Influence of ZrO<Subscript>2</Subscript> on the physicochemical properties of the ZrO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> binary system

A series of ZrO₂-TiO₂ mixed oxides with different weight ratios (5, 20, and 30% ZrO₂) were prepared by wet impregnation of TiO₂-P25 Degussa with certain amounts of ZrO(NO₃)₂·6H₂O (Fluka) dissolved in deionised water. The samples were characterized by the XRD, , , , and BET methods. An increase in ZrO₂ content shifted the phase transition temperature (anatase into rutile) toward higher temperatures. X-ray diffraction using an Anton Paar XRK900 reactor chamber indicated that, in the case of samples containing ZrO₂, an additional diffraction peak appeared after cooling down to 25°C. This peak could be attributed to a polymorph of TiO₂ such as in the single crystal of anatase or hexagonal form of TiO₂ which appears in the presence of ZrO₂. Generally, the preparation of dioxide systems can modify the properties of pure compounds or generate new catalytic sites as a result of strong interaction between ZrO₂ and TiO₂ oxides. The binary systems exhibit advantages like strong acidity, extended specific surface area, and high thermal stability in comparison with TiO₂. The article is published in the original.     

Binary ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> xerogels: Synthesis and properties

Binary systems of silica and zirconia xerogels have been prepared by hydrolysis of zirconium(IV) oxychloride in the silica gel matrix. Systems of various composition have been studied by ¹H NMR, IR spectroscopy, and thermogravimetry and have been tested in a model process of hydrogen peroxide decomposition. It has been shown that the physicochemical properties of binary oxide systems can be tailored by varying the component ratio.     

Synthesis and characterization of ZrO<Subscript>2</Subscript> thin films

Physicochemical processes involved in the preparation of zirconia thin films by sol-gel technology from film-forming solutions (FFSs) on the basis of zirconium oxochloride and ethanol were studied. The phase composition, structure, and properties of the films were determined.     

Synthesis and characterization of ZrO<Subscript>2</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanofilms

Processes involved in the preparation of zirconia and yttria thin films by sol-gel technology from film-forming solutions (FFSs) were studied over the entire range of concentrations. The physicochemical properties, composition, and structure of the films were studied.     

Synthesis characterization and catalytic evaluation of Ni/ZrO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> aerogels catalysts

The Ni/ZrO₂/SiO₂ aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO₂–SiO₂ composite aerogels with a aqueous solution of Ni(NO₃)₂, (ii) impregnation SiO₂ aerogels with a mixed aqueous solution of Ni(NO₃)₂ and ZrO(NO₃)₂ · 2H₂O, (iii) one-pot sol–gel procedure from precursors Ni(NO₃)₂/ZrO(NO₃)₂ · 2H₂O/Si(OC₂H₅)₄. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH₃-TPD), N₂ adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride (MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component, texture, and catalytic selectivity.     

Oxygen redistribution in ZrO<Subscript>2</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> system

This work represents the results of oxygen redistribution studies at quantitative and isotopic levels in synthesis and thermal treatment of ZrO - (0 to 35 mol %) Y₂O₃ solid solution crystals. The crystals were grown by directed melt crystallization method in a cold container using direct high-frequency heating. The crystal oxygen content and isotopic composition data was collected with respect to stabilizer concentration and technological conditions of synthesis. The temperature and frequency relationships of crystal electroconductivity were also studied. Some strength and tribological characteristics of the given materials were represented. The solid state formation by directional melt crystallization was shown to involve oxygen isotopic exchange interaction between the melt, growing crystal, and gas phase.     

Physicochemical processes involved in synthesis of thin films based on double oxides of the ZrO<Subscript>2</Subscript>-GeO<Subscript>2</Subscript> system

The major physicochemical processes underlying the preparation of thin films of the ZrO-GeO₂ system from film-forming solutions based on zirconium oxochloride (ZrOCl₂ · 8H₂O), germanium tetrachloride (GeCl₄), and ethanol were studied. The phase composition, structure, and physicochemical properties of the films were determined.     

Study and Thermodynamic Analysis of the ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> System

The system ZrO₂-SiO₂ was additionally studied by means of differential thermal analysis. The temperatures of the solid-state decomposition of zircon and the coordinates of the eutectic point were refined. A thermodynamic calculation of the system in terms of the theory of subregular ionic solutions was carried out on the basis of the experimental data obtained.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 207–210.Original Russian Text Copyright © 2005 by Kamaev, Archugov, Mikhailov.     

Effect of the alkoxides addition order on the properties of Pd/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZrO<Subscript>2</Subscript> catalysts used for methane combustion

A series of Pd/Al₂O₃–ZrO₂ catalysts were prepared to be used in methane oxidation. The effect of the addition order of metal alkoxides on the texture, structure and catalytic properties of the solids is studied. The control of the preparation parameters is achieved via sol gel way as an attractive route of the preparation of these catalysts. N₂ physisorption, XRD, Scanning Electronic Microscopy (SEM) and H₂ chemisorption are the main techniques used to characterize the prepared Pd/Al₂O₃–ZrO₂ catalysts. Textural analysis reveals the mesoporosity of all the catalysts independently of the addition order of alkoxides while surface area is more pronounced when the aluminium alkoxide is added before or with the zirconium precursor. XRD patterns show the development of the zirconia tetragonal phase for all the catalysts. Better metallic dispersion is obtained when aluminium alkoxide is added first which can be justified by the high homogeneity observed on the corresponding catalyst as revealed by SEM technique.     

Sol-gel synthesis of mesoporous mixed oxides in the ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> system

Simple and convenient method was proposed for synthesis of mixed oxides in the system ZrO₂-SiO₂ (10–60 mol% zirconium dioxide). Starting substances were tetraethylorthosilicate and zirconium chloride octahydrate. The surface properties of the synthesized samples were studied and the degree of their homogeneity and the strength of acid centers were determined.     

Yttria stabilized zirconia solid electrolyte surface modification with ZrO<Subscript>2</Subscript>, Y<Subscript>2</Subscript>O<Subscript>3</Subscript>, and ZrO<Subscript>2</Subscript> + 9 mol % Y<Subscript>2</Subscript>O<Subscript>3</Subscript> films

The surface of ceramic electrolyte ZrO₂ + 9 mol % Y₂O₃, hereinafter referred to as YSZ (abbreviated yttria stabilized zirconia), was modified with 0.1 to 0.2 μm oxide films of ZrO₂, Y₂O₃, and YSZ (same composition as substrate) by dip coating in alcohol solutions of the relevant salts and further annealing. The results of scanning electronic microscopy and X-ray diffraction evidence epitaxial film growth. By means of impedance spectroscopy at the temperatures of 500 to 600°C, the effect of YZS electrolyte surface modification with ZrO₂, Y₂O₃, and YSZ films to the polarization resistance of silver electrode was studied.     

A Simple Thermal Decomposition Method for Synthesis of ZrO<Subscript>2</Subscript>/GrO Nanolayer

This paper reports on a novel processing route for producing ZrO₂/GrO nanocomposites by solid-state thermal decomposition of zirconium acetate nanostructures and graphene as starting reagents, powders were carried out in the temperature 200 °C for 2 h. In addition, nanocomposites of ZrO₂/GrO were obtained by solid-state thermal decomposition of the as-synthesized graphene oxide and Zr(CH₃COO)₂·4H₂O. The as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, atomic force microscope, photoluminescence spectroscopy and Thermogravimetric analysis. The sublimation process of the Zr(OAc)₂ and GrO powder were carried out within the range of 210, 220 and 230 °C. The XRD studies indicated the production of pure ZrO₂/GrO nanocomposites after thermal decomposition.     

Photocatalytic properties of mesoporous TiO<Subscript>2</Subscript>/ZrO<Subscript>2</Subscript> films in gas-phase oxidation of alcohols

We have used the sol-gel template synthesis method to obtain mesoporous zirconium-containing titanium dioxide films and have studied their structural and sorption characteristics, surface acid function, and photocatalytic activity during gas-phase oxidation of aliphatic alcohols. We have shown that the zirconium content changes the acidity and specific surface area of the films, determining the rate at which the studied processes occur and the relative yield of reaction products. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 354–359, November–December, 2005.     

Hydrothermal synthesis of nanosized and amorphous alumina in the ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-H<Subscript>2</Subscript>O system

The reciprocal influence of components on the chemical and structural transformations in the ZrO₂-Al₂O₃-H₂O system during nanoparticle formation under hydrothermal conditions is considered. The possibility of formation of amorphous aluminum oxide under hydrothermal conditions is found as a result of the influence of zirconia nanoparticles on the crystallization.     

Synthesis,structure, and electric properties of oxygen-deficient perovskites Ba<Subscript>3</Subscript>In<Subscript>2</Subscript>ZrO<Subscript>8</Subscript> and Ba<Subscript>4</Subscript>In<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>11</Subscript>

Perovskite phases Ba₃In₂ZrO₈ and Ba₄In₂Zr₂O₁₁ with the nominal concentration of structural oxygen vacancies 1/9 and 1/12, respectively, were synthesized by solid-phase and solution methods. X-ray diffraction showed cubic symmetry of both phases with the unit cell parameter a = 0.4193(2) and 0.4204(3) nm, respectively. The absence of superstructural lines resulted in the conclusion on statistical arrangement of oxygen vacancies. Thermogravimetry and mass spectrometry proved that both phases can reversibly absorb water from gas phase (pH₂O = 2 × 10⁻² atm) with observed correlation between the concentration of oxygen vacancies and amount of absorbed water. The total water amount was up to 0.9 mol per formula unit or, if recalculated for perovskite unit ABO₃, 0.3 and 0.23 mol H₂O, respectively. The temperature curves of coductivity in the atmosphere with various partial water vapor pressures (pH₂O = 3 × 10⁻⁵ and 2 × 10⁻² atm) showed significantly higher conductivity and lower activation energy (0.52 eV) in humid atmosphere due to proton transfer. The proton conductivity is up to 5 × 10⁻⁴ Ohm⁻¹ cm⁻¹ at 300°C for Ba₃In₂ZrO₈ specimen. IR spectrometry showed that protons in the structure exist primarily in OH-groups.     

ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> binary oxides as promising supports for palladium catalysts of hydrodechlorination

Deposited palladium catalysts of the hydrodechlorination of 1,3,5-trichlorobenzene were studied. Pure zirconium and aluminum oxides and ZrO₂-Al₂O₃ mixtures with 1, 5, and 10 mol % Al₂O₃ prepared by coprecipitation were used as supports. Palladium was deposited by the precipitation of its hydroxide on supports. Catalysts on binary supports (ZrO₂ + 1% Al₂O₃ and ZrO₂ + 5% Al₂O₃) exhibited higher activity and stability in hydrodechlorination compared with catalysts on pure supports. The suggestion was made that the high activity and stability of these systems in hydrodechlorination was related to the formation of binary oxide in the interaction of ZrO₂ with palladium oxide at the stage of annealing of the catalyst precursor. Binary oxide, which was a center of the activation of the C-Cl bond, was simultaneously a source of active hydrogen. The presence of various palladium states in catalysts was substantiated by the temperature programmed reduction method.     

Mixed amphoteric oxide ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> as catalyst for the conversion of 2-methyl-3-butyn-2-ol

The TPR spectra of the conversion of 2-methyl-3-butyn-2-ol (MBOH) on mixed ZrO₂-Al₂O₃ oxides with different ZrO₂ contents were obtained by desorption mass spectrometry. It was shown that MBOH is dehydrated to 3-methyl-3-buten-1-yne on the acid centers (H₀ ≥ –3.3) and is decomposed to acetylene and acetone at the basic centers (H_– ≤ +6.8) of this oxide. The formation of acid centers in the amorphous structure of ZrO₂-Al₂O₃ at 1.5 < Al/Zr < 3is explained by the Tanabe rule.     

Oxygen redistribution during crystal growth of ZrO<Subscript>2</Subscript>-R<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions

This paper presents the results of our experimental studies of quantitative redistribution and isotope fractionation of oxygen during the crystal growth of cubic solid solutions based on ZrO₂. The single crystals were grown by directional crystallization of a melt in a cold container. As stabilizing oxides, we used Y₂O₃, Gd₂O₃, and Yb₂O₃ in concentrations of 8–40 mol %. The results showed that the oxygen isotopic growth effects changed depending on the type and content of the stabilizer in the crystals of ZrO₂-R₂O₃ solid solutions.     

Hot atom chemical behavior of tritium in neutron-irradiated Li<Subscript>2</Subscript>TiO<Subscript>3</Subscript> and Li<Subscript>2</Subscript>ZrO<Subscript>3</Subscript>

The annihilation behavior of irradiation defects induced in neutron-irradiated Li₂TiO₃ and Li₂ZrO₃ were investigated with the tritium release behavior. It was revealed that the common characteristics in both samples were that the annihilation process of irradiation defects consisted of two first-order processes and E’-center could act as tritium trapping site, and otherwise was the way how the E’-center annihilated. The difference was suggested to attribute to the mobility of M as M⁴⁺ (or M³⁺, etc.).