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528 results on '"Zapotoczny, Szczepan"'

5. Synergistic effect of workfunction and acoustic impedance mismatch for improved thermoelectric performance in GeTe/WC composite

Author

Kumar, Ashutosh, Bhumla, Preeti, Kosonowski, Artur, Wolski, Karol, Zapotoczny, Szczepan, Bhattacharya, Saswata, and Wojciechowski, Krzysztof

Subjects
Physics - Applied Physics, Condensed Matter - Materials Science
Abstract

The preparation of composite materials is promising for concurrent optimization of electrical and thermal transport properties to realize an improved thermoelectric (TE) performance. We report the effect of work function and acoustic impedance mismatch (AIM) on the TE properties of (1-z)Ge0.87Mn0.05Sb0.08Te/(z)WC composite. In particular, a composite consisting of Mn and Sb co-doped GeTe as a matrix and WC as a dispersed phase is prepared, and its structural and TE properties are investigated. The simultaneous increase in electrical conductivity ({\sigma}) and Seebeck coefficient ({\alpha}) with WC volume fraction (z) results in an enhanced power factor ({\alpha}^2{\sigma}) in the composite. The rise in {\sigma} is attributed to increased carrier mobility in the composite. This is further established from the work function measurement using the Kelvin probe force microscopy (KPFM) technique and is also supported by the density functional theory (DFT) calculations. The difference in elastic properties (sound velocity) between Ge0.87Mn0.05Sb0.08Te and WC results in a high AIM that leads to a large interface thermal resistance (Rint) between the phases. The correlation between Rint and the Kapitza radius results in reduced phonon thermal conductivity (\kappa_ph) of the composite and is discussed using the Bruggeman asymmetrical model. The decrease in \kappa_{ph} is further established using phonon dispersion calculations that indicates the decrease in phonon group velocity in the composite. The simultaneous effect of enhanced {\alpha}^2{\sigma} and reduced \kappa_ph results in a maximum figure of merit (zT) of 1.93 at 773K for (1-z)Ge0.87Mn0.05Sb0.08Te/(z)WC composite having z=0.010. This study shows promise to achieve higher zTav across a wide range of composite materials having similar electronic structure and different elastic properties., Comment: 23 Pages, 9 Figures, 1 Table

Published
2021
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10. Nanomechanical Characterization of the Interfacial Properties of Bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine

Author

Quaroni, Luca, Bandopadhyay, Kingshuk, Mach, Marzena, Wydro, Paweł, and Zapotoczny, Szczepan

Subjects
Condensed Matter - Soft Condensed Matter
Abstract

We investigate the mechanical properties of bilayers of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine in the gel phase by using peak force tapping with quantitative nanomechanical mapping. We study both dry and aqueous bilayers and liposomes supported on the oxidized silicon surface. We report the observation of a marked substrate effect on the measured Young modulus of supported bilayer stacks which decreases as the height of the stack increases. In contrast a clear substrate effect is not observed for the top bilayer of supported aqueous liposomes, which is however affected by the surface curvature of the sample. Adhesion forces present quantitative differences between dry and aqueous samples, with the former being dominated by capillary effects and the latter by non-contact interactions between tip and substrate. The mechanical properties of stacked bilayers reveal a threshold between two different regimes, for the lower portion and the upper portion of the stack, that shows a change in the plasticity of the system. The threshold is affected by applied setpoint and aging of the sample. We propose that it arises from the presence of thin layers of hydration water between the headgroups of contacting phospholipid bilayers, which appears to have a major effect on the response of the bilayer to an external mechanical stress.

Published
2021

31. Magnetic Adsorbent Decorated with Poly(N-Isopropylacrylamide) (PNIPAM) Brushes for the Vortex-Assisted Solid Phase Extraction (VASPE) of Lead in Water, Cigarettes and Soil with High-Resolution Continuum Source Flame Atomic Absorption Spectrometry (HR-CS FAAS) Detection

Author

Khan, Mansoor, Alosmanov, Rasim, Wolski, Karol, Zapotoczny, Szczepan, and Soylak, Mustafa

Subjects
SOLID phase extraction, LEAD in water, FLAME, CIGARETTES, TOBACCO smoke, SPECTROMETRY, CESIUM ions, GAMMA ray spectrometry, CESIUM compounds
Abstract

Here is reported the synthesis of a magnetic phosphorus-containing adsorbent decorated with poly(N-isopropylacrylamide) (PNIPAM) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP) and its application for vortex assisted solid phase extraction of lead in water, cigarettes and soil. The adsorbent was characterized using Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive x-ray (EDX) spectroscopy. A high-resolution continuum source flame atomic absorption spectrometer (HR-CS FAAS) was used for the quantification of lead. All factors affecting the extraction efficiency including the solution pH, adsorbent dose, sample volume, vortex time, and elution protocols were optimized. The limits of detection (LOD) and quantification (LOQ) were determined to be 0.05 µg L−1 and 0.18 µg L−1, respectively. The preconcentration and enhancement factors were 20 and 18. Validation was performed using TMDA 64.3 fortified water and INCT-OBTL-5 tobacco leaves certified reference materials with satisfactory recoveries. The method was shown to be sensitive, efficient and reproducible. [ABSTRACT FROM AUTHOR]

Published
2024
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43. Exfoliating layered zeolite MFI into unilamellar nanosheets in solution as precursors for the synthesis of hierarchical nanocomposites and oriented films

Author

Roth, Wieslaw J., primary, Sasaki, Takayoshi, additional, Wolski, Karol, additional, Gil, Barbara, additional, Zapotoczny, Szczepan, additional, Čejka, Jiří, additional, Kubů, Martin, additional, Mazur, Michal, additional, Ebina, Yasuo, additional, Sakai, Nobuyuki, additional, Tang, Dai-Ming, additional, and Ma, Renzhi, additional

Published
2023
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