A revised two-equation model of turbulence

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Chapter 16 Synthesis Of Crystalline C-N Thin Films

This chapter describes the physico-chemical phenomena underlying the synthesis of crystalline carbon nitride (C-N) thin films. In section 1, the status of current research on C-N films is briefly reviewed as well as its benefits. Section 2 describes the experimental techniques employed to produce C-N films. These techniques include laser ablation of graphite targets in an atomic nitrogen ambience, dual ion beam assisted deposition, reactive sputtering of pure graphite target with pure N2, rf-plasma-assisted hot filament chemical vapor deposition (cvd) and ion implantation. The theoretical models are described in section 3 for predicting the thermal stability and formation of C-N films. These models include thermodynamics, molecular dynamics, and thermal spike. In section 4, some characterization techniques are described including X-ray diffraction (XRD) and transmission electron microscopy (TEM) for microstructure, rutherford backscattering (RBS) and auger electron spectroscopy (AES) for composition, and electron energy loss spectroscopy (EELS) and X-ray photoelectron spectroscopy (XPS) for chemical state. Some characterization results are also presented. The prospects for practical application of C-N films are summarized in the concluding section 5. Some diagnostic questions are provided at the end to reinforce the materials discussed in the chapter. © 2007 Elsevier Inc. All rights reserved

Synthesis And Characterisation Of Sol-Gel Derived Nanostructured Composite Of Zno/Pvp Thin Films

Pure ZnO films and ZnO nanoparticle dispersed polyvinylpyrrolidone (PVP) films were prepared on a Pyrex glass substrate by sol-gel dip coating using a zinc acetate precursor. The thin film is extensively characterised for its surface morphology, chemistry, thickness and nanocrystallite size, using various advanced analytical techniques such as SEM, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscopy. Under the given processing conditions, ZnO semiconductor thin films with nanocrystallite size 20-30 nm were obtained, and the ZnO nanoparticle size in the PVP matrix increased with increase in ZnO content. © 2004 Institute of Materials, Minerals and Mining

Synthesis And Morphological Characterization On Pvp/Zno Nano Hybrid Films

The synthesis-structure relationship in sol-gel derived PVP/ZnO nanocomposite films using was analyzed. The surface morphology of the thin film was studied using atomic force microscopy (AFM) in the tapping mode. The average nanocrystalline size within the film was estimated. The Fourier transform infrared spectra (FTIR) were recorded in the reflection mode. The results show that the sol-gel technique is a viable method for production M/SC-polymer nanocomposite films

Semi-Analytical Solution Of A Constrained Fourth-Order Integro-Differential Equation Of Steady Flow-Structure Interaction In A Model Collapsible Tube

We provide accurate, non-perturbative, semi-analytical solutions to a constrained fourth-order integro-differential equation derived by Djorjevic and Vukobratovic [On a steady, viscous flow in two-dimensional channels, Acta Mech. 163 (2003) 189-205] in the study of a steady incompressible flow through a flexible 2D tube. Our numerical experiments motivate the introduction of a global parameter that monitors the deformation of the tube as a function of material properties and flow characteristics. Physically, this parameter is proportional to the work done by the longitudinal tension on the wall. An example is provided on how this global parameter can be used to monitor coronary lesion progression. In particular, this parameter is used to define an index of criticality of such lesions. © 2005 Elsevier Inc. All rights reserved

Effect Of Thermal Conductivity On Reaction Front Propagation During Combustion Synthesis Of Intermetalics

A mathematical model is developed to investigate the effect of thermal conductivity on the combustion synthesis of intermetallics. The governing equations are solved using a high-order-implicit numerical scheme capable of accommodating the steep spatial and temporal gradients of properties. A parametric study is then performed to elucidate reaction characteristics (propagation type, steady-state propagation velocity, peak temperature, etc.) in terms of the thermal conductivity ratio, κ=k p /k r. The predicted results appear plausible and consistent with the trends presented in the available literature. © 2006 Springer Science + Business Media, Inc

Modeling Of Aerosol Spray Characteristics For Synthesis Of Sensor Thin Film From Solution

A model is developed of aerosol spray for synthesis of sensor film from solution. The synthesis technique considered involves atomization of a solution of mixed salts in methanol, spraying of solution droplets, droplet deposition on a heated substrate, evaporation and chemical reaction to produce mixed oxides, and subsequent film growth. The precise control of oxide nanoparticle size distribution and inter-particle spacing in the film is crucial to achieving high sensitivity. These in turn largely depend on the droplet characteristics prior to impingement on the substrate. This paper focuses on the development of a model to describe the atomization and spray processes prior to the film growth. Specifically, a mathematical model is developed utilizing computational fluid dynamics solution of the equations governing the transport of atomized droplets from the nozzle to the substrate in order to predict droplet characteristics in flight. The predictions include spatial distribution of droplet size and concentration, and the effect on these characteristics of swirling inlet flow at the spray nozzle. © 2013 Elsevier Inc