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Abstract In the present thesis one used differential thermal analysis-thermogravimetery techniques, XRD, III ab s orp t t on and nitrogen gas adsorption .to study the t he r-rna I d ecompos I tion of nickel acetate t-e t r auy dr a te and uranyl acetate d i hy d r-a t e . A s uunua ry or tmport a nt re s uI t s and conclusion of various parts e f the present thesis is given below. • The metal acetate used wet’e, nickel acetate tetrahydrate (HIJII), and urany I acetate d i hy dr-a t e (Fluka), reagent grade, used without further purification. The starting materials were sieved and samples of particle size less than 125!Jm used for IJTA-TGexperimentals. The resul t s show the thermal d ecompoa I tLon where reaction of nickel acetate tetrahydrate. IJTA-TG studies showed that nickel acetate tetrahydrate loses weight in two endothermic step. in atmosphere of ni t rog en. The first step endotllermic peak is in the range of 65 to 130°C and is due to the loss of wat er- of crystallization. Where as the second endothermic peak is in the range 260 to 3’75°C and is due to decomposition of atlhydrous salt to give nickel oxide, acetone and CU2· The DTA curve showed a dented endothermic peak at about 330°C, which indicates the main acetate decomposition Occur in at least two stages. The second stage of the anhydrous salt may indicate the presence of an intermediate mixed acetateoxide salt or may indicate the product of carbonate. In air, the first decompositon step is characterized by a sharp endothermic peak in the range of 70-1300c and is again attributed to the loss of water crystallization. Whereas, the second decomposition step is exottlermic peak at about 270- 290°C. It can be concluded that the decomposi tion of the acetone vapor occures on contact with the oxygen, with the consequent marked endothermal ac tivity. The DrA curves show that the dehydra tion occure in one step. Hence, the decomposition of step II could involve the libration of acetone and carbon dioxide. However, the intermediate mixed acetate oxide salt followed by decomposition to oxide. The kinetics ·of the isothermal decomposition of nickel acetate tetrahydrate were studied in nitrogen and air atmosphere at different temperature range. The a-t data were analyzed by the method of L.Il. according to the various kinetic equa tions. The results show that the best fit data is obtained according to phase boundary ---~- - -- - - --- -~---- ----- ----------------- 141 controlled reaction (H 2 random nucleation model and H3 function), and A2· Other models gave a less statisfactory fit to the experimental data. Also, we found that H2 model gave highest correlation coefficient. The activation parameters for the decomposition of nickel acetate tetrallydrate were calculated on the basis of R 2’ R3 models. The activation energies of the dehydration step were found to be 105 -I and 90 kJ mol for air and ni trogen atmosphere. The activation energies equals 114 kJ mol -1 and 205 k J 1001-1 in air of the isothermal kinetic in nitrogen atmosphere, atmosphere. The kinetic analysis on the non-isothermal decomposition of nickel acetate tetrahydrate was studied. The analysis of TG curves assuming HZ function, which gave the highest correlation coeficient in the analysis of isothermal data and made a cri tical comparison of the three dynamic methods: Diefallah’s composite method, Coats-Redfern method and Ozawa integral method. The kinetics of the decomposition reaction on the nickel acetate tetrahydrate were studied in nitrogen and azr- at dLf’f’er-en t heating rate-s of Z, 5, 10, 15, and 20oC/min. The activation parameters were calculated according to HZ & ”3 modeL 142 Wherever, Ozawa method gives a more satisfactory kinetic analysis than that of the other methods. The thermal decomposition reaction of urany,l acetate dihydrate were carried out in atmosphere of nitrogen and air. DTA-TO studies showed that urany 1 acetate dihydrate loses weigh t in two endothermic peaks in nitrogen. The first step is a broad endothermib peak in the range 90-130oC corresponding to the dehydra tion stage. The second s t.ep (decomposition step) is also broad endothermic peak in range of 320-370oC. In air, DTA-TO showed that uranyl acetate dihydrate loses weight in two steps. The first step is characterized by a broad endothermic peak in range of 95-130oC. The second step starts at 300°C and is characterized by exothermic peak at 335°C. However, decomposi tion of the with ace tone vapor occures on contac t wi th oxygen consequent marked exothermic activity. The kinetic of the isothermal of decomposition r eac tion of urany I aceta te dihydra te were studied in nitrogen and air at different temperature range. The a -t data were analysed by the method of L. R. according to. the various kinetic equations. The result show tha t the bes t fi t of da ta is obtained for random nucleation models and phase boundary controlled model, other models give a less satisfactory fits. The activation parameters for the decompposition of uranyl acetate dihydrate were calculated on the basis of A2 and A 3 models. The kinetics analysis of the non-isothermal decomposl tion of uranyl acetate dihydrate was stucJied. The analysis of TO cur-v es assuming A 2 function, which gave the highest correlation coefficient in the analysis of isotllermal data and made a critical comparison of the three dynamic method: Diefallah’s composite, Coats-Refern, and Ozawa integrals methods. The kinetics of the decomposi tion reaction on the nickel acetate tetrahydrate Were studied in nitrogen and air at different heating rates of 2, 5, 15, 200C/min. Some IR, XRD, suraface area measurements were carried out for different heat treated samples of nickel acetate and uranyl acetate to support the TO dynamic measurements. |