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The existence of interfacial carbides is a well-known phenomenon in Al/diamond composites, although quantitative analyses are not described so far. The control of the formation of interfacial carbides while processing Al(Si)/diamond composites is of vital interest as a degradation of thermophysical properties appears upon excessive formation. Analytical quantification was performed by GC-MS measurements of gaseous species released upon dissolving the matrix and interfacial reaction products in aqueous NaOH solutions and the CH 4 /N 2 ratio of the evolving reaction gases can be used for quantification. Although the formation of interfacial carbides is significantly suppressed by adding Si to Al, also a decline in composite thermal conductivity is observed in particular with increasing contact time between the liquid metal and the diamond particles during gas pressure infiltration. Furthermore, surface termination of diamond particles positively affects composite thermal conductivity as oxygenated diamond surfaces will result in an increase in composite thermal conductivity compared to hydrogenated ones. In order to understand the mechanisms responsible for all impacts on the thermal conductivity and thermal conductance behaviour, the metal/diamond interface was electrochemical etched and characterized by SEM. Selected specimens were also cut by an ultrashort pulsed laser system to characterize interfacial layers at the virgin cross section in the reactive system Al/diamond.

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We have studied the nanostructuring and colorizing of the copper surface by scanning with a femtosecond laser beam with a near-Gaussian beam profile. The experimental studies were conducted using a femtosecond laser comprising a Ti:Sapphire oscillator and a multi-pass amplifier with the maximum pulse energy of 0.7 mJ, pulse frequency of 1 kHz, and pulse duration <30 fs. It is shown that the use of a short-pulsed femtosecond laser leads to the formation of wavelength scale periodic surface structures and eventually increases the brightness of the color of the copper surface. It is revealed that via reciprocally scanning the copper surface by multiple ultrashort laser pulses with a weakly asymmetric spatial energy density distribution and an energy density below the material ablation threshold, it is possible to create a combined nanostructure composed of low-spatial-frequency laser-induced periodic surface structures coated with nanoscale roughness. It is shown that relatively minor changes in the nanostructures obtained by scanning the copper surface by multiple ultrashort laser pulses can lead to a significant change in the color during surface colorizing.Keywords: femtosecond laser beam, copper colorizing, nanostructure, forward and reverse scanning, energy density.Citation: Liedl G, Pospichal R, Murzin SP. Features of changes in the nanostructure and colorizing of copper during scanning with a femtosecond laser beam.

A colorization of copper surfaces after nanostructure modifications with ultrashort laser pulses was studied. Femtosecond laser has been used for experiments. A relative motion of the laser beam on the material was realized. Tracks on the material obtained in a multi-pulse mode with an energy density lower than the threshold ablation were studied using scanning electron microscopy and atomic force microscopy. By the surface treatment with a laser pulses duration smaller than 30 fs, almost-wavelength periodic structures were formed and finally the surface brightness was increased. It was demonstrated that small nanostructure modifications changed the surface colour significantly. Using backscattered and secondary electron modes of scanning electron microscopy images were obtained from four sample regions that showed different colours, such as dark purple-red, turquoise, yellow-orange and grey-green. It was found that one of the main reasons for the difference in colour of images is the oxidation degree.