贮氢合金正电子湮没和扰动角关联研究

本工作用正电子湮没和扰动角关联方法研究Pd0.75Ag0.25和LaNi4.25Al0.75两种贮氢合金。在77～295K温区和0～0.35氢浓度范围用正电子湮没寿命测量方法研究了Pd0.75Ag0.25Hx样品。实验测量的正电子湮没寿命谱用两个寿命成份表征。短寿命成份τ1是自由正电子湮没寿命,不随温度和氢     

66 贮氢合金正电子湮没和扰动角关联研究

本工作用正电子湮没和扰动角关联方法研究Pd0.75Ag0.25和LaNi4．25Al0.75两种贮氢合金。     

用正电子湮没方法研究有机导体

本工作用正电子湮没方法研究了几种新的电荷转移复合物型的有机导体。测定了在这些材料中正电子湮没的线形参数S、湮没寿命和3γ湮没相对产额。实验结果见下表。     

液态轧制Fe-3%Si中的正电子湮没参数

用正电子湮没方法研究非晶态合金对认识非晶态的结构模型、电子结构、缺陷分布、结构弛豫、晶化过程起了不可忽视的作用。近年来,在急冷淬火制备非晶态合金带材的基础上又发展了一种崭新的工艺,即液态急冷轧制。因为它降温速率比急冷淬火的慢,且轧制出的带材有较大的厚度,制备的带材呈晶态结构,换句话说,它克服了急冷淬火制备非晶态带材中所存在的热稳定性问题,从而可望短期内在工业生产中得到实际广泛应用,并大大减少生产工序,节约能源和成本。本文报道了用正电子湮没多普勒展宽能谱对液态急冷轧制的Fe-3％Si(工业中所用的一种矽钢的成分)的测量结果,以探索正电子湮没方法在该类合金中的适用性。     

Ti-6Al-4V合金中α′马氏体转变的正电子湮没研究

本文用正电子湮没方法研究了高温淬火后的Ti-6Al-4V合金,在200—1000℃范围内各温度下等时时效后的S参数随温度的变化规律。并借此讨论了α’马氏体转变机制     

用正电子湮没技术研究新锆合金包壳的离子辐照效应

国产Zr-Sn-Nb系新锆合金SZA-4和SZA-6是CAP1400大型先进压水堆包壳材料的主要候选材料,对其辐照性能的研究可为制备工艺改进提供科学依据。在中国原子能科学研究院HI-13串列加速器辐照终端,在300 ℃温度下,用100 MeV的Fe束流对两种新锆合金包壳管材进行5 dpa剂量辐照。辐照前后的正电子湮没寿命测量表明：两种样品辐照前湮没寿命为Zr中单空位寿命,表明管材制备过程中最后的退火温度和时间尚未完全消除加工引入的缺陷;两种样品辐照后的正电子湮没寿命减小,分析表明这是由于辐照导致Fe在锆合金中重新分布,主要分布在bcc结构的β-Nb沉淀相颗粒与hcp结构的α-Zr基体之间具有开空间的相界,正电子被相界捕获,与周围Fe原子电子湮没,造成湮没寿命减小。     

超塑形变Al-6Cu-0.5Zr合金正电子湮没寿命测量

正电子对材料内部原子尺度缺陷(如空位、空位团、微空洞等)十分敏感。本文介绍不同形变量的超塑性Al-6Cu-0.5Zr合金正电子寿命测量结果。用两态捕获模型分析,得出正电子湮没平均寿命与形变量的关系。     

非晶合金(Co_(0.85)Ni_(0.08)Fe_(0.06)Nb_(0.01))_(75)Si_(10)B_(15)的正电子湮没研究

用正电子湮没寿命技术研究了非晶合金(Co_(0.85)Ni_(0.08)Fe_(0.06)Nb_(0.01))_(75)Si_(10)B_(15)的结构弛豫和晶化过程。样品取自觉42mm、厚0.035mm的快淬非晶条带,经X射线衍射证明是非晶态。样品在真空中不同温度下等时退火40分钟,处理后的样品在室温下进行正电子湮没寿命测量。同样样品在室温下进行热电动势测量,将结果和正电子寿命结果比较。     

用正电子寿命方法研究Fe-Ni-Co合金中氢损伤

铁镍铬合金(型号4J29)是能和玻璃封接的定膨胀合金,主要用于晶体管、集成电路外引 线等。由于存在延迟断裂问题,影响了元件的可靠性。本文用正电子湮没方法对4J29合金中氢损伤行为进行了探讨。     

1996年全年分类主题索引

１９９６年全年分类主题索引用页Ａ１３．１０固体与流体物理学的核现象与核技术在束穆斯堡尔实验装置…………２８５用正电子湮没技术研究深低温下Ａ卜ｈ－ＣＵ－Ｍｇ—Ｚｒ合金中的缺陷和电子密度··３１６０用正电子湮没寿命技术研究掺杂的ＩｎＰ……７３９５粒子关联...     

Irradiation effects on thermal diffusivity and positron annihilation lifetime in ceramics induced by neutron and 30 MeV electron

Measurements of thermal diffusivity and positron annihilation lifetime were performed on neutron- and 30 MeV electron-irradiated ceramics. Thermal diffusivity of heavily neutron-irradiated ceramics decreased to a very low level and the difference between specimens was small. Positron annihilation lifetime of these specimens also showed a distinct change; however, the difference between specimens was also small. Accordingly, in this study, electron irradiation was performed to 0.01–0.02 dpa via the 30 MeV KURRI-Linac. The electron-irradiated specimens also showed obvious degradation in thermal diffusivity and an increment in positron annihilation lifetime, and it was clarified that positron annihilation lifetime showed some correlation with thermal diffusivity.     

Beyond fusion,annihilation reactions of confined hydrogen

Theoretical mechanisms showing how antineutrons can enter a region of confined hydrogen or deuterium and decay into antiprotons is given. An annihilation reaction of a proton and antiproton releases energy. This starts a series of deuterium fissions that increase the probability of annihilation reactions. The gamma rays produced lose momentum via radiation pressure vibrations of the surrounding confinement lattice. This constitutes a change of radiation energy to kinetic energy, exhibited as heating of the lattice material. A likely mechanism of mass changing to energy is the annihilation of large particles breaking into a multiplicity of repeated less energetic positron annihilations. The explanation given shows that it is possible in theory to utilize the tremendous energy available from annihilation reactions. The harnessing of this final frontier of energy and power could ultimately prove to be the most useful energy source, particularly for propulsion systems. The reaction cited may be the initial step in using the energy from annihilation reactions. Excess heat from a Pons — Fleischmann-type reaction can be accounted for as annihilation, not fusion.     

On the stabilization of positron annihilation Doppler-broadening data

The present investigation compares three different methods for stabilizing positron annihilation Doppler-broadening data. The three methods have in common the use of a reference gamma ray line, which is simultaneously measured with the positron annihilation line at 511 keV. It is shown that a regressional method should be used whenever the dominating instability in the data has a random nature. A practical example of an application of the regressional method is given.     

Fe—B超细微晶合金的正电子湮没研究

用正电子湮没技术对急地制备了Ｆｅ－Ｂ合金结晶态超细微粒（ＣＵＦＰ）的微结构进行了分析，寿命谱研究结果与正电子三态湮没模型相吻合，研究了Ｆｅ－Ｂ－ＣＵＦＰ的结晶与非晶两种结构的微缺陷，并推测Ｆｅ－Ｂ－ＣＵＦＰ聚集体（纳米晶膜）材料具有类原子气态微结构的可能性。     

Dependence of resonant positron-molecule annihilation on molecular temperature

Measurements of positron-on-molecule annihilation as a function of positron energy have established that positrons can bind to hydrocarbon molecules via vibrational Feshbach resonances. The magnitudes of these resonances, which grow rapidly with increasing molecular size, are still not well understood. In this paper, the role of molecular temperature is investigated using a specially designed temperature-regulated annihilation cell. Only relatively small changes in annihilation rate are observed when the molecular temperature is varied by a factor of two, from 300 K down to approximately half that value for the alkane molecules pentane and heptane. These results place important constraints on theories of the annihilation rates and positron-molecule binding energies.     

Doppler-broadening measurements of positron annihilation with high-momentum electrons in pure elements

Doppler-broadening measurements of the electron–positron annihilation line in twenty-seven single-element samples are presented. A coincidence technique has been used to suppress the background and to evidence the contribution of positron annihilation with core electrons. Systematic dependences on the atomic number of the target material are found in ratio curves obtained dividing the measured spectra by the spectrum of a reference material. The positron lifetime technique has been used to detect the presence of positron traps in all the samples. The change in the high-momentum part of the annihilation line due to positron trapping is illustrated. The measured data are in a good qualitative agreement with recent theoretical calculation and constitute the most complete measurement series, up to now, to establish a future data-base for positron annihilation spectroscopy.     

铁中空位的正电子湮没特性

从第一性原理和二分量密度泛函理论出发．应用离散变办法和嵌入集团模型完全自洽地计算了不同相状态的铁单空位的正电子湮没特性．同时讨论了晶格膨胀和晶格弛豫对正电子湮没特性的影响。     

辐射损伤的正电子湮没和扰动角关联研究(英文)

用正电子湮没和扰动角关联二种方法研究了Si和Nb的辐射损伤。采用正电子湮没方法得到的结果与扰动角关联的完全一致。     

Detrapping behavior of tritium trapped via hot atom chemical process in neutron-irradiated ternary lithium oxides

Tritium detrapping behavior in neutron-irradiated ternary lithium oxides was investigated by the comparison of the annihilation of irradiation defects with the tritium release. It was revealed that the annihilation of irradiation defects would consist of two processes; namely the fast and the slow ones. The slow annihilation process has correlation with the tritium release, indicating that E′-center or F⁺-center could act as tritium trapping site, and from its activation energy of each sample, the annihilation of E′-center and F⁺-center could be attributed to the recovery of oxygen via diffusion, triggering the tritium release. Meyer-Neldel plots of these results indicate that the slow annihilation process was governed by the formation entropy of a pair of vacancy and interstitial atom of oxygen. Therefore, the trapped tritium would be detrapped by oxygen recovery to E′-center or F⁺-center, and its kinetics would be determined by the population of oxygen vacancy under thermal equilibrium.