Iranian Journal of Materials Science and Engineering

A Mathematical Model for Upper-Bound Analysis of Backward Extrusion in Ultra-Thin-Walled Tube Forming

RAMIN Ebrahimi

This study presents an analytical model based on the upper-bound method to investigate the backward extrusion of ultra-thin-walled tubes (wall thickness 100–400 µm). The deformation zone is divided into distinct regions with kinematically admissible velocity fields and defined discontinuities, allowing accurate estimation of strain rate field. The model incorporates effects of friction, wall thickness variation, and velocity discontinuities to predict extrusion force, deformation zone depth, and strain localization. Validation through both experimental measurements and finite element simulations demonstrates strong agreement with the analytical predictions. The proposed model offers an efficient and reliable framework for understanding deformation mechanics in precision tube extrusion and serves as a practical design tool in metal forming processes.

Influence of Process Parameters and Metallic Binders on Physicomechanical and Tribological Properties of WC-based Alloys Fabricated by the SPS

Ali Rasooli

There is a global need to develop engineering materials to address the increasing demands in various industries. Spark plasma sintering (SPS) is one of the most distinguished powder metallurgy techniques, offering the opportunity for the fabrication of different types of materials. This work emphasizes optimizations of the important process parameters, including temperature, pressure, and holding time, involved in the SPS of the WC, WC-Co, and WC-Cr, as well as assessing the influence of the content of the Co (6-24 wt.%) and Cr (0.2-1 wt.%) binders on the overall characteristics of the SPS-ed cermets. The results illustrate that the process parameters highly affect the physicomechanical properties of the SPS-ed WC, where the most appropriate conditions from a physicomechanical viewpoint are obtained at a sintering temperature of 1700 °C, a pressure of 80 MPa, and a holding time of 5 min. The included Co binder reduces the optimum temperature and pressure down to 1200 °C and 70 MPa, respectively. The addition of the Co improves the final properties of the WC irrespective of its content. The highest tribomechanical properties are attained when 18 wt. % of Co is added. Similar to that of Co, the incorporation of Cr into the WC increases the tribomechanical performance. In general, the use of Co and Cr metallic binders seems a useful strategy to promote the overall properties of the SPS-ed WC.

The Effect of lanthanum Substitution on the Ferroelectric and Piezoelectric Properties of (Pb0.88Sr0.12)(Zr0.54Ti0.44Sb0.02)O3 Ceramics

Saeid Baghshahi

Piezoelectric ceramics based on lead zirconate titanate (PZT) with a composition of (Pb_0.88-3x/2Sr_0.12La_x)(Zr_0.54Ti_0.44Sb_0.02)O₃ where x=0.0, 0.005 and 0.01 were synthesized using conventional solid state sintering at 1280°C. The effect of lanthanum substitution on the microstructure, ferroelectric and piezoelectric properties of the samples was studied. The results showed that lanthanum substitution was beneficial for densification of the samples during sintering and the samples with 1.0 mole% lanthanum exhibited the maximum density of 7.34 g.cm^-3 when sintered at 1280°C. Moreover, the piezoelectric coefficient (d₃₃), relative dielectric constant (e_r), dielectric loss (tanδ), electromechanical coupling coefficient (k_p) and the Curie temperature (T_C) of the samples reached the optimal values of 635 pC/N, 3000, 0.018, 0.67 and 195°C respectively at 0.5 mole% lanthanum substitution. Furthermore, the bulk density (ρ) was 7.31 g.cm^-3 for the same sample. The results indicate that the lanthanum doped PSZTS ceramics can be hopefully used in applications such as pulsed transmitting transducers, high sensitivity receivers and actuators with large displacements.

Experimental Investigation of Single Shot Peening on TiN Coated surfaces

Ehsan Bazzaz

Improvement of the mechanical properties of the coated surfaces was the matter of significant researches for a long time. A lot of physical and chemical operations were applied and examined on the coating surfaces successfully, but the effect of the mechanical treatments was not widely investigated. In this paper, the effect of a surface mechanical treatment on the micro coating layer has been studied and investigated. For this purpose, the necessary conditions have been created for implying impact to the coating surface. A setup of gas gun facility with well-designed and prepared projectiles are used to strike the sample surface with different speeds. A significant number of impacts have been inflicted on the test sample of the spade drill insert cutting tool. The consequence of this process is the change in crystal structure of the coating layer, which shows that under the created conditions, the crystal structure was not destroyed and instead getting compacted so that the size of the crystal grains has been reduced and considerably refined. Subsequent studies using electron microscopy have led to the measurement of the average size of the crystalline grains before and after impacts. Obviously, a significant effect has been observed and a meaningful trend has been seen for this change in the form of a linear relationship. The main result is that about 4% reduction in the average grain size happens when the impact speed changes by 10m/s. In this way, the principal basis for the use of this surface treatment in improving the surface properties of the micro coating layers is provided. This leads to the application of such treatments as an industry process for improvement of thin coating mechanical properties.

Facile Synthesis and Optical Properties of Rod-like Copper Oxide Nanoparticles

Moges Tsega Yihunie

Copper oxide (CuO) nanoparticles (NPs) were synthesized by the sol-gel method, followed by calcination at 600 ^oC for 2 h. The XRD pattern indicated that the synthesized CuO NPs had a monoclinic structure, with an average crystallite size of 53 nm. The FT-IR spectra showed that surfactant molecules were adsorbed on the surface of the CuO nanoparticles, along with the presence of Cu-O bonding. The TEM analysis revealed rod-like CuO NPs with diameters of about 50 nm and lengths ranging from 150 to 200 nm. The XPS analysis confirmed that copper and oxygen were synthesized as the main components with Cu²⁺ and O^2-oxidation states. The optical band gap of CuO was calculated to be 3.5 eV. The maximum PL emission was recorded at 430 nm for the 365 nm excitation wavelength, and the change in PL intensity and peak shift was calculated as a function of excitation wavelength. The Mie analysis results also showed that when crystallite sizes increased, so did the maximum values of extinction efficiency, scattering efficiency, asymmetry, and scattering matrix. The findings of this study imply that CuO NPs could be a viable choice for a variety of luminous device applications.

Synthesis of Carbon black/geopolymer composites with high and stable electrothermal performance

Imad Disher

Geopolymer/nano carbon black composite is a promising electrically conductive smart material that can be used in self-heating and self-sensing applications. This paper studies the effect of adding nano carbon black to the physical, mechanical, electrical, and electrothermal performance of metakaolin-based geopolymer. Carbon black was added at the percent of 5%, 10%, 15%, and 20% by weight of metakaolin; the compressive strength was tested at various ages of 7, 14, 28, and 90 days, and the electrothermal performance was tested using AC and DC voltages. The results showed that a compromise between suitable compressive strength and high electrothermal conversion could be achieved when a specific balance between the carbon black percent and the lowest water content is established. A composite with a compressive strength of 27 MPa and stable electrothermal performance reaching 142°C at 9V DC can be prepared using 20 wt% of carbon black and a water-to-metakaolin ratio of 0.549, which is used as a smart material in construction applications.

Design and Development of Fe₃O₄/ZnTiO₃/MWCNT/Epoxy Nanocomposite: An Integrated Experimental and Numerical Investigation of Microwave Impedance Matching and Scattering Parameters

Reza Sarkhosh

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.