Solid State Phenomena Vol. 364

Abstract: Carbon nanotube (CNT) is an innovative material with significant potential for a wide range of applications, including but not limited to the development of lightweight composite materials or superconductors. A single CNT demonstrates an exceptional degree of tensile strength. CNTs are commonly employed in a structure of yarn, wherein several CNT strands are arranged and aligned together. CNT yarns, on the other hand, have a lower tensile strength than individual CNTs due to the different parameters of the yarn. This study aimed to investigate the effect of different structural parameters on the mechanical properties of CNT yarn. Sixty CNT yarn models with different structures were simulated with the molecular dynamic (MD) simulation. The varied parameters are the chirality of the CNTs, CNTs’ inner diameter, number of walls, crosslink density, and yarn twist angle. Tensile strength results from the simulations were compared concerning the varied parameters, and their influence on the nominal tensile strength of the CNT yarn was studied. It was found that the parameters for the CNT yarn that yields a higher tensile strength are the armchair type CNT with a small diameter, a large number of walls, crosslink density higher than approximately 1%, and a low twist angle.

Abstract: Lignin is a type of polymer with diverse functional groups that can be transformed into biofuels and various high-value chemicals. By utilizing light energy and operating at low temperatures, photocatalysis via Reactive Oxygen Species (ROS) becomes a promising strategy to develop further. However, the revelation of photocatalyst mechanisms in ROS production to improve the efficiency and effectiveness of lignin transformation is still limited. This study aims to determine the effect of Cu₂O/CuO quantum dots (QDs) concentration in the photocatalyst system on lignin depolymerization via ROS. The wet chemical method was used to synthesize Cu₂O/CuO QDs. The property determination of absorbance, crystallinity, and particle morphology is characterized using uv-vis, X-ray diffraction (XRD), and Transmission Electron Microscope (TEM) instrument. The ROS production was measured using a UV-vis instrument by varying the Cu₂O/CuO QDs concentration (1, 3, and 5 μM). The depolymerization sign was observed using a Fourier-Transform Infrared Spectroscopy (FTIR) instrument. The result shows that the synthesized material has a Cu₂O/CuO phase with an average particle size of 8 nm and a band gap value of 2.35 eV. The optimum ROS production activity was achieved at the Cu₂O/CuO QDs 3 μM concentration, reaching ten mM/sec. The FTIR result also confirms that the functional group transformation occurred. Overall, this study provides brief insight for further optimization of the lignin depolymerization photocatalysis process.

Abstract: This work reported the successful fabrication of a low-cost electrospun PAN nanofiber coated with Cu₂O QDs. Our works reveal that the spray coating method was effective in applying a homogenous distribution of Cu₂O QDs on the surface of PAN nanofiber. The as-synthesized Cu₂O QDs have an absorption edge at 510 nm and band gap energy of 2.5 eV indicating a light-sensitive photocatalyst. The SEM image showed an even distribution of Cu₂O QDs on the top of PAN nanofibers with an average diameter of 454.45 ± 124.732 nm. The wettability of the as-made nanofibers was determined using the contact angle method. Our PAN/Cu₂O QDs nanofibers showed hydrophilic behavior. The reactive oxygen species generation study also indicated the ability of our PAN/Cu₂O to generate singlet oxygen. Our results indicate the promising potential of PAN/Cu₂O as wound healing fabric due to the advantageous natural properties of copper and hydrophilic fabric.

Abstract: Black galingale is a medicinal plant that has medicinal properties. The major constituents found in black galingale rhizomes are flavonoids, which display antioxidant activities. Therefore, in this research, the focus is to isolate and structurally determine bioactive compounds from the ethyl acetate extract of black galingale rhizomes and evaluate their antioxidant and antimicrobial activity, The black galingale rhizomes were extracted by maceration using ethyl acetate as a solvent. the compounds were isolated by column chromatography using hexane: ethyl acetate as an eluent solvent system. The isolated compounds were examined and characterized using FT-IR, UV-Vis, and NMR techniques, examined antioxidant activity by DPPH assay, and antimicrobial activity. From the extraction of ethyl acetate extract, it was found that 4 pure flavonoid compounds could be extracted. The FT-IR spectral data of 4 compounds showed a unique vibration corresponding to OH stretching, CH stretching, C=O stretching, C=C stretching of an aromatic ring, and C-O-C bond. Antioxidant activity testing by DPPH assay found 5-hydroxy-3,7-dimethoxyflavone (1) to have the highest antioxidant activity at 73.79% compared to the standard Trolox with 133.37±1.60 mM. Antimicrobial activity testing found that 3,5,7-trimethoxyflavone (3) showed the best growth inhibition activities against B. megaterium and S. aureus, Moreover, it studies the nanoemulsion properties of 5-hydroxy-3,7-dimethoxyflavone (1) was found stable with a nanoparticle size of 21.1 nm, a zeta potential of-49.7 mV, and has PDI of 0.227. Therefore, this research shows that the extract from black galingale rhizome could be used as an active ingredient in the cosmetics industry.

Abstract: Because citric acid may be used to preserve food, the citric acid business has grown to play a significant role in the food and beverage sector. Environmental problems with gypsum waste, or citrogypsym, resulted from the manufacture of citric acid. Calcium sulfate dihydrate (DH), with low material physical characteristics, is the primary component of gypsum. As a result, the goal of this research is to examine the phase transformation process of citrogypsum using the hydrothermal process, which is a method of recrystallizing an example solution in an appropriate setting. To do this, a recycling calcium chloride solution was used, and it was heated to 95°C for five hours under atmospheric pressure to form alpha calcium sulfate hemihydrate (α-HH). The present of -OH at 1600 cm-1 wave numbers in the FT-IR spectra of α-HH, indicates that CaSO₄ has 0.5 water molecules in its crystal. Moreover, the DSC thermograms of α-HH reveal endothermic peaks at 151.2°C and 183.14°C, respectively, which correspond to the loss of 0.5 water molecules in CaSO₄. The TGA thermogram of α-HH also shows a crystal water content of 4.5 wt%. Furthermore, SEM images validate the hexagonal structure of α-HH morphology. In addition, because chloride ions have an impact on corrosive materials, the saline solution can be recycled at least four times to save money and the environment.

Abstract: The current article provides the results of the study on the improving the procedure of induction heating of products with a curvilinear surface profile by hardening of steam turbine blades surface with a complex helical shape and requiring protection against erosive wear [9, 10] using a universal microwave heating device. A principally new device that uses the effect of the magnetic field's force action has been developed and constructed. That makes possible to provide a high-quality strengthening of product surfaces regardless of their geometric configuration and size. The advantages of thermal treatment technology on such device are substantiated based on the results of metallographic, X-ray structural, and hardness analysis.

Abstract: The work investigated the nature and features of surface strengthening of steel products during friction thermomechanical processing (FTMP) of the surface. For this purpose, changes in the structure and properties occurring under the influence of FTMP in test samples were studied, and the influence of energy parameters during FTMP on the amount of surface strengthening of the samples was also evaluated. As a result of the research work, the factors affecting the preliminary thermal strengthening and additional strengthening of 65G steel samples using FTMP were identified, which allowed to increase the microhardness of the steel in the processing zone by more than 2 times. At the same time, the microhardness was increased thermally to the level of about 580 kgf/mm², which is equivalent to 5800 MPa, and after FTMP, the microhardness increased to 1300 kgf/mm², which corresponds to 13000 MPa. It is also shown that the strengthened "white" layer formed during FTMP and located along their entire processing length is continuous, which characterizes the homogeneity and uniformity of the strengthening of the surface of the samples. The load distribution at FTMP was determined using a dynamometer and the circumferential force of friction processing was calculated, which made it possible to establish dependencies that show the strengthening characteristics taking into account the thickness of the friction disc. Taking these data into account, recommendations are offered regarding the optimal thickness of the reinforcing disc.

Abstract: The article shows the process of preparing an oxide layer on the surface of titanium for use in industrial catalysis. Data from physical and chemical studies are presented, namely microhardness, porosity, thickness, specific surface area, adhesion and thermal stability of the active layer.To determine the physicochemical characteristics of the resulting oxide layer, the following analysis methods were used: X-ray diffraction analysis (XRD), X-ray diffraction phase analysis (XPA), X-ray absorption analysis (XRA), and X-ray fluorescence analysis. The thickness of the oxide layer depending on the duration of anodization was estimated by optical microscopy.

Abstract: The paper presents experimental investigations of the adhesive properties of meta-aramid coatings applied to metal substrates of different types. The increased adhesion ability of meta-aramid coatings to copper substrates was found in comparison with other metals and alloys used as structural materials. The dependence of the strength of the adhesive bond of the meta-aramid coating on the surface roughness at various concentrations of the polymer solution has been determined.