METAL-HYDROGEN SYSTEMS IN THE HIGH-PRESSURE RANGE

The report is devoted mainly to the progress achieved in metal-hydrogen and metaldeuterium systems in the high pressure range since 1976. Emphasis is laid upon ternary systems with Ni and with Pd as basic component, and admixtures of Fe and Co (in case of Ni) or Rh and Ni (in case of Pd). From the results of such alloy series' the conditions of hydride formation of the admixed component in pure state can be extrapolated. Following this line hydrides of Co and of Rh could be obtained, although under rather hard conditions (65 kbar at 325 °C in case of Co, 40 kbar at 250 °C in case of Rh). Similarly the formation of Mo hydride was observed at 65 kbar and 350°C. New investigations on the – H system were directed to the hysteresis between hydride formation and decomposition, and to the magnetic behaviour at low temperatures. With the ternary system Pd – Ni – H higher transition temperatures of superconductivity could be obtained than with Pd – H at comparable compositions. New methods for application under high hydrogen pressures and some results of these are presented: a miniaturized device for “in situ” magnetic measurements, a cylinder-piston device for measuring absorption and desorption isotherms, a twin calorimeter, a galvanic cell, and a relaxation method for diffusion coefficients. Application of this method to PdHn and PdDn (– 65 to 0°C) showed that the Fick's diffusion coefficients decrease to rather low values when n→l. © by Akademische Verlagsgesellschaft