In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Ferromagnetic materials

Hydrogen energy, economy and storage: Review and recommendation

One of the imposing barriers to realizing the promise of an energy economy based on hydrogen is onboard hydrogen storage for fuel-cell-powered vehicles. New materials that enable the release of dense, plentiful and pure hydrogen at temperatures less than 85 oC are necessary to move the world from an oil-based economy to a hydrogen economy. We report a novel approach in which we deposit a hydrogen-rich material into a nanoporous scaffold. The role of the scaffold is to impose a nano-phase structure on the hydrogen-rich material thus providing an additional handle on the kinetics and thermodynamics of hydrogen release. We demonstrate on the example of ammonia borane infused in the nanoporous silica that the kinetics of hydrogen release is improved while the purity of hydrogen is increased in comparison with the release from bulk ammonia borane. These findings suggest that hydrogen rich materials infused in nanoscaffolds offer the most promising approach to date for onboard hydrogen storage

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.200462602

Nanoscaffold Mediates Hydrogen Release and the Reactivity of Ammonia Borane

This review highlights various aspects of current palladium membrane research and serves as a comprehensive bibliography covering palladium membrane preparation methods and applications. There are many promising uses for palladium membranes, although widespread use of the available technologies is constrained primarily by the high cost of palladium, lack of durability due to hydrogen embrittlement, and susceptibility to fouling. Various researchers in the field are tackling these problems and fabricating thinner palladium alloy composite membranes that better withstand contaminantion and thermal cycling. What has been accomplished to address these issues and the directions presently being explored are discussed.

Innovations in palladium membrane research

Hydrogen is considered a good energy carrier candidate for future automotive applications that could be part of a carbon-free cycle. Metal hydrides are often preferred over pressurized gas and other hydrogen storage methods because of their gravimetric and volumetric storage capacities and safe operating pressures. In addition to the hydrogen storage capacity, other properties that have often been disregarded must now be addressed before hydrogen storage in metal hydrides becomes feasible. The slow hydriding/dehydriding kinetics, high release temperature, low storage efficiency due to the high enthalpy of formation, and thermal management during the hydriding reaction remain important difficulties in meeting the objectives set by the Department of Energy (DOE) for hydrogen storage systems. Nanotechnology offers new ways of addressing those issues by taking advantage of the distinctive chemical and physical properties observed in nanostructures. Nanostructured materials significantly improve the reaction kinetics, reduce the enthalpy of formation, and lower the hydrogen absorption and release temperatures through destabilization of the metal hydride and multiple catalytic effects in the system. But nanostructures can also lead to poor cyclability, degradation of the sorption properties, and a significant reduction of the thermal conductivity that could make metal hydrides impractical for hydrogen storage. This review summarizes the effects that nanotechnology can have on the main properties of metal hydrides and highlights the main competing behaviours between the system requirements, the necessary trade-offs, and the research priorities necessary to obtain hydride storage materials for practical automotive applications. Copyright © 2007 John Wiley & Sons, Ltd.

Size effects on the hydrogen storage properties of nanostructured metal hydrides: A review

High-resolution tomographic imaging is demonstrated using a reflection-type terahertz time-domain spectroscopy. To realize a practical system for general use, a robust all-fiber laser was used as the pump light source. Broadband terahertz waves were generated with the combination of optical pulses compressed to 17 fs using optical fibers and a DAST crystal. Using deconvolution signal processing, the wideband spectrum of the generated terahertz waves provided high-axial resolution leading to successful imaging of a multilayered structure containing a 2-μm-thin GaAs layer. To our knowledge, this is the first demonstration of terahertz tomographic imaging of such a thin layer.

High-resolution time-of-flight terahertz tomography using a femtosecond fiber laser

Hydrogen absorption of nanocrystalline palladium

An automated Sieverts-type apparatus was developed to measure the change in the rate of the hydrogen reaction with LaNi5 and the change in the statistical size distribution of the alloy particles as a function of the number of hydrogen absorption-desorption cycles. Exposure of LaNi5 to oxygen or air at room temperature inhibits the hydrogen absorption rate and drastically reduces the particle size. The measurements of the X-ray diffraction peaks of LaNi5 revealed a strong anisotropic change in the broadening of the peaks with an increasing number of hydrogen absorption-desorption cycles. The oxidized LaNi5 particles pulverize under the lower stresses induced by the repeated change in the volume of the alloy during the hydrogen absorption—desorption cycles.

Effect of the pulverization of LaNi5 on the hydrogen absorption rate and the X-ray diffraction patterns

Synthesis of Ti–Fe alloys by mechanical alloying

http://www.ex.u-tokai.ac.jp/uchida_lab/Review%20Paper.pdf

Hirohisa Uchida

Papers

High-resolution time-of-flight terahertz tomography using a femtosecond fiber laser

Hydrogen absorption of nanocrystalline palladium

Effect of the pulverization of LaNi5 on the hydrogen absorption rate and the X-ray diffraction patterns

Synthesis of Ti–Fe alloys by mechanical alloying

Surface processes of H2 on rare earth based hydrogen storage alloys with various surface modifications