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61.
The electronic states of the Cr overlayers on TiO2(0 0 1) surfaces have been investigated using angle-resolved and resonant photoemission spectroscopy with synchrotron radiation. At lower coverages, Cr deposition on TiO2(0 0 1) creates two well separated in-gap emissions due to the formation of surface Ti3+ (3d1) ions and Cr3+ (3d3) ions. At higher coverages, the in-gap emission is developed into the 2-peak-structure emission of Cr 3d character. The corresponding state is considered to be of metallic nature from the viewpoint of the high ability of oxygen adsorption, but has no Fermi edge, indicating a possibility of forming small Cr clusters on TiO2(0 0 1) at this stage. 相似文献
62.
汪巍 《数学的实践与认识》2004,34(3):103-109
首先引入了差分系统基于两种度量的极端稳定性概念 ,然后建立了一些关于差分系统 ( h0 ,h)极端稳定性 (极端一致稳定性 ,极端渐近稳定性 ,极端一致渐近稳定性 )的判定准则 .在所得到的定理中 ,对△ V的限制较弱 ,特别地 ,△V甚至可以恒为正 ,从而便于实际应用 . 相似文献
63.
The atomic structures of indium (In) on silicon (Si) (1 0 0)-(2 × 1) surface are investigated by the local density approximation using first-principles pseudopotentials. Total energy optimizations show that the energetically favored structure is the parallel ad-dimer model. The adsorption energy of In on ideal Si(1 0 0)-(1 × 1) surface is significantly higher than that on reconstructed Si(1 0 0)-(2 × 1) surface, suggesting that In adsorption does not break the Si-Si dimer bond of the substrate. When Si surface contains single dimer vacancy defects, In chain will be interrupted, leading to disconnected In nanowires. Displacive adsorption of In on Si(1 0 0) is also considered, and the calculation suggests that interdiffusion of In into Si substrate will not be favorable under equilibrium conditions. 相似文献
64.
Martin A. Bos Bertus Dunnewind Ton van Vliet 《Colloids and surfaces. B, Biointerfaces》2003,31(1-4):95-105
Interfacial rheological properties and their suitability for foam production and stability of two vegetable proteins were studied and compared to β-casein. Proteins used ranged from flexible to rigid/globular in the order of β-casein, gliadin and soy glycinin. Experiments were performed at pH 6.7. Network forming properties were characterised by the surface dilational modulus (determined with the ring trough) and the critical falling film length (Lstill) at which a stagnant protein film will break. Gliadin had the highest dilational modulus, followed by glycinin and β-casein, whereas glycinin formed the strongest film against fracture in the overflowing cylinder. The rate of decrease in the surface tension was studied at the air–water (Wilhelmy plate method) and the oil–water interface (bursting membrane) and the dynamic surface tension during compression and expansion in the caterpillar. Gliadin had the lowest equilibrium interfacial tensions and β-casein the lowest dynamic surface tension during expansion. Hardly any foam could be formed at a concentration of 0.1 g/l by shaking. At a concentration of 1.4 g/l most foam was formed by β-casein, followed by gliadin and glycinin. It seems that in the first place the rate of adsorption is important for foam formation. For the vegetable proteins, adsorption was slow. This resulted in lower foamability, especially for glycinin. 相似文献
65.
Microstructures of nickel surfaces electrodeposited on indium tin oxides coated glasses are investigated using atomic force microscopy. The fractal dimension D and Hurst exponent H of the nickel surface images are determined from a frequency analysis method proposed by Aguilar et al. [J. Microsc. 172 (1993) 233] and from Hurst rescaled range analysis. The two methods are found to give the same value of the fractal dimension D∼2.0. The roughness exponent α and growth exponent β that characterize scaling behaviors of the surface growth in electrodeposition are calculated using the height-difference correlation function and interface width in Fourier space. The exponents of α∼1.0 and β∼0.8 show that the surface growth does not belong to the universality classes theoretically predicted by statistical growth models. 相似文献
66.
B. V. Derjaguin 《Progress in Surface Science》1992,40(1-4):240-251
A review is presented about research on surface forces and surface interactions conducted over the past half-century, with some emphasis on the pioneering contributions of the Department of Surface Phenomena at the Institute of Physical Chemistry of the USSR Academy of Sciences. 相似文献
67.
Let Ω be a region in ℝn and letp = Pi )
i
1m
, be a partition ofΩ into a finite number of closed subsets having piecewise C2 boundaries of finite(n - 1 )dimensional measure. Let τ:Ω→Ω be piecewise C2 onP where, τi = τ|pi is aC
2 diffeomorphism onto its image, and expanding in the sense that there exists α > 1 such that for anyi = 1, 2,...,m ‖Dτi
-1 ‖ < α-1, where Dτi
-1 is the derivative matrixτ
i
- 1 and |‖·‖ is the Euclidean matrix norm. By means of an example, we will show that the simple bound of one-dimensional dynamics
cannot be generalized to higher dimensions. In fact, we will construct a piecewise expanding C2 transformation on a fixed partition with a finite number of elements in ℝ2, but which has an arbitrarily large number of ergodic, absolutely continuous invariant measures 相似文献
68.
Inhibition of the reduction of Cr(VI) at the magnetite–water interface by calcium carbonate coatings
The effect of calcium carbonate coatings on the reduction of aqueous chromate on the magnetite(1 1 1) surface has been investigated using a combination of synchrotron based X-ray photoemission spectroscopy (PES) and X-ray absorption near edge structure (XANES) spectroscopy, along with laboratory-based powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). CaCO3 coatings (dominantly calcite with minor quantities of aragonite and vaterite) of thicknesses ranging from 10 Å to 20 m were grown on magnetite(1 1 1) surfaces by exposure to supersaturated aqueous solutions followed by evaporation of the solution—a process that mimics pore-water evaporation in vadose zones leading to the formation of caliche and calcium carbonate coatings on mineral grains. Coating thicknesses were determined from attenuation of the Fe 2p photoemission signal by the carbonate coating. For coatings less than 15 Å thick, Cr 2p photoemission and Cr LII, LIII-edge XANES spectra show that chromate is reduced by the underlying magnetite surface; however, as the minimum coating thickness increases beyond 15 Å, the magnetite surface becomes passivated and further chromate reduction ceases. Our findings suggest that carbonate coatings on natural magnetite grains can significantly reduce or eliminate their ability to reduce Cr(VI), which is a toxic and highly mobile environmental contaminant. 相似文献
69.
In this paper we report the results of a morphological and structural investigation on film properties of a soluble polydiacetylene, the poly[1,6-bis(3,6-dihexadecyl-N-carbazolyl)-2,4-hexadiyne] (polyDCHD-HS). The red films of this polymer, prepared by standard spin-coating techniques, revealed absence of linear dichroism and birefringence in contrast with the ordered mesophases detected by powder X-ray studies. In order to interpret the optical behavior of this polymer, we performed AFM and SEM studies of polyDCHD-HS films spun on hydrophylic and hydrophobic glass substrates. We found the presence of surfaces organized in rod-like particles, more regularly oriented on the hydrophylic substrate. GIXRD studies, carried out on films sufficiently thick to allow the observation of the diffraction pattern, reveled the presence of a lamellar structure with a spacing of 3.22 nm. The low intensity of the diffraction peaks and the isotropic linear optical properties of the films show that the lamellar mesophases are not extended over large areas. These findings were compared with the data obtained from AFM and SEM studies on films of two other polydiacetylenes, the poly[1-(3,6-dihexadexyl-N-carbazolyl)-6-(N-carbazolyl)-2,4-hexadyine] (polya-DCHD) and the poly[1,6-bis(3,6-dipalmitoyl-N-carbazolyl)-2,4-hexadyine] (polyDPCHD), spun on hydrophylic glass substrate. The results confirmed the presence of nodular morphologies which seem to be a general characteristic of this class of materials. The particles organization appears instead related to the chemical nature of the substituents on the carbazolyl rings. 相似文献
70.
Brillouin spectroscopy was used to study elastic properties of the Si (1 1 1) decorated with Ni nanostructures deposited by nanospherical lithography. The height of the nickel nanostructure deposited was about 25 nm, while the area taken by the structure differed depending on the type of matrix used. It was found that the Ni nanostructures change the velocity of both bulk and surface phonons in the systems studied. This finding is in contradiction to the results concerning the surface phonons velocities in different media covered with a homogenous thin metal film, in which the effect was observed for films thicker than 70 nm. 相似文献