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Correlation of Dielectric Properties and Vibrational Spectra of Composite PVDF/Salt Fibers
(MDPI, 2024-08-26) Dallaev, Rashid; Sarkar, Ranjini; Selimov, Daud; Papež, Nikola; Kočková, Pavla; Schubert, Richard; Částková, Klára; Orudzhev, Farid; Ramazanov, Shihgasan; Holcman, Vladimír
Nitride salts were added to polyvinylidene fluoride fibers and then the fiber mats were prepared by electrospinning. An experimental investigation of the structure was provided by Raman, FTIR, SEM, and XRD. The phase ratio of the polymer was studied both theoretically and experimentally in connection with the addition of the hydrates Mg(NO3)2, Ca(NO3)2, and Zn(NO3)2 salts. The com-parison of simulated and experimental data for vibrational spectroscopies is discussed. We provide a comparison of triboelectric, dielectric, and compositional characterization of PVDF fibers doped with three types of nitride hydrates. Doping of PVDF fibers with magnesium nitrate hexahydrate leads to significant improvement of the triboelectric performance.
Exploring Hydrogen Embrittlement: Mechanisms, Consequences, and Advances in Metal Science
(MDPI, 2024-06-17) Sobola, Dinara; Dallaev, Rashid
Hydrogen embrittlement (HE) remains a pressing issue in materials science and engineering, given its significant impact on the structural integrity of metals and alloys. This exhaustive review aims to thoroughly examine HE, covering a range of aspects that collectively enhance our understanding of this intricate phenomenon. It proceeds to investigate the varied effects of hydrogen on metals, illustrating its ability to profoundly alter mechanical properties, thereby increasing vulnerability to fractures and failures. A crucial section of the review delves into how different metals and their alloys exhibit unique responses to hydrogen exposure, shedding light on their distinct behaviors. This knowledge is essential for customizing materials to specific applications and ensuring structural dependability. Additionally, the paper explores a diverse array of models and classifications of HE, offering a structured framework for comprehending its complexities. These models play a crucial role in forecasting, preventing, and mitigating HE across various domains, ranging from industrial settings to critical infrastructure.
FUNCTIONAL TUNGSTEN-BASED THIN FILMS AND THEIR CHARACTERIZATION
(TANGER Ltd, 2024-01-08) Košelová, Zuzana; Horáková, Lenka; Sobola, Dinara; Burda, Daniel; Knápek, Alexandr; Fohlerová, Zdenka
Anodization is a technique that can be used to create thin layers of oxide on the surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten is still often choice for cold field emitters in commercial microscopy applications. His suitable quality can be improved even more by deposition of thin layer. Not only emission characteristic can be improved, but also emitter operating time can be prolonged. Tungsten oxide is known for its excellent resistance to corrosion and chemical attack, which is due to its stable crystal structure and the strong chemical bonds between tungsten and oxygen atoms. Many techniques were applied for this purpose, with various advantages and disadvantages. For this work anodization was chosen because of controllable uniform material coverage and easy accessibility without the need for expensive complex equipment. The anodization process involves applying an electrical potential to tungsten while it is immersed in an electrolyte solution. This causes a thin layer of tungsten oxide to form on the surface of the metal. The thickness and properties of the resulting oxide layer can be controlled by adjusting the anodization conditions, such as the electrolyte solution, voltage, and the duration of the process. In this work, H3PO4 was used as electrolyte To test whether these tungsten oxide layers would be viable for electron emitters, for use in electron guns and other devices that require high-quality electron emitters, we put them through a series of tests. Properties were evaluated using appropriate techniques. In general, anodization of tungsten to create thin tungsten oxide layers is a promising technique for producing high-quality electron emitters.
Oxidation Behavior and Outward Diffusion of Al Along Oxide Grain Boundaries of FeCrAl Alloys Overdoped with Zr and Hf
(SPRINGER, 2024-02-01) Daradkeh, Samer Issa Abdel Razzaq; Recalde, Oscar; Mousa, Marwan Suleiman; Sobola, Dinara; Boll, Torben
The formation of the alpha-Al2O3 scale on reactive element (RE)-doped FeCrAl alloys is commonly believed to be primarily caused by inward oxygen transport along grain boundaries. However, this study suggests that metal ion outward diffusion also plays a role in the development of the oxide scales and their microstructural characteristics. The study examines the oxidation behavior and grain boundary outward diffusion of iron-chromium alloys containing similar to 10 at% aluminum and similar to 22 at% chromium, doped with an over-critical concentration of REs, i.e., Zr and Hf. All samples were investigated after thermal exposure at 1100 degrees C by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). As a result of the overdoping, a considerable increase in oxide growth, an increase in the depth of internal oxidation, and RE-oxide formation near and at oxide grain boundaries (GBs) were observed as a consequence of increased inward and outward diffusion. The effect of overdoping manifests itself differently depending on the RE type and amount due to different solubility, ionic size, and electronic structure of alumina. The sample with Zr retained the adhesion of alumina to the alloy after the first and second thermal exposure, while Hf overdoping resulted in severe spallation after the second thermal exposure.
Electrical Characterization of Epoxy Nanocomposite under High DC Voltage
(MDPI, 2024-04-01) Alsoud, Ammar Awadallah Ahmad; Daradkeh, Samer Issa Abdel Razzaq; Al-Bashaish, Saleh R.; Shaheen, Adel A; Ahmad, M D (Assa’d) Jaber; Abuamr, Adel M.; Mousa, Marwan Suleiman; Holcman, Vladimír
This work studies the direct current breakdown characteristics of unfilled epoxy and epoxy nonconductive nanocomposites (SiO2,MgO and Al2O3). It also examines the variation of electrical properties in epoxy nanocomposites. The novel aspect of this study is that the samples of Epoxy nanocomposite were exposed to high voltages of up to six kilo volts for three hours using field electron microscopy under high vacuum conditions (10-5 mbar). The current emitted from these samples was measured at three different intervals of time. In addition, the influence of high voltage on the permittivity, loss factor (tan(delta)), and conductivity of the epoxy nanocomposite was studied. This evaluation was conducted before and after applying the voltage at room temperature, The frequency range extends from 10-2-10-7 Hz using the Novo Control Alpha-A analyzer. Current-voltage characterization was performed through field electron microscopy. The samples were characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy and Fourier Transform Infrared Spectroscopy. The unfilled epoxy exhibited structural degradation, resulting in the formation of holes when exposed to high voltages of up to six kilo volts, leading to a reduction in electrical properties. Nevertheless, the addition of nanoparticles shows a significant increase in the operational lifetime of the epoxy nanocomposite. The degree of increase in the lifetime of epoxy composite varied depending on several factors such as the type of NPs introduced and their respective sizes. The epoxy/Al2O3 nanocomposite comparing with epoxy/MgO and epoxy/SiO2 nanocomposite showed elevated resistance to direct current breakdown strength and maintaining its dielectric.

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