We have studied systematically the effects of temperature, time, and pressure on the process of hydrogen absorption in LaFe11.5Si1.5 compound. Results show that hydrogen absorption can increase the lattice parameter of the compound without changing its crystal structure. The LaFe11.5Si1.5H1.6 compound can be prepared at a hydrogen pressure of 0.0987 MPa at 423 K with uniform distribution of hydrogen. Hydrogen absorption can also increase the Curie temperature obviously, decrease the thermal hysteresis and maintain the magnetic entropy change at a high standard. With prolonged exposure time in air, the variation of the Curie temperature and magnetic entropy change of LaFe11.5Si1.5H1.6 compound are very small, implying that the magnetic thermal performance of hydride alloy has a good time stability.

Surfactant-assisted high energy ball milling technique is a new method of producing magnetic nanoparticles. In this study, permanent magnetic SmCo 5 nanoparticles and nanoflakes with high room-temperature coercivity values and narrow particle size distributions were produced by this technology and a subsequent size-selection process. The SmCo 5 nanoparticles with average particle sizes of 9.8 and 47.5 nm, exhibited room-temperature coercivity values of 6.8×10 4 and 7.3×10 5 A/m, respectively, while the SmCo 5 nanoflakes, with the mean particle size of about 1.4 μm and average thickness of 75 nm, showed excellent permanent magnetic properties with an obvious c-axis crystal texture, a strong magnetic anisotropy and high coercivity values of 5.5×10 5 and 1.6×10 6 A/m in their easy-axis and hard-axis directions, respectively. The coercivity values of SmCo 5 nanoparticles and nanoflakes exhibited a significant particle size dependance effect.

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