Iranian Journal of Materials Science and Engineering

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In this study, the crystallization behavior of a 65GeO₂-15PbO-10MgF₂-10MgO glass (prepared by the conventional melt quenching technique) has been investigated. The microstructure and crystallization behaviors of this glass were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), non-isothermal differential thermal analysis (DTA) and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that a fully glassy phase can successfully be prepared by the conventional melt quenching technique exhibiting one-stage crystallization on heating, i.e., the glassy phase transforms into crystalline MgGeO₃ and Pb₅GeO₇ phases. The activation energy for the crystallization, evaluated from the Kissinger equation, was approximately 202±5 kJ/mole using the peak temperature of the exothermic reaction. The Avrami exponent or reaction order, n, indicates the nucleation rate in this glass to increase with time and the crystallization to be governed by a three-dimensional interface-controlled growth.

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In the present study, the effects of boron on the structural and magnetic properties of AlCrFeNiMnSiB_x high entropy alloys (HEAs) were investigated. In this regards, different percentages of boron element were added to the based composition and the samples were identified using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Based on results, the tendency of Si element to formation of silicide phases prevents from the stabilization of single FCC and BCC solid solution phases in AlCrFeNiMnSi alloy. The boron element has significant effects on destabilization of silicide phases and by increasing in the percentage of this element, the simple BCC solid solution phase has been dominate phase. Of course, boron has distractive effects on magnetic properties of prepared alloys and the saturation of magnetization of AlCrFeNiMnSiB_x HEAs decrease from 29.8 emu/g to about 6 emu/g by increasing the boron content.  

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Investigation the structural and magnetic properties of nanocrystalline Co₇₈Zr₁₇B₂Si₁W₂ alloy during melt spinning and annealing processes were the main goal of this study. In this regard, samples were prepared using vacuum induction melting, melt spinning and subsequent annealing. The specimens were evaluated using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). Based on results, nanocrystalline Co₅Zr single phase with hard magnetic properties (Ms=29.5 emu/g and Hc=2.7 kOe) successfully formed during melt spinning process (at wheel speed of 40 m.s^-1). The coercivity value of rapid solidified sample increased to about 3.2 kOe during annealing process up to 400°C. However, more increasing in annealing temperature lead to the transformation of non-equilibrium magnetic Co₅Zr phase to stable Zr₂Co₁₁ phase, which has distractive effects on final magnetic properties.
 

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The present work, set out with the aim of studying the effect of in-situ precipitation of TiO₂ form Ti₃C₂T_x MXene phase on the electromagnetic (EM) behavior of Ti₃C₂/TiO₂ composites. In this regard, Ti₃C₂T_x MXene phase was synthesized using HF acidic etching of Ti₃AlC₂ MAX phase and the in-situ precipitation of TiO₂ phase within Ti₃C₂ sheets was followed by controlled annealing in temperature range of 500-800 ^oC for 2 h. The phase and structural characteristics of prepared composites were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM) and differential thermal analysis. The electromagnetic behavior of samples was also analyzed using vector network analyzer (VNA). The results showed that by performing the controlled annealing process of Ti₃C₂T_x MXene phase, it is possible to in-situ formation of TiO₂ phase and form the Ti₃C₂/TiO₂ composites. The electromagnetic behavior of Ti₃C₂/TiO₂ composites is in direct relation with the percentage of TiO₂ phase deposited within Ti₃C₂ sheets during annealing process. The reflection loss (RL) changed from -7.98 to -21.28 dB (within frequency range of 1-18 GHz) with increasing in annealing temperature from 500 to 800 ^oC as well as increasing the size and percentage of formed TiO₂ particles.
 

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The present study focuses on the phase and structural features of MnAl intermetallic compound during solid-state synthesis. In this regard, the milling process was done in differentMn_50+xAl_50-x (0<x<7.5)powder mixtures and the prepared samples were evaluated using X-ray diffractometer, scanning and transmission electron microscopy, differential thermal analysis and vibrating sample magnetometer. The results showed that the τ-MnAl magnetic phase with L1₀ structure could not be formed during the milling and low temperature annealing. During milling process, Al atoms dissolve in Mn network and a single β-Mn supersaturated solid solution (SSSS) form. The β-Mn (SSSS) phase is unstable and transforms into the icosahedral quasi-crystal as well as γ_2-Al₈Mn₅ and β-Mn stable phases during subsequent annealing.