Journal of Science and Technique: Section on Physics and Chemical Engineering

DESIGN AND FABRICATION OF THE THERMAL IMAGING SYSTEM FOR TANK SIGHTS

Van Huy Mai — 2025-11-05

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.

HIGHLY SELECTIVE NO2 GAS SENSOR OPERATING AT ROOM TEMPERATURE WITH PPB-LEVEL DETECTION SENSITIVITY BASED ON ZnO NANOPARTICLES

Van Cuong Nguyen — 2025-11-05

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.

EFFECT OF COMPRESSION FORCE IN THE FABRICATION OF MEMBRANE ELECTRODE ASSEMBLY BY DECAL METHOD FOR PROTON EXCHANGE MEMBRANE WATER ELECTROLYZER

Chi Linh Do — 2025-11-05

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.

EFFECT OF SILICON ADDITION ON DEZINCIFICATION OF L72 BRASS IN CHLORIDE MEDIA

Minh Tien Ngo — 2025-11-05

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.

COMPARATIVE ANALYSIS OF TiO2 NANOTUBE LAYERS FORMED BY SINGLE- AND TWO-STEP ANODIZATION: SURFACE MORPHOLOGY, CORROSION RESISTANCE, AND CELLULAR RESPONSE

Van Toan Le — 2025-11-05

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.

INVESTIGATION OF ELECTROCHEMICAL CHARACTERISTICS of α-NaxMnO2 CATHODES FOR SODIUM-ION BATTERIES

Van Ky Nguyen — 2025-11-05

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.

GREEN SYNTHESIS OF NANO-ZERO-VALENT IRON USING CLEISTOCALYX OPERCULATUS EXTRACT FOR EFFICIENT RHODAMINE B DEGRADATION

Duc Thieu Nguyen — 2025-11-05

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.