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

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.