Tạp chí của Trường Đại học Kỹ thuật Lê Quý Đôn
EFFECT OF ANNEALING ON THE MICROSTRUCTURE AND HARDNESS OF THE FeCoNiCrAl0.25Mn0.75 HIGH ENTROPY ALLOY
In this study, the effect of annealing treatment on the microstructural evolution and hardness of the FeCoNiCrAl 0.25 Mn 0.75 high-entropy alloy was systematically investigated. The alloy was examined in the as-cast condition and after annealing at 600, 700, and 800°C for 4, 8, 16, and 24 h, respectively. The as-cast microstructure primarily consisted of a FeCoNi-rich FCC solid solution accompanied by a minor fraction of an AlNi-rich BCC phase. The precipitation of needle-like AlNi-rich BCC phases within the FCC matrix was initiated after annealing at 600°C for 16 h, whereas similar precipitates were observed after only 4 h at annealing temperatures of 700 and 800°C. The volume fraction of the precipitated phase increased progressively with annealing time at all investigated temperatures, reaching a maximum value of approximately 52% under the 800°C/24 h condition. This pronounced precipitation behavior contributed significantly to the strengthening of the alloy, resulting in a maximum hardness of about 205 HV3, compared to 139 HV3 in the as-cast state. These results demonstrate that annealing treatment plays a crucial role in tailoring the microstructure and enhancing the mechanical performance of the FeCoNiCrAl 0.25 Mn 0.75 high-entropy alloy, providing valuable insights for the design and development of structural materials.
Section on Physics and Chemical Engineering (JST-PCE)
INFLUENCE OF FORMULATION PARAMETERS ON THE COMBUSTION AND OBSCURATION CHARACTERISTICS OF RED PHOSPHORUS/PYROGEL-BASED SMOKE COMPOSITIONS
This study investigates the influence of Mg particle size and oxidizer type on the combustion and obscuration characteristics (including ignition temperature, heat of combustion, mass consumption rate, flame temperature, laser attenuation capability, and infrared screening efficiency) of red phosphorus (RP)/pyrogel-based smoke compositions. Samples were prepared using Mg powders with mean particle sizes ranging from 50.2 to 529.5 µm and four different oxidizers (NaNO 3 , KNO 3 , Ba(NO 3 ) 2 , and Sr(NO 3 ) 2 ). The results showed that Mg particle size strongly affected the mass consumption rate (0.027–0.083 g.s -1 ) and smoke-screen formation rate, while exerting negligible effects on ignition temperature, heat of combustion, and flame temperature. Among the oxidizers tested, NaNO 3 exhibited the most favorable smoke-generation performance, characterized by a higher mass consumption rate and the shortest time to achieve over 90% obscuration (18 s). The RP/pyrogel smoke screens exhibited effective infrared shielding in both the 3–5 µm and 8–12 µm bands, with screening times of approximately 30 s and 20 s, respectively. These findings provide a scientific basis for the selection and optimization of RP/pyrogel-based formulations for smoke-screen generation aimed at infrared shielding and laser energy attenuation.
FABRICATION OF FeCo LAYERED DOUBLE HYDROXIDE (LDH) FOR HIGH-PERFORMANCE ENERGY STORAGE
The development of high-performance electrode materials is essential for next-generation energy-storage technologies. In this work, FeCo layered double hydroxide (FeCo-LDH) was successfully synthesized using a simple co-precipitation method. Structural characterizations by XRD and FT-IR confirmed the formation of a well-defined LDH phase with characteristic basal reflections, metal–oxygen vibrations, and interlayer hydroxyl groups. SEM analysis revealed a loosely stacked nanosheet morphology that provides abundant electroactive surface sites, while EDX confirmed the uniform distribution of Fe and Co without detectable impurities. Electrochemical measurements demonstrated the outstanding pseudocapacitive performance of FeCo-LDH. The material exhibited pronounced redox activity in CV, distinct potential plateaus in GCD, and low charge-transfer resistance in EIS. A high specific capacitance of 1409 F·g⁻¹ at 10 A·g⁻¹ was achieved, indicating excellent rate capability and efficient ion diffusion. These results confirm that FeCo-LDH is a promising electrode material for high-performance supercapacitors and other advanced energy-storage applications.
EFFECT OF MULTILAYER LAMINATION ON THE PERFORMANCE AND SENSITIVITY OF FLUXGATE MAGNETIC SENSORS
This study investigates the influence of multi-layered ferromagnetic core structures on the performance of fluxgate magnetic sensors. Utilizing ultra-soft Metglas amorphous ribbons, core configurations ranging from one to five layers were fabricated and analyzed through a combined approach of finite element numerical simulation and experimental characterization. Simulation results reveal that increasing the number of core layers significantly enhances the average demagnetizing factor (nearly doubling for the 5L structure compared to the 1L), leading to a 12% reduction in effective magnetic induction. Experimental data demonstrate that the single-layer configuration achieves an optimal sensitivity of approximately 1200 V/T with a resolution of 300 nT. Conversely, increasing the number of magnetic layers extends the linear dynamic range from ±0.25 mT to over ±0.9 mT, albeit at the cost of reduced sensitivity 54 V/T for the 5L structure. This research confirms the trade-off between sensitivity and operating range modulated by multi-layer architectures, providing a critical foundation for optimizing fluxgate sensors for specific application requirements.
SYNTHESIS AND CHARACTERIZATION OF rGO AND NICKEL-COBALT OXALATE COMPOSITE MATERIALS FOR SUPERCAPACITOR ELECTRODE APPLICATIONS
In this work, a composite material comprising nickel-cobalt oxalate and graphene (rGO@NiCo-Ox) was synthesized via a hydrothermal method for application as a supercapacitor electrode. Comprehensive characterizations of the structural and compositional properties were conducted using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetric analysis (TGA). The electrochemical behavior was systematically evaluated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The experimental results reveal that the incorporation of graphene significantly reduces both the electrical resistance and particle size of the nickel-cobalt oxalate component, resulting in the rGO@NiCo-Ox composite demonstrating markedly improved electrochemical performance compared to pristine NiCo-Ox. Notably, the rGO@NiCo-Ox electrode achieves a maximum specific capacity of 652.65 C g -1 at a current density of 1 A g -1 , representing an enhancement of 123% over the capacity of NiCo-Ox. In addition, the composite exhibits superior cycling stability relative to the pure NiCo-Ox electrode. These findings suggest that the integration of battery-type active materials with graphene offers a compelling strategy for augmenting the electrochemical properties of single-component systems, and highlight the rGO@NiCo-Ox composite as a highly promising electrode material for high-performance supercapacitors.
OPTIMIZATION OF THE PROCESS PARAMETERS FOR SYNTHESIS OF 3,6-BIS(1H-1,2,3,4-TETRAZOL-5-YLAMINO)-S-TETRAZINE
3,6-bis(1H-1,2,3,4-tetrazol-5-ylamino)-1,2,4,5-tetrazine (BTATz) is a high-nitrogen energetic material with attractive properties including low sensitivity, excellent gas-generating capacity, and environmentally friendly decomposition. In this work, the synthesis of BTATz from 3,6-bis(3,5-dimethylpyrazol-1-yl)-1,2,4,5-tetrazine (BDT) and 5-aminotetrazole (5-AT) in sulfolane was optimized using the Taguchi method with an L9(3 3 ) orthogonal array, considering three factors: BDT/5-AT molar ratio, reaction temperature, and reaction time. Statistical analysis revealed that the molar ratio of BDT/5-AT was the most influential factor on yield, while reaction time exhibited the least effect. The optimal conditions (BDT/5-AT = 2.8, temperature = 135°C, time = 20 h) afforded a maximum experimental yield of 88.3%, which agreed well with the predicted value of 86.4%. The ignition temperature of ~274°C remained unchanged across all conditions, confirming the consistent quality of the synthesized product. Structural characterization by FT-IR and NMR supported the successful preparation of BTATz. Sensitivity tests indicated relatively low impact and friction sensitivity, highlighting BTATz as a promising candidate for advanced energetic formulations.
NANO-ZnO IMMOBILIZED ON BIO-ACTIVATED CARBON FROM ROBUSTA COFFEE HUSK FOR PHOTOCATALYTIC DEGRADATION OF FLUORESCENT DYE
ZnO's photocatalytic properties make it a widely used semiconductor, while bio-activated carbon (BAC) from agricultural waste is emerging as a sustainable and cost-effective photocatalyst substrate. This study explores the preparation and characterization of a nano ZnO/BAC composite from coffee husks for efficient degradation of Rhodamine B (RhB) under simulated sunlight. BAC was produced by carbonizing coffee husks at 900°C in argon and activating with HCl. ZnO nanoparticles (20–100 nm) were deposited on BAC, confirmed by SEM images. UV-Vis DRS analysis indicated strong ZnO absorption below 400 nm, enhancing photocatalytic performance. RhB degradation followed pseudo-first-order kinetics ( k 1 = 0.0206 min -1 , R² = 0.9894), achieving 91.46% removal in 120 minutes, particularly rapid in the first 40 minutes. The composite showed good reusability, retaining over 88% efficiency after seven cycles. These results highlight ZnO/BAC as a promising sustainable photocatalyst for dye removal in wastewater treatment.
REMOVAL OF MERCURY(II) FROM ACID MINE DRAINAGE BY MODIFIED OYSTER SHELL BIOSORBENT
Mercury (Hg 2+ ) contamination in acid mine drainage (AMD) remains a critical environmental concern that requires cost-effective and sustainable treatment solutions. In this study, phosphate-modified oyster shell (MOS) was synthesized and evaluated as a low-cost biosorbent for Hg²⁺removal. Characterization results confirmed the successful formation of calcium phosphate phases containing active PO 4 3 ⁻and OH⁻groups, which served as the primary binding sites for mercury. Batch adsorption experiments showed rapid uptake, reaching equilibrium within 30 min, with removal efficiencies consistently above 90% across initial concentrations of 5–30 mg.L -1 . The optimal pH range was determined to be 5–7, where reduced proton competition enabled effective ion exchange and complexation with phosphate groups – conditions well aligned with partially neutralized AMD. Adsorption capacity increased with MOS dosage, with an optimal range of 1.0–1.5 g.L -1 . Regeneration experiments demonstrated that MOS retained significant performance after multiple adsorption–desorption cycles, indicating good structural stability despite the acidic environment. These results highlight MOS as a promising, practical, and sustainable biosorbent for mercury removal in AMD treatment applications.
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 and capping agent. The synthesized nZVI was characterized by XRD, SEM-EDS, FT-IR, and BET. The XRD pattern confirmed the formation of crystalline α-Fe⁰, while 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 experiments revealed that while nZVI alone primarily adsorbed Rhodamine B (RhB) and H₂O₂ alone exhibited limited oxidation, the combined nZVI/H₂O₂ system achieved nearly complete decolorization within 50 min. The enhanced efficiency was attributed to a heterogeneous Fenton-like process generating highly reactive ·OH radicals. These findings demonstrate that Cleistocalyx operculatus-mediated nZVI offers a sustainable and effective approach for the removal of organic dyes from wastewater, highlighting its potential in 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-Na x MnO 2 (x = 0.7-1.0) cathode materials synthesized via the sol-gel method. The α-Na x MnO 2 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-Na x MnO 2 materials were investigated using CR2032 coin cells, in which the cathodes were fabricated from the synthesized α-Na x MnO 2 materials. The α-Na x MnO 2 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 Na 0.8 MnO 2 (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-NaxMnO 2 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 (TiO 2 1S) and two-step (TiO 2 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 TiO 2 2S sample. Furthermore, TiO 2 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/cm 2 .
HIGHLY SELECTIVE NO2 GAS SENSOR OPERATING AT ROOM TEMPERATURE WITH PPB-LEVEL DETECTION SENSITIVITY BASED ON ZnO NANOPARTICLES
In this work, we reported a high-selectivity nitrogen dioxide (NO 2 ) gas sensor that operates directly at room temperature without catalyst or illumination. The NO 2 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 NO 2 , 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 NO 2 , while the interaction with other gases such as H 2 S, NH 3 , SO 2 , CH 4 , C 3 H 8 , and CO 2 was negligible. This room-temperature, easily fabricated sensor offered a promising solution for cost-effective, real-time NO 2 monitoring in various applications, particularly those requiring high sensitivity at low NO 2 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.
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, we 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 ZnTe 1-x S x (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 ZnTe 1-x S x QDs have the zinc-blende (ZB) structure when x changes. When changing x composition, the emission wavelength of ternary ZnTe 1-x S x QDs can change from 408 nm to 526 nm. Evidence of ternary ZnTe 1-x S x 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, we modified the surface of raw carbon felt (CF) using concentrated HNO 3 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, and FT-IR 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 81.07-97.14% after 45 minutes of reaction. Furthermore, long-term stability tests confirmed its relatively stable performance after 3 cycles of reuse.
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 10 o C to 50 o C, 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/m 2 . Moreover, the transformation mechanism of HD by the green decontamination agent is also proposed.
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 cm 3 /s/cm 2 . 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.
IMPACTS OF TEXTILE MATERIALS ON THE MAIN PROPERTIES OF WEFT KNITTING FABRIC MADE FROM BAMBOO AND POLYAMIDE YARNS
This article represents 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.
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 ´ %)]. 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).
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 COMBUSION 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 INVESTIGATION OF 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.
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 acetamidinium chloride (C 2 H 7 ClN 2 ) and diethyl malonate (C 7 H 12 O 4 ) 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.
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.
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 an 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 nM = 1935 g/mol, low polydispersity index PDI = 1.25, predominantly in the linear chain configuration with the terminal hydroxyl group.