Pokročilé keramické materiály
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- ItemElectrical properties of epoxy/graphite flakes microcomposite at the percolation threshold concentration(IOP Publishing Ltd, 2024-04-17) Alsoud, Ammar Awadallah Ahmad; Daradkeh, Samer; Shaheen, Adel A; Al-Hroub, Qasim Amjad; Knápek, Alexandr; Mousa, Marwan; Sobola, DinaraThe electrical properties and activation energy of epoxy/graphite flakes (GFs) micro-composite with different content of GFs (0.0625-1 wt%) were studied for electrical properties using Novocontrol Alpha Analyser (10-2 Hz-107 Hz). GFs sizes ranged from (100 nm to 10 mu m). The analysis was performed by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), visible spectrum reflectance spectra (VIS) spectra, and Fourier Transform Infrared spectra (FTIR) spectroscopy. Increasing GFs content caused multiple changes in electrical characteristics. At 0.0625 wt%, all electrical properties noticeably increased. But at 0.125 to 0.25 wt%, immobilized nanolayers were formed leading to decreased permittivity, dielectric loss (tan(delta)), quality factor (Q-factor), capacitance, conductivity, and figure of merit (F-factor). At 0.25 wt%, the epoxy microcomposite had lower permittivity, tan(delta), conductivity, and capacitance compared with unfilled epoxy. With 0.5 wt% of GFs, signified the percolation threshold, initiating a rise in permittivity, conductivity, capacitance, and tan(delta), accompanied by the closer proximity of grain boundaries, facilitating the formation of conductive channels. At a concentration of 1 wt% of GFs, the establishment of continuous interfacial conductive pathways resulted in a remarkable augmentation of all dielectric properties. The Cole-Cole analysis has been employed to investigate variations in epoxy/GFs microcomposites based on concentration levels.
- ItemEnergy gap measurements based on enhanced absorption coefficient calculation from transmittance and reflectance raw data(Elsevier, 2024-01-18) Allaham, Mohammad Mahmoud; Dallaev, Rashid; Burda, Daniel; Sobola, Dinara; Nebojsa, Alois; Knápek, Alexandr; Mousa, Marwan; Kolařík, VladimírThe absorption coefficient plays an important role in studying and characterizing semiconducting materials. It is an important parameter to study the mechanism of photons absorption within the structure of the studied material. Thus, it helps to study the several types of charge carrier transport along with the energy band structure and its defects. In literature, a formula was reported to precisely calculate the absorption coefficient from raw data of transmittance and reflectance of electromagnetic radiation. However, the reported formula has several issues limiting its validity in the literature. In this paper, we provide a more mathematically accurate form of this equation to precisely obtain the absorption coefficient from the raw data, by considering the total internal reflection at the different interfaces. Moreover, the equation is tested by simulated data and is applied to study the optical characteristics of a single-component epoxy resin from its transmittance and reflectance raw data.
- ItemCombination NIPS/TIPS Synthesis of -Fe2O3 and /-Fe2O3 Doped PVDF Composite for Efficient Piezocatalytic Degradation of Rhodamine B(MDPI, 2023-10-02) Magomedova, Asiyat; Rabadanova, Alina; Shuaibov, Abdulatip; Selimov, Daud; Sobola, Dinara; Rabadanov, Kamil; Giraev, Kamal M.; Orudzhev, FaridHighly porous membranes based on polyvinylidene fluoride (PVDF) with the addition of nanoscale particles of non-magnetic and magnetic iron oxides were synthesized using a combined method of non-solvent induced phase separation (NIPS) and thermo-induced phase separation (TIPS) based on the technique developed by Dr. Blade. The obtained membranes were characterized using SEM, EDS, XRD, IR, diffuse reflectance spectroscopy, and fluorescent microscopy. It was shown that the membranes possessed a high fraction of electroactive phase, which increased up to a maximum of 96% with the addition of 2 wt% of alpha-Fe2O3 and alpha/gamma-Fe2O3 nanoparticles. It was demonstrated that doping PVDF with nanoparticles contributed to the reduction of pore size in the membrane. All membranes exhibited piezocatalytic activity in the degradation of Rhodamine B. The degree of degradation increased from 69% when using pure PVDF membrane to 90% when using the composite membrane. The nature of the additive did not affect the piezocatalytic activity. It was determined that the main reactive species responsible for the degradation of Rhodamine B were (OH)-O-center dot and O-center dot(2)-. It was also shown that under piezocatalytic conditions, composite membranes generated a piezopotential of approximately 2.5 V.
- ItemAnalysis of processing efficiency, surface, and bulk chemistry, and nanomechanical properties of the Monel® alloy 400 after ultrashort pulsed laser ablation(IOP Publishing Ltd, 2024-01-01) Ronoh, Kipkurui; Novotný, Jan; Mrňa, Libor; Knápek, Alexandr; Sobola, DinaraMonel (R) alloy 400 has excellent corrosion resistance and finds applications in marine industries. The processing of marine components requires high processing efficiency and a quality finish. Hence, this research aims to investigate the effects of the laser processing parameters such as laser fluence, scanning velocity, hatching distance, and the scanning pass on the ablation rates and efficiency, chemistry, and nanomechanical properties of the Monel (R) alloy 400 after pulsed picosecond (ps) laser ablation. From the experimental findings, the ablation depth increases as the laser fluence increases while decreasing as the scanning velocity increases. Surface roughness was noted to increase as the laser fluence increased. The findings demonstrated that the ablation rate increases as laser fluence increases while ablation efficiency decreases. Energy dispersive x-ray spectroscopy (EDX) showed that the elemental composition of laser-ablated zones is almost similar to that of the polished sample. X-ray spectroscopy (XPS) shows that the outer layer on the surface of Monel (R) alloy 400 is composed of NiO and CuO. The hardness and Young's modulus of the laser-processed alloy were found to be less than those of the bulk material. This study can be used to establish optimal processing parameters for the ultrafast ps laser processing of materials to achieve high ablation efficiency with a high-quality surface finish for industrial applications.
- ItemOxygen Vacancies and Surface Wettability: Key Factors in Activating and Enhancing the Solar Photocatalytic Activity of ZnO Tetrapods(MDPI, 2023-11-15) Orudzhev, Farid; Muslimov, Arsen; Selimov, Daud; Gulakhmedov, Rashid; Lavrikov, Alexankder; Kanevsky, Vladimir; Gasimov, R.D.; Krasnova, Valeryia; Sobola, DinaraThis paper reports on the high photocatalytic activity of ZnO tetrapods (ZnO-Ts) using visible/solar light and hydrodynamic water flow. It was shown that surface oxygen defects are a key factor in the photocatalytic activity of the ZnO-Ts. The ability to control the surface wettability of the ZnO-Ts and the associated concentration of surface defects was demonstrated. It was demonstrated that the photocatalytic activity during the MB decomposition process under direct and simulated sunlight is essentially identical. This presents excellent prospects for utilizing the material in solar photocatalysis.