非等莫耳六元CoFeMnTiVxZry (0.4 ≤ x, y ≤ 3)高熵合金之儲氫研究

Hydrogen Storage in CoFeMnTiVxZry (0.4 ≤ x, y ≤ 3) High-Entropy Alloys

許臻豪(HASH(0x1c227850))

指導教授 ： 陳瑞凱 ； 林樹均

國立清華大學/工學院/材料科學工程學系/碩士(2008年)

摘要

儲氫合金的儲氫量、工作壓力、工作溫度、循環壽命與吸放氫速率都是目前儲氫合金發展過程中所被重視的環節。本研究以真空電弧熔煉製備合金，所用合金均為鑄造態，輔以X光繞射術(XRD)與掃描式電子顯微鏡術(SEM)分析，並以X光能譜分析術(EDS)測定合金成份微結構組成，再利用壓力成分等溫(PCI)曲線，量測合金吸放氫行為。本研究以等莫耳高熵合金為基礎，添加或置換元素，並利用本研究提出的熱力學平均分配法，詳細探討非等莫耳合金的儲氫特性。對Laves相CoFeMnTiVxZry (0.4 ≦ x, y ≦ 3)高熵儲氫合金的初步研究顯示，含Zr成分的合金均可以活化並吸氫，且增加V與Zr含量可以有較大的吸氫量。本研究並提出平均分配法簡化結合焓的計算，得到在同一系統中，合金中每莫耳原子計算結合焓與最大莫耳比儲氫量呈線性關係。在不同系統中，總能量是決定最大莫耳比儲氫量的重要因素。

關鍵字

等莫耳與非等莫耳高熵合金 ； 壓力成分等溫曲線 ； Laves相 ； CoFeMnTiVxZry ； 平均分配法計算結合焓

並列摘要

Storage capacity, working pressure and temperature, cycle life, and rate of absorption and desorption in hydrogen storage are current emphasized developing issues. We use a vacuum arc remelter to prepare as-cast alloys. The alloys are characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), and x-ray diffractometry (XRD). Pressure-composition-isotherm (PCI) curves are used to investigate the absorption and desorption of hydrogen. After detailed investigation we conclude that both equal- and non-equal-molar high-entropy alloys have a high potentiality in hydrogen storage.
Results on Laves phase-related CoFeMnTiVxZry (0.4 ≦ x, y ≦ 3) high-entropy alloys shows that with Zr as a component, high-entropy alloys are easily activated and absorb hydrogen. Simultaneous addition of Zr and V improves the capacity of hydrogen absorption. In this experiment, we first adopt the most popularly used equal-molar compositions in high-entropy alloys as a base to find a suitable alloy series, then change the relative amount among components in alloys or make substitution for elements to investigate in detail the effects of elements and non-equal molar compositions on the hydrogen storage properties.
An equipartition method (EPM) for calculation formation enthalpy of multicomponent metal hydrides proposed in this study shows a linear relationship between enthalpy per mole atom in alloy and maximum storage capacity in atomic ratio for a single system. On the other hand, for different systems total energy determines the maximum storage capacity among systems.

並列關鍵字

equal- and non-equal-molar high-entropy alloys ； PCI curves ； Laves phase ； CoFeMnTiVxZry ； equipartition method for formation enthalpy calculation

參考文獻

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