Effect of thermal annealing on the properties of nickel sulfide nanostructures: Structural phase transition

Abstract This work covers the effects of annealing temperature on crystalline size, surface morphology, optical, structural and paramagnetic properties of NiS and Ni 3 S 4 nanostructures grown through SILAR technique into FNBR matrix. Annealing at low temperature was performed in air and vacuum for 8 h. X-ray diffraction results confirm structural phase transitions (like NiS→Ni 7 S 6 and Ni 3 S 4 →Ni 9 S 8 ) and oxidation processes (by the formation of NiO-SO 4 -H 2 O) after thermal annealing of nanocomposites (NCs) in a vacuum and in air, respectively. By EDX spectrum the average Ni:S atomic ratio is approximately 1:1 for as-prepared NiS, 1:0.89 for NiS annealed in a vacuum and 1:0.91 for NiS annealed in air.