Physical Review B

The effects of hydrogen on the physical and mechanical properties of iron and steel are reviewed. A new mechanism for the cold work peak for hydrogen in iron is considered. Together, internal friction and mechanical properties indicate that hydrogen softens iron by enhancing screw dislocation mobility at room temperature but hardens iron by core interactions at low temperatures. No single mechanism exists for the degradation of the properties of steel by hydrogen. Instead a complex process involving many of the proposed mechanisms as contributing factors is shown to account for most degradation phenomena.

Effects of hydrogen on the properties of iron and steel

The mechanisms of hydrogen-related fracture are briefly reviewed and a few evaluative statements are made about the stress-induced hydride formation, decohesion, and hydrogen-enhanced localized plasticity mechanisms. A more complete discussion of the failure mechanism based on hydrogen-enhanced dislocation mobility is presented, and these observations are related to measurements of the macroscopic flow stress. The effects of hydrogen-induced slip localization on the measured flow stress is discussed. A theory of hydrogen shielding of the interaction of dislocations with elastic stress centres is outlined. It is shown that this shielding effect can account for the observed hydrogen-enhanced dislocation mobility.

Hydrogen-enhanced localized plasticity—a mechanism for hydrogen-related fracture

Thin-Film Lithium and Lithium-Ion Batteries

Widespread adoption of hydrogen as a vehicular fuel depends critically upon the ability to store hydrogen on-board at high volumetric and gravimetric densities, as well as on the ability to extract/insert it at sufficiently rapid rates As current storage methods based on physical means—high-pressure gas or (cryogenic) liquefaction—are unlikely to satisfy targets for performance and cost, a global research effort focusing on the development of chemical means for storing hydrogen in condensed phases has recently emerged At present, no known material exhibits a combination of properties that would enable high-volume automotive applications Thus new materials with improved performance, or new approaches to the synthesis and/or processing of existing materials, are highly desirable In this critical review we provide a practical introduction to the field of hydrogen storage materials research, with an emphasis on (i) the properties necessary for a viable storage material, (ii) the computational and experimental techniques commonly employed in determining these attributes, and (iii) the classes of materials being pursued as candidate storage compounds Starting from the general requirements of a fuel cell vehicle, we summarize how these requirements translate into desired characteristics for the hydrogen storage material Key amongst these are: (a) high gravimetric and volumetric hydrogen density, (b) thermodynamics that allow for reversible hydrogen uptake/release under near-ambient conditions, and (c) fast reaction kinetics To further illustrate these attributes, the four major classes of candidate storage materials—conventional metal hydrides, chemical hydrides, complex hydrides, and sorbent systems—are introduced and their respective performance and prospects for improvement in each of these areas is discussed Finally, we review the most valuable experimental and computational techniques for determining these attributes, highlighting how an approach that couples computational modeling with experiments can significantly accelerate the discovery of novel storage materials (155 references)

http://www-personal.umich.edu/~djsiege/Energy_Storage_Lab/Publications_files/CSR_H2_storage.pdf

High capacity hydrogen storage materials: attributes for automotive applications and techniques for materials discovery

In this review an attempt is made to highlight some of the important properties of the palladium-hydrogen system. (The term hydrogen will be used as a collective term when referring to all three isotopes, but otherwise the names of the specific isotopes, protium, deuterium, and tritium, will be used.) Most of the data in the literature are for the palladium-protium system; generally the three isotopes behave similarly, however, the thermo­ dynamic and kinetic (diffusion) behavior of the isotopes differ quantita­ tively and these differences are discussed below. Lasser recently published a monograph entitled Tritium and Helium-3 in Metals (1), which contains a compilation of the thermodynamic prop­ erties of all three isotopes in palladium and in palladium-silver alloys. Lewis presented a comprehensive review in 1966 (2), certain aspects of which he has updated (3). Wicke & Brodowsky (4) reviewed the thermo­ dynamic and kinetic behavior of palladium-hydrogen and palladium alloy­ hydrogen systems in 1978. In view of the interest in this system, kindled by the recent discovery of possible anomalous effects in the Pd-D system, it appears to be a timely occasion to review the palladium-hydrogen system. The palladium-hydrogen system has long held a key role in metal-

The Palladium-Hydrogen System

Interstitial hydrogen contents and their associated volume increments have been determined for a variety of fcc metals and alloys. Using high pressure techniques, hydrogen contents approaching n = 1, where n = H-to-metal (atomic ratio), have been obtained. Despite electronic and initial volume differences amongst the fcc metallic matrices, all data fall onto a common relationship.

https://iopscience.iop.org/article/10.1088/0305-4608/1/3/307/pdf

The volume increase of fcc metals and alloys due to interstitial hydrogen over a wide range of hydrogen contents

A detailed model for hysteresis is presented for metal hydride systems based on the requirement for dislocation production during both hydride formation and hydride decomposition. A quantitative illustration of the model is presented using the regular interstitial solution approximation. The relationship between the solvus hysteresis and pressure hysteresis is given. The model predicts that calorimetrically measured enthalpies for hydride formation and decomposition will not exhibit any differences arising from hysteresis but that the enthalpies determined from the temperature variations of the plateau pressures for hydride formation and decomposition will show differences due to hysteresis.

Ted B. Flanagan

Papers

The Palladium-Hydrogen System

The volume increase of fcc metals and alloys due to interstitial hydrogen over a wide range of hydrogen contents

Hysteresis in metal hydrides

Lattice spacings of gold–palladium alloys

Dynamic equilibrium between chemisorbed and absorbed hydrogen in the palladium/hydrogen system