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It has been reported that ball milling and adding catalyst can improve hydrogen desorption properties of MgH 2. In this study, simultaneous effect of adding catalyst and ball milling on hydrogen desorption properties of MgH 2 was studied. Mechanical alloying and heat treatment methods were used to synthesize MgNi 4 Y intermetallic as a catalyst. In this regard, pure Mg, Ni, and Y elemental powders were ball milled in different conditions and then heat treated at 1073 K (800°C) for 4 hours. XRD and FESEM methods were used to investigate properties of the samples. It was found that, after 10 hours of ball milling and then heat treating at 1073 K (800°C), MgNi 4 Y intermetallic was formed almost completely. The results of Sievert tests showed that as-received MgH 2 did not release any significant amount of hydrogen at 623 K (350°C). But, after ball milling for 10 hours, 0.8 wt pct hydrogen was released from MgH 2 at 623 K (350°C) in 40 minutes. Adding 10 wt pct catalyst via ball milling to MgH 2 led to releasing 3.5 wt pct hydrogen in the same conditions. In addition, increasing ball milling time from 10 to 65 hours increased the amount of released hydrogen from 51 to 85 pct of theoretical hydrogen desorption value and improved kinetic of desorption process.

In this research, plasma electrolytic saturation of carbon and nitrogen was used to prepare TiC/N coating on NiTi alloy. In this regard, four types of urea-based electrolytes with various amounts of NH 4 NO 3 were employed. The effect of electrolyte composition on the characteristics of the formed layer was studied using grazing incidence X-ray diffraction and scanning electron microscopy. The results showed that the TiC 0.2 N 0.8 compound was formed in coating. The pore size of coating was increased by increasing the concentration of NH 4 NO 3 . To investigate the corrosion resistance of the coated samples, the potentiodynamic polarization test and electrochemical impedance spectroscopy were performed in Ringer's solution. It was observed that as the NH 4 NO 3 concentration of electrolyte increased, the corrosion resistance of the formed layer was reduced. Such a behaviour was attributed to the operating current as well as discharge energy enhancement which caused the deep cracks and porosities formation in the coating.