Papers by Keyword: Degradation

Abstract: WO₃-based composite photocatalysts supported on tungsten disulfide (WS₂), urea, melamine, and graphene nanoplatelets (GNPs) were synthesized and characterized. The SEM micrographs showed that the support materials had a major impact on the composites' shape. While WO₃/WS₂ created layered sheets with scattered nanoparticles, WO₃/melamine and WO₃/urea showed porous and uneven morphologies. Strong interfacial contact was demonstrated by the homogeneous distribution of tiny WO₃ particles on crumpled graphene layers in WO₃/GNPs. W and O from WO₃, as well as S, N, and C elements from the corresponding supports, were verified by EDX. Methyl orange (MO) degradation under light irradiation was used to assess photocatalytic activity. Because of its huge surface area and improved electron mobility, WO₃/GNPs showed the highest degrading efficiency. The WO₃/WS₂ also displayed encouraging activity efficient due to the interfacial charge separation. On the other hand, WO₃/urea and WO₃/melamine performed moderately, most likely as a result of agglomeration and less conductive supports. With WO₃/GNPs emerging as a promising choice for dye degradation and wastewater treatment applications, these findings emphasize the importance of support materials in enhancing WO₃-based photocatalysts.

Abstract: Industrialization has led to widespread aquatic contamination, with dyes being among the most prominent pollutants found in various water bodies. Major contributors to dye pollution include the textile, printing, leather, cosmetics, and chemical industries, with the textile industry alone being responsible for approximately 13% of the dyes released into aquatic environments. This study focuses on comparing the photocatalytic degradation performance of synthesized catalysts prepared in the presence of biopolymers. Pullulan was selected as a capping agent to aid the synthesis process and promote the formation of nanosized catalysts. Three types of catalysts, namely copper oxide, zinc oxide, and a composite of both, were synthesized, and their performance was evaluated through the photocatalytic degradation of methylene blue. Among the three, zinc oxide demonstrated the highest degradation efficiency (99%), followed by the composite (27%), while copper oxide exhibited negligible photocatalytic activity (14%). Further optimization of the best-performing catalyst (zinc oxide) was conducted by varying parameters such as catalyst dosage (0.05-0.15g) and solution pH (5-9). The results showed that zinc oxide achieved the highest degradation under acidic conditions (pH 5) with a dosage of 0.15 g, requiring only 70 minutes to reach nearly 100% degradation. Overall, this study provides valuable insights into the influence of catalyst type on the photocatalytic degradation of methylene blue.

Abstract: Applications of advanced heat resistant ferritic steels in boiler repairs require detailed information on the creep behaviour of welds made of various combinations of steels. The paper deals with the results of hardness and microstructure characterization of a dissimilar circumferential weld of 14MoV6-3 and P91 tubes after about 10 years of service exposure in a boiler operated at 580 °C and steam pressure of 10.3 MPa. The P91 tube (f38x4 mm) was welded to the 14MoV6-3 tube (f38x6.3 mm) using the GTAW (141) technology. Bőhler-FOX IN 9-IG (3Cr0.5Mo0.3V) wires were applied as a filler material. Microhardness evaluation after long-term service exposure revealed two carburized zones, values in these zones did not exceed 350 HV0.5. The slowdown of recrystallization in partially decarburized areas of the 14MoV6-3 and the WM suppressed the formation of soft ferritic bands along fusion lines. This phenomenon is related to the high thermodynamic stability of V(C,N) particles in vanadium-bearing low alloy heat resistant ferritic steels at temperatures below 600 °C.

Abstract: This study developed WO₃/WS₂ composites loaded with noble metals to degrade methyl orange under UV light. Pure WO₃/WS₂ and variations loaded with Au, Ag, Pt, Ru, and Rh were among the photocatalysts. To examine the materials' structural, morphological, and optical characteristics, X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy were used. The highest photocatalytic activity was observed with Au@WO₃/WS₂, degrading MO by 98.59 %. The synergistic interactions between Au nanoparticles and the WO₃/WS₂ heterostructure improved charge separation and light absorption, indicating the composites' potential for effective UV-active photocatalysts for environmental remediation.

Abstract: This study investigates the synergistic potential of a novel heterojunction photocatalyst for methyl orange degradation. The photocatalyst comprises iron tungstate (FeWO₄) and graphitic carbon nitride (g-C₃N₄), engineered to exploit the distinct properties of each component for enhanced photocatalytic activity. The research systematically evaluates the performance of the synthesized FeWO₄/g-C₃N₄ composite in degrading methyl orange, with an emphasis on optimizing catalytic efficiency. The photocatalyst was characterized using advanced techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to elucidate its structural and morphological properties. Key parameters such as loading concentrations were optimized to assess their influence on the photodegradation efficiency. Among tested compositions, 1.0 wt% FeWO₄/g-C₃N₄ achieved the highest degradation efficiency of MO at 78.04% within 180 minutes under UV irradiation. The heterojunction structure promoted effective charge separation, and further enhanced visible-light response. These results demonstrate the catalyst’s potential for sustainable water purification applications.

Abstract: The operational integrity of supercritical steam power units necessitates comprehensive understanding of welded joint behaviour under high-temperature service conditions. Advanced steam cycle technology requires meticulous periodic evaluation of pressure-bearing components to ensure structural integrity throughout extended service periods. This requirement is particularly critical for components subjected to the most severe operational parameters, including superheater tubes, main steam pipelines, and steam collectors operating above critical temperature. For pressure components not directly exposed to exhaust gases, microstructural degradation represents the primary degradation mechanism governing component lifespan.P92 (X10CrWMoVNb9-2) steel, characterized by a tempered martensitic microstructure with 9% chromium content, has been extensively utilized for high-pressure applications in supercritical steam power generation systems. This advanced creep-resistant steel demonstrates superior mechanical properties, including exceptional high-temperature strength retention, oxidation resistance, and creep rupture strength under prolonged thermal exposure.Welded joints of pressure elements in steam boilers are potentially the weakest points when assessing their service life. These joints exhibit enhanced susceptibility to microstructural degradation and mechanical properties deterioration, particularly within the heat-affected zone (HAZ), during extended high-temperature operation. Therefore, systematic material characterization of welded joints relative to base material performance is essential for understanding long-term degradation mechanisms.This investigation presents systematic creep testing methodology and experimental results for P92 welded joint specimens subjected to annealing at temperatures of 600°C and 650°C for durations up to 10,000 hours. Both abridged and long-term creep tests were performed with the results of determination of creep strength and creep speed in steady state.

Abstract: Development of drug eluting biodegradable cardiovascular stent materials offers a promising alternative to conventional bare metallic stents due to their excellent biocompatibility and ability to eliminate long-term complications associated with permanent implants. The study presents a novel drug-eluting bilayer coating comprising inner calcium phosphate (CaP), titanium dioxide (TiO₂) and outer DEX-loaded chitosan for magnesium alloy stents. The coating is engineered to enhance corrosion resistance, promote biocompatibility and provide controlled drug release to mitigate restenosis and inflammation. The synergistic properties of CaP-TiO₂ improve the structural stability of the coating, while the chitosan matrix ensures effective drug delivery. In-vitro corrosion measurements and drug release kinetics demonstrate the coating’s potential for dual-functionality as a biodegradable barrier and a therapeutic agent carrier respectively. The innovative approach highlights a significant step towards the development of biodegradable drug-eluting stents tailored for cardiovascular applications.

Abstract: TiO₂-based photocatalysis has attracted a lot of interest due to its potential to capture solar energy and drive important processes including the breakdown of pollutants and the development of sustainable energy sources. A series of magnesium, zinc, and cobalt nitrate nanocomposite samples with TiO₂ semiconductor nanocomposite samples have been successfully produced by employing a simple and very effective combustion technique with the oxidizing gas urea. Prepared pure TiO₂ nanoparticle was found to have a bandgap of 3.3 eV and a crystalline size of 57.8 nm. For Co, Mg, and Zn doped TiO₂, X-ray diffraction (XRD) studies show cubic, orthorhombic, and tetragonal crystalline structures with crystalline diameters ranging between 37 nm, 46 nm, and 87 nm. Optical study has demonstrated the absorbance, transmittance, and bandgap measurements of Co, Mg, and Zn doped TiO₂. The higher provider density brought on by the Brustein-Moss impact is responsible for the bandgap values' shift to higher energies, which vary from 4.43 eV to 5.35 eV. Visiblei light irradiation was used to measure the degradation of Rhodamine-B (RhB) dye; Co, Mg, and Zn doped TiO₂ explained high photocatalytic activity, which was thoroughly described. The addition of additional energy levels to the TiO₂ bandgap by the dopants results in a wider spectrum of light absorption and more effective use of solar radiation. Here reported the parameters affect how well TiO₂ nanoparticles infused with Mg, Zn, and Co perform photocatalysis.

Abstract: In addition to the well-known bias temperature instability (BTI) phenomena, recently, it has been revealed that SiC MOSFETs show another instability during high-frequency repetitive switching between VGS(L) and VGS(H), referred to as gate-switching instability (GSI). This study shows the increase in switching energy caused by gate-switching instability VGS(th) drift as key performance parameters in electric power conversion systems, especially, when operating in hard-switching mode. A new methodology based on double pulse test was applied at each readout. The results highlighted the significance of the degradation mechanism through its impact on hard-switching applications with high-switching frequency. Therefore ruggedness against GSI plays a pivotal role in the long-term reliable operation of SiC MOSFET devices to ensure durable and efficient power conversion systems.

Abstract: The purpose of the suppressor is to partially eliminate the sound effect after firing and to mask the muzzle flame (essential for power components). When fired, the temperature rises approximately seven to ten degrees with each shot, assuming uniform temperature conditions of 21 °C. Given this knowledge, the suppressor can reach temperatures of 150 °C to 280 °C after firing one or two 30-round magazines. Assuming active training of the force or sport shooters, the suppressor will reach temperatures of 540 °C Celsius during continuous firing in an army combat situation, with temperatures in excess of 1000 °C. Already temperatures exceeding 280 °C during firing significantly affect the degradation of the suppressor material by thermal expansion through wear and tear, clogging by sediments in the case of frequent use of suppressors, massive deterioration by high temperature pressures and a significant reduction of the effect. Thermal deformation also has a significant effect, which can cause twisting or bending of the material, which can result in contact of the projectile with the suppressor and deflection of the projectile, in the worst case resulting in rupture of the suppressor and fragmentation of the projectile. Current knowledge, studies, professional articles published by the shooting public, representing the opinions and knowledge of the force components, sport shooters as well as hunters point to the lack of functionality, durability effectiveness of suppressors and point to defects, shortcomings during active use.