TEXTURE ASSESSMENT OF THORIA AS A FINAL DECOMPOSITION PRODUCT OF HYDRATED THORIUM NITRATE AND OXYCARBONATE

Th(NO3)(4) . 5H(2)O and ThO(CO3). O.5H(2)O were used as parent compoun ds for the formation of ThO2. Thermal processes involved during the co urse of decomposition up to 500 degrees C in air were monitored by the rmogravimetry, differential thermal analysis and infrared (IR) gas pha se analysis. Intermediate and final solid products were characterized by IR spectroscopy and X-ray diffractometry. The results showed that T h(NO3)(4) . 5H(2)O is completely decomposed to ThO2 at 300 degrees C v ia three unstable intermediates: Th(OH)(NO3)(3) at 165 degrees C; ThO( NO3)(2) at 210 degrees C and ThO1.75(NO3)(0.5) at 250 degrees C. Simil arly, ThOCO3 . 0.5H(2)O is completely decomposed to ThO2 at 300 degree s C via the unstable intermediate ThO1.5(CO3)(0.5) at 160 degrees C. S urface texture measurements and scanning electron microscopy showed th at ThO2, the final decomposition product at 500 degrees C of both Th(N O3)(4) . 5H(2)O and ThO(CO3). O.5H(2)O is crystalline and has surface areas of 32 m(2) g(-1) and 56 m(2) g(-1), respectively. ThO2 formed fr om the nitrate is mainly microporous. However, ThO2 obtained from the oxycarbonate contains different types of porosities.