Above 170 degree water contact angle and oleophobicity of fluorinated graphene oxide based transparent polymeric films

Understanding and tuning the wettability of the surfaces are highly intriguing for various applications. The development of stable and transparent coatings over aluminium alloys and glass substrates for making them superhydrophobic and extended oleophobic (lower to the surface tension of 33.4 mN/m (coconut oil)) using a scalable and simple spray painting technique is demonstrated. Fluorinated graphene oxide (FGO, fluorine content of 34.4 atomic weight %), an atomically layered material, modified Polydimethylsiloxane (PDMS) polymer composite is used as the paint for the coatings. The coated filmswere studied for their surface and compositional features. A water contact angle (CA) of 173.7 degree (close to the highest ever reported water CA, 175degree) is achieved with 60 wt% FGO in PDMS, and the same showing a CA of 94.9degree with coconut oil, in conjunction with a low contact angle hysteresis (4degree). The work of adhesion with the amount of FGO is studied and the surface energy of FGO containing paints is calculated and compared with the bare paints using Zisman plot analysi

Effect of wettability and surface roughness on ice-adhesion strength of hydrophilic, hydrophobic and superhydrophobic surfaces

The anti-icing properties of hydrophilic, hydrophobic and superhydrophobic surfaces/coatings were evaluated using a custom-built apparatus based on zero-degree cone test method. The ice-adhesion reduction factor (ARF) of these coatings has been evaluated using bare aluminium alloy as a reference. The wettability of the surfaces was evaluated by measuring water contact angle (WCA) and sliding angle. It was found that the ice-adhesion strength on silicone based hydrophobic surfaces was ~ 43 times lower than compared to bare polished aluminium alloy indicating excellent anti-icing property of these coatings. Superhydrophobic coatings displayed poor anti-icing property in spite of their high water repellence. Field Emission Scanning Electron Microscope reveal that Silicone based hydrophobic coatings exhibited smooth surface whereas the superhydrophobic coatings had a rough surface consisting of microscale bumps and protrusions superimposed with nanospheres. Both surface roughness and surface energy play a major role on the ice-adhesion strength of the coatings. The 3D surface roughness profiles of the coatings also indicated the same trend of roughness. An attempt is made to correlate the observed ice-adhesion strength of different surfaces with their wettability and surface roughness. It was concluded that smooth surface with low surface energy are responsible for low ice-adhesion strength

Fabrication of Superhydrophobic and Oleophobic sol–gel Nanocomposite coating

Superhydrophobic sol–gel nanocomposite coatings with improved oleophobic property were obtained by incorporation of a perfluoroalkylmethacrylic copolymer in a hybrid sol–gel matrix containing fumed silica nanoparticles. The coatings exhibited a water contact angle (WCA) of 158° and contact angle of 146° for ethylene glycol and 113° for lubricant oil. Though the sol–gel nanocomposite coatings in the absence of fluoropolymer were superhydrophobic with WCA of 155°, they were oleophilic with oil contact angle of b10°. The enhanced oleophobicity can be attributed to the further lowering of surface energy by the presence of fluoropolymer. FESEM images of the coating showed a highly porous structure with random distribution of aggregates of silica nanospheres. The coatings were characterized using FTIR, EDX and XPS. These studies indicated adsorption of fluoropolymer on the coating surface. The method is simple and cost-effective and can be used for preparing multifunctional water- and oil-repellent self-cleaning coatings on large areas of different kinds of substrates like glass, metal an

Invasive Alien Flora of Thiruvallur District, Tamil Nadu, India

Abstract: A qualitative floristic survey conducted in Thiruvallur district to record alien invasive flora. This study recorded 136 species in 90 genera and 37 families. The most speciose family of study area is Asteraceae (with 18 species), Convolvulaceae (11), Caesalpiniaceae (9) and Amaranthaceae (8). While 12 families which include Apocynaceae, Balsaminaceae, Cactaceae, Liliaceae were represented by just single species' in study area. Among genera, Cassia with 9 species dominated the study area followed by Ipomoea (7) and Indigofera (5). Eighty-nine species from tropical America, 19 from tropical Africa and 6 from tropical South America invaded into Thiruvallur district, Tamil Nadu, India. Of eight life forms herb represented with 95 species followed by shrub and under-shrub (11 species each). Study that concentrates on quantitative analysis is essential to assess the impact of invasive alien species on native flora of Thiruvallur district

Effect of ageing and FAS modification on the wettability of anodized Al alloy

Micro-nano porous oxide layer was developed on AA2024 by phosphoric acid anodization process (PAAO). A low surface energy material (Fluoroalkylsilane-13) was applied on the developed oxide layer in order to reduce the wettability of the surface. The FAS modified surface exhibited hydrophobic with water contact angle of about 1300 and sliding angle of greater than 900. The structural changes of PAAO during natural ageing improved the hydrophobic property of the surface. The surface morphology analyzed by field emission scanning electron microscopy (FESEM) showed that the FAS coating was uniform and intact to the developed oxide layer. The AFM results revealed that there was about 30% decrease in Ra value after 30 days of natural ageing compared to freshly modified surface. This variation in the nanometer scale roughness due to the natural aging of PAAO caused the surface to superhydrophobic (SH) (WCA-1600 and sliding angle <50). Similar SH property had also been achieved by artificial ageing (vacuum heat treatment at 80°C for 1 h). Composition analysis by energy dispersive X-ray analysis (EDAX) revealed that the amounts of F and Si were higher in the case of vacuum heat treated specimen compared to the naturally aged. The potentiodynamic polarization experiments were conducted in 3.5% NaCl solution and the results were discussed

Effect of Anodized Oxide Layer Aging on Wettability of Alkyl Silane Coating Developed on Aerospace Aluminum Alloy

Incipient nanoporous texture was developed by phosphoric acid anodization (PAAO) process on AA2024 specimen. The developed oxide layer was modified with low surface energy material fluoroalkyl-silane (FAS-13) by simple immersion technique to improve the hydrophobic property of the surface. Atomic force microscopy results showed that there was a significant reduction (30 pct) in surface roughness due to the aging of PAAO. The water contact angle measurement revealed that there was a gradual increase in WCA from 130 to 160 deg due to the aging of PAAO. A systematic composition analysis was carried out to understand the interfacial chemical reaction and also to differentiate the coating formation mechanism between the natural and artificial aging processes. The potentiodynamic polarization results revealed that the superhydrophobic (SH) surface exhibited about 15 and 4 times improved corrosion resistance compared to bare specimen and PAAO, respectively. Electrochemical impedance spectroscopy results also showed the improved corrosion inhibition behavior of vacuum heat-treated and FAS-modified SH surface among the developed coatings

Three finger palpation technique of vas deferens for keyhole vasectomy in spotted (Axis axis) and sambar deer (Cervus unicolor)

Aim: Vasectomy is performed in deer for population control, maintain pedigreed animals and prevent inbreeding. Conventional procedure of vasectomy required a long-term anesthesia and longer duration of hospitalization, which often result in stress, morbidity and mortality. A study was conducted to capture, neuter and release the deer with minimal hospitalization and stress by adopting three finger palpation technique of vas deferens and performing vasectomy through a key-hole incision. Materials and Methods: The study was conducted on three spotted male deer and three sambar male deer, which were immobilized with a mixture of xylazine at the dose of 1.00 mg/kg and ketamine at the dose of 5.00 mg/kg. The vas deferens could be palpated as a piece of cooked spaghetti at the neck of the scrotum on the anterior aspect by three finger palpation technique and was able to fix the vas deferens between the thumb and middle finger. Through a key-hole incision of <5 mm length, the vas deferens was exteriorized and resected using electrocautery and the skin incision was sealed with methyl methacrylate. The deer were released on the same day, and no post-operative complication was noticed. Conclusion: The study revealed that three finger palpation technique of vas deferens provided guidance for easy access to vas deferens for vasectomy in deer with less hospitalization, and the deer could be released on the same day

Zinc Oxide-Containing Porous Boron–Carbon–Nitrogen Sheets from Glycine–Nitrate Combustion: Synthesis, Self-Cleaning, and Sunlight-Driven Photocatalytic Activity

We developed a single-step thermal method that enables successful inclusion of ZnO components in the porous boron–carbon–nitrogen (BCN) framework to form a new class of functional hybrid. ZnO-containing BCN hybrids were prepared by treating a mixture of B₂O₃, glycine, and zinc nitrate at 500 °C. Glycine–nitrate decomposition along with B₂O₃ acts as a source for ZnO-BCN formation. The incorporation of ZnO onto BCN has extended the photoresponse of ZnO in the visible region, which makes ZnO-BCN a preferable photocatalyst relative to ZnO upon sunlight exposure. It is interesting to note that as-prepared 2D ZnO-BCN sheets dispersed in PDMS form a stable coating over aluminum alloys. The surface exhibited a water contact angle (CA) of 157.6° with 66.6 wt % ZnO-BCN in polydimethylsiloxane (PDMS) and a water droplet (7 μL) roll-off angle of <6° and also demonstrates oil fouling resistant superhydrophobicity. In brief, the present study focuses on the gram scale synthesis of a new class of sunlight-driven photocatalyst and also its application toward the development of superhydrophobic and oleophobic coating