Single crystals of barium oxalate have been grown using gel method at ambient temperature. Thermal characteristics and kinetic parameters of barium oxalate crystals were determined by thermo-gravimetric (TG) analysis ...Single crystals of barium oxalate have been grown using gel method at ambient temperature. Thermal characteristics and kinetic parameters of barium oxalate crystals were determined by thermo-gravimetric (TG) analysis under non-isothermal heating conditions. The pyrolysis experiments were performed with increasing temperature up-to 600℃ at heating rate of 5℃, 7℃ and 10℃ in nitrogen gas atmosphere. The pyrolysis curve showed that loss of mass took place mainly in the range of 220℃ - 400℃. At higher temperature there was a significant mass loss due to decomposition of oxalates. Ozawa and Coats & Redfern methods were used to determine the apparent activation energies of material degradation. The apparent activation energies for barium oxalate crystals were obtained 187.42 KJ·mol-1 and 185.4 KJ·mol-1 for the respective methods.展开更多
In the present study, the selection of an etchant for a particular crystal was purely made on empirical basis. The gel grown barium oxalate crystals were etched by HCl, HNO3, BaCl2, NH4Cl, and NH4Cl-HCl solutions. Mic...In the present study, the selection of an etchant for a particular crystal was purely made on empirical basis. The gel grown barium oxalate crystals were etched by HCl, HNO3, BaCl2, NH4Cl, and NH4Cl-HCl solutions. Micro-topographical studies have been made and it was found that elongated triangular etch pits and pits within pits were formed. Rectangular growth layers in the form of staircase and leaf like dendrite pattern were seen. Kinetics of etching was studied. Quantitative estimation of dissolved crystals in etchants was used for the determination of activation energy of reaction and pre-exponential factor with the help of Arrhenius equation.展开更多
文摘Single crystals of barium oxalate have been grown using gel method at ambient temperature. Thermal characteristics and kinetic parameters of barium oxalate crystals were determined by thermo-gravimetric (TG) analysis under non-isothermal heating conditions. The pyrolysis experiments were performed with increasing temperature up-to 600℃ at heating rate of 5℃, 7℃ and 10℃ in nitrogen gas atmosphere. The pyrolysis curve showed that loss of mass took place mainly in the range of 220℃ - 400℃. At higher temperature there was a significant mass loss due to decomposition of oxalates. Ozawa and Coats & Redfern methods were used to determine the apparent activation energies of material degradation. The apparent activation energies for barium oxalate crystals were obtained 187.42 KJ·mol-1 and 185.4 KJ·mol-1 for the respective methods.
文摘In the present study, the selection of an etchant for a particular crystal was purely made on empirical basis. The gel grown barium oxalate crystals were etched by HCl, HNO3, BaCl2, NH4Cl, and NH4Cl-HCl solutions. Micro-topographical studies have been made and it was found that elongated triangular etch pits and pits within pits were formed. Rectangular growth layers in the form of staircase and leaf like dendrite pattern were seen. Kinetics of etching was studied. Quantitative estimation of dissolved crystals in etchants was used for the determination of activation energy of reaction and pre-exponential factor with the help of Arrhenius equation.
