Computation of Temperature Distribution in Infiltration of Metal in Opal Using a Graphite Furnace Heating Assembly
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Computation of Temperature Distribution in Infiltration of Metal in Opal Using a Graphite Furnace Heating Assembly Hossein Golnabi, Mahmood Ghorannevis and Nahid Chaboki Plasma Physics Research Center, Islamic Azad University, P.O. Box 14665-678, Tehran, Iran ABSTRACT The use of high temperature furnace assembly used in high–temperature high-pressure machine is proposed and modeled for the infiltration process of metals in opals. The goal here is to provide useful information about the temperature distribution inside the capsule cell in order to save some time and reduce synthesis cost in the real infiltration process. The heat conduction equation is solved for a cylindrical geometry and the variation of the temperature as a function of time and radius distance are reported. The 2-D finite element method for a symmetrical assembly is used and the temperature dependence of heat conductivity of multi elements is considered in the calculations. Temperature dependence of heat conductivity of different elements involved in infiltration process are modeled and also reported here. Such information concerning the temperature distribution inside the infiltration assembly is helpful for both the equilibrium studies and transient conditions. Results of such study help the users to properly select the appropriate temperature gradient for the steady state and transient situations. Such temperature and pressure adjustments are helpful for a successful melt infiltration process. INTRODUCTION In recent years metallic photonic crystals have shown many interesting results [1]. It has been mentioned that by decreasing the characteristic size of crystal periodicity, the position of the metallic photonic band gap may be shifted from the microwaves to terahertz frequencies and further into infrared spectral range. The method of the fabrication of opals and the melt infiltration is discussed for the network and cermet topologies. In that report the infiltration of metals in opals are reported in which a special dye assembly is used for the melting and infiltration process. It has been shown that the infiltration process is sensitive to the heating temperature and pressing pressure. The use of high temperature furnace assembly used in high– temperature high-pressure machine is proposed and modeled for such infiltration process. In equilibrium experiments using piston-cylinder a large sample volume with homogeneous temperature distribution is desired. On the other hand, for experiments at transient conditions a true knowledge of the temperature distribution is needed to drive the processes such as induced melt migration or diffusion. With such information and the experimental results provided by different thermocouples in the heating assembly it is possible to control the required temperature distribution in the system with graphite heating assembly. There has been a great deal of interest in the metallic photonic crystals in recent years. Different reports on the synthesis, characterization, and possible applications of such new ma
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