Hydrothermal Synthesis of New Compounds with Novel Structures(1/3)

This research proposal is divided into two parts. The first part is about high-temperature, high-pressure hydrothermal synthesis of uranium silicates and germanates. The second part is about the synthesis of organically templated transition metal phosphates under mild hydrothermal conditions. Uranyl silicates are the most abundant group of uranium(VI) minerals and their structural chemistry has been extensively studied because an understanding of their structures may be a key to understanding the long-term performance of a geological repository for nuclear waste. We propose to synthesize new silicates and germanates of uranium, particularly those with unusual oxidation states and mixed-valence compounds. The synthetic method is mainly high-temperature, high-pressure hydrothermal reactions in gold ampoules contained in a high-pressure reaction vessel at 500-600 ºC and 1000-2000 bar. Their crystal structures, photoluminescence properties, XPS and XANES spectroscopy will be studied. The synthesis of organically templated transition metal phosphates has been extensively studied because of their interesting structural chemistry and potential applications. We will focus on the synthesis of compounds containing transition metals in reduced oxidation states by using Zn or Zn/Hg amalgam as a reducing agent under mild hydrothermal conditions. Their crystal structures and properties will be studied.