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The bidirectional reflectance distribution function (BRDF) is a well-defined quantity that allows the bidirectional reflectance of surfaces to be described. However, the light propagation in a specific direction cannot be perfectly realized in practice, because the physical apertures are not infinitesimal but finite. Consequently, a BRDF measurement cannot be considered fully bidirectional, although the measure coincides with the BRDF within a certain confidence level. To properly understand the impact of the finite apertures on the BRDF measures, the deviation between the real BRDF and the BRDF to be obtained using real experimental conditions with finite apertures was theoretically studied for surfaces with realistic BRDFs. The biconical reflectance factor was used to estimate these “measured BRDFs” in different geometrical conditions, and a family of negative exponential functions was defined to assess the impact on surfaces with different angular scattering distributions. An expression for estimating the relative error from finite apertures is given, which considers the angular variation of the BRDF and the different solid angles involved in the measurement.

Laser scanning confocal fluorescence microscopy measurements were performed on thermoplastic polyolefin (TPO) substrates that were coated with chlorinated polyolefin (CPO). The TPO investigated was a blend of high modulus polypropylene with an ethylene-butene copolymer (EBR9) containing 9 wt% butene. The CPO was a maleated chlorinated polypropylene containign 20 wt% Cl. The purpose of these experiments was to obtain detailed mechanistic information about the CPO-TPO interaction. To achieve acceptable contrast in these measurements, a fluorescent dye was covalently attached to a small portion of the CPO. Solvent wiping of the TPO substrates with isopropyl alcohol followed by xylenes prior to coating with CPO increased the mean roughness of the TPO surface by more than 100 nm; but it had a much larger effect on the roughness of the (several micrometers) CPO-TPO interface after coating. The EBR component of the TPO was shown to be exclusively responsible for the roughness increase. We also found evidence of a diffuse interface between the CPO and ERB components that was localized to sites in which the EBR was present at the TPO surface.

Various surface treatment methods were investigated to improve the adhesion of abrasion-resistant polymethylsilsesquioxane (PMSQ) coatings on the optical resins. The adhesion of PMSQ films was improved on polymethylmethacrylate (PMMA), polycarbonate (PC), and PC/acrylonitrile butadiene styrene (ABS) by pretreating their surface with O2 plasma or chromic acid followed by surface grafting with trimethyl ethoxysilane (TMES). After the O2 plasma and the subsequent TMES treatments, the adhesion of PMSQ coating on PMMA substrate was significantly enhanced by the reduction of the percentage of peeling area from ~100% to <1% in cross cut tests. After the chromic acid and the subsequent TMES treatments of PC and PC/ABS substrates, the adhesion of PMSQ coatings was also significantly enhanced by reducing the percentages of peeling areas from nearly 100% to 50% and <1%, respectively, for PC and PC/ABS. The PMSQ coating might increase the hardness of the polymer by two to three levels.

Sessile droplet freezing on textured micropillar surfaces was observed visually and thermographically. Hydrophobic surfaces with three different topographies were selected, the contact angles of water on which were 141°, 102°, and 138°. Droplet surface temperature distribution measurements from lateral view enabled quantitative evaluation of the freezing stages. According to the experiment, it was found that the surface hydrophobicity decreases with the increasing pillar distance. Only a slight increase in hydrophobicity was found with the decreasing pillar diameter. The liquid water droplet experienced five successive stages to become fully frozen. It was also confirmed that the droplet’s opaque appearance is caused by the sudden ice shell formation at the ice incipience. Besides, the solidification frontier (SF) movement inside the droplet was analyzed. The freezing rate was higher at the SF edge. Moreover, the textured surfaces with higher hydrophobicity were prone to further postpone the droplet’s freezing onset. However, surface topography showed minor impact on the droplet surface recalescence stage duration. Additionally, the droplet internal solidification stage lasted longer on samples with higher hydrophobicity.

MoS2 coatings are well-known for their solid lubricant properties and used as self-lubricants in vacuum and inert gas environments, and such coatings are not used in atmospheric conditions because of their deteriorating tribology. The tribological performance of MoS2 solid lubricant coatings in the different atmospheres has been improved by the codeposition of a small amount of another metal. In this study, the tribological behavior of MoS2/Nb coatings was investigated in ambient air at temperatures up to 500°C by using high-temperature pin-on-disc tribo testers and alumina balls as counterfaces. MoS2/Nb coatings were deposited on silicon wafers and AISI 52100 steel substrate by closed-field unbalanced magnetron sputtering. The structural analyses of the coatings were performed using X-ray diffraction and scanning electron microscopy techniques. The hardness was measured using a microhardness tester.

The development of effective anticorrosion pretreatments for metallic substrates is an issue of great importance for durability of metal structures and components. In this work for improved corrosion protection properties of sol–gel derived hybrid coatings, encapsulated corrosion inhibitors [2-mercaptobenzothiazole (MBT) and 2-mercaptobenzimidazole (MBI)] in the presence of β-cyclodextrin (β-CD) have been incorporated into hybrid coatings. Inclusion complex formation of MBI or MBT with β-CD led to encapsulated corrosion inhibitors which became active in corrosive electrolytes, and could slowly diffuse out of the host material to ensure continuous delivery of the inhibitors to corrosion sites and long-term corrosion protection. Structural characterization of the hybrid coatings were performed using EIS, SEM coupled with EDX, and FTIR.

Recently, magnesium (Mg) and its alloys have attracted more attention because of their biodegradability and fascinating mechanical properties in the medical field. However, their low corrosion resistance and high degradability in the body have a great effect on mechanical stability and cytocompatibility, which hinders its clinical applications. Therefore, here we introduce a bifunctional composite coating composed of polycaprolactone and synthesized hydroxyapatite nanoparticles (HA-NPs) loaded with simvastatin deposited on the AZ31 alloy via electrospinning technique. The synthesized HA-NPs and composite nanofibers layer were characterized using TEM, FE-SEM, FTIR, and XRD to understand the physiochemical properties of the composite nanofibers compared to pristine polymer and bare alloy. Corrosion resistance was evaluated electrochemically using potentiodynamic polarization and EIS measurements, and biodegradability was evaluated in terms of pH and Mg ions release in SBF solution. The as-prepared coating was found to retard the corrosion and increased the osteocompatibility as resulted in cell culture test, a higher cell attachment and proliferation on the implant biointerface, in addition to releasing simvastatin in a controlled platform.

Slot coating of particle suspensions is commonly used in the manufacturing of a wide variety of products. An important limit in this process is known as low-flow limit, which refers to the minimum wet film thickness that can be coated at a given substrate velocity. Recent studies have shown that shear-induced particle migration leads to a highly non-uniform particle distribution in the coating bead, playing an important role in the flow dynamics in slot coating of particulate systems. In this work, we extend the previous analyses to investigate the effects of particle migration on the low-flow limit in slot coating of particle suspensions at both dilute and concentrated conditions. As a first approximation, the suspension is modeled as a Newtonian liquid with a concentration-dependent viscosity, and shear-induced particle migration is described according to the diffusive flux model. The resulting set of governing equations is solved with a stabilized finite element method coupled with the elliptic mesh generation method for the free-boundary problem. The results show that particle migration changes the liquid viscosity near the downstream meniscus and strongly affects the force balance that sets the critical operating conditions at the low-flow limit. Remarkably, it was found that particle migration enlarges the operating window of the process when the suspensions are compared to a Newtonian liquid with the same bulk properties, especially at high concentrations.