Structural and wettability properties of titanium nitride (TiN) thin films for different annealing temperatures have been characterized, and critical parameters have been identified. TiN thin films were deposited onto the silicon substrates by using the magneto-sputtering technique for two different powers, 150 W and 350 W. Subsequently, the films were annealed in the air at 573–973 K for the duration of 1 h. The X-ray diffraction spectra showed the appearance of titanium dioxide (TiO2) above 773 K temperature (termed as transformation temperature). The relative intensity of the TiO2 peaks rapidly increase with the temperature. The thin and dense oxide overlayer appeared at 773 K, and the thicker oxide layer was observed at 973 K. Surface roughness is observed to increase with the increase in annealing temperature but with the limiting value at 773 K; after that, the roughness decreases because of the stable formation of TiO2. Similarly, with an increase in temperature, the hydrophobic nature of thin films becomes more significant; however at 973 K, the formation of TiO2 declines the hydrophobic nature, and thus the surface energy increases. Transformation temperature is also found to be responsible for the reduction in grain size and compressive strain of the thin film.
Uranium mills following the sulfuric acid leaching route produce Uranium Peroxide (UP) as uranium ore concentrate (yellow cake), which is then refined to produce nuclear grade uranium products. Whereas the mills processing ores by alkaline leaching route generate Sodium Diuranate (SDU) as yellow cake, which commonly contains impurities viz. Zr, SiO2, Mo, Organic Carbon (OC). These impurities form muck, interfacial crud and acid insolubles during digestion and solvent extraction (SX) stages in refining process. Hence, SDU needs to be pre-treated before processing in the uranium refinery. India has substantial U reserves (>50%) hosted in carbonate minerals matrix which obviously need alkaline processing for extraction of U. In the present study, the origin of impurities in a SDU produced in an Indian Uranium mill was traced back to the mineralogical composition of the ore, chemical reactivity of minerals to the reagents,and build-up of impurities in process streams due to existence of multiple recycle streams in the milling process flowsheet. A process scheme has been developed for converting SDU into highly pure Heat Treated Uranium Peroxide (HTUP). The scheme involves digestion of SDU in sulfuric acid medium followed by separation of insolubles from the liquor which is later subjected to pH controlled U-peroxide precipitation process. The U-peroxide formed was heat treated to drive-off active oxygen and water of crystallization. A HTUP product assaying about 91% U3O8 was produced from an impure SDU assaying 74% U3O8. Process has been demonstrated at large scale (about 100 kg/batch) and engineering data and scale up parameters have been generated.
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