0020-1685/03/3901- $25.00 © 2003 MAIK “Nauka /Interperiodica” 0077 Inorganic Materials, Vol. 39, No. 1, 2003, pp. 77–81. Translated from Neorganicheskie Materialy, Vol. 39, No. 1, 2003, pp. 88–93. Original Russian Text Copyright © 2003 by Churbanov, Shaposhnikov, Skripachev, Snopatin. INTRODUCTION Arsenic selenide fibers are commonly drawn from a melt flowing through a cylindrical or annular channel. Optical fibers must meet the following geometric requirements: the core and cladding must be coaxial and have preset diameters throughout the fiber length. The geometric parameters of fibers depend on the rate of melt outflow from the drawing nozzle. To obtain fibers with controlled properties, it is necessary to know how the melt flow rate varies with temperature and pressure. Here, we report our findings on the rate of As 2 Se 3 melt outflow from cylindrical channels in the ranges of temperatures and excess gas pressures over the melt that are typical of fiber drawing processes. The flow of molten As 2 Se 3 in cylindrical channels has not been studied previously. The viscosity of As–Se glasses was determined by indentation (170–278°C) [1] and by the disc oscillation damping method (500– 750°C) [2]. EXPERIMENTAL The unit we used to measure the melt outflow rate (Fig. 1) includes a quartz container (1) ending in the nozzle to be examined, a temperature-controlled fur- nace (2), a gas pressure control system (3), and a fiber takeup spool (4). The furnace (2) is a massive resis- tance-heated copper block. The furnace temperature was maintained within ± 3°ë. The pressure of the inert gas (high-purity argon) over the melt was maintained with an accuracy of ±10 3 Pa. A rod of the glass to be examined was placed in the quartz container (1), and the container was mounted in the furnace (2) preheated to the set temperature. The furnace temperature was measured with two Chromel– Alumel thermocouples (5). The container was con- nected to the gas pressure control system (3) through a seal assembly (6), and the desired gas pressure over the solution was established. The initial height of the liquid column was 150 mm. The outflowing melt was collected as a fiber wound on Flow of Molten Arsenic Selenide in a Cylindrical Channel M. F. Churbanov, R. M. Shaposhnikov, I. V. Skripachev, and G. E. Snopatin Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, ul. Tropinina 49, Nizhni Novgorod, 603950 Russia e-mail: churbanov@ihps.nnov.ru Received July 3, 2001; in final form, July 15, 2002 Abstract—The flow rate of molten arsenic selenide in cylindrical channels is measured at channel diameters of 3.0 to 5.5 mm, channel lengths of 40 to 120 mm, temperatures of 285–320 and 375–470°C, and inert gas gage pressures of up to 1.5 × 10 5 Pa. It is found that there is a motionless melt layer on the inner surface of the channel. For a channel 4.6 mm in diameter, its thickness is 0.7 mm at 290°C and 0.1 mm at 420°C. In the tem- perature range 280–315°C, there is a threshold gas pressure below which the melt does not flow. Partial crys- tallization may occur in the flowing melt. Its effect on the melt flow rate grows as the holding time at 270–320°C increases. The data obtained can be used to choose conditions for producing As 2 Se 3 optical fibers by the cruci- ble method. G 1 2 3 4 5 6 7 8 Fig. 1. Experimental setup for studying the flow of molten glass through a cylindrical channel: (1) container with a drawing nozzle, (2) furnace, (3) gas pressure control sys- tem, (4) fiber takeup spool, (5) thermocouples, (6) seal assembly, (7) pressure gage, (8) gas pressure stabilizer.