M. Maleki, S. M. Rozati,
Volume 12, Issue 4 (December 2015)
Abstract
In this paper, polycrystalline pure zinc oxide nano structured thin films were deposited on two kinds of single crystal and polycrystalline of p and n type Si in three different substrate temperatures of 300, 400 and 500◦C by low cost APCVD method. Structural, electrical and optical properties of these thin films were characterized by X ray diffraction, two point probe method and UV visible spectrophotometer respectively. IV measurements of these heterojunctions showed that turn on voltage and series resistance will increase with increasing substrate temperature in polycrystalline Si, while in single crystal Si, turn on voltage will decrease. Although they are acceptable diodes, their efficiency as a heterojunction solar cell are so low
E. Maleki, K. Reza Kashyzadeh,
Volume 14, Issue 4 (December 2017)
Abstract
Hardened nickel coating is widely used in many industrial applications and manufacturing processes because of its benefits in improving the corrosion fatigue life. It is clear that increasing the coating thickness provides good protection against corrosion. However, it reduces the fatigue life. Thus, applying a thin layer of coated nickel might give an acceptable corrosion protection with minimum loss of the fatigue life. In the present study, the effects of hardened nickel coating with different thicknesses on the fatigue behavior of CK45 mild steel were experimentally investigated. After conducting the experimental tests, we carried out two different modeling approaches of finite element method (FEM) and artificial neural network (ANN). In the FEM modeling, an attempt was made to analyze the fatigue of the components by modeling the interface phase between the base metal and coating more accurately and using the spring elements; ANNs were developed based on the back propagation (BP) error algorithm. The comparison of the obtained results from FEM and ANN modeling with the experimental values indicates that both of the modeling approaches were tuned finely.
B. Mirzakhani, Y. Payandeh, H. Talebi, M. Maleki,
Volume 17, Issue 3 (September 2020)
Abstract
In this paper, the effect of two-step precipitation hardening on the mechanical properties of Al-3.7Cu-1Mg was investigated. For this meaning, some specimens were subjected to the first step aging at 175, 190 and 205°C for 2 h, once the samples solution treated at 500°C. To have stable precipitates uniformly distributed in the microstructure and to reduce the heat treatment time, the second step was implied at 65°C. The tensile and hardness tests were performed at ambient temperature immediately after aging. The results indicated that depending on the first step temperature, the second aging time affects the alloy mechanical behavior in different aspects. A factor named SNMP introduced to determine the cycle giving the best mechanical properties. The strength and elongation increase 1.5 and 2 times respectively; compared to the values reported in the DIN EN 755-2 standard by performing the two-step aging cycle, consisting of the first-stage at 175°C and the second step at 65°C for 10 hours. Moreover, using the proposed two-step aging, the heat treatment time was reduced considerably compared to the conventional precipitation hardening process.
Aliyeh Afzalalghom, Ali Beitollahi, Seyed Mohammad Mirkazemi, Mahdi Maleki, Hossein Sarpoolaky,
Volume 23, Issue 2 (June 2026 2026)
Abstract
Gas-phase methods for graphite/graphene production, such as chemical vapor deposition (CVD), yield high-quality products but demand catalysts, substrates, high-purity hydrocarbon gases, specialized furnaces, and temperatures exceeding 1000 °C. Here, we demonstrate the synthesis of highly graphitized films with crystalline domains via low-temperature carbonization (900 °C) of nanoporous polydivinylbenzene (PDVB) microspheres, without reliance on a CVD system or catalysts. The films formed on the inner surface of the furnace quartz tube and were characterized by Raman spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). Raman spectrum revealed a high graphitization degree (ID1/IG = 0.78), surpassing reported values for catalyst-free plasma- or low-pressure-assisted CVD. XRD showed a sharp diffraction peak at 2θ = 26.37° (d = 3.37 Å), exactly matching the (002) plane of Graphite-2H, while HRTEM and selected area electron diffraction confirmed crystalline domains with p63/mmc symmetry. We propose that the intricate network of nanopores as nanoreactors in PDVB microspheres enables the generation and controlled release of fused benzene rings into the quartz tube, where they condense to form crystalline films. This approach reveals how a nanoscale confinement can be translated into a macroscopic, scalable route, offering a low-cost and facile method for graphite or graphene production.
