Chemical Analysis and Electronic Structure Studies of Vacancy-Type Defects by Measuring Positron Annihilation Momentum Distribution in Wide Range

通过测量大范围正电子湮没动量分布来研究空位型缺陷的化学分析和电子结构

• 批准号: 10450229
• 负责人: HASEGAWA Masayuki
• 金额: $ 7.68万
• 依托单位: TOHOKU UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B).
• 财政年份: 1998
• 资助国家: 日本
• 起止时间: 1998 至 2000
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-10450229/
• 关键词: Positron Annihilation; BCC-Cu; Nano-particles; Fermi Surface; Reactor Pressure Vessel Steels; Fe-Cu; Al-Cu-Mg; Magic Number Vacancy Clusters; 電子運動量分布; 黒鉛; シリコン; 空孔クラスター; 酸素-空孔複合体; 酸素極性基; 原子空孔; 魔法数; 空孔・不純物

We have measured electron momentum distributions in wider ranges sampled by positrons in several metals and semiconductors using positron annihilation techniques of two dimensional angular correlation of annihilation radiation (2D-ACAR) and coincidence Doppler broadening (CDB). Marked results are as follows.1) Fe-Cu model alloys for nuclear reactor pressure vessel (RPV) steels containing harmful Cu impurities.A quantum-dot-like positron state is demonstrated in the defect-free Cu ultrafine particles embedded in Fe matrix. The wave functions of all positrons are entirely confined in the particles. The positrons in this state convey us usefu and exclusive information about the atomic and electronic structures of the particles. By 2D-ACAR experiments on Fe-1.0%Cu single crystals, we have determined the Fermi surface of BCC Cu ultrafine particles in Fe. The Fermi surface is almost spherical but has 12 necks around the centers of (110) Brillouin faces of the BCC structure.In neutron-irradiated Fe-Cu model alloys, we have observed irradiation-induced microvoids of which inner surfaces are almost coated with Cu atoms. After annealing around 4O0℃, the dissociation of vacancies from the microvoids leads to the formation of Cu ultrafine particles.2) Role of vacancy-solute complex in the initial rapid age hardening in Al-Cu-Mg alloy.Using CDB method, we have found that quenched-in vacancies are bound to Mg atoms rather than Cu atoms initially and the vacancy-Mg complexes easily migrate to vacancy sinks at 150℃. Vacancy-Mg-Cu complexes form during the initial 1 min aging at vacancy sinks. The dislocation-solute interaction is the origin of the initial rapid hardening.3) Mgic number vacanvy clusters in graphite and Si.By combining positron annihilation experiments and first-principles calculation, we firstly observed magic number vacancies in a covalent-bond materials : graphite after neutron irradiation.

我们已经测量了更宽的范围的电子动量分布在严重性金属和半导体中的采样，并在an灭辐射（2D-ACAR）的二维角相关性（2D-ACAR）和一致的多普勒宽度（CDB）的二维角相关性（CDB）中。反应器容器（RPV）含有危害的CU杂质。在无缺陷的CU超级铁颗粒中，嵌入了Fe矩阵中的量子。通过2D-ACAR实验的Fe-1.0％CU单晶的原子和电子结构，我们已经确定了BCC Cu Ultrafine颗粒的费米表面几乎是FERMI表面。 BCC结构的（110）Brillouin面的中心。在中子 - iRradiat Ed Fe-Cu模型合金中，我们观察到了辐射引起的微型小子，其内部表面几乎被CU原子涂覆。导致Ticles的形成。2）空位 - 溶剂在al-Cu-mg合金中的作用，我们一直是静置的空位空缺在150°C下下沉。空位空缺下降期间的空置MG-CU络合物形成。3）MGIC数字量固定群。第一原理计算，我们在共价 - 键材料中迅速观察到魔术数空位：中子照射后石墨。

项目成果

唐政、長谷川雅幸 永井康介 他6名: "Stable vacancy clusters in nautron-irradiated graphite:Evidence for aggregations with a magic number" Physical Review Letters. 82・13(3月29日号掲載予定). (1999)

Tomasa、Masayuki Hasekawa、Kosuke Nagai 等 6 人：《Stable vacancy Clusters in nautron-irradiated Graphite：Evidence for Aggregations with a magic number》《物理评论快报》82・13（预定于 3 月 29 日出版）。 1999）

Y.Nagai et al.: "Role of Vacancy-Solute Complex in the Initial Rapid Age Hardening in an Al-Cu-Mg Alloy"Acta Mater.. 59. 911-918 (2001)

Y.Nagai 等人：“空位-溶质复合体在 Al-Cu-Mg 合金初始快速时效硬化中的作用”Acta Mater.. 59. 911-918 (2001)

Y.Nagai et al.: "Positron confinement in ultrafine embedded particles : Quantum-dot-like state in Fe-Cu"Phys.Rev.. 61. 6574-6578 (2000)

Y.Nagai 等人：“超细嵌入粒子中的正电子限制：Fe-Cu 中的量子点状状态”Phys.Rev.. 61. 6574-6578 (2000)

M.Hasegawa, M.Saneyasu, M,Tabata, Z.Tang, Y.Nagai, T.Chiba and Y.Ito: "Positron and Positronium Studies of Irradiation-induced defects and microvoids in vitreous and metamict silica"Nucl.Instr.Meth. in Phys.Res.. B166-167. 431-439 (2000)

M.Hasekawa、M.Saneyasu、M、Tabata、Z.Tang、Y.Nagai、T.Chiba 和 Y.Ito：“玻璃体和变晶二氧化硅中辐照诱导缺陷和微孔的正电子和正电子研究”Nucl.Instr。

Y.Nagai et al.: "An Origin of Embrittlement of Reactor Pressure Vessel Steels : Ultra-fine Cu Precipitates"Phys.Rev.B. 63(in press). (2001)

Y.Nagai 等人：“反应堆压力容器钢脆化的起源：超细铜沉淀”Phys.Rev.B。