Influence of Synthesis Conditions on the Structure and the Surface State of Zirconia Nanoparticles

The paper studies the influence the nature of the salt anion and the base of precipitant, used in the synthesis of zirconia nanoparticles by chemical coprecipitation, on process parameters of the hydrogel drying, xerogel dehydration and crystallization, and the occurrence of polymorphic transitions in crystalline oxide systems are considered in this paper. The features of the structure, surface condition and properties of zirconia nanoparticles, which were obtained by using different precursors, are examined by FTIR and EPR spectroscopy, DSC and XRD methods. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3516

Formation of nanostructured state in LaBGeO₅ monolithic glass using pulsed magnetic fields

Using the methods of transmission electron microscopy, X-ray structure analysis and thermal differential analysis, it has been discovered that the pulsed magnetic field (PMF) intensifies homogeneous crystallization in LaBGeO₅-glass system, promotes homogenization of crystalline phase distribution inside the bulk of glass matrix. A possibility of obtaining the volume nanostructured state in LaBGeO₅-glass due to application of PMF has been suggested and experimentally grounded

Properties of Zirconia Nanoceramics under High-Energy Electrons Irradiation

Formation of radioactive isotopes is investigated under irradiation by relativistic electrons with energy up to 100 MeV. Radioactive isotopes 87,88Y, 88,89,95Zr, 95Nb, 175Hf are registered after irradiation by relativistic electrons with energy 47.2 MeV. The present data are necessary for the choice of a material for a dielectric wakefield accelerator. The greatest danger at operation of accelerators represents 88Y. Formation of radiation defects in nanoceramics is investigated. The various types of radiation defects are found out at an irradiation by relativistic electrons with energy 47 MeV and 86 MeV. In UV VIS spectra the absorption lines of radiation are registered at 402.2 nm and 635 nm, which correspond to the F and F' centers of monocline lattices of zirconia. It is revealed, that krypton atoms are the centers of segregation of point defects. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3562

Atmospheric Heating and Wind Acceleration: Results for Cool Evolved Stars based on Proposed Processes

A chromosphere is a universal attribute of stars of spectral type later than ~F5. Evolved (K and M) giants and supergiants (including the zeta Aurigae binaries) show extended and highly turbulent chromospheres, which develop into slow massive winds. The associated continuous mass loss has a significant impact on stellar evolution, and thence on the chemical evolution of galaxies. Yet despite the fundamental importance of those winds in astrophysics, the question of their origin(s) remains unsolved. What sources heat a chromosphere? What is the role of the chromosphere in the formation of stellar winds? This chapter provides a review of the observational requirements and theoretical approaches for modeling chromospheric heating and the acceleration of winds in single cool, evolved stars and in eclipsing binary stars, including physical models that have recently been proposed. It describes the successes that have been achieved so far by invoking acoustic and MHD waves to provide a physical description of plasma heating and wind acceleration, and discusses the challenges that still remain.Comment: 46 pages, 9 figures, 1 table; modified and unedited manuscript; accepted version to appear in: Giants of Eclipse, eds. E. Griffin and T. Ake (Berlin: Springer

Monitoring techniques for nanocrystalline stabilized zirconia from some medical prosthesis

International audienceThe paper proposes the investigation of influence of doping with Ce ions to the phase stability and mechanical properties of zirconium dioxide. For this investigation, we used X-ray and neutron diffraction, electron microscopy and microstructure characterization, including Resonant Ultrasound Spectroscopy (RUS) for nondestructive evaluation of physical-mechanical properties of ceramic made from zirconia. The RUS method has the advantage of being rapid, has a good accuracy and can be used in quality control of the object. © 2016 Taylor and Francis Group, London

Monitoring techniques for nanocrystalline stabilized zirconia from some medical prosthesis

International audienceThe paper proposes the investigation of influence of doping with Ce ions to the phase stability and mechanical properties of zirconium dioxide. For this investigation, we used X-ray and neutron diffraction, electron microscopy and microstructure characterization, including Resonant Ultrasound Spectroscopy (RUS) for nondestructive evaluation of physical-mechanical properties of ceramic made from zirconia. The RUS method has the advantage of being rapid, has a good accuracy and can be used in quality control of the object. © 2016 Taylor and Francis Group, London

X-ray photoelectron spectroscopy of nanopowders of ZrO₂-Y₂O₃-Cr₂O₃ compounds

The X-ray photoelectron spectroscopy investigation of doped zirconium dioxide nanopowders of ZrO₂ + 3 mol.% Y₂O₃ + 0.5 % Cr₂03, ZrO₂ + 0.5% Cr₂O₃ and ZrO₂ + 3 mol.% Y₂O₃ compositions has been carried out in order to obtain information about surface states of the nanoparticles. Samples of all compositions are nonstoichiometric and include four states of zirconium atoms: Zr⁴⁺(O²⁻, Zr⁴⁺(OH), Zr³⁺, and Zr²⁺. Although initial states of samples doped with yttrium and chromium and with yttrium only differ slightly from one another, after calcination at 600 °C in air for 1 h, intensity of component corresponding to Zr-OH bond in case of Y-doping decreased by 58% and in case of Y and Cr doping by 27% only. This fact shows that doping with chromium oxide slows down depiction of OH groups and explains nanopowders crystallization process delay

Synthesis of lead zirconate: influence of zirconium oxide crystal modification

Specific features of lead zirconate synthesis from zirconium oxide of various crystal modifications (monoclinic, tetragonal, and cubic) have been studied. The monoclinic zirconium oxide has been shown to exhibit thehighest reactivity and its use results in decreased temperatures of lead zirconate synthesis and the ceramic sample sintering. A physical mechanism is proposed to explain the dependence of the lead zirconate synthesis temperature on the zirconium oxide crystal lattice type.Изучены особенности процесса получения цирконата свинца из оксида циркония различной кристаллической модификации (моноклинной, тетрагональной и кубической). Показано, что моноклинная модификация оксида циркония является наиболее реакционно способной: ее использование ведет к понижению температуры синтеза цирконата свинца и температуры спекания керамических образцов. Предложен физический механизм, определяющий зависимость температуры синтеза цирконата свинца от типа кристаллической решетки оксида циркония.Досліджено особливості процесу синтезу цирконату свинцю з оксиду цирконію різної кристалічної модифікації (моноклинної, тетрагональної та кубічної). Показано, що моноклинна модифікація оксиду цирконію є найбільш реакційно здатною: її використання призводить до зниження температури синтезу цирконату свинцю та температури спікання керамічних зразків. Запропоновано фізичний механізм, що пояснює залежність температури синтезу цирконату свинцю від типу кристалічної гратки оксиду цирконію

Phase transformations in the synthesis of La₀.₇Sr₀.₃MnO₃ nanopowders

La₀.₇Sr₀.₃MnO₃ nanopowder has been obtained by co-precipitation of the metal salts out of solution using sodium carbonate. The nanopowder synthesized contains two morphologically different particle types of 40 and 100 to 200 nm size. Using X-ray diffraction and transmission electron microscopy, phase transformations of the synthesis products have been studied within temperature range of 300 to 900°C. The nanoparticle formation genesis is traced and reasons for bimodal size distribution thereof are explained.Нанопорошок La₀.₇Sr₀.₃MnO₃ получен методом совместного осаждения растворов солей металлов карбонатом натрия. Синтезированный нанопорошок состоит из двух типов частиц с размерами 40 и 100-200 нм и разной морфологической формой. Методами рентгеноструктурного анализа и просвечивающей электронной микроскопии исследовались фазовые превращения продуктов синтеза в интервале температур 300-900°С. Прослежен генезис образования наночастиц и объяснены причины их бимодального распределения по размерам.Нанопорошок La₀.₇Sr₀.₃MnO₃ одержано методом сумісного осадження розчинів солей металів карбонатом натрію. Синтезований нанопорошок складається з двох типів частинок із розмірами 40 та 100-200 нм і різною морфологією. Методами рентгеноструктурного аналізу і просвічуючої електронної мікроскопії досліджено фазові перетворення продуктів синтезу в інтервалі температур 300-900°С. Простежено генезис утворення наночастинок і пояснено причини їх бімодального розподілу за розмірами