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    One-step fabrication of soft calcium superhydrophobic surfaces by a simple electrodeposition process
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    Abstract:
    A simple, one-step electrodeposition process was rapidly performed on a metal substrate to fabricate calcium superhydrophobic surfaces in an electrolyte containing calcium chloride (CaCl2), myristic acid (CH3(CH2)12COOH), and ethanol, which can avoid the intricate post-processing of surface treatment. The morphology and surface chemical compositions of the fabricated superhydrophobic surfaces were systematically examined by means of SEM, XRD, and FTIR, respectively. The results indicate that the deposited surfaces were mainly composed of calcium myristate, which can dramatically lower surface free energy. The shortest process for constructing a superhydrophobic surface is about 0.5 min, and the maximum contact angle of the as-prepared surfaces can reach as high as 166°, showing excellent superhydrophobicity. By adjusting the electrodeposition time, the structure of the cathodic surface transforms from the turfgrass structure, loose flower structures, larger and dense flower structures, secondary flower structures, and then into tertiary or more flower structures. The superhydrophobic surfaces showed excellent rebound performance with a high-speed camera. After a pressing force, their hardness increases, but the superhydrophobic performance is not weakened. Inversely, the bouncing performance is enhanced. This electrodeposition process offers a promising approach for large areas of superhydrophobic surfaces on conductive metals and strongly impacts the dynamics of water droplets.
    To study the effect of nanometer SiC particles(nano-SiCp) on microstructure and oxidation resistance of NiCoCrAlY coating,four kinds of NiCoCrAlY coatings with different contents of nano-SiCp were prepared on the surface of a Ni-based superalloy using laser cladding technology,and their microstructure and isothermal oxidation behaviors at 1050 °C were investigated.The influencing mechanisms of nano-SiCp were primarily discussed.The results show that the microstructure and oxidation resistance of the coatings with nano-SiCp were incoordinately improved compared with those of the coating without nanometer particles,in which the coating with 1.0 %(mass fraction) nano-SiCp displays the best performance.With the addition of nano-SiCp,not only the crystal habit of the bonding interface between coating and substrate was improved,but also the microstructure of cladding layer was refined.The refinement of cladding layer microstructure plays a very positive role in improving the oxidation resistance of the NiCoCrAlY coatings.
    Nanometre
    Cladding (metalworking)
    Isothermal process
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    Abstract Pure titanium and Ti-6Al-4V alloy powders are treated by a mechanical milling process, which is one of the severe plastic deformation processes. The mechanical milling enables to produce a nano-grain microstructure very easily and has been applied to many powder materials. The bimodal microstructure in those mechanically milled powders is composed of a nano-grain structure with a grain size of about 50 nm in the surface-near region and of a work-hardened microstructure in the core region of the powder. We applied the hot roll sintering process to pure titanium and to Ti-6Al-4V mechanically milled powders. These compacts have a hybrid microstructure that consists of nano-grain structure with grain sizes of 200 to 500 nm and a micron size meso-grain structure. The hybrid microstructure materials demonstrate enhanced mechanical properties compared to conventional materials.
    Titanium alloy
    Severe Plastic Deformation
    Citations (38)
    The 6061 Al alloy based composites reinforced with 10 vol% SiC whiskers were prepared by powder metallurgy with the powders having the different sizes, i.e. < $30{\mu}m$ and > $30{\mu}m$ The composites were subjected to equal channel angular pressing (ECAP) at various conditions and the microstructural changes during ECAP were examined In the composites SiC whiskers were clustered and randomly aligned. The clusters were relatively well distributed in the composite with the smaller initial powder size. After ECAP, the clusters were aligned parallel to flow direction and became smaller. In addition, the shape of clusters was changed from irregular to round. The microstructure of the ECAPed samples were compared with those of the conventionally hot-extruded composites. The uniform microstructure and enhanced microhardness could be obtained by using the powders having the smaller size, decreasing ECAP temperature and repeating ECAP.
    Powder Metallurgy
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    This study is aiming at controlling the microstructure of plasma sprayed Al2O3-TiO2 composite coatings using freeze granulated powders. As sprayed and sintered Al2O3 + 3wt%TiO2 powders were air plasma sprayed with industry process parameters and compared with a commercial powder. The resulting coatings were investigated with respect to powder flowability, porosity and microstructure of the granules. The results showed that microstructure and melting fraction in the coatings could be tailored with the freeze granulation process and heat treatment conditions.
    Granulation
    Powder coating
    Citations (4)