Structural and optical properties of Ni/NiO composites synthesized by eco-friendly self-propagation synthesis (SHS): Effects of NH4OH addition

Ni/NiO composites were obtained by self-propagation synthesis (SHS) in order to investigate their structural and optical properties, evaluating the effects of ammonium hydroxide in the combustion. All the obtained solids were analyzed by X-Ray Diffraction (XRD), Ultraviolet–Visible spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy (RT-Raman) and Photoluminescence Spectroscopy (PL). The Ni phase content in the composite was dependent on the amount of ammonium hydroxide. Variations in the NiO cell dimensions were related to their nanostructure and to the formation of defects within the NiO lattice. Sample microstrain was associated with optical properties. The band gap values are shifted to higher wavelengths (red shift). The PL spectra show a strong dependence on the microstrain and NiO lattice defects. The PL quantum yield was measured in order to compare the amounts of defects in Ni/NiO composites.