Non-oxide ceramic nanostructured powders are synthesized through metastable transformation
processing based on the Self-propagating High-temperature Synthesis (SHS) process followed by
quenching. Binary systems like the investigated TiC–TiB2, when quenched from the liquid state
give rise to metastable structures capable of being converted into a stable, fine-grained
(nanocomposite) microstructure upon recrystallization by medium temperature treatments. A
necessary condition is that the combustion temperature of the SHS reaction is higher than the
eutectic temperature.
A previous optimisation of the reaction stoichiometry was carried out to obtain SHS products
with composition approximately equal to the eutectic (i.e. 67%mol TiC0,7 – 33%mol TiB2),
according to the reaction: 6Ti + B4C + 1.8C → 4TiC0.7 + 2TiB2.
In this work, different amounts of sodium borate (borax) were used in order to determine the
optimum amount of additive to produce nanostructured TiC0.7–TiB2 composites. The morphological
evolution of the powders after thermal treatment yielding re–crystallized structures demonstrates
the metastability of the SHS–quench products. Therefore, the metastability process based on SHS–
quench represents an extremely attractive route suitable for the achievement of nanocomposites.
Nanostructured Mg2Ni, Fe-doped and Ti-doped Mg2Ni alloys for hydrogen storage applications have been produced by means of Mechanically Activated Self-propagating High temperature Synthesis (MASHS). Different molar compositions of Fe and Ti (0.1; 0.3 and 0.5) have been studied in order to determine their influence in the hydrogen sorption properties. Different Mg-Ni based alloys have been tested in order to study their hydrogen sorption behavior. The hydrogenation was carried out in a Pressflow Gas Controller. Subsequently, the dehydrogenation process was conducted by means of a Differential Scanning Calorimetry (DSC) equipped with an H2 detector of the purged gas. The MASHS method has been demonstrated to be effective for the obtainment of nanostructured pure and doped Mg2Ni intermetallics. In addition, the materials produced showed hydrogen storage capacities superior to 4wt%, especially in the case of Fe-doped Mg2Ni and a slight reduction of desorption temperature was reached with Ti-doped Mg2Ni. Finally, the activation energy of the dehydrogenation process was evaluated and Ti-doped sample exhibited the lower activation energy value. Obtained results are promising for technological applications of Mg-based alloys.
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