Microporosity of heat-treated manganese dioxide

被引:24
作者
Arnott, J. B. [1 ]
Williams, R. P.
Pandolfo, A. G.
Donne, S. W.
机构
[1] Univ Newcastle, Discipline Chem, Newcastle, NSW 2308, Australia
[2] Delta EMD Australia Pty Ltd, Mayfield W, NSW 2304, Australia
[3] CSIRO, Div Energy Technol, Clayton, Vic 3169, Australia
基金
澳大利亚研究理事会;
关键词
electrolytic manganese dioxide; EMD; porosity; ALKALINE ELECTROLYTE; CATHODIC REDUCTION; ADSORPTION METHOD; CATION VACANCIES; MOLECULAR AREA; GAMMA-MNO2; MNO2; DISCHARGE; SURFACES; SOLIDS;
D O I
10.1016/j.jpowsour.2006.10.028
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
A structural and micro-pore analysis of a series of heat treated electrolytic manganese dioxide (EMD) samples has been conducted. In terms of crystal structure, the original EMD with gamma-MnO2 structure (orthorhombic unit cell) was found to progressively convert to beta-MnO2 (tetragonal unit cell) at elevated temperatures. The structural transition was kinetically limited, with the higher temperatures leading to a greater degree of transformation. The orthorhombic gamma-MnO2 unit cell was found to contract along the a and b axes, while along the c axis an expansion was observed only at the highest heat treatment temperatures. These changes occur as a result of manganese ion diffusion leading to the formation of a denser, more defect free material. The porosity of these heat treated EMD samples was also examined by N-2 gas adsorption combined with various interpretive techniques such as the Kelvin equation, MP method, Dubinin-Radushkevich method, Dubinin-Astakhov method and a more modem density functional theory based approach. Despite shortcomings associated with certain techniques, all clearly indicated that the EMD micro-pore volume decreased and the meso- and macro-pore volume increased as the heat treatment temperature was increased. This was justified as a result of manganese ion movement during the structural rearrangement causing the small pores to be progressively sintered shut, while the larger pores were formed as a result of stress-induced cracking in the denser final product. (c) 2006 Elsevier B.V. All rights reserved.
引用
收藏
页码:581 / 590
页数:10
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