JPH02221157A - Production of oxidation resistant high-strength carbon material - Google Patents

Abstract

PURPOSE:To obtain composite carbon material which has high strength and high density and is excellent in resistance to oxidation by mixing ceramics at a specified rate with carbonaceous substance for which oxidizing treatment has been previously performed and calcining this mixture. CONSTITUTION:1-90wt.% ceramics is blended with carbonaceous substance for which oxidizing treatment has been previously performed and this compound is calcined. Any of coal-based, petroleum-based or resin-based raw coke and calcined coke may be utilized as carbonaceous substance. Raw coke which has been coked at <=550 deg.C and has >=8% volatile matter is preferably utilized. Oxidizing treatment for carbonaceous substance is preferably performed at about 300-600 deg.C for raw coke and at about 600-1200 deg.C for calcined coke. Oxidiz ing treatment time is preferably regulated to about 30-90 minutes and controlled so that consumption by oxidation is regulated to a range within about 5-20wt.%. One kind or two kinds or more of SiC, B4C, SiO2 and B2O3, etc., are preferably utilized as ceramics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing an oxidation-resistant high-strength carbon material. More specifically, the method for producing an oxidation-resistant, high-density, high-strength carbon material in which ceramics are blended with an oxidized carbon material and sintered is carried out.

[Prior Art] Carbon materials are materials that have many excellent properties such as high temperature strength, thermal shock resistance, high thermal conductivity, good electrical conductivity, low heat*visibility, and chemical resistance. However, it has the major drawback of being easily oxidized under high temperature conditions. For example, when a carbon material is heated in air, it begins to oxidize at around 300°C and rapidly progresses above 600'C.

On the other hand, although carbon materials have excellent high-temperature properties, their use at high temperatures is limited to non-oxidizing atmospheres, and it has been difficult to use them in the atmosphere. As a method to compensate for these drawbacks of carbon materials, there is a method of impregnating them with phosphoric acid compounds or boric acid compounds in order to improve their oxidation resistance. A method of impregnating or coating with a glass film forming component, a method of blending silicon carbide and silicon iron with carbon or graphite, a method of blending a silicon III binder mainly composed of silicon carbide and silicic acid, etc. have been proposed. . However, the method of impregnating a phosphoric acid compound is a method of raising the oxidation initiation temperature of carbonaceous material by about 100 to 200°C at most, and does not provide a fundamental solution.

In addition, the oxidation resistance of the carbon material can be considerably improved by impregnating or coating it with glass film-forming components, but this depends on the glass film formed on the surface of the carbon material, so it may cause uneven coating, damage to the film, or There is a risk that oxidation will progress locally due to peeling caused by the difference in thermal expansion coefficient between the glass film and the glass film, and stable effects cannot be expected.

In addition, raw coke powder is mixed with boron carbide powder and silicon carbide powder and sintered to create an oxidation-resistant high-strength carbon material (Japanese Patent Laid-Open No. 59
-131576), carbon-ceramic composite VJ (Japanese Patent Laid-Open No. 140075/1983), which is a mixture of ground coke powder and ceramic powder, or a carbon-ceramic composite VJ (Japanese Patent Application Laid-Open No. 140075/1982), which is prepared by mixing or mixing and grinding and sintering ground coke powder and ceramic powder.
No. 2) is also known. Furthermore, a heat-resistant fan (Japanese Patent Application Laid-Open No. 60-60299) has been proposed using a material in which silicon carbide, boron carbide, and aluminum oxide are mixed with coke.

Each of these has achieved a certain degree of oxidation resistance and high density, but the present invention further improves these methods and provides a high-density carbon-based composite material with further excellent oxidation resistance. It is something.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for manufacturing a carbonaceous and ceramic composite material that has high strength, high density, and particularly excellent oxidation resistance.

[Means to solve the problem]

The present invention is a method for manufacturing a high-density, high-strength composite material by blending 1 to 90% by weight of ceramics with carbonaceous material and sintering the mixture, which is characterized in that the carbonaceous material is previously oxidized. This is a method for producing oxidation-resistant, high-strength carbon materials.

At first glance, it may seem contradictory to apply oxidation treatment to impart oxidation resistance to carbon materials, but the inventor of the present invention dared to carry out this process and found that the result was unexpectedly high density, high strength, and oxidation resistance. We were able to obtain a composite material with excellent properties.

The carbonaceous material used in the present invention may be coal-based, petroleum-based or resin-based raw coke, or roasted coke;
Preferably, raw coke is coked at a temperature below 0.degree. C. and has a volatile content of 8% or more.

By using raw coke, it is possible to sinter without using binders or other additives that cause porosity, resulting in a high-strength composite material with extremely low porosity after sintering. This is because it can be obtained.

However, the composite material of the present invention is not limited to this, and it is effective even if the calcined coke is subjected to oxidation treatment.

The carbonaceous powder has a diameter of 20 μm or less, preferably 5 μm or less.

The oxidation treatment for carbonaceous material, which is a feature of the present invention, is preferably performed on the carbonaceous material after pulverization.

The oxidation temperature must be changed depending on the carbon quality, but 3
The temperature range is 00 to 1.200°C.

It is desirable to carry out the process at a low temperature for raw coke, and at a high temperature for roasted coke. For raw coke, the temperature is preferably 300 to 600°C, and 400 to 50°C.
It is more preferable to carry out the reaction at 00°C.

The calcining of coke is preferably carried out at 600 to 1,200°C, more preferably at 800 to 1,000°C.

The oxidation treatment time is preferably 30 to 90 minutes and controlled so that the oxidation consumption is in the range of 5 to 20%.

When the amount of oxidation consumption is less than 5%, the effect of the oxidation treatment is insufficient, and when the amount of oxidation consumption exceeds 20%, it is economically unfavorable.

Ceramic materials used in the present invention include carbides, oxides,
Nitride etc. are used, but silicon carbide (S i C)
, boron carbide (B4C), silicon oxide (SiO□),
Boron oxide (B203) and the like are suitable, alone or in combination
More than one type may be mixed.

The blending ratio of ceramics to carbonaceous material is 1 to 90 parts R
% range. Preferably it is 10 to 30% by weight.

If it is less than 1% by weight, oxidation resistance at high temperatures cannot be expected;
If it exceeds 0% by weight, the hardness of the composite material will increase, but the thermal shock resistance will be inferior to that of carbon materials, which is not preferable.

The size of the ceramic particles used is the same as that of the carbon material.
It is preferably 0 μm or less, preferably 5 μm or less.

By mixing the powder materials prepared in this manner, hot press molding or molding, and firing, a composite material with extremely low porosity (high strength and oxidation resistance) can be obtained.

[Effect]

It is not clear why pre-oxidation treatment of carbonaceous material gives sintered composite materials high density, high strength, and excellent oxidation resistance, but oxygen-containing groups are adsorbed on the carbonaceous surface due to oxidation treatment. During the molding reheating process, the adsorbed oxygen-containing groups degas with CO or CO2, activating the coke surface and strengthening the bonds between powder particles and making the composite more dense. It is presumed that this is because it is less likely to occur from within.

〔Example〕

EXAMPLES The present invention will be explained in more detail below with reference to Examples, but the present invention is not limited to these Examples.

(Example) Carbon-based raw coke (average volatile content: 11%) coked at about 500° C. was crushed using a show crusher and an impact crusher to form powder with an average particle size of 10 μm. This coke powder was air oxidized at 350-400°C for 40 minutes.

Boron carbide powder (average particle size 5 μm) and silicon carbide powder (
(average particle size: 5 μm) were added in the proportions shown in Table 1, mixed with a mixer, and then CEP molded at a pressure of 1 t/cj.

Further, it was fired at 2,000°C in an inert atmosphere.

The sintered body was cut into 10×10×60 (layers), and an oxidation test was conducted at 1.000° C. for 2 hours in an air flow (4j/sin).

(Comparative Example) As a comparative example, a case where no air oxidation treatment was performed and no ceramics were added (Comparative Example 1), and a case where no air oxidation treatment was performed and ceramics were added (Comparative Example 2) were shown together.

〔Effect of the invention〕

According to the present invention, the composite material manufactured using oxidized and GL-manufactured carbon powder has high strength, high density, and excellent oxidation resistance, as well as high temperature strength and thermal shock resistance, which are characteristics of carbon materials. Therefore, it can be expected to be used in ceramic materials, chemical industry materials, aerospace materials, etc.

Claims (1)

[Claims] In a method of manufacturing a high-density, high-strength composite material by blending 1 to 90% by weight of ceramics with carbonaceous material and sintering the mixture,
A method for producing an oxidation-resistant high-strength carbon material, characterized by using carbon material that has been oxidized in advance.