Evaluation of mechanical and physicochemical properties of protection coatings obtained by the sol-gel method
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EVALUATION OF MECHANICAL AND PHYSICOCHEMICAL PROPERTIES OF PROTECTION COATINGS OBTAINED BY THE SOL-GEL METHOD M. Tkaczyk,1 J. Krzak-Ros,1 and J. Kaleta1, 2 Thin coatings obtained by the sol-gel method could find potential applications in medical, chemical, and food industry. To achieve this, the coatings must have proper physicochemical, mechanical, and protective properties. Titanium dioxide (TiO 2 ) and silicon dioxide (SiO 2 ) coatings have been applied to the surface of stainless steel (316L) by the sol-gel method by using two techniques: dip-coating and painting. To determine the physicochemical compositions of triple SiO 2 and TiO 2 coatings, the samples were examined by the Raman spectroscopy. The surface images obtained with the help of scanning electron microscopy allow us to determine the surface morphology and continuity of the coatings. The surface morphology was examined prior to and after tensile tests. The static tensile tests and fatigue strength tests were carried out in an MTS-810 hydraulic testing machine with a measuring range of up to 100 kN. The preliminary research confirmed the fact that the coatings obtained by the sol-gel method have physicochemical, mechanical, and protective properties required for their application as protective coatings. Keywords: sol-gel thin film, titanium dioxide, silicon dioxide, protective coating, aging of hydrolysate.
Ceramic materials have better corrosion, wear, and creep resistances and lower chemical reactivity than metallic materials [1]. These properties make them valuable in applications, such as protective coatings on metallic substrates [1, 2]. Several methods are used to obtain ceramic coatings on metallic surfaces: physical vapor deposition, chemical vapor deposition, plasma spraying, laser cladding, and chemical plating or sol-gel process [3]. In the collection of all available methods, the sol-gel process seems to be the most promising. The fundamental advantage of the sol-gel process is the possibility to form ceramic materials and glasses at temperatures close to room temperature [4, 5]. Preparing glass in a traditional way requires melting of the precursors at high temperatures, which restrains the choice of substances that can be entrapped in (or onto) the glass products. It is possible to place many products inside the sol-gel materials, e.g., nanoparticles of metals, chemical substances, drugs or even some bacteria [6]. Furthermore, the sol-gel process is clean, environmentally friendly, and cost-effective [7]. The sol-gel method is based on the hydrolysis of liquid precursors and the formation of colloidal sols. This method allows us to obtain materials of high purity and excellent homogeneity of the microstructure. Depending on the choice of reagents, the method of annealing, the method of layering, and doped substances, one can obtain powders, blocks, or thin coatings (Fig. 1) with broad spectra of optical, electronic, magnetic, and electrochemical properties, as well as materials with desired porosities. The coatings obtained by the sol-gel
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