Wavy film flow down a vertical plate: Comparisons between the results of integral approaches and full-scale computations

This paper is devoted to a theoretical analysis of nonlinear two-dimensional waves using the Navier-Stokes equations in their full statement. Steady-state travelling wave regimes have been found and an analysis of their linear stability has been carried out. It is shown that the flow regimes obtained using the Navier-Stokes equations are qualitatively different from the solutions of Shkadov’s integral approach starting from some values of the Kapitza number. It is also found that the wave regimes of the Navier-Stokes equations have an internal vortex at moderate Reynolds numbers. The results obtained using “the regularized integral model” are in excellent agreement with the Navier-Stokes calculations for Re/Ka ≤2. Unlike the solutions found using an integral approach, it is shown that only a few types of nonlinear waves exist when the full Navier-Stokes equations are considered. The text was submitted by the author in English.     

Modelling of spreading process: effect from hydrogen bonds

Lubricant spreading on solid substrates has drawn considerable attention not only for the microscopic wetting theory but also for the dramatic application in head-disk interface of magnetic storage drive systems. Molecular dynamic simulation based on a coarse-grained bead-spring model has been used to study such a spreading process. The spreading profiles indicate that the hydrogen bonds among lubricant molecules and the hydrogen bonds between lubricant molecules and polar atoms of solid substrates will complicate the spreading process in a tremendous degree. The hydrogen bonds among lubricant molecules will strengthen the lubricant combination intensity, which may hinder most molecules from flowing down to the substrates and diffusing along the substrates. And the hydrogen bonds between lubricant molecules and polar atoms of solid substrates will confine the lubricant molecules around polar atoms, which may hinder the molecules from diffusing along the substrates and cause precursor film to vanish.     

Influence of reaction gas flows on the properties of SiGe:H thin film prepared by plasma assisted reactive thermal chemical vapour deposition

A new preparing technology, very high frequency plasma assisted reactive thermal chemical vapour deposition （VHFPA-RTCVD）, is introduced to prepare SiGe：H thin films on substrate kept at a lower temperature. In the previous work, reactive thermal chemical vapour deposition （I~TCVD） technology was successfully used to prepare SiGe：H thin films, but the temperature of the substrate needed to exceed 400℃. In this work, very high frequency plasma method is used to assist RTCVD technology in reducing the temperature of substrate by largely enhancing the temperature of reacting gases on the surface of the substrate. The growth rate, structural properties, surface morphology, photo- conductivity and dark-conductivity of SiGe：H thin films prepared by this new technology are investigated for films with different germanium concentrations, and the experimental results are discussed.     

Rheological effect on thermocapillary flow of a liquid film jet painted on a moving boundary

In the present paper, a liquid (or melt) film of relatively high temperature ejected from a vessel and painted on the moving solid film is analyzed by using the second-order fluid model of the non-Newtonian fluid. The thermocapillary flow driven by the temperature gradient on the free surface of a Newtonian liquid film was discussed before. The effect of rheological fluid on thermocapillary flow is considered in the present paper. The analysis is based on the approximations of lubrication theory and perturbation theory. The equation of liquid height and the process of thermal hydrodynamics of the non-Newtonian liquid film are obtained, and the case of weak effect of the rheological fluid is solved in detail.     

Influence of Oxygen Vacancies on the Luminescence Spectra of Y2O3 Thin Films

Luminescence spectra of Y₂O₃ thin films annealed in air and in vacuum are investigated. It is established that the presence of oxygen vacancies leads to a decrease in the intensity of the luminescence band with a maximum at 3.4 eV (related to emission of selflocalized Frenkel excitons describing the excited state of a molecular ion (YO₆)^9–) and of the luminescence band with a maximum at 2.9 eV (related to the anion sublattice). It is revealed that the oxygen vacancies also lead to a decrease in the luminescence intensity in the 2.60, 2.35, 2.10. 1.90, and 1.70 eV bands that are related to radiative recombination in the donor–acceptor Y³⁺–O^2– pairs. The donor–acceptor distances are calculated.     

Optical Properties of Films of Cu x Ag1−x InSe2 Solid Solutions Obtained by Laser Evaporation

The structure and optical properties of the films of ternary compounds AgInSe₂, CuInSe₂ and Cu _x Ag_1–x InSe₂ solid solutions obtained by pulsed laser evaporation are investigated. It has been established that the films like bulk crystals have the structure of chalcopyrite. By the transmission and reflection spectra near the edge of natural absorption the refractive index and coefficient of optical absorption are calculated and the energies of interband transitions and the crystalline and spinorbit splitting are determined.     

X‐Ray Luminescence of Thin Oxide Films Containing Lead and Bismuth

We obtained thin films of the Bi₄Ge₃O₁₂, Bi₄Si₂O₁₂, PbWO₄, and Bi₂WO₆ scintillators and investigated their luminescence properties on xray excitation. We measured the xray luminescence spectra and established the linear character for the dependence of the luminescence intensity on the power of the dose of xray irradiation within the limits of up to 3·10^–3 A/kg. We investigated the radiation stability of the films obtained. The possibility of their application for detecting ionizing radiation is investigated. The films based on Bi₄Ge₃O₁₂ with an admixture of the Ge and Si or Mn activator of up to 1.5 mol.% are most suitable.     

Theoretical Investigation of Transparent (3–5 μm) and High Reflective (1.3 μm) Filter by Sol-Gel Process

When designing a cut-off interference filter, extra layers are needed to add on each side of periodic symmetrical multilayer to match the incident medium and the substrate. In this paper, we use sol-gel film with adjustable refractive index as the match layer. The influence of the refractive index and thickness of the match layer on the film system is discussed in detail. As an example, a special filter which is transparent (>80%) at the wavelength 3–5 m and high reflective (>90%) at the wavelength 1.3 m is designed. Finally a series of optimized film parameters are presented. The whole design process is a good reference to the other multilayer special filter made by sol-gel process.     

Influence of surface ordering on the wetting of structured liquids

The substrate is shown to induce substantial ordering in diblock copolymer thin films above the bulk order-disorder transition (ODT) where, thermodynamically, a phase mixed state is favored. Initially, uniform films reorganize to form a hierarchy of transient surface patterns and stable film thicknesses that depend on the initial film thickness and on the substrate. Self-consistent field calculations of the free energy of the system for different situations, depending on the relative tendency for the different block components to be attracted to the substrate and/or free surface, provide an explanation of the formation of the stable film thicknesses. A continuum picture proposed earlier by Brochard et al.rovides an explanation of the wetting characteristics of this system. In some cases the ordering destabilizes the film so that dewetting occurs (wetting autophobicity), whereas in other cases the surface ordering results in a kinetic stabilization of a film that would otherwise dewet. Received 3 August 2001 and Received in final form 1 November 2001