Mechanical Strength of Low-Dimension Class Fibers
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MECHANICAL STRENGTH OF LOW-DIMENSION CLASS FIBERS K.A. CERQUA, E.C.BEHRMAN AND W.C. LACOURSE Institute for Ceramic Physics New York State College of Ceramics at Alfred University Alfred, New York 14802 ABSTRACT Chalcogenide glasses present a unique opportunity for the study of the effect of dimensionality of the properties of amorphous systems. Presented here are preliminary results of experiments on fibers of these materials. Strength in these fibers is related both to dimensionality, which is a continuously variable function of composition and to drawing conditions, which produce ordering. A simple theoretical model for the ordering effect is proposed and discussed. INTRODUCTION Considerable interest in new materials for infrared transmission at 10.6ji has sparked research in extending the capabilities of chalcogenide and more recently chalcohalide glasses. While improvement to the optical properties of these materials will determine the ultimate applicability of these glasses, the long-term usefulness of the materials in fiber form will be determined by inherent properties such as strength and durability. In recent research at Alfred we have examined the structural and mechanical properties of arsenic selenide[1] and Ge-Sb-Se[2] glasses. We are now investigating iodine-based chalcohalide (so-called heavy-metal halides or TeX glasses) materials in both bulk and fiber form. These glasses can provide transmission well past 1 5 p. Replacement of constituents with heavier halide atoms not only increases the transmission, but decreases impurity-induced attenuation by reducing the tendency of formation of hydride and oxide species in the materials[3]. While the infrared transparency of chalcohalide materials makes them promising candidates for use in this spectral range, numerous limitations may restrict their practical use. In examining Te-Se-Br and Te-Se-I glass systems, Lucas[4] showed a maximum T5 obtainable for these materials of about 75 0 C with a Se/Te ratio of 3/2 for bulk samples. T0 in these materials decreases with increasing Se content with values routinely on the order of 50-65°C for bulk materials and less (40-50°C) for Te 2 Se 1 _2 =I2 (x = 1 - 4) compositions in fiber form. The low T, allows for considerable time dependence of properties following processing. Low temperature stress and structural relaxation processes occur over short time scales at room temperature, making it impossible to assign unique values to structure-dependent properties. Consideration of the above-mentioned processes is essential in evaluating the effect of processing conditions of fibers on their observed strengths. This paper will not consider these relaxation processes, but, rather, concentrate on those inherent material phenomena which we would expect to determine the strength of these low-dimensional materials. We propose a simple one dimensional model which describes the concept of ordering which occurs during fiberization of these glasses. The
Mat. Res. Soc. Symp. Proc. Vol. 172. ©1990 Materials Research Society
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