Papers by Keyword: Amorphous Phase

Abstract: The article presents the results of studies on preparation of amorphous zirconium dioxide from zirconium nitrate by its hydrolysis in the presence of oxalic acid. It is determined that the balance of reagents taken for synthesis (1 ml 0,025 M ZrO(NO₃)₂ is 1.35 ml 4 M HOOC-COOH), and the optimum temperature of the received gel drying, which is 230 ̊С, is established, too. Morphology of the obtained ZrO₂ samples was explored. It has been found that the calcining temperature is independent of the size and shape forming irregular agglomerates, consisting of smaller spherical particles, whose diameter varies between 50 and 300 nm. The X-ray analysis of the sample is represented, which showed a low degree of crystallinity of the substance. IR spectroscopy data showed the presence of zirconium dioxide-characteristic peaks on the IR spectrum. The same spectrum reflects the presence of a large amount of sorbed water in the obtained sample, as well as peaks characteristic of the gas adsorbed by the sample from the environment.

Abstract: In this study, amorphous Fe₇₈Si₉B₁₃ alloy was successfully synthesized by mechanical alloying (MA) of pure elemental powders which were milled under an argon gas atmosphere. Effects of milling time on the phase transformation, microstructure and morphological evolution were studied by X-ray diffraction (XRD), laser diffraction (Granulometry), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that by increasing the milling time, the nanocrystalline and amorphous phase content increases and alloys with good properties are obtained at 100 h of milling.

Abstract: In this paper, the effects of annealing treatment on the microstructure, thermal property and magnetic properties of mechanical alloyed FeSiBAlNiC and FeSiBAlNiCe amorphous high entropy alloys has been systematically investigated using X-ray diffraction, differential scanning calorimetry, field emission scanning electron microscopy and alternation gradient magnetometry. The results showed that annealing at different temperature range induced the pronounced microstructural evolution from the amorphous phase to a mixture of amorphous phase and intermetallics but without any formation of solid solutions. In addition, the thermal stability and heat resistance were enhanced with increasing the annealing temperature. Similarly, annealing treatment also had significant effect on the particle morphology, making the particles evolve from near-round shape to plate-like shape. Furthermore, subsequent annealing of W6-Ce amorphous HEAs enhanced the saturation magnetization (Ms) remarkably (from 0.6 emu/g of 140 h as-milled W6-Ce to 20.17 emu/g). But for the Ms values of the 140 h as-milled amorphous W6-C HEAs, annealing in different temperature range all exhibited a slightly decreased effect.

Abstract: Ni-W alloys were prepared by electrodeposition at diverse processing conditions. The Ni-W alloys were studied by SEM, EDX and XRD analysis to determine composition and morphology of the surface in dependence on electrodeposition conditions. Focus was put on surface with electroactive sites for hydrogen evolution. Stability of the alloys in chloride medium was determined applying chronopotentiometry and potentiodynamic polarization. Electrochemical behavior of the alloys was tested in alkaline solution by cyclic voltammetry. It was found that processing conditions directly influence quality of the Ni-W alloys concerning phase, morphology and composition. Prevailing amorphous phase of Ni-W alloys supports corrosion rate growth.

Abstract: The paper presents results of the Rietveld refinement method in X-ray diffraction quantitative phase analysis of calcium mono-aluminate, the mineral. It has been stated that the theoretical calcium mono-aluminate CaO⋅Al₂O₃. is a high-stable phase, mixing energy of which is equal to 16214,10 eV. Ab-initio calculations and Rietveld refinement method were used to identify die structural state of CaO⋅Al₂O₃.

Abstract: The Ti-48at%Al composite powder was synthesized by high energy ball milling. The properties of the composite particles, such as medium diameter,Phase ,microstructure and components, were respectively investigated . Results show that, the phase evolution process can be described by: Ti+ Al fcc Ti (Al),TiAl,TiAl₃,Ti₃AlTiAl₃,Ti₃Alamorphous phase. After milling 3 hours, Fcc Ti (Al) solid solution, TiAl, TiAl₃, Ti₃Al were found. After milling 9 hours, the amorphous phase of Ti - 48 at % Al were produced. The element distribution of the mechanically alloyed Ti-48at%Al powder was close to the initial design composition after 5 h milling, but this distribution was inhomogeneous. Medium diameter (D₅₀) of Ti-48at%Al composite powder achieved the minimal size 9.56 μm after milling for 5hours.

Abstract: Powder of Fe₇₂Nb₄Si₁₀B₁₄ (%at) glassy alloy was obtained by gas atomization in order to investigate the possibilities of amorphous phase formation due to the high cooling rates (10³ 10⁵ K/s) involved in this process. The ratio between the gas volumetric and the metal mass flow rates used was 1.0, and nitrogen (N₂) was used as the atomization gas. The powder, sieved in different granulometric size ranges, was characterized through: X-ray diffratometry (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). Fe₇₂Nb₄Si₁₀B₁₄ (%at) bulk metallic glass (BMG) showed completely or partially glassy structure depending on the size range. The obtaining of powders with glassy structure that could be applied as shot penning powder particles and thermal spray feeding powder for metallic coatings or would make possible the production of bulk glassy materials by warm consolidation of such powders or even a millimeters thick deposit obtained by spray forming with glassy or metastable microstructure that would be very interesting considering applications as soft ferromagnetic parts.

Abstract: Nanostructured WC-17Co coating was prepared by means of High Velocity Oxygen Flame (HVOF) technique. Characteristic of nano-structure of the coating was analyzed. The coating seems to be of lamination structure formed by fully or partially melted powder. It shows that the coating consists of melted and recrystallized zone, semi-molten zone and un-melted zone. Amorphous phase and nanocrystalline phase co-existed in the coating is due to the rapid heating and cooling during spraying. The nanostructured coating possesses excellent mechanical properties, which are closely related to the unique nanostructures existed in the coating.

Abstract: Ti/(Ru,Ir)O_x, and Ti/(Ru,Ir,La)O_x oxide electrodes were prepared by using thermal decomposition of the metal chlorides in the precursor solution on the Ti base. Their apparent electrocatalytic activity investigated by cyclic voltammetry, polarization curve, scanning electron microscope and X-ray diffraction. These data show that Ti/(Ru,Ir,La)Ox oxide electrode exhibits considerably high voltammetric charges, apparent current density and low onset potential for the ClER and OER. The XRD results reveal the main formation of the La-containing oxide electrode in amorphous phase.

Abstract: In the current study, the amorphization behavior of mechanically alloyed Ni57Zr20Ti22Ge1 powder was examined in details. The conventional X-ray diffraction results confirm that the fully amorphous powders formed after 5 hours of milling. The thermal stability of the Ni57Zr20Ti22Ge1 amorphous powders was investigated by differential scanning calorimeter (DSC). As the results demonstrated, the glass transition temperature (Tg) and the crystallization temperature (Tx) are 761 K and 839 K, respectively. The supercooled liquid region ΔT is 78 K. The appearance of wide supercooled liquid region may be mainly due to the Ge additions which cause the increasing differences in atomic size of mechanically alloyed Ni57Zr20Ti22Ge1 powders.