International Journal of Materials and Mechanical Structures Engineering

Structural Analysis and Temperature-Dependent Impedance Behavior of BiFeO₃ Nanoparticles for PV Application

Md Samiul Islam — 2026-07-01

Silicon semiconductor remains the principal material for commercial PV (photovoltaic) cells. Alternative PV materials are being actively explored to reduce dependence on silicon-based PV cells and improve future cell performance. Bismuth ferrite (BiFeO₃, BFO) has attracted consideration as a lead-free multifunctional oxide material for PV applications because of its preferable bandgap of 2.0 to 2.7. In this work, BiFeO₃ nanoparticles were synthesized by the sol–gel method and annealed at 600 °C, and their structural, morphological and impedance characteristics were examined. X-ray diffraction (XRD) analysis confirmed the formation of crystalline BiFeO₃ nanoparticles, confirming the rhombohedral R3c phase, with prominent diffraction peaks around 31.8° and 32° (2θ). Field-emission scanning electron microscopy (FESEM) revealed the surface morphology and particle size of 138 nm of the synthesized nanoparticles. The impedance behavior of BiFeO₃ was further investigated through frequency-dependent impedance measurements at 100, 200 and 300 °C. The impedance response showed a clear dependence on frequency and temperature. At 100 °C, impedance decreased continuously with increasing frequency. However, at 200 and 300 °C, the impedance showed dual behavior, first increased and then decreased with frequency. The structural development, nanoparticle morphology and temperature-dependent impedance response show that sol–gel-synthesized BiFeO₃ nanoparticles may be useful for PV cells and related electronic devices.

Investigation of Corrosion Behavior of Mild Steel in Simulated Atmospheric Environments: A Review of Salinity Effects

Emekwisia, Chukwudubem C. — 2026-07-30

This review provides a systematic structural evaluation of the atmospheric corrosion mechanisms of low-carbon mild steel, focusing exclusively on the impacts of airborne marine salinity and localized chloride ion deposition. Structural steel elements located within maritime coastal environments undergo aggressive electrochemical deterioration driven by the high loading of windborne halide aerosols. This paper organizes and evaluates empirical data from standardized simulation configurations to isolate the chemical, thermodynamic, and microstructural consequences of chloride contamination on the structural iron matrix. Experimental data synthesis reveals that elevated chloride deposition rates up to 120 mg/m²/day shift uniform surface thinning to severe localized pitting, reaching a maximum measured pit depth of 0.85 mm. Under high salinity film concentrations of 3.5 wt.% NaCl, the thin-film solution conductivity increases drastically, pushing the electrochemical corrosion current density (I_corr) from a baseline of 1.2 µA/cm² up to 49.6 µA/cm². Long-term mineralogical phase analysis confirms that continuous marine chloride exposure alters the rust scale evolution, forcing the preferential crystallization of loose, unstable akaganeite (β-FeOOH) tunnel crystals until it reaches a dominant 68% share within 12 weeks. Consequently, high surface salt accumulation up to 100 mg/m² results in a dramatic increase in cumulative steel weight loss to 295 g/m², triggering extensive scale delamination and blistering. These quantitative outcomes provide crucial empirical benchmarks for selecting high-durability protective barriers and calculating accurate structural corrosion allowances within high-salinity marine boundary layers.

Modelling and Simulation Investigation of Transient Heat Conduction in Composite Two-Material Rods

Akobuche Chikezie — 2026-09-11

This study investigated the modeling and simulation of transient heat conduction in composite two-material rods. Since many real-world systems are made of two or more materials with different thermal properties, transient heat conduction in composite materials is a significant issue in thermal engineering. These issues are very challenging to solve analytically and practically. The numerical solutions are therefore unavoidable. Transient heat conduction, in contrast to steady-state conduction, explains how a material’s temperature changes over time in response to changes in its initial or boundary thermal conditions. For the purpose of evaluating thermal stresses, material integrity, energy transfer, and the service performance of engineering systems, it is crucial to accurately predict this temperature evolution. The Crank–Nicolson method and a second-order finite-difference discretization in space were used to systematically formulate the problem. For a composite rod, the standard nondimensional transient conduction model is as follows: ∂Tₐ/∂t = ∂²Tₐ/∂x², 0 ≤ x ≤ 1/2 and ∂Tᵦ/∂t = ∂²Tᵦ/∂x², 1/2 ≤ x ≤ 1. The second material’s relatively high thermal conductivity helps it stay near the normalized temperature of unity. All the results illustrate the gradual transition from the initial non-equilibrium state to the steady thermal state and validate the anticipated physical behavior of transient conduction in a composite rod.