Pulsed laser ablation (PLA) is an effective method for processing and structuring materials at the micro- and nanoscale levels. Quasi-crystalline materials (QC) with unique physical and chemical properties are of particular interest for PLA studies. This work is devoted to studying the effect of solvent and laser flux density on the process of nanosecond PLA of quasi-crystalline material Al–Cu–Fe.
The experiments were carried out using a nanosecond Nd:YAG laser (λ = 1064 nm). The QC Al–Cu–Fe samples were placed in various solvents (water, ethanol, hexane). The laser radiation flux density was varied in the range from 1 to 5 J/cm². The obtained structures were analyzed using scanning electron microscopy (SEM) and atomic force microscopy (AFM).
To create Cu/CuO/FeO4 and Al2O3 nanocomposites, nanosecond laser pulses were applied to an Al–Cu–Fe quasicrystal (QC). The ablation process was carried out in two different liquids: ethanol and deionized water. Irradiation was carried out for 15 minutes at two levels of laser energy density: 40 J/cm2 and 80 J/cm2, in each of the media.
The effect of solvents was studied to understand the structural changes and morphology of nanoparticles using microscopic and spectroscopic techniques. X-ray diffraction (XRD), selected area electron diffraction (SAED) and Raman spectroscopy data indicate the formation of Cu/CuO/Fe3O4 and Al2O3 nanocomposites in both solvents.
Moreover, transmission electron microscopy (TEM/HRTEM) and field emission scanning electron microscopy (FE SEM) combined with energy dispersive X-ray mapping demonstrated that nanoparticles with a characteristic core-void-shell structure are formed in the ethanol medium, where the crystalline Cu–Fe phase forms the core and the amorphous Al2O3 phase forms the shell. In the case of using deionized water, hollow structured nanoparticles consisting of Cu, Fe and Al oxides were obtained.
The formation mechanisms of these two types of structures in different environments are determined by the Kirkendall diffusion process, which probably depends on the physical characteristics of the solvent, such as thermal conductivity, viscosity and polarity. A possible mechanism for the formation of the observed morphology is proposed based on the experimental results.
The results showed that the solvent has a significant effect on the surface morphology formed after ILA. In water, smoother and more uniform structures were observed compared to ethanol and hexane. This is due to the different thermophysical properties of the solvents, such as thermal conductivity and heat of evaporation.
Increasing the laser radiation flux density led to an increase in the ablation depth and the size of the resulting craters. At high flux densities, the formation of microdroplets of molten material was observed, which subsequently solidified on the sample surface. Optimization of the ILA parameters allows controlling the morphology and structure of the resulting nanostructures.
Author: R.Rawata, A. Tiwari, N. Arun, SVS Nageswara Rao, A.P. Pathak, Yagnesh Shadangi, N.K. Mukhopadhyay, S. Venugopal Rao, A. Tripathi
Institute: Department of Physics, School of Physical Sciences, Sikkim University 6th mile Samdur, 737102, Sikkim, India, School of Physics, University of Hyderabad, Hyderabad, 500046, Telangana, India, Center for Advanced Studies in Electronics Science and Technology (CASEST), University of Hyderabad, Hyderabad, 500046, Telangana, India, Department of Metallurgical Engineering, Indian Institute of Technology (BHU), Varanasi Varanasi, 221005, Uttar Pradesh, India, Advanced Center of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad, 500046, Telangana, India