Interaction of Various Variants of the Nanostructured Surface of Titanium with MSCs Isolated from Adipose Tissue

Titanium has been successfully used in dental implantology for a long time. Due to the osseointegration process, titanium implants are able to withstand the chewing load. This article is devoted to the study of surface treatment methods of titanium alloys and the study of their interaction with mesenchymal stem cells (MSCs). The surface microrelief can influence MSC differentiation in different ways, which subsequently gives it osteogenic potential. The paper proposes modes of surface modification of titanium alloys on Grade 4 and Grade 1 by chemical and electrochemical (anodizing) etching. The possibility of modifying the surface of titanium alloys using the synthesis of graphene layers has been proposed in this paper for the first time. The osteogenic potential of a particular surface was assessed by the number of mesenchymal stem cells cultured on them under identical conditions.

The Mechanisms of Antibacterial Activity of Magnesium Alloys with Extreme Wettability

In this study, we applied the method of nanosecond laser treatment for the fabrication of superhydrophobic and superhydrophilic magnesium-based surfaces with hierarchical roughness when the surface microrelief is evenly decorated by MgO nanoparticles. The comparative to the bare sample behavior of such surfaces with extreme wettability in contact with dispersions of bacteria cells Pseudomonas aeruginosa and Klebsiella pneumoniae in phosphate buffered saline (PBS) was studied. To characterize the bactericidal activity of magnesium samples with different wettability immersed into a bacterial dispersion, we determined the time variation of the planktonic bacterial titer in the dispersion. To explore the anti-bacterial mechanisms of the magnesium substrates, a set of experimental studies on the evolution of the magnesium ion concentration in liquid, pH of the dispersion medium, surface morphology, composition, and wettability was performed. The obtained data made it possible to reveal two mechanisms that, in combination, play a key role in the bacterial decontamination of the liquid. These are the alkalization of the dispersion medium and the collection of bacterial cells by microrods growing on the surface as a result of the interaction of magnesium with the components of the buffer solution.

Comparison of advanced techniques for mechanical surface treatment of stainless steel parts

This work compares various mechanical surface treatment techniques applied to improve the properties of the AISI 304 austenitic stainless steel. Effects of laser shock peening (LSP), water jet cavitation peening (WjCP), water jet shot peening (WjSP), and ultrasonic impact treatment (UIT) on surface roughness, hardness, and residual stress were studied. The results demonstrate that as compared to the untreated specimen (Ra = 3.06 μm), all strain hardening methods demonstrate the decreased surface roughness parameters. The smallest Ra parameter of the wavy regular surface microrelief is formed after the ultrasonic treatment. The surface hardness (22.1 HRC5) was respectively increased by 30.7%, 38.4%, 69.6%, and 73.2% after the LSP, WjCP, WjSP, and UIT treatments. All peening techniques induced compressive residual stresses (ranged from –377 MPa to –693 MPa) in the near-surface layer. It is assumed that used treatments can increase wear/corrosion resistance and fatigue life in the studied steel.

ДОСЛІДЖЕННЯ ВПЛИВУ ПОКРИТТІВ І ТЕХНОЛОГІЧНИХ МЕТОДІВ ВИГОТОВЛЕННЯ НАПРЯМНИХ ЕЛЕМЕНТІВ НА ЇХ ЗНОСОСТІЙКІСТЬ

The matter of the experimental studies of the effect of coatings and technological methods of manufacturing guide elements of universal prefabricated readjustable tooling on their wear resistance are presented. The coatings investigated were made of VK15 carbide powder, which were applied by detonation spraying, and a titanium nitride-based coating produced by condensation with ion bombardment, as well as the surface hardening of guide elements by diamond burnishing for various steels: 20V, 12KhN3A, 40Kh, 38KhMYuA-B and others.During the process of diamond smoothing the roughness improves by 2 - 3 classes and the very nature of the roughness changes: a surface microrelief is created with rounded peaks and valleys instead of microroughness with sharp peaks and valleys, which are characteristic of surfaces after grinding. In this case the bearing surface of the samples increases essentially, and their running-in is accelerated. According to the results of tests under a load of 50, 75 and 100 kgf, a graph of the dependence of wear on the specific pressure was built and it was found that the wear of samples after burnishing decreases by 25 ... 40% compared to polished and at a load of 20 kgf/cm, respectively, is for steel 20 ... 2.7 and 1.9 μm, for steel 12XN3A – 2.3 and 1.6 μm, for steel 40X – 1.8 and 1.3 μm and for steel 38XMYUA – 1.4 and 0.8 μm.With increasing the load the wear of the ground specimens increases sharply, and for the flattened specimens this process is much slower. Based on the test results, graphs of the wear rate were plotted depending on the test duration, as well as for wear in relation to the number of cycles. According to the test results, it was found that steel 38KhMYuA has less wear, which is associated with its high hardness and insignificant tendency to metal seizure. Based on the research results, it was found that different methods of processing parts (previous) grinding and diamond burnishing have different wear. It has been found that diamond burnishing is a very effective surface hardening process.As a result of the tests carried out, it was found that the best performance in testing for wear resistance obtained for a column with TiN coating, the thickness of which does not exceed 0.1 μm, is 5 - 6 times less than the wear resistance of columns with a hard-alloy coating. For the system of directly changeable dies, a pair is recommended, which includes a guide column with a detonation coating VK15 and a holder (sleeve) with a CIB coating based on TiN, since these coatings showed high performance properties and had practically no wear.

Optimization of the parameters of a partially regular microrelief by vibration rolling method

Experience of operating machines shows that their quality depends on the nature of the contact of mating parts. The irregular nature of the surface microrelief, which is due to traditional treatment methods used, arises difficulties in solving three main problems of microgeometry optimization: reliable, theoretically substantiated normalization, technological support, accurate measurement and control. This determined the direction in solving the problem of increasing the accuracy and reliability of the surface quality normalization, that is the microrelief normalization. At present, there are a large number of technological methods for surface treatment aimed to form a regular microrelief on it. One of the most common and studied methods for the regular microrelief formation is the vibration rolling method based on thin plastic deformation of the surface metal layers and a complex relative displacement of the treated surface and the deforming element. Significant progress in the surface quality normalization was achieved after the introduction of GOST 24773-81, the standard for regular microreliefs. For example, the nomenclature of parameters and characteristics of partially regular microreliefs includes the relative area occupied by regular inhomogeneities FH. FH is a value expressed as a percentage of the area occupied by regular inhomogeneities to the area of the treated surface. If FH is determined for the 2A·Sk area within the boundaries of a microrelief element at different axial steps of regular inhomogeneities, the microgeometry of a partially regular microrelief can be described ambiguously. To avoid this, it is necessary to consider the multiplicity of the ratio of the amplitude A to the axial step So.

Synthesis, XRD analysis and electronic structure of InGaTe2 chain semiconductor

In this work, we developed a technology for growing a single crystal of a ternary compound, using the Atomic Force Microscope (AFM), we studied the surface microrelief in 2D and 3D modes, using X-ray diffraction (XRD) analysis, determined the parameters of the unit cell of this phase and revealed that it crystallizes in tetragonal symmetry with lattice parameters [Formula: see text] Å and [Formula: see text] Å, space group I4/mcm. Using the density functional method, using the ABINIT software package, using the Troiller–Martins pseudopotentials in the basis of plane waves, the band structure was calculated, the origin of the valence and conduction bands was determined. It was revealed that this phase is a direct-gap semiconductor with a bandgap of 0.56 eV. The parameters of the InGaTe2 unit cell were calculated by the pseudopotential and linearized attached plane wave (LAPW) methods, the theoretical and experimental values of the lattice parameters are in good agreement. Based on the band structure, the effective masses of electrons and holes are determined. It is shown that the tensors of the inverse effective mass for both extreme have a diagonal form.

A New Method for Modeling the Cyclic Structure of the Surface Microrelief of Titanium Alloy Ti6Al4V After Processing with Femtosecond Pulses

A method of computer modeling of a surface relief is proposed, and its efficiency and high accuracy are proven. The method is based on the mathematical model of surface microrelief, using titanium alloy Ti6Al4V subjected to processing with femtosecond pulses as an example. When modeling the examples of microrelief, changes in the shape of segments-cycles of the studied surface processes, which correspond to separate morphological formations, were taken into account. The proposed algorithms were realized in the form of a computer simulation program, which provides for a more accurate description of the geometry of the microrelief segments. It was proven that the new method significantly increases the efficiency of the analysis procedure and processing of signals that characterize self-organized relief formations.