Pokročilé keramické materiály

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    Comprehensive analysis of charge carriers dynamics through the honeycomb structure of graphite thin films and polymer graphite with applications in cold field emission and scanning tunneling microscopy
    (ELSEVIER, 2024-09-13) Allaham, Mohammad Mahmoud; Daradkeh, Samer; Al-Braikat, Hatem; Dallaev, Rashid; Burda, Daniel; Košelová, Zuzana; Al-Akhras, M-Ali; Jaber, Ahmad; Mousa, Marwan; Sobola, Dinara; Kolařík, Vladimír; Knápek, Alexandr
    Polymer graphite electron sources have performed satisfactorily as field emission emitters and scanning tunneling microscopy probes in the past few years. However, the emission process was characterized by limited total emission currents. This paper introduces the elemental, vibrational, electronic structure, and optical analysis of polymer graphite and glass-graphite composite field emission cathodes to study these limitations. Moreover, the field emission characteristics are studied including the changes in the potential energy barrier of the used materials and structures. Among the studied structures, the cathodes prepared from graphite thin films deposited on a micropointed glass substrate (film-GMF) showed superior performance as random field emission arrays. This includes obtaining much higher emission current values 20 times) and lower threshold voltages 1/2) compared to the results obtained from polymer graphite samples. The enhancement factor in such emitters is believed to be the three-dimensional honeycomb structure of graphite. Moreover, the study includes applying graphite coatings to tungsten nano-field emission cathodes and scanning tunneling microscopy probes, which improves the performance of such cathodes/probes in both microscopic techniques.
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    Optical Properties of YttriumOrthoferrite Films Prepared by PlasmaLaser Deposition
    (Preprints.org, 2024-08-08) Sobola, Dinara; Fawaeer, Saleh Hekmat Saleh; Kočková, Pavla; Schubert, Richard; Dallaev, Rashid; Trčka, Tomáš
    This study investigates the optical properties of Yttrium Orthoferrite thin films fabricated via plasma laser deposition. Yttrium Orthoferrite, a ferrimagnetic material known for its potential applications in spintronics and photonics, was deposited on single-crystal substrates under controlled conditions to analyze its optical characteristics. The influence of deposition time, on the film quality and optical properties was examined.
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    Comprehensive Analysis of E478 Single-Component Epoxy Resin and Tungsten-E478 Interface for Metallic-Polymer Composite Electron Source Applications
    (American Chemical Society, 2024-06-29) Allaham, Mohammad Mahmoud
    This study provides comprehensive elemental, optical, and energy gap characteristics of the E478 single-component epoxy resin. This type of epoxy resin has imperative applications in medium voltage insulation and cold field emission of electrons. X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and hydrogen nuclear magnetic resonance (1H-NMR) were used to study the elemental and structural analyses, ultraviolet photoelectron spectroscopy (UPS) was used to obtain the local work function and the ionization potential energies, and ultraviolet/visible light spectroscopy (UV/VIS) was used to report the optical and energy gap characteristics of the epoxy resin being studied. Moreover, the UPS and UV/VIS analyses were merged to obtain the electron affinity of the E478 epoxy resin and to study the epoxy's energy band diagram and the tungsten-epoxy interface band structure. The results showed that the E478 epoxy resin is considered an n-type semiconductor of energy gap similar to 3.94 eV, local work function similar to 3.42 eV, ionization potential similar to 6.10 eV, electron affinity similar to 2.16 eV, and tungsten-epoxy Schottky contact barrier height similar to 2.50 eV.
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    Field Ion Microscopy of Tungsten Nano-Tips Coated with Thin Layer of the EpoxyResin
    (Preprints.org, 2024-07-30) Sobola, Dinara; AL Soud, Ammar; Knápek, Alexandr; Mousa, Marwan; Schubert, Richard; Kočková, Pavla; Škarvada, Pavel
    This paper reports results of analysis of field ion emission mechanism from tungstenepoxy composite emitters that are compared to tungsten nanofield emitters. In this context, the mechanism of emission from this type of emitters is described based on a theory of induced conductive channels. The tungsten emitters were prepared using the electrochemical polishing technique and coated with a layer of the epoxy resin. Field ion microscope (FIM) analyses are reported including the study of the emissionion density distributions from both the uncoated and coated emitters. Two forms of emission patterns have been observed in the ion emission microscopy technique describing the differences in the emission mechanism of both types of emitters. The observed results show: (a) the expected crystalline surface atomic distribution images of the field ion microscopy in the case of uncoated tungsten tips, and (b) randomly distributed emission spots that describe the locations of the induced conductive channels inside the resin coating layer.
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    Physicochemical Properties of Tungsten Trioxide Photoanodes Fabricated by Wet Coating of Soluble, Particulate, and Mixed Precursors
    (MDPI, 2024-02-01) Chittoory, Valli Kamala Laxmi Ramya; Filipská, Markéta; Bartoš, Radim; Králová, Marcela; Dzik, Petr
    Advanced oxidation processes are emerging technologies for the decomposition of organic pollutants in various types of water by harnessing solar energy. The purpose of this study is to examine the physicochemical characteristics of tungsten(VI) oxide (WO3) photoanodes, with the aim of enhancing oxidation processes in the treatment of water. The fabrication of WO3 coatings on conductive fluorine-doped tin oxide (FTO) substrates was achieved through a wet coating process that utilized three different liquid formulations: a dispersion of finely milled WO3 particles, a fully soluble WO3 precursor (acetylated peroxo tungstic acid), and a combination of both (applying a brick-and-mortar strategy). Upon subjecting the WO3 coatings to firing at a temperature of 450 degrees C, it was observed that their properties exhibited marked variations. The fabricated photoanodes are examined using a range of analytical techniques, including profilometry, thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), and voltammetry. The experimental data suggest that the layers generated through the combination of particulate ink and soluble precursor (referred to as the brick-and-mortar building approach) display advantageous physicochemical properties, rendering them suitable for use as photoanodes in photoelectrochemical cells.