Huang Huogen

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 re- actor (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, be- cause of its catalysis to hydrogen absorption, as a minor alloying element in Ti-Zr-Ni quasicrys- tals. 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 measure- ment apparatus. The XRD result shows that a single icosahedral quasicrystal (IQC) phase with a quasilattice constant aR=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 . The deuteration test below the transformed temperature indicates that the al- loy 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.

Deuterium Storage of Ti39Zr38Ni17Pd6 Icosahedral Quasi-crystal

Abstract Ti-Zr-Ni-based icosahedral quasicrystals (IQCs) are a type of hydrogen storage materials with promising application in the fields of hydrogen energy and nuclear fusion energy. In the present paper, the preparation of Ti39Zr38Ni17Pd6 IQC and its deuterium storage properties were investigated by XRD, TEM, XPS analysis and a gas-solid reaction system. Results show that the saturation concentration of absorbing deuterium for the alloy at room temperature reaches near 11 mmol·D2/g·M (D2 means deuterium molecular and M the metal), exceeding those of Zr2Fe and ZrCo alloys. After a few absorption/desorption cycles, no phase transformation is observed, but the quasilattice displays a remarkable expansion of 6.37% after full D intake. The binding energy rise of 0.2 eV for Ti and 0.6 eV for Zr, caused by the introduction of saturated deuterium atoms, provides the evidence of the preferential location of deuterium near Zr and Ti in quasicrystals of this kind. The possible existence of a lower D desorption equilibrium pressure with

Effect of Pd Substitution on Phase Formation and Stability in Ti-Zr-Ni Quasicrystalline Alloys

Abstract Pd can be used as an adding element to improve hydrogenation properties of Ti-Zr-Ni quasicrystalline alloys. However, the action mechanism of Pd addition is unclear yet. The effects of Pd substituting Ti and Zr in Ti45Zr38Ni17 and Ti40Zr40Ni20 alloys were studied by means of XRD, TEM and DSC examination. The results show that icosahedral quasicrystal can be formed purely through 4%∼6% Pd substitution for Ti or 4% for Zr in the Ti45Zr38Ni17 alloy, as well as 3%∼4% for Ti or possibly below 3% for Zr in the Ti40Zr40Ni20 alloy. This indicates a higher substitution limit for Ti in order for the heritance of the quasicrystal phase. Two derived quasicrystals Ti39Zr38Ni17Pd6 and Ti36Zr40Ni20Pd4 can be transformed into crystalline phases after annealing at 400 °C, demonstrating their lower thermo-stabilities in comparison to such Ti-Zr-Ni alloys being stable at about 700 °C. Both the replacement tendency and the decrease of the thermostability of quasicrystal phase might be ascribed to appropriate atomic size of Pd.