Vladyslav V. Lisnyak

THERMODYNAMIC PROPERTIES OF LIQUID Al-Si AND Al-Cu ALLOYS

The partial and integral enthalpies of mixing in liquid Al-Si and Al-Cu alloys were determined by high-temperature isoperibolic calorimetry at 1750±5 and 1590±5, respectively. The thermodynamic properties of Al-Si melts were also studied by electromotive force method in temperature range 950-1270 K. The partial and integral excess Gibbs free energies of mixing in liquid Al-Si and Al-Cu alloys were also calculated from literature data on thermodynamic activity of aluminium. The comparison of our experimental results with literature data has been performed.

Thermodynamics of liquid Fe-Si and Fe-Ge alloys

The enthalpies of mixing of liquid binary Fe-Ge (1765±5 K) and Fe-Si (1750±5 K) alloys were determined using a high-temperature isoperibolic calorimeter. The thermodynamic properties of Fe-Ge melts were also studied by electromotive force method in the temperature range of 1250-1580 K. The comparison of our measurement results with literature data has been performed. The extreme negative values of integral enthalpy of mixing and alternating-sign deviations from Raoults low for germanium can be explained by the influence of binary clusters formation.

QUANTUM CHEMICAL STUDY OF POLYAROMATIC HYDROCARBONS IN HIGH MULTIPLICITY STATES

A study of polyaromatic hydrocarbons by semiempirical PM3 and ab initio methods in MINI and STO 6G-31 bases has been performed for compounds with different numbers of rings. The optimized space and electronic structures have been derived. The multiplicity states effect on the energetic stability of the polyaromatic hydrocarbons is examined. It is shown that the high multiplicity states become more energetically preferable with the growth of the PAH size.

Thermodynamics of liquid aluminium-copper-germanium alloys

Abstract Partial for aluminium and integral enthalpies of mixing of liquid Al–Cu–Ge alloys have been measured by high-temperature isoperibolic calorimetry at T=(1380±5) K. Thermodynamic activities, partial for aluminium and integral Gibbs free energies of mixing have been determined by the electromotive force method (emf) over the range 1050⩽T/K⩽1250. Integral excess entropies of mixing have been calculated from calorimetric enthalpies and emf measured Gibbs free energies of mixing. The integral enthalpies of mixing and the integral excess Gibbs free energies of mixing have been also evaluated based on the literature data for boundaries using the Bonnier geometric model. Differences between experimental and calculated thermodynamic functions of mixing are positive. These facts as well as negative excess integral entropies of mixing reveal information about microsegregation in the melt. Therefore, the existence of ternary eutectic has been forecasted for Al–Cu–Ge phase diagram.

Quantum chemical insight on vibration spectra of silica systems

A set of silicate ions and corresponding lithium salts have been quantum chemically (QC) simulated in a “free molecule” approach. The infrared (IR), inelastic neutron scattering (INS), and Raman spectra have been simulated and fitted to the experimentally registered ones. The complete assignment of the vibrational bands along with the intensities and potential energy distribution has been performed. The applicability of the traditionally used quasimolecule Si–O–Si model to the interpretation of bands near 440–480 cm− 1 and so-called “Boson” peak near 50 cm− 1 has been critically discussed.

Crystal structure of a novel cubic pyrophosphate WP2O7

Abstract The crystal structure of a novel pyrophosphate WP 2 O 7 has been studied by X-ray powder diffraction. It was found that the crystal structure of WP 2 O 7 belongs to the well-known MoP 2 O 7 structure type ( a =7.9502 A). The tetravalent state of tungsten in the pyrophosphate has been confirmed by magnetic susceptibility measurements.

Formation of Pyrogenic Silica: Spectroscopic and Quantum Chemical Insight

This article describes the genesis of amorphous silica under high-heat conditions from SiO2 molecules through protoparticles, primary particles, and aggregates to agglomerates using vibrational spectra and quantum chemical simulations data. The impact of small molecules (water, HCl, CO2) is also discussed. The article also explains the nature of the pyrogenic silica amorphism.

Thermo-Exfoliated Graphite Containing CuO/Cu2(OH)3NO3:(Co2+/Fe3+) Composites: Preparation, Characterization and Catalytic Performance in CO Conversion

Thermo-exfoliated graphite (TEG)/CuO/Cu2(OH)3NO3:(Co2+/Fe3+) composites were prepared using a wet impregnation method and subsequent thermal treatment. The physicochemical characterization of the composites was carried out by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and Ar temperature-desorption techniques. The catalytic efficiency toward CO conversion to CO2 was examined under atmospheric pressure. Characterization of species adsorbed over the composites taken after the activity tests were performed by means of temperature programmed desorption mass-spectrometry (TPD MS). (TEG)/CuO/Cu2(OH)3NO3:(Co2+/Fe3+) composites show superior performance results if lower temperatures and extra treatment with H2SO4 or HNO3 are used at the preparation stages. The catalytic properties enhancements can be related to the Cu2(OH)3NO3 phase providing reaction centers for the CO conversion. It has been found that prevalence of low-temperature states of desorbed CO2 over high-temperature ones in the TPD MS spectra is characteristic of the most active composite catalysts.

Synthesis and transport properties of prospective photovoltaic systems related to CuInSe2 and CuGaSe2

Abstract Solid solutions in CuGaSe2–ZnSe and CuInSe2–ZnSe systems have been obtained by radio frequency heating. In order to prepare n-type phases based on CuGaSe2, p-type (CuGa)1−xZn2xSe4 and (CuIn)1−xZn2xSe4 (0.05⩽x⩽0.1) single crystals were doped by Ag, Hg, Cd, Zn implantation. The crystal structure of the solid solutions was studied by X-ray diffraction; the substitutors as well as the implantant valence states were analyzed using X-ray photoelectron spectroscopy. Hall effect, electrical conductivity, and the charge carrier mobility of an n-type zinc-implantated solid solution (CuGa)1−xZn2xSe4 and (CuIn)1−xZn2xSe4 (0.05⩽x⩽0.1) were studied.

Surface Response of Brominated Carbon Media on Laser and Thermal Excitation: Optical and Thermal Analysis Study

The present study is objected to develop an analytical remote optical diagnostics of the functionalized carbons surface. Carbon composites with up to 1 mmol g−1 of irreversibly adsorbed bromine were produced by the room temperature plasma treatment of an activated carbon fabric (ACF) derived from polyacrylonitrile textile. The brominated ACF (BrACF) was studied by elastic optical scattering indicatrix analysis at wavelength 532 nm. The obtained data were interpreted within results of the thermogravimetric analysis, X-ray photoelectron spectroscopy and temperature programmed desorption mass spectrometry. The bromination dramatically reduces the microporosity producing practically non-porous material, while the incorporated into the micropores bromine induces the dielectric and structural impact on surface polarizability and conductivity due to the charging effect. We have found that the elastic optical scattering in proper solid angles in the forward and the backward hemispheres is sensitive to the kind of the bromine bonding, e.g., physical adsorption or chemisorption, and the bromination level, respectively, that can be utilized for the express remote fabrication control of the nanoscale carbons with given interfaces.