• MOHAMMAD AZADI

      Articles written in Sadhana

    • Investigation of tribological and compressive behaviors of Al/SiO₂ nanocomposites after T6 heat treatment

      MAHBOOBEH AZADI SAEID REZANEZHAD MEHRDAD ZOLFAGHARI MOHAMMAD AZADI

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      The aim of this paper is to present experimental results of tribological and compression properties of aluminum nanocomposites after T6 heat treatment. This heat treatment contained three stages: solutionizing at 500°C for 5 h, quenching in water, and ageing 180°C for 9 h. The method of nanocomposite production was the stir casting process. The SiO₂ nanoparticles in 0.5 and 1% wt were added to the aluminum melt as the reinforcement agent. The microstructural evaluation was conducted by the optical microscopy (OM) and the field emission scanning electron microscopy (FESEM) methods. The results of the wear test revealed that the specific wear rate of specimens comprising SiO₂ nanoparticles was lower than that of specimens without nanoparticles. Thus, the formation of the holes, wear debris and cracks decreased obviously for nanocomposite surfaces during wear testing. Moreover, the wear rate reduced obviously for nanocomposites fabricated by thepre-heating process compared to others. It was noticeable that the ball-milling process was an effective method to decrease the friction coefficient value to 0.15 for nanocomposites. Such observations were due to higher hardness and lower micro-porosity content. The elastic modulus for various nanocomposites improved by 8–19% compared to the aluminum alloy. In addition, when the content of SiO₂nanoparticles increased from 0.5 to 1% wt, the ultimate compressive strength decreased about 11–13% due to the presence of more microporosities.

    • Low crosstalk four-channel photonic crystal demultiplexer

      MOHAMMAD AZADI MAHMOOD SEIFOURI SAEED OLYAEE

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      In the present paper, a four-channel optical demultiplexer (DMUX) based on two-dimensional photonic crystal has been presented. In this optical demultiplexer, filtering and wavelength separation were performed using point defects between the output and input waveguides. To design the optical demultiplexer, a 31 X 21 resonance filter with a lattice constant (Ʌ) of 0.54 lm and the radius of the dielectric rods of 0.2Ʌ was first designed, and then it was expanded to obtain a four-channel 31 X 41 demultiplexer. The output wave spectrum was measured for four channels in the range of 1541.5 nm to 1557.6 nm. The average quality factor of 2567, the average crosstalk of - 25 dB, and the transmission coefficient of higher than 97% were obtained.

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