COMPARISON OF TWO STAINING METHODS FOR ANODIZING IN ALLOY 6063 ALUMINUM PROFILES

Aluminum stands out for being a light, corrosion-resistant, and recyclable metal, achieving wide coverage in the market. When incorporated into alloying elements, it is possible to acquire other desirable characteristics. Alloy 6063, intended for architectural purposes, has aesthetic, structural, and strength functions. This study aims to compare two different staining methods on the surface of anodized profiles of aluminum alloy 6063. Anodized finishing is performed through an electrolytic process using sulfuric acid as an electrolyte to change the surface layer of the material, ensuring a more resistant aluminum oxide film than that formed naturally. For decorative purposes, the anodic film coloration can be performed by several methodologies, including, in this case, the coloration by organic adsorption, with the use of aniline, and the electrolytic coloration, composed of tin sulfate salts, both for obtaining the black color. To compare, neutral saline mist tests, scanning electron microscopy analysis, determination of the anodic layer thickness, and immersion tests with 3.5 percent sodium chloride for 1000 hours. The results obtained highlight that both were shown to be resistant to corrosion due to the fact that they do not present corrosion points when exposed to the neutral saline mist test for 600 hours. In the immersion tests, both remained resistant to sodium chloride. Because both methodologies present satisfactory results in all tests, the quality of the applied stains is ensured, and it is found that they are equivalent when the parameters discussed are used.

Evaluating the Antibacterial Activity and Mode of Action of Thymol-Loaded Chitosan Nanoparticles Against Plant Bacterial Pathogen Xanthomonas campestris pv. campestris

The bacterium Xanthomonas campestris pv. campestris (Xcc) causes black rot disease in cruciferous crops, resulting in severe yield loss worldwide. The excessive use of chemical pesticides in agriculture to control diseases has raised significant concern about the impact on the environment and human health. Nanoparticles have recently gained significant attention in agriculture owing to their promising application in plant disease control, increasing soil fertility and nutrient availability. In the current study, we synthesized thymol-loaded chitosan nanoparticles (TCNPs) and assessed their antibacterial activity against Xcc. The synthesis of TCNPs was confirmed by using ultraviolet–visible spectroscopy. Fourier-transform infrared spectroscopy, transmission electron microscopy, and scanning electron microscopy analysis revealed the functional groups, size, and shape of TCNPs, with sizes ranging from 54 to 250 nm, respectively. The antibacterial activity of TCNPs against Xcc was investigated in vitro by liquid broth, cell viability, and live dead staining assay, and all of them demonstrated the antibacterial activity of TCNPs. Furthermore, TCNPs were found to directly inhibit the growth of Xcc by suppressing the growth of biofilm formation and the production of exopolysaccharides and xanthomonadin. The ultrastructure studies revealed membrane damage in TCNP-treated Xcc cells, causing a release of intracellular contents. Headspace/gas chromatography (GC)–mass spectrometry (MS) analysis showed changes in the volatile profile of Xcc cells treated with TCNPs. Increased amounts of carbonyl components (mainly ketones) and production of new volatile metabolites were observed in Xcc cells incubated with TCNPs. Overall, this study reveals TCNPs as a promising antibacterial candidate against Xcc.

Electron microscopy analysis of ATP-independent nucleosome unfolding by FACT

FACT is a histone chaperone that participates in nucleosome removal and reassembly during transcription and replication. We used electron microscopy to study FACT, FACT:Nhp6 and FACT:Nhp6:nucleosome complexes, and found that all complexes adopt broad ranges of configurations, indicating high flexibility. We found unexpectedly that the DNA binding protein Nhp6 also binds to the C-terminal tails of FACT subunits, inducing more open geometries of FACT even in the absence of nucleosomes. Nhp6 therefore supports nucleosome unfolding by altering both the structure of FACT and the properties of nucleosomes. Complexes formed with FACT, Nhp6, and nucleosomes also produced a broad range of structures, revealing a large number of potential intermediates along a proposed unfolding pathway. The data suggest that Nhp6 has multiple roles before and during nucleosome unfolding by FACT, and that the process proceeds through a series of energetically similar intermediate structures, ultimately leading to an extensively unfolded form.

Oxidative removal of As(III) by polyacrylonitrile@Ag-Ag2O/schwertmannite nanofiber under visible light

Visible light response PAN@Ag-Ag2O/Sch (PAN@AS, schwertmannite and polyacrylonitrile abbreviated as Sch and PAN) nanofibers with different mass ratios were synthesized by electrospinning technology and pH-induced precipitation reaction. X-Ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy analysis showed that the formation of Ag-Ag2O/Sch heterojunction and Ag-Ag2O nanoparticles were evenly distributed on the surface of Sch. The prepared nanofibers have high oxidative removal performance for As(III) under visible light. In the [email protected] system, the total As removal percent can reach 90.96% after 120 min irradiation at pH 4.0. The scavenger experiments confirmed that the main active substances of the [email protected] system were h+ and •OH. The high oxidation and removal performance of the [email protected] composite for As(III) was attributed to the effective separation of photogenerated electron-hole pairs and high adsorption capacity of Sch for As under acidic conditions. This research provides a new material for the oxidation and removal of pollutants in water [such as As(III)] and also provides a research basis for the preparation of recyclable photocatalysts.

Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN

We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100℃ with two beam currents. Photoluminescence spectra suggested that low-beam-current ion implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the number of intrinsic dislocation loops, suggesting a decrease in the density of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

Switchable wetting of oxygen-evolving oxide catalysts

The surface wettability of catalysts is typically controlled via surface treatments that promote catalytic performance. Here we report on potential-regulated hydrophobicity/hydrophilicity at cobalt-based oxide interfaces with an alkaline solution. The switchable wetting of single particles, directly related to their activity and stability towards the oxygen evolution reaction, was revealed by electrochemical liquid-phase transmission electron microscopy. Analysis of the movement of the liquid in real time revealed distinctive wettability behaviour associated with specific potential ranges. At low potentials, an overall reduction of the hydrophobicity of the oxides was probed. Upon reversible reconstruction towards the surface oxyhydroxide phase, electrowetting was found to cause a change in the interfacial capacitance. At high potentials, the evolution of molecular oxygen, confirmed by operando electron energy-loss spectroscopy, was accompanied by a globally thinner liquid layer. This work directly links the physical wetting with the chemical oxygen evolution reaction of single particles, providing fundamental insights into solid–liquid interfacial interactions of oxygen-evolving oxides.

Influence of Surface Preparation on Cracking Phenomena in TIG-Welded High and Medium Entropy Alloys

Multi-element systems with defined entropy (HEA—high entropy alloy or MEA—medium entropy alloy) are rather new material concepts that are becoming increasingly important in materials research and development. Some HEA systems show significantly improved properties or combinations of properties, e.g., the overcoming of the trade-off between high strength and ductility. Thus, the synthesis, the resulting microstructures, and properties of HEA have been primarily investigated so far. In addition, processing is crucial to achieve a transfer of potential HEA/MEA materials to real applications, e.g., highly stressed components. Since fusion welding is the most important joining process for metals, it is of vital importance to investigate the weldability of these materials. However, this has rarely been the subject of research to date. For that reason, in this work, the weldability depending on the surface preparation of a CoCrFeMnNi HEA and a CoCrNi MEA for TIG welding is investigated. The fusion welding of longer plates is described here for the first time for the CoCrNi alloy. The welds of both materials showed distinct formation of cracks in the heat affected zone (HAZ). Optical and scanning electron microscopy analysis clearly confirmed an intergranular fracture topography. However, based on the results, the crack mechanism cannot be conclusively identified as either a liquid metal embrittlement (LME) or hot cracking-like liquid film separation.

Simple Fabrication of BiVO4 Thin Films Synthesized by Modified SILAR Method: Effect of Film Thickness

In this study, BiVO4 photoanodes were synthesized using a simple and inexpensive modified successive ionic layer adsorption and reaction (SILAR) method. In particular, the effect of the number of SILAR cycles on the photoelectrochemical (PEC) properties of BiVO4 was evaluated. Scanning electron microscopy analysis revealed the porous surface morphology of the BiVO4 thin layers with irregularly shaped particles formed on the surface of fluorine-doped tin oxide substrates. The crystal structure of BiVO4 was confirmed using X-ray diffraction analysis. The ultraviolet–visible spectrophotometry results indicated that the bandgap energy of the deposited film was approximately 2.4 eV. In addition, the PEC properties of the BiVO4 photoanodes using potentiostat were analyzed. The linear sweep voltammetry curves revealed that the photocurrent density of the BiVO4 samples increased with the increasing number of m-SILAR cycles, and a maximum photocurrent density of approximately 0.83 mA/cm2 was achieved for the BVO-35. These results suggest that an efficient photoelectrode for compact PEC cells can serve as a basis for development.

Electron microscopy analysis of femtosecond laser-assisted capsulotomy before and after lens fragmentation

Studying anterior lens capsule cutting edge profiles from femtosecond laser-assisted capsulotomy procedures performed before and after lens fragmentation. Twenty eyes (10 patients) with age-related cataract underwent femtosecond laser-assisted surgery (FLACS) using the Ziemer Z8 platform. First step of laser surgery was either capsulotomy (group first) or fragmentation (group second). One eye of each patient was assigned randomly, the second eye treated with the different sequence of procedures. After anterior capsule removal, tissue was fixed in cacodylate-buffered solution and cutting-edge profiles were analysed using scanning electron microscopy (SEM). All cases had cataract grade 2 and 3 based on LOCS III grading. SEM analysis showed more smooth edges in the first group, especially in cases with pseudoexfoliation (P = 0.037); more tags and bridges and a significant number of staggered cutting patterns (7 out of 10 cases) in the second group. All cases evolved the same microgroves with “valleys and mountains “ as signs of the photodisruption process. Femtosecond laser capsulotomy should be performed before lens fragmentation minimizing the rate of cutting errors. Especially in eyes with advanced cataract, as intracapsular pressure may increase due to lens fragmentation without anterior capsular opening.