Unusual behavior of thermal conductivity of a crystalline-NaCl-opal nanocomposite

An opal-based nanocomposite has been prepared with NaCl incorporated in its pores. The nanocomposite was produced by impregnating the opal with a NaCl solution at room temperature. Thermal conductivity of the nanocomposite has been measured in the temperature range 4.2-300 K. The effective heat conductivity of the nanocomposite was found to be equal to that of pure opal. The observed phenomenon can be explained by assuming that NaCl resides in opal pores in the form of noncontacting needles, thus precluding heat propagation through it. (C) 1998 American Institute of Physics.