Showing 2 results for H. R. Shahverdi
A. Rasooli, H. R. Shahverdi, M. Divandari, M. A. Boutorabi,
Volume 29, Issue 1 (Jun 2010)
Abstract
In this research, the reaction kinetics of TiH2 powder in contact with pure aluminum melt at various temperatures on the basis of measuring the released hydrogen gas pressure was studied. To determine the mechanism the reaction, after Solidification of samples, interface of TiH2 powder in contact with melt was studied. The results showed that PH2-time curves had three regions. In the first and second regions, the rate of reaction conforms to zero and first order, respectively. In the third region, hydrogen gas pressure remains constant and the rate of reaction becomes zero order. In the first and second regions, the main factors controlling the rate of reaction are diffusion of hydrogen atoms within titanium lattice and chemical reaction of titanium with aluminum melt, respectively. Based on the main factors controlling the rate of reaction, three temperature ranges can be considered for reaction mechanism, a) 700-750ºC, b) 750-800ºC and c) 800-1000ºC. In the temperature range (a), the reaction is mostly chemical reaction control. In the temperature range (b), the reaction is diffusion and chemical reaction control, and in the temperature range (c), the reaction is mostly diffusion control.
A. Rasooli, M. Divandari, H. R. Shahverdi, M. A. Boutorabi,
Volume 30, Issue 1 (Jun 2011)
Abstract
In this research, DTA and TGA curves of titanium hydride powder in air with the heating rates of 5, 10, 20, 25, 30ºC/min were drawn, and XRD patterns of titanium hydride powder during heating rate 10ºC/min were prepared. Results showed that hydrogen comes out of titanium hydride in air during seven stages. And, by increasing heating rate, the mechanism of hydrogen emission from titanium hydride is almost fixed. Upon computation of activation energy of these stages, it was revealed that the mechanism does change at different temperatures. According to DTA curve at 10ºC/min, at temperatures lower than 460ºC, the mechanism is controlled by internal diffusion, at temperatures between 460-650ºC, it is controlled by physicochemical process, and at temperatures higher than 650ºC, it is controlled by chemical reaction. By increasing heating rate, the mechanism is changed at higher temperatures.
