Thermally stable composite system Al2O3-Ce 0.75Zr0.25O2 for automotive three-way catalysts

Present-day three-way catalysts operate in contact with exhaust gases whose temperature is as high as >1000 C, so the problem of developing thermally stable catalytic compositions is still topical. A series of Al2O 3-Ce0.75Zr0.25O2 composites containing 0, 10, 25, and 50 wt % Al2O3 has been synthesized by direct precipitation. The as-prepared composites and those calcined in air at 1000 and 1100 C have been characterized by BET, X-ray diffraction, transmission electron microscopy, and temperature-programmed reduction methods. The composites aged at 1050 C in a 2% O2 + 10% H2O + 88% N2 atmosphere have been used to prepare monolith catalysts, and the oxygen storage capacity (OSC) of the latter has been measured using a gas analysis setup. As the proportion of Al2O 3 in the composite is raised, the mixing uniformity and degree of dispersion of Ce x Zr1-x O2-δ particles increase, their chemical composition becomes homogeneous, and the amount of cerium involved in oxidation and reduction increases. The composite containing 50 wt % Al2O3 is a mixture of Ce x Zr 1-x O2-δ and Al2O3 crystallites, whose size is practically unaffected by calcination. The (Pt/Al2O3 + Al2O3-Ce 0.75Zr0.25O2) based on this composite has the highest OSC and is the most active. For this reason, full-scale testing of this catalyst is recommended. © 2013 Pleiades Publishing, Ltd

Self-organized growth of dendrite domains in lithium niobate and lithium tantalate single crystals

The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. The research was made possible by Russian Science Foundation (Project №14-12-00826)

Strain-polarization Coupling Mechanism of Enhanced Conductivity at the Grain Boundaries in BiFeO3thin Films

Charge transport across the interfaces in complex oxides attracts a lot of attention because it allows creating novel functionalities useful for device applications. It has been observed that movable domain walls in epitaxial BiFeO3 films possess enhanced conductivity that can be used for reading out in ferroelectric-based memories. In this work, the relation between the polarization, strain and conductivity in sol-gel BiFeO3 films with special emphasis on grain boundaries as natural interfaces in polycrystalline ferroelectrics is investigated. The interaction between polarization and grain boundaries occuring at elevated temperatures during or after material sintering stage leads to the formation of branched network of highly conductive grain boundaries with the electrical conductivity about two orders higher than in the bulk. At room temperature, these conductive traces stabilized by the defects remain and do not change upon polarization switching. These collective states provide further insight into the physics of complex oxide ferroelectrics and may strongly affect their practical applications, because reveal an additional mechanism of the leakage current in such systems. © 2020.Piezoresponse force microscopy and conductive atomic force microscopy investigations were made possible by the Russian Science Foundation (grant 19–72–10076). The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. Part of this work was developed within the scope of the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through the FCT/MEC and, when appropriate, cofinanced by FEDER under the PT2020 Partnership Agreement. For the financial support, we also express our gratitude to the Brazilian agencies: Fundação de Amparo à Pesquisa do Estado de São Paulo – FAPESP (Project N° 2017/13769–1) and Conselho Nacional de Desenvolvimento Científico e Tecnológico – CNPq (Research Grant 304604/2015–1 and Project N° 400677/2014–8) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES (CAPES-PRINT Project: 88881.310513/2018–01). This project has received funding from the Marie Sklodowska-Curie Research and Innovation Staff Exchange program (grant agreement # 778070). Part of the work (SVK) was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility and supported by DOE BES scientific user facility division

Forward growth of ferroelectric domains with charged domain walls. Local switching on non-polar cuts

Forward domain growth representing one of the main stages of domain switching is studied for isolated domains and domain arrays appearing as a result of tip-induced switching on the non-polar cuts of lithium niobate crystals. Formation of the wedge-like domains with a high aspect ratio and charged domain walls is observed. The domain growth in the area with a negligible external field is considered in terms of the kinetic approach based on analogy with crystal growth. The domain wall motion by step generation and propagation of the charged kinks is discussed. It is proposed that the switching field contains the inputs of the external field produced by a biased scanning probe microscope tip, the depolarization field produced by charged kinks, and the screening fields. According to the simulation results of the field distribution, the forward growth is caused by the step generation near the tip and the kink propagation induced by the depolarization field produced by the kinks. Scanning with the biased tip creates self-assembled domain arrays with several modes of domain length alteration: doubling, quadrupling, and chaotic. The statistical characterization of the arrays proves their high ordering. The array is formed under the influence of the depolarization field produced by three neighboring domains. The proposed mechanism can be applied for forward domain growth during switching on the polar cuts as well. In this case, the steps on the domain wall are generated on the polar surface, whereas the domain elongates by kink motion in the field produced by the charged kinks. © 2021 Author(s).The equipment of the Ural Center for Shared Use “Modern nanotechnology” Ural Federal University was used. The research was made possible by the Russian Science Foundation (Project No. 19-12-00210)

Synthesis and Study of Complex Oxide Systems Based on Ce and Sn Modified with Transition Metals for Application in Three-Way Catalysts

The work is devoted to the study of promising oxide systems with oxygen capacity. The possibility of partial replacement of platinum group metals by these oxide systems without loss of exhaust gas purification efficiency was investigated

Domain formation induced by focused ion beam in lithium niobate crystals

The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. The research was made possible in part by Government of the Russian Federation (Act 211, Agreement 02.A03.21.0006) and by President of Russian Federation grant for young scientists (Contract 14.Y30.16.8441-МК)

Electrostriction measurements in gadolinium doped cerium oxide

The equipment of the Ural Center for Shared Use “Modern nanotechnology” UrFU was used. The research was made possible with the financial support of Russian Foundation for Basic Research grant (15-52-06006-MNTI_a)

EFFECT OF THE STAGE OF BEAD MILLING OF A SUSPENSION OF OXIDE CARRIERS ON THE TEXTURAL, STRUCTURAL AND CATALYTIC PROPERTIES OF THREE-WAY CATALYSTS

The work is devoted to investigation effect of the bead milling stage of oxide supports slurry on thermal stability of three way catalysts coatings based on them. Results of the work can be used to develop TWC with high thermal stability and catalytic activity