JPS5870770A - Coated carbon fiber - 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 carbon fibers with high tensile strength.

Conventionally, carbon fiber has been used as a material for reinforced plastics (FR, P) because it has particularly excellent specific strength and can be produced in large quantities at low cost. Furthermore, since it has high high-temperature strength, it is expected to be used as a material for fiber-reinforced metals (PR,M).

Generally, the most effective way to improve the strength of fibers is to reduce the probability of defects by making them thinner. However, if they were made too thin, the strength per unit area would be high, but the strength of each piece would be low, making handling extremely difficult. In particular, when a metal is used as a matrix, it is extremely difficult to prevent the metal from wrapping around between the aligned fibers.

The inventors have arrived at the present invention as a result of various studies on methods of reinforcing fibers without simply reducing the fiber diameter. When carbon fiber is used for FRP, FR, and M, it is often desirable to coat the surface with ceramic to improve reactivity and compatibility with matrix plastics and metals. The present invention is based on the discovery that the above-mentioned problems can be solved by coating the surface of carbon fibers with amorphous ceramic.

Traditionally, ceramics have strong characteristics such as almost no deformation before breaking and a higher Young's modulus than other materials.
Various attempts have been made to coat ceramics such as ceramics. However, it cannot be said that it is sufficiently effective in improving strength. This is thought to be because the ceramic is sensitive to notches and the unevenness of the surface did not contribute to improved strength.

The inventors thought and considered that the strength of the coated carbon fiber could be improved by making this ceramic tougher.
It has been found that a significant effect can be obtained by making the entire ceramic layer or the outermost layer amorphous. As mentioned above, it is important that the outermost surface of the coating layer is amorphous because fiber breakage occurs from the surface due to notches.

Of course, the effect remains the same even if the entire coating layer is amorphous.

The ceramic to be coated on the surface is An203°S.
iC,S i 8N,, TiC,TiN, WC,T
Single units such as aC, Sialon (81AJON), (T
As a result of experiments, it was found that compounds such as i,W)C,Ti (CIN) are suitable.

If the thickness of the ceramic layer is less than 0.1μ, a reinforcing effect will be obtained, but if it is more than 20μ, the strength will decrease.

To coat the amorphous ceramic layer, CV
D method, plasma CVD method, ion blating method,
Any non-buttering method is possible, but if there is a difference in thermal expansion coefficient from the ceramic layer, it is preferable to coat at a low temperature.

When the coated carbon fiber of the present invention is used as an FRM, the outer layer may be further coated with a metal and then bundled and hot pressed, but the strength of the fiber is determined by the ceramic layer.

A detailed explanation will be given below using examples.

Example 1 A carbon fiber having a diameter of 10 μm was coated with a 2 μm layer of AjB08 by an ion blating method. As a result of surface analysis using X-ray diffraction, Auger spectroscopy, etc., it was found that this Al2O8 layer was amorphous4. When the tensile strength was measured, the product of the present invention had a strength of 280 Kt/m B, whereas the uncoated carbon fiber had a tensile strength of 175 Kt/m B.
Met.

Example 2 Carbon fibers having a diameter of 20 μm were coated with SiC having the thickness shown in Table 1 by plasma CVD. As a result of the analysis, it was confirmed that it was in an amorphous state.

The results of measuring the tensile strength of these materials are shown in Table 1, and it can be seen that there is a □ effect from 0.1 μm onwards, and that the strength decreases when the tensile strength exceeds 20 μm.

Example 3 Carbon fiber with a diameter of 20μ was coated with 5
Coated with μ S r a N 4 . In this case, three types of crystal states shown in Table 2 were obtained by changing the conditions. The tensile strength of each is shown in Table 2.

Example 4 Carbon fibers having a diameter of 10μ were coated with 2μ of various ceramics shown in Table 3 by sputtering, and their tensile strengths were compared. In this case, all layers are in an amorphous state.

Claims (1)

[Claims] (1) Carbon fiber is used as the core material and A603, Z
rOSiC, Si N 5iAjl (ON), and periodic table Ill 8 411
Va, Va, coated with carbides, nitrides, carbonitrides of group VIa elements, or one or more of these compounds,
A coated carbon fiber characterized in that at least the outermost layer of the coating layer is amorphous. (2. A coated carbon fiber according to claim (1), characterized in that the thickness of the coating layer is 0.1 μm or more and 20 μm or less.