利用中子衍射和XRD技术, 结合Reitveld拟合和Fourier变换, 对Laves相零基体合金Ti0.68Zr0.32MnCr的氘化物中氘的占位特征进行了研究. 氘化物Ti0.68Zr0.32MnCrD3.0的中子衍射谱除Bragg衍射峰外, 还出现明显的漫散射包, 而相应的XRD谱却只呈现衍射峰, 未发现漫散射包. 对衍射谱与相应的RDF分析表明, 这种C14型Laves相氘化物中只有部分氘原子随机不饱和地分布在确定的4种A2B2四面体间隙位置, 并形成长程有序结构, 这部分氘原子在6h1和12k位的占位系数比6h2和24l位大. 而氘化物中的另一部分氘原子并不是随机分布, 而是不同程度地偏离间隙中心的位置, 形成比长程有序结构更大的氘原子间距的短程有序结构. 短程与长程有序的氘原子共同形成沿着合金六方晶格的c轴在Ti/Zr原子周围的四面体间隙聚集的网格团簇结构. 这种偏离有序位置的团簇结构是大量氘原子在晶格间隙中聚集所造成的.
The occurrences of diffuse scattering in the neutron diffraction patterns of the deuterides of Laves phase have frequently been reported, but have not been specifically studied. As the diffuse scattering indicates the formation of short range ordering of D and/or alloy atoms in the phase, we have particularly studied the possible short range ordering of interstitial D atoms in the deuteride of a null matrix Laves phase alloy Ti0.68Zr0.32MnCr by neutron and XRD techniques. The neutron diffraction pattern of the deuteride Ti0.68Zr0.32MnCrD3.0 has shown not only the Bragg peaks, but also strong diffuse scattering, whereas the corresponding XRD pattern has only shown the Bragg peaks. These phenomena confirm the formation of short range ordering of interstitial D in the deuteride. The D occupancy and short range ordering of the deuteride were analyzed by the Rietveld refinement and Fourier transformation. The analyses suggest that a fraction of D atoms in the deuteride is randomly and unsaturatedly distributed in certain interstices, and forms a long range ordered structure in the crystal lattice. These interstitial atoms are in four types of the A2B2 tetrahedral sites, where the occupancies of the D atoms in the 6h1 and 12k crystallographic sites are higher than those in the 6h2 and 24l sites. However, other D atoms in the deuteride have stayed away from the centres of the interstitial sites to different extents, and formed the short range ordered structure. These D atoms keep an average interdistance of 0.243 nm for the nearest neighbours, larger than that of about 0.2 nm for the long range ordered D atoms. The short and long range ordered D atoms together form a cluster network surround the Ti/Zr atoms along the c--axis of the lattice. The phenomenon is likely to be caused by the accumulation of great amount of D atoms in the interstices of the alloy.
参考文献
| [1] | |
| [2] | |
| [3] | |
| [4] | |
| [5] | |
| [6] | |
| [7] | |
| [8] | |
| [9] | |
| [10] | |
| [11] | |
| [12] | |
| [13] | |
| [14] | |
| [15] | |
| [16] | |
| [17] | |
| [18] | |
| [19] | |
| [20] | |
| [21] |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%