In the paper, a novel technique for highly dispersed pyrochlore Y2Ti2O7 is proposed. The experimental results proved that the application of microwave irradiation at a certain stage of calcination allowed synthesizing of Y2Ti2O7 in much shorter time, which ensured substantial energy savings. An increase up to 98 wt.% in the content of the preferred phase with a pyrochlore-type structure Y2Ti2O7 was obtained after 25 h of yttrium and titanium oxides calcination at a relatively low temperature of 1150 °C, while the microwave-supported process took only 9 h and provided 99 wt.% of pyrochlore. The proposed technology is suitable for industrial applications, enabling the fabrication of large industrial amounts of pyrochlore without solvent chemistry and high-energy mills. It reduced the cost of both equipment and energy and made the process more environmentally friendly. The particle size and morphology did not change significantly; therefore, the microwave-assisted method can fully replace the traditional one.
Al2O3 and Al2O3/ZrO2 multilayer coatings were deposited by the magnetron method by sputtering the corresponding metal targets in a mixture of oxygen and argon gases. The microstructure of the cross sections to determine the thickness and elemental composition of the obtained coatings was studied by transmission and scanning electron microscopy. The surface morphology of Al2O3 coating samples was studied by scanning probe microscopy. It is shown that the formed Al2O3 coating and the Al2O3/ZrO2 multilayer coating have a columnar structure with the columns oriented perpendicular to the surface. The columnar structure of multilayer coatings is not violated during the transition from layer to layer. The coating surface consists of globules with a diameter of about 20 nm. It was found that the Al2O3 coating has dielectric properties using the method of impedance spectrometry. Thus, it was shown that the magnetron method can be used to apply high-quality multilayer dielectric coatings, which can be used as thermal barrier coatings to protect the blades of high-temperature stages of aircraft engine turbines.
Multilayer (TiSi)N/CrN coatings were fabricated through vacuum-arc deposition by applying the arc currents of (100 ÷ 110) A on TiSi cathode and (80 ÷ 90) A on Cr cathode, negative bias potential connected to the substrate holder of –(100 ÷ 200) V and reactive gas pressure of (0.03 ÷ 0.6) Pa. Applying a negative bias voltage on substrates enhanced the ion bombardment effect, which affected the chemical compositions, phase state, mechanical and tribological properties of (TiSi)N/CrN coatings. Obtained results indicated that (TiSi)N/CrN coatings with Si content ranging from 0.53 to 1.02 at. % exhibited a high hardness level of (22.1 ÷ 31.1) GPa accompanied with a high Young’s modulus of (209 ÷ 305) GPa, H/E* level of (0.080 ÷ 0.100), H3/E*2 level of (0.15 ÷ 0.33) GPa, and the friction coefficient of 0.35. Values of critical loads at dynamic indentation, changes in friction coefficient and level of acoustic emission signal evidence the high adhesive strength of (TiSi)N/CrN coatings, which allows recommending them to increase cutting tool performance.
The paper investigates the structure and properties of nanoscale multilayer coatings based on (TiZr)N and (TiSi)N produced by vacuum arc technique. Also, it provides an analysis of the impact of partial pressure of nitrogen on structural and phase state of coatings. The nitride phases are strongly textured, crystallographic planes (111) of most grains are oriented parallel to the surface. Dimensions of the coherent scattering regions and values of micro-distortions of the lattice have been calculated. The hardness of coatings reached 37.1 GPa, and the adhesion fracture load exceeds 150 N. The process technology ensures high uniformity of and a low defect rate in obtained coatings.
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