High capacity hydrogen storage: Basic aspects, new developments and milestones

Hydriding and dehydriding characteristics of Mg-LaNi5 composite materials prepared by mechanical alloying

This paper reviews the present performances of intermetallic compound families as materials for negative electrodes of rechargeable Ni/MH batteries The performance of the metal-hydride electrode is determined by both the kinetics of the processes occurring at the metal/solution interface and the rate of hydrogen diffusion within the bulk of the alloy Thermodynamic and electrochemical properties for each hydride compound family will be reported The steps of hydrogen absorption/desorption such as charge-transfer and hydrogen diffusion for evaluating the electrochemical properties of hydrogen storage alloys are discussed Exchange current density (I
 0) and hydrogen diffusion coefficient (D
 H) are the two most important parameters for evaluating the electrochemical properties of metal hydride electrode The values of the two parameters for a number of hydrogen storage alloys are compared The relationship between alloy composition and electrochemical properties is noted and evaluated

Kinetic and thermodynamic studies of hydrogen storage alloys as negative electrode materials for Ni/MH batteries: a review

Effects of microencapsulation on the electrode behavior of Mg2Ni-based hydrogen storage alloy in alkaline solution

Structural disorder in expanded “ c ” parameter ReBa 2 Cu 3 O 7− x (Re=rare earth) thin films grown by radio-frequency magnetron sputtering has been quantified by undertaking Rietveld refinements of X-ray data In order to understand why the disorder occurs, we have focused on determining the factors which influence the amount of disorder, such as growth conditions, rare-earth ion size, and overall composition To understand more about the disordering mechanism, some additional comparative growth experiments with bulk samples have been carried out For YBa 2 Cu 3 O 7− x films, low oxygen growth pressures and temperatures give rise to disordered films with enlarged “ c ” parameters and degraded superconducting properties There is a correlation between (00 l ) to (006) peak intensity ratios and the “ c ” parameter with the amount of disorder in the films In the most disordered YBa 2 Cu 3 O 7− x films, as much as 14% Y and Ba cation exchange, and a large fraction of apical oxygen vacancies have been found The effect of smaller rare-earth ions is to decrease the amount of cation disorder However, as was shown for YbBa 2 Cu 3 O 7− x films, there are structural vacancies in the rare-earth site and T c is reduced A model for the disordering mechanism is proposed based on the kinetic and thermodynamic driving forces for the growth of YBa 2 Cu 3 O 7− x from the disordered, precursor phase, Re 033 Ba 066 CuO y 

Studies of structural disorder in ReBa2Cu3O7−x thin films (Re=rare earth) as a function of rare-earth ionic radius and film deposition conditions

Investigations on the structural and hydrogenation characteristics of LaNi5, HoNi5, GdNi5, SmNi5, MmNi5, and CFMmNi4.5Al0.5 thin films

The synthesis and hydrogenation behaviour of some new composite storage materials: Mg-xwt% FeTi(Mn) and La2Mg17-xwt% LaNi5

The hydrogenation behaviour of RNi5 type materials in thin film and bulk form

This paper seeks to review the hydride/hydrogen technology and to describe the work being done in our laboratory for the development of rare earth pentanickelide (RNi5) type solid state materials for hydrogen storage. To start with a brief review of the basic theme for solid state storage mode of hydrogen has been given. The salient features of this storage mode have been outlined. For the RNi5 type materials, more emphasis has been laid on the discussion of a new result obtained by us. It has been found that it is possible to synthesise amorphous phases of RNi5 (LaNi5, MmNi5) materials and this phase has been found to have a higher hydrogen storage capacity. Another new result in regard to the RNi5 type hydrides is relating to the variation of electrical resistivity (P) as a function of hydrogenation time (t). The curious nature of P-t curve has been explained in terms of the variation of electronic density of states as a result of the hydrogenation process.

K. Ramakrishna

Papers

Investigations on the structural and hydrogenation characteristics of LaNi5, HoNi5, GdNi5, SmNi5, MmNi5, and CFMmNi4.5Al0.5 thin films

The synthesis and hydrogenation behaviour of some new composite storage materials: Mg-xwt% FeTi(Mn) and La2Mg17-xwt% LaNi5

The hydrogenation behaviour of RNi5 type materials in thin film and bulk form

Solid State Materials for Hydrogen Storage

Investigations on the formation of new structural phases through stoichiometric deviations on Y sublattice in Y1Ba2Cu3O7