JPS60200860A - Manufacture of high strength acid-resistance carbon/carbon composite material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to high strength, oxidation resistant carbon/carbon composites formed by diffusing antioxidants into a composite matrix. The antioxidant is placed inside the composite matrix and diffused into the composite matrix.

BACKGROUND OF THE INVENTION The use of boron in the manufacture of carbon materials such as graphite made from graphite powder and fillers such as graphitizable materials such as pitch or resins is known. Boron enhances the bonding of the material and its conversion into graphite.

It is also known in the art to use boron in the manufacture of carbon/carbon composites made of carbon or fibrous carbon materials such as graphite cloth. This boron or boron-containing material is placed on top of the fiber 1,1F shape and the fiber is then densified by one or more impregnations with furan/furfural resin.

An example of this type of composite is Leo C6 Old+rcnr
eicl+ U.S. Patent Nos. 3.672.9.36 and 4
．． No. 119.189. These patents recognize that there are certain improvements in stack strength and oxidation resistance when a boron-containing compound is added to the fibrous carbon material prior to resin impregnation and subsequent carbonization of the resin.

Robert C., 5half U.S. Patent 4.1
No. 64.601 and No. 4.101.354 are
The interlaminar tensile strength of carbon/carbon composites containing boron is low during carbonization and graphitization of the composite (both
It has been shown that the tensile strength in the fiber direction of the fibrous carbon material is greatly improved when heated to 160°C, and furthermore that the tensile strength in the fiber direction of the fibrous carbon material at such temperature is much lower than that of the composite fibers caused by the reaction with boron at high temperature. It is disclosed that the reduction is typically significant, apparently due to the deterioration of the carbonaceous material. According to the teachings of this patent, significant reductions in the fiber direction tensile strength of fibrous carbon materials are prevented by the use of a protective coating on the fibers.

The protective coating includes a thermosetting material that remains flexible after being exposed to curing temperatures. The coating is applied to the fiber and cured prior to application of the resin and boron-containing compound. The resin and boron-containing compound are then applied and the resin is at least partially cured during the "B" stage process. After forming the laminate and heating the laminate to a temperature sufficient to carbonize and at least partially graphitize the resin, the criticality of the composite tensile strength in the fiber direction of the fibrous carbon material of the laminate is determined. It has been found that the interlaminar tensile strength is greatly improved without any significant decrease.

Robert C., 5haffer and William
m L, ]'arasen U.S. Patent 4.321.29
No. 8 discloses the formation of carbon/carbon composites with higher oxidation resistance, improved high temperature stability, higher density and improved laminate tensile strength. According to the teachings herein, a mixture is formed that includes a refractory metal and a thermoset resin that remains flexible after being exposed to curing temperatures. The metal can be in the form of particulate metal or atomically dispersed metal or both. This metal can react with boron at high temperatures in a ternary system of carbon. The fibrous carbon material is coated with this mixture and the thermosetting resin is cured.

The coated fibrous carbon material is then re-impregnated with a second thermoset resin containing a boron compound and an optional refractory metal capable of reacting with boron to form a stable metal boride.

As for the refractory metal in the first coating, if present, it can be in the form of particulate metal or atomically dispersed metal or both.

The second thermoset resin is at least partially cured and the multiple layers of fibrous material are then assembled to form a composite.

The composite is then heated to a temperature sufficient to carbonize and graphitize the thermoset resin. US Patent 4.16
Carbon/carbon composites made by the methods described in No. 4.601 and No. 4.32L 298 have virtually no inherent voids.

Composites formed in this manner are desirable for surfaces exposed to oxygen attack, and the oxidation rate of the composite was significantly reduced.

Structure and effect of the present invention U.S. Pat. No. 4.164.601 and t 321.298
The carbon/
The mechanical properties of carbon composites are improved by the following method.

In accordance with the present invention, the fibrous carbon material is first coated with a flexible thermoset resin that remains flexible after curing. The thermoset resin can optionally include a refractory metal that can react with boron to form gold FA boride. The thermoset resin is then cured, and the coated fibers are re-cured with a second thermoset resin containing an illuminant compound and an optional refractory metal capable of reacting with boron to form a metal boride. coated. Regarding the optional refractory metal in the first coating, this metal, if present, can be in the form of particulate metal or atomically dispersed metal or both. The second thermosetting resin is partially cured.

That is, it is heated at a temperature and time to subject the second thermoset resin coating to a ``13'' step. The impregnated fabric is then cut into patterns and shaped to provide a thermoset product, which The thermoset resin is then heat treated to carbonize and graphitize and essentially form a carbon/carbon composite.

The composite can then be densified by re-impregnation with a resin containing atomically dispersed boron and optionally an atomically dispersed refractory metal that can react with the boron to form a metal boride. can. The composite is then finally densified using carbon chemical vapor deposition or further treatment with a re-impregnating resin. This is then subjected to a heating cycle to carbonize the reimpregnated material, and the resulting carbon/carbon composite is then further processed by carbon chemical vapor deposition or by a final application of the reimpregnated resin. Heat treated to diffuse boron into the material matrix.

Reimpregnation with a resin containing atomically dispersed boron is an optional preferred step. The total boron content of the composite can be contained in the second thermoset resin added during the pre-prescribing operation, but some of the boron can be removed away from the fibers.
It is preferred to place it close to the last densifying medium that is free of boron, ie the carbon from the chemical vapor deposition or the carbon from the last re-impregnation. This provides the best diffusion of boron into the final densified carbon and reduces the possibility of sheathing around the fibers.

In accordance with the present invention, the fibrous carbon material is first coated with a flexible thermoset that remains flexible after curing. The thermoset resin optionally includes a refractory metal that can react with boron to form a metal boride. The refractory metal can be atomically dispersed in the resin, i.e. the refractory metal can be part of the molecular structure of the resin; or it can be a particulate metal; or both can be used. be able to.

Robert C15haffer's US Patent 3+
Thermosetting resins such as those disclosed in J44,5JO can be used in the present invention and are hereby incorporated by reference. This patent describes furfuryl alcohol copolymers, which are made by reacting maleic acid or maleic anhydride with polyhydroxy compounds such as ethylene glycol. It forms an ethylenically unsaturated polycarboxylic ester prepolymer.

The ester prepolymer is then copolymerized with furfuryl alcohol to form a furfuryl alcohol copolymer.

Thermosetting resins containing atomically dispersed metals can be made by incorporating refractory metals into the resin in the form of reaction products of tungsten carbonyl and/or molybdenum carbonyl and pyrrolidine. An example of such a thermoset resin is a copolymer of furfuryl alcohol and a polyester prepolymer that is reacted with a complex that is the reaction product of tungsten carbonyl and/or molybdenum carbonyl and pyrrolidine. It is something. Such copolymers are described in U.S. Pat. No. 4, Robert C.
No. 087.482 is disclosed in more detail. made by reacting monomers and prepolymers with complexes that are the reaction products of tungsten carbonyl and/or molybdenum carbonyl and pyrrolidine,
Another thermosetting polymer containing chemically bonded metal atoms is RoberLC.

5haffer U.S. Pat. No. 4.185.043, 4.
No. 302.392. After the resin is prepared, it can be diluted with a suitable solvent such as dimethylformamide to a solids content of, for example, 70%.

Fibrous carbon materials that can be used in the present invention include any carbon material in the form of fibrous filaments or other forms. Examples include fabrics such as carbon or graphite fabrics. The term carbon herein refers to all forms of carbon including graphite.

The flexible first coating is applied to the fibrous carbon material in a suitable manner and cured. One method that may be used is to dip the fibrous carbon material into an open container of coating material, then remove excess coating material by passing the fibrous carbon material through a pressure roller, and then remove the fibrous carbon material by passing it through a pressure roller. drying the coating by hanging it in air at ambient temperature to vaporize some of the solvent in the coating material. Curing of the coating material is then accomplished, for example, by placing the fibrous carbon material in a circulating air oven to allow polymerization of the resin and further removal of remaining solvent. The solids content of the thermosetting coating material is about 5-200% by weight of the fibrous carbon material.
The conditions are adjusted to provide a cured coating of

Following application of the flexible coating, the fibrous carbon material is then re-impregnated with a second thermosetting resin, which is partially cured or "B-staged"("B-staged").″'−
staged). This resin may be the same as a flexible thermoset resin. The resin may or may not contain suitable amounts of atomically dispersed or particulate refractory metals, or both, as described above. The resin also contains a boron compound, the amount of boron preferably being balanced on a molecular basis with the amount of metal present in the overall system. The boron-containing compound is preferably amorphous boron. Impregnation and curing of the second coating of thermoset resin is accomplished by any suitable method such as dipping the coated fibrous carbon material into an open container of thermoset resin containing boron and, if desired, a refractory metal. can. Excess material is removed by passing the fibrous carbon material between pressure rollers, after which the material is suspended in air at ambient temperature to vaporize some of the solvent contained in the resin. dried. Preferably, the amount of amorphous boron blended with the resin is selected such that the amorphous boron does not constitute about 2-9% by volume of the laminate. The dry fibrous carbon material is then treated to at least partially cure the thermoset resin, such as by placing it in a circulating air oven to drive polymerization of the resin.

The resulting laminate is then preferably coalesced and densified with a resin matrix that is further cured. In one process to do this, 5" i-layers are assembled into 11" laminates at elevated pressure and temperature in a mold in an electrically heated platen press. J! The resin is allowed to sit for a sufficient time to make it sufficiently self-supporting to provide a degree of fiber/resin matrix adhesion and to retain its shape and size during subsequent processing.

The laminate is then carbonized and preferably at least partially graphitized, for example by heating at a temperature of 1400 DEG to 2200 DEG C. For example, carbon-organic resin composites are first shaped by molding and at least partially precured. The composite is then placed in an oven that is heated at a predetermined rate to a temperature on the order of 1000'F (538C) to essentially decompose the resin without delamination or other damage to the composite. To carry out this carbonization, the carbonization time can be increased up to 14 days.

The laminate is then further heated in a furnace to higher temperatures to further carbonize and/or graphitize the resin. This higher temperature can be between 1400<0>C and 2200<0>C.

The characteristics (numerical voids) in the obtained carbon/carbon composite are
It is at least partially filled by treatment with a medium containing carbon-graphite material. This is accomplished by first treating the composite with a reimpregnation resin containing atomically dispersed boron.

The reimpregnated resin can optionally include a refractory metal atomically dispersed in the resin system. Examples of such resins are:
P. Anthony Hinman US Patent 4.
No. 412,064.

Following the optional resin re-impregnation treatment, the composite is further densified by chemical vapor deposition or re-impregnation with additional mesophase coal tar pitch. Chemical vapor deposition deposits pyrolytic type carbon-graphite material within and on the surfaces of the voids. Surfaces can be sealed in this way, which results in composites with considerably lower surface areas. Mesophase coal tar pitch can be used to deposit a carbon-graphite matrix and densify the composite.

However, this method is not a preferred embodiment since the composite still retains a relatively large amount of porosity after densification. This carbon-graphite material, whether deposited by chemical vapor deposition or by coal-coeur pitch reimpregnation, is sensitive to oxygen attack. However, the composite is now treated at temperatures such as 3500-4500° C. to diffuse the boron contained in the boron-containing reimpregnation resin into the carbon of the chemical vapor deposition or coal tar pitch.

This diffused boron changes the properties of the chemical vapor deposited carbon or coal tar pitch carbon so that subsequent silicon carbide coatings or other surface coatings are
It is no longer vulnerable in the 400'F range. That is, practice of the present invention not only provides fiber protection from boron attack, but also provides uniform oxidation resistance throughout the composite and allows the chemical vapor deposited carbon or coal tar pitch carbon to be modified to provide other coatings. Provides a synergistic surface that promotes improved oxidation resistance for.

Example 1 A resin made according to Example 1 of 5haffer US Pat. No. 4,087,482 was placed in an open container and a carbon fabric was immersed in the resin. The solids content of the resin was adjusted to produce a coating that comprised approximately 28% of the weight of the fabric.

The fabric is passed through a pressure roller to remove excess coating material;
It was hung in the air to dry at ambient temperature. Next, fold the fabric into approx.
Placed in a circulating air oven maintained at 25'F for approximately 30 minutes. This temperature treatment cured the resin sufficiently to avoid intermixing with the resin in the second coating.

The coated fabric was then treated with a milled material (a) consisting of 82.2% by weight phenolic resin and 17.8% by weight amorphous boron.
Further impregnation was carried out by immersion in an open container containing grind. Enough milling was added to give about 55% by weight of the original weight of the fabric. The fabric was passed through a pressure roller to remove excess resin and the prep L/g was hung to dry in air at ambient temperature.

Then, the fabric is air heated to a temperature below about 180℃! Place in the oven for about 60 minutes, then reduce the temperature to 200'F for about 30 minutes.
for 1 minute, then increase the temperature to 225'F for about 10 minutes. This temperature treatment advances the resin to the "B" stage.

The impregnated fabric was then cut into pieces of chosen size and J(a), which were then constructed into the desired shape.

The laminate is integrated, densified, and the Mul-IJ Nox material is pressed into a conforming mold using an electrically heated platen press for approximately 20 minutes.
1.1 kg/Cm2 (300psi), approximately 177
Cure at 350° F. for about 90 minutes.

It has been found that the time required for curing depends on various factors including wall thickness and the shape of the part.

When removed from the press, the parts had a high degree of fabric-matrix adhesion. The part has sufficient self-supporting properties to maintain this shape and dimensions during subsequent processing steps. The laminate is then placed in a furnace and heated to approximately 538°C (538°C) for approximately 260 hours.
By slowly raising the temperature to 1000'F),
This was fully carbonized. The part was then cooled to ambient temperature over approximately 36 hours. The carbonized laminate was placed in a container in a vacuum oven and evacuated to 29 inches for approximately 1 hour. The part is then heated to about 185°C (365°F) for about 1 hour;
The re-impregnated resin was then allowed to melt and flow over the part. The reimpregnated resin is a resin made according to Example 7 of US Pat. No. 4,412,064. The vacuum is then released and the re-impregnated composite is then heated to about 224°C (435'F) for about 1 hour.
It was further heated for 2 hours. This further heat treatment cured the reimpregnated resin enough to prevent it from flowing in the next carbonization step.

The laminate was then placed in a furnace and carbonized by heating to about 538° C. (below 1000° C.) for about 48 hours.

The laminate was heated to about 3800'F for about 2 hours to further carbonize and graphitize the composite material. The laminate was then placed in a furnace and densified by chemical vapor deposition of carbon in the matrix for approximately 125 hours. The laminate was then machined to the desired size and shape and then densified a second time by chemical vapor deposition for about 125 hours. The densified parts are then approximately 42
50'F for about 3 hours and at this temperature for about 1 hour: tf11'! i do This further heat treatment was found to diffuse the 1M element into the chemical vapor deposited carbon. The laminate was then tested to meet the mechanical strength G
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However, the amount of boron in the second coated pulverized material was limited to 8.9% by weight. The laminate was tested and found to have the following mechanical properties.

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However, the composite was reimpregnated three times with resin-containing boron, with a 48 hour carbonization cycle at about 3000'F between each reimpregnation. The laminate was tested and found to have the following mechanical properties.

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A carbon/carbon composite was made according to US Pat. No. 4,321,298. The laminate was then tested and
It was found to have the following mechanical properties.

Cow-@00? ＋ BA〕COC'l"l■－ト＼＼＼＼＼＼＼l：io（社）（branch）（２）（社） oOjO代■ Therefore, in the five samples made according to the present invention, these containing boron The mechanical properties of the composite in terms of tension, deflection, compression and normalized tensile strength were shown to be better than those obtained with known methods.

These composites were also found to exhibit significantly improved oxidation resistance. In a test in an oxidizing atmosphere below about 1800 °C, Example 2 lost 45.4% by weight and Example 3 lost 32.03% by weight in 3 hours. On the other hand, a conventional carbon/carbon composite made by chemical vapor deposition has a loss of 84.92% by weight.

When coated with silicon carbide or other coatings, these composites exhibit the ability to work synergistically with the coatings by repairing the coatings at lower temperatures where these coatings are susceptible to oxidation.

Claims (5)

[Claims] (1) applying a coating of a flexible thermosetting resin to a fibrous carbon material that remains flexible after hardening; curing the flexible thermosetting resin; applying a boron compound to the fibrous carbon material; impregnating a second thermosetting resin comprising: at least partially curing the second thermosetting resin; assembling a plurality of the layers of the fibrous carbon material to form a laminate; Heating the above laminate to a temperature of -1 minute to carbonize the thermosetting resin, and filling the voids in the sown carbon/carbon composite phase with carbon/graphite material -C. carbon/carbon composite, and heating the carbon/carbon composite to diffuse the boron contained therein into the deposited carbon/graphite material. Manufacturing method for carbon composites. (2) The carbon/carbon composite material obtained after the heating to carbonize the thermosetting resin is treated with a resin containing atomically dispersed boron. Method. (3) The method of claim (2), wherein the composite material is further densified by chemical vapor deposition or coal cool pitch re-impregnation. 4. The method of claim 3, wherein the composite material is further heat treated to diffuse the boron into the carbon and carbonize the re-impregnated material prior to the heat treatment. (5) The method according to any one of claims (1) to (4), wherein at least one of the resins contains a refractory metal capable of reacting with boron to form a metal boride. .