Study of Atomic and Electronic Structures of Nano-Particles in the Early Stages of Their Formation Using Self-Searching Positrons

利用自搜索正电子研究纳米粒子形成早期的原子和电子结构

• 批准号: 13305044
• 负责人: HASEGAWA Masayuki
• 金额: $ 26.96万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 2001
• 资助国家: 日本
• 起止时间: 2001 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13305044/
• 关键词: positron annihilation; precipitated nano particles; Fe-Cu alloys; Al alloys; momentum distribution; Fermi surface; 電子運動量分布; 陽電子消滅法; 自己探索プローブ; 陽電子量子ドット閉じ込め

Embedded (sub-)nano particles in materials play important roles in controlling the physical and mechanical properties of the host materials. Thus it is very indispensable to clarify the evolution processes of the nano particles as well as their atomic and electronic structures. This study aims to establish a novel approach to these issues with use of the latest positron-annihilation experimental and theoretical methods, such as coincidence Doppler broadening (CDB), two-dimensional angular correlation of annihilation radiation (2D-ACAR) and corresponding first-principles calculations.First we have revealed the formation process of Cu (bcc) particles in thermally aged Fe-Cu alloys by detailed aging experiments; the evolution of Cu aggregation in different aging conditions has been investigated by the CDB method. Second we have obtained detailed aging-induced changes in the 2D-ACAR momentum distribution, especially around Fermi cut-off momentum region. Larger smearing around the Fermi momentum is observed for the small Cu particles with sub-nano sizes. This observation strongly suggests a new and unique method for detecting sub-nano size Cu particles in Fe. At this stage we have succeeded to observe the nano particles larger than 0.5 nm.We also have measured 2D-ACAR spectrum of aging-induced particles in the single crystals of Al alloys: Ag_2Al and fcc Zn particles. Combining the first-principles calculations, we obtained detailed Fermi surfaces of the embedded particles.

材料中嵌入的（亚）纳米颗粒在控制主体材料的物理和机械性能方面发挥着重要作用。因此，阐明纳米粒子的演化过程及其原子和电子结构是非常必要的。本研究旨在利用最新的正电子湮灭实验和理论方法，例如符合多普勒展宽（CDB）、湮没辐射的二维角相关（2D-ACAR）和相应的一阶正电子湮灭辐射，建立解决这些问题的新方法。首先我们通过详细的时效实验揭示了热时效Fe-Cu合金中Cu(bcc)颗粒的形成过程；通过CDB方法研究了不同老化条件下Cu聚集的演变。其次，我们获得了详细的老化引起的 2D-ACAR 动量分布变化，特别是在费米截止动量区域周围。对于亚纳米尺寸的小铜颗粒，观察到费米动量周围有较大的拖尾现象。这一观察结果有力地表明了一种新的、独特的方法来检测铁中的亚纳米尺寸铜颗粒。现阶段我们已经成功地观察到了大于0.5 nm的纳米颗粒。我们还测量了铝合金单晶中时效诱导颗粒的2D-ACAR谱：Ag_2Al和fcc Zn颗粒。结合第一性原理计算，我们获得了嵌入粒子的详细费米面。

项目成果

Z.Tang et al.: "First-principle calculation of the coincidence Doppler broadening of positron annihilation radiation"Physical Review B. 65. 045108 (2002)

Z.Tang等：“正电子湮没辐射符合多普勒展宽的第一原理计算”Physical Review B.65.045108(2002)

Y.Nagai et al.: "Coincidence Doppler Broadening Study of the Pre-precipitation Stage of an Al-Cu-Mg-Ag alloy"accepted for publication in Philosophical Magazine A. (印刷中).

Y. Nagai 等人：“Al-Cu-Mg-Ag 合金预沉淀阶段的重合多普勒展宽研究”接受在哲学杂志 A 上发表（正在出版）。

Positron annihilation study of vacancy-solute complex evolution in Fe-based alloys

• DOI: 10.1103/physrevb.67.224202
• 发表时间: 2003-06-11
• 期刊: PHYSICAL REVIEW B
• 影响因子: 3.7
• 作者: Nagai, Y;Takadate, K;Hasegawa, M
• 通讯作者: Hasegawa, M

Elemental analysis of positron affinitive site in materials by coincidence Doppler broadening spectroscopy

• DOI: 10.1016/s0969-806x(03)00188-9
• 发表时间: 2003-10-01
• 期刊: RADIATION PHYSICS AND CHEMISTRY
• 影响因子: 2.9
• 作者: Nagai, Y;Tang, Z;Hasegawa, M
• 通讯作者: Hasegawa, M

T.Onitsuka et al.: "Deformation-Enhanced Cu precipitation in Fe-Cu Alloy Studied by Positron Annihilation Spectroscopy"Physical Review B. 65. 012204 (2002)

T.Onitsuka 等人：“通过正电子湮灭光谱研究的 Fe-Cu 合金中变形增强的 Cu 沉淀”物理评论 B. 65. 012204 (2002)