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11.
K. Nordlund C. BjörkasK. Vörtler A. MeinanderA. Lasa M. MehineA.V. Krasheninnikov 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(11):1257-1261
Current and future tokamak-like fusion reactors include the three elements Be, C, and W as the plasma-facing materials. During reactor operation, also mixtures of all these elements will form. Hence it is important to understand the atom-level mechanisms of physical and chemical sputtering in these materials. We have previously shown that athermal low-energy sputtering of pure C and Be can be understood by the swift chemical sputtering mechanism, where an incoming H (or D or T) ion enters between two atoms and pushes them apart. In the current article, we examine the model system of D impacting on a single dimer to determine the detailed mechanism of bond breaking and its probability for the Be2, C2, W2, WC, BeW, and BeC dimers. The results are found to correlate well with recent experiments and simulations of sputtering of the corresponding bulk materials during prolonged H isotope bombardment. 相似文献
12.
Prior studies highlight consumer behavior in social commerce from the perspective of relational exchange, while culture-driven aspects have been neglected. Given cultural uniqueness in China, this study develops a research model to explore the effects of key social commerce affordances on swift guanxi dimensions and subsequent purchase intention. Data from 450 agricultural product consumers in social commerce were used in PLS analysis for testing the proposed research model. The results indicate that interactivity, stickiness, and word of mouth exert positive effects on mutual understanding, reciprocal favor, and relationship harmony, to various degrees. In turn, swift guanxi dimensions are determinants of consumers’ purchase intention in social commerce. 相似文献
13.
14.
We report the use of swift heavy ion irradiation as a means to tailor the luminescence properties of bismuth doped barium sulphide nanostructures. The samples were irradiated with 120 MeV Ni+9 ions at three different fluences of 1 × 1012, 5 × 1012, and 1 × 1013 ion/cm2. Structural and optical properties of pristine and irradiated samples were carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence (PL) and UV-vis spectroscopy. X-ray diffraction (XRD) studies were used to estimate the average size of nanoparticles. The average size of the crystallites is estimated from the line widths of the diffraction pattern, while the exact size of the crystallites is estimated from the TEM micrographs. After irradiation with a fluence of 1 × 1013 ion/m2 the photoluminescence intensity increases by 42%. The indirect band gap of BaS:Bi is increased after ion irradiation. 相似文献
15.
The relationship between the yield ratio and the material constants,b andN, of the Swift equation for hotrolled low carbon steels has been established. The yield ratio calculated by using the Swift
equation agrees well with an experimentally obtained yield ratio. It was found that the yield ratio decreases with an increasing
value ofN or with a decreasing value ofb. It was also found, however, that high yield strength is associated with small values of bothb andN. Therefore, to obtain both high yield strength and low yield ratio, a detailed microstructural control is needed to determine
the optimum values ofb andN. 相似文献
16.
Large strain homogeneous simple shear of Hexagonal Close Packed (HCP) polycrystals is first studied numerically. The analyses are based on the classical Taylor model and the Visco-Plastic Self-Consistent (VPSC) model with various Self-Consistent Schemes (SCSs). In these polycrystal plasticity models, both slip and twinning contribute to plastic deformations. The simple shear results are then extended to the case of solid circular bars under large strain fixed-end torsion, where it is assumed that the solid bar has the same mechanical properties as the element analyzed for large strain simple shear. It is shown that the predicted second-order axial force is very sensitive to the initial texture, texture evolution and the constitutive models employed. Numerical results suggest that the torsion test can provide an effective means for assessing the adequacy of polycrystal plasticity models for HCP polycrystalline materials. 相似文献
17.
M.-C. Clochard T. Berthelot C. Baudin N. Betz E. Balanzat G. Gbel A. Morin 《Journal of power sources》2010,195(1):223-231
Proton conductive individual channels through a poly(vinyl di-fluoride) PVDF matrix have been designed using the ion track grafting technique. The styrene molecules were radiografted and further sulfonated leading to sulfonated polystyrene (PSSA) domains within PVDF. The grafting process all along the cylindrical ion tracks creates after functionalisation privileged paths perpendicular to the membrane plane for proton conduction from the anode to the cathode when used in fuel cells. Such ion track grafted PVDF-g-PSSA membranes have low gas permeation properties against H2 and O2. A degree of grafting (Yw) of 140% was chosen to ensure a perfect coverage of PSSA onto PVDF-g-PSSA surface minimizing interfacial ohmic losses with the active layers of the Membrane Electrolyte Assembly (MEA). A three-day fuel cell test has been performed feeding the cell with pure H2 and O2, at the anode and cathode side respectively. Temperature has been progressively increased from 50 to 80 °C. Polarisation curves and Electrochemical Impedance Spectroscopy (EIS) at different current densities were used to evaluate the MEA performance. From these last measurements, it has been possible to determine the resistance of the MEA during the fuel cell tests and, thus the membrane conductivity. The proton conductivities of such membranes estimated during fuel cell tests range from 50 mS cm−1 to 80 mS cm−1 depending on the operating conditions. These values are close to that of perfluorosulfonated membrane such as Nafion® in similar conditions. 相似文献
18.
A. Meftah W. AssmannN. Khalfaoui J.P. StoquertF. Studer M. ToulemondeC. Trautmann K.-O. Voss 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(9):955-958
The results of present paper have shown that sputtering of yttrium iron garnet (Y3Fe5O12) under swift heavy ions in the electronic energy loss regime is non-stoichiometric. Here we are presenting additional experimental results for gadolinium gallium garnet (Gd3Ga5O12) as target. The irradiations were performed with different ions (50Cr (589 MeV), 86Kr (195 MeV) and 181Ta (400 MeV)) impinging perpendicularly to the surface. As earlier, the sputtering yield was determined by collecting the emitted gadolinium and gallium atoms on a thin aluminium foil, placed upstream above the target and analyzing the Al catcher by Rutherford backscattering. Also for Gd3Ga5O12, the emission of Gd and Ga is non-stoichiometric. Sputtering appears above a critical electronic stopping power of Sth = 11.6 ± 1.5 keV/nm, which is larger than the threshold for track formation, in agreement with other amorphisable materials. In addition, the angular distribution of the sputtered species was measured for Y3Fe5O12 and Gd3Ga5O12 using 200 MeV Au ions impinging the surface at 20° relatively to the surface. For the two garnets the ratio of Y/Fe (and Gd/Ga) varies with the angle of emitted species and the stoichiometry seems to be preserved only for an emission perpendicular to the surface. 相似文献
19.
Yoshinobu Wakamatsu Hideaki YamadaSatoshi Ninomiya Brian N. JonesToshio Seki Takaaki Aoki Roger WebbJiro Matsuo 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2011,269(20):2251-2253
Various imaging techniques using microbeam have been applied in biology. Secondary ion mass spectrometry (SIMS) is one of the prominent tools for biological imaging; SIMS can provide data on molecular distribution in biological samples smaller than 1 μm. However, conventional SIMS has only low sensitivity for molecular ions; therefore there is a need for beams of more sensitive primary ions. Plasma desorption mass spectrometry (PDMS) is a method using high energy fission fragments from excitation of a 252Cf source, and it allows ionization of large molecules (typically up to 20 kDa) due to the dense electronic excitation. Although PDMS is not in use today because of the development of soft ionization methods, ionization induced by high energy ion collision still remains the only method which combines high spatial resolution and sensitive detection of large molecules. In this work, the secondary ion yield of amino acid and phospholipid was measured for 6 MeV Cu4+. The yields were compared to bismuth cluster ions, which achieve relatively high yield. It was confirmed that the swift heavy ion has a couple of hundred times higher yield for large molecules than bismuth cluster ions. 相似文献
20.
The radiation damage effect on the friction coefficient, wear, and microhardness of the alloy Ti-6Al-4V after 250 MeV krypton ion irradiation was studied. Tribological measurements were made in air, oxygen, and argon atmospheres and in a vacuum. The smallest friction coefficient for the irradiated samples occurred in argon and the vacuum. The wear of the unirradiated samples and those irradiated with low fluences (<1013 cm−2) increased in the vacuum and argon atmosphere. Wear was significantly reduced after irradiation with the fluence of 1014 cm−2. The microhardness of the alloy Ti-6Al-4V increased by over 25% after irradiation with a large fluence. 相似文献