成果報告書詳細
管理番号20100000001968
タイトル*平成21年度中間年報 水素製造・輸送・貯蔵システム等技術開発 水素貯蔵材料 貯蔵・輸送機器要素技術に関する研究開発 ホウ素系水素貯蔵材料の開発
公開日2011/5/10
報告書年度2009 - 2009
委託先名株式会社豊田中央研究所 国立大学法人東北大学金属材料研究所
プロジェクト番号P08003
部署名燃料電池・水素技術開発部
和文要約和文要約等以下本編抜粋:1.研究開発の内容及び成果等 1.複合化によるホウ素系水素化物開発 (1.1)Mg(BH4)2+Mg(NH2)2 Mg(BH4)2+Mg(NH2)2の複合材料は10mass%程度の水素放出能力を有する。本実験では水素放出機構を解明するためにin-situ XRD測定を実施した。図1-1は加熱時のXRDプロファイルを示す。加熱によってMg(BH4)2+Mg(NH2)2→結晶相1→結晶相2(2Mg(BH4)(NH2))→非晶質相の過程を経て水素を放出する。
英文要約Development of advanced hydrogen storage materials with high hydrogen density and moderate operation temperature is widely regarded as one of the key technologies for the widespread of hydrogen energy. Metal borohydride M(BH4)n (M: metal, n = 1-4) with high hydrogen density (up to 18 mass%) has been attracting great attention as one of the potential hydrogen storage materials. However, the high dehydriding/rehydriding temperature and low reaction rate are big barriers for onboard hydrogen storage application. In this year, our studies mainly focused on the following aspects; 1) Composite hydrides, 2) Intermediate compounds, 3) Additives effects, and 4) Muon spin relaxation (μSR) analysis. The achievements acquired in this year are shown below.
1) Composite hydrides. Dehydriding process of Mg(BH4)2+Mg(NH2)2 system with a potentiality to release approximately 10mass% of hydrogen was investigated. The crystal structure of a new phase formed at an elevated temperature was determined by combining XRD analysis and theoretical calculations. For LiBH4+2LiNH2 system, it has been found that approximately 9mass% of hydrogen can be released at 150℃. Also, we have confirmed that the rehydriding reaction partially proceeded after a high pressure rehydriding treatment. In addition, the initial dehydriding temperature was decreased to below 150℃ in the Ca(BH4)2+LiAlH4 system. Therefore, the above experimental results indicate that appropriate composite hydrides are very important for lowering dehydriding temperature.
2) Intermediate compounds: On the way to the clarification of the dehydriding process of Ca(BH4)2, we found the structural transformation and determined the crystal structures of low- and high-temperature Ca(BH4)2. Furthermore, we investigated the rehydriding property of Mg(BH4)2 and found the re-formation of Mg(BH4)2 and the intermediate compound MgB12H12. These results suggest that Mg(BH4)2 has the possibility for reversible hydrogen storage, while further improvements of hydrogen storage properties are required for practical applications.
3) Additives effects: In order to improve the dehydriding/rehydriding properties of Mg(BH4)2, we have systematically investigated the Ti-based additives effect. It was found that TiCl3 showed the best improvement effects on both dehydriding and rehydriding reactions among the Ti-based additives. The improvement effects might attribute to the catalytic effect of TiB2 formed during heating process and the suppression of the segregation of MgH2 from primary material.
4) μSR analysis: μSR analysis of a series M(BH4)n have been successfully carried out. We have found a good correlation between the dehydriding properties and the formation probability of H-μ+-H. This means the formation probability of H-μ+-H would be a good indicator for estimating the thermodynamic stabilities of M(BH4)n.
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