ON THE ORIGIN OF PERIODIC INCLUSIONS IN METALS FROZEN ONTO A MOVING SUBSTRATE

Metal coating application onto optical fibers by the freezing techniqu e is accompanied by the emergence of cavities empty of metal, which ar e situated at regular intervals along the fiber. This article attempts to explain the nature of this phenomenon, which is shown to be inhere nt in the freezing technique. The regular cavities are due to the inst ability of the melt flow during the phase transition process at the po int of contact of the cool fiber and the melt. Resonance of one of the eigen vibrations of the entrance meniscus with chaotic perturbations of the melt flow accounts for the periodicity of the cavities. The res ults of the theoretical analysis are confirmed by the experimental dat a. The conclusions of this analysis allow one to explain the presence of a similar phenomenon in the ''spinning'' process used for the fabri cation of amorphous-alloy thin ribbons. (C) 1997 American Institute of Physics.