PADOVA UNIVERSITY AND CNISM

HYDROGEN GROUP

Settore Materiali-Dipartimento di Ingegneria Meccanica (DIM)
Dipartimento di Fisica (DF)

The Hydrogen Group of Padova University has been studying since some years materials for solid state hydrogen storage. Our laboratory has facilities for the synthesis of materials (high energy ball milling) and for their morphological and structural analysis (X-ray diffraction and porosimetry). A Sievert's volumetric type Gas Reaction Controller (supplied by Advanced Materials Co., USA) is currently used to study absorption/desorption kinetics and thermodynamics of the materials of interest. The GRC allows:

1. Fully automatic and manual data acquisition of absorption/desorption kinetics and absorption/desorption pressure-composition isotherms (PCI)).

2. Programming of operations in sequence (up to 12) even cyclic form

3. Thermoregulation: both contant temperature and temperature ramps.

The working values for temperature and hydrogen pressure (up to 500 °C and up to 200 bar, respectively) allow to study materials even in extreme conditions .

The Sievert's type Gas Reaction Controller used in the laboratory	Gas Reaction Controller control panel from which it is possible to follow the measurements in real time

Examples are shown in the following of hydrogen desorption (a) and of pressure-composition isotherms (b) measurements carried out at different temperatures on Mg88Ni11Fe1 powder samples prepared by high energy milling. From figure (a) it is evident the improvement of desorption kinetics by increasing the temperature. The effect of temperature on the equilibrium pressure of absorption and desorption processes is evidenced in figure (b). The two plateaux are due to the formation of two different types of hydrides. The physical meaning of the plateau is explained at Section metallic hydrides.

figure (a)		figure (b)