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Investigation of Subboundaries Evolution in Superplastically Deformed NiAl by positron lifetime

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Journal of Materials Science & Technology 2003年第4期19卷 373-375页

作者： XinghaoDU JiantingGUO BideZHOU LiangyueXIONG DepartmentofSuperalloys InstituteofMetalResearchChineseAcademyofSciencesShenyang110016China SchoolofMaterialSciencesandEngineering HarbinInstituteofTechnologyHarbin150001China

In order to study the subboundaries evolution in superplastically deformed NiAl, the positron lifetime change during superplastic deformation process was measured. It is shown that the superplastic deformation of NiAl has not influence on its T2, the newly recrystallized grain boundaries formed during entire superplastic deformation process belong to the calegory of subboundaries and have not contribution to the superplastic strain.

关键词： NiAl positron lifetime Superplasticity Boundaries

Self-consistent field method and non-self-consistent field method for calculating the positron lifetime

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Chinese Physics B 2010年第11期19卷 658-661页

作者：张杰刘建党陈祥磊叶邦角 Department of Modern Physics University of Science and Technology of China

Many methods are used to calculate the positron lifetime, these methods could be divided into two main types. The first method is atomic superposition approximation method and the second one is the so called energy band calculation method. They are also known as the non-self-consistent field method and self-consistent field method respectively. In this paper, we first introduce the two basic methods and then, we take Si as an example and give our calculation results, these results coincide with our latest experimental results, finally, we discuss the advantages and disadvantages of the two methods.

关键词： positron lifetime atomic superposition approzimetion method pseudopotential method

Design of a high-sampling-rate electronic module for array-detector positron annihilation lifetime measurements

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Radiation Detection Technology and Methods 2019年第3期3卷 127-135页

作者： Jiale Cai Daowu Li Yingjie Wang Zhiming Zhang Peilin Wang Haohui Tang Baoyi Wang Xingzhong Cao Fuyan Liu Long Wei Beijing Engineering Research Center of Radiographic Techniques and Equipment Institute of High Energy PhysicsChinese Academy of SciencesBeijing 100049China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China School of Nuclear Science and Technology University of Chinese Academy of SciencesBeijing 100049China

Introduction In this study,a high-time-resolution electronic module with a high channel density and low power consumption was designed for the measurement of the multi-detector array positron annihilation lifetimes.This electronic module consisted of 32 input channels,and each channel provided a high sampling rate up to 5.12 GSPS based on a Domino Ring Sampler 4(DRS4)chip.Compared to the high-speed flash analog-digital converter(FADC),DRS4 chip has a higher channel density with an affordable lower price and power consumption.Methods The developed electronic module was also capable of real-time data analysis for directly extracting the time information of input signals at the data acquisition site,thereby significantly decreasing the data rate.The digital constant fraction discriminator(DCFD)algorithm was implemented in the field programmable gate array(FPGA)for performing the time pick-up.Results The coincidence time resolution of the electronic module was measured,and the test results revealed a value of 26 ps.A prototypical 16-pixel detector module of the multi-detector system was evaluated using this electronic module,and the coincidence time resolution of the prototypical module was 411.84 ps.Conclusions The electronic module was confirmed to satisfy the severe requirements of the multi-array-detector positron annihilation lifetime measurement system.It was also suitable for other high-time-resolution,high-channel-density,costeffective,and low-power-consumption applications.

关键词： Digital constant fraction discriminator FPGA DRS4 positron lifetime

Gas-phase hydrogenation influence on defect behavior in titanium-based hydrogen-storage material

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Progress in Natural Science:Materials International 2017年第1期27卷 105-111页

作者： Roman S.Laptev Viktor N.Kudiiarov Yuri S.Bordulev Andrey A.Mikhaylov Andrey M.Lider Department of General Physics Institute of Physics and Technology National Research Tomsk Polytechnic University

Titanium and its alloys are promising materials for hydrogen storage. However, hydrogen penetration accompanies the exploitation of hydrogen storage alloys. In particular, hydrogen penetration and accumulation in titanium alloys changes their mechanical properties. Therefore, the research works of such materials are mainly focused on improving the reversibility of hydrogen absorption-liberation processes, increasing the thermodynamic characteristics of the alloys, and augmenting their hydrogen storage capacity. In the process of hydrogenation-dehydrogenation, the formed defects both significantly reduce hydrogen storage capacity and can also be used to create effective traps for hydrogen. Therefore, the investigation of hydrogen interaction with structural defects in titanium and its alloys is very important. The present work, the hydrogen-induced formation of defects in the alloys of commercially pure titanium under temperature gas-phase hydrogenation（873 K） has studied by positron lifetime spectroscopy and Doppler broadening spectroscopy. Based on the evolution of positron annihilation parameters τ_f, τd, their corresponding intensities If, Idand relative changes of parameters S/S0and W/W0, the peculiarities of hydrogen interaction with titanium lattice defects were investigated in a wide range of hydrogen concentrations from 0.8at% to 32.0at%.

关键词： Titanium Hydrogen Lattice defects positron annihilation positron lifetime Doppler broadening

The effects of fast neutron irradiation on oxygen in Czochralski silicon

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Chinese Physics B 2009年第1期18卷 293-297页

作者：陈贵锋阎文博陈洪建李兴华李养贤 School of Material Science and Engineering Hebei University of Technology

The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon （CZ-Si） are investigated systemically by using Fourier transform infrared （FTIR） spectrometer and positron annihilation technique （PAT）. Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration （[Oi]） in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V4 appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies （0.1-1.0eV） can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms （O） at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [Oi] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.

关键词： neutron irradiation irradiation defects FTIR spectrometer positron lifetime

Exploring positron characteristics utilizing two new positron–electron correlation schemes based on multiple electronic structure calculation methods

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Chinese Physics B 2015年第10期24卷 535-542页

作者：张文帅谷冰川韩小溪刘建党叶邦角 Department of Modern Physics University of Science and Technology of China State Key Laboratory of Particle Detection and Electronics University of Science and Technology of China

We make a gradient correction to a new local density approximation form of positron-electron correlation. The positron lifetimes and affinities are then probed by using these two approximation forms based on three electronic-structure calculation methods, including the full-potential linearized augmented plane wave（FLAPW） plus local orbitals approach,the atomic superposition（ATSUP） approach, and the projector augmented wave（PAW） approach. The differences between calculated lifetimes using the FLAPW and ATSUP methods are clearly interpreted in the view of positron and electron transfers. We further find that a well-implemented PAW method can give near-perfect agreement on both the positron lifetimes and affinities with the FLAPW method, and the competitiveness of the ATSUP method against the FLAPW/PAW method is reduced within the best calculations. By comparing with the experimental data, the new introduced gradient corrected correlation form is proved to be competitive for positron lifetime and affinity calculations.

关键词： positron annihilation positron lifetime electronic structure

Variation of Radiation Damage with Irradiation Temperature and Dose in CLAM Steel

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Plasma Science and Technology 2012年第7期14卷 629-631页

作者：郑永男黄群英彭蕾左翼范平周冬梅袁大庆吴宜灿朱升云 China Institute of Atomic Energy Institute of Plasma Physics Chinese Academy of Sciences

The dependences of radiation induced defects on irradiation temperature up to 700℃ at 15 dpa and on irradiation dose up to 85 dpa at room temperature have been investigated by the heavy ion irradiation and the positron annihilation lifetime spectroscopy for the CLAM. A void size peak is observed at -500℃ where the vacancy cluster contains 9 vacancies and has an average diameter of 0.59 nm. The size of the vacancy clusters increases with the increase of irradiation dose at room temperature, and the vacancy cluster at 85 dpa consists of 9 vacancies and reaches a size of 0.60 nm in diameter. The absolute values of the void size at the peak and the increase of void size with dose in the CLAM steel are negligible compared to those of the normal stainless steels, indicating that the CLAM steel has good radiation resistant property.

关键词： radiation damage CLAM steel heavy ion irradiation simulation positron lifetime

Precipitation Study in Inconel 625 Alloy by positron Annihilation Spectroscopy

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Journal of Materials Science & Technology 2003年第5期19卷 434-436页

作者： M.Ahmad. W.Ahmad. M.A.Shaikh Mahmud Ahmad M.U.Rajput Nuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad PakistanNuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad PakistanNuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad PakistanNuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad Pakistan Nuclear Physics Division Pakistan Institute of Nuclear Science & Technology P.O. Nilore Islamabad Pakistan

Precipitation in Inconel 625 alloy has been studied by positron annihilation spectroscopy and electron microscopy. The observed dependence of annihilation characteristics on aging time is attributed to the change of the positron state due to the increase and decrease of the density and size of the 7' precipitates. Hardness measurements and lifetime measurements are in good agreement.

关键词： positron lifetime Precipitation Inconel 625 alloy Fast-fast coincidence system Hardness

SEM and positron Annihilation Technology Investigation on the Defect Change with Thermal Treatment Temperature in GaP

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Semiconductor Photonics and Technology 1997年第2期3卷 3-8+19页

作者： ZHANG Fujia,SHAO Jiafeng,ZHANG Dejian (Department of Physics,Lanzhou University,Lanzhou 730001,CHN) QI Li,GAN Runjin (Beijing Mechanical Industry Institute,Beijing 100083,CHN)

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关键词： Defects positron lifetime Thermal Treatment