金属氮氢化物复合材料储氢循环性能研究

发布时间：2018-04-19 15:00

本文选题：储氢材料 + LiMgBNH　；参考：《北京有色金属研究总院》2015年硕士论文

【摘要】：Li-Mg-N-H复合储氢材料具有较大的储氢容量和良好的可逆性,成为最有希望的实用储氢材料之一,但缓慢的吸放氢动力学限制了其广泛应用。添加LiBH4后,材料动力学性能得到一定改善,但放氢温度仍然较高,且循环性能较差。催化和复合可有效提高LiMgBNH (1.1 MgH2-2LiNH2-0.1 LiBH4)储氢材料的动力学和热力学性能。本文首先研究了三种不同AB5型合金(LaNi3.8Al0.75Mn0.45、LaNi4Co、LaNi4.5Mn0.5)对LiMgBNH储氢材料吸放氢动力学性能的影响。三种合金均可有效改善LiMgBNH材料的放氢动力学,降低放氢温度和放氢反应激活能,其中对动力学性能改善最显著的是LaNi4.5Mn0.5合金。AB5型合金并未与LiMgBN H生成新相,合金产生催化作用的原因可能是合金的添加使LiMgBNH中N-H键的键能减小,有利于材料放氢,弥散分布的合金颗粒使合金的催化作用得以充分发挥。通过比较不同制备工艺对复合材料放氢动力学及循环性能的影响,发现高球料比制备的10wt.% LaNi45Mn0.5样品虽然具有较好的动力学性能,但因合金及基体材料颗粒较细,在吸放氢循环过程中容易聚集长大,150℃下循环性能较差,其平均放氢衰减量约为LiMgBNH样品的2倍。而低球料比制备的10 wt.% LaNi4.5Mn0.5样品合金颗粒尺寸增大,循环性能较LiMgBNH样品有明显改善。循环过程中颗粒的聚集长大增大了扩散传质的距离,引起动力学衰减,从而造成容量衰减。降低球料比后,样品中颗粒较大的LaN45Mn0.5合金具有一定的分散强化催化作用,即合金在循环过程中发生开裂粉化,一方面改善了颗粒的聚集情况,另一方面增大了合金的分散程度,使合金的催化性能发挥更充分,这可部分抵消因颗粒长大造成的动力学衰减,从而提高材料循环稳定性。本文研究了温度对复合材料吸放氢性能的影响,发现温度降低时,由于原子扩散减缓,复合材料动力学性能衰减明显。降低循环温度至140℃,低球料比制备的10wt.%LaNi4.5Mn0.5样品循环性能没有因颗粒长大减缓而改善。吸放氢不充分仍是其循环放氢衰减的一个重要原因。LaNi4.5Mn0.5合金可有效改善复合材料的颗粒聚集情况,但较小的添加量使其改善作用有限。将复合材料中LaNi4.5Mn0.5含量提高至30wt.%,材料的动力学性能提高,颗粒聚集情况明显改善。但材料颗粒长大明显,其150℃下循环性能与LiMgBNH样品及10wt.% LaNi4.5Mn0.5样品相比变差。原因是球磨过程中合金对基体材料有研磨作用,使基体材料颗粒变细,循环过程中更易长大。为进一步研究增大添加量后合金对复合材料循环性能的影响,将循环温度提高至180℃。LiMgBNH样品循环性能变差,而30wt.% LaNi4.5Mn0.5样品循环性能相对于未添加样有了明显的改善。由于循环温度升高,循环过程中颗粒快速长大,合金的分散强化催化作用变得明显,因此添加合金的复合材料循环性能明显改善。为降低合金对基体材料颗粒的研磨作用,采用三维摆动混合方法制备了30 wt.% LaNi4.5Mn0.5样品,由于合金分散度下降,其动力学性能较球磨样下降。因基体材料颗粒大小对复合材料循环性能的影响较大,150℃下该混合样品循环性能相对于球磨的30wt.%LaNi4.5Mn0.5样品有了明显提升。合金的添加也使混合样品的循环性能优于LiMgBNH样品。
[Abstract]:Li-Mg-N-H composite hydrogen storage materials have large hydrogen storage capacity and good reversibility, and become one of the most promising practical hydrogen storage materials. However, the slow desorption kinetics limit its wide application. After adding LiBH4, the dynamic properties of materials are improved, but the hydrogen storage temperature is still high, and the cycle performance is poor. Catalysis and complex. The kinetic and thermodynamic properties of LiMgBNH (1.1 MgH2-2LiNH2-0.1 LiBH4) hydrogen storage materials can be effectively improved. In this paper, the effects of three different AB5 alloys (LaNi3.8Al0.75Mn0.45, LaNi4Co, LaNi4.5Mn0.5) on the absorption and desorption kinetics of LiMgBNH hydrogen storage materials are investigated. The hydrogen release kinetics of LiMgBNH materials can be effectively improved by three kinds of alloys. The most significant improvement of the kinetic properties is that the LaNi4.5Mn0.5 alloy.AB5 alloy does not produce a new phase with LiMgBN H. The reason for the catalytic effect of the alloy may be that the alloy addition makes the bond energy of the N-H bond in LiMgBNH decrease, which is favorable for the material to degenerate and the dispersed alloy particles make the alloy. By comparing the effects of different preparation processes on the kinetics of hydrogen release and the performance of the composites, it is found that the high ball material has better kinetic properties than the 10wt.% LaNi45Mn0.5 sample prepared, but it is easy to gather and grow at 150 degrees in the process of hydrogen absorption and desorption because of the fine particles of the alloy and the matrix material. The lower cycle performance is poor, and the average dehydrogenation reduction is about 2 times that of the LiMgBNH sample. The size of the low ball material is larger than that of the 10 wt.% LaNi4.5Mn0.5 sample, and the cycle performance is obviously better than that of the LiMgBNH sample. The aggregation and growth of the particles increases the distance of the diffusion mass transfer and causes the kinetic attenuation, resulting in the capacity of the sample. Attenuation. After reducing the ball ratio, the larger LaN45Mn0.5 alloy in the sample has a certain dispersion strengthening catalysis, that is, the alloy has cracked powder during the cycle process. On the one hand, the aggregation of the particles is improved. On the other hand, the dispersing degree of the alloy is increased and the catalytic performance of the alloy is more fully played, which partly counteracts the due to the grain. The effect of temperature on the performance of hydrogen absorption and desorption is studied. The effect of temperature on the performance of hydrogen absorption and desorption is studied. It is found that when the temperature is reduced, the dynamic properties of the composites are attenuated because of the reduction of atomic diffusion. The circulation of 10wt.%LaNi4.5Mn0.5 samples prepared by low ball material is reduced to 140 degrees C. .LaNi4.5Mn0.5 alloy can effectively improve the particle aggregation of the composite material, but the small amount of addition makes it limited. The content of LaNi4.5Mn0.5 in the composite is increased to 30wt.%, and the dynamic properties of the material are raised. The agglomeration of particles is obviously improved, but the growth of the material particles is obvious, and the cycling performance at 150 C is worse than that of the LiMgBNH samples and the 10wt.% LaNi4.5Mn0.5 samples. The reason is that the alloy has a grinding effect on the matrix material in the ball milling process, making the matrix material finer and more easy to grow in the cycle process. The effect of alloy on the cyclic properties of the composites is that the cycling performance of the samples is worse than that of the samples at 180.LiMgBNH, while the cyclic properties of 30wt.% LaNi4.5Mn0.5 samples are obviously improved compared to the non addition samples. The particles grow rapidly in the cycle process and the dispersion strengthening catalysis of the alloy becomes obvious because of the increase of the cycle temperature. In order to reduce the grinding effect of the alloy to the matrix material, the 30 wt.% LaNi4.5Mn0.5 samples were prepared by the three dimensional swinging mixing method. The kinetic properties of the composites decreased because of the decrease of the dispersion of the alloy. The influence of the particle size of the matrix material on the cyclic properties of the composites was observed. The cyclic performance of the mixed sample is obviously improved at 150 C at 150 C. The addition of the alloy also makes the cycling performance of the mixed sample better than that of the LiMgBNH sample.

【学位授予单位】：北京有色金属研究总院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB34

【共引文献】