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Thermal dehydration kinetics of a rare earth hydroxide, Gd(OH)3

All Rights Reserved. Thermal dehydration kinetics of a rare earth hydroxide, Gd(OH)3. Chang, Chengkang; Mao, Dali (The State Key Laboratory of Metal Matrix Composites, School of Materials Science and Engineering, Shanghai Jiaotong University, Shanghai 200030, Peop. Rep. China). International Journal of Chemical Kinetics, 39(2), 75-81 (English) 2007 John Wiley & Sons, Inc. CODEN: IJCKBO. ISSN: 0538-8066. DOCUMENT TYPE: Journal CA Section: 67 (Catalysis, Reaction Kinetics, and Inorganic Reaction Mechanisms) Section cross-reference(s): 69, 75 This paper reports the synthesis, characterization, and dehydration kinetics of a rare earth hydroxide, Gd(OH)3. Uniform rod-like Gd(OH)3 powder was prepd. by a colloidal hydrothermal method. The powder thus obtained dehydrated into its oxide form in a two-step process, where cryst. GdOOH was obtained as the intermediate phase. Crystal structure study revealed a monoclinic structure for GdOOH, with space group P2/1m and lattice parameters a = 6.Several substances like 16469-18-4 may be metioned in this study.0633, b = 3.7107, c = 4.3266, and b = 108.669. The first-step dehydration follows the F2 mechanism, while the second step follows the F1 model, indicating that both the steps are controlled by nucleation/growth mechanism. The activation energy Ea and frequency factor A are 231 ± 12 kJ/mol and 2.08 ′ 1018 s-1 for the first step and 496 ± 32 kJ/mol and 7.88 ′ 1033 s-1 for the second step, resp. Such high activation energy calcd. from the exptl. data can be ascribed to the high bonding energy of Gd-O bond, and the difference in activation energy for the two steps is due to the change in the bond length of hexagonal Gd(OH)3 and monoclinic GdOOH. .