SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Coatings

29

The static and dynamic wetting properties of a 3D graphene foam network are reported. The foam is synthesized using template-directed chemical vapor deposition and contains pores several hundred micrometers in dimension while the walls of the foam comprise few-layer graphene sheets that are coated with Teflon. Water contact angle measurements reveal that the foam is superhydrophobic with an advancing contact angle of ∼163 degrees while the receding contact angle is ∼143 degrees. The extremely water repellent nature of the foam is also confirmed when impacting water droplets are able to completely rebound from the surface. Such superhydrophobic graphene foams show potential in a variety of applications ranging from anti-sticking and self-cleaning to anti-corrosion and low-friction coatings.

Concepts: Water, Wetting, Surface tension, Chemical vapor deposition, Angle, Contact angle, Coatings, Sessile drop technique

28

Flame-retardant and self-healing superhydrophobic coatings are fabricated on cotton fabrics by a convenient solution dipping method, which involves the sequential deposition of a trilayer of branched poly(ethylenimine) (bPEI), ammonium polyphosphate (APP) and fluorinated-decyl polyhedral oligomeric silsequioxane (F-POSS). When directly exposed to flame, such a trilayer coating generates a porous char layer because of its intumescent effect, successfully endowing the coated fabric with self-extinguishing property. Meanwhile, the preserved F-POSS in cotton fabrics and APP/bPEI coating produce a superhydrohobic surface with self-healing function. The coating can repetitively and autonomically restore superhydrophobicity once the superhydrophobicity is damaged. The resultant cotton fabrics, which are flame resistant, waterproof and self-cleaning, can be readily cleaned with simple water rinsing. Thus, the integration of self-healing superhydrophobicity with flame-retardancy provides a practical way to solve the problem regarding the washing durability of the flame-retardant coatings. The flame-retardant and superhydrophobic fabrics can endure more than 1000 cycles of abrasion under a pressure of 44.8 kPa without losing its flame-retardancy and self-healing superhydrophobicity, showing potential applications as multifunctional advanced textiles.

Concepts: Cotton, Geology, Coating, Textile, Yarn, Coatings, Brominated flame retardant, Tent

28

AIM: The first aim of the present experiment was to compare bone healing at implants installed in recipient sites prepared with conventional drills or a piezoelectric device. The second aim was to compare implant osseointegration onto surfaces with and without dendrimers coatings. MATERIAL AND METHODS: Six Beagles dogs were used in this study. Five implants with two different surfaces, three with a ZirTi(®) surface (zirconia sand blasted, acid etched), and two with a ZirTi(®) -modified surface with dendrimers of phosphoserine and polylysine were installed in the right side of the mandible. In the most anterior region (P2, P3), two recipient sites were prepared with drills, and one implant ZirTi(®) surface and one coated with dendrimers implants were installed at random. In the posterior region (P4 and M1), three recipient sites were randomly prepared: two sites with a Piezosurgery(®) instrument and one site with drill and two ZirTi(®) surface and one coated with dendrimers implants installed. Three months after the surgery, the animals were sacrificed for histological analysis. RESULTS: No complications occurred during the healing period. Three implants were found not integrated and were excluded from analysis. However, n = 6 was obtained. The distance IS-B at the buccal aspect was 2.2 ± 0.8 and 1.8 ± 0.5 mm, while IS-C was 1.5 ± 0.9 and 1.4 ± 0.6 mm at the Piezosurgery(®) and drill groups, respectively. Similar values were obtained between the dendrimers-coated and ZirTi(®) surface implants. The BIC% values were higher at the drill (72%) compared to the Piezosurgery(®) (67%) sites. The BIC% were also found to be higher at the ZirTi(®) (74%) compared to the dendrimers-coated (65%) implants, the difference being statistically significant. CONCLUSION: This study has revealed that oral implants may osseointegrate equally well irrespective of whether their bed was prepared utilizing conventional drills with abundant cooling or Piezosurgery(®) . Moreover, the surface coating of implants with dendrimers phosphoserine and polylysine did not improve osseointegration.

Concepts: Implants, Coating, Dental implant, Osseointegration, Implant, Piezoelectricity, Coatings, Per-Ingvar Brånemark

28

Long lasting anticorrosive coatings for steel have been developed based on halloysite nanotubes loaded with three corrosion inhibitors: benzotriazole, mercaptobenzothiazole and mercaptobenzimidazole. The inhibitors' loaded tubes were admixed at 5-10 wt % to oil based alkyd paint providing sustained agent release and corrosion healing in the coating defects. Slow 20-30 hour release of the inhibitors in defect points caused remarkable improvement in anticorrosion efficiency of the coatings. Further time expansion of anticorrosion agents release has been achieved by formation of release stoppers at nanotube-ends with urea-formaldehyde copolymer and copper-inhibitor complexation. Corrosion protection efficiency was tested on ASTM A366 steel plates in 0.5 M NaCl solution with microscanning of corrosion current development, by microscopy inspection and studying paint adhesion. The best protection was found using halloysite / mercaptobenzimidazole and benzotriazole inhibitors. Stopper formation with urea-formaldehyde copolymer provided additional increase in corrosion efficiency due to longer release of inhibitors.

Concepts: Sodium chloride, Coating, Agent, Coatings, Passivation, Corrosion, Paint, Formulations

28

An electrostatic dry coating process based on a liquid pan coater was developed for enteric coating of tablets with Eudragit(®) L100-55. Two different liquid plasticizers of triethyl citrate (TEC) and PEG400 were used in the coating process. In contrast to TEC, PEG400 produced good powder adhesion and successful coating. DSC results showed that PEG 400 lowered the glass transition temperature (T(g)) of Eudragit(®) L100-55 to a greater extent than TEC at the same blend ratio, indicating that PEG400 was more effective in plasticizing the polymer. PEG 400 showed higher contact angle on both surfaces of tablet cores and coating powders as well as lower absorption into the tablet cores than TEC, suggesting that more PEG400 existed at the interface between tablet core and coating powders. The combination effects of higher plasticizing efficiency and more PEG400 available at the tablet surface produced higher plasticization of Eudragit(®) L100-55, leading to the successfully initial powder adhesion. The powder adhesion was further enhanced by the electrostatically assisted coating process, as confirmed by the higher coating level and coating efficiency with electrical charging (60 kV) than the ones without it (0 kV). The micrographs of scanning electron microscopy and in vitro drug release tests of the coated tablets showed that higher curing temperature and longer curing time led to enhanced film formation and acid resistance. The electrostatic dry coating process has been demonstrated to be a promising process for enteric coating of tablets.

Concepts: Electron, Pharmacology, Liquid, Differential scanning calorimetry, Scanning electron microscope, Glass transition, Coatings, Plasticizer

26

Practical application of sol-gel derived superhydrophobic films is limited by the fragility of “needlelike” surface roughness. An efficient one step procedure is developed to prepare robust thin films with “craterlike” surface roughness from a methyltrimethoxysilane matrix and polymer sphere templates. The films could be readily spray coated to produce roughened surface textures, which are governed by template concentration and geometry. The effect of this on the wettability and robustness of thin films was examined in detail, revealing a rapid trade-off between the two characteristics due to variations in coating porosity.

Concepts: Coating, Differential geometry, Coatings

5

Prompted by the rapidly developing field of wearable electronics, research into biocompatible substrates and coatings is intensifying. Acrylate-based hydrogel polymers have gained widespread use as biocompatible articles in applications such as contact and intraocular lenses. Surface treatments and/or coatings present one strategy to further enhance the performance of these hydrogels, or even realise novel functionality. In this study, the conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is deposited from the vapour phase onto hydrated hydrogel substrates and blended with biocompatibilising co-constituents incorporating polyethylene glycol (PEG) and polydimethyl siloxane (PDMS) moieties. Plasma pre-treatment of the dehydrated hydrogel substrate modifies its surface topography and chemical composition to facilitate the attachment of conductive PEDOT-based surface layers. Manipulating the vapour phase polymerisation process and constituent composition, the PEDOT-based coating is engineered to be both hydrophilic (ie. to promote biocompatibility) and highly conductive. The fabrication of this conductively coated hydrogel has implications for the future of wearable electronic devices.

Concepts: Electricity, Polymer, Coating, Polyethylene, Electronics, Coatings, Silicone, Polymers

4

A limitation of aspirin is that some patients, particularly those with diabetes, may not have an optimal antiplatelet effect.

Concepts: Coatings

3

Prevention of microbially induced corrosion (MIC) is of great significance in many environmental applications. Here, we report the use of an ultra-thin, graphene skin (Gr) as a superior anti-MIC coating over two commercial polymeric coatings, Parylene-C (PA) and Polyurethane (PU). We find that Nickel (Ni) dissolution in a corrosion cell with Gr-coated Ni is an order of magnitude lower than that of PA and PU coated electrodes. Electrochemical analysis reveals that the Gr coating offers ~10 and ~100 fold improvement in MIC resistance over PU and PA coatings respectively. This finding is remarkable considering that the Gr coating (1-2 nm) is ~25 and ~4000 times thinner than the PA (40-50 nm), and PU coatings (20-80 μm), respectively. Conventional polymer coatings are either non-conformal when deposited or degrade under the action of microbial processes, while the electro-chemically inert graphene coating is both resistant to microbial attack and is extremely conformal and defect-free. Finally, we provide a brief discussion regarding the effectiveness of as-grown vs. transferred graphene films for anti-MIC applications. While the as-grown graphene films are devoid of major defects, wet transfer of graphene is shown to introduce large scale defects that make it less suitable for the current application.

Concepts: Electrochemistry, Antibiotic resistance, Metal, Coating, Coatings, Corrosion

3

Hexagonal boron nitride is a two-dimensional layered material that can be stable at 1,500 °C in air and will not react with most chemicals. Here we demonstrate large-scale, ultrathin, oxidation-resistant coatings of high-quality hexagonal boron nitride layers with controlled thicknesses from double layers to bulk. We show that such ultrathin hexagonal boron nitride films are impervious to oxygen diffusion even at high temperatures and can serve as high-performance oxidation-resistant coatings for nickel up to 1,100 °C in oxidizing atmospheres. Furthermore, graphene layers coated with a few hexagonal boron nitride layers are also protected at similarly high temperatures. These hexagonal boron nitride atomic layer coatings, which can be synthesized via scalable chemical vapour deposition method down to only two layers, could be the thinnest coating ever shown to withstand such extreme environments and find applications as chemically stable high-temperature coatings.

Concepts: Chemistry, Nitrogen, Chemical substance, Chemical element, Layer, Coating, Coatings, Boron nitride