Journal of Science and Technique: Section on Physics and Chemical Engineering
Journal of Le Quy Don Technical University
GREEN SYNTHESIS OF NANO-ZERO-VALENT IRON USING CLEISTOCALYX OPERCULATUS EXTRACT FOR EFFICIENT RHODAMINE B DEGRADATION
In this study, nano-zero-valent iron (nZVI) was successfully synthesized via a green method using Cleistocalyx operculatus leaf extract as a natural reducing agent. The synthesized nZVI was characterized by XRD, SEM-EDS, FT-IR, and BET analyses. The XRD pattern confirmed the formation of crystalline α-Fe⁰while SEM images revealed spherical aggregates in the 50-100 nm size range. FT-IR analysis identified organic functional groups from the plant extract on the nanoparticle surface, indicating bio-capping. BET analysis showed a specific surface area of 67.484 m2/g with a mixed micro-mesoporous structure. Batch degradation experiments were conducted at an initial Rhodamine B (RhB) concentration of 10 mg/L, using an nZVI dose of 0.3 g/L, H2O2 dose of 0.01 M, and initial pH of 7.0. Results demonstrated that nZVI alone mainly adsorbed RhB, whereas H2O2 alone exhibited limited oxidation. In contrast, the combined nZVI/H2O2 system achieved nearly complete decolorization within 50 min, following a pseudo-first-order kinetic model with an apparent rate constant of 0.083 min-1. The enhanced efficiency was attributed to a heterogeneous Fenton-like process generating highly reactive ·OH radicals. These findings highlight that C. operculatus-mediated nZVI provides a sustainable and efficient strategy for the removal of organic dyes from wastewater, underscoring its promise for advanced water treatment applications.
INVESTIGATION OF ELECTROCHEMICAL CHARACTERISTICS of α-NaxMnO2 CATHODES FOR SODIUM-ION BATTERIES
P2 and O3 layered structure materials have large potential for application as cathodes for sodium-ion batteries. This article presents the research results on the electrochemical properties of layered structure α-NaxMnO2 (x = 0.7-1.0) cathode materials synthesized via the sol-gel method. The α-NaxMnO2 cathode materials were characterized by X-ray diffraction (XRD) to determine their crystal structure, scanning electron microscopy (SEM) to analyze their morphology, and energy-dispersive X-ray spectroscopy (EDX) to assess their elemental composition. The electrochemical properties of α-NaxMnO2 materials were investigated using CR2032 coin cells, in which the cathodes were fabricated from the synthesized α-NaxMnO2 materials. The α-NaxMnO2 cathode material exhibited the highest initial charge-discharge capacity at a rate of 0.1 C when x = 1.0, with values of 168.43 mAh.g-1 and 165.18 mAh.g-1 in the first cycle, respectively. However, the capacity declined significantly after 10 cycles and reached only about 50.02% of its initial value after 50 cycles. The composition with the highest cycling stability was Na0.8MnO2 (x = 0.8), maintaining 63.37% of its initial capacity after 50 cycles. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements were conducted using an Ivium potentiostat to evaluate the electrochemical properties of the synthesized materials. The α-NaxMnO2 material demonstrates strong potential as a cathode candidate for sodium-ion batteries.
COMPARATIVE ANALYSIS OF TiO2 NANOTUBE LAYERS FORMED BY SINGLE- AND TWO-STEP ANODIZATION: SURFACE MORPHOLOGY, CORROSION RESISTANCE, AND CELLULAR RESPONSE
This study examines the influence of anodization procedures on the formation and properties of TiO₂ nanotube layers on commercially pure titanium (cp-Ti) for biomedical implant applications. Both single-step (TiO2 1S) and two-step (TiO2 2S) anodization produced nanotubular structures composed of anatase and rutile phases, with the two-step process yielding more uniform and vertically aligned nanotubes. Mechanical testing indicated an increase in surface hardness, while electrochemical analyses demonstrated enhanced corrosion resistance, particularly for the TiO2 2S sample. Furthermore, TiO2 2S surfaces promoted superior cell adhesion and spreading, with well-developed filopodia and lamellipodia. Overall, the two-step anodization produces a more stable, oxygen-rich oxide layer with improved durability and biocompatibility, highlighting its potential for bone implant applications.
EFFECT OF SILICON ADDITION ON DEZINCIFICATION OF L72 BRASS IN CHLORIDE MEDIA
Brass alloys (Cu-Zn) are susceptible to dezincification, especially in chloride-rich environments. This study investigates the effect of adding 0.5% silicon to L72 brass on its corrosion behavior and resistance to localized corrosion induced by microcracks. Samples with and without silicon were immersed in a 3.5% NaCl solution and analyzed using electrochemical testing, EDX techniques, and dezincification coefficient (z) measurements. The results show that silicon addition improves corrosion resistance by increasing the corrosion potential, reducing current density, and minimizing zinc loss. OM and EDX analyses confirmed that the silicon-containing alloy exhibited a smoother surface and higher copper content. However, microstructural observations revealed that silicon can alter grain boundaries and promote microcrack formation, which may initiate localized corrosion. These findings suggest that while silicon enhances overall dezincification resistance, it may also introduce structural vulnerabilities, highlighting the need to optimize silicon-alloyed brass compositions to improve corrosion resistance while minimizing microcrack-induced degradation in aggressive environments.
EFFECT OF COMPRESSION FORCE IN THE FABRICATION OF MEMBRANE ELECTRODE ASSEMBLY BY DECAL METHOD FOR PROTON EXCHANGE MEMBRANE WATER ELECTROLYZER
Proton exchange membrane water electrolysis (PEMWE) is a promising technique for producing high-purity hydrogen without using fossil fuels. The outstanding advantage of PEMWE is that it is combined with renewable energy sources such as solar, wind, etc. to produce green hydrogen. The most important part in a proton exchange membrane water electrolyzer is the membrane electrode assembly (MEA). The performance of PEMWE is mainly determined by the properties of the MEA. In this paper, the authors studied the preparation of the anode catalyst layer by ink spray technique on a teflon substrate in the fabrication of MEA by decal method. This is the most advanced method that allows the fabrication of MEAs that are both of good quality and easy to perform. The pressing conditions were studied, tested and evaluated, thereby providing the optimal pressing parameters for the fabrication of MEA and then applying MEA to the proton exchange membrane water electrolyzer, running tests at different current densities and achieving the minimum potential value of 1.708 V at a current density of 1 A/cm2.
HIGHLY SELECTIVE NO2 GAS SENSOR OPERATING AT ROOM TEMPERATURE WITH PPB-LEVEL DETECTION SENSITIVITY BASED ON ZnO NANOPARTICLES
In this work, authors reported a high-selectivity nitrogen dioxide (NO2) gas sensor that operates directly at room temperature without catalyst or illumination. The NO2 gas sensor was based on ZnO nanoparticles, which were synthesized using a simple solution method, ensuring scalability in mass production. Crucially, the sensor exhibited high sensitivity and selectivity towards NO2, achieving parts-per-billion (ppb) level detection limits. At 23°C, the sensor showed a sensitivity of 4.2% with the response time and recovery time are 120 s and 185 s, respectively, under 5 ppb NO2, while the interaction with other gases such as H2S, NH3, SO2, CH4, C3H8, and CO2 was negligible. This room-temperature, easily fabricated sensor offered a promising solution for cost-effective, real-time NO2 monitoring in various applications, particularly those requiring high sensitivity at low NO2 concentrations.
DESIGN AND FABRICATION OF THE THERMAL IMAGING SYSTEM FOR TANK SIGHTS
This study reports the first successful design and fabrication of a thermal imaging sight for tank artillery in Vietnam, utilizing an uncooled detector operating in the long-wave infrared (LWIR) spectrum. The objective lens, consisting of only three spherical elements with a focal length of 100 mm, was evaluated using the modulation transfer function (MTF). The system achieved MTF values approximately 0.5 at a spatial frequency of 30 cycles per millimeter (cycles/mm), approaching the diffraction limit. Measurements of the minimum resolvable temperature difference (MRTD) demonstrate that the sighting system is capable of detecting tank-sized targets at ranges exceeding 2 kilometers.
EVALUATION OF SPECIFIC PROPERTIES OF FINISHED WOOL AND WOOL-BLENDED POLYESTER WOVEN FABRICS
This article presents experimental evaluations of 5 samples of finished woven wool and wool-blend polyester fabrics with different proportions of raw materials provided by Nam Dinh Silk Textile Joint Stock Company for research. Experimental evaluations are sequently performed with fabric capillarity determined according to TCVN 5073-90 standard, the wrinkle resistance degree of fabric determined according to TCVN 7425:2004 standard, the breathability of fabric determined according to TCVN 5092:2009 standard, the shrinkage of fabric after washing determined according to TCVN 8041:2009 ISO 5077:2007 standards. The research results prove that the material composition of the fabric affects some fabric properties, specifically concerning fabric sample PLE1 (LE (P/W/C 29.5/70/0.5) has the ability to the highest capillarity in the longitudinal and transverse directions of 0.83 cm/min and 0.93 cm/min, respectively; PLE2 fabric sample has the largest crease return angle in the longitudinal direction reaching 174.5° with anti-creasing coefficient is 96.4%; fabric sample PLE3 has the best air permeability at 53.3 cm3/s/cm2. fabric sample LE has the highest shrinkage in the longitudinal direction at 1.8%; fabric sample PLE3 has the highest shrinkage; the horizontal direction reaches 4.0%. The research results can provide suggestions for textile product designers to choose appropriate materials when designing to meet usage requirements, contributing to improving product quality textile products.
DESIGNING INGREDIENTS OF BTX FLASH-REDUCED PROPELLANT WITH A HIGH PVC CONTENT
Based on experiments, it was researched to determine the kind of pyroxylin and the effect of flash-reduced additives (PVC) on the quality of BTX propellant. Therefore, it designed ingredients for the research and manufacture of propellant of BTX with high PVC content. The results show that the kind of pyroxylin used type BA with a high nitrogen content (about 13.26% N). The flash-reduced additive is the PVC with chlorine content at 61-65% and the thermochemical coefficient of PVC is about -(2 ± 0.5) kcal/(kg x %). When using PVC with the above properties the chemical stability of the propellant is high. At that time, the ingredients of BTX flash-reduced propellant with a high PVC content are determined to be about 77% Pi-BA; 20% PVC; 1.38% DPA; 0.35% ethyl-alcohol; 0.15% ethyl-ether; 1.1% moisture and about 0.02% graphite (addition).
SYNTHESIS OF 2,4,6,8,10,12-HEXABENZYL-2,4,6,12-HEXAAZATETRACYCLO DODECANE USING MELAMINIUM TRI(HYDROGENSULFATE) AS A SOLID ACID CATALYST
In this article, the authors successfully synthesized 2,4,6,8,10,12-hexabenzyl-2,4,6,12-hexaazatetracyclo dodecane (HBIW) through a condensation reaction using melaminium tri(hydrogensulfate) as a solid acid catalyst. The structural characteristics of the product were determined using modern analytical methods: IR, DSC, NMR, and HPLC. Factors influencing the yield of the HBIW synthesis reaction were examined, including catalysts and catalyst amount. The results show that using melaminium tri(hydrogensulfate) as a solid catalyst at 10% mol of glyoxal, yields an optimal yield of 89.86%.
FABRICATION AND STUDY OF OPTICAL PROPERTIES OF TERNARY ZnTeS SEMICONDUCTOR QUANTUM DOTS
Ternary ZnTe1-xSx (0 ≤ x ≤ 1) semiconductor quantum dots (QDs) with varying x composition were successfully fabricated by a wet chemical method in ODE solvent. Their crystal structure, oscillation characteristics, and optical properties were studied through X-ray diffraction patterns (XRD), Raman (RS), absorption spectra (Abs), and photoluminescence (PL). The results showed that ternary ZnTe1-xSx QDs have the zincblende (ZB) structure when x changes. When changing x composition, the emission wavelength of ternary ZnTe1-xSx QDs can change from 408 nm to 526 nm. Evidence of ternary ZnTe1-xSx QDs with uniform Se and S compositions was studied and proven through XRD patterns and RS scattering spectra.
IMPACTS OF HEAT TREATMENT ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF 15%Cr-5%Ni-2%Cu MARTENSITIC STAINLESS STEEL
This study examines how the heat treatment parameters affect the strength and microstructures of 15%Cr-5%Ni-2%Cu martensitic stainless steel. A tempering range of 300-650°C in air cooling and quenching at 1050°C in oil cooling produced the tested specimens. Following heat treatments, optical and scanning electron microscopes, X-ray diffraction analyses, hardness measurements, and tensile testing were used to examine mechanical properties and microstructure. The findings demonstrated that the impact of heat treatment, particularly tempering temperature, on the microstructure and mechanical properties of martensitic stainless steel has been studied. As the tempering temperature rose, the steel's hardness and tensile strength declined. The ductility may be significantly enhanced by raising the tempering temperature. The property was thought to be associated with the microstructure of reversed austenite and tempered lath martensite. A more incredible reversed austenite amount facilitates the increased ductility of martensitic stainless steel.
CARBON FELT MODIFICATION WITH HNO3 FOR THE ELECTRO-FENTON PROCESS OF DEGRADATION ORGANIC POLLUTANTS IN THE AQUATIC ENVIRONMENT
In this study, the authors modified the surface of raw carbon felt (CF) using concentrated HNO3 for durations ranging from 0 to 12 hours at temperatures between 30°C and 90°C. The structural morphology of both the raw CF and the modified CF was characterized using SEM, EDX, XRD, FT-IR, and contact angle methods. The results showed that the CF modified for 6 hours at 30°C exhibited the highest degradation efficiency for LFX. After 90 minutes of reaction, the degradation efficiency for LFX reached 79.65%. Additionally, the modified CF electrodes demonstrated flexibility and high applicability in degrading various organic pollutants such as oxytetracycline, tartrazine, rhodamine B, methyl orange, and methyl blue, achieving degradation efficiencies of 64.64-97.14% after 45 minutes of reaction. Furthermore, long-term stability tests confirmed its relatively stable performance after 3 cycles.
OPTIMIZATION OF SYNTHESIS PARAMETERS AND CHARACTERIZATION OF 4,6-DIHYDROXY-2-METHYL PYRIMIDINE
4,6-dihydroxy-2-methylpyrimidine (MPD) serves as a crucial precursor in the pharmaceutical industry and the synthesis of organic compounds and has recently gained attention as a key intermediate in the production of the energetic material FOX-7. A modern synthetic approach involves the condensation of acetamidine hydrochloride (C2H6N2·HCl) and diethyl malonate (C7H12O4) in an organic alkaline medium; however, limited data are available regarding the technological parameters that govern this process. In this study, the Taguchi experimental design method was employed to determine the optimal conditions for maximizing MPD yield. Validation experiments confirmed that the optimal parameters included a sodium methoxide concentration of 18%, a reaction time of 180 minutes, and a DEM/Ace·HCl molar ratio of 1.4. Under these conditions, a maximum MPD yield of 88.5% was achieved. The synthesized MPD was subsequently identified and characterized through nuclear magnetic resonance (NMR) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and melting point determination. Additionally, powder X-ray diffraction (PXRD) analysis was conducted, with the PXRD pattern of MPD being reported for the first time, providing valuable structural insights into the synthesized compound.
EVALUATION OF THE ABILITY TO TRANSFORM YPERITE BY GREEN DECONTAMINATION BASED ON TUNGSTEN
This article presents the research findings on the evaluation of the ability to transform yperite (HD - a blister agent) of green decontamination based on tungsten. Several key factors influencing the decontaminating potential are thoroughly investigated, including the decontaminant-to-contaminant ratio, reaction temperature, and solution stability. Additionally, the decontamination efficiency on various materials such as paint, alumium, and L1 rubber fabric is also assessed. The results show that at a reaction volume ratio of 1:10, temperature ranging from 10oC to 50oC, and solution stability maintained for 18 hours, the decontamination efficiency on the aluminum surfaces exhibits the highest rate of 99.5%, followed by L1 fabric with 96.2% and paint with 77.8%; the density of decontaminant is recommended to apply 0.2-0.3 L/m2. Moreover, the transformation mechanism of HD by the green decontamination agent is also proposed.
IMPACTS OF TEXTILE MATERIALS ON THE MAIN PROPERTIES OF WEFT KNITTING FABRIC MADE FROM BAMBOO AND POLYAMIDE YARNS
This article presents the evaluation of the influence of textile materials on some physical and mechanical properties of knit fabrics concerning break load, elongation at break, determination of capillarity, air permeability, stretch properties, and elasticity. The evaluations are performed on 3 fabric samples with composition ratio: 70% bamboo/ 20% polyamide/ 10% spandex, 100% polyamide, 80% bamboo/ 20% polyamide, provied by local manufacturers for testing. The research uses the standard test methods of determination of breaking load and elongation at break to TCVN 5795:1994, capillarity to TCVN 5073:1990, air permeability of textile fabrics to TCVN 5092:2009 (ASTM D 73:2004), stretch properties of knitted fabrics having low power to (ASTM D2594), textiles - stretchability of fabrics and ribbons to NF G07-196. Experimental results are synthesized and calculated to compare and analyze the data obtained for each sample of test cloth and the results showed that textile materials and some structural parameters affect some physical and mechanical properties of knit fabrics.
LASER ATTENUATION AND OBSCURANT EFFICIENCY OF SCREENING SMOKE
The concealment capability is one of the most important characteristics of smoke screens used in military camouflage. In this article, the influence of several factors (i.e., the formulation, sample mass, and environmental conditions) on the obscurant capabilities (including the degree of the 1.064 μm laser attenuation, the mass extinction coefficient, the Yield factor, and the Figure of Merit) was investigated and evaluated. The findings indicate that red phosphorus-based smoke compositions exhibit higher obscurant characteristics, providing superior laser attenuation to traditional anthracene-based formulations. The research findings can be used to develop a method for determining the laser attenuation capability of smoke screens.
IMPACTS OF GRAPHENE ON THE COMBUSTION AND INFRARED EMISSION CHARACTERISTICS OF THE PYROTECHNIC COMPOSITION BASED ON MAGNESIUM-TEFLON-VITON
Graphene has been studied and developed for application in many civil and military fields. In particular, the application of increasing the performance of high-energy materials in the military has received much attention in recent years. This article presents studies on the influence of graphene additives on some combustion characteristics and infrared emission of the pyrotechnic composition based on Magnesium-Teflon-Viton (MTV). EDX analysis and SEM images are used to evaluate the distribution of graphene in the pyrotechnic mixture. Graphene additives added to the MTV pyrotechnic mixture did not significantly affect the burning rate, but significantly changed the combustion temperature and infrared emission of the pyrotechnic compositions.
SYNTHESIS AND ANTIMICROORGANISM ACTIVITY OF MIRAMISTIN
Quaternary ammonium compounds are known for their rich physicochemical and biological characteristics, and are widely used in many areas of life such as surface active properties and anti-microbial properties. Miramistin is a typical compound with full physicochemical and biological properties of quaternary amino compounds, has antimicrobial properties and is widely used in the medical and pharmaceutical fields. This article presents the results of research on the synthesis and optimization of the miramistin synthesis process based on the use of different starting compounds. In addition, the antimicroorganism properties of miramistin were tested and showed potential application as an antimicroorganism.
DESIGN AND FABRICATION OF SHAPE MORPHING MAGNETO-IMPEDANCE MAGNETIC SENSOR
The magnetoimpedance (MI) effect is characterized by the alteration in the impedance of soft magnetic materials when subjected to a magnetic field while a high-frequency alternating current flows through them. In this study, we engineered two distinct sensor architectures utilizing amorphous FeCSi magnetic ribbon: a single-bar structure with the dimension of 10 mm × 90 μm × 20 μm and a meander structure consisting of 13 parallel single bars. These structures were miniaturized through advanced techniques combining laser engraving and chemical etching. The magnetic analysis reveals that the meander structure exhibits a pronounced dependency on the angle θ between the magnetic field and the sensor orientation, enhancing its soft magnetic properties by up to fivefold compared to the single-bar design. This enhancement might be attributed to a reduction in the demagnetization effect and shape anisotropy energy within the meander sensor. Furthermore, the analysis of the MI effect indicates that the resonance frequency remains unaffected by external magnetic fields for both sensor types. Notably, the meander sensor demonstrates exceptional MI ratio values exceeding 82%, representing a remarkable 24-fold increase over the 3.5% observed in the single-bar sensor. Additionally, the isotropy - quantified as the MI ratio's dependence on angle θ, and magnetic field sensitivity are significantly improved in the meander configuration. These advancements in soft magnetic and physical properties are correlated to the domain structure of the sensor, particularly its transverse magnetic permeability, as evidenced by micromagnetic simulations conducted using Mumax3. With its superior MI ratio, isotropy, and heightened magnetic field sensitivity, the meander-type magnetic field sensor presents substantial potential for applications across diverse fields, ranging from biological systems to specialized practical missions.
RECONSTRUCTION OF THE SURFACE PROFILE OF OPTICAL-MECHANICAL STRUCTURE WITH WHITE LIGHT INTERFERENCE BY DEEP LEARNING U-NET MODEL
This research proposes a method to accurately determine the location of the interference signal peak in white light interferometry. This improves the accuracy and resolution of the measurement, enabling precise measurement and reconstruction of three-dimensional microstructures on optical surfaces. By using a deep learning algorithm with a U-net neural network architecture to generate a predicted signal that closely matches the reference signal, combined with Fast Fourier Transform to filter noise and fit the proposed function, the exact location of the envelope signal peak is determined, providing information about the height of the point. This method can achieve an accuracy of around 0.9 nanometers at a noise level of 50 dB, which is over 40% more accurate than the traditional Fourier transform method at various noise levels. The persistent issues of the traditional Fourier transform method, such as determining the location of the interference signal peak at a signal position and the accuracy being heavily influenced by noise and the fitting signal, are effectively addressed.
MULTI-SENSOR CAMERA MODEL FOR CONTROLLING COORDINATES OF POINTS ON THE SURFACE OF TELESCOPES
A new optoelectronic system for measuring the reflective mirror surface distortion of large telescopes is discussed in this study. This system comprises a multi-matrix structure of CMOS sensors, each sensor responsible for capturing an image of a control point on the mirror surface through a common objective. Simulation and calculation studies show that during operation, the position of the multi-sensor camera on the supporting ring is determined by control points on the telescope surface. The more control points, the higher the accuracy of the calculations. Simulation results indicate that the camera position error falls within acceptable limits when using 5 or more control points. Experimental results show that when calculating simultaneously with 3 control points, the error in determining the angular position of the camera reaches a value of  = 0.302 arc minutes, which is 2 - 2.5 times smaller than when calculating with only one control point.
FABRICATION AND ELECTROCHEMICAL CHARACTERIZATION OF CATHODE MATERIAL Na1.0Li0.05Mn0.6Ni0.3Al0.05O2 FOR SODIUM ION BATTERIES
Sodium-ion batteries exhibit structural and operational similarities to lithium-ion batteries, and they are increasingly recognized as a viable alternative to lithium-ion batteries. In this context, it is imperative to investigate electrode materials specific to sodium-ion batteries to enhance their capacity, stability, and cost-effectiveness, thereby facilitating their commercialization in the near future. In pursuit of these objectives, this study successfully synthesized Na1.0Li0.05Mn0.6Ni0.3Al0.05O2using a sol-gel method followed by calcination. The resulting material demonstrated a P2 crystal structure and achieved a maximum specific capacity of 142.2 mAh g-1 at a discharge current density of 10 mA g-1 within the voltage range of 1.5 to 4.1 V. Furthermore, the material exhibited commendable stability, maintaining 89.1% capacity retention after 50 cycles and 76.4% after 100 charge-discharge cycles at a current density of 15 mA g-1 within the same voltage range, indicating its potential as a cathode material for sodium-ion batteries.
SYNTHESIS AND CHARACTERIZATION OF POLYEPICHLOROHYDRIN DIOLS
Polyepichlorohydrin (PECH) is a functional polymer with high value in energy materials. Cationic ring-opening polymerization of epichlorohydrin (ECH) with a diol initiator and Lewis or protic acids catalyst, proceeds through an activated monomer mechanism (AM) allowing control of the polymer's average molecular weight and polydispersity index. In the present investigation, PECH diol was synthesized under the catalysis of boron trifluoride etherate, with the ECH monomer:ethylene glycol as an initiator molar ratio of 1:0.045, achieving a low molecular weight Mn = 1935 g/mol, low polydispersity index PDI = 1.25, predominantly in the linear chain configuration with the terminal hydroxyl group.
STUDYING THE ELECTROCHEMICAL PROPERTIES OF POTASSIUM-DOPED SODIUM-MANGANESE OXIDE CATHODE MATERIALS FOR SODIUM-ION BATTERIES
The development of layered sodium manganese oxide cathode materials with high capacity and long life is one of the keys to boosting the performance of sodium-ion batteries (SIBs), but it remains a great challenge. In this work, a potassium doped P2-type sodium manganese oxide, Na0.8K0.1Mn0.9O2 (NKMO), is developed as a high-capacity and long-lasting cathode for high-performance SIBs. Sodium-potassium-manganese oxide Na0.8K0.1Mn0.9O2 was synthesized by a conventional solid-state reaction method. Crystal structure and morphology of the NKMO material were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The NKMO material was utilized to fabricate CR2032-type coin cells, and later evaluated for its electrochemical characteristics. The electrochemical characteristics of NKMO were evaluated through cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charging-discharging (GCD) at different current densities on a NEWARE battery testing system. The NKMO material had a superior initial charge and discharge capacity, approximately 130 mAh.g-1 and 125 mAh.g-1, respectively, within the voltage range of 1.5-4 V at a current density of 0.1 C. Remarkably, the capacity remained stable at 100 mAh.g-1 even after 100 cycles. These findings indicate that NKMO is a highly promising cathode material for sodium-ion batteries.
CONTINUOUS MONITORING OF DISSOLVED OXYGEN CONCENTRATION USING LOW-COST MULTISPECTRAL SENSORS
This study proposed an approach for continuously monitoring dissolved oxygen concentration using absorption spectroscopy with a low-cost multispectral sensor. An experimental system was built to investigate the correlation between dissolved oxygen concentration and absorbance of several wavebands in the visible and near-infrared regions. An optimized linear regression model with four wavebands at 460, 485, 585, and 900 nm gave the best prediction results with coefficient of determination and root mean square error of 0.85 and 0.68 mg/L, respectively. The experimental results demonstrated that the proposed absorption spectroscopy with a low-cost multispectral sensor has great potential for continuously monitoring dissolved oxygen concentration in water in a non-contact manner.
THE EFFECT OF ANNEALING REGIME ON THE PRECIPITATION OF FeCoNiAl0.75Nb0.25 HIGH ENTROPY ALLOY
This paper investigates the effect of the annealing regime on the precipitation of FeCoNiAl0.75Nb0.25 high entropy alloy. The as-cast microstructure consists of coarse dendritic phases that are replaced by equiaxed morphology, and the distribution of the interdendritic phase becomes regularly better with increasing time and annealing temperature up to 825ºC. The precipitated process begins at 700ºC for 8 hours, shortening to 4 hours when the annealing temperature increases. The size of this phase is only a few μm. The fraction of the precipitated phase increases and the size of the dendritic phase is reduced as the annealing temperature is up to 825ºC, while this size rises in the 925ºC/16 hours regime. The microstructure is coarse, and the precipitated phase gradually disappears when the annealing is at 1000ºC. The HV3 hardness of the alloy increases with annealing time when the temperature is lower than 825ºC and reaches the highest value of ~ 614 kg/mm2 at 600ºC/ 24 hours; this value begins to decrease for the 925ºC/16 hours regime. Meanwhile, the hardness gradually decreases with increasing annealing time at 1000ºC. It can be expected due to the rapid coarsening of the dendritic phase, the decrease in the proportion of the precipitated phase in the alloy, and the appearance of plastic flow phenomena at grain boundaries.
INVESTIGATION OF FLUORESCENCE EFFECTS OF EU(TTA)3(H2O)2 AND EU(TTA)3(PHEN) COMPLEXES IN THE PRESENCE OF OTHER LANTHANIDE METAL IONS
In this study, we explore the fluorescence behavior of Eu(TTA)3(H2O)2 and Eu(TTA)3(Phen) complexes in the presence of various other lanthanide metal ions, with the objective of ensuring diversity in the raw material sources for military purposes. The fluorescence properties of these complexes are investigated to understand their potential interactions with other lanthanide ions and their effects on fluorescence emission. Spectroscopic analysis is conducted to examine how the presence of different lanthanide ions influences the fluorescence emission of Eu(TTA)3(H2O)2 and Eu(TTA)3(Phen) complexes. Product structure characteristics are determined by IR, UV-Vis, and EDX spectroscopy. The optical properties of the complex are studied by fluorescence spectroscopy. The results indicate that the structure EuxM1-x(TTA)Phen (M: Tb, Nd, Pr; x = 0.1; 0.5; 0.9; 1.0) gives stronger luminescence at ignited wavelengths λex = 385 nm.
DETERMINATION OF 4-METHYLIMIDAZOLE AND 2-ACETYL-4-TETRAHYDROXY-BUTYLIMIDAZOLE IN CARAMEL COLOR AND PRODUCTS BY LIQUID CHROMATOGRAPHY-MASS SPECTROMETRY
The simultaneous determination of 4-MEI and THI in caramel and products by LC-MS/MS was developed with several advantages of simplicity, selectivity, and high sensitivity. Chromatographic separation was performed using a C18 column (100 × 2.1 mm, 1.7 μm), with a mobile phase consisting of ammonium formate pH = 4 and acetonitrile containing 0.1% formic acid employing a gradient elution mode. The analytes were detected using an MS/MS double mass spectrometer with an ESI+ ionization source. Samples were cleaned and enriched on a SPE MCX column. Method validaion resulted in a linear range of 5.0 - 500 ppb for 4-MEI, and 1.0 - 500 for THI, with LODs of 0.30 g/kg for THI and 1.5 μg/kg for 4-MEI, and LOQs of 1 μg/kg for THI and 5 μg/kg for 4-MEI. Repeatability and reproducibility for 4-MEI ranged from 2.9% to 9.1% and 2.9% to 11.8%, respectively, and for THI from 3.5% to 9.4% and 4.8% to 11.5%, respectively. Recovery rates for with 4-MEI and THI met AOAC's requirements, ranging from 82.7% to 106.4% and 87.2% to 109.7%, respectively. Application of the analytical method for 24 market products, including caramel, beverages, condiments, and cakes, showed that the 4-MEI and THI concentrations in consumer products were within the permissible limits, while pure caramel samples exceeded the permissible limits for THI concentrations.
FORMULATION AND SEVERAL CHARACTERISTICS OF THE SMOKE COMPOSITIONS BASED ON RED PHOSPHORUS
Red phosphorus is an important ingredient in the manufacture of pyrotechnic smoke and is likely to be in service for many years. One of the most effective ways to use smoke screens is to protect special vehicles from laser and infrared guidance systems. In this work, the formulation, obscurant and emission characteristics of the smoke composition in smoke devices used in special vehicles were determined and evaluated. Research results show that the smoke composition comprises red phosphorus, sodium nitrate, Al-Mg alloy, and fluorine-containing polymers. The outcomes also demonstrated that the smoke screen has a high attenuation capability to 1.064 μm laser radiation and strong infrared emission in both wavelength ranges of 3 - 5 μm and 8 - 14 μm.