Temperature programmed decomposition of thorium nitrate pentahydrate

Temperature programmed decomposition (TPD) of thorium nitrate pentahydrate has been studied using evolved gas analysis-mass spectrometry (EGA-MS) in t he temperature range 300-1200 K. A thermogravimetric (TGA) investigation wa s also carried out in the same temperature range. Complexity of the TGA dec omposition profile was resolved through use of EGA-MS data. The activation energies and pre-exponential factors were determined for various gas releas e stages from the fractional extent of decomposition plots. Residues left o ver after each decomposition stage were analysed using X-ray diffraction (X RD) and X-ray photoelectron spectroscopy (XPS). The XRD investigations reve aled formation of a nanocrystalline thoria intermediate product, ultimately agglomerating to a microcrystalline phase. The XPS investigations indicate d systematic alteration in the chemical environment around the thorium atom while the Th4+ oxidation state remained unchanged. This was further corrob orated from the analysis of shake-up satellites of Th (4f(5/2)) spectra. Th e O/Th ratios for various intermediate products were also determined. (C) 2 000 Elsevier Science B.V. All rights reserved.