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Special Issue on "Thin Film Processes"

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Hyun Wook Jung

Processes 2020, 8(5), 564; https://doi.org/10.3390/pr8050564 - 11 May 2020

Cited by 2 | Viewed by 1420

Abstract

Thin film processes are significantly incorporated in manufacturing display panels, secondary batteries, fuel/solar cells, catalytic films, membranes, adhesives, and other commodity films [...] Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Comparison of Growth Characteristics and Properties of CVD TiN and TiO₂ Anti-Coking Coatings

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Processes 2019, 7(9), 574; https://doi.org/10.3390/pr7090574 - 30 Aug 2019

Cited by 6 | Viewed by 2078

Abstract

Coating metals with anti-coking materials inhibit their catalytic coking and are especially beneficial in the pyrolysis of hydrocarbon fuels. It is believed that growth characteristics and properties may play a pivotal role in the anti-coking performance of chemical vapor deposition (CVD) coatings. In [...] Read more.

Coating metals with anti-coking materials inhibit their catalytic coking and are especially beneficial in the pyrolysis of hydrocarbon fuels. It is believed that growth characteristics and properties may play a pivotal role in the anti-coking performance of chemical vapor deposition (CVD) coatings. In this study, TiN and TiO₂ coatings were obtained by CVD using TiCl₄–N₂–H₂ and TiCl₄–H₂–CO₂ systems, respectively. The effects of deposition time, residence time, and partial pressure were examined, and the coating microstructure was characterized by scanning electron microscopy (SEM). The results reveal that the effect of deposition parameters on the growth characteristics of TiN and TiO₂ coatings is very different. The growth of the TiN coating shows characteristics of the island growth model, while the TiO₂ coating follows the layer model. In general, the growth rate of the star-shaped TiN crystals is higher than that of crystals of other shapes. For the TiO₂ coating, the layer mode growth characteristics indicate that the morphology of the TiO₂ coating does not change significantly with the experimental conditions. Coking tests showed that the morphology of non-catalytic cokes is not only affected by the temperature, pressure, and coking precursor, but is also closely related to the surface state of the coatings. Both TiN and TiO₂ coatings can effectively prevent catalytic coking and eliminate filamentous cokes. In some cases, however, the N or O atoms in the TiN and TiO₂ coatings may affect common carbon deposits formed by non-catalytic coking, such as formation of needle-like and flaky carbon deposits. Full article

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Open AccessArticle

Digitalizing the Paints and Coatings Development Process

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Processes 2019, 7(8), 539; https://doi.org/10.3390/pr7080539 - 15 Aug 2019

Cited by 7 | Viewed by 5084

Abstract

Numerous laboratory tests are used to determine the appropriateness of new formulations in the development process in the paint and coatings industry. New formulations are most often functionally inadequate, unacceptable for environmental or health reasons, or too expensive. Formulators are obliged to repeat [...] Read more.

Numerous laboratory tests are used to determine the appropriateness of new formulations in the development process in the paint and coatings industry. New formulations are most often functionally inadequate, unacceptable for environmental or health reasons, or too expensive. Formulators are obliged to repeat laboratory tests until one of the formulations fulfills the minimum requirements. This is cumbersome, slow, and expensive, and can cause ecological problems, wasting materials on tests that do not produce the desired results. The purpose of this research was to find out if there might be a better way forward to increase efficiency and free up formulators to focus on new products. In this experiment, a new paints and coatings development process was redesigned based on the potential benefits of formulation digitalization. Instead of laboratory testing, a digital platform was used that has been developed and stocked with relevant, up-to-date, and complete, usable data. This study found that, by going digital, developers could vastly reduce non-value-added activities in the development process (by as much as 70%) and significantly shorten the entire process throughput time (by up to 48%). Using digital tools to facilitate the development process appears to be a possible way forward for the paint and coatings industry, saving time, materials, and money and protecting the environment. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Impact of Thermal Radiation on Magnetohydrodynamic Unsteady Thin Film Flow of Sisko Fluid over a Stretching Surface

by

Abdul Samad Khan

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Yufeng Nie

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Zahir Shah

Processes 2019, 7(6), 369; https://doi.org/10.3390/pr7060369 - 12 Jun 2019

Cited by 19 | Viewed by 2981

Abstract

The current article discussed the heat transfer and thermal radioactive of the thin liquid flow of Sisko fluid on unsteady stretching sheet with constant magnetic field (MHD). Here the thin liquid fluid flow is assumed in two dimensions. The governing time-dependent equations of [...] Read more.

The current article discussed the heat transfer and thermal radioactive of the thin liquid flow of Sisko fluid on unsteady stretching sheet with constant magnetic field (MHD). Here the thin liquid fluid flow is assumed in two dimensions. The governing time-dependent equations of Sisko fluid are modeled and reduced to Ordinary differential equations (ODEs) by use of Similarity transformation with unsteadiness non-dimensionless parameter

S t

. To solve the model problem, we used analytical and numerical techniques. The convergence of the problem has been shown numerically and graphically using Homotopy Analysis Method (HAM). The obtained numerical result shows that the HAM estimates of the structures is closed with this result. The Comparison of these two methods (HAM and numerical) has been shown graphically and numerically. The impact of the thermal radiation

R d

and unsteadiness parameter

S t

over thin liquid flow is discovered analytically. Moreover, to know the physical representation of the embedded parameters, like

β

, magnetic parameter M, stretching parameter

ξ

, and Sisko fluid parameters

ε

have been plotted graphically and discussed. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Comparative Study of the Performances of Al(OH)₃ and BaSO₄ in Ultrafine Powder Coatings

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Weihong Li

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Diego Cárdenas Franco

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Processes 2019, 7(5), 316; https://doi.org/10.3390/pr7050316 - 27 May 2019

Cited by 10 | Viewed by 5801

Abstract

Ultrafine powder coatings are one of the development directions in the powder coating industry, as they can achieve thin coatings with good leveling and high surface smoothness comparable to liquid coatings. Compared to regular coatings, they experience a higher sensitivity to any incompatibilities, [...] Read more.

Ultrafine powder coatings are one of the development directions in the powder coating industry, as they can achieve thin coatings with good leveling and high surface smoothness comparable to liquid coatings. Compared to regular coatings, they experience a higher sensitivity to any incompatibilities, e.g., filler from coating components. The properties of fillers play a great role in the performance of coating films. Aluminum trihydrate (Al(OH)₃) is a well-known filler in solvent-based coatings and other polymer industries. To study and evaluate the performances of Al(OH)₃ in ultrafine powder coatings, a popular filler, barium sulfate (BaSO₄) is used for comparison. Both fillers are added in ultrafine powder coatings based on two of the most commonly used resin systems (polyester-epoxy and polyester). The differences of physical and chemical properties between both fillers have significant influences on several properties of powder paints and coating films. The polar groups (hydrogen bond) in Al(OH)₃ result in the strong interaction between inorganic filler and organic polymer matrix, thus decreasing the molecular network mobility and influencing the chain formation, which is verified by differential scanning calorimetric (DSC). The bed expansion ratio (BERs) of powder paints incorporated with Al(OH)₃ are much higher than those with BaSO₄, which indicate more uniform gas-solid contact during the spraying process. Samples with Al(OH)₃ exhibit much lower specular gloss at 60°, which are expected to achieve remarkable matting effects. Superior corrosion resistances can be observed for almost all the coated panels incorporated with Al(OH)₃ in contrast to those with BaSO₄. Other aspects are slightly influenced by the difference between the two fillers, such as the angle of repose values (AORs) of powder paints, the impact resistance and flexibility of coating films. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Viscoelastic MHD Nanofluid Thin Film Flow over an Unsteady Vertical Stretching Sheet with Entropy Generation

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Processes 2019, 7(5), 262; https://doi.org/10.3390/pr7050262 - 06 May 2019

Cited by 29 | Viewed by 3586

Abstract

The boundary-layer equations for mass and heat energy transfer with entropy generation are analyzed for the two-dimensional viscoelastic second-grade nanofluid thin film flow in the presence of a uniform magnetic field (MHD) over a vertical stretching sheet. Different factors, such as the thermophoresis [...] Read more.

The boundary-layer equations for mass and heat energy transfer with entropy generation are analyzed for the two-dimensional viscoelastic second-grade nanofluid thin film flow in the presence of a uniform magnetic field (MHD) over a vertical stretching sheet. Different factors, such as the thermophoresis effect, Brownian motion, and concentration gradients, are considered in the nanofluid model. The basic time-dependent equations of the nanofluid flow are modeled and transformed to the ordinary differential equations system by using similarity variables. Then the reduced system of equations is treated with the Homotopy Analysis Method to achieve the desire goal. The convergence of the method is prescribed by a numerical survey. The results obtained are more efficient than the available results for the boundary-layer equations, which is the beauty of the Homotopy Analysis Method, and shows the consistency, reliability, and accuracy of our obtained results. The effects of various parameters, such as Nusselt number, skin friction, and Sherwood number, on nanoliquid film flow are examined. Tables are displayed for skin friction, Sherwood number, and Nusselt number, which analyze the sheet surface in interaction with the nanofluid flow and other informative characteristics regarding this flow of the nanofluids. The behavior of the local Nusselt number and the entropy generation is examined numerically with the variations in the non-dimensional numbers. These results are shown with the help of graphs and briefly explained in the discussion. An analytical exploration is described for the unsteadiness parameter on the thin film. The larger values of the unsteadiness parameter increase the velocity profile. The nanofluid film velocity shows decline due the increasing values of the magnetic parameter. Moreover, a survey on the physical embedded parameters is given by graphs and discussed in detail. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Impact of Thermal Radiation and Heat Source/Sink on MHD Time-Dependent Thin-Film Flow of Oldroyed-B, Maxwell, and Jeffry Fluids over a Stretching Surface

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Abdul Samad Khan

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Yufeng Nie

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Zahir Shah

Processes 2019, 7(4), 191; https://doi.org/10.3390/pr7040191 - 02 Apr 2019

Cited by 19 | Viewed by 2787

Abstract

In this study paper, we examined the magnetohydrodynamic (MHD) flow of three combined fluids, Maxwell, Jeffry, and Oldroyed- B fluids, with variable heat transmission under the influence of thermal radiation embedded in a permeable medium over a time-dependent stretching sheet. The fluid flow [...] Read more.

In this study paper, we examined the magnetohydrodynamic (MHD) flow of three combined fluids, Maxwell, Jeffry, and Oldroyed- B fluids, with variable heat transmission under the influence of thermal radiation embedded in a permeable medium over a time-dependent stretching sheet. The fluid flow of liquid films was assumed in two dimensions. The fundamental leading equations were changed to a set of differential nonlinear and coupled equations. For this conversion, suitable similarity variables were used. An optimal tactic was used to acquire the solution of the modeled problems. The convergence of the technique has been shown numerically. The obtained analytical and numerical consequences are associated graphically and tabulated. An excellent agreement was obtained between the homotropy analysis method (HAM) and numerical methods. The variation of the skin friction and Nusslet number and their influence on the temperature and concentration profiles were scrutinized. The influence of the thermal radiation, unsteadiness effect, and MHD were the main focus of this study. Furthermore, for conception to be physically demonstrated, the entrenched parameters are discussed graphically in detail along with their effect on liquid film flow. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Model for Thin Layer Drying of Lemongrass (Cymbopogon citratus) by Hot Air

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Processes 2019, 7(1), 21; https://doi.org/10.3390/pr7010021 - 04 Jan 2019

Cited by 38 | Viewed by 5822

Abstract

Lemongrass is a plant that contains aromatic compounds (myrcene and limonene), powerful deodorants, and antimicrobial compounds (citral and geraniol). Identifying a suitable drying model for the material is crucial for establishing an initial step for the development of dried products. Convection drying is [...] Read more.

Lemongrass is a plant that contains aromatic compounds (myrcene and limonene), powerful deodorants, and antimicrobial compounds (citral and geraniol). Identifying a suitable drying model for the material is crucial for establishing an initial step for the development of dried products. Convection drying is a commonly used drying method that could extend the shelf life of the product. In this study, a suitable kinetic model for the drying process was determined by fitting moisture data corresponding to four different temperature levels: 50, 55, 60 and 65 °C. In addition, the effect of drying temperature on the moisture removal rate, the effective diffusion coefficient and activation energy were also estimated. The results showed that time for moisture removal increases proportionally with the air-drying temperature, and that the Weibull model is the most suitable model for describing the drying process. The effective diffusion coefficient ranges from 7.64 × 10⁻¹¹ m²/s to 1.48 × 10⁻¹⁰ m²/s and the activation energy was 38.34 kJ/mol. The activation energy for lemongrass evaporation is relatively high, suggesting that more energy is needed to separate moisture from the material by drying. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Experimental Studies on Corrosion Behavior of Ceramic Surface Coating using Different Deposition Techniques on 6082-T6 Aluminum Alloy

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Processes 2018, 6(12), 240; https://doi.org/10.3390/pr6120240 - 26 Nov 2018

Cited by 13 | Viewed by 4480

Abstract

Aluminum alloys cannot be used in aggressive corrosion environments application. In this paper, three different surface coating technologies were used to coat the 6082-T6 aluminum alloy to increase the corrosion resistance, namely Plasma Electrolytic Oxidation (PEO), Plasma Spray Ceramic (PSC) and Hard Anodizing [...] Read more.

Aluminum alloys cannot be used in aggressive corrosion environments application. In this paper, three different surface coating technologies were used to coat the 6082-T6 aluminum alloy to increase the corrosion resistance, namely Plasma Electrolytic Oxidation (PEO), Plasma Spray Ceramic (PSC) and Hard Anodizing (HA). The cross-sectional microstructure analysis revealed that HA coating was less uniform compared to other coatings. PEO coating was well adhered to the substrate despite the thinnest layer among all three coatings, while the PSC coating has an additional loose layer between the coat and the substrate. X-ray diffraction (XRD) analysis revealed crystalline alumina phases in PEO and PSC coatings while no phase was detected in HA other than an aluminum element. A series of electrochemistry experiments were used to evaluate the corrosion performances of these three types of coatings. Generally, all three-coated aluminum showed better corrosion performances. PEO coating has no charge transfer under all Inductive Coupled Plasma (ICP) tests, while small amounts of Al³⁺ were released for both HA and PSC coatings at 80 °C. The PEO coating showed the lowest corrosion current density followed by HA and then PSC coatings. The impedance resistance decreased as the immersion time increased, which indicated that this is due to the degradation and deterioration of the protective coatings. The results indicate that the PEO coating can offer the most effective protection to the aluminum substrate as it has the highest enhancement factor under electrochemistry tests compared to the other two coatings. Full article

(This article belongs to the Special Issue Thin Film Processes)

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Open AccessArticle

Fabrication of New Liquid Crystal Device Using Layer-by-Layer Thin Film Process

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Processes 2018, 6(8), 108; https://doi.org/10.3390/pr6080108 - 01 Aug 2018

Cited by 11 | Viewed by 4245

Abstract

Indium tin oxide (ITO) transparent electrodes are troubled with high cost and poor mechanical stability. In this study, layer-by-layer (LBL)-processed thin films with single-walled carbon nanotubes (SWNTs) exhibited high transparency and electrical conductivity as a candidate for ITO replacement. The repetitive deposition of [...] Read more.

Indium tin oxide (ITO) transparent electrodes are troubled with high cost and poor mechanical stability. In this study, layer-by-layer (LBL)-processed thin films with single-walled carbon nanotubes (SWNTs) exhibited high transparency and electrical conductivity as a candidate for ITO replacement. The repetitive deposition of polycations and stabilized SWNTs with a negative surfactant exhibits sufficiently linear film growth and high optoelectronic performance to be used as transparent electrodes for vertically aligned (VA) liquid crystal display (LCD) cells. The LC molecules were uniformly aligned on the all of the prepared LBL electrodes. VA LCD cells with SWNT LBL electrodes exhibited voltage-transmittance (V-T) characteristics similar to those with the conventional ITO electrodes. Although the response speeds were slower than the LCD cell with the ITO electrode, as the SWNT layers increased, the display performance was closer to the LCD cells with conventional ITO electrode. This work demonstrated the good optoelectronic performance and alignment compatibility with LC molecules of the SWNT LBL assemblies, which are potential alternatives to ITO films as transparent electrodes for LCDs. Full article

(This article belongs to the Special Issue Thin Film Processes)

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