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Telomeres of Tetrafluoroethylene - Advanced Materials to Create Superhydrophobic Coatings and Optical Fiber with Low Attenuation Coefficient  [cached]
Shestakov A.F.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2013,
Abstract: The paper describes formation of telomers of tetrafluoroethylene (TFE), which are very interesting intermediate materials of different purposes, by radiation polymerization. In some cases there are formed long chained oligomers suitable for creation of superhydrophobic coatings. In such systems formation of gels is observed under low TFE content. Quantum chemical analysis allows to reveal the factors that are responsible for this phenomenon. In the case of solvents with appropriate cyclic structure, short chain oligomers, which have low C-H bonds content, are raw materials for fluoropolymers suitable for manufacturing optical fibers. The work is aimed to predict which types of materials are formed under polymerization conditions. For these purposes the generalized Polany-Semenov rule is used. Its parameters found by DFT calculations can be recommended for practical applications in the molecular design of new fluorine-containing polymers.

ZHANG Ergeng,LONG Kang,WANG Zhiwen East China University of Science,Technology,Shanghai,Institute of Metal Research,The Chinese Academy of Sciences,Shenyang,

腐蚀科学与防护技术 , 2002,
Abstract: Corrosion perfomance of three kind of coatings,i.e. the PPS based coatings filled with microsized-(normal coating) or nanosized pigments(nanocomposite) and the later one plus a post treatment with a surfactant of fluorine(hydrophobic nanocomposite coating),was investigated by means of electrochemical impedance spectroscopy(EIS) mesearement.The results show that the nanocomposite coating showed better corrosion resistance than the normal ones.However,the hydrophobic nanocomposite coatings showed the best corrosion resistance,which may be owed to the beneficial effect induced by the treatment with surfactant of fluorine.
Synthesis and Characterization of Superhydrophobic-Superoleophobic and Anti-Corrosion Coatings via Sol-Gel Process  [PDF]
Mohammad Reza Heshmati, Sahar Amiri, Maryam Hosseini-Zori
Open Journal of Organic Polymer Materials (OJOPM) , 2020, DOI: 10.4236/ojopm.2020.101001
Abstract: Superoleophobic nanocomposite coatings with improved hydrophobic properties were obtained by incorporation of a perfluoroalkyl polymer in hybrid sol-gel matrix containing silica and titania nanoparticles. SiO2 and TiO2 nanoparticles were synthesized based on sol-gel precursors utilizing tetraethyl orthosilicate, 3-glycidoxypropyl trimethoxysilane, and tetra (n-butyl orthotitanate). SEM and EDX images of the coating demonstrated that a Silica nanosphere had been aggregated in superporous structure. The analysis results show that nano-sized inorganic particles (10 - 20 nm) have a uniform distribution and dispersion. By increasing the PFOTES, the oleophobicity of coatings increased due to lowering of surface energy in the presence of fluoropolymer. Results of EIS measurement show that PFOTES and TiO2 nanoparticles increased anti-corrosion property of hybrid coatings. This method introduces a simple way to produce water- and oil-repellent self-cleaning coatings on large areas of different substrates like glass, ceramic, metal and composites.
Superhydrophobic Surface Based on a Coral-Like Hierarchical Structure of ZnO  [PDF]
Jun Wu,Jun Xia,Wei Lei,Baoping Wang
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014475
Abstract: Fabrication of superhydrophobic surfaces has attracted much interest in the past decade. The fabrication methods that have been studied are chemical vapour deposition, the sol-gel method, etching technique, electrochemical deposition, the layer-by-layer deposition, and so on. Simple and inexpensive methods for manufacturing environmentally stable superhydrophobic surfaces have also been proposed lately. However, work referring to the influence of special structures on the wettability, such as hierarchical ZnO nanostructures, is rare.
Preparation and characterization of superhydrophobic surfaces based on hexamethyldisilazane-modified nanoporous alumina  [cached]
Tasaltin Nevin,Sanli Deniz,Joná? Alexandr,Kiraz Alper
Nanoscale Research Letters , 2011,
Abstract: Superhydrophobic nanoporous anodic aluminum oxide (alumina) surfaces were prepared using treatment with vapor-phase hexamethyldisilazane (HMDS). Nanoporous alumina substrates were first made using a two-step anodization process. Subsequently, a repeated modification procedure was employed for efficient incorporation of the terminal methyl groups of HMDS to the alumina surface. Morphology of the surfaces was characterized by scanning electron microscopy, showing hexagonally ordered circular nanopores with approximately 250 nm in diameter and 300 nm of interpore distances. Fourier transform infrared spectroscopy-attenuated total reflectance analysis showed the presence of chemically bound methyl groups on the HMDS-modified nanoporous alumina surfaces. Wetting properties of these surfaces were characterized by measurements of the water contact angle which was found to reach 153.2 ± 2°. The contact angle values on HMDS-modified nanoporous alumina surfaces were found to be significantly larger than the average water contact angle of 82.9 ± 3° on smooth thin film alumina surfaces that underwent the same HMDS modification steps. The difference between the two cases was explained by the Cassie-Baxter theory of rough surface wetting.
Flow in channels with superhydrophobic trapezoidal textures  [PDF]
Tatiana V. Nizkaya,Evgeny S. Asmolov,Olga I. Vinogradova
Physics , 2013, DOI: 10.1039/C3SM51850G
Abstract: Superhydrophobic one-dimensional surfaces reduce drag and generate transverse hydrodynamic phenomena by combining hydrophobicity and roughness to trap gas bubbles in microscopic textures. Recent works in this area have focused on specific cases of superhydrophobic stripes. Here we provide some theoretical results to guide the optimization of the forward flow and transverse hydrodynamic phenomena in a parallel-plate channel with a superhydrophobic trapezoidal texture, varying on scales larger than the channel thickness. The permeability of such a thin channel is shown to be equivalent to that of a striped one with greater average slip. The maximization of a transverse flow normally requires largest possible slip at the gas areas, similarly to a striped channel. However, in case of trapezoidal textures with a very small fraction of the solid phase this maximum occurs at a finite slip at the gas areas. Exact numerical calculations show that our analysis, based on a lubrication theory, can also be applied for a larger gap. However, in this case it overestimates a permeability of the channel, and underestimates an anisotropy of the flow. Our results provide a framework for the rational design of superhydrophobic surfaces for microfluidic applications.
Microstructural control of Co-based PTA coatings
Gomes, Rafael;Henke, Sérgio;D′Oliveira, Ana Sofia;
Materials Research , 2012, DOI: 10.1590/S1516-14392012005000099
Abstract: cobalt-based alloys are widely used as hardfacing materials when wear resistance is required at room temperature or high temperature applications. however, their performance is a consequence of their microstructures that depends on the processing conditions. this work focused on the influence of solidification rate on the structure development by processing the alloys with and without the interference of the substrate. the coatings were characterized by scanning electron microscopy, energy dispersive spectrometer, optical microscopy and instrument indentation tests. results showed that despite the same phases developed in tested conditions, differences in the solidification microstructure and the influence of fe diffusing from the substrate accounted for the measured variation in hardness. higher hardness values were obtained for the samples processed free-standing (mini billets) with respect to the coatings and they were independent of the processing parameters, indicating that the substrate compromise the properties of hardness, as expected.
Predicting properties of PVD and CVD coatings based on fractal quantities describing their surface  [PDF]
W. Kwa?ny
Journal of Achievements in Materials and Manufacturing Engineering , 2009,
Abstract: Purpose: The goal of the presented study was to develop a methodology giving a possibility to predict functional properties of coatings obtained in the PVD and CVD processes on tool materials, based on fractal- and multi-fractal quantities describing their surface.Design/methodology/approach: Effect of process type and deposition conditions on structure and shape of surface, as well as mechanical and service properties of the obtained coatings were determined. Methodology and detailed description of coatings topography obtained in PVD and CVD process on tool materials, including use of the fractal- and multi-fractal geometry based on images obtained on the atomic forces microscope were worked out. Relationships between fractal- and multi-fractal quantities and their mechanical and service properties were determined.Findings: The investigation results confirmed the feasibility to predict hardness and erosion resistance of coatings obtained in the magnetron PVD process, as well as the service properties defined in the cutting ability test for coatings obtained in the arc PVD process and in the high-temperature CVD process, based on the surface fractal dimension Ds value for their surface topography.Practical implications: Determining significant quantitative correlations between fractal quantities defining coatings’ surfaces, as well as their service and/or mechanical properties provides the opportunity to predict their end-user properties.Originality/value: Fractal analysis was applied for characterization of PVD and CVD coatings surfaces.
Effect of palladium diffusion in coatings deposited on the nickel based superalloy  [PDF]
M. Zagula-Yavorska,J. Sieniawski
Archives of Materials Science and Engineering , 2011,
Abstract: Purpose: In this paper the effect of palladium diffusion in coatings deposited on the surface of nickel based superalloy was evaluated.Design/methodology/approach: The palladium coatings 3 and 7 μm thick were deposited by the electroplating process on Inconel 713 LC Ni-base superalloy. The heat treatment of electroplated coatings at the temperature 1050°C for 2 h under argon atmosphere was performed. The microstructure investigations of the heat treated coatings were conduced by the use of optical microscope (Nikon Epiphot 300) and a scanning electron microscope (Hitachi S-3400N) equipped with an Energy Dispersive Spectroscope EDS (VOYAGER of NORAN INSTRUMENTS). The phase composition was identified by X-ray (ARL X’TRAX) diffractometer. The surface roughness parameter - Ra of heat treated coatings was evaluated by Perthometer S2 MAHR equipment.Findings: The microstructure of 3 μm thick palladium electroplated coating after diffusion treatment consists of three phases: AlPd2, Ni3Al, Ni0,52Pd0,475. The increase of palladium thickness from 3 to 7 μm does not influence the phase composition of heat treated coatings. Heat treatment of palladium electroplating coatings increases the surface roughness parameter Ra.Research limitations/implications: The results will be used in the future investigations to explain the influence of palladium on the oxidation resistance of aluminide coatings.Practical implications: The palladium electroplating coatings after heat treatment and aluminizing process may be used as an alternative to platinum modified aluminide coatings as coatings for turbine blades of aircraft engines.Originality/value: The paper includes the results of microstructure and surface roughness investigations of palladium electroplating coatings 3 and 7 μm thick after diffusion treatment. Inconel 713 LC; Palladium electroplating; Diffusion treatment; Surface roughness
Zita I?dinská,Ahmed Nasher,Karol I?dinsky
Materials Engineering , 2010,
Abstract: In this work, the influence of the processing conditions on the microstructure and abrasive wear behavior of composite laser clad coatings with Ni based matrix reinforced with 50% WC particles is analyzed. Composite powder was applied in the form of coatings onto a mild steel substrate (Fe–0.17% C) by different laser powers and cladding speeds. The microstructure of the coatings was analyzed by scanning electron microscopy (SEM). Tribological properties of coatings were evaluated by pin-on-disc wear test. It appeared that the hardness of the matrix of composite coatings decreases with increasing cladding speed. However, wear resistance of composite coatings with decreasing hardness of Ni based matrix increases. Significantly enhanced wear resistance of WC composite coatings in comparison with Ni based coatings is attributed to the hard phase structures in composite coatings.
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