CoFe0.5-2.5MnTi0.5-2.5VZr與AlMgNi0.3-1.0TiZr 高熵儲氫合金之研究

Hydrogen Storage in CoFe0.5-2.5MnTi0.5-2.5VZr and AlMgNi0.3-1.0TiZr High-Entropy Alloys

林偉恩(Wei-En Lin)

指導教授 ： 陳瑞凱 ； 葉均蔚

國立清華大學/工學院/材料科學工程學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00407

摘要

本研究第一部份以等莫耳CoFeMnTiVZr多元高熵合金為基礎，以Fe與Ti變量 (Fex及Tiy合金) 作元素改質及溫度改變，以探討真空電弧熔煉鑄造態非等莫耳合金CoFexMnTiyVZr (簡稱E6合金) 的吸放氫行為。第二部份以創新的等莫耳含鎂AlMgNiTiZr高熵合金為基礎，以Ni變量作元素改質及溫度改變，探討輕型機械合金化AlMgNiwTiZr高熵合金 (簡稱E5合金) 的吸放氫行為。先以X光繞射儀分析晶體結構，掃描電鏡分析微結構，EDS測定合金組成，DSC量測金屬氫化物的放氫溫度，再以PCI及動力曲線，量測E5及E6合金吸放氫行為。
重要結論如下: 鑄造態E6合金，最大儲氫量約2 wt%，平台壓集中在1 - 5 atm之間，t0.9 (達到最大儲氫量百分之九十所需的時間) 約在100秒以內，遲滯值約在1以內，晶粒大小吸氫前分布在17.1 nm - 50.3 nm，吸氫後分布在14.8 nm - 46.1 nm，體積膨脹率約在3 %以內，晶體結構主要為C14 Laves相，元素過度添加，皆有元素態析出，熱力學分析顯示，E6合金分布趨勢與AB2型合金相似。機械合金化E5合金，球磨八小時即已合金化，各元素分布均勻，最大儲氫量約1.5 wt%，動力學達飽和儲氫量時間較長、t0.9約10,000秒，平台壓分布於5 - 12 atm之間，晶體結構由數種介金屬化合物所構成，球磨時間越長以及Ni含量減少，越容易發生非晶結構，因此Ni在E5合金內為非晶化抑制元素。

關鍵字

儲氫高熵合金 ； CoFexMnTiyVZr & AlMgNiwTiZr ； 非晶化抑制元素 ； PCI ； C14 Laves相 ； 介金屬化合物

並列摘要

The first part of this study investigates behavior of hydrogen absorption and desorption of non-equal-molar vacuum-arc-remelted as-cast CoFexMnTiyVZr (E6 alloys) based on their equal-molar counterpart by varying x (Fex alloys) and y (Tiy alloys) contents as well as measuring temperature. The second part does the same things as the first part but only changing the alloys to mechanical-alloying (MA) light-weighted AlMgNiwTiZr (E5 alloys). Experiments include XRD, SEM, EDS, DSC, PCI, and kinetics of hydrogen absorption and desorption for determination of crystal structure, microstructure, phase composition, hydrogen desorption temperature, and behavior of hydrogen absorption and desorption of E6 and E5 alloys, respectively.
Primary conclusions are summarized as follows: The as-cast E6 alloys possess maximal hydrogen storage capacity of 2 wt %, plateau pressure in PCIs of 1 – 5 atm, time to 90 % of maximal capacity, t0.9, of about 100 s, values of hysteresis of less than 1, grain size before and after hydrogen absorption cycle of 17.1 nm - 50.3 nm, and 14.8 nm - 46.1 nm, respectively, volume expansion mostly of less than 3 %, crystal structure of C14 Laves phase for both before and after cycle states, elemental precipitation for excessive addition of Fe and Ti, and similar distribution as the AB2 alloys in the thermodynamic ΔH vs. (H/M)max plot. MA-E5 alloys have become alloys after 8-h MA with homogeneous distribution of composition, and possess maximal hydrogen storage capacity of 1.5 wt %, plateau pressure in PCIs of 5 – 12 atm, t0.9 of about 10,000 s, crystal structure composed of several intermetallics, property of easy amorphization for prolonged MA and for alloys containing less amount of Ni. Therefore Ni is an amorphization inhibitor in E5 alloys.

並列關鍵字

Hydrogen-storage high-entropy alloys ； CoFexMnTiyVZr & ； amorphization inhibitor ； PCI ； C14 Laves phase ； Intermetallics

參考文獻

3.Anders Andreasen, PhD thesis, 2005

4.Momirlan M, Veziroglu TN. Renewable Sustainable Energy Rev., 6 (2002) 141

6.A. Zuttel, L. Schlapbach, Nature, 414 (2001) 353

8.W. Grochala, P. P. Edwards, Chem. Rev., 104 (2004) 1283

9.a) F. SchMth, B. Bogdanovic, M. Felderhof, Chem. Commun. 2004, 37, p. 2249–2258; b) S. Orimo, Y. Nakamori, J. R. Eliseo, A. Zuttel, C. M. Jensen, Chem. Rev., 107 (2007) 4111