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Characterization,spectroscopic investigation of defects by positron annihilation,and possible application of synthesized PbO nanoparticles

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Chinese Physics B 2021年第2期30卷 400-407页

作者： Sk Irsad Ali Anjan Das Apoorva Agrawal Shubharaj Mukherjee Maudud Ahmed P M G Nambissan Samiran Mandal Atis Chandra Mandal Department of Physics University of BurdwanGolapbagBurdwan 713104West BengalIndia Department of Physics A.P.C.Roy Government CollegeSiliguriDarjeeling 734010West BengalIndia Applied Nuclear Physics Division Saha Institute of Nuclear Physics1/AF BidhannagarKolkata 700064India Department of Physics Government General Degree College at PedongKalimpong 734311West BengalIndia

Nanocrystalline samples of highly pure lead oxide were prepared by the sol-gel route of synthesis.X-ray diffraction and transmission electron microscopic techniques confirmed the nanocrystallinity of the samples,and the average sizes of the crystallites were found within 20 nm to 35 nm.The nanocrystallites exhibited specific anomalous properties,among which a prominent one is the increased lattice parameters and unit cell volumes.The optical band gaps also increased when the nanocrystallites became smaller in size.The latter aspect is attributable to the onset of quantum confinement effects,as seen in a few other metal oxide nanoparticles.positron annihilation was employed to study the vacancy type defects,which were abundant in the samples and played crucial roles in modulating their properties.The defect concentrations were significantly larger in the samples of smaller crystallite sizes.The results suggested the feasibility of tailoring the properties of lead oxide nanocrystallites for technological applications,such as using lead oxide nanoparticles in batteries for better performance in discharge rate and resistance.It also provided the physical insight into the structural build-up process when crystallites were formed with a finite number of atoms,whose distributions were governed by the site stabilization energy.

关键词： lead oxide nanocrystals positron annihilation sol-gel processes

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Evolution of native point defects in ZnO bulk probed by positron annihilation spectroscopy

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Chinese Physics B 2009年第5期18卷 2072-2077页

作者：彭成晓王科范张杨郭凤丽翁惠民叶邦角 Physics and Electronics School Henan University Modern Physics Department University of Science and Technology of China

This paper studies the evolution of native point defects with temperature in ZnO single crystals by positron lifetime and coincidence Doppler broadening （CDB） spectroscopy, combined with the calculated results of positron lifetime and electron momentum distribution. The calculated and experimental results of the positron lifetime in ZnO bulk ensure the presence of zinc monovacancy, and zinc monovacancy concentration begins to decrease above 600 ℃ annealing treatment. CDB is an effective method to distinguish the elemental species, here we combine this technique with calculated electron momentum distribution to determine the oxygen vacancies, which do not trap positrons due to their positive charge. The CDB spectra show that oxygen vacancies do not appear until 600℃ annealing treatment, and increase with the increase of annealing temperature. This study supports the idea that green luminescence has a close relation with oxygen vacancies.

关键词： positron annihilation ZnO native defects

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Investigation of SPPO Membranes by positron annihilation Lifetime Spectroscopy

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Plasma Science and Technology 2006年第5期8卷 573-576页

作者： Htwe Htwe Yin 阴泽杰唐世彪黄环 Department of Modern Physics University of Science and Technology of China Hefei 230026 China Department of Chemistry University of Science and Technology of China Hefei 230026 China

positron annihilation lifetime spectroscopy （PALS） is a powerful technique to study the free volume in polymers. The lifetime of ortho-positronium （o-Ps）, a bound state of an electron and a positron, can be used to assess the pore size while the intensity can be used to characterize the number of pores. On the basis of the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes in the sulfonated poly （2,6-dimethyl-1,4- phenyleneoxide）（SPPO） membranes with different amounts of LiCl were calculated. It was found that, with the increasing amount of LiCl, the free volume radius and the fractional free volume firstly increased and then decreased. After immersing the membranes in distilled water, the free volume radius and the fractional free volume changed with different water concentrations in the membrane.

关键词： positron annihilation pore size free volume SPPO polymer water concentration

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Theoretical study on the positron annihilation in Rocksalt structured magnesium oxide

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Chinese Physics B 2011年第5期20卷 413-417页

作者：刘建党张杰张丽娟郝颖萍郭卫锋成斌叶邦角 Department of Modern Physics University of Science and Technology of China

Based on the atomic superposition approximation （ATSUP） and first-principles pseudopotential plane-wave methods, the bulk and Mg mono-vacancy positron lifetime of magnesium oxide were calculated using Arponen-Pajamme and Borofiski-Nieminen positron-annihilation-rate interpolation formula respectively. The calculated values are in good agreement with experimental values and the first-principles method gives more convincing results. The positron annihilation density spectra analysis reveals that positrons mainly annihilate with valence electrons of oxygen atoms when the magnesium-vacancy appears within magnesium oxide.

关键词： magnesium oxide positron annihilation momentum distribution

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Effects of MeV Fe Ions Irradiation on the Microstructure and Property of Nuclear Grade 304 Stainless Steel:Characterized by positron annihilation Spectroscopy,Transmission Electron Microscope and Nanoindentation

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Acta Metallurgica Sinica(English Letters) 2021年第12期34卷 1695-1703页

作者： Honglin Yan Zhiming Zhang Jianqiu Wang Bright O.Okonkwo En-Hou Han Key Laboratory of Nuclear Materials and Safety Assessment Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China

Nuclear grade 304 stainless steel was irradiated by 3.5 MeV Fe ions,with fluxes of 3.05E+15 ions/cm^(2)and 1.55E+16 ions/cm^(2).Irradiation effects were studied by positron annihilation spectroscopy(PAS),transmission electron microscope(TEM)and nanoindentation techniques.PAS results showed that different types of defects were produced after irradiation and that there was significant variance in defects formed when the samples were subjected to different irradiation doses.TEM characterization showed that the irradiation-induced dislocation loops enlarged in average size,but decreased in number density at higher irradiation doses.Nanoindentation test showed obvious irradiation hardening phenomenon,which was in good agreement with the PAS and TEM results.Irradiation hardening effect increased with an increase in irradiation dose and saturation occurred with an increase in irradiation dose from 3.2 to 16 dpa.Further statistical analysis showed that barrier strength of the Frank loop depends on the loop size and density produced by the ion irradiation.

关键词： Stainless steel Irradiation hardening positron annihilation Nanoindentation

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Dislocation Densites of Deformed Steel Sheets Based on positron annihilation

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International Journal of Minerals,Metallurgy and Materials 1998年第1期12卷 47-50页

作者： Yonglin Kang Xianjin Wang (Materials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China) Materials Science and Engineering School University of Science and Technology Beijing Beijing 100083 China

The variation regularity of dislocation densites of some deformed steel sheets under three kinds of strainpaths as uniaxial tension, plane strain and equal biaxial stretching was investigated by means of positron lifetimespectrum and Doppler-broadening techniques. The results show that the increasing rate of dislocation densites isrelated to the plastic strain path. A relationship between the increasing rate of micro-defects, macro-instability andforming limits during the process of steel sheet forming was got based on analyzing the mechanism of dislocationdensity increasing under different stress-strain condihons.

关键词： positron annihilation dislocation steel sheet strain path

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Comparison of the Free Volume of LiCl-Added SPPO Membrane and SPPO-PES Blend Membrane by positron annihilation Method

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Plasma Science and Technology 2007年第5期9卷 575-577页

作者： Htwe Htwe YIN 黄环唐世彪马庆力 Department of Modern Physics University of Science and Technology of ChinaHefei 230026China Center of Physical Experiment and Teaching School of ScienceUniversity of Science and Technology of ChinaHefei 230026China Electronics Department Electronic Engineering InstituteHefei 230038China

positron annihilation lifetime spectroscopy （PALS） is a powerful technique for the study of free volume in polymers. The lifetime of ortho-positronium （o-Ps）, a bound state of an electron and a positron, can be used to assess the pore size, while the intensity can be used to characterize the number of pores. Based on the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes of sulfonated poly （2,6-dimethyl-1,4- phenyleneoxide）（SPPO） membranes with added LiCl and SPPO-PES （Polyethersulfone） blend were compared. Free volume radii in both kinds of membranes are discussed.

关键词： positron annihilation free volume pore size SPPO polymer blend

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Effect of vacancy charge state on positron annihilation in silicon

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Chinese Physics B 2013年第10期22卷 394-396页

作者：刘建党成斌孔伟叶邦角 State Key Laboratory of Particle Detection and Electronics University of Science and Technology of China Department of Modern Physics University of Science and Technology of China

The charge-state-dependent lattice relaxation of mono-vacancy in silicon is studied using the first-principles pseu- dopotential plane-wave method. We observe that the structural relaxation for the first-neighbor atoms of the mono-vacancy is strongly dependent on its charge state. The difference in total electron density between with and without charge states in mono-vacancy and its relevant change due to the localized positron are also examined by means of first-principles simu- lation, demonstrating the strong interplay between positron and electron. Our calculations reveal that the positron lifetime decreases with absolute charge value increasing.

关键词： vacancy charge state positron annihilation

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Identification of the pressure-induced phase transition of ZnSe with the positron annihilation method

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Chinese Physics B 2011年第10期20卷 452-456页

作者：刘建党成斌张杰张丽娟翁惠民叶邦角 Department of Modern Physics University of Science and Technology of China

This paper studies the pressure-induced phase transition between zincblende （B3） and NaC1 （B1） structure ZnSe by using the hydrostatic pressure first-principles pseudopotential plane wave method. The energy-volume and enthalpy- pressure curves are employed to estimate the transition pressure. It is found that ZnSe undergoes a first-order phase transition from the B3 structure to the B1 structure at approximately 15 GPa derived from the energy-volume relation and 14 GPa based on deduction from enthalpy pressure data. The pressure-related positron bulk lifetimes of the two ZnSe structures are calculated with the atomic superposition approximation method. In comparison with the 13.4% reduction in volume of ZnSe at the transition pressure, the positron bulk lifetime decreases more significantly and the relative value declines up to 22.3%. The results show that positron annihilation is an effective technique to identify and characterize the first-order phase transition and can give valuable information about changes in micro-scale, such as volume shrinkage and compressibility.

关键词： high-pressure phase transition positron annihilation

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A compact positron annihilation lifetime spectrometer

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Chinese Physics C 2011年第1期35卷 100-103页

作者：李道武刘军辉章志明王宝义张天保魏龙 Key-Laboratory of Nuclear Analysis Techniques Institute of High Energy PhysicsChinese Academy of Sciences Graduate University of Chinese Academy of Sciences

Using LYSO scintillator coupled on HAMAMATSU R9800 （a fast photomultiplier） to form the small size γ-ray detectors, a compact lifetime spectrometer has been built for the positron annihilation experiments. The system time resolution FWHM=193 ps and the coincidence counting rate -8 cps/p.Ci were achieved. A lifetime value of 219±1 ps of positron annihilation in well annealed Si was tested, which is in agreement with the typical values published in the previous lectures.

关键词： compact PLS LYSO positron annihilation

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