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The traditional method of corrosion studies of structural materials exposed to water at high pressures and temperatures is ex-situ weight gain/loss estimation and analyses of the oxide scales. In this work, in-situ electrochemical impedance spectroscopy (EIS) is applied to study behaviour of 316 L stainless steel exposed to sub-critical and super-critical water (SCW) with the aim to investigate the effect of temperature, in particular close to the critical point of water. As the second objective, the effect of exposure time during the long-term exposure at 500 °C was investigated. Impedance data were analyzed and discussed, based on changes in the physical and chemical properties of water. Instantaneous corrosion rate data, estimated from impedance data, were converted in weight differences and compared with the literature data available for 316 L steel corrosion in SCW. The good agreement obtained supports applicability of in-situ EIS for corrosion studies in super-critical range.

Oxidační kinetiku lze v případě koroze zirkoniových slitin rozdělit do dvou stádií, která jsou od sebe oddělená transientním stavem. Výskyt transientního stavu je z korozního hlediska klíčový, neboť při něm dochází ke zvýšení rychlosti oxidace. V této práci byly pomocí in-situ elektrochemické impedanční spektroskopie studovány slitiny zirkonia Zr–Nb a Zr–Sn při teplotě 340 °C a tlaku 15 MPa v prostředí, které simulovalo chladivo reaktoru VVER. Cílem dlouhodobých experimentů (až 9000 h) bylo charakterizovat oxidační kinetiku v závislosti na expoziční době a typu zirkoniové slitiny. Výsledky ukázaly, že za uvedených experimentálních podmínek dochází u slitiny zirkonia Zr–Sn k dřívějšímu dosažení přechodu, tzv. transientnímu stavu.

Single crystals of Bi2-xInxSe3 (x = 0.0-0.66) were prepared from the elements of 5N purity using the modified Bridgman method. On the samples with a various content of incorporated In-atoms the reflectivity in IR-region and the transport coefficients (electrical conductivity σ⊥, Hall coefficient RH (B ∥ c), Seebeck coefficient S⊥) were measured. The results showed that the In-atoms incorporation to the crystal lattice of Bi2Se3 in the region of small concentrations of In-atoms increases the free carriers concentration, in the region of higher concentrations of In-atoms the free carriers concentration is suppressed. On the ground of measured changes in the values of transport coefficients and optical parameters (determined from the interpretation of infrared reflectivity) a model of point defects in the Bi2-x Inx Se3 crystal lattice has been suggested. This model takes into account the existence of antisite defects Bi'Se in the Bi2Se3 crystal lattice the concentration of which is suppressed by incorporated In-atoms. The built-in In-atoms form uncharged defects InxBi which are positively polarized.

The aim of this letter is to report the preparation of Sb2Te3-Sb2Teg_xSx and Sb2Te3-Sb2Te3_xS~ monocrystalline structures. Contrary to all expectations, p -n junctions 'were observed on these structures. Similar problems were discussed previously [1] for Bi2Te3-Bi2Se3 system. Samples with a concentration gradient of Se and S, respectively, were prepared from Sb2Te3 single crystals. Sb2Te3 single crystals were grown using the Bridgman method in conical quartz ampoules. The starting elements of semiconductor purity (99.999%) in the stoichiometric ratio were synthesized at a temperature of 1073 K for 48 h. Ampoules charged with synthesized polycrystalline material were lowered into t]~e temperature gradient of 400 K (5 cm) -I at a rate of 1.3 mmh -t. Single crystals obtained, approximately 60 mm long and 10 mm in diameter, were used to prepare the samples of dimensions 10 mm x 10 mm x 2 ram. The cleavage planes of single crystals formed the larger-area sides of the samples. The samples prepared in this way were annealed in S and Se vapour, respectively, at 623 K for 50 h. After annealing, the samples were cleaved into halves along the {0 0 0 1) planes. The resultant samples in plate-like form were of dimensions 10 m m x 10 m m x 1 mm, having higher concentration of S and Se, respectively, in one side of the sample. The concentration profiles of the samples were measured perpendicularly to the {0 0 0 1 ) planes by means of an energy-dispersive X-ray (EDX) microanalyser (KEVEX; Fig. 1). It follows from Fig. 1 that Se atoms diffuse into Sb2Te3 crystals relatively easily and form there an area of mixed crystal. This is in agreement with the phase diagram of the Sb2Teg-Sb2Se3 system [2]. The Sb atoms needed for the formation of a compound is probably taken from SbTe point defects. Therefore, the crystal volume increases. The process can be expressed by the equation

Single crystals of Bi 2 Se 3− x S x (x = 0−0.45) were prepared by the modified Bridgman method. The homogeneity of the crystals was proved by X-ray fluorescence analysis and measurement of reflectivity spectra. Measurement of the crystal lattice parameters by the powder X-ray diffraction method showed that with increasing sulfur content the value of the lattice parameter c increases and a decreases. From the measurement of reflectivity in IR region, the electrical conductivity and the Hall coefficient, some basic physical parameters of Bi 2 Se 3− x S x crystals were obtained which characterize the crystals as semiconductors.

Sb2Te3−xSex(x=0·00−1·25) single crystals were prepared from 5N purity elements using a modified Bridgman method. Measurements of the reflectivity spectra in the plasma resonance frequency range, Hall constantRH(B∥c) and electrical conductivityσ⊥C were carried out on these samples at room temperature. With increasing selenium content a shift of the reflectivity minimum towards longer wavelengths was observed as well as an increase of the Hall constant and a decrease of the electrical conductivity — the incorporation of Se atoms into the Sb2Te3 crystal lattice results obviously in a decrease in the concentration of free carriers. This effect is accounted for by a change in the polarity of bonds in the Sb2Te3 crystal lattice, due to the formation of SeTex substitutional defects.