Nanocrystalline Al-Mg Alloys for Hydrogen Storage

技术：在运输车辆中储存和使用氢气所涉及的危险导致了用于储氢的金属氢化物的研究。氢化物需要具有高的重量和体积存储能力，在相对较低的温度下快速的加氢/脱氢动力学和在环境条件下稳定的结构。近年来的研究表明，丙酸镁（Mg(AlH4)2）具有最佳的储存能力和脱氢性能，并且在环境条件下相对稳定。但其加氢特性尚不清楚。预计有几个因素可以提高氢化动力学，包括将晶粒尺寸减小到纳米级，增加表面积和加入催化剂。另一方面，合成过程中的污染是阻碍氢吸收的主要问题。在本项目中，将开发一种新的合成技术，以生产具有控制成分和高纯度的Al-Mg合金纳米晶多孔粉末。阐明这些合金中氢化物形成的基本过程，以调整其组成和纳米结构以优化储氢特性。电沉积技术将用于制备含镁量在25 ~ 60wt%范围内的纳米晶Al-Mg合金。将研究亚稳沉积合金的热稳定性和相演化，并对选定的微观结构进行氢化特征测试。基于纳米尺度结构的详细表征和加氢数据的分析，将对合金成分和结构对氢吸收动力学的影响机制有一个深入的了解。如有必要，将加入石墨和钯等催化剂以提高加氢动力学。对优化后的加氢性能合金的氢脱附特性进行了研究。本研究结果将提供一种新的合成技术，并阐明加氢/脱氢过程的机理。非技术：能源消耗的快速增长，化石燃料的急剧减少，以及对高效清洁燃料替代品的需求，导致了燃料电池的深入研究和发展，而燃料电池需要氢作为燃料。这是佛罗里达大学材料科学与工程系和中佛罗里达大学佛罗里达太阳能中心之间的合作项目。这项工作将通过在同行评估的期刊上发表和在国家和国际会议、大学、国家实验室等上发表的结果传播，影响科学界。这些研究的结果将有助于开发一种潜在的储氢材料，这将对燃料电池驱动汽车的发展产生重大影响。这项研究的技术影响将是重要的，因为电沉积是一个成熟的行业，技术转让将非常容易。该计划的教育部分包括对大一和高年级的研究生和本科生的培训。由于材料科学与工程在高中和初中学生中不是很熟悉，因此将努力通过参加MSE-teach研讨会和邀请高中生参加实验室来教育教师。通过为留学生提供实习机会，促进国际化教育。

TECHNICAL: The hazards involved in storing and using hydrogen gas in transportation vehicles has led to the investigation of metal hydrides for hydrogen storage. The hydrides are required to have high gravimetric and volumetric storage capacities, fast hydrogenation/dehydrogenation kinetics at relatively low temperatures and stable structures in ambient conditions. Recently it has been shown that magnesium alanate, Mg(AlH4)2, has the best combination of storage capacity and dehydrogenation properties and is relatively stable under ambient conditions. However, its hydrogenation characteristics are not known. Several factors are expected to enhance the hydrogenation kinetics including reducing grain size to nano-regime, increasing the surface area and incorporating catalysts. On the other hand contamination during synthesis is a major issue that impedes the hydrogen uptake. In this program, a new synthesis technique will be developed that will produce nanocrystalline porous powders of Al-Mg alloys with controlled composition and high purity. Fundamental process of hydride formation in these alloys will be elucidated with the objective of tailoring the composition and nanostructure for optimized hydrogen storage characteristics. Electrodeposition techniques will be employed for fabricating the nanocrystalline Al-Mg alloys within 25 to 60wt% Mg composition range. Thermal stability and the phase evolution of the metastable as-deposited alloys will be investigated and selected microstructures will be tested for hydrogenation characteristics. Based on the detailed characterization of the structure at nanoscale and analysis of the hydrogenation data, a mechanistic understanding of the effects of alloy composition and structure on the hydrogen uptake kinetics will be developed. Catalysts such as graphite and Pd will be incorporated to enhance the hydrogenation kinetics, if necessary. The alloys with optimized hydrogenation properties will be investigated for their hydrogen desorption characteristics. The results of this research will provide a new technique for synthesis and shed light on the mechanisms of hydrogenation/dehydrogenation processes. NON-TECHNICAL: The fast increase in energy consumption, the drastic decrease in fossil fuels, and the demand for an efficient and clean fuel alternative have resulted to the intensive research and development of fuel cells, which require hydrogen as fuel. This is a collaborative program between the Materials Science and Engineering Department at the University of Florida and the Florida Solar Energy Center at the University of Central Florida. This work will impact the scientific community through the dissemination of the results by publishing in peer-assessed journals and presentation at national and international conferences, universities, national labs, etc. Results from these studies will help to develop a potential material for hydrogen storage which will have significant impact on the development of fuel cell driven cars. The technological impact of this research will be important because electrodeposition is a well-established industry and the transfer of technology will be very easy. The educational component of this program includes training of graduate and undergraduate students at freshman as well senior level. Since Materials Science and Engineering is not well known among the high school and middle school students, efforts will be placed on educating the teachers through participation in the MSE-teach workshop and hosting high school students in labs. Education at an international level will be promoted by providing internship for international students.