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Scanning electron microscopy (SEM) and profilometry of the crater morphology and ablation efficiency upon femtosecond laser ablation of Au-coated Ni targets in various fluids revealed a pronounced dependence on the ablation medium. For ethanol, a sufficient ablation efficiency was obtained, whereas for 2-butanol a higher efficiency indicated stronger laser–target interaction. Hierarchical features in the crater periphery pointed to asymmetrical energy deposition or a residual effect of the Coulomb-explosion-initiating ablation. Significant beam deviation in 2-butanol caused maximum multiple scattering at the crater bottom. The highest values of microstrain and increased grain size, obtained from Williamson–Hall plots, indicated the superposition of mechanical stress, defect formation and propagation of fatigue cracks in the crater circumference. For n-hexane, deposition of frozen droplets in the outer crater region suggested a femtosecond-laser-induced phase explosion. A maximum ablation depth occurred in water, likely due to its high cooling efficiency. Grazing incidence micro X-ray diffraction (GIXRD) of the used target showed residual carbon and partial surface oxidation. The produced nanoparticle colloids were examined by multiangle dynamic light scattering (DLS), employing larger scattering angles for higher sensitivity toward smaller nanoparticles. The smallest nanoparticles were obtained in 2-butanol and ethanol. In n-hexane, floating carbon flakes originated from femtosecond-laser-induced solvent decomposition. [ABSTRACT FROM AUTHOR]

This study aims to investigate the physical and chemical characterization of six fly ash samples obtained from different municipal solid waste incinerators (MSWIs), namely grate furnaces, rotary kiln, and fluidized bed reactor, to determine their potential for CO2 and thermochemical energy storage (TCES). Representative samples were characterized via simultaneous thermal analysis (STA) in different atmospheres, i.e., N2, air, H2O, CO2, and H2O/CO2, to identify fly ash samples that can meet the minimum requirements, i.e., charging, discharging, and cycling stability, for its consideration as TCES and CO2-storage materials and to determine their energy contents. Furthermore, other techniques, such as inductively coupled plasma optical emission spectroscopy, X-ray fluorescence (XRF) spectrometry, X-ray diffraction (XRD), scanning electron microscopy, leachability tests, specific surface area measurement based on the Brunauer–Emmett–Teller method, and particle-size distribution measurement, were performed. XRF analysis showed that calcium oxide is one of the main components in fly ash, which is a potentially suitable component for TCES systems. XRD results revealed information regarding the crystal structure and phases of various elements, including that of Ca. The STA measurements showed that the samples can store thermal heat with energy contents of 50–394 kJ/kg (charging step). For one fly ash sample obtained from a grate furnace, the release of the stored thermal heat under the selected experimental conditions (discharging step) was demonstrated. The cycling stability tests were conducted thrice, and they were successful for the selected sample. One fly ash sample could store CO2 with a storage capacity of 27 kg CO2/ton based on results obtained under the selected experimental conditions in STA. Samples from rotary kiln and fluidized bed were heated up to 1150 °C in an N2 atmosphere, resulting in complete melting of samples in crucibles; however, other samples obtained from grate furnaces formed compacted powders after undergoing the same thermal treatment in STA. Samples from different grate furnaces showed similarities in their chemical and physical characterization. The leachability test according to the standard (EN 12457-4 (2002)) using water in a ratio of 10 L/S and showed that the leachate of heavy metals is below the maximum permissible values for nonhazardous materials (except for Pb), excluding the fly ash sample obtained using fluidized bed technology. The leachate contents of Cd and Mn in the fly ash samples obtained from the rotary kiln were higher than those in other samples. Characterization performed herein helped in determining the suitable fly ash samples that can be considered as potential CO2-storage and TCES materials. [ABSTRACT FROM AUTHOR]