M. Alipour, S. Mirjavadi, M. K. Besharati Givi, H. Razmi, M. Emamy, J. Rassizadehghani,
Volume 9, Issue 4 (December 2012)
Abstract
In this study the effect of Al–5Ti–1B grain refiner on the structural characteristics and wear properties of Al–12Zn–3Mg–2.5Cu alloy was investigated. The optimum amount for Ti containing grain refiners was selected as 2 wt.%. T6 heat treatment, (i.e. heating at 460 °C for 1 h before water quenching to room temperature and then aging at 120 °C for 24 h) was applied for all specimens before wear testing. Dry sliding wear resistant of the alloy was performed under normal atmospheric conditions. The experimental results showed that the T6 heat treatment considerably improved the resistance of Al–12Zn–3Mg–2.5Cu alloy to dry sliding wear.
Mohammad Khakbaz, Reza Sarkhosh, Masoud Javadi,
Volume 21, Issue 0 (IN PRESS 2024)
Abstract
Today, the application of high‑performance thin‑film nanocomposites as impedance‑matching layers in telecommunication and military technologies has gained substantial importance. In this study, a multiphase nanocomposite comprising Fe₃O₄, ZnTiO₃, and multi‑walled carbon nanotubes (MWCNT) embedded within an epoxy resin matrix was designed and synthesized under carefully controlled laboratory conditions. Experimental data were analyzed using multiple regression analysis alongside error variance reduction techniques to identify the optimal composition among the four finalized sample variants. During the fabrication process, the samples underwent sequential mixing, heating, and sonication steps to ensure proper dispersion of the fillers, followed by casting into molds with dimensions corresponding to the rectangular waveguide test section used for the electromagnetic measurements.Topological and morphological characterizations of the fabricated composites were performed by Scanning Electron Microscopy (SEM), while crystal structure assessments employed X‑ray Diffraction (XRD) analysis. Furthermore, electromagnetic characterization was conducted using WR‑90 waveguide measurements over the frequency range of 8.2–12.4 GHz. Among the samples examined, specimen C4, containing an increased ZnTiO₃ content, demonstrated superior particle dispersion and consequently improved electromagnetic impedance‑matching performance. Numerical simulations carried out with the Frequency Domain Solver of CST Microwave Studio corroborated the experimental findings with considerable agreement. The results identified Fe₃O₄ as the dominant contributor to magnetic loss mechanisms, whereas MWCNTs served as conductive constituents within the composite matrix. The inclusion of ZnTiO₃ markedly enhanced impedance matching characteristics, resulting in a significant reduction of wave reflection and thereby facilitating improved wave energy transmission control across a broad bandwidth. Specifically, for the 1 mm thick C4 sample, the reflection coefficient was reduced to −17.85 dB, while the transmission parameter S₂₁ remained below −0.072 dB at 8.2 GHz, indicating excellent impedance matching and minimal reflective loss. Frequency‑dependent analysis further demonstrated a stable balance between dielectric and magnetic contributions, manifesting in consistent electromagnetic performance without substantial deviation across the measured spectrum. Accordingly, the investigated nanocomposite emerges as a promising candidate for lightweight, high‑performance absorber layers, impedance‑matching layers, and electromagnetic coatings in advanced telecommunication and defense applications.
