Solid State Phenomena Vol. 341

Abstract: Series of high entropy alloys designed on Hume-Rothery criterion was prepared and the probability of the empirical approach to hydrogen storage materials preparation was investigated. Calculated HEA’s with equimolar compositions were selected from the list of alloys with limited VEC (valence electron concentration), ΔS and ΔH. The phase composition of prepared materials was compared with the prediction model and material characteristics such as chemical composition, and phase composition were studied. In this article material characterization of predicted high-entropy alloys with various prediction parameters values will be presented in terms of empirical prediction methods for solid-state hydrogen storage materials.

Abstract: The investigated slags from Bergwerk (Burgenland, Austria) are from the 17^th century and a byproduct of a copper smelting process. These slags are typical plate slags but metallographic studies have shown that these slags are atypical compared to alpine slags. There is an elongated texture running across the slag but the typical fayalite dendrites are absent. Noticeable are high sulfur and Fe levels. SEM-EDX element mappings show that FeO and FeS coexist locally, suggesting that a eutectic FeO-FeS mixture exists. The melting point could have been lowered to 930 °C by the FeO-FeS eutectic. CaSO₄ was also detected in the slag. The glass phase, containing all the slag impurities, is located between the fayalite and the FeO-FeS mixture. The smelting process, in which these slags were formed, is currently unknown. It has been unproven as well, what advantages such a copper smelting process could have.

Abstract: The metallography was used for evaluation of localised form of corrosion of stainless steel tubes of heat exchangers. The heat exchangers were in service for relative short period from few months to 2 years. The service conditions of these heat exchangers were different (temperature, medium, etc.) and caused penetration of tube walls. The metallography cross sections were used to identified the corrosion mechanisms. For all evaluated cases the different mechanisms were found – pitting corrosion, microbiologically induced corrosion, trans-crystalline corrosion cracking, intercrystallite corrosion cracking. Together with diffraction and elementary analysis of corrosion products the metallography evaluation was used for identification of corrosion mechanisms.

Abstract: During cavitation investigations with manganese-aluminum-bronzes (MAB) in seawater using ultrasound (US), it was found that the microstructure of the bronze was developed by etching. To investigate this phenomenon in more detail, metallographically polished MAB samples were US-treated in synthetic seawater. On the one hand, pulsed ultrasound was used with a sonotrode in order to be able to observe the effects of cavitation. On the other hand, an ultrasonic bath with less power than the sonotrode was used to investigate the influence of ultrasound on the electrochemical response of the MAB. It was found that the k-phase is attacked most severely by cavitation, followed by β-phase and the α-phase. Potentiostatic measurements indicated that the transport of oxygen to, and of metal ions from the metal surface is enhanced by the ultrasound, which then leads to increased corrosion rates.

Abstract: The present work deals with the causes of the damage to the distribution wheel of the main circulation pump of the nuclear power plant. During the solution of the problem, a significant influence of the final machining on the formation of cracks was found. Coarse surface machining can cause strain-induced martensite on the distribution wheel surface. Small pitting, which was observed on the surface of the distribution wheel, can be caused by the presence of martensite with less corrosion resistance. Thermal stress and residual stress after coarse final surface machining caused the growth of the cracks which initiated from the pitting.

Abstract: Barium strontium titanate (Ba_0.8Sr_0.2TiO₃) thin films have been prepared by pulsed laser deposition (PLD). The thin film of (Ba_0.8Sr_0.2TiO₃) was deposited on a silicon (Si) substrate with different deposition temperatures. The XRD pattern identifies these specimens as being of the tetragonal phase. As the deposition substrate temperature varied from 200 °C to 400 °C, the average crystal size of BST increased from 34 nm to 68 nm calculated by the XDR pattern. Field (FESEM) images have estimated the particle size of the film. The dielectric constant increased with increasing substrate temperature.

Abstract: Lead Zirconate Titanate (PZT) film was synthesized by sol-gel technique on a silicon substrate. The raw materials used to synthesize the solution of PZT consist of lead acetate, zirconate nitrate and titanate (IV) isopropoxide and 2methoxy ethanol is used as a stabilizer for Ti structure. Acetic acid is the solvent used to solve lat acetate and zirconate nitrate. The XRD pattern of the sample shows that the film has a tetragonal phase with a perovskite structure. FESEM revealed the surface morphologies and the cross-section of the film. The different thicknesses of film and annealing temperatures are investigated in this work. The dielectric constant was measured at 1 kHz, PZT films have a dielectric constant value ( 312-552 ) and a dielectric loss (0.02-0.08) at ambient temperature. Keywords: PZT film; Lead zirconated titanate; ferroelectric properties; dielectric constant.

Abstract: In this paper, studying synthesis and characterization of ferrospinel nickel ferrite. Nickel ferrite is prepared by using the sol-gel method, with a ratio of 2:1 of iron nitrate to nickel nitrate. First the starting material is dissolved in 100 ml of ethylene glycol solution to get the gel and then the gel was dried at 160°C then calcined at 600°C to obtain fine powder, second the nickel ferrite powder is pressed and sintered at 1200°C. To characterize nickel ferrite are used different techniques, such as: XRD is shown high purity, the purity of the nickel ferrite is known and the extent to which the material is affected by the temperatures of calcination and sintering. FT-IR that is shown absorption band between the elements of the components of nickel ferrite appears. The shape of the resulting powder is known through the SEM, the SEM images showed the spherical shape of the nickel ferrite powder, found the particular size of powder at 600°C ranges between405-264 nm and for sample after sintering at 1200°C ranges between589-353 nm, and our Physical characterization test down.

Abstract: Solid solutions of PZT ceramic at Zr/Ti ratio of 0.56/0.44 having various content of softener (La⁺³) and hardener (Sc⁺³) ions according to chemical formula (Pb_1-y La_y) (Sc_x Zr_0.56-x Ti_0.44) O₃, [y= (0.0 and 0.02); x= (0.02, 0.04 and 0.06)], were prepared via conventional solid state reaction methods. Structural and microstructural characteristics were investigated systematically. The measurements of XRD diffraction spectra showed occurring of phase transformation after doping with Sc⁺³ ions in both, PZT and PLZT ceramics, through emerging of tetragonal phase to coexist with the rhombohedral phase. Their fraction varied depending on content of Sc⁺³ ions. SEM mages display a different influence of softener and hardener ions, at 0.02 % mole, on the grain size. Doping with La⁺³ causes reduction in grain size, whereas Sc⁺³ increase the grain size. However, further increase in Sc⁺³ content in both (PZT and PZT) ceramics causes sharp decreasing in grain size. The latter feature is preferable in terms of increasing in the energy storage values.