Particle Size Of Mg Research Articles

Improvement of hydrogen-storage properties of Mg by reactive mechanical grinding with Fe 2O 3

We tried to improve the H 2-sorption properties of Mg by mechanical grinding under H 2 (reactive mechanical grinding) with Fe 2O 3 under various milling conditions. The sample Mg–10 wt.%Fe 2O 3 prepared by milling at a revolution speed of 250 rpm for 24 h has the best hydrogen-storage properties. It absorbs 5.05 wt.% hydrogen at 593 K under 12 bar H 2 for 60 min at the first cycle. Its activation is accomplished after three hydriding–dehydriding cycles. The activated sample absorbs 4.22 wt.% hydrogen at 593 K, 12 bar H 2 for 10 min. The reactive grinding of Mg with Fe 2O 3 increases the H 2-sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and by the additive), by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. Hydriding–dehydriding cycling also increases the H 2-sorption rates by creating defects on the surface of the Mg particles, and by making cracks on the surface of Mg particles and reducing the particle size of Mg.

Development of hydrogen-storage alloys of Mg– [formula omitted] system by reactive mechanical grinding

We have improved the H 2 -sorption properties of Mg by mechanical grinding under H 2 (reactive mechanical grinding) with Fe 2 O 3 . The sample Mg–10 wt% Fe 2 O 3 prepared by milling at the revolution speed of 250 rpm for 6 h has the best hydrogen-storage properties. It absorbs 3.43 wt% hydrogen at the first cycle at 593 K under 12 bar H 2 for 60 min. Its activation is accomplished after three hydriding–dehydriding cycles. The activated sample absorbs 3.32 wt% hydrogen at 593 K, 12 bar H 2 for 60 min. The reactive grinding of Mg with Fe 2 O 3 increases the H 2 -sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and by the additive) by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. Hydriding–dehydriding cycling increases the H 2 -sorption rates by making cracks on the surface of Mg particles and reducing the particle size of Mg. The agglomeration of the particles resulting from the annealing effect during cycling decreases the hydriding and dehydriding rates.

Influences on the H2-sorption properties of Mg of Co (with various sizes) and CoO addition by reactive grinding and their thermodynamic stabilities

We attempted to improve the H2-sorption properties of Mg by mechanical grinding under H2 (reactive grinding) with Co (with various particle sizes) and with CoO. The thermodynamic stabilities of the added Co and CoO were also investigated. CoO addition has the best influence and addition of smaller particles of Co (0.5–1.5 μm) has a better effect than the addition of larger particles of Co on the H2-sorption properties of Mg. The activated Mg+10 wt.% CoO sample has about 5.54 wt% hydrogen-storage capacity at 598 K and the highest hydriding rate, showing an Ha value of 2.39 wt.% after 60 min at 598 K, 11.2 bar H2. The order of the hydriding rates after activation is the same as that of the specific surface areas of the samples. The reactive grinding of Mg with Co or CoO and hydriding-dehydriding cycling increase the H2-sorption rates by facilitating nucleation of magnesium hydride or α solid solution of Mg and H (by creating defects on the surface of the Mg particles and by the additive), and by making cracks on the surface of Mg particles and reducing the particle size of Mg, thus shortening the diffusion distances of hydrogen atoms. The cobalt oxide is stable even after 14 hydriding cycles at 598 K under 11.2 bar H2. Discharge capacities are measured for the sampple Mg+10 wt.%CoO and Mg+10wt.%Co (0.5−1.5 μm) with good hydrogen-storage properties.

Effects on the H 2-sorption properties of Mg of Co (with various sizes) and CoO addition by reactive grinding

We tried to improve the H 2-sorption properties of Mg by mechanical grinding under H 2 (reactive grinding) with Co (with various particle sizes) and with CoO. The CoO addition has the best effect and the addition of smaller particles of Co (0.5–1.5 μm) has a better effect on the H 2-sorption properties of Mg than the addition of larger particles of Co. The activated Mg+10 wt.% CoO sample has a hydrogen-storage capacity of about 5.54 wt.% at 598 K. The reactive grinding of Mg with Co or CoO and the hydriding–dehydriding cycling increase the H 2-sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and/or by the additive), by making cracks on the surface of the Mg particles and by reducing the particle size of Mg and thus by shortening the diffusion distances of the hydrogen atoms.

Effect of Particle Size on Combustion of Magnesium-Sodium Nitrate Propellants

Abstract The Combustion of Mg-NaNO3, propellants at different mixture ratios has been studied to establish the effect of particle size on the burning rate characteristics. Results indicate that compositions containing NaNO3, of finer particle size (50 μm) give higher burning rate at high fuel content of the mixture than at the stoichiometric ratio, whereas the compositions containing NaNO3 of coarser particle size (250μm) show increased burning rate with increasing oxidiser content (maximum at the stoichiometric ratio). Thermal decomposition results indicate that condensed phase heat release as well as reactions in the vapour phase are responsible for the variations in the burning rate. Decomposition products of finer size NaNO3, formed before Mg particles acquire sufficient energy for ignition, react exothermically with the Mg particles and lead to condensed phase heat release. This energy release, which is larger at higher fuel contents: is seen as causing higher burning rates with low pressure sensitivity. Increasing oxidiser content reduces the heat release in the condensed phase due to oxide coating of the metal particles with the higher concentration of the molten oxidiser leading to formation of metal agglomerates which eject from the surface and cause lower burning rate with high pressure sensitivity. In contrast, the decomposition products of coarser size NaNO3 diffuse out along with the metal particles for the reaction to occur in the vapor phase. This causes an increase of burning rate with increasing oxidiser content of the mixture up to the stoichiometric ratio with a pressure dependence. Further, the burning rate was found to increase with decreasing particle size of Mg due to the faster rate of heat transfer with the increase in surface area of the particles. The burning surface temperature data obtained during static tests at different mixture ratios and particle sizes also support the suggested mechanism.