Special features of the tungsten wire heat transfer and the WO3 nanoparticle synthesis in supercritical water

Abstract

Special features of the tungsten wire (TW) heat transfer in supercritical water at P = 25 MPa and T ≤ 923 K are investigated, including the conditions of (WO3)n nanoparticle formation on the tungsten wire surface with the reaction kn〈W〉 + 3knH2O = k(WO3)n + 3knH2. Values of the heat transfer coefficient as a function of oxidation time and temperature were determined using the method of electric current flash heating of the tungsten wire. It has been found that due to WO3 dissolution in supercritical water, there occurs oxide recondensation from the tungsten wire surface onto other design elements of the setup, which is accompanied by formation of monoclinic and rhombic WO3, and also monoclinic FeWO4.