Papers by Keyword: Coating

Abstract: Laser cladding, as an effective method of metal surface modification, is to fuse an alloy coating of enhanced mechanical and chemical properties on the surface of a substrate. Therefore, laser cladding has been attracting continuous and extensive research for years. In this paper, the research progress in laser clad cobalt-based alloys is summarized. The preparing processes, microstructures, properties and influence factors of laser clad cobalt-based alloys coatings and their ceramic particles strengthened composites coatings are analyzed systematically. And the existing problems, some solving measures, the development tendencies and industral uses are presented.

Abstract: Titanium and titanium alloys possess some attractive properties, such as excellent corrosion and erosion resistance, low densities, high specific strength and modulus, enabling them extensively used in aeronautical, marine, chemical and biomedical applications and so on. Nevertheless, Recent years, the corrosion resistance of titanium and titanium alloys is required to elevate in some fields, proper surface modification such as surface oxidation can solve the problems effectively. In this paper, the recent investigations of thermal oxidation and micro-arc oxidation to improve the corrosion resistant of titanium and its alloys are reviewed. The structures, properties and their influence factors of the coatings are analysed systematically. And the existing problems and the future prospect of the further researches is mentioned.

Abstract: Titanium and titanium alloys are widely used in aeronautical, marine, chemical and biomedical applications and so on, owing to their specific properties such as good corrosion resistance, low densities, high specific strength and modulus, and high-temperature resistance. However titanium and titanium alloys also have many disadvantages, such as low hardness, low wear-resistance and the low corrosion-resistance in some cases, which limit their wider application. Recent years, the corrosion resistance of titanium and titanium alloys is required to elevate in some fields. Proper surface modification can solve the problems effectively. This paper reviews the recent investigations of laser surface modification to improve the corrosion resistant of titanium and its alloys. The microstructures, the corrosion resistance properties, and the influence factors of the coatings were discussed systematically. And the future prospect of the further researches and uses is presented.

Abstract: Electrophoretic deposition is proposed to fabricate super-hydrophobic film on copper surface with reduced graphene sheets (RGSs). The resulted film was characterized with contact angle meter, scanning electron microscopy and so on. It is found that the film presents super-hydrophobic property with water contact angle of 150.4°. Air can be trapped in the island-like structure and intensify the wettability of film. Electrochemical measurements prove that super-hydrophobic film can inhibit corrosion process of underlying copper by inducing both anodic and cathodic current density. This method for super-hydrophobic film fabrication is facial and time-saving, and it will expand the application of RGSs in mechanical engineering.

Abstract: Separator shutdown by interrupting the transmission of lithium ions to terminate the battery reaction is a valid safety mechanism for preventing thermal runaway reactions in lithium ion batteries. Yet the cell temperature continues rising after the shutdown, the separator need sufficient thermal stability to physically isolate the electrodes. To reduce the thermal shrinkage of polyethylene (PE) separators, a fresh composite separator is developed by introducing alumina (Al₂O₃) nanoparticles/waterborne polyurethane (WPU) layer on one side of the pristine PE separator via casting process. The microporous structure of the composite separator is supposed to be a significant consideration for the cell performance, which is confirmed by the scanning electron microscope. Compared with the pristine PE separator, the thermal shrinkage of the novel separator improved markedly with an acceptable decline in air permeability and ion conductivity.

Abstract: There is a large variety of techniques available to protect metals from various types of corrosion. Till date chromate containing metal coatings is one of the most commonly used methods. Layered clays are basically of two types depending on the type of ion exchange capacity. In the recent years different researchers demonstrated the use of such cation/ anionic clays as potential nanocontainers for the inhibitors. These nanocontainers can be used in the coating to induce self-repairing capacity when the coating surface is damaged. Due to the disturbance in the pH and availability of chloride ions clay based nanocontainers can release the inhibitor to protect the surface. In the recent year use of anionic clay like hydrotalcites or layered double hydroxides are much studied in comparison to cationic clay like montmorillonite. This review critically analysed the potential of these clay in the future development of self-healing coating.

Abstract: In the present study, coatings of aluminium, zinc and combinations of aluminium-zinc and zinc-nickel were applied to steel substrates using the cold gas spray process. The effects of powder morphology and impact velocity, as determined by gas temperature and pressure, on the uniformity of the coatings were investigated. The through coating microstructure and composition were examined using scanning electron microscopy to determine the elemental distribution and the nature and extent of porosity. Work continues with an investigation of substrate condition and spray parameters on deformation and bonding. Significant plastic deformation of metal grains was evident. Further, it was revealed that the uniformity and compactness of the coatings are directly associated with the shape and size of the powders, and the gas pressure and temperature. The performance of the coatings is currently being evaluated and compared with ion vapour deposited and electrodeposited coatings.

Abstract: This research developed and optimized the methods for simultaneous determination of tetracycline (TCs), macrolide (MLs) and sulfonamide (SAs) antibiotics in soils using accelerated solvent extraction (ASE)- solid-phase extraction (SPE)-high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Methanol-citric acid (pH=4.7) was used as extraction solvent, diatomite (washed by EDTA) was used as dispersing agent. Firstly, soil was extracted by ASE with the parameter conditions: pressure 1500 psi, temperature 70°C, static 10 min, 1 circle, then pre-concentration by SPE and followed by HPLC-MS/MS analysis. Recovery was 86.3%~97.4% for SAs, 67.3%~87.4% for TCs and 68.4%~78.3% for MLs. RSD < 9 % and r > 0.99. Limits of detection (LOD) was 0.5~0.9 ug/kg for SAs, 0.2~1.1 ug/kg for TCs and 0.2~0.3 ug/kg for MLs. This method determined 9 kinds of antibiotics within 15 min, the determination accuracy can meet the requirements of actual analysis.

Abstract: Titanium dioxide was coated onto buoyant polypropylene granules. Titanium dioxide coated polypropylene granules (TCPG) had high mechanical and attritional stability as well as appreciable photocatalytic activity under solar irradiation. Chosen model pollutant, Methylene Blue (MB) could be totally decolorized and partially mineralized within 3 h of treatment. TCPG might successfully be applied as suspended in the column flow-through system. Degradation rates depended strongly on pH, initial dye concentration, and optimal media dosage, following pseudo-first-order kinetic model.

Abstract: This work consisted in the development and characterization of a bioactive coating on Ti6Al4V samples by flame spray projection. A synthetichidroxyapatite powder was used to form the coatings. Oxygen and acetylene gas were used as combustible, and the metallic substrate was Ti6Al4V with a roughness of 0.4 and 2.3 μm. The time process varied from 5 to 60 seconds. The projection distance was of 22 cm.The spray coatings were mechanical tested; in all cases, the results indicated that the coatings were well adhered to the metallic surfaces and the metallic subtracts did not present any degradation of the mechanical properties. In addition, the coatings were immersed in simulated body fluids for 21 days in physiological conditions to evaluate the bioactivity. The results demonstrated that the coatings are potentially bioactive through the formation of a dense and homogeneous apatite layer similar to the bone. Results of X-ray diffraction exhibited evidence of a hidroxyapatite layer and by energy dispersive spectroscopy, a Ca/P ratio of 1.57 was obtained. This is an indication of that the use of flame spray projection to coat Ti6Al4V substrates do not decompose the original hidroxyapatite powder. Compositional analysis of the remnant fluids, made by inductively coupled plasma spectrometry, showed that nonmetallic ions were present in the coatings.