Key Engineering Materials Vol. 670

Abstract: Methods of chromatography-mass spectrometry, IR spectroscopy, viscometry were used to study structural and mechanical properties of highly paraffinic crude oil processed in high-frequency acoustic field. It was shown that ultrasonic treatment leads to an increase in viscosity, yield stress, viscous flow activation energy and internal fracture energy of dispersion system with an increase in processing time. Proportion of n-alkanes С₁₅Н₃₂–С₁₆Н₃₄ and concentration of aromatic hydrocarbons increase in the composition of dispersed phase of processed crude oil according to chromatography-mass spectrometry.

Abstract: The article demonstrates how acid-base properties of the surface of tin (II) oxide powders influence its photocatalytic activity in reaction of photodegradation of methylene blue. The experiment shows that the photocatalytic activity of the tin (II) oxide depends on the number and the strength of surface acid centers of the Lewis.

Abstract: We investigated tribological properties and worn surfaces morphology of polymer nanocomposite (PNCs) based on ultrahigh-molecular-weight polyethylene and aluminum and silicon oxide and nitride nanoparticle (NP) fillers by several methods to establish wear mechanisms. Joint mechanical activation in a planetary mill was used for the PNC preparation. PNCs with Al₂O₃ showed the best wear resistance. Scanning electron microscopy suggests that worn surfaces of PNCs with different fillers had different wear mechanisms. IR-spectroscopy and EDS analysis showed that oxidation processes occurred during friction and wear. Oxides of aluminum and silicon might be catalysts of oxidation processes. Due to tribochemical processes, cross-linked structures were formed on the PNCs surfaces. Probably, these cross-linked structures provide increase of wear resistance.

Abstract: Phase evolution of copper-containing zirconium phosphates during the temperature treatment up to 900 °C and formation of active Cu⁰ particles on the surface of these materials in H₂/Ar flow were studied. The materials were characterized by XRD, TEM, TPR-H₂ at different steps of treatment. Temperature increase up to 900 °C led to removal of oxygen from the CuZr₄P₆O₂₄ structure with formation of Cu⁺-containing compounds. Materials treated by H₂-containing flow at 600 °C contained Cu⁰ particles with sizes from 2 nm to 1 μm. Mixed copper-zirconium phosphate was shown to adsorb CO above 80 °C, while pre-reduced materials adsorbed it starting from 30 °C with formation of CO₂ above 100 °C.

Abstract: Relevance of the work caused by necessity of expanding the database of the mutual solubility of salts of rare earth elements to create technologies for producing them in pure form for high-tech industries. The main aim of the study: was to investigate reciprocal solubility of lanthanum and erbium bromates and trichloroacetates in the water and the and to determine the conditions of solid solutions formation and the possibility of obtaining concentrates of lanthanum and erbium.

Abstract: Classification of simple supramolecular structures (for example molecular complexes), which has been introduced and described by Mulliken [1], is based on types of molecular orbitals of the components. In the paper [2], disadvantages of such classification are shown, which motivate us to return to the re-examination properties of molecular complexes. By this reason, there is a need to research the molecular complexes of one electron acceptor with a wide range of electron donor molecules. This paper have continued work (Part I [3]) on the chloranil complexes by studying the spectral properties complexes of N- and O-unsubstituting anilines and phenols. The present work aimed at analyzing linear relation the energies of charge-transfer bands of molecular complexes are related to ionization potentials of the donor components. All complexes conform to linear relations like involving both adiabatic and vertical ionization potentials of donor components. Mulliken [1] has been proposed to apply the vertical ionization potentials of donor components only. The development of photoelectron spectroscopy has led to the measurement of adiabatic and vertical ionization energies for thousands of molecules, which allow theirs to the present analysis of spectral properties molecular complexes.

Abstract: Alkaline earth metal aluminates activated by rare-earth ions (REⁿ⁺) possess intensive luminescence upon UV excitation. The paper studies phase formation of calcium aluminate prepared by the sol-gel method. The stages of the end products’ formation using methods of the thermal and the infrared spectrometric analysis and X-ray diffraction are proposed. Dependence of phase composition, the surface morphology and luminescence properties on the annealing temperature of the precursor is investigated.

Abstract: Textural characteristics and structural peculiarities of materials based on supported vanadium oxide are considered. The materials were prepared by the incipient wetness impregnation of SiO₂, TiO₂, γ-Al₂O₃ and carbon-modified γ-Al₂O₃ supports using an aqueous solution of NH₄VO₃. Samples were characterized by low temperature N₂ adsorption, XRD, IR, Raman and US-Vis DR spectroscopy and H₂-TPR.

Abstract: Glass-ceramics phosphors were obtained by the introduction of the crystalline phase NaMg₃Sc (MoO₄)₅:Eu³⁺,Tb³⁺ in the glass composition 8SiO₂-20B₂O₃-5Lu₂O₃-31Bi₂O₃-36ZnO. The properties were characterized by X-ray diffraction (XRD), photoluminescence (PL) and photoluminescent excitation spectra (PLE). The XRD patterns were indicated NaMg₃Sc (MoO₄)₅:Eu³⁺,Tb³⁺ crystallize well with the novel structure type and were assigned to the triclinic phase (space group PĪ, Z = 6). Glass-ceramic phosphors are well-known and promising as solid electrolytes, laser, luminescent and other inorganic materials. Luminescent properties of the phosphors are performed at room temperature. The excitation spectra of Eu-doped phosphor present strong absorption at 300 nm and the sharp peaks in the 350-500 nm range. Under the 394 nm excitation, intense red emission peak at 616 nm corresponding to ⁵D₀→⁷F₂ transition of Eu³⁺ is observed in the emission spectrum. The luminescence property indicates that the local symmetry of Eu³⁺ ion has no inversion center. The excitation spectra of Tb-doped phosphor by monitoring wavelength at 546 nm shows the intense broad band from 260 to 420 nm and the line at 234 nm, which is mainly attributed to charge-transfer band transition in MoO₄^2- group, indicating the existence of energy transfer from MoO₄^2- to Tb³⁺ in the Tb³⁺:glass-ceramic. The measured emission spectrum of Tb-doped phosphor has intense green emission at 546 nm corresponding to ⁵D₄→⁷F₅ transition of Tb³⁺, with λ_ex=368 nm. The as-prepared phosphors may find potential applications in the field such as color displays, light-emitting diodes (LEDs) and optoelectronic devices.

Abstract: The thermodynamically possible reactions in MnTe-H₂O system at room temperature have been studied. The potential–pH diagram has been plotted assuming quasi-equilibrium on interfacial boundary. The possible mechanism of formation and the composition of a surface in dependence on electrode potential and pH have been discussed and the stable conditions for manganese telluride, i.e. the specific area in the diagram (pH from −2 to 14 and potential from −1.5…− 1.1 to −0.9…−0.6 V) have been found. The obtained results may help optimize the conditions for electodeposition of manganese telluride thin films and for liquid chemical etching for the formation of interfacial boundaries.