Papers by Keyword: Thin Coating

Abstract: Coatings with flake carbonyl-iron powder as absorber and polyurethane resin as matrix were prepared. The complex permittivity, complex permeability and microwave-absorbing properties were investigated in the frequency range of 2–18 GHz. Both the complex permittivity and permeability of the flaky carbonyl-iron were increased compared to the spherical powders. The minimum reflection loss decreased and the matching frequency shifted to the lower frequency region with increase in the coating thickness. The band width can reach nearly 16GHz as the RL was below than-4 dB with thickness only 1.4 mm. The minimum reflection loss value of-14.5 dB was obtained at 3.56 GHz for the 1.6mm coatings with 89 wt% carbonyl-iron powders. These results showed that the coatings were favorable for the broadband low-frequency microwave absorption with a small thickness.

Abstract: SnO₂-TiO₂ sol-gel coatings on soda-lime silicate glass heat treated at 500 °C and xerogel specimens also heat treated at 500 °C were investigated in this study. The morphology of 1, 3, 5 and 7 mol% SnO₂ doped titanium oxide coatings were evaluated with a scanning electron microscope (SEM), an atomic force microscope (AFM) and an UV-VIS light spectrophotometer, whilst xerogel structure was analysed with X-ray diffraction spectroscopy (XRD). The physicochemical properties of the TiO₂-SnO₂ systems depended mainly on the Sn-to-Ti ratio. The surface morphology of the layer was compact and homogeneous with no visible cracks. Anatase and rutile phase was found in the tested 1, 3, 5, 7 and 10 mol% SnO₂ doped and heat treated xerogel specimens. Rutile phase content in the heat treated xerogel was reduced, if Sn⁴⁺ content was increased. Photocatalytic activity and antibacterial properties were evaluated as well.

Abstract: Prepared and heat-treated sol-gel ZnO-TiO₂ coatings onto microscope glass slides were characterised by atomic force microscopy (AFM), scanning electron microscopy (SEM), as well as absorption spectra of light has been obtained. Thermally treated xerogels were characterised by X-ray diffraction (XRD). As well as their photocatalytic activity using methyl orange (MO) and observing the colour changes over the time in visible light (VIS) and ultra violet (UV) light has been determined. The influence of ZnO concentration on morphology, photocatalytic activity and antibacterial properties of coatings was analysed. The growth of S. epidermidis on the surface of the samples was inhibited due to photocatalytic properties of coatings.

Abstract: This paper addresses the problem of open thin coatings of constant thickness made from Kevlar composite material. Kevlar is an organic polymer fiber 5 times stronger than steel taken at the same weight. Therefore, this fiber has been used successfully in producing composite materials. In this paper, the generic name of Kevlar designates the composite material having the following characteristics: E=7,6×104MPa; θ=0,34; ρ=1700kgcm3. The program COSMOS/M with which the study was conducted and broadcasted was The Structural Research and Analysis Corp. The analysis was carried out by the finite element method.

Abstract: The study investigated the possibilities of determination of corrosion resistance of metal and non-metal (organic) coatings deposited to steel surface in the corrosion environment. To determine the corrosion rate of metal PVD coating based on Ti, we used the method involving measurement of polarization conductivity. Corrosion resistance of galvanic Ni or Ni-Co coatings was determined by measuring free corrosion potential E_SCE (against that of saturated calomel electrode SCE), or by means of potentiodynamic polarization relationships according to Tafel. These methods provided the basic corrosion characteristics: corrosion potential E_corr, instantaneous corrosion rate j_corr and polarization resistance R_p. Corrosion resistance of organic coating Woerodur, which was applied by pressure spray to the substrate pre-treated in various ways, was tested in a salt-fog environment. After the exposure to the respective environment we evaluated the appearance of coating. The aim of the study was to point out to the availability of methods suitable for evaluation of corrosion resistance of coatings, and to the possibilities of their application under real practical conditions.

Abstract: The article deals with the issue of evaluation of thin coatings for coating of cutting tools in order to increase their lifetime at higher temperatures. The aim of the experimental work was to determine the quality of two types of coatings - AlTiNmulti and AlTiCrN. The coatings were applied to the material Böhler 190 Microclean using PLATIT PL1001 Compact device at temperature of 430°C and pressure of 0,020 mbar. To determine the quality of coatings tribological test Pin-on-Disc was used, the counterpart was made of tungsten carbide (WC). Outputs of measurements were evaluated in Sensomp, which evaluates the results obtained from measurements using microscope PLu Noex. The results of the tests show that the AlTiNmulti coating is most suitable for use in environments with higher temperatures.

Abstract: Metallic copper ultra-thin layers were synthesized by modified PE CVD method from low-sized volatile metal complexes consisting of small (2- to 5atomic) ligand molecules. To characterize the deposited copper layers the X-ray photoelectron (XPS), infrared (FTIR) and UV-vis spectroscopy, SEM, XRD analyses were used. The layers were found to be nanocrystalline and have a nanoscale grain structure with parameters depending on the experimental conditions. It was revealed that plasma activation decreases mean size of copper grains and increases its stability on the air. The microstructure of the layers was examined by scanning electron microscopy (SEM) and diffraction of synchrotron radiation (DSR) methods, and chemical composition with a predominant content of copper in the metallic state Cu0.

Abstract: The structure of interest is a thin, metallic coating of fcc copper, of thickness down to a few nanometers only, resting on a stiffer substrate. The elastic and plastic properties of the thin coating using nanoindentation under different geometrical features such as size of the indenter and coating thickness are determined. The force-displacement curve is monitored during indentation and the precise conditions for the occurrence of so called pop-ins during loading are investigated. To simulate the nanoindentation process, a molecular dynamics approach is used, where an infinitely stiff indenter is pushed into the coating under displacement control. The coating is modeled as a thin rectangular plate, with the bottom atom layers locked from movement, simulating the stiffer substrate, and periodic boundary conditions in the plane of the plate are applied.

Abstract: A deconvolution method that combines nanoindentation and finite element analysis was developed to determine elastic modulus of thin coating layer in a coating-substrate bilayer system. In this method, the nanoindentation experiments were conducted to obtain the modulus of both the bilayer system and the substrate. The finite element analysis was then applied to deconvolve the elastic modulus of the coating. The results demonstrated that the elastic modulus obtained using the developed method was in good agreement with that reported in literature.

Abstract: Hydroxyapatite (HAP) crystalline thin-coatings have been grown using a right angle RF magnetron sputtering approach at room temperature. The surface structural information of these biocompatible coatings at nanometer scales was obtained by glancing-incidence X-ray diffraction (GIXRD) with synchrotron radiation. The GIXRD spectra were obtained by fixed incidence theta angles at 0.5 and 1 degree. Structural profile analyses were performed over these nano-coating layers with reduced substrate interference. The coating thickness was calibrated by specular X-ray reflectivity (XRR) curves. Experiments have been performed on thin-coatings of HAP sputtered on silicon wafers and acid etched titanium discs at room temperature. GIXRD analysis has shown that all the principal peaks are attributed to a crystalline HAP. Previous tests of biocompatibility with osteoblasts cells have been encouraging studies on the surface of hydroxyapatite thin coatings prepared by opposing RF magnetron sputtering approach, as a promising candidate for bioimplant materials.