148 research outputs found
Formation of the oxide coating on the titanium surface by multipulse femtosecond laser irradiation
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 surfac
The formation of oxide layers on a titanium surface by irradiation with femtosecond laser pulses
By subjecting technical grade titanium to irradiation with femtosecond laser pulses with highenergy density, we create a microporous nanocrystalline oxide layer with a thickness of ∼50 μm on its surface. The structure and phase composition of the modified surface layers are studied using X-ray diffraction and high-resolution scanning and transmission electron microscopie
Topological Coherent Modes for Nonlinear Schr\"odinger Equation
Nonlinear Schr\"odinger equation, complemented by a confining potential,
possesses a discrete set of stationary solutions. These are called coherent
modes, since the nonlinear Schr\"odinger equation describes coherent states.
Such modes are also named topological because the solutions corresponding to
different spectral levels have principally different spatial dependences. The
theory of resonant excitation of these topological coherent modes is presented.
The method of multiscale averaging is employed in deriving the evolution
equations for resonant guiding centers. A rigorous qualitative analysis for
these nonlinear differential equations is given. Temporal behaviour of
fractional populations is illustrated by numerical solutions.Comment: 14 pages, Latex, no figure
Paleointensity determination on Neoarchaean dikes within the Vodlozerskii terrane of the Karelian craton
© 2017, Pleiades Publishing, Ltd. The results of paleomagnetic studies and paleointensity determinations from two Neoarchaean Shala dikes with an age of ~2504 Ma, located within the Vodlozerskii terrane of the Karelian craton, are presented. The characteristic components of primary magnetization with shallow inclinations I = −5.7 and 1.9 are revealed; the reliability of the determinations is supported by two contact tests. High paleointensity values are obtained by the Thellier–Coe and Wilson techniques. The calculated values of the virtual dipole moment (11.5 and 13.8) × 10 22 A m 2 are noticeably higher than the present value of 7.8 × 10 22 A m 2 . Our results, in combination with the previous data presented in the world database, support the hypothesized existence of a period of high paleointensity in the Late Archaean–Early Proterozoic
Surface texturing of steel by femtosecond laser and accompanying structure/ phase transformations
Topography, structure, and phase composition of surface layers of AISI 321 stainless steel textured by 1030-nm 320-fs-laser pulses were studied by scanning electron microscopy and X-ray diffraction analysis. Variation in single-pulse fluence and the number of pulses was found to change the laser-produced surface texture from onedimensional quasi-periodic nanograting to microrelief of various roughnes
Residual stresses in Ti6Al4V alloy after surface texturing by femtosecond laser pulses
Surface topography and residual stresses in surface layers of α + β titanium alloy
Ti6Al4V textured by 1030-nm, 320-fs-laser pulses were studied by scanning electron
microscopy and X-ray diffraction analysis. It was found that multipulse laser processing leads to the formation of laser-induced periodic surface structures (LIPSS) on the surface of Ti6Al4V alloy. XRD studies showed that depending on the laser pulse fluence, both tensile and compressive residual stresses are formed in thin near-surface layer
XPS and DFT study of pulsed Bi-implantation of bulk and thin-films of ZnO - the role of oxygen imperfections
An atomic and electronic structure of the bulk and thin-film morphologies of
ZnO were modified using pulsed Bi-ion implantation (1x1017 cm-2 fluence, 70 min
exposure under Bi-ion beam, EBi+ = 30 keV, pulsed ion-current density of not
more than 0.8 mA/cm2 with a repetition rate of 12.5 Hz). The final samples were
qualified by X-ray photoelectron core-level and valence band mapping
spectroscopy applying ASTM materials science standard. The spectroscopy data
obtained was discussed on the basis of DFT-models for Bi-embedding into ZnO
host-matrices. It was established that in the case of direct Bi-impurities
insertion into the employed ZnO-host for both studied morphologies neither the
only "pure" Bi2O3-like phase nor the only "pure" Bi-metal will be preferable to
appear as a secondary phase. An unfavorability of the large cluster
agglomeration of Bi-impurities in ZnO-hosts has been shown and an oxygen 2s
electronic states pleomorphizm was surely established.Comment: 20 pages, 8 figures, 2 tables, accepted to Appl. Surf. Sc
Optical transparency and local electronic structure of Yb-doped Y 2 O 3 ceramics with tetravalent additives
The results of optical transmission and X-ray core-level spectra measurements of Yb:Y 2 O 3 ceramics with different tetravalent sintering additives (ZrO 2 , CeO 2 and HfO 2 ) fabricated from nanopowders (produced by the laser ablation method) and then annealed at 1400 °C in air for 2 h are presented. It is found that the transmission values for ZrO 2 - and HfO 2 -doped ceramics at the lasing wavelengths are higher than those of CeO 2 -doped samples. The X-ray photoelectron spectra (XPS) O 1s spectra show that the relative intensity of oxygen defect peak detected for 3Yb:Y 2 O 3 + 5CeO 2 ceramics decreases substantially and consistently compared to that of 5Yb:Y 2 O 3 + 5HfO 2 and 3Yb:Y 2 O 3 + 5ZrO 2 samples. This can be attributed to a more complete filling of oxygen vacancies due to annealing-induced oxygen diffusion into the highly defective sintered ceramics. The measurements of XPS Ce 3d spectra showed that the insufficiently complete filling of the oxygen vacancies in the 3Yb:Y 2 O 3 + 5CeO 2 compound is due to the appreciable presence of trivalent cerium ions. © 2019 by the authors.Ministry of Education and Science of the Russian Federation, Minobrnauka: 3.7270.2017/8.9This study was supported by FASO (Theme "Electron" No. AAAA-A18-118020190098-5). The XPS measurements were supported by the Ministry of Education and Science of the Russian Federation (Project No. 3.7270.2017/8.9) and the Government of the Russian Federation (Act 211, agreement No. 02.A03.21.0006). Fabrication of ceramic samples was performed in the framework of the state task of IEP UB RAS
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