Influence Of Substrate Conductivity Research Articles

STUDY OF THE Ni(OH)2 ELECTROCHROMIC PROPERTIES OF FILMS DEPOSITED ON FTO GLASS WITH AN ADDITIONAL CONDUCTING LAYER

This work attempts to evaluate the influence of substrate conductivity on electrochromic and electrochemical properties of Ni(OH)2/PVA composite films, including coloration and bleaching rate. The conductivity of FTO glass was improved by depositing a silver gird with differing line densities. For deposition of the silver lines, aerosol jet printing method was used. As a result, few electrochromic films were deposited onto bare FTO glass and FTO glass with silver grid deposited onto it. In order to investigate deposited electrochromic films, the cyclic voltammetry with simultaneous recording of the optical characteristics is used. The optical characteristics of films were rather close to each other. At the same time, their electrochemical properties are different. It is found that the additional peaks observed is that of silver, which is electrochemically active in used potential window. In addition it was observed that during electrochemical cycling of Ni(OH)2/PVA deposited on substrates with silver grid, the last changed color from shiny metallic to black color. It is proposed that color changes of silver grid caused by silver transforming to Ag2O or AgO and back to metallic silver. It is found, that for small areas of electrochromic platings, substrate resistivity has a negligible effect on coloration and bleaching rates. The coloration and bleaching rates for Ni(OH)2/PVA films deposited onto the bare substrate, the substrate with a silver grid (1 cm cell size) and the substrate with a silver grid (0.5 cm cell size) were: –1.45, –1.71, –1.40 and 1.1, 0.75, 0.84 %∙s-1. It is suggested that the effect of substrate conductivity will clearly be seen when the physical sizes of substrate increase. Also it was underlined that for further experiments for effect definition of substrate resistivity on electrochromic properties inherit conductive materials should be used

Natural Convection in a Series of Thermally Interacting Cavities with Wall Mounted Heaters

Laminar natural convection in a series of thermally interacting cavities is numerically studied. Each cavity consists of a conducting bottom wall with a surface mounted heater. The side walls of the cavities are isothermally cooled. Each cavity thermally interacts with its adjacent cavities through the conducting walls. Flow and heat transfer characteristics are studied in detail for various Rayleigh numbers. The convection characteristics in multiple cavities are compared with those in single independent cavity. The thermal interaction between the cavities results in lower temperatures compared with those in independent cavities. While heat is rejected into the adjacent upper cavity through some portion of the conducting wall, heat is received from the adjacent cavity through the remaining portion of the wall. The influence of substrate conductivity on heat exchange between adjacent cavities are examined. Substrate conductivity shows strong effect on temperature distribution. When cooling at both vertical sides is changed to one side cooling, the heat transfer characteristics are changed drastically and many interesting flow features are observed. Effects of cavity aspect ratio is studied and higher heat transfer rates are observed at higher aspect ratios. Correlations for dimensionless temperature maximum and average Nusselt number are presented in terms of Rayleigh number.

Conjugate Thermal Analysis of Air-Cooled Discrete Flush-Mounted Heat Sources in a Horizontal Channel

Thermal analysis with comprehensive treatment of conjugate heat transfer is performed in this study for discrete flush-mounted heat sources in a horizontal channel cooled by air. The numerical model accounts for mixed convection, radiative exchange and two-dimensional conduction in the substrate. The model is first used to simulate available experimental work to demonstrate its accuracy and practical utility. A parametric study is then undertaken to assess the effects of Reynolds number, surface emissivity of walls and heat sources, as well as thickness and thermal conductivity of substrate, on flow field and heat transfer characteristics. It is shown that due to radiative heat transfer, the wall temperatures are brought closer, and the trend of temperature variation along the top wall is significantly altered. Such effects are more pronounced for higher surface emissivity and/or lower Reynolds numbers. The influence of substrate conductivity and thickness is related in that a large value of either substrate conductivity or thickness facilitates redistribution of heat and tends to yield a uniform temperature field in the substrate. For highly conductive or thick substrate, the “hot spot” cools down and may occur in upstream sources. Radiation loss to the ambient increases with substrate conductivity and thickness due to the elevated temperature near the openings, yet the total heat transfer over the bottom surface by convection and radiation remains essentially unaltered.

Numerical and Experimental Investigation of Laminar Channel Flow With a Transparent Wall

A numerical and experimental investigation is undertaken for developing laminar flow in a duct with one opaque, uniformly heated wall and one transparent wall. In the numerical model, mixed convection, radiative exchange, as well as two-dimensional conduction in the substrate are considered. Experiments are conducted in a high-aspect-ratio rectangular channel using infrared thermography to validate the numerical model and visualize the temperature field on a heated surface. An extended parametric study using the validated model is also carried out to assess the impact of channel height, and thermal conductivity and thickness of the substrate. For a channel height of H=6 mm and a heating power of qs=257 W/m2, as Re increases from 150 to 940 the fraction of heat transfer by convection from the heated surface rises from 65% to 79%. At Re=150, as H increases from 6 mm to 25 mm, radiation from the heated surface increases from 35% to 70% of the total heating power. The influence of substrate conductivity and thickness on local flux distributions is limited to regions near the channel inlet and outlet. Over the entire parametric space considered, radiation loss from the interior duct surfaces to the inlet and outlet apertures is less than 2% of the total heat input and thus unimportant.

Influence of Substrate Conductivity on Circulation Reversal in Evaporating Drops

Nonuniform evaporation from sessile droplets induces radial convection within the drop, which produces the well-known "coffee-ring" effect. The evaporation also induces a gradient in temperature and consequently a gradient in surface tension, generating a Marangoni flow. Here we investigate theoretically and experimentally the thermal Marangoni flow and establish criteria to gauge its influence. An asymptotic analysis indicates that the direction of the flow depends on the relative thermal conductivities of the substrate and liquid, k_{R} identical withk_{S}/k_{L}, reversing direction at a critical contact angle over the range 1.45<k_{R}<2. We corroborate the theory experimentally and demonstrate that the Marangoni flow can significantly influence the resulting patterns of particle deposition.

Influence of substrate conductivity on layer thickness in LPE GaAs

Differences have been found on the growth rate of epitaxial layers grown simultaneously on semi-insulating and P and N type (1 0 0) GaAs substrates from the same Ga–As liquid solution. The layers were grown by LPE at 786°C using an initial supercooling of 15°C and a cooling rate of 0.5°C/min. The thickness of the grown layers was measured, under an optical microscope, in cleaved cross-sections etched in a FeCl 3–HCl solution. To fit the thickness-growth time data to the theoretical expression used for diffusion-limited growth it is necessary to use different initial supercoolings for the layers grown in each substrate, in spite that those layers were grown at the same time, from the same solution and therefore under exactly the same conditions.

Influence of substrate conductivity on electrochemical polymerization of O-methoxyaniline

The influence of substrate conductivity on electrochemical polymerization (ECP) of O-methoxyaniline on transparent conducting SnO 2 and SnO 2:F coated glass substrates has been investigated. In this work, transparent conducting SnO 2 and SnO 2:F coated glass substrates having different electrical conductivities were used as the substrates for the synthesis of poly ( O-methoxyaniline) (POMA) thin films. These substrates were characterized by x-ray diffraction (XRD) measurements. The POMA thin films were synthesized on these substrates by ECP of O-methoxyaniline under cyclic voltammetric conditions. The POMA thin films were characterized by cyclic voltammetry, UV-visible spectroscopy, scanning electron microscopy (SEM) and electrical conductivity measurements. It was observed that the efficiency of the polymerization process depends on the substrate conductivity and it increases with increasing the substrate conductivity. The optical absorption spectra show a major peak at ∼800 nm corresponding to emeraldine salt (ES) phase of POMA irrespective of the substrate conductivity. However, the systematic increase in the overall absorbance and the sharpness of the peak at ∼800 nm is observed with the increase in the substrate conductivity. The surface morphology of the POMA films also found to be depend on the substrate conductivity.

Influence of substrate conductivity on characteristics of ZnO/SiO2-diaphragm piezoelectric resonators

Most of the ZnO/SiO2-diaphragm piezoelectric composite resonators on silicon substrates exhibit Q-factors of the anti-resonance much lower than those of the resonance. It is demonstrated both theoretically and experimentally that this is caused by the conductivity of the substrate.