Phase transition and hydrogenation properties of Ce2Ni7-type Pr2Co7 during hydrogen absorption process
Phase transition and hydrogenation properties of Ce2Ni7-type Pr2Co7 during hydrogen absorption process
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Ce2Ni7型Pr2Co7吸氢过程中的相变及加氢性能
DOI：
10.1016/j.ijhydene.2018.04.197
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
and Tetsuya Suzuki
中科院分区：
文献类型：
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作者：
Kenji Iwase;Kazuhiro Mori;Suguru Tashiro;and Tetsuya Suzuki
采用X射线衍射（XRD）和压力-组成（P单键C）等温线研究了Ce 2Ni 7型Pr 2Co 7的晶体结构和加氢性能。可逆吸氢容量达到0.8H/M，在吸附-脱附过程中存在两个平台。两个观察到的氢化物相，Pr2Co7H2.7和Pr2Co7H7.2，被确定为具有六方（空间群：P63/mmc）和正交（空间群：PbCN）晶体结构，分别。合金的晶体结构由六方Ce 2Ni 7型结构（原始合金）→相同的Ce 2Ni 7型结构（Pr2Co7H2.7）→正交（Pr2Co7H7.2）。Pr_2Co_7H_2.7的晶格沿原合金的轴向沿着各向异性膨胀，而Pr_2Co_7H_7.2的晶格沿原合金的轴向各向同性膨胀。基于XRD数据评估了在吸-脱氢过程中原始合金相和氢化物相的半高宽（FWHM）值。在吸收过程中，主峰的FWHM值随着氢含量的增加而降低，表明氢化后晶格缺陷的数量没有增加。第二次循环吸收过程中的平台压力与第一次循环相同，这也表明没有晶格缺陷。
The crystal structure and hydrogenation properties of Pr2Co7with a Ce2Ni7-type structure were investigated by X-ray diffraction (XRD) and observation of the pressure–composition (Psingle bondC) isotherms. The reversible hydrogen capacity reached 0.8 H/M, and two plateaus were observed in the absorption–desorption process. The two observed hydride phases, Pr2Co7H2.7and Pr2Co7H7.2, were determined to have hexagonal (space group:P63/mmc) and orthorhombic (space group:Pbcn) crystal structures, respectively. The crystal structure transformed in the order of hexagonal with a Ce2Ni7-type structure (original alloy) → same Ce2Ni7-type structure (Pr2Co7H2.7) → orthorhombic (Pr2Co7H7.2). The crystal lattice of the Pr2Co7H2.7underwent anisotropic expansion along thec-axis of the original alloy, whereas that of Pr2Co7H7.2exhibited isotropic expansion. The full width at half maximum (FWHM) values for the original alloy and hydride phases during the hydrogen absorption–desorption process were evaluated based on the XRD data. The FWHM values for the main peaks decreased as the hydrogen content increased during the absorption process, indicating that the number of lattice defects did not increase upon hydrogenation. The plateau pressures during the absorption process of the second cycle were the same as those of the first cycle, which also suggests that there were no lattice defects.