This article presents a review of experimental investigations of changes in the structure and properties of the surface and near-surface layers of various materials (steels, metal alloys, ceramics, ...and graphite) in the area of a barcode applied by continuous laser radiation and short (nanosecond) and ultrashort (femto- and picosecond) laser pulses.
Nanostructured near-IR antireflective layer was produced on a GaAs slab surface by direct femtosecond laser fabrication of a surface diffraction grating. The single nanostructured layer on the GaAs ...slab reduces its total reflection at the wavelength λ ≈ 2.5 μm by 42 %, in agreement with the second-order approximation of the effective medium theory, with negligible increase of its absorbance.
•In a scanning regime, a symmetrical fs-laser beam yields in nanostructured microspikes.•Smooth and less oxidized microspikes were obtained using an asymmetrical fs-laser beam.•Surface topology and ...oxidation degree depends on scanning direction in the asymmetrical case
We have developed a new method for manipulating nanotopology and chemical composition of titanium surfaces by a scanning femtosecond laser beam with an asymmetrical spatial fluence distribution. Using of a common Gaussian laser beam leads to formation of combined nano- and micro-scale surface topologies owing to superimposition of different laser beam parts during the surface scanning. In contrast, beam shaping results in presumable surface structuring at specific laser fluences yielding in “clean” surface structures. In a simple case, cutting of a half beam perpendicular to the scanning direction enables to eliminate surface nanotopology, leaving less oxidized, cleaner and smoother microspikes, just by changing the scanning direction. Optimal experimental conditions were revealed to obtain in air the topologically and chemically different surface structures using the asymmetrical femtosecond laser beam and the opposite scanning directions.
The effect of the femtosecond laser irradiation on the formation of oxide layers on the surface of a commercially pure titanium VT1-0 was studied. The methods of X-ray analysis, scanning electron and ...transmission electron microscopies were used to study the structural and phase state of oxide layers. As a result of the femtosecond laser irradiation, the porous multi-phase nanocrystalline oxide coating with a thickness of 50 μm is formed on the titanium surface. The coating consists of titanium oxides: TiO2 (rutile and anatase), TiO and Ti3O5.
An analysis of the advantages of laser marking is carried out in comparison with other methods of forming a given surface relief of structural materials, forming barcodes, and reading them. The ...necessary conditions for stable reading of barcodes, described by the value of the contrast ratio, are formulated. The elements of the prints of the laser exposure pattern that make up the barcode are classified, and an example of measuring and calculating the contrast ratio of samples using spectrophotometry is given. The parameters of the surface relief in the areas of the applied barcode are measured using scanning probe microscopy. The analysis of the influence of the parameters of laser radiation on the geometric characteristics of the elements of the barcode and the value of its contrast ratio is carried out.
The phase and elemental composition of the near-surface layer of nitrided ferrovanadium irradiated with a high-power ion beam has been investigated by XRD and SEM methods. The impact of a powerful ...beam of the Temp-4M setup with an energy of carbon ions of 250 keV at a radiation pulse duration 10
–7
s and a power density of charged particles
q
i
≥ 10
6
W/cm
2
causes melting of the Fe–VN composite and partial evaporation of elements with a high vapor pressure from the surface layer. High-speed solidification of the melt on the surface of the Fe–VN target leads to the formation of highly dispersed vanadium nitride and tetragonal carbide Fe
23
C
6
in the modified layer. After irradiation of Fe–VN with a high-power beam with
q
i
≈ 10
7
W/cm
2
at a dose of ~ 10
15
cm
–2
, a violation of the translational invariance of the distribution of intercalated carbon atoms, a structural redistribution of Fe and V atoms, and the formation of X-ray amorphous microliquations of Fe–V and gas–carbon complexes are observed in the modified layer.
One-dimensional quasi-periodic nanogratings with spacings in the range from 160 to 600 nm are written on a dry or wet titanium surface exposed to linearly polarized femtosecond IR and UV laser pulses ...with different surface energy densities. The topological properties of the obtained surface nanostructures are studied by scanning electron microscopy. Despite the observation of many harmonics of the one-dimensional surface relief in its Fourier spectra, a weak decreasing dependence of the first-harmonic wavenumber (nanograting spacing) on the laser fluence is found. Studies of the instantaneous optical characteristics of the material during laser irradiation by measuring the reflection of laser pump pulses and their simulation based on the Drude model taking into account the dominant interband absorption allowed us to estimate the length of the excited surface electromagnetic (plasmon-polariton) wave for different excitation conditions. This wavelength is quantitatively consistent with the corresponding nanograting spacings of the first harmonic of the relief of the dry and wet titanium surfaces. It is shown that the dependence of the first-harmonic nanograting spacing on the laser fluence is determined by a change in the instantaneous optical characteristics of the material and the saturation of the interband absorption along with the increasing role of intraband transitions. Three new methods are proposed for writing separate subwave surface nanogratings or their sets by femtosecond laser pulses using the near-threshold nanostructuring, the forced adjustment of the optical characteristics of the material or selecting the spectral range of laser radiation, and also by selecting an adjacent dielectric.
The tungsten surface was processed by a high power pulsed ion beam at the TEMP accelerator (
ions, accelerating voltage of 200 ± 10 kV, energy density of a single pulse of 2.5–3.0 J/cm
2
). Changes ...in the relief and structure of the surface of tungsten samples were studied by scanning electron microscopy. After treatment with a high-power pulsed ion beam (HPIB), defects in the form of craters form on the surface of tungsten. The number of craters decreases with an increase in the number of impact pulses. After exposure to three pulses, microcraters are forms in the surface layer along the grain boundaries. After ten pulses, there are practically no cracks on the irradiated surface. An increase in the number of pulses leads to the formation of a more equiaxed ultrafine-grained structure in the near-surface layer of tungsten.
—The features of the method for generating gas-vapor plasma and the characteristics of a high-power ion beam (HPIB) obtained in a vacuum diode with a graphite cathode using a plasma-forming ...high-voltage nanosecond pulse are described. The cathode material and the two-pulse mode of operation of the TEMP-4 type diode make it possible to form a multicomponent nanosecond HPIB with a maximum ion energy of up to 1 MeV, a particle flux density on the surface of ~10
13
ion/cm
2
, and a power density on the sample surface of up to 10
7
W/cm
2
to modify the surface properties of structural materials. Materials are published within the framework of scientific discussion. The authors invite researchers of the generation of high-power beams of non-gas ions and the processes of beam modification of solid-state materials to discuss the topics of this article.
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