【摘要】：本文在論述儲氫化合物研究進展及存在問題的基礎上,利用Retiveld全譜擬合分析、X射線衍射分析(XRD)、壓力組成等溫線(P-C-T)測試、透射電子顯微鏡(TEM)等手段系統(tǒng)研究了Mg含量對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)三類化合物結構和吸放氫特性的影響,揭示了三類化合物結構特征與吸放氫特性之間的關系,并進行了對比,主要結論如下:(1)通過將SmNi、SmNi_5、SmNi_2前驅體,與一定比例Mg、Ni粉球磨加燒結退火后成功制備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)型相分別是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。擬合結果表明,Mg原子僅僅占據在這些主相結構中[A_2B_4]亞單元的A側位置而不占據在[AB_5]亞單元。同時同一構型的AB_y型相的晶格參數(shù)和亞單元尺寸隨著Mg含量的增加逐漸減小;并且隨著y值的增大,減小程度越不明顯。(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、未活化和最高氫壓6 MPa條件下的初次P-C-T測試結果表明,隨著Mg含量的增加,同一構型的AB_y型相的吸氫平臺壓變高,吸放氫可逆程度變好,且在同一x值的條件下,隨著y的增加,吸放氫可逆程度也變好;對于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,在當前實驗條件下,均只具有一個吸(放)氫平臺;而Sm_(4-x)Mg_(x )Ni_(14)(x=0.25,0.5,0.75)化合物,均呈現(xiàn)出兩個吸放氫平臺。(3)對初次P-C-T后的產物進行分析結果表明,SmNi_2、Sm_(1.75)Mg_(0.25)Ni_4化合物完全非晶化,主要生成非晶氫化物;Sm_(1.5)Mg_(0.5)Ni_4化合物則發(fā)生了部分非晶化和氫致微相分離(HIMPS),生成了Sm_(1.5-x )Mg_(0.5+x )Ni_4H_y相、非晶氫化物和富Ni相;SmNi_3化合物部分發(fā)生了結構改變,生成了SmNi_3H_x化合物;而其余成分的Sm-Mg-Ni化合物則仍由原來的相結構組成。(4)沒有發(fā)生非晶化、HIMPS和結構轉變的化合物經過吸放氫循環(huán)測試結果表明,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次吸放氫循環(huán)后的儲氫容量保持率分別為98%、97%、92%、87%、71%、66%、44%、44%。這一變化趨勢主要歸因于Mg原子的擇優(yōu)占位和相結構中[AB_5]亞單元比例的增加,二者均可以通過降低相在吸放氫過程中的點陣應變來提高吸放氫循環(huán)穩(wěn)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緇撹濡備笅:(1)閫氳繃灝哠mNi,SmNi_5,SmNi_2鍓嶉┍浣，

本文編號：2281924