X-ray Amorphous Structure Research Articles

Механічні властивості аморфних металевих сплавів системи Al87(Ni,Fe)8(REM)5 після короткочасного відпалу

The phase transition temperatures for amorphous metals based on aluminum Al87(Ni,Fe)8(REM)5 system were determined by differential scanning calorimetry (DSC). The mechanisms of formation and growth of nanocrystals in an amorphous matrix were predicted using kinetic models (Matusita model). It was found that after annealing at the temperature of stable nanocrystalline growth, an X-ray amorphous structure with a volume fraction of disordered nanocrystalline phases of solid state of Al(X), GdFe2, AlFe2Ni, GdFe2 for the amorphous metal alloy (AMA) Al87Y4Gd1Ni4Fe4 alloy and microcrystalline phases of solid state of Al(X), GdFe2 AlFe2Ni for the Al87Gd5Ni4Fe4 alloy are formed, which significantly affects the mechanical properties of the Al87(Ni,Fe)8(REM)5 system. The effect of annealing on the mechanical properties of amorphous aluminum-based alloys was investigated using Oliver-Pharr and Young's modulus methods it was found that thermal modification of AMAs: Al87Gd5Ni4Fe4 as a result of heat treatment of AMAs from 5 to 15 min., the microhardness increases from 0.20 GPa to 2.75 GPa, and when heat treated for 60 min at a temperatures of T3 = 645±5 K, 647±5 K, it decreases to 0.35 GPa and 0.45 GPa, respectively.

Synthesis, Characterization and Evaluation of the Application of CoZn Nanostructures as Anode Materials

This study aims to obtain CoZn nanostructures using the electrochemical deposition method and to estimate the applicability of the resulting nanostructures as anode materials for lithium-ion batteries. Scanning electron microscopy, energy dispersive and X-ray phase analysis were used as the main methods for characterizing the obtained nanostructures. A study of the morphological properties of the synthesized nanostructures revealed that the variation of the synthesis conditions results in the formation of structures with different degrees of structural ordering and morphology. During the evaluation of the phase composition of the synthesized CoZn nanostructures with variation in the applied potential differences, the phase transformations’ dynamics were established, which can be written as follows: X-ray amorphous structures → Zn/CoO2 → Co2Zn11/Co/CoO2 → Co2Zn11/ZnO. Using the methods of phase analysis and mapping, an isotropic distribution of phases in the composition of nanostructures was established. In such a case, the formation of the Co2Zn11 phase occurs with an elevation in the concentration of cobalt from 8.9 to 29.3–31.1 at. % leads to the partial substitution of zinc ions by cobalt ions, followed by the formation of a cubic phase. The study of the morphological properties of the synthesized CoZn nanostructures afterlife tests showed differences in the degradation processes of nanowires triggered by the phase composition alteration.

Understanding the structural phase state of bulk amorphous/crystalline alloys obtained from Zr35Ti30Be27,5Cu7,5 powder

The paper describes a method for obtaining Ti- and Zr-base near-eutectic alloys in the form of powders with a high degree of sphericity and a narrow size distribution of powder particles. Thus, a Zr35Ti30Be27,5Сu7,5 alloy powder with a particle sphericity of more than 97% and a particle size distribution of 63–100 μm was produced using the method of plasma spheroidization of fragmented powders obtained by grinding amorphous rapid-quenched strips. The final state of spherical particles has an X-ray amorphous structure, as indicated by a broad halo of scattered intensity typical of amorphous materials. An even distribution of chemical elements across the particle section could be observed. Bulk samples were made using the method of spark plasma sintering and applying varying parameters of temperature and dwelling time. The authors looked at the microstructure and microhardness of the bulk samples and carried out an X-ray phase analysis. The samples were found to have an X-ray amorphous structure during spark plasma sintering in the temperature range of 320 to 340 оC. However, at the temperatures of 320–325 оC, the resulting samples have a high internal porosity, which cannot be fixed with a pressure rise. The greatest compaction is achieved at the temperatures of 335 to 340 оC. By varying the dwelling time, the authors determined the optimal regime for producing bulk amorphous alloys: sintering at 340 оC and the pressure of 50 MPa, dwelling for 15 min followed by cooling at the rate of 80 оC/min. The samples produced in the above conditions have no visible porosity, and their microhardness is closest to that registered in cast samples.Contributors to this research include O. N. Sevryukov, Associate Professor, Candidate of Technical Sciences; P. V. Morokhov, Lead Engineer; P. S. Dzhumaev, Associate Professor, Candidate of Technical Sciences; I. V. Kozlov, Engineer; V. V. Mikhalchik, Senior Lecturer, Candidate of Technical Sciences; D. S. Gorbunov, Senior Lab Assistant (National Research Nuclear University MEPhI); A. A. Fadeev, Research Fellow; I. D. Zavertyaev, Junior Researcher (Baikov Institute of Metallurgy and Materials Science at the Russian Academy of Sciences).

Effective Cu/ZnO/Al2O3 Catalyst for Methanol Production: Synthesis, Activation, Catalytic Performance, and Regeneration

A precursor CuO/ZnO/Al2O3 catalyst for methanol synthesis has been prepared at room temperature by introducing a ternary salt solution into the excess of sodium carbonate solution following the reverse co-precipitation method. The catalyst was tested for the synthesis of methanol from synthesis gas. The composition (vol. %) has been presented: CO, 22; CO2, 5.8; N2, 5.5; H2, balance. The methanol productivity was recorded to be 2.7 kg kgcat–1 h–1 at a temperature of 260 °С, a pressure of 3 MPa, and a space velocity of 61,700 l (kgcat)–1 h–1. The possibility of regenerating the activity of a catalyst subjected to conditions of artificial aging (overheating in a syngas environment) has been tested: approximately 92% of the initial activity could be restored. Physicochemical studies were conducted using the thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), the scanning electron microscopy (SEM), and the X-ray diffraction (XRD) techniques using the Cu, Zn, and Al oxides obtained following the co-precipitation method. X-ray studies revealed that an amorphous phase was obtained from the Al oxide that was synthesized following both the direct and reverse co-precipitation methods. The calcination temperature was 300 °C. Individual oxides of Cu and Zn obtained following the reverse co-precipitation method form crystalline phases when calcined at 300 °C. When all three ingredients are present, calcination of the sample at 300 °C helps obtain an X-ray amorphous structure of the catalyst characterized by a high specific surface area. High-temperature carbonates are formed from samples prepared using a ternary mixture of nitrate salts when these are calcined at 300 °C.

Tailoring of rhenium oxidation state in ReOx thin films during reactive HiPIMS deposition process and following annealing

Bulk rhenium trioxide (ReO3) has an unusually high electrical conductivity and, being nanosized, has promising catalytic properties. However, the production of pure ReO3 thin films is challenging due to the difficulty to stabilize rhenium in a 6+ oxidation state. Here we present a novel approach for the deposition of ReOx (x ≈ 1.6–2.9) thin films using reactive high power impulse magnetron sputtering (r-HiPIMS) from a metallic rhenium target in a mixed Ar/O2 atmosphere. The thin films were deposited in the gas-sustained self-sputtering regime, observed during r-HiPIMS process according to current waveforms. The influence of the substrate temperature, the oxygen-to-argon flow ratio and post-annealing at 250 °C in the air for 3 h on the properties of the films were studied. The as-deposited films have an X-ray amorphous structure (a-ReOx) when deposited at room temperature while a nano-crystalline β-ReO2 phase when deposited at elevated temperatures (150 or 250 °C). The amorphous a-ReOx can be converted into the crystalline ReO3 with a lattice parameter of 3.75 Å upon annealing in the air. The surface morphology of the films is dense without detectable voids when elevated substrate temperatures are used. Various Re oxidation states are observed on the surface of the films in different ratios depending on the deposition parameters. All samples exhibit electrical resistivity on the order of 10−3 Ωcm and optical properties typical for thin metallic films.

Influence of annealing on mechanical properties of alloys of Al-REM-Ni(Fe)

Have been investigated the influence of annealing on the physicochemical properties of amorphous alloys based on aluminum. It has been established that: after annealing during 5, 15, 30, 45, 60 min at the temperature of the third stage of crystallization, an X-ray amorphous structure with an insignificant volume fraction of a disordered nanocrystalline phase forms. The temperature of annealing was determined from DSC-curves. In structural transformations under these conditions, the microhardness of the alloys increases to a maximum degree in these conditions. The optimal time limits of time heat treatment to improve the physicochemical properties of aluminum-based AMAs have been established.

Investigation of the structure and electrical properties of nanocomposite films W-=SUB=-x-=/SUB=-Si-=SUB=-1-x-=/SUB=-

An experimental investigation of the structure and phase composition by X-ray, Raman, and ultrasoft X-ray emission spectroscopy, as well as the study of the electrical properties of WxSi1-x films used as sensitive elements of superconducting single-photon detectors (SNSPD), depending on the thickness in the range from 7 to 80 nm, was carried out, according to the results of which it was found that the W3Si phase is presumably formed in films 20 and 40 nm thick with a resistivity of 8.4·10-5 and 6.0·10-5 Ω ·cm, respectively, containing the WSi2, W5Si3, and SiO2 phases, as well as WOx and a small share of β-W. Films with a thickness of 7 nm have the highest resistivity of 18.0·10-5 Ω ·cm and contain nanocrystals, WSi2, SiO2, as well as β-W, and an amorphous silicon phase. Films with a thickness of 80 nm (the resistivity is also 18.0·10-5 Ω ·cm) predominantly contain WSi2, as well as W5Si3 and SiO2, and, presumably, the W3Si phase. Keywords: Superconducting single-photon detector, phase composition, X-ray amorphous structure, WSi superconducting films, spectroscopy.

Efficiency definition of the deposition process of electrochromic Ni(OH)2-PVA films formed on a metal substrate from concentrated solutions

Electrochemical devices based on nickel hydroxide electrodes are used in different areas. The main ones are chemical current sources, variable transparency “smart” windows, devices for carrying out electrocatalytic reactions, sensors for determining various substances. In this regard, methods of nickel hydroxide synthesis are of great interest, especially those that allow forming nickel hydroxide directly on the surface of electrodes. One of these methods is electrochemical deposition with cathodic current polarization. The available information on nickel hydroxide synthesis from nickel solutions was considered. It was shown that the available data mainly covered information on dilute solutions from 0.01 to 0.25 mol/L Ni(NO3)2. In addition, no comparison was found in the literature for the efficiency of the cathodic formation of Ni(OH)2 at different concentrations of nickel nitrate. To eliminate the lack of information, the dependence of the current efficiency on the concentration of nickel nitrate in the electrodeposition solution was determined at a constant cathode current density of 0.625 mA/cm2. The resulting dependence decreased nonlinearly with increasing concentration. The nickel hydroxide deposit formed in this case had an X-ray amorphous structure, and it depended little on the Ni(NO3)2 concentration. In addition, the current efficiency reached zero at concentrations of 1.5 mol/L Ni(NO3)2 and higher. However, with polyvinyl alcohol in the solution and at Ni(NO3)2 concentrations of 1.5 and 2 mol/L, electrochemically and electrochromically active Ni(OH)2 films were deposited. The current efficiency calculated indirectly for 1.5 and 2 mol/L Ni(NO3)2 solutions was 3.2 and 2.3 %, respectively. Thus, it was concluded that polyvinyl alcohol affected the mechanism of nickel hydroxide electrodeposition from aqueous solutions of nickel nitrate.

Corrosion and mechanical properties of nanostructure electrolytic Co-W and Fe-Co-W alloys

It has been shown that the corrosion-electrochemical behavior of coatings with iron (cobalt) tungsten alloys depends on the content of the refractory component, and an increase in chemical resistance in the acidic medium is due to the formation of acidic tungsten oxides on the surface. The use of artificial neural networks allowed us to identify the most significant parameters that determine the corrosion resistance of alloys. The microhardness of the coatings under study depended on the content of tungsten and exceeds the characteristics of individual metals, which makes it possible to recommend such materials as an alternative to hard chromium coatings. An increase in corrosion resistance and microhardness of coatings by alloys is associated with the formation of a fine-crystalline and X-ray amorphous structure of the surface layers when using non-stationary modes of electrodeposition.

Effect of ultraviolet irradiation or diffuse discharge plasma on structure and surface electrical charge of micro-arc calcium phosphate coatings

The studies of the effect of ultraviolet (UV) irradiation and plasma of a runaway electron preionized diffuse discharge (REP DD) post-treatments on the surface structure and electrical charge of the micro-arc oxidation (MAO) coatings were performed. The UV irradiation and plasma treatment did not effect on the morphology, roughness and thickness of the MAO coatings. However, these post-treatments led to formation of the small fraction of the crystalline CaHPO4phase in the X-ray amorphous structure of the coatings. Moreover, the UV and REP DD plasma treatments increased the electrostatic potential (EP) negative values from –85 mV to –126 mV of the coatings in the following order: MAO < MAO/UV (for 5 min) < MAO/Plasma (with 10,000 pulses) < MAO/UV (for 20 min) < MAO/Plasma (with 80,000 pulses).

Conditions for partial and complete crystallization suppression upon quenching from liquid state

For bulk-amorphizing alloys Мg65Сu25Y10 and Zr41,2 Тi13,8Сu12,5Ni10Ве22,5, the thickness and cooling rate of melt layers is calculated, which ensure the formation of X-ray amorphous structures typical for metallic glasses ( lC, vC ), and truly amorphous states without inclusions of «frozen-in crystallization centers» (lc*, vc* ). Correlation of the calculated values lC, vC with the known experimental estimates is C Cachieved. It is shown that both studied alloys demonstrate a predisposition to complete suppression of crystallization processes at physically correct values of the parameters lc* and vc* (10 μm; 1,3·107 K/s and 550 μm; 2,7·103 K/s for alloys based on Mg and Zr, respectively). It is concluded that the most significant factors controlling the tendency of materials to noncrystalline solidification are the decrease in the frequency of non-stationary nucleation with the increase in the rate of QLS, as well as relatively low &lt;1018 m-3 s-1) maximum values of the rate of stationary crystallization centers formation.

Synthesis and Physicochemical Study of Xanthan Butyl Ether

Xanthan is an important polysaccharide widely used in many industrial fields. It is produced by the bacteria Xanthomonascampestris. Chemical modification of xanthan can open up new horizons for its use. In this work, xanthan butyl ester was obtained for the first time by the interaction of xanthan and bromobutane using sodium hydroxide as a catalyst. The composition and structure of the obtained new xanthan derivative was studied by elemental analysis, IR spectroscopy, X-ray phase analysis, scanning electron microscopy and thermal analysis. The introduction of a butyl group into the xanthan molecule was proved by elemental analysis and IR spectroscopy by the appearance of corresponding bands. It was shown by X-ray phase analysis that xanthan butyl ether has a more X-ray amorphous structure in comparison with the original xanthan. It was shown by scanning electron microscopy that xanthan butyl ether powder consists of particles of a larger size and a layered structure in comparison with the original xanthan. It has been shown by thermal analysis that xanthan butyl ether is less thermostable than the starting xanthan

Structure and phase composition of aluminosilicate-based microspheres

The paper focuses on aluminosilicate-based microspheres, whose shell represents an X-ray amorphous state, which significantly reduces their strength properties. However, a number of technological characteristics used in industry provide the formation of glass-ceramic and crystalline states of the condensed phase, which is the shell microsphere. Presently, the formation of the structure and phase composition during the interaction between aluminosilicates (the SiO2/Al2O3 ratio varies between 0−100 %) and high-temperature (≥ 5000 K) plasma is most interesting. This paper presents the research results of the structure and phase composition of the aluminosilicate-based condensed phase during the microsphere production. The X-ray phase analysis shows that after cooling, the structure and phase composition of the microsphere shells based on refractory polycrystalline materials promotes the formation of the X-ray amorphous structure at SiO2 ≥ 60 wt. % in the initial powder and the transition of γ-Al2O3 cryptocrystalline phase to high-temperature α- Al2O3 phase with the use of the initial alumina powder.

Response of electrical and dielectric parameters of ZnIn2Te4 thin films to temperature and frequency

ZnIn2Te4 has been synthesized in the bulk form by the melt and gradually cooling method. Then, thermally evaporated thin films have been prepared with different thicknesses (173–385 nm). X-ray diffraction shows X-ray amorphous structure for the prepared films. Energy dispersive X-ray has been used to evaluate the composition of the prepared materials. The temperature dependence of dc and ac conductivities has been studied in the range: 303–413 K. The dc conductivity obeys Mott and Davis model showing semiconducting behavior with two conduction mechanism in this temperature range. Then, dependence of the ac conductivity and dielectric parameters on the frequency has been studied in the range: 1 kHz–1 MHz. Correlated barrier hopping between centers of non-intimate valence alternation pairs is the mechanism describing the response of ac conductivity to the frequency. Both, dielectric loss and dielectric constant increase with increasing the temperature and with decreasing the frequency.

Structure, mechanical properties and corrosion resistance of amorphous Ti-Cr-O coatings

In this work, titanium‑chromium oxide (TCO) coatings were investigated aiming to produce a functional hard-corrosion resistance coating based on the well-known properties of the individual TiO2 and Cr2O3 oxides. The TCO coatings were deposited on low carbon steel and Si substrates using reactive magnetron sputtering from a crystalline TiCr target. Amorphous TCO coatings with increasing oxygen content up to 65 at.% were obtained by rising the oxygen flow rate during the reactive deposition. Coatings deposited using constant O2 flow rate of 1.5 (6.2% of oxygen) were selected to evaluate the corrosion resistance, hardness and to determine the effect of annealing treatments. Electrochemical evaluation was done using impedance spectroscopy and potentiodynamic polarization in 3.5 wt% NaCl solutions showing a significant protection efficiency. The coatings were heat treated at different temperatures (200, 400, 500, 600 and 800 °C) for 2 h in air. The coatings were analyzed by X-ray photoelectron spectroscopy to obtain the composition, X-ray diffraction (XRD) and scanning electron microscopy for microstructural and morphological characterization, respectively. The XRD results show that the heat-treated coatings maintained the X-ray amorphous structure up to 500 °C. Above this temperature, the coatings crystallize forming large Cr2O3 crystals segregated to the surface leaving an amorphous TiCr bottom layer.

Evolution of the Al85Ni5Fe7La3 Amorphous Alloy Structure under Flash Lamp Annealing

The microstructure of Al85Ni5Fe7La3 amorphous alloy after high-speed quenching, isothermal annealing, and flash lamp annealing (FLA) was studied by electron microscopy (including the high-resolution transmission electron microscopy), electron and X-ray diffraction, energy-dispersive X-ray microanalysis, and differential scanning calorimetry. A comparative analysis of the structures with respect to phase composition and phase morphology was performed. It was shown that, after the quenching, an X-ray amorphous structure is formed in the alloy. Critical parameters of heat treatment of the amorphous alloy which lead to single-phase or multiphase crystallization and volumetric or gradient structure were determined. The phase composition of the nanocomposite formed during crystallization was determined. The identity of the emerging structures with respect to the phase composition and phase morphology was determined for certain parameters of isothermal and flash lamp annealing to which close values of microhardness significantly exceeding the hardness of the alloy in the amorphous state correspond.

Effect of micro-arc oxidation time and applied voltage on formation of strontium- and silicon-incorporated biocoatings

The study of the influence of the MAO time and applied voltage on the formation of the structure, phase and elemental compositions, and properties of Sr-Si-CaP coatings on the titanium surface were performed. It was established that the coating thickness, roughness and the average size of the structural elements (spheres and pores) grow linearly with increasing of the MAO voltage from 200 to 370 V. While, the MAO time effects only on the coating thickness. XRD revealed that the coatings deposited at the low voltages of 200-250 V have X-ray amorphous structure. Increase of the voltage to 350 V leads to the formation in the coatings of crystalline-amorphous structure with amount of crystalline monetite (CaHPO4) phase to 35±5 wt.%. The EDX microanalysis showed that maximum Ca/P atomic ratio of 0.9 and maximum contents of 1.0 at.% Sr and 1.2 at.% Si were found on the coating surface in the regions of accumulation of the monetite crystals for the coatings deposited at high voltages of 300-350 V.

Microstructure and Mechanical Properties of Multilayer α-AlN/α-BCN Coating as Functions of the Current Density during Sputtering of a B4C Target

Multilayer AlN/BCN coating of nanometer scale have been prepared by magnetron sputtering of Al and B4C targets in an argon–nitrogen atmosphere during deposition on a Si substrate. These coating have an X-ray amorphous structure and the maximum Knoop hardness of 27 GPa (at the current density 100 mA). The first-principle molecular dynamics calculations show that the B4–BN layer is dynamically unstable; thus, it will not be epitaxial and will be amorphous or have a structure different from the B4–BN structure. The thermal vacuum annealing from 600 to 800°C of samples with multilayer nanosized coating leads to the decrease in the Knoop hardness to 18 GPa; however, the coating structure is retained X-ray amorphous.

Impact of Al or Si addition on properties and oxidation resistance of magnetron sputtered Zr–Hf–Al/Si–Cu metallic glasses

Amorphous quaternary Zr–Hf–Al/Si–Cu thin-film metallic alloys were prepared by non-reactive magnetron co-sputtering using four unbalanced magnetrons equipped with Zr, Hf, Al or Si, and Cu targets. The Zr, Hf and Al or Si targets were sputtered in dc regimes while the Cu target in a high-power impulse regime. Two series of films with either Al (up to 17 at.%) or Si (up to 12 at.%) addition were deposited. The effect of the elemental composition on the structure, thermal behavior, mechanical and surface properties, electrical resistivity and oxidation resistance was systematically investigated. All Zr–Hf–Al/Si–Cu films were deposited with an X-ray amorphous structure. The glass transition was, however, recognized only up to 12 at.% Al or 6 at.% Si. The addition of Al or Si enhances mechanical properties of the films and the thermal stability of their amorphous state. This may be explained by an increase of a covalent component of the mixed metallic-covalent bonds with increasing the Al and Si content. Moreover, the Zr–Hf–Al–Cu metallic glasses exhibit a wider super-cooled liquid region, while the Zr–Hf–Si–Cu metallic glasses are more oxidation resistant.

Mechanical properties, bonding characteristics, and oxidation behaviors of Nb–Si–N coatings

Nb–Si–N coatings with Si contents of 0–30 at% were fabricated through reactive direct current magnetron cosputtering. The processing parameters were various sputtering powers, substrate holder rotation speeds, and nitrogen flow ratio (N2/(N2 + Ar)). Three phase regions, namely face-centered cubic (f.c.c.) NaCl structure, X-ray amorphous, and nanocrystalline phases, were identified and related to the chemical compositions of the coatings. Low-Si-content (0–13 at%) and middle-N-content (39–45 at%) Nb–Si–N coatings exhibited an f.c.c. structure, high-Si-content (17–30 at%) and high-N-content (45–53 at%) Nb–Si–N coatings exhibited an X-ray amorphous structure, and low-Si-content (6 at%) and low-N-content (26–30 at%) Nb–Si–N coatings exhibited a nanocrystalline structure. Examining the bonding characteristics of the Nb–Si–N coatings by using X-ray photoelectron spectroscopy indicated that NbN tended to form preferentially and was followed by Si3N4, which is consistent with the laws of thermodynamics. The correlations between the mechanical properties, residual stresses, and structures of the Nb–Si–N coatings were investigated using nanoindentation, a curvature method, and X-ray diffraction. The oxidation behaviors of the Nb–Si–N coatings annealed in air at 400–600 °C were also examined.