In this work, we have used a nanosecond pulsed fiber laser to modify the wettability characteristics of AISI 430 steel. For this, various surface morphologies were created on the samples by laser irradiation with different overlapping and intensity parameters. Immediately upon laser treatment, all the structured samples acquired either hydrophilic or superhydrophilic wetting angles. All the samples were also analyzed with XRD. Then, laser-treated samples were kept in ambient air and/or low-temperature annealing was applied to reach hydrophobic surface properties. Interestingly, these surfaces returned back practically to their initial wetting state by cleaning in an ultrasonic bath. The obtained results are analyzed based on the existing wettability models.

The paper investigates how the surface relief of an implant affects cell behavior. Currently, most implant manufacturers claim the key impact biocompatibility factor to be surface micro-roughness. We suppose that the interaction between cells and implants also depends on such relief peculiarities as continuous or discontinuous topography, subcellular distance between peaks and presence of porous oxide layer. We have developed the laser processing conditions that provide three different reliefs: «open grooves», «grid» and «close grooves». Along with the micro-roughness characteristics the reliefs differ with their deepness and period of grooves. The surface composition analysis results have shown a sandwich structure consisting of Ti → TiO → Ti 2 O 3 Nx → TiO 2 (anatase) → TiO 2 (rutile). The wettability study has demonstrated superhydrophilicity (CA is 0 • ) for all reliefs. The quantitative and qualitative analysis of hMSCs proliferation and osteogenic differentiation was performed for 20 days. In vitro study has revealed the topography affects the spatial orientation of cells. The shape and size of the cell nuclei vary with different topographies. We have found continuous «open grooves» structures with the subcellular to cellular period are beneficial for cells' life-sustaining activity. Discontinuous «grid» structures with individual slots might not provide cells with mobility with the least external mechanical effect compared to «open grooves».

A pulsed fiber laser with a wavelength of 1.06 µm was used to treat a commercial pure titanium surface in the air at intensities below the ablation threshold to provide oxide formation. Laser oxidation results are predicted by the chemical thermodynamic method and confirmed by experimental techniques (x-ray diffraction, energy dispersive x-ray spectroscopy). For the first time, the chemical thermodynamic method was used for determining the qualitative and quantitative phase-chemical composition of the compounds formed by a pulsed laser heating of commercial titanium in the air, and its applicability is proven. The simulation shows that multilayered composite film appears on a surface, the lower layers of which consist of Ti 2 O 3 and TiO oxides with the addition of titanium nitride; and the thin upper layer consists of transparent titanium dioxide. Also, the chemical composition of films remains unchanged within a temperature range of 881-2000 K.

The local crystallization during annealing at 600 °C in nanoscale diamond-like carbon coatings films grown by pulsed vacuum-arc deposition method was observed using modem techniques of high-resolution transmission electron microscopy. The crystallites formed by annealing have a face-centred cubic crystal structure and grow in the direction [011 ] as a normal to the film surface. The number and size of the crystallites depend on the initial values of the intrinsic stresses before annealing, which in turn depend on the conditions of film growth. The sizes of crystallites are 10 nm for films with initial compressive stresses of 3 GPa and 17 nm for films with initial compres sive stresses of 12 GPa. Areas of local crystallization arising during annealing have a structure dif ferent from the graphite. Additionally, the investigation results of the structure of nanoscale diamond-like carbon coatings films using Raman spectroscopy method are presented, which are consistent with the transmission electron microscopy research results.[http://dx.doi.Org/10.1063/l.4903803]The negative influence of high intrinsic compressive stresses in diamond-like carbon (DLC) films with a high con tent of sp3-phase, restraining their widespread application in micromechanics, is well known.1,2 However, many research ers use the intrinsic stresses purposefully to form carbon coatings with special properties. In particular, the investiga tion of multilayer carbon-based structures, with different contents of sp3 and sp2-phases, which are characterized by different values of electrical conductivity and the internal stresses, is described.3,4 In this case, the changing accelerat ing potential of the substrate is used. It allows to accelerate carbon ions and forms layers with different properties, which is necessary for the method of vacuum-arc deposition with the filtration of the plasma flow.5The structure and electrical properties of the tetrahedral amorphous carbon (ta-C) films with 70%-88% sp3 content were investigated by atomic force microscopy (AFM), trans mission electron microscopy (ТЕМ), and Raman spectros copy as a function of annealing temperature in the range of 25-1100 °C.6 ТЕМ investigation is confirmed that the clus ters appear not only at the surface of the films but also in the bulk. The growth and the partial orientation of the sp2-bonded nanoclusters in the size range of 1-3 nm are accom panied by a large reduction in the film intrinsic stress, which decreases sharply in the temperature range of 500-600 °C. Therefore, temperature of 600 °C was selected in the present work as the critical temperature at which significant changes in the structure and properties of carbon coatings are beginning.The pulsed vacuum-arc method7 for deposition of DLC films allows to exclude the using of the electrostatic ion acceleration by applying a negative potential to the substrate Author to whom correspondence should be addressed. Electronic mail: kolpakov@bsu. edu.ru and to reduce undesirable heating of the carbon film during the deposition, ...

a b s t r a c tThe literature contains many contradictory data about the most thermodynamically favorable structure of precipitates in a-Ti matrix of the hypoeutectoid Ti-Si alloys. In this work we applied our recently developed thermodynamic model to predict the structure of Ti-Si precipitates in a-Ti matrix of the TiSi alloy with total Si concentration of 0.7 wt.%. We considered all prominent Ti-Si phases such as Ti 3 Si; Ti 5 Si 3 ; Ti 5 Si 4 ; TiSi and two TiSi 2 phases and discovered that formation of the Ti 5 Si 3 phase is more favorable than that of the Ti 3 Si in contradiction with the known phase diagrams. Theoretical result was confirmed by experimental investigation of microstructure and phase composition of the model Ti-0.7Si alloy annealed at 873 K for 10 h. Indeed, the only observed phase has hexagonal Ti 5 Si 3 structure. To ensure the completeness of the results we calculated ab initio elastic constants for all considered Ti-Si phases.