首页 | 本学科首页   官方微博 | 高级检索  
    检索          
共有20条相似文献,以下是第1-20项 搜索用时 78 毫秒

1.  Helium-Implantation-Induced Damage in NHS Steel Investigated by Slow-Positron Annihilation Spectroscopy  
   LI Yuan-Fei  SHEN Tie-Long  GAO Xing  GAO Ning  YAO Cun-Feng  SUN Jian-Rong  WEI Kong-Fang  LI Bing-Sheng  ZHANG Peng  CAO Xing-Zhong  ZHU Ya-Bin  PANG Li-Long  CUI Ming-Huan  CHANG Hai-Long  WANG Ji  ZHU Hui-Ping  WANG Dong  SONG Peng  SHENG Yan-Bin  ZHANG Hong-Peng  HU Bi-Tao  WANG Zhi-Guang《中国物理快报》,2014年第3期
   Evolutions of defects and helium contained defects produced by atomic displacement and helium deposition with helium implantation at different temperatures in novel high silicon (NHS) steel are investigated by a slow positron beam. Differences of the defect information among samples implanted by helium to a fluence of 1×1017 ions/cm2 at room temperature, 300°C, 450°C and 750°C are discussed. It is found that the mobility of vacancies and vacancy clusters, a recombination of vacancy-type defects and the formation of the He-V complex lead to the occurrence of these differences. At high temperature irradiations, a change of the diffusion mechanism of He atoms/He bubbles might be one of the reasons for the change of the S-parameter.    

2.  Molecular dynamics simulations of displacement cascades in Fe-10%Cr systems  
   郁刚  马雁  蔡军  陆道纲《中国物理 B》,2012年第3期
   Molecular dynamics simulations of the displacement cascades in Fe-10%Cr systems are used to simulate the primary knocked-on atom events of the irradiation damage at temperatures 300,600,and 750 K with primary knockedon atom energies between 1 and 15 keV.The results indicate that the vacancies produced by the cascade are all in the central region of the displacement cascade.During the cascade,all recoil Fe and Cr atoms combine with each other to form Fe-Cr or Fe-Fe interstitial dumbbells as well as interstitial clusters.The number and the size of interstitial clusters increase with the energy of the primary knocked-on atom and the temperature.A few large clusters consist of a large number of Fe interstitials with a few Cr atoms,the rest are Fe-Cr clusters with small and medium sizes.The interstitial dumbbells of Fe-Fe and Fe-Cr are in the 111 and 110 series directions,respectively.    

3.  Defect types and room-temperature ferromagnetism in undoped rutile TiO2 single crystals  
   李东翔  秦秀波  郑黎荣  李玉晓  曹兴忠  李卓昕  杨静  王宝义《中国物理 B》,2013年第22卷第3期
   Room-temperature ferromagnetism has been experimentally observed in annealed rutile TiO2 single crystals when a magnetic field is applied parallel to the sample plane.By combining X-ray absorption near the edge structure spectrum and positron annihilation lifetime spectroscopy,Ti3+-V O defect complexes(or clusters) have been identified in annealed crystals at a high vacuum.We elucidate that the unpaired 3d electrons in Ti3+ ions provide the observed room-temperature ferromagnetism.In addition,excess oxygen ions in the TiO2 lattice could induce a number of Ti vacancies which obviously increase magnetic moments.    

4.  Trapping and diffusion behaviors of helium at vacancy in iron from first principles  
   LIU YueLin  SHI WenPu《中国科学:物理学 力学 天文学(英文版)》,2013年第6期
   We investigate the structure,trapping,and diffusion behaviors of helium(He) at vacancy in a Fe single crystal using first-principles simulations.Vacancy with more space can provide the lower electron density region for He binding in comparison with intrinsic Fe,causing He to diffuse into the vacancy inner easily.We provide the quantitative microscopic studies related to the atomic-level thermo-kinetic trapping processes.Moreover,such physical viewpoint can be applied to other vacancy-like defects such as vacancy clusters,void and grain boundaries which can open a space with reduced electron density region to increase He binding in metals and metal alloys.    

5.  Structural Distortion and Defects in Ti_3AlC_2 irradiated by Fe and He Ions  
   庞立龙  李炳生  申铁龙  高星  方雪松  高宁  姚存峰  魏孔芳  崔明焕  孙建荣  常海龙  何文豪  黄庆  王志光《中国物理快报》,2018年第2期
   Ti_3AlC_2 samples are irradiated in advance by 3.5 MeV Fe-ion to the fluence of 1.0×10~(16) ion/cm~2,and then are implanted by 500 keV He-ion with the fluence of 1.0×10~(17) ion/cm~2 at room temperature.The irradiated samples are investigated by grazing incidence x-ray diffraction(GIXRD) and transmission electron microscopy(TEM).GIXRD results show serious structural distortion,but without amorphization in the irradiated samples.Fe-ion irradiation and He-ion implantation create much more serious structural distortion than single Fe-ion irradiation.TEM results reveal that there are a large number of defect clusters in the damage region,and dense spherical He bubbles appear in the He depositional region.It seems that the pre-damage does not influence the growth of He bubbles,but He-ion implantation influences the pre-created defect configurations.    

6.  Effects of Grain Boundary Characteristics on Its Capability to Trap Point Defects in Tungsten  
   何文豪  高星  高宁  王霁  王栋  崔明焕  庞立龙  王志光《中国物理快报》,2018年第2期
   As recombination centers of vacancies(Vs) and self-interstitial atoms(SIAs), firstly grain boundaries(GBs)should have strong capability of trapping point defects. In this study, abilities to trap Vs and SIAs of eight symmetric tilt GBs in tungsten are investigated through first-principles calculations. On the one hand, vacancy formation energy E~f_V rapidly increases then slowly decreases as the hard-sphere radius r_0 of the vacancy increases.The value of E~f_V is the largest when r_0 is about 1.38 ?, which is half the distance between the nearest atoms in equilibrium single crystal tungsten. That is, any denser or looser atomic configuration around GBs than that in bulk is helpful to form a vacancy. On the other hand, SIA formation energy E~f_(SIA) at GBs decreases monotonically with increasing the hard-sphere radius of the interstitial sites, which indicates that GBs with larger interstitial sites have stronger ability to trap SIAs. Based on the data obtained for GBs investigated in this study, it is found that the ability to trap Vs increases as the GB energy increases, and the capability of trapping SIAs linearly increases as the excess volume of GB increases. Due to its lowest GB energy and smallest excess volume among all GBs studied, twin GB ∑3(110)[111] has the weakest capability to trap both Vs and SIAs.    

7.  Semiclassical Calculation of Recurrence Spectra of Rydberg Hydrogen Atom Near a Metal Surface  
   WANG De-Hua《理论物理通讯》,2009年第51卷第2期
   Using closed orbit theory, we give a clear physical picture description of the Rydberg hydrogen atom near a metal surface and calculate the Fourier transformed recurrence spectra of this system at different scaled energies below ionization threshold. The results show that with the increase of the scaled energy, the number of the closed orbit increases greatly. Some of the orbits are created by the bifurcation of the perpendicular orbit. This case is quite similar to the Rydberg atom in an electric field. When the scaled energy increases furthermore, chaotic orbits appear. This study provides a different perspective on the dynamical behavior of the Rydberg atom near a metal surface.    

8.  The effects of fast neutron irradiation on oxygen in Czochralski silicon  
   陈贵锋  阎文博  陈洪建  李兴华  李养贤《中国物理 B》,2009年第18卷第1期
   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 C.After the CZ-Si is annealed at 600 C,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 C,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 C.It turns out that the large fluctuation of [Oi] after short-time annealing from 500 to 700 C results from the transformation of fast neutron irradiation defects.    

9.  Coalescence of heteroclusters Au767 and Ag767: a molecular-dynamics study  
   李国建  王强  李虎田  王凯  赫冀成《中国物理 B》,2008年第17卷第9期
   This paper studies the coalescence of heteroclusters Au767 and Ag767 by using molecular dynamics with the embedded atom method, where layer atomic energy is employed to describe the potential energy variation of per atom in different layers along radial direction. The results show that the coalescence is driven by releasing the atomic energy of the coalesced zone. The deformation, which is induced by substitutional and vacancy diffusion during the coalescence, makes the coalesced cluster disorder. If the summation of the thermal energy and the released atomic energy is large enough to keep the disorder state, the clusters form a metastable liquid droplet; otherwise, the clusters coalesce into a solid cluster when the coalesced cluster reaches the equilibrium state, and the coalesced cluster experiences liquid to solid ordering changes during the coalescence of a solid Au767 with a liquid Ag767 and a liquid Au767 with a liquid Ag767. The centre of figure of the cluster system is shifted during the coalescence process, and higher coalescence temperature causes larger shift degree.    

10.  Effects of Substrate Temperature on Helium Content and Microstructure of Nanocrystalline Titanium Films  
   庞洪超 罗顺忠 龙兴贵 安竹 刘宁 段艳敏 吴兴春 杨本福 王培禄 郑思孝《中国物理快报》,2006年第23卷第12期
   Helium-charged nanocrystalline titanium films have been deposited by HeAr magnetron co-sputtering. The effects of substrate temperature on the helium content and microstructure of the nanocrystalline titanium films have been studied. The results indicate that helium atoms with a high concentration are evenly incorporated in the deposited titanium films. When the substrate temperature increases from 60℃ to 350℃ while the other deposition'parameters are fixed, the helium content decreases gradually from 38.6 at.% to 9.2at.%, which proves that nanocrystalline Ti films have a great helium storage capacity. The 20 angle of the Bragg peak of (002) crystal planes of the He-charged Ti film shifts to a lower angle and that of (100) crystal plane is unchanged as compared with that of the pure Ti film, which indicates that the lattice parameter c increases and a keeps at the primitive value. The grain refining and helium damage result in the diffraction peak broadening.    

11.  Study of local environment of Cu atoms in Fe73.5Cu1Nb3Si13.5B9 alloy with different annealing temperature  
   ZHANG Yu  YANG Ying  WANG YuXin  LU Wei  YAN Biao《中国科学:物理学 力学 天文学(英文版)》,2013年第56卷第10期
   The local environment of Cu atoms in Fe73.5Cu1Nb3Si13.5B9 alloy was investigated by extended X-ray absorption fine structure(EXAFS).Cu clusters began to order when the annealing temperature was around 733 K from the results of the Fourier transform curves.The fitting results showed that the first shell of the near fcc(face-centered cubic)Cu clusters only contained Cu atoms.The coordination number increased with the annealing temperature.Subsequently,the occupancy rate increased from 33.3%(annealed at 733 K)to 100% (annealed at 853 K).This local structural change of Cu atoms could probably affect the distribution of the bcc(body-centered cubic)α-Fe in Fe73.5Cu1Nb3Si13.5B9 alloy.    

12.  Effect of vacancy defect clusters on the optical property of the aluminium filter used for the space solar telescope  
   程秀围  关庆丰  范鲜红  陈波《中国物理 B》,2010年第19卷第1期
   We investigate the microstructures of the pure aluminium foil and filter used on the space solar telescope, irradiated by photons with different doses. The vacancy defect clusters induced by proton irradiation in both samples are characterized by transmission electron microscopy, and the density and the size distribution of vacancy defect clusters are determined. Their transmittances are measured before and after irradiating the samples by protons with energy E = 100 keV and dose = 6 × 10 11 /mm 2 . Our experimental results show that the density and the size of vacancy defect clusters increase with the increase of irradiation doses in the irradiated pure aluminium foils. As irradiation dose increases, vacancies incline to form larger defect clusters. In the irradiated filter, a large number of banded void defects are observed at the agglomerate boundary, which results in the degradation of the optical and mechanical performances of the filter after proton irradiation.    

13.  Deuterium cluster jet produced at moderate backing pressures  
   Hongbin Wang  Fangfang Ge  Hongjie Liu  Guoquan Ni  Xiangdong Yang  Yuqiu Gu  Xianlun Wen  Weimin Zhou  Guangchang Wang  Tianshu Wen  Yingling He  Chunye Jiao  Shuanggen Zhang  Xiangxian Wang《中国光学快报(英文版)》,2006年第4卷第5期
   A deuterium cluster jet produced in the supersonic expansion into vacuum of deuterium gas at liquid nitrogen temperature and moderate backing pressures are studied by Rayleigh scattering techniques. The experimental results show that deuterium clusters can be created at moderate gas backing pressures ranging from 8 to 23 bar, and a maximum average cluster size of 350 atoms per cluster is estimated. The temporal evolution of the cluster jet generated at the backing pressure of 20 bar demonstrates a two-plateau structure. The possible mechanism responsible for this structure is discussed. The former plateau with higher average atom and cluster densities is more suitable for the general laser-cluster interaction experiments.    

14.  Deuterium cluster jet produced at moderate backing pressures  
   王红斌  葛芳芳  刘红杰  倪国权  杨向东  谷渝秋  温贤伦  周维民  王光昶  温天舒  何颖玲  焦春晔  张双根  王向贤《中国光学快报(英文版)》,2006年第5期
   A deuterium cluster jet produced in the supersonic expansion into vacuum of deuterium gas at liquid nitrogen temperature and moderate backing pressures are studied by Rayleigh scattering techniques. The experimental results show that deuterium clusters can be created at moderate gas backing pressures ranging from 8 to 23 bar, and a maximum average cluster size of 350 atoms per cluster is estimated. The temporal evolution of the cluster jet generated at the backing pressure of 20 bar demonstrates a two-plateau structure. The possible mechanism responsible for this structure is discussed. The former plateau with higher average atom and cluster densities is more suitable for the general laser-cluster interaction experiments.    

15.  Calculation of Quark-Number Susceptibility at Finite Chemical Potential and Temperature  
   曹京  赵阿蒙  罗柳军  孙为民  宗红石《中国物理快报》,2010年第3期
   We use the direct method proposed by He et al. [Phys. Lett. B 680 (2009) 432) to calculate the quark-number susceptibility (QNS) at finite temperature and the chemical potential in the quasi-particle model. In our approach the QNS is given by a formula solely involving the dressed quark propagator at finite chemical potential μ and temperature Τ. The QNS at finite μ and Τ is calculated in the quasi-particle model. It is found that at high temperatures the QNS tends to the ideal quark gas result. At very small temperatures the QNS vanishes. This vanishing behavior in the low-temperature region is consistent with the lattice results. For μ∈ [0,180] MeV, our results show that there exists a rapid increase of QNS near some temperatures. The temperature at which the rapid increase occurs shifts to smaller values with the increasing quark chemical potential. This rapid increase could be regarded as a signal of a crossover.    

16.  Coherence-enhanced entanglement between two atoms at high temperature  
   胡要花  方卯发  姜春蕾  曾 可《中国物理 B》,2008年第17卷第5期
   This paper studies the entanglement properties in a system of two dipole-dipole coupled two-level atoms resonantly interacting with a single-mode thermal field. The results show that, when the temperature of the cavity is high enough (corresponding to the large value of the mean photon number), the entanglement is greatly enhanced due to the initial atomic coherence. These results are helpful for controlling the atomic entanglement by changing the initial parameters of the system.    

17.  Characteristics of wall sheath and secondary electron emission under different electron temperatures in a Hall thruster  
   段萍  覃海娟  周新维  曹安宁  陈龙  高宏《中国物理 B》,2014年第7期
   In this paper, a two-dimensional physical model is established in a Hall thruster sheath region to investigate the influences of the electron temperature and the propellant on the sheath potential drop and the secondary electron emission in the Hall thruster, by the particle-in-cell(PIC) method. The numerical results show that when the electron temperature is relatively low, the change of sheath potential drop is relatively large, the surface potential maintains a stable value and the stability of the sheath is good. When the electron temperature is relatively high, the surface potential maintains a persistent oscillation, and the stability of the sheath reduces. As the electron temperature increases, the secondary electron emission coefficient on the wall increases. For three kinds of propellants(Ar, Kr, and Xe), as the ion mass increases the sheath potentials and the secondary electron emission coefficients reduce in sequence.    

18.  Feasibility analysis of junction temperature measurement for GaN-based high-power white LEDs by the peak-shift method  
   张晶晶  张涛  刘石神  袁士东  金亚方  杨盛《中国光学快报(英文版)》,2013年第10期
   Transient thermal impedance of GaN-based high-power white light emitting diodes (LEDs) is created using a thermal transient tester. An electro-thermal simulation shows that LED junction temperature (JT) rises to a very low degree under low duty cycle pulsed current. At the same JT, emission peaks are equivalent at pulsed and continuous currents. Moreover, the difference in peak wavelength when a LED is driven by pulsed and continuous currents initially decreases then increases with increasing pulse width. Thus, selecting an appropriate pulse width decreases errors in JT measurement.    

19.  Vacancy in 6H—Silicon Carbide Studied by Slow Positron Beam  
   王海云 翁惠民 杭德生 周先意 叶邦角 范扬眉 韩荣典 C.C.Ling Y.P.Hui《中国物理快报》,2003年第20卷第7期
   The defect changes in 6H-SiC after annealing and 10MeV electron irradiation have been studied by using a variable-energy positron beam.It was found that after annealing,the defect concentration in n-type 6H-SiC decreased due to recombination with interstitials.When the sample was annealed at 1400℃ for 30 min in vacuum,a 20-nm thickness Si layer was found on the top of the SiC substrate,this is a direct proof of the Si atoms diffusing to surface when annealed at high temperature stages.After 10MeV electron irradiation,for n-type 6H-SiC,the S parameter increased from 0.4739 to 0.4822,and the relative positron-trapping rate was about 27.878 times of the origin sample,this shows that there are some defects created in n-type 6H-SiC.For p-type 6H-SiC,it is very unclear,this may be because of the opposite charge of vacancy defects.    

20.  HYDROFORMYLATION OF 1-HEXENE WITH Rh_4(CO)_(12) AND [Rh(CO)_2Cl]_2  
   《分子催化》,1989年第Z1期
   The hydroformylation of hexene-1 catalyzed by Rh_4 (CO)_12 and 〔Rh(CO)_2Cl〕_2 andthe effects of solvents (benzene, n-heptane and THF) and PPh_3 on the activity andselectivity of the catalysts were studied.The results indicated that the activity of Rh_4(CO)_(12) decreased with increasing solventpolarity and it did not change appreciably with addition of PPh_3 when the molar ratioPPh_3/Rh_4(CO)_(12)≤4. Thc activity of Rh_4(CO)_(12) was over twice as large as that of〔Rh(CO)_2Cl〕_2 when calculated according to the number of moles of rhodium clusters inbenzene without PPh_3, but the activities of both Rh_4(CO)_(12) and 〔Rh(CO)_2Cl〕_2 wereabout the same when calculated according to the number of rhodium atoms. It is suggestedthat the clusters probably dissociated into the similar active rhodium mononuclear speciesunder the reaction conditions and the species formed a cluster similar to Rh_4(CO)_(12) againwhen the conditions were reduced to the ambient temperature and pressure.    

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号