Nanosecond pulsed laser ablation of Al–Cu–Fe quasicrystalline material: Effects of solvent and fluence

Abstract

Nanosecond laser pulses were used to synthesize Cu/CuO/Fe3O4 and Al2O3 nanocomposites by ablating Al–Cu–Fe quasicrystal (QC) in two different solvents, namely ethanol and deionized water. The ablation was performed for 15 min with two different laser fluences of 40 J/cm2 and 80 J/cm2 in both the media. The effects of these solvents have been studied to understand the structural and morphological transformations of nanoparticles using microscopic and spectroscopic techniques. X-ray diffraction (XRD), selected area electron diffraction (SAED) and Raman spectroscopy studies revealed the formation of Cu/CuO/Fe3O4 and Al2O3 nanocomposites in both the solvents. Furthermore, transmission elctron microscopy/high resolution transmission electron microscopy (TEM/HRTEM) and field emission scanning electron microscopy (FESEM) in combination with the energy dispersive X-ray mapping established the formation of NPs with a typical core-void-shell structure evolved in presence of ethanol, showing the crystalline Cu–Fe phase in the core and amorphous Al2O3 phase in the shell. However, in the case of deionized water, the hollow structured NPs were obtained consisting of oxides of Cu, Fe and Al. The mechanisms of the formation of two structures in these two media are controlled by the Kirkendall diffusion process, which appears to be dependent on the physical properties of the solvent i.e., thermal conductivity, viscosity and, polarity. Based on the experimental observation, a possible mechanism for the observed morphology is discussed.