Determination of activation energies of the U(Mo)/Si and U(Mo)/Al solid state reaction using in-situ X-ray diffraction and Kissinger analysis

The solid state reaction between U(Mo) and Si, leading to the formation of silicides, has been studied using in-situ X-ray Diffraction. Samples were prepared by sputter depositing Si in thin layers on U(Mo) substrates (8 wt% Mo) and vice versa. In a similar way the reaction between U(Mo) and Al has been studied using U(Mo) substrates covered with a thin layer of Al. The samples were heated to temperatures up to 950 C in a static purified helium atmosphere. Even though the measurements were hampered by the undesired oxidation of uranium, the formation of various silicides and aluminides could be observed. Kissinger analysis on ramp anneals with ramp rates of 0.2, 0.5, 1 and 3 C/s have been performed to investigate the kinetics of the formed silicides. Using this method, the apparent activation energy for the different silicide formation reactions was deduced. Using the effective heat of formation rule, a prediction was made on the first phase formed and the subsequent phase sequence. A good agreement was found between the measurements and prediction.