Facile Synthesis of Fluorinated Polysilazanes and Their Durable Icephobicity on Rough Al Surfaces

Superhydrophobic Al surfaces with excellent durability and anti-icing properties were fabricated by coating dual-scale rough Al substrates with fluorinated polysilazane (FPSZ). Flat Al plates were etched using an acidic solution, followed by immersion in boiling water to generate hierarchical micro-nano structures on their surfaces. The FPSZ coatings were synthesized by grafting 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS-17), a fluoroalkyl silane), onto methylpolysilazane, an organopolysilazane (OPSZ) backbone. The high water contact angle (175°) and low sliding angle (1.6°) of the FPSZ-coated sample with an FAS-17 content of 17.3 wt% promoted the efficient removal of a frozen ice column with a low ice adhesion strength of 78 kPa at −20.0 °C (70% relative humidity), which was 4.3 times smaller than that of an OPSZ-coated surface. The FPSZ-coated Al surface suppressed ice nucleation, leading to a decrease in ice nucleation temperature from −19.5 to −21.9 °C and a delay in freezing time from 334 to 4914 s at −19.0 °C compared with the OPSZ-coated Al surface. Moreover, after 40 icing–melting cycles the freezing temperature of a water droplet on the FPSZ-coated Al surface remained unchanged, whereas that on the FAS-17-coated Al surface increased from −22.3 to −20.7 °C. Therefore, the durability of the polymeric FPSZ coating was superior to that of the FAS-17 monolayer coating.

Copper Surface Treatment Method with Antibacterial Performance Using “Super-Spread Wetting” Properties

In this work, a copper coating is developed on a carbon steel substrate by exploiting the superwetting properties of liquid copper. We characterize the surface morphology, chemical composition, roughness, wettability, ability to release a copper ion from surfaces, and antibacterial efficacy (against Escherichia coli and Staphylococcus aureus). The coating shows a dense microstructure and good adhesion, with thicknesses of approximately 20–40 µm. X-ray diffraction (XRD) analysis reveals that the coated surface structure is composed of Cu, Cu2O, and CuO. The surface roughness and contact angle measurements suggest that the copper coating is rougher and more hydrophobic than the substrate. Inductively coupled plasma atomic emission spectroscopy (ICP-AES) measurements reveal a dissolution of copper ions in chloride-containing environments. The antibacterial test shows that the copper coating achieves a 99.99% reduction of E. coli and S. aureus. This study suggests that the characteristics of the copper-coated surface, including the chemical composition, high surface roughness, good wettability, and ability for copper ion release, may result in surfaces with antibacterial properties.

Surface wettability effect of plain and plasma-sprayed copper-coated surfaces on CHF enhancement during saturated pool boiling of FC-72

In the current scenario, CHF study is essential for the safe operation of electronics equipment comprising a two-phase heat transfer process. Therefore, the present experimental investigation involves saturated pool boiling and CHF study of FC 72 over a plain stainless steel surface (SS) and microporous copper-coated SS surfaces under atmospheric conditions. Accordingly, three different plasma-sprayed copper-coated surfaces with coating thicknesses of 65 μm, 105 μm, and 145 μm prepared using micro copper particles of size 25–45 μm. The analysis of the results shows that with an increase in heat flux values, the boiling heat transfer coefficient increases over plain as well as coated surfaces. The plasma-spayed copper-coated surfaces with a coating thickness of 65 μm and 105 μm exhibit a higher boiling heat transfer coefficient as than the plain surface. On the other hand, a 145 μm thick coated surface resulted in a comparable boiling heat transfer coefficient with the plain SS surface. Among the three porous-coated surfaces, the boiling heat transfer coefficient decreases continuously from 65 μm to 145 μm of the coated surface. On the contrary, to the observed nucleate boiling behavior, all the porous-coated surfaces show a higher value of CHF than the plain surface, and the CHF value is found to increase continuously from 65 μm to 145 μm of the coated surfaces. The enhancement of CHF values was found to be 66.29%, 69.17%, and 77.75% for a coating thickness of 65 μm, 105 μm, and 145 μm, respectively, compared with the plain surface. The porous coating thickness of 65 μm shows a greater value of heat transfer coefficient than 105 μm and 145 μm whereas 145 μm exhibits a higher value of CHF as than 65 μm and 105 μm.

Effect of Various Process Parameters of EDC on Mild Steel Substrate and their Properties

In the present study, A layer of the modified composite coated surface is made using Copper, molybdenum disulfide, and hexagonal boron nitride. For this process, Electrical discharge machine (EDM) is used but in reverse polarity. Various factors of the machine influenced the thickness of the deposited layer like the amplitude of peak current, duty factor, powder mixing ratio, used etc. For the deposition process, green compacted electrodes which was made after mixing the powder material in mortar for approximately 2.5 hour and post processing in Hot mount press moulding machine. After that the mixture powder was put in the Hot mounting press machine to made green compact electrode with specific parameters. Experiment was performed on EDM and many analysis were carried out to study the morphology of the coated surface. To get the morphology of the coated layer, FESEM images were examined and found the satisfying uniform distribution of deposited layer constituents with material powder mixing ratio of (Cu/HBN/MoS2) at (20/40/40) got with 50% duty factor and 10 Ampere peak current amplitude. Also done XRD, for the evidence of Cu, MoS2 and HBN.

Pressure influence on saturated boiling of R141b over Cu and Si-coated surfaces

Pool boiling has been a research topic of great interest over the decades due to its inherent capabilities of large heat transfer rates with narrow temperature gaps and it advocates its suitability in a large number of industrial applications. The present paper describes the effect of operating pressure on pool boiling of R141b over a plain Cu surface as well as Si-coated surface prepared by a direct current (DC) sputtering technique. The working fluid R141b undergoes saturated pool boiling under pressure ranging from −20 kPa(g) to + 30 kPa(g) with the acquired experimental data and trends compared with the existing correlations and theories. Within the pressure range considered, the surface superheat variation was insignificant at lower heat fluxes; however, at higher heat fluxes, the maximum reduction was found to be by 9.5°C and 14.8°C for the plain Cu surface and Si-coated surface, respectively, regarding the corresponding values of −20 kPa(g) pressure. With respect to the results under atmospheric conditions, at the pressure of + 30 kPa(g), a corresponding increase in heat transfer coefficient of 12.1% for the plain Cu surface and of 17.8% for a Si-coated surface was observed at a heat flux of 225 kW/m2 and 272 kW/m2, respectively. In comparison to the results under atmospheric pressure conditions, the accompanying augmentation in the critical heat flux was observed as 13.3% for the plain Cu and 21.2% for the Si-coated surfaces at a pressure of + 30 kPa(g). Based on the experimental data, a correlation is developed for predicting heat transfer coefficients within the given pressure range.

Pimpinellin Inhibits Collagen-induced Platelet Aggregation and Activation Through Inhibiting Granule Secretion and PI3K/Akt Pathway

Pimpinellin is a coumarin-like compound extracted from the root of Toddalia asiatica. Its effects on platelet function has not been investigated. This study found that pimpinellin pretreatment effectively inhibited collagen-induced platelet aggregation, but did not alter ADP- and thrombin-induced aggregation. Platelets pretreated with pimpinellin showed reduced α granule (CD62) level and secretion of dense granule (ATP release). Pimpinellin-treated platelets also exhibited decreased clot reaction and TxB2 production. Pimpinellin pretreatment suppressed adhesion and spreading of human platelets on the fibrinogen coated surface. Analysis of tail bleeding time of mice administered with pimpinellin (40 mg/kg) revealed that pimpinellin did not change tail bleeding time significantly, number of blood cells, and APTT and PT levels. Pimpinellin inhibited collagen-induced ex vivo aggregation of mice platelets. Immunoblotting results showed that pimpinellin suppressed collagen-induced phosphorylation of PI3K-Akt-Gsk3β and PKC/MAPK in platelets.

Finishing Properties of Poly Urethane Coating on Bleached and Ammonia Fumigated Mango Wood Surface

Aims: The impact of bleaching chemicals on the gloss and film thicknesses of poly urethane (PU) coated surface of mango wood (Mangifera indica) with ammonia fumigation and an exposure towards sunlight was investigated Study Design: Thirty six wood samples of size 10.6 cm (length) C 7.62 cm (width) were prepared from 2.5 cm thick kiln dried mango wood (Mangifera indica). Specimens were divided into six groups, each group having 6 samples for the study. Place and Duration of Study: The experiment was carried out in year 2016 at the Laboratory of Forest Product Division, Forest Research Institute, Dehradun, Uttarakhand, India. Methodology: All the samples were sanded with 80 grit size sand paper and coated with poly urethane. Two chemicals were used for bleaching purpose like an aqueous solution of oxalic acid (H2C2O4) was prepared with 30% concentration (by mixing 42.9 g of the solute in 100 ml of hot water) and a commercially available Hydrogen peroxide (H2O2) was used as such (30%). For the purpose of bleaching, these chemicals were applied on to the sanded surfaces using brush at room temperature. The bleached sample surfaces were allowed to dry before proceeding to the next step. The PU (Poly Urethane) coated samples were treated with ammonia fumigation before and after bleached with the two chemicals. Ammonia fumigation was carried out in a fumigation chamber for 24 hours for all the samples (except T1). Results: On exposure to natural sunlight for 60 hours, all the samples showed reduction in film thickness in PU coating but in a wide range of 2.8 % to 11.4%. The highest loss of coating thickness was shown by samples which were neither fumigated nor bleached. Among the fumigated samples, those bleached with oxalic acid resulted in high film thickness loss. Samples bleached with hydrogen peroxide after ammonia fumigation resulted in least film thickness reduction. Both ammonia fumigation and bleaching in general brought down the original gloss of poly urethane coating. The gloss value reduced as expected on exposure to sunlight. Bleaching by hydrogen peroxide prior to ammonia fumigation resulted in highest loss in gloss Conclusion: The un-fumigated and unbleached surface resulted in minimum gloss reduction due to long exposure to sunlight.