Investigation On Gas Absorption Characteristic And Application Of ZrV Based Alloy

Getter material can be used to absorb the active gas molecules in the vacuum environment to maintain and improve the vacuum degree of the sealed-off devices without extra vacuum-pump. With the rapid technological development, the smaller and compact vacuum devices are significantly required for many electric applications. And the getter materials with high absorption performance are highly demanded. The damage of heat sensitive components can be caused during high temperature activation process of the traditional getters, which may seriously reduce the reliability and lifetime of the sealed-off devices. There is an urgent need to improve the activation efficiency and reduce the activation temperature of the getter material. With the increasingly extended service time of vacuum device, the repeated activation performance of the getter material also needs to be improved.In this thesis, we aimed to develop a novel high-performance getter material based on ZrV alloy to meet the requirements of engineering application. The research work was carried out to explore the relationship between the micro-structure and the absorption performance of getter material, as well as the activation property. The phase composition, the gas （H2, CO） absorption kinetics, the activation efficiency and the repeated activation performance of the ZrVFe alloy were systematically studied in order to investigate the influence of alloy phase composition on the absorption property. Then the ZrV based alloy was modified by elements substitution and the addition of the rare earth in order to improve the gas （H2, CO） absorption kinetics and increase the activation efficiency. The sintered porous getter was fabricated with the ZrVMnCe alloy to make an engineering application attempt. The main contents of the thesis are as following:（1） Based on ZrV₂-ZrFe₂-Zr ternary alloy phase diagram, the ratio of Zr, V, Fe in the alloy was designed. The Zr56.97xV35.85yFe7.18z（x=1,y=1,z=1; x=1.2,y=l,z=1; x=0.8,y=1,z=1; x=l,y=1.4,z=1; x=1,y=0.6,z=1; x=1,y=1,z=1.5; x=1,y=1,z=0.5） alloys were fabricated by vacuum-smelting technology. The alloys were composed of α-Zr phase and C15 Laves phase when z=1 and z=0.5. And the gas （H2, CO） absorption property was improved with the increasing of the C15 Laves phase. The alloy was composed of a-Zr phase, C15 Laves phase and C14 Laves phase when z=1.5. The gas （H2, CO） absorption property was obviously improved by the C14 Laves phase. The H2 absorption speed reached up to 2137.9 cm3/s·g, which was 71.9% higher than that of the Zr56.97V35.85Fe7.18 alloy. And the CO absorption speed reached up to 1300.6 cm3/s·g which was 59.3% higher than that of the Zr56.97V35.85Fe7.18 alloy. By the calculation of the gas diffusion activation energy, it was found that the absorption kinetics of the alloy was improved by the C14 Laves phase. The H2 and CO diffusion activation energy were decreased to 1.95 kcal/mol and 5.22 kcal/mol when z=1.5. The repeated activation times and activation efficiency were also increased with the increasing of V element.（2） The Zr56.97V35.85X7.18 （X=Cr、Mn、Fe、Co、Ni） alloys were fabricated by the elements substitution in order to increase the content of C14 Laves phase in the alloy and improve the absorption kinetics. It was found that the content of C14 Laves phase increased by the substitution of Cr、Mn、Co、Ni through XRD full spectrum analysis and the gas （H2, CO） absorption property was improved as well. Among them, the substitution of Mn element showed the highest improvement of absorption performance. The H2 absorption speed of Zr56.97V35.85Mn7.18 alloy reached up to 2295.7 cm3/s·g which was 84.6% higher than that of Zr56.97V35.85Fe7.18 alloy, and the CO absorption speed reached up to 1349.0 cn3/s·g which was 65.2% higher than that of the Zr56.97V35.85Fe7.1g alloy. The H2 and CO diffusion activation energy of Zr56.97V35.85Mn7.18 alloy were deceased to 1.57 and 5.00 kcal/mol, respectively.（3） The effect of the rare earth element addition, such as La、Ce、Pr、Nd on the phase composition, the absorption performance and the activation property of the ZrV based alloy was further investigated. The Zr56.97V35.85Mn7.18Re2.65 alloys were composed of a-Zr phase, C15 Laves phase, C14 Laves phase and new RE2O3 phase through XRD full spectrum analysis. The gas （H2, CO） absorption property was obviously improved by the addition of La, Ce, Pr, Nd. And the addition of Ce element showed the highest improvement of absorption performance. The H2 absorption speed of Zr56.97V35.85Mn7.18Ce2.65 alloy reached to 2479.7 cm3/s·g which was 8.01% higher than that of Zr56.97V35.85Mn7.18 alloy, and the CO absorption speed reached to 1494.2 cm3/s·g which was 10.8% higher than that of the Zr56.97V35.85Mn7.18 alloy. The H2 and CO diffusion activation energy of Zr56.97V35.85Mn7.18Ce2.65 alloy were decreased to 1.35 and 4.24 kcal/mol, respectively. The activation efficiency of ZrV based alloys was significantly increased by the addition of La, Ce, Pr, Nd. Besides, the repeated activation performance was improved to some extent as well.（4） The feasibility of the Zr56.97V35.85Mn7.18Ce2.65 alloy for engineering application was explored. The Zr56.97V35.85Mn17.18Ce2.6560%-Zr40% sintered porous getter was fabricated via the metal injection molding process and vacuum sintering process. The solvent and thermal condition, as well as the sintering process of the sintered porous getter was optimized by using a series of analysis methods, such as SEM, DTA-TG, porosity, specific surface area and carbon content. The H2 absorption speed of the as-prepared Zr56.97V35.85Mn7.18Ce2.6560%-Zr40% sintered porous getter reached up to 1454.2 ml/s·g which was 19.4% higher than that of the traditional commercial Zr56.97V35.85Fe7.i860%-Zr40% getter, and the CO absorption speed reached up to 901.9 ml/s·g which was 9.6% higher than that of Zr56.97V35.85Fe7.1860%-Zr40% getter. The activation efficiency of the Zr56.97V35.85Mn7.18Ce2.6560%-Zr40% sintered porous getter was higher than Zr56.97V35.85Fe7.1860%-Zr40% when the activation temperature was 450℃.