Chapter 15 - Metal-Coated Fibers

Abstract

This chapter provides information on the “freezing” technology and the properties of metal-coated fibers obtained by this technique. In this technique, the fiber passes through a layer of molten metal. When the temperature of the melt is close to the melting point of the metal and the temperature of the fiber is somewhat lower, a layer of the metal can freeze on the surface of the fiber. To obtain a stable uniform metal film, the duration of the contact of the fiber with the molten metal in the metalizer should be shorter than the time of fiber heating to the metal melting point. Otherwise, the frozen layer will melt again, and the fiber will pass through the metalizer without any coating. Cavities in the glass–metal interface are inherent in the freezing technique. Usually they appear regularly with a period comparable to the fiber diameter. Only metals with a comparatively low melting point can be applied by the freezing method without a noticeable problem with the fiber strength due to the reaction of the melt with silica. Very high stresses can arise in the metal film and in the silica fiber during cooling after metal application because of a big difference in thermal expansion coefficients of silica and the metal.