Influence of Electrodeposition Parameters on Morphology and Polymer Inclusion into Polymer/Zn Composite Coatings

In this study different type of composite coatings was obtained by electrodeposition using zinc as matrix and polymeric particles as disperse phase in zinc sulphate electrolyte. The effects of some electrodeposition parameters on the thickness and morphology of obtained composite coatings were analysed by optical microscopy, Scanning Electron Microscopy (SEM) and Energy-Dispersive X-Ray Spectroscopy (EDX) methods. Polymeric particles inclusion into zinc matrix was correlated with imposed electrodeposition parameters. It was observed that the thickness of the coatings is influenced by electrodeposition parameters. From the morphology of the coatings, it could be concluded that pure zinc has a regular surface with hexagonal crystals, while the composite coatings have fine surface structure. Also, the electrodeposition parameters influence the inclusion of the dispersed phase into metallic matrix that will influence further the different properties of the composite materials.

Moiré, Euler and self-similarity – the lattice parameters of twisted hexagonal crystals

A real-space approach for the calculation of the moiré lattice parameters for superstructures formed by a set of rotated hexagonal 2D crystals such as graphene or transition-metal dichalcogenides is presented. Apparent moiré lattices continuously form for all rotation angles, and their lattice parameter to a good approximation follows a hyperbolical angle dependence. Moiré crystals, i.e. moiré lattices decorated with a basis, require more crucial assessment of the commensurabilities and lead to discrete solutions and a non-continuous angle dependence of the moiré-crystal lattice parameter. In particular, this lattice parameter critically depends on the rotation angle, and continuous variation of the angle can lead to apparently erratic changes of the lattice parameter. The solutions form a highly complex pattern, which reflects number-theoretical relations between formation parameters of the moiré crystal. The analysis also provides insight into the special case of a 30° rotation of the constituting lattices, for which a dodecagonal quasicrystalline structure forms.

Nanostructural crystallization of metals

Based on thermodynamic calculations, it is shown that metal crystallization is an equilibrium nanostructural process. At the beginning, trigonal or tetragonal structure-forming nanocrystals are formed from elementary nanocrystals. Then crystallization centers are formed from them. Further, tetragonal or hexagonal dendrites are formed from them and tetragonal or trigonal structure-forming nanocrystals. Their forms depend on the degree of branching of dendrites. The most branched of them (compact dendrites) are tetragonal or hexagonal crystals.

Crystallomorphological and physical properties of apatite from carbonatites

This paper presents the results of the study of x-ray luminescence of apatite from different genetic types of apatite species in order to study its geochemical characteristics and the possibility of using as a mineral indicator the conditions of ore formation and for search purposes. Apatite Ca2Ca3(F,Cl,OH)2[PO4]3 contains impurities Gd3+, Ce3+, Eu2+, Dy3+, Sm3+, Nd3+ as well as Mn2+ and others. Syngony is hexagonal. Crystals of prismatic habit; usually ending in dipyramide or basopinacoid. Sometimes forms tabular crystals. A hexagonal prism is often preserved. Color greenish, bluish-green; pinkish-purple, gray; often white, colorless or brown. Quite often translucent due to the presence of small internal cracks and inclusions; sometimes the inclusions are arranged oriented, preferably parallel to the main axis of the crystal. Brightly luminesces in cathode, x-ray and ultraviolet rays. The intensity and color of luminescence varies widely depending on the impurities. The presence of three crystal chemical positions in the structure of apatite – two cationic and one anionic makes it possible to be realized in the mineral by a wide heterovalent substitution. The distribution of isomorphic impurities between the crystal chemical positions will depend on the type of cation, its amount, as well as anionic substitutions in apatite. To determine the luminescence intensity values of the characteristic isomorphic impurities of apatite TR3+ (Gd3+, Ce3+, Eu2+, Dy3+, Sm3+, Nd3+) and Mn2+, the X-ray luminescence method was applied. Apatites of different genetic types of the Aldan, Baltic Shields, the Baikal region (Russia), the Sette-Daban Range, and the Maimech-Kotui Province (Yakutia) and the Ukrainian Shield were investigated. The obtained values of luminescence intensity of TR3+ and Mn2+ can be used to diagnose the genetic type of apatite species, the conditions of mineral formation, the type of their mineralization and for search purposes. On the basis of factor analysis, it can be concluded that the intensity of the luminescence centers of rare earth elements in the apatites of each complex depends on the relative age position of the mineral in the groups of successively formed rocks. Analysis of apatite carbonatites from different deposits showed minimal fluctuations in the ratios of radiation intensity of X-ray centers (Ce3+, Sm3+, Mn2+, Eu2+), which may indicate a close geochemical situation and, consequently, the only source of matter in the formation of carbonates. Analysis of apatite carbonatites from different fields showed minimal fluctuations in the radiation intensity ratios of the centers of X-ray luminescence (Ce3+, Sm3+, Mn2+, Eu2+), which, in my opinion, may indicate a close geochemical situation and, as a consequence, the substance or the result.

BIAS OF BASAL DISLOCATION LOOP IN ZIRCONIUM

An analytical expression for the elastic interaction energy of radiation point defects of the dipole type with the basal dislocation loop of the hcp metal is obtained using the Green's function method for hexagonal crystals in the Krener approach. It was used for numerical calculation of the bias for the basal dislocation loop of zirconium in a toroidal reservoir. The toroidal geometry of the reservoir allows one to perform the calculation for a loop of any size and without any correction of the elastic field in its region of influence. The dependencies of the loop bias on its radius and nature are obtained for various shapes of dipole defects.

Microstructural Investigation of Fluoroapatite Hydrothermally Converted from Hydroxyapatite Synthesized from Crocodile Eggshell

Fluoro/hydroxyapatite (FHAp) were prepared by hydrothermal at 150 °C for 24 hours with different of starting materials. The conversion of hydroxyapatite (HAp) and tricalcium phosphate to FHAp showed the rod-like shape with 200 nm. While, the morphology of FHAp from crocodile eggshell as CaCO3 form with different in phosphorus and fluoride source showed the unique structure evolution from rod-like hexagonal crystals, dumbbell to ball shape. Two distinctive morphology, first when using NaF as fluoride source with (NH4)2HPO4 precursor show the large cubic structure in high magnification it is tufted hexagonal crystal and it bundle like structure. As the pH value decreases in NH4F, it increases crystal size. For H3PO4 as phosphate precursor found that unique structure evolution from rod-like hexagonal crystals to dumbbell structure and then form the sphere assembly with a size of several micrometers.

Intrinsic Valley Polarization in 2D Magnetic MXenes: Surface Engineering Induced Spin-valley Coupling

Generating valley polarization for valleytronics applications requires breaking the inversion symmetry of two-dimensional (2D) hexagonal crystals. As such, 2D MXenes naturally lose their inversion symmetry upon surface functionalization, thereby opening...

Studies of Zinc and Zinc Oxide Nanofilms of Different Thickness Prepared by Magnetron Sputtering and Thermal Oxidation-=SUP=-*-=/SUP=-

Polycrystalline zinc films with the thickness of about 20, 40, 60, and 80 nm and mainly granular morphology comprising nearly spherical particles involving hexagonal crystals are obtained by magnetron sputtering on cover glass supports. Subsequently, the prepared layers were subjected to thermal oxidation in the air to obtain transparent zinc oxide layers. The synthesized films are studied by SEM and UV-vis spectroscopy. Based on the obtained spectra, optical properties of the layers are studied as a function of their thickness. The optical band gap Eg for the films with the thickness from 40 to 80 nm is estimated on the level about 3.28 eV similar to the reference value 3.3 eV for bulk zinc oxide, while for the thickness of 20 nm Eg slightly drops to about 3.24 eV. Keywords: zinc; zinc oxide; nanolayers; magnetron; oxidation; surface morphology; transparency; optical bandgap.