Se adsorption on Fe(100) and (111) surfaces is examined using the density functional theory (DFT). Selenium is adsorbed in a distorted bridge on the (111) surface while in the (100) surface it prefers a 4-fold hollow site, with energies of -10.36 and -5.25 eV, respectively. Se adsorption results in surface reconstruction. There is some contraction in the case of the (1 0 0) plane for 1/4 and 1/2 ML coverage and some relaxation at 1 ML (4.5%). Contraction increases to 15% for the (1 1 1) plane at 1/4 ML. At a higher coverage, there is a non-regular movement of surface metal atoms, and there is almost no change at 1 ML. The magnetic moment for surface Fe atoms decreases with coverage. The most important changes are in the (1 0 0) plane, followed by the (1 1 0) and then the (1 1 1) planes with a reduction of 52%, 24% and 7% respectively. The density of states presents a contribution of Se states at -5.0 and -13.1 eV, when stabilized after adsorption. The Fe-Fe bond weakening is higher in the (1 0 0) plane. Fe-Se bonds are formed at the expense of the metallic bond.
COBISS.SI-ID: 1062826
The Auger electron spectroscopy study on chemistry of the 46.8°(111) twist grain boundary of an Fe-2.3%V alloy showed an extended phosphorus enrichment at temperatures in range of 500°C and 800°C. Simultaneously, slight but nearly independent segregation of vanadium was also detected. The standard enthalpy and entropy of grain boundary segregation of phosphorus and vanadium were determined according to the Guttmann model of multicomponent interfacial segregation. Obtained data clearly show that this [sum] = 19 coincidence boundary is special (i.e. low energy interface). The data also fit well with the predictive model of grain boundary segregation and confirm that phosphorus segregates intersitially at the grain boundary while vanadium substitutes iron atoms in the interface structure.
COBISS.SI-ID: 899498
The adsorption of atomic Se on a Fe(1 1 0) surface is examined using the density functional theory (DFT). Selenium is adsorbed in high-symmetry adsorption sites: the -short and long-bridge, and atop sites at 1/2, 1/4, and 1 monolayer (ML) coverages. The long bridge (LB) site is found to be the most stable, followed by the short bridge (SB) and top sites (T). The following overlayer structures were examined, p(2 * 2), c(2 * 2), and p(1 * 1), which correspond to 1/4 ML, 1/2 ML, and 1 ML respectively. Adsorption energy is -5.23 eV at 1/4 ML. Se adsorption results in surface reconstruction, being more extensive for adsorption in the long bridge site at 1/2 ML, with verticaldisplacements between +8.63 and -6.69% -with regard to the original Feposition-, affecting the 1st and 2nd neighbours. The largest displacement inx or y-directions was determined to be 0.011, 0.030, and 0.021 A for atop and bridge sites. Comparisons between Se-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the Se. At the long bridge site, the presence of Se causes a decrease in the surface Fe d-orbital density of states between 4 and 5 eV below Fermi level. The density of states present a contribution of Se states at -3.1 eV and -12.9 eV.
COBISS.SI-ID: 854186
In this research, the structure changes along the depth of gradient layers of titanium substrate, after etching with NaOH and subsequent thermal treatment at various temperatures between 300 and 800 °C, were investigated by XRD, FTIR and AES. Particularly, the changes of Ti substrate after etching with NaOH, subsequent ionic exchange of Na+ with Ca2+ ions and thermal treatment at 700 °C were analysed This structure might be suitable for deposition of hydroxyapatite by biomimetic or plasma methods and as an appropriate scaffold for cell adhesion and proliferation.
COBISS.SI-ID: 17537814
The scientific monography covers the characterization and modeling of polycrystalline metallic material (spring steel) microstructures, with the aim being to better understand the complex problem of predicting material properties based on a knowledge and representation of the microstructure. The microstructure features of the spring steel were studied on numerous samples in order to understand the basic geometrical characteristics needed to build the model. An overview of light microscopy, scanning electron microscopy, and Auger electron spectroscopy techniques is provided. Some general aspects of the methods used for the microstructure modeling are provided. The method using neural networks and genetic algorithms is an original breakthrough contribution and provides the foundation for a completely new approach to the modeling of metallic materials. The representation of a random grain structure (as an object) is realized using the neural networks. The manipulation and optimization of the randomly generated grain shape is achieved by the genetic algorithms. The established concept of the 2D modeling is designed and can be directly used in the 3D space.
COBISS.SI-ID: 1024170