Volumen 62 (2018): Heft 1 (February 2018)

High entropy alloys (HEAs) have been in focus of scientist for past few years owing to their predicted scratch, corrosion and temperature resistance and also to interesting magnetic properties. They are usually prepared by arc melting of at least 5 pure elements. This article deals with electrodeposition of such five-element alloy from water bath, which have not been yet reported. The HEA coating consisting of Fe, Co, Ni, Mn and Mo or Zn was successfully electrodeposited on steel, copper and other metallic substrates. Substrates were polished and treated by sonication in acetone prior to electrodeposition. Obtained thin layers were documented by optical microscopy and SEM techniques. Their exact composition was determined by EDS and XRF analysis. Scratch and accelerated corrosion tests were performed to asses their resistance properties. Electrochemical properties were determined by measurements of polarization curves.

The structure and mechanical properties of the coatings formed by reactive detonation spraying of titanium in a wide range of spraying conditions were studied. The variable deposition parameters were the nature of the carrier gas, the spraying distance, the O₂/C₂H₂ ratio, and the volume of the explosive mixture. The phase composition of the coatings and the influence of the spraying parameters on the mechanical properties of the coatings were investigated. In addition, nanohardness of the individual phases contained the coatings was evaluated. It was found that the composition of the strengthening phases in the coatings depends on the O₂/C₂H₂ ratio and the nature of the carrier gas. Detonation spraying conditions ensuring the formation of composite coatings with a set of improved mechanical properties are discussed.

The contribution is focused on the preparation of coating based on the dicalcium phosphate-dihydrate (DCPD) on the surface of ZW3 magnesium alloy. For the preparation of the coating a cathodic electrodeposition technique called Large Amplitude Sinusoidal Voltammetry (LASV) was used. The DCPD layer was prepared at the temperature of 22 ± 2 °C in electrolyte composed of 0.1M Ca(NO₃).4H₂O, 0.06 M NH₄H₂PO₄ and H₂O₂. Electrochemical characteristics were evaluated by electrochemical impedance spectroscopy (EIS) in 0.1M NaCl solution. The obtained data in form of Nyquist plots were analysed by the equivalent circuit method. It is clear from the measured values of polarization resistance Rp that dicalcium phosphate-dihydrate (DCPD) layer prepared by LASV electro-deposition technique improved corrosion resistance of ZW3 alloy in the chosen environment.

Within the national and international research program of materials for advanced nuclear reactors Czech organizations contributed with several tests of metallic alloys. The specimens of the alloys were first exposed in the long term (up to 1500 hours) in simulated advanced gas cooled reactor coolant environment at 750-900 °C. After exposure the degradation of tested materials was explored, especially changes in material microstructure, corrosion damage and corrosion layer composition and in some cases also changes in mechanical properties were observed. In this paper selected results of exposure tests in high temperature helium of alloy 800 H, austenitic steel 316L and high-temperature nickel alloys are presented.

Most of the cinematographic film collections stored in film archives are made on a triacetate base, and from the 1950s to the 1980s, a magnetic track was used to record sound. With a large number of archive materials, archives often do not know the chemical composition of film bases, history of use and degradation rates. Therefore, the chemical composition of three films with a magnetic audio track and one representative of the modern film FOMAPAN were investigated by infrared spectroscopy. Selected samples were artificially aged at elevated temperatures and humidity, and the rate of degradation of the film was evaluated by infrared spectroscopy, dimensional changes and gravimetric analysis. Based on the measurements, all of the examined films were made from cellulose triacetate and the binder of the magnetic trackswas cellulose nitrate. To determine the degree of degradation of the binder of the audio track and the triacetate base, a degradation index was created which expresses the ratio of the bandwidths of the characteristic groups in the infrared spectra. It is shown that infrared spectroscopy makes it easy to determine the chemical composition of cinematographic films and to quantify the rate of degradation and the current state of the film base using a suitably chosen degradation index.