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1.
《Surface science》1986,175(3):508-519
Ni, Cu, Ag and Au on W(110) in the submonolayer range are studied by thermal desorption spectroscopy with the goal of obtaining information on lateral interactions and on the phase state of the adsorption layer in the temperature range in which desorption occurs. Ni, Cu and Ag are found to desorb over a wide coverage range from the two-phase (vapor-condensate) region while Au desorbs only from the single-phase vapor region. Segments of the coexistence curve are determined. The desorption energies have the following limiting values: 4.35–4.95. 3.2–3.85, 2.8–3.55 and 3.3–4.1 eV for Ni, Cu, Ag and Au, respectively. 相似文献
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A. Harder S. Michaelsen K. P. Lieb A. P. Williams 《Zeitschrift für Physik A Hadrons and Nuclei》1993,345(2):143-153
Theγ-radiation emitted after thermal neutron capture in isotopically enriched58Ni and60Ni was measured at the ILL high flux reactor by means of Ge/NaI detectors operated in Compton suppression and pair spectrometer mode. The neutron binding energies were determined asB n (59Ni)=8999.15(23) keV and Bn(61Ni)=7820.07(20) keV; some 95% of the totalγ-ray fluxes through59,61Ni were assigned. Theγ-ray strength functions of the primary transitions and the level densities are discussed. 相似文献
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C. Kusch N. Krawez R. Tellgmann B. Winter E.E.B. Campbell 《Applied Physics A: Materials Science & Processing》1998,66(3):293-298
60 and produced by low-energy ion bombardment. The desorption properties of the films were studied as a function of the film
thickness, ion energy, and ion dose. The results provide strong corroborative evidence for the endohedral nature of the Li-containing
species and also clearly indicate the prescence of Li2@C60 in the films. The binding energy in these films is significantly larger than in pure C60 films and evidence of degradation of the fullerenes is seen at high ion energies and/or large ion doses.
Received: 6 August 1997/Accepted: 8 August 1997 相似文献
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在中子与58Ni反应的总截面、去弹性散射截面和弹性散射角分布的实验数据基础上, 获得了入射中子能量从0.825—150MeV的一组普适的中子与58Ni反应的光学模型势参数. 利用光学模型、宽度涨落修正的Hauser-Feshbach理论、预平衡反应的激子模型和核内级联模型的中能核反应计算程序MEND, 计算了中子与58Ni反应的所有截面、角分布和能谱, 并将理论计算结果与实验数据和评价数据进行了分析比较. 相似文献
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Th. Desaive M. Hennenberg G. Lebon 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(4):641-647
In this work, we study the problem of onset of thermal convection in a rotating saturated porous medium heated from below.
The effect of rotation is restricted to the Coriolis force, neglecting thus the centrifugal effects, the porous medium is
described by Brinkman's model. The linear eigenvalue problem is solved by means of a modified Galerkin method. The behavior
of the critical temperature gradient is discussed in terms of various parameters of the system for both stationary and overstable
convections. Finally a weakly nonlinear analysis is provided to derive amplitude equations and to study the onset of Küppers-Lortz
instability.
Received 24 June 2002 / Received in final form 11 September 2002 Published online 31 October 2002
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ID="a"e-mail: tdesaive@ulg.ac.be 相似文献
7.
采用真空热压技术在高真空和温度为523K的情况下,通过不同压力将直径平均大约为45nm的Cu纳米粉末压制成纳米结构Cu固体材料,将X射线衍射、扫描电镜与物性测试仪(PPMS)相结合,研究了低温下纳米结构Cu固体材料的比热容随温度和材料密度的变化.研究结果表明:低温比热容随着纳米结构Cu固体材料密度的降低而升高;纳米结构Cu固体材料的低温比热容大于粗晶Cu,其增加率在10K左右达到极大.基于缺陷的热振动效应,探讨了这些现象的物理机理. 相似文献
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The mechanical properties of amorphous solids like metallic glasses can be dramatically changed by adding small concentrations (as low as 0.1%) of foreign elements. The glass-forming-ability, the ductility, the yield stress and the elastic moduli can all be greatly effected. This paper presents theoretical considerations with the aim of explaining the magnitude of these changes in light of the small concentrations involved. The theory is built around the experimental evidence that the microalloying elements organise around them a neighbourhood that differs from both the crystalline and the glassy phases of the material in the absence of the additional elements. These regions act as isotropic defects that in unstressed systems modify the shear moduli. When strained, these defects interact with the incipient plastic responses which are quadrupolar in nature. It will be shown that this interaction interferes with the creation of system-spanning shear bands and increases the yield strain. We offer experimentally testable estimates of the lengths of nano-shear bands in the presence of the additional elements. 相似文献
11.
Comparison of formation and evolution of radiation-induced defects in pure Ni and Ni-Co-Fe medium-entropy alloy
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High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have attracted a great deal of attention for developing nuclear materials because of their excellent irradiation tolerance. Herein, formation and evolution of radiation-induced defects in NiCoFe MEA and pure Ni are investigated and compared using molecular dynamics simulation. It is observed that the defect recombination rate of ternary NiCoFe MEA is higher than that of pure Ni, which is mainly because, in the process of cascade collision, the energy dissipated through atom displacement decreases with increasing the chemical disorder. Consequently, the heat peak phase lasts longer, and the recombination time of the radiation defects (interstitial atoms and vacancies) is likewise longer, with fewer deleterious defects. Moreover, by studying the formation and evolution of dislocation loops in Ni-Co-Fe alloys and Ni, it is found that the stacking fault energy in Ni-Co-Fe decreases as the elemental composition increases, facilitating the formation of ideal stacking fault tetrahedron structures. Hence, these findings shed new light on studying the formation and evolution of radiation-induced defects in MEAs. 相似文献
12.
Tokiyoshi Matsuda Mamoru Furuta Takahiro Hiramatsu Hiroshi Furuta Chaoyang Li Takashi Hirao 《Applied Surface Science》2010,256(21):6350-2485
Thermal stability of sputter deposited ZnO thin films was evaluated by thermal desorption spectroscopy (TDS). Desorption of Zn was mainly observed from the films deposited at low O2/Ar gas ratio and low RF power. In contrast, O2 desorption was mainly observed from the films deposited at high O2/Ar gas ratio and high RF power. The amount of desorbed O2 from the film increased with increasing the O2/Ar gas flow ratio and the RF power. Furthermore, the desorption temperature of O2 increased with increasing the RF power during the deposition. Thermal stability of the ZnO films was controlled not only by the O2/Ar gas flow ratio, but also applied RF power to the target. 相似文献
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The temperature dependences of the thermal conductivity of planar and nanotubular supracrystalline structures have been calculated at temperatures below the Debye temperature using the Landauer approach for the ballistic conductance of one-dimensional conductors. The mathematical model based on this approach has been examined on carbon nanotubes and graphene. 相似文献
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John C. Tully 《Surface science》1981,111(3):461-478
Three-dimensional stochastic classical trajectory studies have been carried out of the thermal desorption of isolated Ar and Xe atoms from the (111) face of platinum. Realistic interaction potentials that produce quantitative agreement with experimental sticking probabilities and angular and velocity scattering distributions were employed. Energy exchange with lattice phonons was included accurately via empirically chosen friction and fluctuating forces. Application of techniques for the simulation of “infrequent events” allowed studies to be extended to experimentally accessible lifetimes. Atoms were found to desorb preferentially to wide angles, with mean energy considerably lower than 2k times the surface temperature. Significant curvature of the Arrhenius plots was exhibited, and pre-exponential factors were found to be lower than characteristic frequencies. These effects were determined to be mainly dynamical in origin; i.e., they cannot be described by conventional transition-state-theory models. 相似文献
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Predictions are given on stability conditions for experiments in standard and reduced-gravity conditions when the Soret effect is operating in a horizontal binary liquid layer heated from below and open to the ambient air. 相似文献
17.
Thermal desorption spectroscopy (TDS) has been used to study the chemisorption of CO, O2, and h2 on Pt. It has been found that TDS is quite sensitive to local surface structure. Three single crystal and two polycrystalline Pt surfaces were studied. One single crystal was cut to expose the smooth, hexagonally close-packed plane of the fee Pt crystal (the (111) surface). The other two single crystals were cut to expose stepped surfaces consisting of smooth, hexagonally close-packed terraces six atoms wide separated by one atom high steps (the 6(111) × (100) and 6(111) × (111) surfaces). Only one predominant desorption state was observed for CO and H adsorbed on the smooth (111) single crystal surface, while two predominant desorption states were observed for these gases adsorbed on the stepped single crystal surfaces. The low temperature desorption states on the stepped surfaces are attributed to desorption from the terraces, while the high temperature desorption states are attributed to desorption from the steps. TDS of CO from the polycrystalline foils exhibited some desorption states which were similar to those observed on the stepped single crystal surfaces, indicating the presence of adsorption sites on the polycrystalline foils that were similar to the terrace and step sites on the stepped single crystals. In general, these results suggest a high density of defect sites on the polycrystalline foils which can not be attributed simply to adsorption at grain boundaries. Oxygen was found to adsorb well on the stepped single crystals and on the polycrystalline foils, but not on the smooth (111) single crystal, under the conditions of these experiments. This is attributed to a higher sticking probability for dissociative O2 adsorption at steps or defects than on terraces. 相似文献
18.
Positron lifetime spectra have been measured at 77 K for KCl and Ag-doped KCl before and after x-irradiation at 77 K and after
annealing at room temperature. Radiation at 77 K reduces the intensity of the intermediate lifetime (τ2) component. Radiation-induced defects were monitored optically and by ESR. The experiment shows that the changes observed
in the positron decay are associated with the presence ofV
K centers.
Work support in part by the Research Corporation.
Paper C1 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973). 相似文献
19.
V. V. Apanasovich E. G. Novikov N. N. Yatskov R. B. M. Koehorst T. J. Schaafsma A. van Hoek 《Journal of Applied Spectroscopy》1999,66(4):613-616
Results of investigation of the optical properties of zinc complexes of mesotetraphenylporphyrin and monopyridyltriphenylporphyrin
in impurity-free organic solvent are presented. Analyses of absorption and emission spectra and fluoresence decay kinetics
in terms of both a sum of exponentials and using simulation of energy-transformation processes in a tetramer-type Zn-porphyrin
complex compound are carried out.
Reported at the VIIIth International Conference on Spectroscopy of Porphyrins and Their Analogs, Minsk, September 22–26, 1998.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 4, pp. 549–552, July–August, 1999. 相似文献
20.
H. Hinzert K. K. Kleinherbers E. Janssen A. Goldmann 《Applied Physics A: Materials Science & Processing》1989,49(3):313-320
Conflicting thermal desorption (TDS) results from submonolayer coverages of atomic Cl, Br or I on Ag(100), Ag(110) or Ag(111) stimulated us to check for the possible influence of different sample preparation procedures. We present experimental evidence, that a combined approach using TDS and angle-resolved ultraviolet photoemission may help to distinguish between better and worse surface preparation. We present detailed new results for the Cl/Ag(110) system. From our observations we conclude that all three halogens listed above give one and only one TDS peak in the submonolayer regime and show very similar adsorption/desorption-characteristics. This fact removes the apparent contradictions reported in the literature and demonstrates that the halogen-Ag bond is not very sensitive to the surface crystallography. 相似文献