THERMAL STABILITY AND DEUTERIUM ABSORPTION AT ROOM TEMPERATURE OF Ti36Zr40Ni20Pd4 QUASICRYSTAL
Ti-Zr-Ni quasicrystals can absorb a large amount of hydrogen, so have strong application potential in the hydrogen energy field and international thermonuclear experimental reactor (ITER) program. However, the hydrogenation of the quasicrystals is often hindered and even poisoned due to their surface oxidation. To inhibit the oxidation, Pd has been selected, because of its catalysis to hydrogen absorption, as a minor alloying element in Ti-Zr-Ni quasicrystals. In this paper, the Ti36Zr40Ni20Pd4 alloy was designed and its thermal stability and room-temperature deuteration were studied with XRD, DSC, OM, XPS and gas-solid reaction measurement apparatus. The XRD result shows that a single icosahedral quasicrystal (IQC) phase with a quasilattice constant a(R)=0.5174 nm was formed in the alloy by suction-casting method, which is metastable and transforms to conventional crystals tI-Zr2Ni and C14-TiZrNiPd (MgZn2 type) phase at about 400 degrees C. The deuteration test below the transformed temperature indicates that the alloy can absorb deuterium up to a large concentration of 11.0 mmol/g (corresponding to 2.2%H, mass fraction) at room temperature after vacuuming and heating activation without any surface treatment. Once fully activated, the IQC can load deuterium rapidly with an absorption rate of 0.030 s(-1) at ambient temperature, and has the quasilattice constant with about 5.5% expansion after two absorption cycles. The Ti36Zr40Ni20Pd4 IQC has better activation property and hydrogen capacity than the Ti40Zr40Ni20 IQC, which shows the catalyzing function of Pd.
Acta Metallurgica Sinica
Science and Technology Development Foundation of China Academy of Engineering Physics [2007A07002]