| Popis: |
The choice of a suitable parameter to characterise the sintering behaviour of different powders is important from scientific as well as technological considerations. Scientifically, it will be very interesting to understand the physical basis for the difference in the reactivity of the different powders of the same material which governs their sintering characteristics. Despite nearly identical or only marginal differences in particle size and surface area, reactivity variation among the powders of the same material can bring about significant differences in their sintering behaviour. Technologically, the assessment of the sintering characteristics is of great importance in controlling the final density and the quality of the sintered product. The UO2 powders are usually prepared through the decomposition of ammonium diuranate or carbonate. The powders prepared through decomposition at lower temperatures sinter to higher densities at relatively lower temperatures and viceversa. In general, lower the temperature of decomposition, higher is the surface reactivity. Uranium dioxide powders produced through decomposition of ADU at temperatures greater than 1273 K are almost inactive and can be sintered only with great difficulty. It has been shown1,2 earlier that the adsorption of metal ions on the surface of uranium dioxide powder taking place in an aqueous medium can distinguish clearly the sintering characteristics of various UO2 powders with varying surface reactivities. In a survey of the adsorption characteristics of several elements1, it was found that manganese, iron and niobium were adsorbed strongly and provided satisfactory distinction between different grades of powder. Detailed studies on manganese have already been reported2. In the present report, adsorption characteristics of iron on uranium dioxide powders of varying activity are presented. In the previous cases, the powders were prepared by decomposition of ADU in the laboratory. The materials for the present series of experiment were obtained from Nuclear Fuel Complex, Hyderabad and were prepared by the decomposition of ADU. |
