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91.
92.
Shasha Lv Rui Zhu Yuanhua Shen Qin Zhou Li Shi Libin Sun Xinxin Wu Zhengcao Li 《Surface and interface analysis : SIA》2022,54(9):954-962
Nickel-base alloys have been selected as a potential metallic material for reactor internals in Generation IV reactors. In order to evaluate their helium embrittlement resistance, microstrain changes and evolution of vacancy-type defects after Helium irradiation and postimplantation annealing have been studied by grazing incidence X-ray diffraction (GIXRD) and slow positron doppler broadening spectroscopy (PDB). GIXRD results show that the increase in microstrain after helium irradiation is more pronounced at high doses. The observed S parameters of PDB increase with the irradiation doses, which indicates a significant number of vacancy-type defects, possibly helium-vacancy clusters. For postimplantation annealing specimens, the microstrain characterized by GIXRD has recovered. The surprise is the S parameters that significantly increase, revealing that helium atoms trapped at unstable helium-vacancy clusters desorb during annealing, contributing to the growth of helium bubbles. These findings of microstrain mechanisms and vacancy-type defects behaviors give us new insights into the helium irradiation evaluation. 相似文献
93.
Single‐crystal X‐ray diffraction and resonant X‐ray magnetic scattering at helium‐3 temperatures in high magnetic fields at beamline P09 at PETRA III 下载免费PDF全文
S. Francoual J. Strempfer J. Warren Y. Liu A. Skaugen S. Poli J. Blume F. Wolff‐Fabris P. C. Canfield T. Lograsso 《Journal of synchrotron radiation》2015,22(5):1207-1214
The resonant scattering and diffraction beamline P09 at PETRA III at DESY is equipped with a 14 T vertical field split‐pair magnet. A helium‐3 refrigerator is available that can be fitted inside the magnet's variable‐temperature insert. Here the results of a series of experiments aimed at determining the beam conditions permitting operations with the He‐3 insert are presented. By measuring the tetragonal‐to‐orthorhombic phase transition occurring at 2.1 K in the Jahn–Teller compound TmVO4, it is found that the photon flux at P09 must be attenuated down to 1.5 × 109 photons s?1 for the sample to remain at temperatures below 800 mK. Despite such a reduction of the incident flux and the subsequent use of a Cu(111) analyzer, the resonant X‐ray magnetic scattering signal at the Tm LIII absorption edge associated with the spin‐density wave in TmNi2B2C below 1.5 K is intense enough to permit a complete study in magnetic field and at sub‐Kelvin temperatures to be carried out. 相似文献
94.
为获得高温气冷堆核电站电气设备绝缘设计所需基础数据, 本文设计了一套测量高压氦气绝缘性能的装置. 利用该装置进行了15-20 ℃, 0.1-7 MPa氦气, 间距0.25, 0.35, 0.5 mm平行极板击穿实验. 实验表明: 氦气的绝缘性能远低于空气; 气压越高, 氦气的击穿电压越大, 3.0 MPa氦气的击穿电压与常压空气基本一致; 根据低气压实验数据和巴申定律推导的公式, 在高气压下计算值偏大, 且偏差随着气压和间距乘积的增大不断增大; 提出了可计算0.1-7 MPa氦气击穿电压的简易公式, 同时修正了高气压氦气的巴申公式, 并进行了理论分析. 相似文献
95.
Maria Giordani Dr. Paola Antoniotti Dr. Felice Grandinetti Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(21):6257-6264
Ab initio calculations at the MP2 and CCSD(T) levels of theory have disclosed the conceivable existence of fluorine‐coordinated complexes of HHeF with alkali‐metal ions and molecules M+ (M+=Li+–Cs+), M+–OH2, M+–NH3 (M+=Li+, Na+), and MX (M=Li, Na; X=F, Cl, Br). All these ligands L induce a shortening of the H? He distance and a lengthening of the He? F distance accompanied by consistent blue‐ and redshifts, respectively, of the H? He and He? F stretching modes. These structural effects are qualitatively similar to those predicted for other investigated complexes of the noble gas hydrides HNgY, but are quantitatively more pronounced. For example, the blueshifts of the H? He stretching mode are exceptionally large, ranging between around 750 and 1000 cm?1. The interactions of HHeF with the ligands investigated herein also enhance the (HHe)+F? dipole character and produce large complexation energies of around 20–60 kcal mol?1. Most of the HHeF–L complexes are indeed so stable that the three‐body dissociation of HHeF into H+He+F, exothermic by around 25–30 kcal mol?1, becomes endothermic. This effect is, however, accompanied by a strong decrease in the H? He? F bending barrier. The complexation energies, ΔE, and the bending barriers, E*, are, in particular, related by the inverse relationship E*(kcal mol?1)=6.9exp[?0.041ΔE(kcal mol?1)]. Therefore the HHeF? L complexes, which are definitely stable with respect to H+He+F+L (ΔE≈25–30 kcal mol?1), are predicted to have bending barriers of only 0.5–2 kcal mol?1. Overall, our calculations cast doubt on the conceivable stabilization of HHeF by complexation. 相似文献
96.
The Role of Dielectric Barrier Discharge Atmosphere and Physics on Polypropylene Surface Treatment 总被引:8,自引:0,他引:8
Dielectric barrier discharge (DBD) is the discharge involved in corona treatment, widely used in industry to increase the wettability or the adhesion of polymer films or fibers. Usually DBD's are filamentary discharges but recently a homogeneous glow DBD has been obtained. The aim of this paper is to compare polypropylene surface transformations realized with filamentary and glow DBD in different atmospheres (He, N2, N2 + O2 mixtures) and to determine the relative influence of both the discharge regime and the gas nature, on the polypropylene surface transformations. From wettability and XPS results it is shown that the discharge regime can have a significant effect on the surface transformations, because it changes both the ratio of electrons to gas metastables, and the space distribution of the plasma active species. This last parameter is important at atmospheric pressure because the mean free paths are short (m). These two points explain why in He, polypropylene wettability increase is greater by a glow DBD than by a filamentary DBD. In N2, no significant effect of the discharge regime is observed because electrons and metastables lead to the same active species throughout the gas bulk. The specificity of a DBD in N2 atmosphere compared to an atmosphere containing oxygen is that it allows very extensive surface transformations and a greater increase of the polypropylene surface wettability. Indeed, even in low concentration and independently of the discharge regime, when O2 is present in the plasma gas, it controls the surface chemistry and degradation occurs. 相似文献
97.
Franziska Traeger 《Chemphyschem》2006,7(5):1006-1013
Many experimental methods of surface science employ electrons or photons of considerable incident energy as probe particles. However, insulating surfaces or delicate physisorbed layers may be damaged by these particles and should, therefore, be analyzed with a gentler probe: He atom scattering allows to determine the symmetry of the unit cell and the detection of phase transitions from diffraction measurements as well as the determination of surface and adsorbate vibrations by time-of-flight resolved detection. Herein, the application of He atom scattering to oxide surfaces is demonstrated on the basis of the examples of MgO and ZnO. MgO(001) is a very inert and stable surface, whereas hydrogen atoms are chemisorbed on the mixed-terminated ZnO(1010) and on both polar faces: ZnO(0001) and ZnO(0001). He atom scattering is very sensitive to the presence of hydrogen on surfaces. In addition ZnO reacts with molecules such as water, CO and CO(2). It is demonstrated that in combination with photoelectron spectroscopy and thermal desorption spectroscopy He atom scattering can also contribute to studies of surface chemistry. 相似文献
98.
F. Arias de Saavedra E. Buendía F. J. Gálvez A. Sarsa 《International journal of quantum chemistry》2000,79(2):75-81
For an A-particle quantum system in a state Ψ, the movement of any pair of particles is studied. Using the corresponding two-body densities, the effective potential that determines the relative and center of mass movements of the pair of particles is built. Some aspects of the proposed general procedure are applied to different, functions used to describe the ground state of the helium atom. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 79: 75–81, 2000 相似文献
99.
I. Porras D. Matthew Feldmann Frederick W. King 《International journal of quantum chemistry》1999,71(6):455-463
Lower‐bound estimates for the ground‐state energy of the helium atom are determined using nonlinear programming techniques. Optimized lower bounds are determined for single‐particle, radially correlated, and general correlated wave functions. The local nature of the method employed makes it a very severe test of the accuracy of the wave function. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 71: 455–463, 1999 相似文献
100.
A highly sensitive and specific method is described for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and environmental samples by gas chromatography–plasma atomic emission detection (GC–AED). The procedure is simple, rapid and free from interferences. The absolute limit of detection is 0.5 fg of MMT (0.5×10−15 g) expressed as Mn. The precision for replicate injections ( n =5) of an MMT solution (10 pg Mn) was 2.8% relative standard deviation (RSD ). Applications of the method to analysis of gasoline (petrol), and preliminary results of the analyses of environmental samples such as air and roadside dirt, are given. © 1997 by John Wiley & Sons, Ltd. 相似文献