ABSTRACT
Previous chapters have reviewed the properties of materials that directly affect their abilities to release or absorb hydrogen reversibly. This chapter examines the properties of materials that most impact their practical implementation in real hydrogen storage systems. These “engineering properties” are defined as the characteristics of heat transfer, mass transfer, and mechanical stress within a physical arrangement of storage material particles consisting of amorphous structures, single crystals, or aggregates. This arrangement of particles is called a bed. Engineering properties considered in this chapter include packing density, thermal conductivity, expansion, and permeability. In general, hydrogen storage materials are high-surface-area materials consisting typ-
ically of transition metals, alkali metals, and other light elements such as B, N, or C. Characteristic particle sizes tend to be small. Beds may sinter or decrepitate with thermal or hydrogen cycling. Decrepitation is the systematic disintegration of bulk particles into smaller particles or “fines.” The morphology of the bed may vary significantly as a function of hydrogen content. Also, for reversible materials, significant changes can occur during the life cycle of the bed, leading to order-of-magnitude changes in engineering properties.
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