Journal Title: پاییز 1387
Article title: Study of Thermal Decomposition Kinetic of Titanium Hydride Powder

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Article abstract:
Titanium hydride powder is used as blowing agent in the production process of metallic foams (especially aluminum metallic foams). As a result of thermal decomposition of TiH2 powder, a massive volume of hydrogen gas releases. The hydrogen evolution, inside molten aluminum, generates bubbles and if the process is properly controlled Al foam will be produced. Determination of the conditions, rate and mechanism of decomposition process is very important for reaching to an acceptable product. In this research, the online measurement of hydrogen evolution, at temperatures range of 673- 1273K, was used for studying the decomposition kinetics of titanium hydride. The results showed that at temperatures range of 673-873K, the decomposition of TiH2 powder is under control of internal diffusion of hydrogen atoms along the titanium oxide (Ti2O3) layer. At higher temperatures, 973-1073K, the TiH2 powder is decomposed at two stages. At the first stage, the equation of velocity is parabolic and the decomposition process under control of internal diffusion. After hydrogen gas pressure reaches to a constant level, the second stage starts. In this stage, the rate equation of decomposition of TiH2 powder will be of zero order, at first, which changes to a parabolic equation later. Titanium hydride decomposes at two stages TiH2→TiHX→α-Ti. The first stage is under control of diffusion of hydrogen atoms in the TiHX layer and the second stage is under control of the chemical reaction. The activation energy is 59.112 kJ/mole approximately, at the first stage, and 81.388 kJ/mole at the second stage, respectively.
Article keyWords:
Kinetics, Titanium Hydride, Thermal Decomposition, Internal Diffusion, Aluminum Foam
Article Authors:

	علي رسولي	First Author	Ali_Rasooli@Iust.ac.ir
	 حميدرضا شاهوردي	Other Author
	مهدي ديواندري	Other Author
	سيد محمدعلي بوترابي	Other Author