Lea. Berlouis et al., A thermal analysis investigation of the hydriding properties of nanocrystalline Mg-Ni based alloys prepared by high energy ball milling, J ALLOY COM, 305(1-2), 2000, pp. 82-89
A thermal analysis study of the hydrogen loading characteristics of nanocry
stalline Mg-Ni alloys (Ni content ranging from 0.1 at% to 10 at%) has been
carried out in 3 MPa hydrogen, employing the techniques of differential sca
nning calorimetry and thermogravimetric analysis (TGA). The measurements co
nfirmed the nonequilibrium state of the samples as prepared by the mechanic
al alloying technique. An enthalpy associated with the stabilisation of the
alloys on first heating in hydrogen was found for all the samples studied.
The magnitude of this enthalpy increased with the nickel content of the al
loy. All the samples showed rapid uptake of hydrogen at 3 MPa pressure, ind
icating that the nickel was thus playing a very active role at the ahoy sur
face in dissociating hydrogen and so enabling more rapid hydride formation
by the alloy. This catalytic activity of the nickel decreased with temperat
ure cycling over the range 80 degrees C to 500 degrees C. Although TGA anal
ysis, carried out at the end of the cycling period, gave the hydrogen conte
nt as 1.1 wt% to 1.7 wt% for the alloys, this is well short of the theoreti
cal amounts expected (7.6 wt% for MgH2), indicating that the samples had be
come deactivated during cycling. No evidence was found of the intermetallic
Mg,Ni prior to or after hydriding. (C) 2000 Elsevier Science S.A. All righ
ts reserved.