Structural phase transformations in radiolytically synthesized Al–Cu bimetallic nanoparticles

Abstract

The structural changes of radiolytically prepared aluminium–copper (Al–Cu) bimetallic nanoparticles by adjusting the precursors’ mole ratio and gamma radiation dose were investigated by transmission electron microscopy, field emission scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), and X-band continuous wave electron paramagnetic resonance (EPR). The EPR spectrum was also analysed through the simulation of the powder-like EPR spectra. The results note that in prepared samples with higher Al contents, formation of core–shell structure is dominant, whereas in Cu-rich samples, the final structures are primarily in alloy and oxide forms. According to the analysis of data obtained from X-ray diffraction, FTIR, and EPR, we found that the unpaired electron of the Cu2+ ion in various phases play the main role in structural phase transformation of Al–Cu nanoparticles. Additionally, based on the information extracted from simulated EPR peaks of Cu–Cu, the diameter of the Cu core in core–shell structures was obtained. We showed that by increasing the gamma radiation dose from 80 to 120 kGy, the overall size of nanoparticles decreases from 9.47 to 3.75 nm, but the contribution of copper core increases from 11 to 22 % of overall particle size.