【作者】 蔡官明；

【导师】 陈长聘；

【作者基本信息】 浙江大学 ， 材料学， 2002， 硕士

【摘要】 研究了由MlNis、MgNi、La-Ca-Mg-Ni和MgaNi等合金与benzene组成的浆料体系的吸氢特性。通过XRD、XPS、SEM和TEM以及P-C-T测试等手段，分析讨论了合金的相结构以及有机溶剂表面处理前后的表面结构等对合金及其组成的浆液吸氢性能的影响。 对MlNi5与C6H6组成的吸氢研究发现，浆液在60℃以下只发生了合金吸氢反应。合金在CgHk中的吸氢反应受传质阻力系数的限制，是一个零级反应过程。热力学计算结果表明，浆液系统和气固系统中合金吸氢反应的△H°、△S°值基本相同，说明合金吸氢热力学性能不受苯液的影响。 经40小时球磨处理后，铸态La1．8Cao．2Mgl6Ni合金转变为非晶态结构，合金颗粒的外形从多棱角状逐渐转变成光滑的圆形。在Lal-sCao．2MglNi合金中添加少量的Mg2Ni粉末混合球磨20h混合物也转变为非晶态结构。混合物颗粒的形态与单独球磨的Lal．sCao．2MglNi合金相比，其外形也发生了一定的变化，但仍有非常明显的棱角。非晶态Lal．sCao．2M81dNi的活化性能急剧下降，在350℃、3.5MPa氢气压了下保温2h，才观察到合金的吸氢反应，而且吸氢速率很低。非晶态合金比常规熔铸的合金的放氢性能有显著提高，在275℃、0.1MPa氢压下，1小时内放出～1.0wt％的氢气，而在相同条件下铸态合金却未能观察到。 Mg-Ni合金和CdH6组成的浆液是一个双相吸氢体系。吸氢过程包含两个阶段，在前一阶段，Mg-Ni合金和苯都发生了吸氢反应，但以合金吸氢为主，后一阶段是苯的加氢过程，其吸氢速度较快。浆液的吸氢速率随温度和浆液中合金浓度升高而加快。研究发现苯主要是在金属氢化物催化下加氢。 在Lal．sCao．2Mgl7-xNi)c、Mg嘶Ni与苯组成的浆液也都发生双相吸氢反应。未经改性处理的Lal．sCao．2Mglv-xNil合金与CdHb组成的浆液吸氢反应前一阶段速率较快而苯的加氢速率低。MgaNi浆液的吸氢速率更小，只有少量的苯发生了加氢反应。经过有机溶剂处理的合金表面有羽毛状细微结构形成。通过XPS分析证实，合金表面存在Mg化合物新相，并且活性Ni原子含量提高。处理后的合金与苯组成的浆液的吸氢速率有急剧的上升，其最佳处理合金组成的浆液在483K、4.5MPa氢压下，3-4分钟内吸氢6.56wt％。更多还原

【Abstract】 The hydrogen storage properties of the slurry systems made by mixing benzene with MINis, Mg-Ni, La-Ca-Mg-Ni and Mg2Ni respectively were investigated. By means of XRD/XPS analyses, SEM investigations, TEM observations and P-C-T measurements, the phase and surface structures of the treated and untreated alloys and the influences to the hydrogen absorption properties produced by organic solvent treatment were studied in detail.It is discovered that only the alloy absorbs hydrogen in the slurry system formed by MlNi5 and benzene below 60"C. The hydrogen absorption rate of the alloy suspended in benzene is only limited by the mass transfer coefficient. The AH?and AS0 of the hydrogen absorption of the alloy in slurry system and gas-solid system are respectively -27.1kJ/molH2, - 83.6J/Kmol and -27.2kJ/molH2, -85.7J/Kmol which confirms that the absorption thermodynamics of the alloy in two systems are similar.After 40h milling, the Lai.gCao.aMgieNi alloy transformed from crystalline to amorphous. The shape of the alloy particles changed sharply. The edges and corners disappeared and the surface became much smoother. The activation properties of the alloy are deteriorated by the mechanical milling treatment but the hydrogen desorption properties of the amorphous alloy is improved. At 275 "C and under O.lMPa H2, the milled Lai.8Cao.2Mg16Ni desorbed ~1.0wt% H2 in Ihr but no hydrogen desorption of cast alloy is observed at the same condition. Some Mg2Ni powders were added into the Lai.gCao^Mg]6Ni alloy and milled together. After 20hr, the composite transformed from crystalline to amorphous, too. The shape of the composite particles changed greatly, but the edges and corners still existed. The incubation period of the milled composite is far shorter than that of the milled Laj.gCao^MgieNi.The slurry formed by benzene and Mg-Ni alloy is a bi-phase hydrogen storage system. There are two portions in the hydriding curves of the slurry formed by Mg-Ni and benzene. The hydriding rate in the former portion is slower than that in the later. The results from the hydrogen absorption measurements of the slurry formed by mixing benzene with Mg-Ni alloy and metal hydride respectively show that the metal hydride is the main catalyst to the hydrogenation of the benzene.Both the alloy and benzene absorb hydrogen in the slurry systems formed by mixing benzene with untreated and treated Lai.8Cao.2Mgi7_xNix and Mg2Ni respectively. When the untreated alloys are used the hydriding rate of the slurry is slow. After organic solvent solution treated, many featheriness microstructures are formed on the surface of Lai gCao^MguNis and Mg2Ni. The XPS analysis resultsshow that some new magnesium compound formed and the content of nickel atoms increased on the top layer. The hydrogen absorption rate of the slurry formed by the treated alloy and benzene increased sharply. In the best treatment condition, the slurry absorbs 6.56wt% hydrogen in 3~4min at 483K and under a hydrogen pressure of 4.5MPa.更多还原