomposition of methyltrichlorosilane.

FIG. 6 is a graph showing the effect of reaction gas pressure on the thickness distribution of a SiC coating layer deposited by thermal decomposition of methyltrichlorosilane.

FIG. 7 shows that the internal voids of the fiber preform are filled with a SiC matrix by a gas phase reactive infiltration method.
Micrograph showing structure of SiC composite material

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C04B 35/56 101L 35/80 BC (72) Inventor Yuta Kato Gokasho, Uji City, Kyoto Prefecture Kyoto University Energy Science and Engineering Research (72) Inventor Hiroshi Araki 1-2-1, Sengen, Tsukuba, Ibaraki Prefectural Ministry of Education, Culture, Sports, Science and Technology Ministry of Science and Technology (72) Inventor Tetsuji Noda 1-1-2, Sengen, Tsukuba, Ibaraki Pref. 4G001 BA22 BA60 BA76 BA77 BA86 BB22 BB60 BB86 BC72 BD01 BD12 BE31 4G032 AA52 BA02 GA08

Claims (2)

[Claims] 1. A pressure of 20 kP while a hydrocarbon gas is supplied while maintaining a reaction gas supply side and an exhaust side of a SiC or C fiber preform accommodated in a reactor at the same constant pressure.
a) A method for C coating SiC or C fibers, wherein hydrocarbon gas is thermally decomposed under conditions of a maximum reaction temperature of 1100 ° C. and C as a pyrolysis product is deposited around SiC or C fibers. . 2. The reaction gas supply side and the exhaust side of the SiC or C fiber preform accommodated in the reactor are maintained at the same constant pressure, and the flow ratio of alkylchlorosilane / hydrogen is 6%.
While supplying a mixed gas of 0% or less, the alkylchlorosilane is thermally decomposed under the conditions of a pressure of 10 kPa or more and a maximum reaction temperature of 1100 ° C., and the thermal decomposition product SiC is converted to SiC.
Or SiC characterized by being deposited around C fibers
Or a method of coating C fibers with SiC.