| 摘要: | 氣候變遷促使人類尋求可再生的替代能源，以減少對化石燃料的依賴並減少環境影響。氫能作為其中一種乾淨、可再生的能源形式，已成為全球極大關注的重要研究議題。然而，氫的低體積密度和高度易燃性使得氫氣儲存和運輸變得更加困難。因此，開發高儲氫能力的材料已成為熱門的研究領域。
AB5合金是常用的固態儲氫合金。A主要為稀土金屬，例如：鑭系元素；B通常是過渡金屬，例如：鎳。然而，由於稀土金屬價格的日益上漲和稀缺，本研究採用AB3型La–Ca–Mg–Ni基儲氫合金來部分替代AB5合金。一系列不同重量比的AB3型La–Ca–Mg–Ni基儲氫複合材料採用真空感應熔煉製備。並在氬氣氣氛下，連續12小時進行1000℃退火熱處理。使用電感耦合等離子體（ICP）確定合金成分為La0.7Ca0.67Mg1.32Ni9。電子探針顯微分析儀 (EPMA) 顯示本鑄造材料在經過熱處理後元素分佈有明顯改善。X射線衍射分析表明合金中存在兩相，即(La,Mg)Ni3相和LaNi5相。使用基於Sieverts定律的PCI方法，發現25℃時、充氫壓力在5 MPa下，純AB3合金的儲氫容量為1.54wt%。獲得的PCI 曲線顯示出平坦的壓力平台，這表明本研究製備的合金具有高均勻性。相比之下，商業AB5型La0.6Ce0.4Ni5儲氫合金的PCI曲線具有較高的平台壓力，且滯後較大。然而，這兩種合金最終的儲氫能力相似，AB3為1.54 wt%，AB5為1.45 wt%。在復合材料方面，將以不同比例的AB5（20、40、50、60和80 wt%）複合成AB3型La-Ca-Mg-Ni基儲氫複合材料。在所有複合材料中，儲氫容量幾乎相同，約為1.4~1.43 wt%。其中，由50 wt% AB5 組成的複合材料的氫含量最高，為1.43 wt%。然而，差異並不顯著，並且獲得的所有這些氫含量都低於純AB3合金。最後，分別對純AB3和50 wt% AB3和50 wt% AB5的複合材料進行了不同條件的高溫活化。在7 MPa下獲得的儲氫容量分別為1.64 wt%和1.8 wt%，表明兩種合金皆通過高溫成功地提升儲氫容量。在儲氫性能方面，也進一步表明AB3和AB5的複合可能產生協同作用。
;Climate change has impelled humanity to seek renewable alternative energy sources, aiming to reduce dependence on fossil fuels and mitigate environmental impacts. Hydrogen energy, as a clean and renewable form of energy, has emerged as a critically significant research topic of global prominence. However, low volume density and high flammability of hydrogen make its storage and transportation difficult. In this regard, the development of materials with high hydrogen storage capacity has become a popular research field.
AB5 alloy is a commonly used solid hydrogen storage alloy, where A is mainly rare earth metals such as lanthanides, and B is usually transition metals such as nickel. However, due to the increasing price and scarcity of rare earth metals, in this study, La–Ca–Mg–Ni-based AB3 hydrogen storage alloys have been proposed to partially replace AB5 alloys. A series of AB3-type La–Ca–Mg–Ni-based hydrogen storage composites with different ratios were prepared by vacuum induction melting, and heat treatment at 1000°C for 12 hours under an argon atmosphere. Inductively Coupled Plasma (ICP) was used to determine the alloy composition as La0.7Ca0.67Mg1.32Ni9. Electron Probe Micro-Analysis (EPMA) showed a significant improvement in chemical homogeneity after the heat treatment. The X-ray diffraction analysis revealed the presence of two phases in the alloy, namely the (La, Mg)Ni3 phase and the LaNi5 phase. Using the Pressure-Composition-Isotherm (PCI) method based on the Sieverts law, the hydrogen storage capacity of pure AB3 was found to be 1.54 wt% at 25°C, under a hydrogen charging pressure of 5 MPa. The PCI curve of the AB3 obtained shows a flat pressure plateau, thus suggesting a high homogeneity of the alloy prepared in this study. In contrast, the PCI curve of the commercial AB5-type La0.6Ce0.4Ni5 hydrogen storage alloy has a higher plateau pressure, with a bigger hysteresis. However, the final hydrogen storage capacity of these two alloys were similar at 1.54 wt% for AB3, and 1.45 wt% for AB5. In terms of composites, different ratios of AB5 (20, 40, 50, 60 and 80 wt%) were composited into AB3-type La–Ca–Mg–Ni-based hydrogen storage alloy. In all of AB3-type La–Ca–Mg–Ni-based composites, the hydrogen storage capacities were nearly the same, about 1.4~1.43 wt%. Among all of composites, the one consisting of 50 wt% of AB5 had the highest hydrogen content of 1.43 wt%. However, the difference was not significant, and all these hydrogen contents obtained were lower than that of the pure AB3 alloy. Finally, the different conditions of high-temperature activation have been performed on pure AB3 and composite with 50 wt% of AB3 and 50 wt% of AB5. The hydrogen storage capacities obtained at 7 MPa were 1.64 wt% and 1.8 wt% respectively, indicating that both alloys successfully increased their hydrogen storage capacities through high-temperature activation conditions. In terms of hydrogen storage capacity, the results also suggested the possible beneficial effect of blending AB3 and AB5. |
