Journal of Energy, Material, and Instrumentation Technology

Exponential-Offset Modelling and XRD Correlation of SOH Degradation in LiFePO4 Batteries under Extreme Loading

2025-09-30T04:10:41+00:00

Understanding the relationship between electrochemical degradation and structural changes is critical for improving the reliability of lithium-ion batteries. In this study, the state of health (SOH) of 18650-type lithium iron phosphate (LiFePO₄, LFP) cells was evaluated under extreme loading using discharge resistances of 2.5 Ω and 0.005 Ω. The SOH decreased sharply after the first cycle and then declined more gradually, and the degradation trend was well described by an exponential-offset model with RMSE = 2.87, MAE = 2.25, and R² = 0.90. Structural analysis was performed by X-ray diffraction (XRD) on electrode samples taken after one discharge at 2.5 Ω (L1), 100 discharges at 2.5 Ω (L100), and one discharge at 0.005 Ω (LD). The XRD results confirmed that the main phase was graphite, but with reduced peak intensities, peak broadening, and increased background noise, indicating crystallinity loss and partial amorphization. These findings demonstrate that SOH degradation is strongly correlated with the decline in crystallinity, and that extreme loading can trigger significant structural deterioration even within a single discharge.

Morphological Study of Electrospun Polyvinylpyrrolidone Fibers at High Concentration Using Water and Ethanol Solvents

2025-09-05T04:17:42+00:00

In this study, polyvinylpyrrolidone (PVP) (Mw ~40,000 g/mol) fibers were fabricated using distilled water and ethanol via an electrospinning approach. Morphological evaluations were carried out with a Scanning Electron Microscopy (SEM). Fiber diameters were analyzed with ImageJ. Solution Concentration of PVP with solvents adjusted to 50% (m/v), respectively. Then, the solution was electrospun with voltages of 8 and 12 kV. PVP/distilled water solution produced a relatively regular fiber network with enlarged junctions at 8 kV. However, it was ribbon-like, bead-like, and film-like in voltages of 12 kV. This structure was attributed to high surface tension and slow solvent evaporation. Another solution, PVP/ethanol, produced a relatively regular fiber network at 8 kV. The structure was different at 12 kV voltages. Globular and particle-like morphologies appear in these conditions. Fiber diameter was analyzed in the layers formed under 8 kV electrospinning conditions. The fiber diameter in PVP/distilled water was 1.05 ± 0.50 µm. Meanwhile, the fiber diameter in PVP/ethanol was 2.46 ± 0.64 µm. Although the fiber diameter was larger in PVP/ethanol, the resulting fiber was more continuous and more stable.

Enhancement of Corrosion Resistance and Electromagnetic Wave Absorption in Aluminium 6061 through Plasma Electrolytic Oxidation Coating with Ethylenediaminetetracetic Acid

2025-08-11T02:47:17+00:00

Aluminium 6061 is well known for its good tensile strength and high corrosion resistance due to the natural protective oxide layer formed on its surface. However, the phenomenon of corrosion can still occur, particularly in aggressive environments, leading to material degradation. To further enhance corrosion resistance, a coating using the Plasma Electrolytic Oxidation (PEO) method with a concentrated solution of Na2SiO3, KOH, and EDTA was applied for 4 minutes. The addition of EDTA plays a crucial role not only in improving corrosion resistance but also in influencing the dielectric properties of the material, which subsequently affects the absorption of electromagnetic waves. Corrosion testing using the Tafel Polarization method revealed that the PEO coating with EDTA resulted in a more positive corrosion potential and a lower current density compared to untreated Aluminium 6061. Furthermore, EDTA enhances the porosity of the oxide layer, promoting the formation of micro-pores on the surface, which can trap corrosive agents and mitigate corrosion phenomena. Testing with a Vector Network Analyzer (VNA) at frequencies ranging from 8 GHz to 12 GHz demonstrated that the material exhibits an electromagnetic wave absorption of -1 dB. Overall, the application of PEO coating with EDTA significantly improves both corrosion resistance and electromagnetic wave absorption, making it suitable for various applications in the automotive, electronics, and energy industries.

Fabrication of Bioceramic Carbonated Hydroxyapatite–Chitosan Composite Scaffold Derived from River Snail Shells via Freeze-Drying for Bone Grafting Applications

2025-09-21T04:36:09+00:00

The prevalence of bone fractures in Indonesia has increased by up to 8.5%, making cost-effective biomaterial alternatives for bone grafting applications necessary. This study aims to synthesize a hydroxyapatite carbonate (CHAp) composite scaffold from river snail shells (Semisulcospira libertina) and chitosan via freeze drying for bone tissue engineering applications. The shells were calcined at 1000°C to produce CaO, which was then synthesized into CHAp via a precipitation method with a Ca:P:CO3 molar ratio of 1.67:1:1. The CHAp/chitosan scaffold was fabricated at a 2:1 (w/w) ratio using freeze drying at -80°C for 72 hours. Characterization was performed using XRD, FTIR, SEM-EDX, and mechanical and degradation testing. XRD results showed that CHAp formed according to the JCPDS No. 09-0432 standard, exhibiting 85.61% crystallinity, a crystal size of 17.07 nm, and type B carbonate substitution. FTIR spectra confirmed the presence of PO4(3-), CO3(2-), and OH(-) groups. SEM-EDX analysis revealed a Ca/P ratio of 1.74 and a carbonate content of 4.06%. The scaffold has a porous structure with pore sizes ranging from 3.6 to 14 um. It has a compressive strength of 0.255 MPa, a maximum strain of 70.71%, and a gradual degradation profile reaching 40.79% in 48 hours. These results demonstrate that the CHAp/chitosan scaffold fabricated from river snail shells has physicochemical and mechanical properties suitable for bone grafting applications. This material offers a sustainable, cost-effective alternative for bone tissue regeneration.

Improvement of TiO2 Performance with 10% Cu–TiO2/BiVO4 Heterojunction Composite Using Sonication in Photoelectrochemical Water Splitting

2025-09-05T03:55:34+00:00

The global energy crisis, driven by the depletion of fossil fuels, has accelerated the search for renewable energy solutions, including hydrogen production via solar-driven photoelectrochemical (PEC) systems. A major limitation of PEC is the UV-only activity of semiconductors such as TiO₂. This study investigates the performance enhancement of TiO₂ through the formation of a Cu-TiO₂/BiVO₄ heterojunction composite with 10% Cu doping and sonication treatment. Cu doping reduces the band gap and extends light absorption into the visible region, while BiVO₄ promotes effective charge separation. SEM-EDS analysis revealed a more uniform particle distribution in the sonicated sample, and UV-Vis DRS confirmed a substantial band gap narrowing from 2.97 eV to 2.02 eV. PEC testing in a 0.5 M NaCl solution showed that the sonicated composite achieved the highest and most stable photovoltage (0.78 V) along with visible hydrogen bubble formation, indicating efficient light-to-hydrogen conversion. These findings demonstrate that sonication plays a crucial role in improving particle dispersion, suppressing agglomeration, and reinforcing the TiO₂/BiVO₄ heterojunction, highlighting its potential as a self-biased photoanode for sustainable hydrogen production.

The Effect of Biaxial Strain on The Thermoelectric Properties of 2D SiBi

2025-03-05T11:32:16+00:00

This study investigates the electronic and thermoelectric properties of two-dimensional silicon bismuth (2D SiBi) using first-principles Density Functional Theory (DFT) calculations. The 2D SiBi monolayer is identified as a semiconductor with an indirect band gap of 0.67 eV. Solving the Boltzmann transport equation reveals outstanding thermoelectric performance, evidenced by high Seebeck coefficients of 1243.79 µV/K (p-type) and 1217.23 µV/K (n-type) at room temperature. Most significantly, the application of a modest -1% biaxial compressive strain induces a substantial enhancement in these values, elevating them to 1361.75 µV/K and 1371.85 µV/K for p-type and n-type carriers, respectively. These results demonstrate that mechanical strain is an effective strategy for tuning and optimizing the thermoelectric efficiency of 2D SiBi, positioning it as a highly promising material for next-generation thermoelectric devices.