Aluminium (Al) samples were nitrided in 13.56 MHz radiofrequency (RF) discharge of 70:30 vol.% Ar:N2 mixture at substrate temperature of 400 °C and RF power of 300 W for different fill pressures and treatment times. The nitrided samples were then characterized for their structural and mechanical properties using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), and Vickers micro hardness testing. XRD peaks (110), (111) and (200) of aluminium nitride (AlN) and their downshift confirmed the nitride formation together with nitrogen diffusion. The metastable cubic phase (c-AlN) shows texture growth and re-orientation dependent on fill pressure and treatment time. SEM micrographs showed the surface morphology with micro-pores. EDS results showed that the nitrogen content was significantly increased with nitriding time, along with the removal of oxides. Vickers hardness of the Al surface was increased more than thrice for 30 hours nitriding.

A discharge of nitrogen - hydrogen mixture by 50 Hz pulsed dc in the presence of active screen cage is investigated by optical emission spectroscopy (OES). The aim is to identify the parameters (mixture ratio, filling pressure and current density) that may lead to high concentration of active species (N2, N2+ and N). The maximum concentration in this experiment is found with 40% H2 - 60% N2, at filling pressure of 3 mbar with current density of 5 mAcm-2. High carbon steel samples are nitrided for 1 - 4 hours at 500ºC and the treated samples are characterized by X - ray diffraction (XRD), Raman spectroscopy and Vicker's micro - hardness testing. The XRD spectra show different phases of nitrides (Fe2 - 3N, FeN, CrN) along with iron oxides. The Raman spectra confirm the formation of α - β (C3N4). The surface hardness is found to increase up to six times for 2 hour treatment.