Effect of fuel to oxidizer ratio on the structure, micro structure and EPR of combustion synthesized NiO nanoparticles.

In this work we describe the synthesis, micro structure (XRD, SEM) and EPR of NiO nanoparticles synthesized by urea-based combustion method using Ni nitrate as the source of Ni. We used fuel-to-oxidizer ratio (psi) as a control parameter to investigate how lattice parameter, particle size and EPR susceptibility vary with psi = 0.25 to 2. Earlier we have studied NiO as a substitutional solute in MgO. The average particle size of NiO was estimated from the full width half maximum (gaussian and lorentzian fits) of the X-ray diffraction peaks of powders using Sherrer's formula and Williamson-Hall plot. The particle size varies from 7 nm to 38 nm as psi is varied systematically. The surface areas were measured using BET method. FT-IR confirms the Ni-O crystalline bond formation. We also calculated porosity and strain in the NiO nanoparticles with varying psi. EPR spectra have yielded the susceptibility of the NiO nanoparticles. Band gap of NiO was determined by UV-visible absorption edge.