Progress In Hydrogen Treatment Of Materials

Edited by V.A. Goltsov

Authors:

A successful entering into the life of an ecologically clean hydrogen economy and an expected transition to hydrogen civilization in the future require the creation of new and new hydrogen-stable structural materials, new and new advanced functional ones, new special technologies of their production and treatment.

In response to these modern day requirements the world-renowned scientists and experts from ten countries have contributed to this book - the first book reviewing the origination and development of a novel field of Materials Science and Engineering now referred to as "Hydrogen Treatment of Materials" (HTM).

The book generalizes the knowledge related to the HTM-theory and the HTM-technology. There are considered structures and properties of material-hydrogen (MH) systems, their surface and subsurface layers, thin films and multilayers. A diffusive-cooperative synergetic nature of MH-systems is generalized, their thermodynamic and kinetic peculiarities are analyzed, and related phenomena are described. For the first time there are systematically considered hydrogen-induced phase transformations: their nature, classification, mechanisms, kinetics, morphology, influence on structure and properties and use in the HTM. The present day knowledge is summarized as it relates to the HTM-technologies for deformed, cast and synthesized materials, such as palladium, niobium, vanadium, alloys on the base of Al, Ti, Fe, intermetallics, nonmetallic materials; the achievements of the HTM-technologies, improving their structures, mechanical, physical and catalytic properties are described. Some attention is also given to hydrogen degradation of metals, alloys and steels.

The book is intended for Materials Science scientists, physicists, chemists, engineers and other active members of the world hydrogen movement. It will be highly useful for students, post-graduates and young scientists who are interested in the structure, properties and applications of material-hydrogen systems.

Copyright © Kassiopeya Ltd.

© Informative-Tecnological Association on Noble, Rare and Non-Ferrous Metals (ITA NRNFM)

© Donetsk State Technical University (DonSTU)

58 Artyom street, DonSTU, 83000 Donetsk, Ukraine

E-mail: Goltsov@physics.dgtu.donetsk.ua

Web: http://dgtu.donetsk.ua/hydrogen

P R E F A C E ^

It was just a little over a quarter of a century ago, during the first International Conference on Hydrogen Energy (the Hydrogen Economy Miami Energy Conference, 18-20 March 1974, Miami Beach, FL, U.S.A.) when a small group of 'Hydrogen Romantics' got together. It was agreed that the Hydrogen Energy System was an idea whose time had arrived. It was the permanent solution to the global environmental problems.

So, International Association for Hydrogen Energy (IAHE) was established by the end of that year, and started working in earnest. One of the first activities of IAHE was establishing (1975) The International Journal of Hydrogen Energy - the official journal of IAHE and then organizing the biennial World Hydrogen Energy Conferences (WHEC) to provide a platform for forming Hydrogen Energy Community: the scientists, energy engineers, environmentalists, decision makers, and the thinkers of the future of humankind and Planet Earth. Since 1976 WHEC was held in Miami, Zuerich, Tokyo, Pasadena, Toronto, Vienna, Moscow, Honolulu, Paris, Cocoa Beach, Stuttgart, Buenos Aires and Beijing.

In the quarter of the century hydrogen has made significant progress and inroads in all the directions in the energy field, due to its unmatched superior properties and characteristics as an energy carrier, on the one hand, and due to the unrelenting work of all those who took part in the Hydrogen Movement, on the other hand.

Historically in parallel with Hydrogen Energy Community Hydrogen-Materials one was successfully developing in the world. As materials problem forms a very important part of any global vector of human development, more and more close cooperation of the above mentioned communities was necessary for the future Hydrogen Economy entering into the life. This cooperation has already its own long history, and its development was very successful thanks to the activity of many outstanding scientists and well-known scientific groups. Among them it is necessary to emphasize the Donetsk group, headed by Professor V.A. Goltsov - the Editor of this Book, a scientist awarded now (June 2000) with IAHE Rudolf E. Erren Award 'for Outstanding Contribution to Hydrogen Energy in General and to Hydrogen Treatment of Materials in Particular'.

Really, since the middle of the 1970s special national and international conferences on the Hydrogen Energy and Hydrogen-Materials problems were held in Donetsk every two-three years. It was just Professor V.A.Goltsov who discovered in the 1970s a new fundamental hydrogen property: hydrogen is not only an excellent universal energy carrier, but it is a fundamental, unique agent for hydrogen treatment of materials permitting to improve their structure and properties, to create new advanced materials needed for Hydrogen Economy. Since that time this new paradigm of Materials Science has attracted new and new adherents.

In 1997 under the auspices of IAHE the Permanent Working International Scientific Committee on Hydrogen Treatment of Materials (PWISC HTM) was established (Chairperson is Prof. V.A. Goltsov, Co-Chairperson is Dr. F. Lewis). One of the general aims and tasks of the created Committee is to support permanently the cooperation of the Hydrogen Energy Community and Hydrogen-Materials one. For this purpose IAHE and PWISC HTM organized triennial international conferences "Hydrogen Treatment of Materials". Proceedings of the selected papers of these conferences are published in IJHE.

This Book is also a result of PWISC HTM activity and of a long scientific work of all its authors. Being the first review of the topic the book "Progress in Hydrogen Treatment of Materials" generalizes the achievements of this new field of Materials Science and Engineering during its starting period of time. Without any doubt it will be very useful for moving forward on all fronts of Hydrogen Treatment of Materials and other Hydrogen-Materials problems.

My colleagues, authors of this Book, being members of World Hydrogen Movement you can be very proud of the results of your unrelenting work making a great contribution to the development of Hydrogen Economy, the only one known to be clean, efficient, sustainable, abundant, hospitable to life on the Planet Earth. I am sure the readers of this Book will positively estimate your scientific achievements.

T. Nejat Veziroglu
Director,
Clean Energy Research Institute,
University of Miami, FL 33124, U.S.A.
President,
International Association for Hydrogen Energy

INTRODUCTION ^

Hydrogen Treatment of Materials (HTM) is a novel field of Materials Science and Engineering. Historically, it has been conceived recently and is being developed for about a quarter of a century. So, much of this area of knowledge has not been well-established yet and cannot be interpreted one-to-one until now. In the context of this book issuance it is appropriate herein to determine the HTM-essence.

Hydrogen provides exceptionally great scope to effect the materials under treatment, in many ways this scope is more diverse than the ones of other fundamental effects.

Really, hydrogen effect comprises physical, chemical, physico-chemical and mechanical compounds. Fundamental changes of thermodynamic, kinetic, phase-structural and other conditions of the existence of materials are produced by the hydrogen action that implies a change in their structure and properties of practical importance which do not disappear after completing hydrogen treatment.

Possibilities of hydrogen treatment are still extending, as hydrogen action can be combined (and are being combined in practice already) with other fundamental actions, that is with the heat (temperature), mechanical (deformation), physical fields and with particle fluxes. By the character of the external action the HTM is correspondingly classified into the following subtypes: hydrogen–heat (thermal) treatment, hydrogen–mechanical treatment, hydrogen–thermal–mechanical treatment, hydrogen–plasma treatment and the like. A further more comprehensive classification of the HTM by different distinctive features and directions is given in the Appendix to this book, and it clearly demonstrates the widest practical possibilities of the HTM.

The HTM, as a unified field of science and engineering, has its own scientific structure and can be firstly divided into two interrelated subfields: the HTM- theory and the HTM-technology, each has its own different first principles, objectives, tasks and methods of their solving.

In its development the HTM – theory, being an applied area of science, has its bases in physics (and first of all in solid-state physics and metal physics), crystallography, physical chemistry, chemistry and other fundamental sciences, It is important therewith to understand the following fundamental circumstances. Those achievements and knowledge, which are the ‘net’ result of a fundamental science, often turn out to be the initial ‘first principles’ for the HTM-theory. Furthermore, on this base the HTM-theory forms, figuratively speaking, its own ‘rules of play’, which provide the development of an interrelated system of conceptions, theories, laws, etc., or in the other words, the development of its own paradigm. The latter being conceived about 25 years ago controls the operation and further progress of the HTM – theory.

If one required a short answer on the question: what is the main task and the dominant subject-matter of the HTM-theory? – The answer would be as follows: The task and subject-matter of the HTM-theory, as an area of science, consist in establishing laws of a correlation between controllable changes of practically important properties of materials and their structure changes induced by a hydrogen action, or by other actions combined with the hydrogen one. These laws are at the basis of the HTM-technology.

All aforesaid is a close-up view of the tasks, structure and subject-matter of the hydrogen treatment of materials as a novel field of Materials Science and Engineering.

Now, some words should be said on the structure and content of this book, the first book summarizing knowledge on the HTM. It is quite evident that the reviews submitted to this book and written by the world-known scientists and experts from ten countries are of prime interest for both the HTM-theory and the HTM-technology. That is why an editor’s division of the book into some parts is substantially a matter of convention. Nevertheless, I have done this division keeping in mind the following principles.

Chapter I (a knowledge related to the HTM-theory) comprises the review summarizing the knowledge obtained on the ‘model’ materials (Pd, Nb, V and the like) and substantially covering general thermodynamic, kinetic and phase-structural peculiarities of metal–hydrogen systems, and structural processes proceeding in them.

Chapter II (a knowledge related to the HTM-technology) comprises the review summarizing the knowledge obtained on important for many practical purposes metallic, intermetallic and nonmetallic materials. The spirit of writing these papers and authors’ position have been therewith taken into account.

Chapter III (a knowledge related to hydrogen degradation) contains the reviews which are not straight related to the HTM. But these papers are undoubtedly important from the practical standpoint. Besides, they let readers think over a transition field: where, when and how hydrogen positive action transforms and causes hydrogen degradation and a possibility of an accident failure. This question is very important in principle. During technical civilization development a man very often comes across such problems. It is appropriate here to remind that our ancestors, that is folk-blacksmiths, knew about such a possibility. When they forged tools (blades, daggers, axes and the like), they knew that they could continue forging a cooling metal, and it would keep on strengthening (!). But its properties are to be improving up to a certain limit only. If you miss a moment, a metal under strengthening and deforming will crack and will be unsuitable for practical use. In some measure, such a situation is typical for a hydrogen action too: in some cases it improves properties of a material, and in other cases it deteriorates them, a boundary area between these situation has not been studied yet.

Chapter IV (Appendix). There are covered some moments of the generation and development of the HTM both from the viewpoint of scientific information as it is, and from the viewpoint of history of the formation of a corresponding international HTM-community. Its interrelation with the widespread world hydrogen movement, working for the benefit of a further hydrogen civilization, is of a special interest.

Dear colleagues – authors of this book! I thank everyone of you personally and all together for the happiness of a collective creative work which has been now brought to completion. I hope you share this opinion and enjoy just now holding our collaborative work in your hands.

We should acknowledge Dr. Eng. Lyudmila F. Goltsova, technical and computer editor, and Mrs. V.A. Garkusheva, English corrector. It has been just their painstaking job, which has made the publication of this book possible.

Special acknowledgement should be given to Professor Dr. Eng. T.N. Veziroglu, President of International Association for Hydrogen Energy, who has been actively supporting for many years and still supporting our international HTM-community. His high appraisal of our work has been given in the Preface to this book.

As in any other work, there might be some inaccuracies, misprints, etc. in our work. We hope that, figuratively speaking, ‘the experimental error’ does not exceed a reasonable scale allowed by the experimental science, for example.

In conclusion I would like to express my hope that our work will be appraised by readers, and the ideas which are apparent from this book will get their successors.

March, 2001

Victor A. Goltsov.^Fundamentals of hydrogen treatment of materials. The fundamentals of hydrogen treatment of materials (HTM) are reviewed and generalized. The first, aims and tasks of hydrogen treatment had been summarized and it was concluded that there are two branches of this novel field of Material Science and Engineering: theory of HTM and technology of HTM. Both of them are based on some specific peculiarities of hydrogen action on materials, which being strong, controllable and reversible comprise physical, chemical, physico-chemical and mechanical components. Then a fundamental knowledge of diffusive-cooperative nature of material-hydrogen systems is generalized; a classification and a panoramic overview of the related phenomenon have been done. What followed is a review of hydrogen-induced phase transformations, their nature, classification and use in HTM. At last, hydrogen-controlled phase transformations and their using in engineering are discussed in short. In conclusion a central knowledge of materials-hydrogen systems nature, being a fundamental base of HTM, has been summarized briefly.

Ted B. Flanagan.^The thermodynamics of hydrogen solution in 'perfect' and defective metals and alloys. The thermodynamics of H₂ solution and hydride formation is reviewed for 'perfect', i.e., relatively defect-free, and for defective metals and alloys. Emphasis is placed on Pd and Pd-rich alloys because most data are available for these. Hydrogen-induced changes are reviewed which take place at moderately high p_H2 and temperatures in some Pd-M alloys due to the establishment of a ternary (Pd + M + H) equilibrium and because of H-enhanced metal atom diffusion. Hydrogen solubility in the phase-separated alloys at ambient temperature has been employed to characterize the separated phases.

Hydrogen solubility has been employed to follow order/disorder in a Pd₃Mn alloy. When Pd₃Mn is ordered in the presence of H₂, a L1₂ structure forms but ordering in vacuo produces a long-period superstructure. Ordered Pd₃Mn alloys dissolve significantly more H₂ than the disordered form.

Leonid I. Smirnov and Victor A. Goltsov.^ Diffusion and diffusive phenomena in interstitial subsystems of M-H systems. A review of theoretical ideas and notions of diffusion and diffusive phenomena in an interstitial subsystem of metal–hydrogen systems has been done. The very simple theoretical regarding only interstice occupancy has already given interesting results: as hydrogen concentration grows, a hydrogen self-diffusion coefficient decreases and tends to zero at a complete occupancy of interstices. This effect is taken into account in all the following theories.

The theories, which additionally take into account the interaction of hydrogen atoms, result in many nontrivial results. As the concentration grows a chemical diffusion coefficient (D) of hydrogen runs into a minimum, first, and at low temperatures it is even negative (the region of ‘uphill diffusion’ and concentration separation). Then D increases, reaches a maximum and, at last, decreases again. As concentration increases and temperature falls, ‘diffusion’ motion of hydrogen atoms is more and more ordered. Near by a spinodal hydrogen concentration an inhomogeneity gets a sharply defined wave front moving with a finite velocity. Under some definite conditions hydrogen concentration inhomogeneity can make an ‘oscillating’ motion, changing its dimensions from time to time. The theory, more general than the theory of Cahn, predicts a possibility of the formation in under a spinodal cupola complex, greatly inhomogeneous structures which are a superposition of sinusoidal concentration inhomogeneities of hydrogen with multiple wave vectors.

Victor A. Goltsov, Tatyana A. Ryumshina, Leonid I. Smirnov, Zhanna L. Glukhova and Raisa V. Kotelva. ^ Theory of hydrogen elasticity phenomenon. In this review there is theoretically generalized hydrogen elasticity, a fundamental phenomenon determining a unique specific nature of metal hydrogen systems. Under the conditions of the monophase regions of the equilibrium phase diagrams of metal–hydrogen systems and at small values of hydrogen concentration gradients the hydrogen elasticity (HE) phenomenon can be adequately described by the system of nonlinear equations analogous to the equations of thermoelasticity. There are given examples of a successful use of these equations and considered cases of hydrogen atoms diffusion migration and of a metallic plate form changing under the influence of hydrogen concentration gradients.

It is shown, that generally the theory of the HE-phenomenon must take into account a concentrational dependence of an effective coefficient of hydrogen diffusion. So, the deduction of a more general kinetic equation is discussed. The equation is valid to an interconnection between the ‘uphill’ diffusion of hydrogen and hydride transformations in metal-hydrogen systems. This kinetic equation and the equation of a metallic matrix motion being interconnected are rather general and adequately describe a wider range of a known hydrogen elasticity and diffusivity effects and predict new ones too.

There are analysed conditions of a metal transition from a hydrogen elasticity region to a hydrogen plasticity one. Such a transition initiates hydrogen phase naklep (cold work) proceeding in metal hydrogen systems. Influences of an initial stressed state, a hydrogen loading rate and a real initial structure on a hydrogen elastic-plastic behaviour of a metal are discussed.

Hartmut Zabel and Bjorgvin Hjorvarsson. ^Hydrogen in thin films and multilayers. Hydrogen in metals has been of sustained interest to material scientists and physicists because of its intriguing structural, thermodynamic and electronic properties. Best known is, however, the damaging mechanical influence causing embrittlement in structural materials. In recent years another, 'smarter' property of hydrogen in nanostructured metal films and superlattices has gained much interest. In these artificial structures hydrogen has been used for tuning the epitaxial misfit to the substrate, for generating a modulated lattice gas, and to switch optical and magnetic properties. We provide a brief overview of the structural and elastic properties of hydrogen in thin films and multilayers, which is essential for all work on these structures.

Frederick A. Lewis.^ Uphill hydrogen diffusion effects: Nature and manifestations. In keeping with proposals initially formulated by Gorsky, experimental evidence and theoretical arguments concerning stress/strain gradients produced during migrations of hydrogen interstitials, have quite solidly been obtained in studies with palladium and palladium alloys. In particular, Gorsky Effect operation explanations have been centrally important to interpretations of 'Uphill diffusion effect' phenomena that have become substantially recorded over the courses of studies of hydrogen diffusion behaviour.

Maria V. Goltsova, Yury A. Artemenko and Grigory I. Zhirov.^ Hydride transformations: Nature, kinetics, morphology. In the present review, the development of notions about hydride transformations is given. By the mid-1980s the synthesis of knowledge about hydride transformations had been done as about diffusive-cooperative transformations. A peculiarity of hydride transformations is that any rearrangement in a hydrogen subsystem is done by a diffusive way only. At the same time, the rearrangement of a crystal matrix proceeds by a cooperative, shift mechanism similar to a martensitic one. Therefore, hydride transformations were classified as a special type of phase transitions in a number of classic phase transformations.

Then, the available information about hydride transformations in the Pd-H system is summarized. It is shown that hydride transformations in this system proceed by the mechanism of generation and growth. The C-shaped kinetic isothermal diagrams describe kinetics of direct a®b  hydride transformations. Another type of kinetic diagrams is typical for reverse b®a  hydride transformations, and the rate of these hydride transformations just accelerates with temperature increasing or hydrogen pressure decreasing. Morphological peculiarities of both direct and reverse hydride transformations are described in details.

In the conclusion of the review, there is given a discussion of a unique role of hydrogen concentrational and hydrogen phase stresses in processes of hydride transformations. It has been found out that these stresses are the most important thermodynamic and kinetic factor in the hydride transformation development.

Lev S. Bushnev.^ Hydride shape-memory effects. There was shown a possibility to realize the shape-memory effect in the V–H system owing to the termoelastic and martensite-like mechanisms of the β-hydride (V₂H) precipitation. An additional purification of the initial vanadium of such interstitial nitrides as oxygen and nitrogen is a general condition. An availability in a solid solution a sufficient quantity of these impurities (>0.3 at.%) stimulates forming the surface martensite in despite of a small hydrogen concentration. The martensite lattice is nearly identical to the β-hydride one, but their morphology is different as the precipitation mechanism is different. The surface martensite embrittles vanadium alloys and it makes impossible their using for tensile tests. This result calls the work in which embrittleness of vanadium is connected with the β-hydride precipitation.

The author showed a feasibility of a new shape-memory effect, which is connected with the Gorsky effect in the two-phase systems. This effect has a diffusion mechanism and it may occur in many two-phases alloys where interstitial phases exist. Especially, this effect makes a valuable contribution to the creep deformation of two-phase alloys. The author hopes that this work will stimulate further theoretic and experimental investigations of hydrogen influence on mechanical properties of metals.

Victor A. Goltsov and Nicolai N. Vlasenko.^ The hydrogen phase naklep phenomenon and its use in hydrogen treatment of metallic materials. Up-to-date knowledge about the hydrogen phase naklep (HPN) phenomenon is synthesized. First, the initial idea, its experimental confirmation, imagination of the HPN-phenomenon nature and principles of the HPN-treatment are elucidated. Then, HPN effects on metals are discussed in details: strengthening of palladium and niobium in finally completely-degassed, monophase-naklep states; super-strength and high plasticity of finally nondegassed polyphase PdH_x and NbH_x alloys; the mechanisms of strengthening and hydride transformation induced plasticity (hydride TRIP-effect); changes of physical properties and structure of metals during the HPN-treatment; recovery and recrystallization of the HPN-treated palladium and niobium. Finally, we consider practical applications and summarize mechanical properties of some HPN-treated alloys.

Ellina Lunarska. ^ Some hydrogen effects at the metals surface treatment. The segregation of an absorbed hydrogen within the subsurface layers, exhibiting structure, chemistry and properties, different from those of a core, should specially affect the tribology, friction, wear and electrochemical behavior of the metals. The respective experimental data are of a great importance, since they impact in both, a better understanding of the phenomena and the appropriate modification of the environment and the metal surface to achieve desired results. In this paper, some recent experimental results providing the proof and confirmation for some hydrogen assisted surface phenomena are summarized and discussed.

Hydrogen evolves from the oil and lubricants at ambient temperature in the contact with a metal and an oxide. The hydrogen entry and its segregation within the subsurface layer modify the elastic, inelastic and plastic properties of the material surface.

Hydrogen absorbed by the Ti-Al intermetallic compounds at a cathodic polarization facilitates their anodic dissolution rate, at least under the certain conditions.

Electrochemical and/or mechanical activation of the surface of a hardly machined Ti alloy and WC-TiC-Co sintered carbide promotes the hydrogen entry into the metal, at a low hydrogen evolution rate and at an anodic polarization of the metal.

The above phenomena should be taken into account at considering the tribological and wear properties and at establishing the time and energy consuming parameters of electrochemical and electrochemical-mechanical machining. The goal is to select the lubricant or friction materials inhibiting hydrogen evolution and ingress and to elaborate the hydrogen treatment facilitating the dissolution and removal of an excess material at machining.

Evolution of hydrogen collected in the subsurface layer under the controlled conditions can be used for pure lubrication.

Oleg N. Senkov and Fransis H. (Sam) Froes.^ Hydrogen as a temporary alloying element in titanium alloys. Use of hydrogen as a temporary alloying element in titanium alloys is an attractive approach for controlling the microstructure and thereby improving final mechanical properties, and also for enhancing processability including working, machining, sintering, compaction, etc. In the present paper, the status of the methods and applications of thermohydrogen processing (THP) to titanium alloys is reviewed. Effects of hydrogen alloying on the phases present, their composition, and the kinetics of phase reactions are considered. The effect of hydrogen on the hot workability, composite- and powder-metallurgy-product processing, and microstructure modification of conventional alloys and intermetallics, including production of submicrocrystalline structures is discussed. Thermohydrogen processing has clear advantages in the development of improved microstructures and mechanical properties. In the case of near net shapes it is the only method for significant microstructural modification. It allows energy savings in processing to final products by improving the processability.

Shaoqing Zhang. ^ Hydrogenation behaviour, microstructure and hydrogen treatment for titanium alloys. The hydrogenation behaviour of Ti and its alloys (a -, b - and (a + b)-types), the effect of hydrogenation temperature and time on hydrogen content in hydrogenated specimens and the microstructural changes during the hydrogenation process were studied. Besides, the procedures of hydrogen treatment and the mechanisms of microstructural modification for a cast Ti-6Al-4V alloy were set forth. It is shown that the hydrogen treatment greatly changes the microstructure of the cast Ti-6Al-4V alloy and consequently improves its mechanical properties.

Alexander A. Ilyin, Boris A. Kolachev and Vladimir K. Nosov. ^ The achievements and prospects of hydrogen technology of titanium alloys production and treatment. Hydrogen technology includes hydrogenation of a metal up to a certain concentration, carrying out technological operations utilizing the favourable effects caused by hydrogen and vacuum annealing for decreasing hydrogen concentrations up to the safe level in order to avoid the hydrogen embrittlement in the course of their usage. The examples of an effective use of hydrogen technology under creating new alloys, the production of wrought semifinished items from hard-deforming titanium alloys, fastening parts, welding joints, shapes casting, utilization of titanium scrap are presented. Hydrogen technology allows to lower metal capacity and energetic expenses of titanium manufacture, to secure ecological purity of technological operations, to increase operational reliability of titanium parts and designs, and, in some cases, to receive unique properties combination, which cannot be achieved by other methods of processing.

Georgy P. Borisov and Franko M. Kotlyarsky. ^ Hydrogen in technologies for aluminium alloys casting. >Hydrogen is one of the most effective agent which has a dramatic affect on dynamics and directions of the development of technological processes.

Results of numerous investigations and an accumulated empirical experience create a reliable scientific and technological background of a struggle with an appearance of the negative influence and effective utilization of a positive role of hydrogen in controlling processes to produce a wide nomenclature of aluminium castings with a desirable level of quality and properties.

A unique ability of hydrogen not only affect on properties of cast Al alloys but serve as a main control parameter for a number of principally new technological processes which by right can be named ‘hydrogen casting technologies’.

At the same time, it is obvious that a lot of aspects of the problem of hydrogen treatment of liquid and solidifying aluminium alloys remains insufficiently studied. In particular, there can be noted very limited studies of the influence of hydrogen dissolved in a solid alloy on transformations in a casting in the process of heat treatment; the role of hydrogen in the processes of transfer of structural peculiarities from a hydrogen-containing product to a metal of the next casting.

Salvatore Miraglia and Daniel Fruchart.^ Systematisation and pecularities of hydride crystal structures forming under the interaction of hydrogen with intermetallics. Crystal and magnetic structures of hydrides (deuterides) of selected binary or ternary metal compounds as determined by neutron diffraction analysis are reviewed. The distribution of hydrogen (deuterium) atoms in the host metal structure is characterized by a preferential occupation of tetrahedral or octahedral interstitial sites. The metal atom arrangements are usually similar to those of the starting alloys with an expanded lattice and sometimes the crystal symmetry may be reduced. Simple models that have been developed to rationalise hydrogen (deuterium) site occupancies are reviewed. The effects of hydrogenation on the structural and magnetic (electronic) properties are discussed. Selected examples and results related to several series of intermetallic hydrides have been chosen to illustrate different structural characteristics.

Kiyoshi Aoki. ^ Hydrogen induced amorphization of intermetallics. This article describes hydrogen-induced amorphization (HIA) of intermetallics, i.e., the formation of amorphous alloys by hydrogenation. We focus on HIA of the C15 Laves AB₂. The formation conditions of amorphous alloys, a correlation between the stability of GdM₂ (M=Fe, Co, Ni) compounds and the structure of a-GdM₂H_x, the factor controlling HIA in the AB₂ compounds and the mechanism of HIA in the RM₂ compounds are discussed and presented. Chemical compositions and crystal structures of amorphizing intermetallics are tabulated.

Victor A. Goltsov, Sergei B. Rybalka, Daniel Fruchart, Victoriya A. Didus.^ Kinetics and some general features of hydrogen induced diffusive phase transformations in Nd₂Fe₁₄B type alloys. In this review there are generalized experimental data on the kinetics of direct and reverse hydrogen-induced diffusive phase (HIDP) transformations in alloys of the Nd₂Fe₁₄B type being the basis of the HDDR technology. There are discussed general regularities of these transformations: their most general mechanisms, types of isothermal kinetic diagrams of both direct and reverse HIDP transformations, mechanisms of temperature and hydrogen pressure influence on the kinetics. There is made a conclusion that hydrogen is not only a necessary thermodynamic condition, but the most important kinetic factor characterizing general features of HIDP transformations.

Hirohisa Uchida. ^ modifications of hydrogen storage alloys and their applications in recent hydrogen technology. In this review, the general aspect of the surface process of hydrogen on the metal surface is given with respect to both the hydrogen absorption by metals in the H₂ gas phase and electrochemical process. And then typical effects of surface modifications of hydrogen storage alloys by chemical contamination on the initial activation and hydriding kinetics are demonstrated. Emphasis is made on the mechanisms and crucial role of the dissociation of covalent molecules of H₂ and H₂O in the initial activation and hydriding of hydrogen storage alloys. Recently, surface modifications such as fluorination and alkaline treatment of the surface of hydrogen storage alloys have been found very effective for the activation and against surface contamination. On the basis of these results, two typical applications are described: (1) the fluorinated hydrogen storage alloys with a high durability against CO gas. These alloys have been developed under the Eco-Energy City Project of the New Energy Development Organization (NEDO), Japan, and are applied to the manufacturing process of the double walled vacuum insulated tubes (DWVIT) for heat transport systems with an extremely high heat insulation effect, less than 5% of that of conventional heat insulation systems. These alloys are also expected to be applied to H₂ fuel cell systems as a H₂ gas supplier; (2) the alkaline pretreated negative electrodes of nickel-metal hydride(Ni-MH) rechargeable battery with enhanced charge and discharge rates. This effect was applied to recent world solar vehicle rallyes using a large scaled Ni-MH battery.

Yasunori Hayashi and Tsutomu Ishikawa.^ Effects of hydrogen inclusion on electrical properties of metal oxides and nitrides. Most of metal oxides and nitrides are semiconductors and show interesting electrical and optical properties depending on various imperfections in the compounds. Hydrogen atoms included in these compounds interact with various defects and modify the electronic structure of the compounds. The modification of the electronic structure by hydrogen inclusion is reviewed for some metal oxides and nitrides. Change of photo-electrochemical properties of a niobium oxide and electrical conduction properties of a copper nitride by hydrogen inclusion are discussed in some detail as an example of the hydrogen-induced modification. Hydrogen inclusion in both cases created new impurity donor states in the band gap of the compounds and showed specific change of material properties.

Louise Jalowiecki-Duhamel.^ Hydrogen treatment of non-metallic catalytic materials. Under H₂ treatment, mixed oxides (Cu–Cr–O, Cu–Al–O, Cu–Zn–O, CeNi_XO_y, CeCu_X O_y), heteropolycompounds, and MoS₂ type catalysts become catalytic hydrogen reservoirs. Hydrogenation of 2-methylbuta-1,3-diene (isoprene) under helium flow in the absence of gaseous hydrogen is used to provide evidence and titrate reactive hydrogen species (H*) present in the solids. The hydrogen reservoir capacity depends on the pretreatment temperature under H₂, which corresponds to the creation of anionic vacancies in the solid by the loss of H₂O or H₂S. The anionic vacancies created in the bulk and at the surface of the solid are able to receive hydrogen in a hydridic form according to a heterolytic dissociation of H₂ (X^2- Mⁿ⁺ o + H₂ ® XH^- Mⁿ⁺ H^- with X = O or S). In relation to the solid structure and the existence of bridged anionic vacancies, particular active sites ^XM-^YM’ (where x and y are the number of unsaturations on each cation) involving reactive hydrogen are created. The configuration of the principal cation (^XM) is the prerequisite condition to observe an activity while the second cation (^Y M’), in close interaction, brings its contribution to the selectivity. The active sites responsible for different catalytic functions correspond to different configurations of anions and anionic vacancies, i.e., different active site structures. Moreover, the hydrogen species presenting marked diffusion properties, the active site has a dynamic behaviour.

Andrzej Zielinski. ^ Hydrogen degradation of some hydride-forming metals and their alloys. The hydrogen effects on mechanical properties of four metals and their alloys are described, namely: titanium, Ti-Al-Nb, Ti-Al-V, Ti-Al-Sn, Ti -Al-Mo, Ti-Mo and Ti-V alloys; zirconium, Zr-Sn and Zr-Nb alloys; vanadium, V-Nb, V-Ti and V-Cr alloys; niobium and its alloys. Hydrogen degradation is shown to manifest mainly as the hydrogen delayed cracking and loss in plasticity. The process of formation and decomposition of hydride phases is discussed as the most likely cause of fracture.

Igor K. Pokhodnya and Valentin I. Shvachko. ^ Hydrogen in welding processes. The results of new investigations on the problem of hydrogen in welding processes are reviewed. The following aspects of this problem are considered: abnormal hydrogen absorption by a melted metal during welding; hydrogen embrittlement of steels and welds; physical nature of hydrogen induced cold cracks (HICC) as the most dangerous defect in welded joints of structural steels.

Victor A. Goltsov. ^ New paradigm of materials science. A new conception about hydrogen as an element which is the basis of hydrogen energy and technology has been developed. This new conception based on the experimentally discovered phenomenon of a controllable hydrogen phase naklep (i.e., HPN-phenomenon) asserts that hydrogen may be used as a universal external agent for hydrogen technologies of metal treatment to improve their physical and technical properties, to create new metallic materials with special properties.

Victor A. Goltsov. ^ Classification of hydrogen treatment of materials. A refined version of HTM-classification in the line with the last advances of the HTM-theory and HTM-technology is suggested.

Lyudmila F. Goltsova.^ HTM–community: history and up-to-date status in the world hydrogen movement. The review shortly sums up the history of HTM-community developing as an important part of the world hydrogen movement. There are analyzed the history and up-to-date status of interrelation between hydrogen energy community and hydrogen–materials one. Last years, great advances in this cooperation have come about thorough activities of Permanent Working International Scientific Committee on Hydrogen Treatment of Materials under the auspices of International Association for Hydrogen Energy. The conclusion is made that promoting this cooperation will be a responsible task of hydrogen movement in the 21^st century.

For Hydrogen Economy development being in advance in the 21^st century, the World Hydrogen Movement should steadily pay special attention to all materials–hydrogen problems.

First, there should be created novel more stable to hydrogen degradation structural materials and novel preventive technologies. This problem being one of the fundamentals of safety is of an absolutely great importance. Really, it cannot be allowed that the hydrogen economy entering into the mankind life would be rejected by the public relation because of some unforseen case, some new ‘Hindenburg syndrom’.

Secondly, hydrogen economy will require advanced functional materials (hydrides, membranes, electrodes, magnets and catalytic materials, etc.) and adequate technologies of a new generation. More and more wide use of hydrogen treatment (side by side with other kinds of treatments) will allow to extend possibilities of Hydrogen Materials Science and Engineering, and will greatly promote hydrogen economy development in new directions.

At last, it is necessary to emphasize the importance of systematic intimate communication between two hydrogen world communities: hydrogen energy community, as it is, and materials-hydrogen one. Now additional possibilities in this area appear due to the activities of the Permanent Working International Scientific Committee on Hydrogen Treatment of Materials under the auspices of International Association for Hydrogen Energy.

The 13^th WHEC, Beijing, 2000

El ingreso exitoso a la vida de una economía ecológicamente limpia basada en el hidrógeno y la esperada transición hacia la civilización del hidrógeno en el futuro, requieren la creación de nuevos materiales estructurales para el hidrógeno; materiales más funcionales y avanzados, como así también nuevas tecnologías especiales para su producción y tratamiento.

En respuesta a los requerimientos de estos tiempos modernos, científicos y especialistas reconocidos a nivel mundial de 10 países han contribuido en la realización de este libro – el primero que revisiona el origen y el desarrollo de un nuevo campo de la Ciencia e Ingeniería de los Materiales, conocido ahora como Tratamiento de Materiales con Hidrógeno (TMH).

Esta obra da un tratamiento general al conocimiento relacionado con la teoría TMH y las tecnologías TMH. En ella se consideran las estructuras y las características de los sistemas material–hidrógeno (MH), sus capas superficiales y subsuperficiales, las películas finas y los sistemas multicapas. Se generaliza la naturaleza sinérgica difusivo-cooperativa de los sistemas MH, se analizan sus particularidades termodinámicas y cinéticas, y se describen los fenómenos relacionados. Por primera vez se consideran sistemáticamente las transformaciones de fase inducidas por el hidrógeno: su naturaleza, clasificación, mecanismos, cinética, morfología, influencia en la estructura, en las propiedades y su uso en TMH. Además en la obra se resume el conocimiento relacionado con las tecnologías TMH para los materiales deformados, fundidos y sintetizados, tales como paladio, niobio, vanadio, aleaciones basadas en el Al, Ti, Fe, materiales intermetálicos y no-metálicos. Se describen los logros de las tecnologías TMH, que permiten mejorar las características de las estructuras y sus propiedades mecánicas, físicas y catalíticas. El libro también centra cierta atención en la degradación por hidrógeno de las propiedades de metales, aleaciones y aceros.

Este libro se piensa para los científicos de las ciencias de materiales, los físicos, los químicos, los ingenieros y otros miembros activos del movimiento mundial del hidrógeno. Será altamente útil para los estudiantes, los diplomados y los científicos jóvenes que están interesados en la estructura, las características y las aplicaciones de los sistemas material–hidrógeno.

L'avènement réussi d'une économie basée sur l'hydrogène, énergie écologiquement propre, ainsi que la transition attendue vers une civilisation fondée sur l'hydrogène dans le futur, nécessitent la découverte et la mise au point de matériaux innovants, de nouveaux matériaux stables dont l'hydrogène est un des constituants, de matériaux utilitaires d'avant garde, de nouvelles technologies spéciales en vue de leur production et traitement.

En réponse à ces nécessités des temps modernes, des scientifiques de renommée internationale et des spécialistes de 10 pays ont contribué à ce livre – premier livre traitant de l'origine et du développement d'un nouveau thème en science des matériaux et ingénierie maintenant désigné sous le nom “Hydrogen Treatment of Materials” (HTM).

Le livre transmet le savoir lié à la théorie et la technologie HTM. Les structures et propriétés de systèmes matériaux–hydrogène (MH), de leurs couches et sous-couches de surface, de films minces et multicouches y sont présentées. Des effets de synergie induits par la nature des systèmes MH sont généralisés pour expliquer les phénomènes de diffusion. Leurs particularités thermodynamiques et cinétiques sont analysées et les phénomènes qui en résultent sont décrits. Pour la première fois, des transformations de phase induites par l'hydrogène sont systématiquement considérées: nature, classification, mécanismes, cinétiques, morphologie, influence sur la structure, les propriétés et l'utilisation en HTM. L'état de l'art lié aux technologies HTM y est résumé, pour des matériaux déformés, fondus et synthétisés, comme le palladium, le niobium, le vanadium, des alliages à base de Al, Ti, Fe, des intermétalliques, des matériaux non-métalliques; le but des technologies HTM, améliorant leurs structures, leurs propriétés mécaniques, physiques et catalytiques est décrit. Une certaine attention est portée sur la dégradation, liée à l'hydrogène, des métaux, alliages et aciers.

Le livre est destiné à l'usage des scientifiques en science des matériaux, aux physiciens, chimistes, ingénieurs et autres membres actifs du mouvement mondial hydrogène. Il sera extrêmement utile aux étudiants, aux scientifiques jeunes et confirmés qui sont intéressés par la structure, les propriétés et les applications des systèmes métal–hydrogène.

Ein zukünftiges Leben, welches durch eine ökologisch saubere Wasserstoffwirtschaft gekennzeichnet ist und auf dem täglichen Umgang mit Wasserstoff basiert, setzt die Entwicklung von neuen wasserstoff-kompatiblen Struktur- und Funktionswerkstoffen voraus. Darüber hinaus werden kosteneffektive Technologien für die Produktion und die Weiterverarbeitung von Wasserstoff benötigt.

Als Reaktion auf diese in der nahen Zukunft liegenden Anforderungen, haben weltbekannte Wissenschaftler und Experten aus 11 verschiedenen Ländern mit ihren Artikeln zu diesem Buch beigetragen – das erste Buch in einer Serie, welches die Entwicklungen von Wasserstofftechnologien im Bereich der Materialwissenschaften umfassend darstellen wird. Dieses Gebiet ist unter dem Namen “Behandlung von Materialien mit Wasserstoff”, oder “Hydrogen Treatment of Materials” (HTM) bekannt geworden ist.

Das vorliegende Buch gibt einen ausgezeichneten Überblick über den gegenwärtigen Stand der HTM-Theorie und HTM-Technologie. Die dargestellten Strukturen und Eigenschaften umfassen Wasserstoff an Oberflächen, in oberflächennahen Atomlagen, in dünnen Schichten und in Multilagen. Die einzelnen Schritte und die kooperativen Eigenschaften der Wasserstoffdiffusion werden behandelt, zusammen mit ihren thermodynamischen und kinetischen Eigenschaften. Zum ersten Mal werden die wasserstoff-induzierten Phasenübergänge systematisch beschrieben, einschliesslich ihrer Klassifikation, Kinetik, Morphologie und ihres Einflusses auf Struktur und Eigenschaften von HTM. Das gegenwärtige Verständnis von HTM-Technologien hinsichtlich verformerter, gussartiger und synthetischer Materialien, unter Einbezug von Palladium, Niobium, Vanadium, Legierungen auf der Basis von Al, Ti, Fe, intermetallische Verbindungen und von nicht-metallischen Materialien, wird ebenfalls dargestellt. Die Erfolge auf dem Gebiet der HTM-Technologien, insoweit wie sie einer Verbesserung der strukturellen, mechanischen, physikalischen und katalytischen Eigenschaften dienen, sind aufgezeigt. Einige Aufmerksamkeit wird auch der Wasserstoffversprödung von Metallen, Legierungen und Stählen gewidmet.

Das vorliegende Buch wendet sich an Materialwissenschaftler, Physiker, Chemiker, Ingenieure und andere aktive Mitglieder der weltweiten Wasserstoff Gemeinde. Es wird auch für Studenten, Postdokotranden, und junge Wissenschaftler sehr nützlich sein, die an der Struktur, an den Eigenschaften und an Anwendungen von Material–Wasserstoff Systemen interessiert sind.