108 research outputs found
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Laser nitriding method of making phosphor bronze with surface-embedded titanium carbide particles
The laser nitriding method of making phosphor bronze with surface-embedded titanium carbide particles involves coating a cleaned phosphor bronze workpiece with a thin film formed of a carbonaceous layer mixed with nanosize particles of titanium carbide. The titanium carbide forms about 5 wt % of the thin film, and the phosphor bronze workpiece is composed of about 6.0 wt % tin, about 0.1 wt % phosphorous, and about 93.9 wt % copper. A laser beam is then scanned over the thin film formed on the phosphor bronze workpiece. Coaxially and simultaneously with the laser beam, a stream of nitrogen gas is sprayed on the thin film formed on the phosphor bronze workpiece in order to provide the workpiece with a nitride coating having nanoparticles of titanium carbide embedded therein
Laser Short-Pulse Heating of a Three Layer Assembly and the Seebeck Effect
Laser short pulse heating of a multi-layer assembly, which consists of different layer properties, results in a non-similar electron and lattice site temperature distributions in the layers. This is because the differences in the amount of energy transfer in each layer despite the fact that each layer is very thin. Consequently, an investigation into the temperature distribution in the electron and lattice subsystems in each layer is essential. In the present study, laser short-pulse heating of a three layer assembly, consisting of Au-Cr-Cu, is examined. The electron and lattice site temperature rise in each layer is predicted using an electron lattice theory approach. Three-dimensional heating situation is accommodated in the model study. The Seebeck coefficient in each layer is computed and compared with the results of the previously derived equation. It is found that the electron temperature distribution varies in each layer and that this variation affects the lattice site temperature distribution. The lattice temperature distribution in the radial direction is not influenced by the diffusion of energy in the radial direction. Abrupt changes in the Seebeck coefficient across chromium and copper layers are observed
Laser Short-Pulse Heating of a Three Layer Assembly and the Seebeck Effect
Laser short pulse heating of a multi-layer assembly, which consists of different layer properties, results in a non-similar electron and lattice site temperature distributions in the layers. This is because the differences in the amount of energy transfer in each layer despite the fact that each layer is very thin. Consequently, an investigation into the temperature distribution in the electron and lattice subsystems in each layer is essential. In the present study, laser short-pulse heating of a three layer assembly, consisting of Au-Cr-Cu, is examined. The electron and lattice site temperature rise in each layer is predicted using an electron lattice theory approach. Three-dimensional heating situation is accommodated in the model study. The Seebeck coefficient in each layer is computed and compared with the results of the previously derived equation. It is found that the electron temperature distribution varies in each layer and that this variation affects the lattice site temperature distribution. The lattice temperature distribution in the radial direction is not influenced by the diffusion of energy in the radial direction. Abrupt changes in the Seebeck coefficient across chromium and copper layers are observed
Investigation Into The Seebeck Coefficient in Two-Layer Assembly During Laser Short-Pulse Heating
The Seebeck coefficient in a substrate varies with electron temperature such that it increases with increasing temperature. The Seebeck coefficient for different materials differs even though the materials have similar thermal properties. In this study, the Seebeck coefficient in a two-layer assembly exposed to laser short-pulse heating is considered. The assembly consists of gold and copper, and the gold layer is situated on top of the copper. In order to investigate the change in the Seebeck coefficient with layer thickness, three different thicknesses of gold layer are accommodated in the simulations. An abrupt change in the Seebeck coefficient occurs across the layers, despite the smooth decay of electron temperatures in this region due to the similar thermal properties of the layer materials. Consequently, the Seebeck coefficient variation across the layers can form the basis for measurement of layer thickness
Investigation Into The Seebeck Coefficient in Two-Layer Assembly During Laser Short-Pulse Heating
The Seebeck coefficient in a substrate varies with electron temperature such that it increases with increasing temperature. The Seebeck coefficient for different materials differs even though the materials have similar thermal properties. In this study, the Seebeck coefficient in a two-layer assembly exposed to laser short-pulse heating is considered. The assembly consists of gold and copper, and the gold layer is situated on top of the copper. In order to investigate the change in the Seebeck coefficient with layer thickness, three different thicknesses of gold layer are accommodated in the simulations. An abrupt change in the Seebeck coefficient occurs across the layers, despite the smooth decay of electron temperatures in this region due to the similar thermal properties of the layer materials. Consequently, the Seebeck coefficient variation across the layers can form the basis for measurement of layer thickness
Focusing of phase change microparticles for local heat transfer enhancement in laminar flows
Phase change material (PCM) suspensions have received wide spread attention for increased thermal storage in various thermal systems such as heat sinks for electronics and solar thermal applications. To achieve further heat transfer enhancement, this paper investigates the effect of focusing micron-sized phase-change particles (PCMs) to a layer near the heated wall of a parallel plate channel. A numerical model for fully-developed laminar flow with a constant heat flux applied to one wall is developed. Melting of the focused PCMs is incorporated using a temperature-dependent effective heat capacity. The effect of channel height, height of the focused PCM stream, heat flux, and fluid properties on the peak local Nusselt number (Nu∗) and the averaged Nusselt number over the melting length (Nu[subscript melt]) are investigated. Compared to the thermally-developed Nusselt number for this geometry (Nuo = 5.385), Nu[subscript melt]and Nu∗ enhancements of 8% and 19% were determined, respectively. The local heat transfer performance is optimized when the PCMs are confined to within 30% of the channel height. The present work provides an extended understanding of local heat transfer characteristics during melting of flowing PCM suspensions, and offers a new method for enhancing heat transfer performance in various thermal-fluidic systems
Characterization of Environmental Dust in the Dammam Area and Mud After-Effects on Bisphenol-A Polycarbonate Sheets
Owing to recent climate changes, dust storms are increasingly common, particularly in the Middle East region. Dust accumulation and subsequent mud formation on solid surfaces in humid environments typically have adverse effects on surface properties such as optical transmittance, surface texture, and microhardness. This is usually because the mud, which contains alkaline and ionic species, adheres strongly to the surface, often through chemical bonds, and is therefore difficult to remove. In this study, environmental dust and the after-effects of mud formed on a polycarbonate sheet, which is commonly used as a protective glass in photovoltaic cells. Ionic compounds (OH−) are shown to significantly affect the optical, mechanical, and textural characteristics of the polycarbonate surface, and to increase the adhesion work required to remove the dry mud from the polycarbonate surface upon drying. Such ability to modify characteristics of the polycarbonate surface could address the dust/mud-related limitations of superhydrophobic surfaces
Corrosion properties of duplex treated Ti-6Al-4V alloy in chloride media using electrochemical and positron annihilation spectroscopy techniques
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