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In this investigation, a crystalline metaboric acid (HBO2) powder was subjected to a dehydration process to transform it into boron oxide (B2O3) using thermogravimetry (TG) technique in an argon atmosphere under non-isothermal conditions at different heating rates (3, 5, 10, and 15 °C min−1). The results of kinetic analysis revealed that the dehydration process was a complex one comprising a consecutive region (region I) followed by a parallel one (region II). Using the relevant kinetic models, the mechanisms involved in each region were analyzed by a proposed method for the complex reactions separately and find that the dehydration mechanism in the region I consisted of the kinetic models R4: g(α) = [1 − (1 − α)2/3] (the chemical reaction at the HBO2/H2B4O7 interface) and D3: g(α) = [1 − (1 − α)1/3]2 (the diffusion of H2O (g) in the H2B4O7 layer), while that in the region II was parallel and consisted of the models D3 (the diffusion of H2O (g) in the H2B4O7 layer) and R4 (the chemical reaction at the of H2B4O7/B2O3 interface). Therefore, based on the kinetic results, the mechanisms of complex processes could be determined by the method. [ABSTRACT FROM AUTHOR]

In this study, titanium particles (with an average size of 48 µm) are dispersed throughout Al foils using the accumulative roll bonding method. The reaction between the particles and the matrix is subsequently activated thermally by post-rolling annealing. The in-situ reaction between the titanium powder and the aluminum matrix promoted by mechanical activation due to accumulative roll bonding and thermal activation due to annealing leads to the formation of Ti-Al intermetallic compounds. The distribution of particles and the intermetallic compounds thus formed are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), field-emission SEM (FESEM), electron probe micro-analysis (EPMA), and optical microscopy. The composite produced with 5 wt pct particles after 20 cycles of rolling and annealing yields the best particle distribution and TiAl3 formation such that the only intermetallic compound formed is TiAl3. The highest TiAl3 contents are recorded in the Al-TiAl3 composite formed by 20 cycles of rolling and annealed after rolling cycle numbers 5 and 9 (2 hours at 430 °C), as well as 12, 17, and 20 (2 hours at 600 °C). Surface energy is found to decrease when the most faceted particles become spherical in shape at high temperatures during the annealing process. Particles as small as 250 nm in size are also observed to form in this composite, and thus fabricated. [ABSTRACT FROM AUTHOR]