Synthesis of γ-Alumina Nanoparticles by Wire-Explosion Process: Characterisation and Formation Mechanism

Single-step synthesis of gamma-alumina (gamma-Al2O3), by wire-explosion process (WEP), is described in this work. Molecular oxygen is used as ambient gas with different levels of pressure to obtain the corresponding oxide nanoparticles (NPs). The energy (E) deposited to the capacitor, used for the explosion is in multiples of the sublimation energy. XRD and TEM techniques are used to characterise the synthesized nanoparticles. The content of gamma-Al2O3 increases with increase in E and/or oxygen pressure (P). The average particle size of the nanoparticles reduces with the increase in E and/or decrease in P. The Born-Haber cycle is used to calculate the lattice energy (LE) of the bulk Al2O3. The dependence of LE and the formation enthalpy of alumina nanoparticles with size are evaluated. A classical homogenous nucleation theory is used to see the effect of saturation ratio and temperature on the activation energy and the nucleation rate of the NPs correlating it with size dependence on E and P used in the WEP.