Porous ceramics based on the ZrO<Subscript>2</Subscript>(Y<Subscript>2</Subscript>O<Subscript>3</Subscript>)–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system for filtration membranes

The results of the studies of the process of fabricating ceramic filtration membranes in the system ZrO₂(Y₂O₃)–Al₂O₃ are presented. The phase compositions of the precursor powders and sintered ceramics have been investigated and their porous structures have been determined. Two stages of the implementation of the technology were demonstrated: fabrication of substrates with an open porosity ranging from 20 to 47% and pore sizes in the 100–300 nm range, as well as the deposition of nanocrystalline aluminum oxide layers on them. It has been established that the pore size distribution in the membrane layer of α-Al₂O₃ is unimodal (from 30 to 100 nm).     

Synthesis of the study of solid solutions based on the ZrO<Subscript>2</Subscript>–HfO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>(CeO<Subscript>2</Subscript>) system

The results of the studies of the conditions of the liquid-phase synthesis of highly dispersed xerogels with a low degree of agglomeration and precursor nanopowders (~10–12 nm) based on zirconium dioxide in the ZrO₂–HfO₂–Y₂O₃(CeO₂) system are presented. The thermal decomposition of xerogels and formation of crystalline solid solutions with the structure of fluorite are investigated. The optimal conditions for the solidification of nanodispersed powders for fabricating compact ceramics based on solid solutions of ZrO₂ and the physical–chemical properties of these ceramics are studied.     

Synthesis and physicochemical properties of a solid oxide nanocomposite based on a ZrO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–Gd<Subscript>2</Subscript>O<Subscript>3</Subscript>–MgO system

A highly dispersive powder with a (ZrO₂)_0.92(Y₂O₃)_0.03(Gd₂O₃)_0.03(MgO)_0.02 composition and specific surface area of 150 m²/g has been synthesized via a method of coprecipitation of hydroxides with the subsequent cryochemical treatment of the gel. Nanoceramics based on the cubic modification of zirconium dioxide with the grain size of ~40–45 nm have been obtained. The temperature dependence of the specific electrical conductance of the nanoceramics within a temperature range of 350–870°C in air has been studied, and the ratio of the ionic and electronic parts of the conductance has been determined. Recommendations for the use of the obtained oxide nanocomposite as an electrolyte for a high-temperature fuel cell have been given.     

Bimetallic Pd–Cu/ZnO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pd–Cu/ZrO<Subscript>2</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for methanol synthesis

Monometallic copper and bimetallic palladium-copper catalysts supported on ZnO–Al₂O₃ and ZrO₂–Al₂O₃ were prepared by conventional impregnation method and tested in methanol synthesis reaction under elevated pressure (3.5 MPa) in gradientless reactor at 220°C. The physicochemical properties of prepared catalytic systems were studied using BET, X-ray, TPR-H₂, TPD-NH₃ techniques. The promotion effect of palladium on catalytic activity and selectivity of copper supported catalyst in methanol synthesis reaction was proven. The highest activity of this system is explained by the Pd–Cu alloy formation.     

Hydroisomerization of Benzene-Containing Gasoline Fraction on Pt/B<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Pt/WO<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Catalysts

The effect of the hydroisomerization conditions of the benzene-containing fraction of catalytic reforming gasoline on the yield and composition of products is studied on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts. These catalysts allow benzene to be completely removed from the raw material. At the same time, the greatest yields of liquid products are obtained with minimal losses of the octane number at 2 MPa, a mass feedstock hourly space velocity (MFHSV) of 2 h^?1, and 325°C: 96.3 and 95.4 wt % on Pt/B₂O₃–Al₂O₃ and Pt/WO₃–Al₂O₃ catalysts, respectively. The activity of the catalysts is maintained for 100 h during their operation.     

Study of the physicomechanical properties of modified material of the composition Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiC–C based on acpb after reduction annealing

Dependences of the apparent density and ultimate strength in compression on amount of silicon carbide and form of modifying addition (Al, Si, B and other mixes) for materials of the composition Al2O3–SiC–C based on an aluminochromium phosphate binder after firing in a reducing atmosphere at 1400°C are studied. It is established that addition of amorphous boron and Al + Si + B are effective for improving physicomechanical properties.     

Synthesis and comparative studies of xerogels,aerogels, and powders based on the ZrO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–СeO<Subscript>2</Subscript> system

The technology of liquid-phase synthesis of mesoporous xerogels and aerogels based on ZrO₂–Y₂O₃–CeO₂ is developed. Xerogels are obtained by the coprecipitation of hydroxides, while aerogels are obtained in accordance with the sol–gel technology: the average pore size is 1.5–17.2 nm and the specific surface area is 120–878 m²/g. Aerogels are characterized by a high degree of porosity: the pore volume attains 1–4 cm³/g. Based on precursor xerogels, nanopowders of a tetragonal solid solution of the (ZrО₂)_0.92(Y₂О₃)_0.03(CeО₂)_0.05 composition with a particle size of 5–9 nm and S _spec = 74 m²/g were fabricated. Due to the high values of their specific surface area, the synthesized xerogels and aerogels are promising as sorbents, catalysts, or catalyst supports.     

Comparative Study of Powders Based on the ZrO<Subscript>2</Subscript>–Y<Subscript>2</Subscript>O<Subscript>3</Subscript>–СeO<Subscript>2</Subscript> System Obtained by Various Liquid Phase Methods of Synthesis

Using the liquid-phase methods of synthesis—the coprecipitation of hydroxides and the hydrothermal method—mesoporous xerogels are obtained based on the ZrО₂–Y₂О₃–CeО₂ system with 5–8-nm particles and powders (after the heat treatment of xerogels at 600°C) with a coherent scattering region (CSR) size of 9 to 10 nm and S_sp = 96–156 m²/g. After calcination at 1400°C, the powders are transformed into tetragonal solid solutions with a CSR size of 65 nm in the synthesis by the coprecipitation method, and they are transformed into solid solutions with a CSR size of 84 nm with a high degree of tetragonality of c/a = 1.438–1.431 in the synthesis by the hydrothermal method.     

Mechanical,Structural and Thermal Properties of Transparent Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–ZnO–TeO<Subscript>2</Subscript> Glass System

Oxide based optical glass materials has important potential material in many applications from fiber optic to sensor due to the high transparency and amourphous structures. The objective of this study is to synthesize the novel optical glass materials based on the bismuth and aluminum contents to be able to determine the physical, chemical and mechanical properties by considering the systematic experimental steps. In this study, Bi₂O₃–Al₂O₃ based tellurite optical glasses have been prepared by using conventional melt quenching method as a function of the both Bi₂O₃ and Al₂O₃ compositions. There is a strong interactions between the glass former and modifier ions that might effect on the structure and mechanical properties. During the experimental steps, thermal, structural and mechanical properties of the prepared glass materials have been determined considering the DTA/DSC, FT-IR spectroscopy, SEM and Vicker’s hardness techniques, respectively. Thermal parameters, like glass transition, T_g, onset, T_x, crystallization, T_p, and melting, T_m, temperatures were obtained by using DTA scan.     

Structural heterogeneity of SiO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>O–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> glass

It is shown that the phase heterogeneity of SiO₂–Na₂O–Al₂O₃ glass has a liquation and crystallization nature, the balance between which is determined by the conditions of their synthesis. An increase in the aluminum oxide content decreases the number of liquation and crystallization sites, and also the linear sizes of the crystalline formations without eliminating the phase separation due to the liquation. The area of metastable immiscibility in the SiO₂–Na₂O–Al₂O₃ system, which is determined by scanning electron microscopy, is probably wider than the area detected by the optical methods.     

Synthesis and study of mesoporous xerogels and nanopowders of a metastable solid solution 97ZrO<Subscript>2</Subscript>–3Y<Subscript>2</Subscript>O<Subscript>3</Subscript> for the fabrication of catalyst substrates

The—technology of the liquid-phase synthesis of metastable phases in the ZrO₂–Y₂O₃ system has been developed. Mesoporous xerogels with the specific surface area of ~350 m²/g and monophase nanopowders (5–10 nm) of the tetragonal solid solution (ZrO₂)_0.97(Y₂O₃)_0.03 have been obtained and their structural peculiarities have been revealed. The efficiency of the suggested technology and good prospects of the synthesized ZrO₂-based precursors in creating catalysts’ substrates have been demonstrated.