Ichiro Shiota1 and Osamu Watanabe1
1National Research Institute for Metals, Tokyo
Microstructures of a nickel coated carbon fiber at high temperatures were studied by X-ray diffraction and an electron probe microanalyser, and they were compared with the results of observations by a scanning electron microscope.
By holding carbon fiber coated with nickel at a high temperature over 700°C, a white ring moving to the center of fiber was observed in the cross section of the carbon fiber.
The white ring was confirmed to be nickel metal, not nickel carbides, by X-ray diffraction and electron probe microanalysis. The area of the carbon fiber passed by the nickel ring showed a flaky appearance, and the carbon was graphitized at the area. The flaky area was oriented less preferably than that in the intact area.
It seems reasonable to consider the moving of the nickel ring accompanied by graphitization of the carbon fiber in such a way that the carbon atoms dissolve into nickel metal from the less graphitized part, diffuse in it, and deposit as graphite on a comparatively well graphitized part of the carbon fiber. As the deposited graphite is stable than carbon in the intact area, the nickel ring dissolves carbon atoms inside of the ring and discharge them as graphite outside of it, thus the nickel ring moves to the center of the carbon fiber and finally aggregates there as a white speck.
Please do not copy without permission.