Mechanism and Kinetic Parameters of the Thermal Decomposition of Gibbsite Al(OH)₃ by Thermogravimetric Analysis

• Authors: D. Redaoui , F. Sahnoune , M. Heraiz , A. Raghdi
• Languages of publication: EN

Abstracts

EN

In this study, the mechanism and the kinetic parameters of the thermal decomposition of gibbsite Al(OH)₃ were studied by differential thermogravimetry technique under non-isothermal conditions, between room temperature and 1200 K at heating rates of 5, 10, 15 and 20°C min¯¹. The obtained differential thermogravimetry curves show clearly three distinct peaks. The first peak is due to the partial dehydroxylation of gibbsite. Among the 32 types of differential equations of non-isothermal kinetics, we have found that the most suitable mechanism is (A_{3/2}: g(x)=[-ln(1-x)]^{2/3}) also called Avrami-Erofeev equation of order 2/3. The values of the activation energy E_{A} and of the pre-exponential factor K are 157 kJ mol¯¹ and 7.58×10¹⁵ s¯¹, respectively. The second peak corresponds to the decomposition of gibbsite to boehmite. Decomposition is controlled by the rate of second-order reaction (F₂: g(x)=(1-x)¯¹-1), under the applied conditions. The activation energy E_{A} and pre-exponential factor K correspond to 243 kJ mol¯¹ and 3.73×10²² s¯¹, respectively. The third peak is due to transformation of boehmite to alumina. However the mechanism for such transformation is better described by the 3/2 rate order reaction (F_{3/2}: g(x)=(1-x)^{-1/2}-1). In addition, the values of E_{A} and K were determined to be around 296 kJ mol¯¹ and 1.82×10¹⁹ s¯¹, respectively. The results of differential thermogravimetry were supplemented by the differential thermal analysis. X-ray powder diffraction analysis was carried out for samples of gibbsite treated at different temperatures between 200 and 1200°C in 200°C steps.

Keywords

EN

81.70.Pg; 81.05.Je; 81.05.Mh; 81.30.Mh; 07.85.Nc

Discipline

• 81.05.Mh: Cermets, ceramic and refractory composites
• 81.05.Je: Ceramics and refractories (including borides, carbides, hydrides, nitrides, oxides, and silicides)(for ceramics in electrochemistry, see 82.45.Yz)
• 81.30.Mh: Solid-phase precipitation(for precipitation hardening, see 81.40.Cd)
• 07.85.Nc: X-ray and γ-ray spectrometers
• 81.70.Pg: Thermal analysis, differential thermal analysis (DTA), differential thermogravimetric analysis

• Publisher: Institute of Physics, Polish Academy of Sciences
• Journal: Acta Physica Polonica A
• Year: 2017
• Volume: 131
• Issue: 3
• Pages: 562-565

Dates

published

2017-03

Contributors

author

D. Redaoui

• Physics and Chemistry of Materials Lab., Department of Physics, University Mohamed Boudiaf of M'sila, 28000, M'sila, Algeria

author

F. Sahnoune

• Physics and Chemistry of Materials Lab., Department of Physics, University Mohamed Boudiaf of M'sila, 28000, M'sila, Algeria

author

M. Heraiz

• Physics and Chemistry of Materials Lab., Department of Physics, University Mohamed Boudiaf of M'sila, 28000, M'sila, Algeria

author

A. Raghdi

• Physics and Chemistry of Materials Lab., Department of Physics, University Mohamed Boudiaf of M'sila, 28000, M'sila, Algeria

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Identifiers

DOI

10.12693/APhysPolA.131.562