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282 results on '"Berent, Katarzyna"'

2. Helical microstructures in molluscan biomineralization are a biological example of close packed helices that may form from a colloidal liquid crystal precursor in a twist-bend nematic phase

Author

Berent, Katarzyna, Cartwright, Julyan H. E., Checa, Antonio G., Pimentel, Carlos, Ramos-Silva, Paula, and Sainz-Díaz, C. Ignacio

Subjects
Condensed Matter - Soft Condensed Matter, Condensed Matter - Materials Science, Physics - Biological Physics
Abstract

We demonstrate that nature has produced a close-packed helical twisted filamentous material in the biomineralization of the mollusc. In liquid crystals, twist-bend nematics have been predicted and observed. We present and analyse evidence that the helical biomineral microstructure of mollusc shells may be formed from such a liquid-crystal precursor.

Published
2022
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14. Occupancies of tetra- and octahedral sites in CoFe2O4 nanoparticles: The effect of the sintering temperature.

Author

Bilovol, Vitaliy, Sikora, Marcin, Lisníková, Soňa, Żukrowski, Jan, Berent, Katarzyna, and Gajewska, Marta

Subjects
TEMPERATURE effect, RIETVELD refinement, X-ray diffraction, MOSSBAUER spectroscopy, FERRITES, X-ray absorption
Abstract

A temperature factor is one of the main parameters in the synthesis of nanoparticles and can affect considerably the arrangement of atoms in the lattice. In the system of magnetically hard CoFe2O4 spinel ferrite, the distribution of cations directly determines the magnetic properties of the sample. It was studied, on products of co-precipitation synthesis followed by a temperature dependent sinterization, by x-ray diffraction (XRD), x-ray absorption (XAS) using synchrotron radiation, vibrating sample magnetometry, and 57Fe Mössbauer spectroscopy (MS). From the Rietveld refinement of XRD patterns, the site occupancies reveal the following trend: with a decrease in the sintering temperature, the inversion degree parameter γ, which is a fraction of Co ions residing in the octahedral sites, decreases. For the highest sintering temperature explored in this work, 1000 °C, γ ≈ 0.83 giving rise to (Co0.17Fe0.83)A[Co0.83Fe1.27]BO4 formulation. For the lowest sintering temperature explored, 500 °C, the inversion degree is approximately 0.69 giving rise to (Co0.31Fe0.69)A[Co0.69Fe1.31]BO4 formulation. The propensity for the cationic arrangement was also confirmed by MS. Qualitative analysis of XAS at Co L3,2 edges strongly supports the tendency observed by XRD: the lower the sintering temperature, the more Co ions tend to occupy the tetrahedral sites. The magnetic behavior of the samples is consistent with the particle size which was determined by transmission/scanning electron microscopies. The particle size is the product of different sintering temperatures after the primary synthesis. [ABSTRACT FROM AUTHOR]

Published
2023
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16. Experimental Permeability and Porosity Determination of All-Oxide Ceramic Matrix Composite Material.

Author

Szwaba, Ryszard, Madejski, Pawel, Kaczynski, Piotr, Kurowski, Marcin, Kunz, Mathias, Berent, Katarzyna, and Ochrymiuk, Tomasz

Subjects
POROUS materials, PARTICLE size distribution, CERAMIC materials, SCANNING electron microscopy, COMPOSITE materials
Abstract

This paper presents an investigation into the water permeability of an all-oxide ceramic matrix composite. To determine the parameters and characterize the water permeability of the ceramic composite material, an experimental study was carried out in which a dedicated test rig was constructed and commissioned. A total of five different configurations of composite tubes were tested. They differed in fibre roving strength, winding angle, fibre bundle arrangement during winding, and matrix grain size distribution. To better understand the internal structure of the analysed ceramic matrix composite material, the experimental study used scanning electron microscopy for microstructure and porosity observation. The tested tubes will be used as liners in an oxy-combustion chamber in future studies. The experiments obtained new and interesting results regarding the water permeability of the ceramic matrix composite with different structural parameters. It was also observed that, as with some porous materials, the permeability of ceramic matrix composites decreases with time as more and more liquid is pressed through it. [ABSTRACT FROM AUTHOR]

Published
2024
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37. Controlling crystallites orientation and facet exposure for enhanced electrochemical properties of polycrystalline MoO3 films.

Author

Trzciński, Konrad, Zarach, Zuzanna, Szkoda, Mariusz, Nowak, Andrzej P., Berent, Katarzyna, and Sawczak, Mirosław

Subjects
SCANNING electron microscopy, IMPEDANCE spectroscopy, CYCLIC voltammetry, AQUEOUS solutions, IONS
Abstract

This study focuses on the development and optimization of MoO3 films on commercially available FTO substrates using the pulsed laser deposition (PLD) technique. By carefully selecting deposition conditions and implementing post-treatment procedures, precise control over crystallite orientation relative to the substrate is achieved. Deposition at 450 °C in O2 atmosphere results in random crystallite arrangement, while introducing argon instead of oxygen to the PLD chamber during the initial stage of sputtering exposes the (102) and (011) facets. On the other hand, room temperature deposition leads to the formation of amorphous film, but after appropriate post-annealing treatment, the (00k) facets were exposed. The deposited films are studied using SEM and XRD techniques. Moreover, electrochemical properties of FTO/MoO3 electrodes immersed in 1 M AlCl3 aqueous solution are evaluated using cyclic voltammetry and electrochemical impedance spectroscopy. The results demonstrate that different electrochemical processes are promoted based on the orientation of crystallites. When the (102) and (011) facets are exposed, the Al3+ ions intercalation induced by polarization is facilitated, while the (00k) planes exposure leads to the diminished hydrogen evolution reaction overpotential. [ABSTRACT FROM AUTHOR]

Published
2023
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