Mg含量对Sm-Mg-Ni化合物吸放氢特性的影响
发布时间：2018-10-19 18:03
【摘要】：本文在论述储氢化合物研究进展及存在问题的基础上,利用Retiveld全谱拟合分析、X射线衍射分析(XRD)、压力组成等温线(P-C-T)测试、透射电子显微镜(TEM)等手段系统研究了Mg含量对AB_y(y=2,3,3.5)型Sm_(2-x )Mg_(x )Ni_4、Sm_(3-x )Mg_(x )Ni_9、Sm_(4-x)Mg_(x )Ni_(14)(x=0,0.25,0.5,0.75)三类化合物结构和吸放氢特性的影响,揭示了三类化合物结构特征与吸放氢特性之间的关系,并进行了对比,主要结论如下:(1)通过将SmNi、SmNi_5、SmNi_2前驱体,与一定比例Mg、Ni粉球磨加烧结退火后成功制备Sm_(2-x )Mg_(x )Ni_4、Sm_(3-x )Mg_(x )Ni_9、Sm_(4-x )Mg_(x )Ni_(14)(x=0.25,0.5,0.75)多相化合物,其中AB_2型、AB_3型和AB_(3.5)型相分别是Sm_(2-x )Mg_(x )Ni_4、Sm_(3-x )Mg_(x )Ni_9、Sm_(4-x )Mg_(x )Ni_(14)化合物中的主相。拟合结果表明,Mg原子仅仅占据在这些主相结构中[A_2B_4]亚单元的A侧位置而不占据在[AB_5]亚单元。同时同一构型的AB_y型相的晶格参数和亚单元尺寸随着Mg含量的增加逐渐减小;并且随着y值的增大,减小程度越不明显。(2)Sm_(2-x )Mg_(x )Ni_4、Sm_(3-x )Mg_(x )Ni_9、Sm_(4-x )Mg_(x )Ni_(14)(x=0,0.25,0.5,0.75)化合物在298 K、未活化和最高氢压6 MPa条件下的初次P-C-T测试结果表明,随着Mg含量的增加,同一构型的AB_y型相的吸氢平台压变高,吸放氢可逆程度变好,且在同一x值的条件下,随着y的增加,吸放氢可逆程度也变好;对于Sm_(2-x )Mg_(x )Ni_4、Sm_(3-x )Mg_(x )Ni_9(AB_3型相)和Sm_2Ni_7化合物,在当前实验条件下,均只具有一个吸(放)氢平台;而Sm_(4-x)Mg_(x )Ni_(14)(x=0.25,0.5,0.75)化合物,均呈现出两个吸放氢平台。(3)对初次P-C-T后的产物进行分析结果表明,SmNi_2、Sm_(1.75)Mg_(0.25)Ni_4化合物完全非晶化,主要生成非晶氢化物;Sm_(1.5)Mg_(0.5)Ni_4化合物则发生了部分非晶化和氢致微相分离(HIMPS),生成了Sm_(1.5-x )Mg_(0.5+x )Ni_4H_y相、非晶氢化物和富Ni相;SmNi_3化合物部分发生了结构改变,生成了SmNi_3H_x化合物;而其余成分的Sm-Mg-Ni化合物则仍由原来的相结构组成。(4)没有发生非晶化、HIMPS和结构转变的化合物经过吸放氢循环测试结果表明,Sm_(3.25)Mg_(0.75)Ni_(14)、Sm_(3.5)Mg_(0.5)Ni_(14)、Sm_(3.75)Mg_(0.25)Ni_(14)、Sm_(2.25)Mg_(0.75)Ni_9、Sm_(2.5)Mg_(0.5)Ni_9、Sm_(2.75)Mg_(0.25)Ni_9、Sm_2Ni_7、Sm_(1.25)Mg_(0.75)Ni_4化合物在50次吸放氢循环后的储氢容量保持率分别为98%、97%、92%、87%、71%、66%、44%、44%。这一变化趋势主要归因于Mg原子的择优占位和相结构中[AB_5]亚单元比例的增加,二者均可以通过降低相在吸放氢过程中的点阵应变来提高吸放氢循环稳定性。
[Abstract]:In this paper, on the basis of discussing the research progress and existing problems of hydrogen storage compounds, (XRD), pressure composition isotherm (P-C-T) measurement is analyzed by Retiveld full-spectrum fitting analysis and X-ray diffraction analysis. The effects of Mg content on the structure and desorption properties of AB_y (2-x) Mg_ (x) Ni_4,Sm_ (3-x) Mg_ (x) Ni_9,Sm_ (4-x) Mg_ (x) Ni_ (14) (xantho-0.250.50.75) have been systematically studied by means of transmission electron microscopy (TEM). The relationships between the structural characteristics and desorption properties of three kinds of compounds have been revealed and compared. 涓昏缁撹濡備笅:(1)閫氳繃灏哠mNi,SmNi_5,SmNi_2鍓嶉┍浣，
本文编号：2281924
[Abstract]:In this paper, on the basis of discussing the research progress and existing problems of hydrogen storage compounds, (XRD), pressure composition isotherm (P-C-T) measurement is analyzed by Retiveld full-spectrum fitting analysis and X-ray diffraction analysis. The effects of Mg content on the structure and desorption properties of AB_y (2-x) Mg_ (x) Ni_4,Sm_ (3-x) Mg_ (x) Ni_9,Sm_ (4-x) Mg_ (x) Ni_ (14) (xantho-0.250.50.75) have been systematically studied by means of transmission electron microscopy (TEM). The relationships between the structural characteristics and desorption properties of three kinds of compounds have been revealed and compared. 涓昏缁撹濡備笅:(1)閫氳繃灏哠mNi,SmNi_5,SmNi_2鍓嶉┍浣，
本文编号：2281924
本文链接：https://www.wllwen.com/kejilunwen/jiagonggongyi/2281924.html
