Substitutional Solid Solutions Research Articles

Material design based on impurity element doping for photoelectrochemical capacitor composite electrodes using metal oxides

To evaluate the properties of TiO2/MnO2 composite electrodes for use as photoelectrochemical capacitors, Zn-doped TiO2 with a rutile-type structure hydrothermally synthesized as a photoelectric conversion material. The substitutional solid-solution of 2 at.% Zn in TiO2 successfully increased the oxygen vacancy amount and the electronic conductivity. A wider optical band gap was observed for the Zn-doped TiO2 compared with an undoped TiO2, indicating that Zn doping increased the carrier concentration due to the generation of oxygen vacancies. The photovoltage of the TiO2 electrode was drastically enhanced from 250 to 1600 mV by 2 at.% Zn doping. The charge-discharge properties of the Zn-doped TiO2/MnO2 composite electrodes were evaluated by photoirradiation of Zn-doped TiO2, where Na+ adsorption−desorption reactions occurred on the MnO2 surface. The Zn-doped TiO2/MnO2 composite electrodes afforded a larger discharge capacity of 13 mA h cm−2 compared to 7 mA h cm−2 for the TiO2/MnO2 composite. Plausibly, the higher carrier concentration increased the Fermi level above the conduction band of TiO2, enabling conducting electrons to overcome the energy barrier between the TiO2 particles. Doping Fe into MnO2 in the composite electrode further enhanced these properties, and Fe doping increased the capacity of the composite from 13 to 25 mA h cm−2. These results demonstrate that the commonly used approach of doping with impurity elements can improve the properties of various electrode materials for use as photoelectrochemical capacitors.

Effects of Zr/(Zr+Ti) Molar Ratio on the Phase Structure and Hardness of TixZr1−xN Films

TixZr1−xN hard films with Zr/(Zr+Ti) molar ratios from 20% to 80% were prepared by multi-arc ion plating using any two of elemental Ti, elemental Zr, and TiZr alloy targets. The as-deposited TixZr1−xN films displayed similar surface and fracture cross-section morphologies and thicknesses. The effects of Zr/(Zr+Ti) molar ratio on the phase composition, preferred growth orientation, and hardness of the films were discussed. The results showed that the as-deposited films had a face-centered cubic structure and exhibited the typical characteristics of substitutional solid solutions. The lattice constant of the films increased monotonically with increasing Zr/(Zr+Ti) molar ratio. Two preferred growth orientations, corresponding to the two hardness peak values, occurred symmetrically at Zr/Ti molar ratios of 40:60 and 60:40. An inflection point with a small reduction in hardness was observed at the Zr/Ti molar ratio of 50:50.

Effect of Zn additions on the microstructure and mechanical properties of Sn-Babbitt alloys fabricated by arc deposition

A deposited layer of Sn-based Babbitt alloys was fabricated on the surface of the steel substrate via the arc deposition technique. The effect of the composition of Zn on the microstructure and mechanical properties has been systematically studied. The morphology of Babbitt alloys and the interfacial microstructure of the interface between the cladding layer and substrate have been investigated. The experimental results revealed that SnSb phases and Cu6Sn5 phases become more uniformly dispersed in the Sn-matrix as Zn composition increased, which resulting in the improvement of hardness and tensile strength. The enhanced performance can be attributed to precipitation strengthening of the newly formed substitutional solid solution Cu6Zn0.5Sn4.5. The bonding strength of Babbitt and steel has been tested according to the standard destructive testing method of sliding bearing. The bonding strength increased and decreased with the increment of Zn, since excessive Zn led the fracture site to shift from the SnSb phase to the segregated Cu6Sn4.5Zn 0.5 at the interface near IMC layers.

A high-density non-equiatomic WTaMoNbV high-entropy alloy: Alloying behavior, microstructure and mechanical properties

A bulk fine-grained W35Ta35Mo10Nb10V10 (at%) high-density high-entropy alloy (HEA) was successfully fabricated by mechanical alloying (MA) and spark plasma sintering (SPS) with varying parameters. Microstructure evolution and mechanical behavior of the HEA samples in various processing conditions were investigated. The alloying effect in the mixed high-purity powders becomes more significant as the increase of ball milling time during MA. Upon SPS at various temperatures ranging from 1600 to 1800 °C, a supersaturated body-centered-cubic (BCC) matrix prevails with the precipitation of Ta2VO6 oxides. After SPS at 1700 °C for 10 min, the average mass density, ultimate compressive strength and microhardness of the bulk HEA at room temperature are 14.65 g cm−3, 2519 MPa and 6.50 GPa, respectively. The mechanisms responsible for the high strength and hardness include massive substitutional solid solution strengthening by the alloying of multiple principal elements, grain boundary strengthening, precipitation strengthening by Ta2VO6 particles, and interstitial solid solution strengthening by interstitials (e.g., tramp O from processing) in the matrix. The systematic information on the relationships among processing parameters, alloy densities, microstructure characteristics (e.g., grain sizes, volume fractions and sizes of precipitated oxides) and mechanical properties provide useful insights for the development of novel high-density and high-strength materials.

Electrochemical deposition of cobalt alloy

Electrodeposition of cobalt alloys with refractory metals makes it possible to obtain coatings with a unique combination of physicochemical properties that are unattainable using other deposition methods. For the deposition of high-quality coatings with a cobalt-vanadium alloy, it is proposed to use a citrate electrolyte. Co-V coating was deposited on steel samples from citrate electrolyte at a temperature of 35-40 °C and a current density of 5-12 A/dm2 using soluble cobalt anodes. The vanadium content in the coating deposited at a ligand concentration of 0.3 mol / dm3 is 0.1-0.5 wt%. An increase in the concentration of the ligand to 0.4 mol / dm3 promotes the binding of cobalt into complexes, and, accordingly, the vanadium content in the coating increases to 0.6-1.2 wt.%. Moreover, the tendency to change the percentage of alloying elements with current density remains. Deposition coatings are dense, shiny, without internal stresses and cracks. The proposed compositions of electrolytes and modes of deposition of Co-V coatings with a vanadium content of up to 1.5 wt.% And a current efficiency of 50%. It was found that Co-V coatings are characterized by increased carbon content and are substitutional solid solutions, and the surface morphology of the obtained coatings depends significantly on the current density and changes from fine-crystalline to globular spheroid. The optimal current density for obtaining high-quality coatings with a cobalt alloy in a galvanostatic mode is ік = 10 A / dm2. Management of the storage of galvanic cobalt alloys in a quite wide range of concentrations of alloy-forming components is achieved by varying the electrolysis parameters, which allows the deposition technology to be adapted to the needs of the modern market.

Application of adsorbents based on LaFe1-xMnxO3 perovskites to treat As, Pb in contaminated groundwater in the craft village

The nanoparticle crystals of perovskite LaFe1-xMnxO3 were prepared by the PVA (polyvinyl alcohol) gel combustion method to determine the adsorption capacity of As(V), Pb2+ from solution was investigated. Single-phase crystalline perovskite of LaFe1-xMnxO3 is formed by solid solution formation which completely replaces LaFeO3 perovskite and LaMnO3 perovskite. In LaFe1-xMnxO3 perovskites, the x substitution composition, or the rate of participation to form the substitution solid solution between the two components LaFeO3 and LaMnO3 will determine the type of original structure, the interaction between the Fe and Mn in in the crystal lattice. Thereby determining the characteristics and adsorption activity of perovskite LaFe1-xMnxO3. Perovskite LaFe1-xMnxO3 with the formula LaFe0.3Mn0.7O3 gave the best As(V) adsorption efficiency on the x components, while the LaFe0.7Mn0.3O3 formula gave the best As(V) adsorption efficiency on the x components. The LaFe1-xMnxO3 perovskite-based adsorbent pelletized with the composition LaFe0.3Mn0.7O3-LaFe0.7Mn0.3O3-bentonite has practical potential to remove arsenic, lead in contaminated water.

Crystal structure and magnetic characteristics of solid solutions Ni<sub>1–x</sub>Cr<sub>x</sub>MnSb

The results of an experiment on studying the features of the crystal structure and magnetic studies of substitutional solid solutions of the Ni1–xCrxMnSb system (0 m х m 0.2) are presented. It was found that an increase in the concentration of chromium in solid solutions does not lead to significant changes in the size of the unit crystal cell. It was found that solid-phase quenching can be used to expand the limit of chromium solubility in Ni1–xCrxMnSb solid solutions. The temperature and field dependences of the specific magnetization of the synthesized compositions have been studied. It was found that the substitution of chromium for nickel in the NiMnSb compound leads to a decrease in the temperature of the “magnetic order – magnetic disorder” phase transformation with an increase in the concentration x from 0 to 20 mol.%. The values of specific magnetization and Curie temperature of hardened hard rasters are higher than those of slowly cooled ones. The results obtained contribute to the creation of a physical basis for the elemental base of spintronics.

Відпускна крихкість литої штампової сталі 4Х4Н5М4Ф2

The results of research of structural steel brand 4Kh4N5М4F2 after heat treatment are given. Manifestations of tempering brittleness at a temperature of 450-500 °C, associated with the maximum value of the parameter «a» of the crystal structure during the formation of a solid substitution solution in the system "Fe-C". The connection between the peculiarities of the crystal structure of the studied steel and the complex of physical and mechanical properties is established. The maximum value of the parameter «а» (a = 0.28848 nm) of the elementary cell of martensite crystal lattice reflects the maximum saturation of the α-solid solution, which increases the resistance of the crystal lattice to deformation, increase the hardness of tempering martensite (up to 56 HRC), change the physical structure sensitive value (increase in specific conductivity to 0,200 Om•mm2/m), increase the tensile strength, reduce the impact strength (up to 15 J/cm2) and increase the brittleness at temperatures of 450-500 °C. The possibility of using matrices (steel 4Kh4N5М4F2, without forging technology) for hot deformation of aluminum alloy AK7ch, which during operation does not reach the temperature of brittleness (above 460 ºC), is demonstrated. Keywords: die steel, crystal structure, heat treatment, physical and mechanical properties.

Production of high-entropy Fe–Cr–Co–Ni–Ti alloy by mechanical alloying and spark plasma sintering of a powder mixture

A two-phase powder alloy based on substitutional solid solutions with BCC and FCC lattices was obtained by highintensity mechanical treatment (HMT) of a multicomponent Fe–Cr–Co–Ni–Ti powder mixture. Sample sections and particles of mixtures obtained were studied using an ultra high resolution field emission scanning electron microscope by scanning electron microscopy. XRD patterns of mixtures were recorded on the DRON 3 diffractometer with FeKα and CuKα radiation. It was found that after 10 minutes of HMT one intense superposition reflection remains on the XRD pattern with the angular position corresponding to Reflections 111 and 110 of phases with FCC and BCC lattices, respectively. A spark plasma sintering (SPS) method was used to obtain compact high-entropy material samples from the mixture after 90 minutes of HMT at 800 and 1000 °C. Their specific electrical resistance and density as well as the dependence of these properties on the sintering temperature were determined. It was demonstrated that the substitutional solid solution with the BCC lattice is probably enriched with titanium during the powder alloy SPS process.

A flow loop study on the effect of Ca2+ ions on the CO2 corrosion of 1Cr carbon steel in a CaCO3-saturated solution

ABSTRACT This paper investigates the effect of calcium on the CO2 corrosion behaviour of 1Cr carbon steel under the effect of flow. The experiments were performed in a flow loop system in 1 wt-% NaCl solution at 80°C, pH = 6.34 with initial S CaCO3 = 2 and pCO2 = 0.53 bar. The flow velocity was kept at 3 m s−1 and the system was pressurised to 3 bar. The corrosion process was monitored with linear polarisation resistance and electrochemical impedance spectroscopy (EIS). Phase analysis of the corrosion products was obtained using X-ray powder diffraction and surface morphology was characterised with scanning electron microscopy. Results show that the flow delayed the precipitation of substitutional solid solution of Fe0.31Ca0.69CO3, deferring the pseudo-passivation stage. The flow did not cause Mesa attack or localised corrosion. The protectiveness of this film was not affected by the presence of calcium and was comparable to the one of pure FeCO3.

Modeling of structural and energetic parameters of р-Er1-xScxNiSb semiconductor

The energy expediency of the existence of Er1-xScxNiSb substitutional solid solution up to the concentration x≈0.10 was established by modeling the variation of free energy ΔG(x) values (Helmholtz potential). At higher Sc concentrations, x> 0.10, there is stratification (spinoidal decomposition of phase). It is shown that in the structure of p-ErNiSb semiconductor there are vacancies in positions 4a and 4c of Er and Ni atoms, respectively, generating structural defects of acceptor nature. The number of vacancies in position 4a is twice less than in position 4c. This ratio also remains for p-Er1-xScxNiSb. Doping of p-ErNiSb semiconductor by Sc atoms by substitution of Er atoms is also accompanied by the occupation of vacancies in position 4a. In this case, Ni atoms occupy vacancies in position 4c, which can be accompanied by the process of ordering the p-Er1-xScxNiSb structure. Occupation of vacancies by Sc and Ni atoms leads to an increase of the concentration of free electrons, an enlarge of the compensation degree of semiconductor, which changes the position of the Fermi level εF and the mechanisms of electrical conductivity.

Growing the solid solution of molekular substitution (GaAs)1-z(ZnSe)z

Epitaxial layers of semiconductor solid solutions of molecular substitution (GaAs)1-z(ZnSe)z (0 < z < 0.80) with a smoothly (but not monotonously) varying composition were obtained from the liquid phase on monocrystal GaAs (100) substrates. The solubility of gallium arsenide and zinc selenide in tin and the phase diagrams of binary systems Ga-Sn, As-Sn, Zn-Sn and Sn-Se indicate that binary compounds in the tin solvent at temperatures of 650–750°C, below the melting point of the corresponding materials, are not in the form of individual atoms of gallium, arsenic, zinc and selenium, but in the form of molecules of gallium arsenide and zinc selenide. Moreover, in the temperature range 650-750°C, the solubility of GaAs in tin varies from ∼ 2.6 to ∼ 5.5 mol%, and ZnSe - from ∼ 0.2 to ∼ 0.35 mol%, the solubility of gallium and zinc is unlimited, and the solubility of arsenic is more than 70 at. %, selenium - more than 5 at.%. It is shown that due to the difference in the valence of gallium and arsenic atoms, the forces of chemical bonds between neighboring Ga and As atoms located in the tetrahedral lattice are not the same. In the tetrahedral lattice, each Ga atom forms 4 bonds with four neighboring As atoms, three of which are formed by the sharing of electrons of neighboring Ga and As atoms, and the fourth one only due to the two valence electrons of the As atom. Apparently, the ionic fraction of the fourth chemical bond is stronger than the other three.

Static Displacements and Short-Range Order in Ni-14 at. % Ir Alloy

In this paper, we are proposing a novel method to estimate static displacements of atoms caused by size effects in fcc substitutional binary polycrystalline solid solutions. Fourier transforms of static displacements of the atoms on every considered shell were calculated using the equations that include dynamical matrix and Fourier transform of interatomic forces. Short-range order parameters on the first seven shells of Ni-14 at. % Ir alloy have been identified from X-ray diffuse scattering intensity by accounting microscopic static displacements of atoms on a particular shell. Pairwise interatomic potentials on the considered shells and critical temperature of disorder-order phase transition were calculated using values of short-range order parameters.

Slag design and iron capture mechanism for recovering low-grade Pt, Pd, and Rh from leaching residue of spent auto-exhaust catalysts

Recovery of platinum group metals (PGMs) from secondary resources has attracted worldwide attention from environmental and economic points of view. Pyrometallurgical routes exhibit the superiority in terms of efficiency and contamination control compared to hydrometallurgical process. However, traditional pyrometallurgical processes face the challenges of excessive flux and energy consumption. In this paper, an iron capture process was proposed to recover low-grade PGMs from leaching residue of spent auto-exhaust catalysts. Slag design was explored aimed at reducing the addition amount of flux. The optimized smelting conditions were as follows: 1400 °C for 30 min, adding 40.0 wt% CaO, 22.7 wt% Na2CO3, 5.0 wt% Na2B4O7, 5.0 wt% CaF2, 15.0 wt% Fe, and 5.0 wt% C. The concentrations of Pt, Pd and Rh remaining in the smelting slag were 0.83 g/t, 4.99 g/t, and 1.47 g/t, respectively. Furthermore, the 50 kg-scale experiment implied positive economic feasibility because of saving flux dosage and smelting time. The capture mechanism was revealed by investigating the formation of the metals phase and slag phase. Matrix formed slag phase and separate with metals phase owing to differences in chemical bonding, density, viscosity, and surface tension. PGMs were proved solubilized in α-Fe as substitutional solid solutions. The formation energies for FePt, FePd, and FeRh alloys were −4.149 eV, −4.040 eV, and −4.360 eV, respectively. Finally, the obtained CaO-SiO2-Al2O3-Na2O glass slag was used for producing glass ceramics. To sum up, the iron capture process realized low energy and material consumption, high recovery efficiency of PGMs, and resource utilization of the glass slag.

Electric field-assisted synthesis/sintering cerium oxide: 5 wt.% gadolinium oxide

Gadolinium oxide ceramic powders were mixed to cerium oxide ceramic powders, pressed to pellets, and sintered either at 1450 °C or applying 200 V cm−1 electric field at 800 °C, 900 °C and 1000 °C. The structural phases and the microstructure of the sintered pellets were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The formation of substitutional solid solution was followed by monitoring the increase of the electrical conductivity by impedance spectroscopy and X-ray diffraction. The main results show that Joule heating due to the flow through the pellets of the electric current, which was produced by the application of the electric field, allows for promoting partial solid solution as well as partial sintering the ceria-gadolinia pellets. Moreover, grain growth that occurred in the high temperature sintered pellets was inhibited in the electric field-assisted synthesized/sintered pellets, being an alternative technique for producing cerium oxide-gadolinium oxide solid solutions.

Solid state synthesis and properties of new semiconducted CuTa2-xSbxO6 solid solution

A new substitutional solid solution of the general formula CuTa2-xSbxO6 and with a limited range of homogeneity (0 < x ≤ 0.5) was found to form in the binary CuTa2O6–CuSb2O6 system. Maximal replacement of Ta5+ by Sb5+ ions reaches at least 25 mol%. The new phase was synthesized by the conventional solid-state reaction using the starting mixtures of reactants containing both CuO, Ta2O5 and α-Sb2O4 oxides as well as CuTa2O6 and CuSb2O6 compounds. The obtained solid solution was characterized by XRD, DTA, IR and UV–Vis-DRS methods. The effects of the degree of Sb5+ ion incorporation in the crystal lattice of CuTa2O6 replacing Ta5+ on the unit cell volume, thermal stability, IR spectra and the energy gap of CuTa2-xSbxO6 in the range 0 < x ≤ 0.5 were determined. The new solid solution is a semiconductor and the energy gap of CuTa2-xSbxO6 decrease from 2.76 to 2.64 eV for 0.10 = x ≤ 0.50.

Formation of CdxPb1−xS/Cd1-δS thin-film two-phase compositions by chemical bath deposition: composition, structure, and optical properties

The possibility of forming thin-film two-phase compositions CdxPb1-xS/Cd1−δS using chemical bath deposition from aqueous media with adding various cadmium salts has been demonstrated. The crystal structure, chemical composition, morphology, and the band gap were studied by the X-ray diffraction, scanning electron microscopy, elemental analysis, Auger and Raman spectroscopy, and diffuse reflectance measurements. The formation of a CdxPb1−xS/Cd1−δS substitutional solid solution phase in well-faceted crystallites on the substrate of an X-ray amorphous CdS phase was experimentally shown. The observed difference in the composition of the films deposited with adding different cadmium salts is the result of the effect of the nucleophilicity of the anionic component of these salts on the kinetics of thiourea decomposition. The results demonstrate the possibility of forming thin-film two-phase compositions or heterostructures on the base of cadmium and lead sulfides in one technological stage using chemical bath deposition, which can be important for the creation of solar cells.

Understanding magnetic phase coexistence in Ru2Mn1−xFexSn Heusler alloys: A neutron scattering, thermodynamic, and phenomenological analysis

The random substitutional solid solution between the antiferromagnetic (AFM) full-Heusler alloy Ru$_2$MnSn and the ferromagnetic (FM) full-Heusler alloy Ru$_2$FeSn provides a rare opportunity to study FM-AFM phase competition in a near-lattice-matched, cubic system, with full solubility. At intermediate $x$ in Ru$_2$Mn$_{1-x}$Fe$_x$Sn this system displays suppressed magnetic ordering temperatures, spatially coexisting FM and AFM order, and strong coercivity enhancement, despite rigorous chemical homogeneity. Here, we construct the most detailed temperature- and $x$-dependent understanding of the magnetic phase competition and coexistence in this system to date, combining wide-temperature-range neutron diffraction and small-angle neutron scattering with magnetometry and specific heat measurements on thoroughly characterized polycrystals. A complete magnetic phase diagram is generated, showing FM-AFM coexistence between $x \approx 0.30$ and $x \approx 0.70$. Important new insight is gained from the extracted length scales for magnetic phase coexistence (25-100 nm), the relative magnetic volume fractions and ordering temperatures, in addition to remarkable $x$-dependent trends in magnetic and electronic contributions to specific heat. An unusual feature in the magnetic phase diagram (an intermediate FM phase) is also shown to arise from an extrinsic effect related to a minor Ru-rich secondary phase. The established magnetic phase diagram is then discussed with the aid of phenomenological modeling, clarifying the nature of the mesoscale phase coexistence with respect to the understanding of disordered Heisenberg models.

A Novel Solid Solution Mn1-xVxP Anode with Tunable Alloying/Insertion Hybrid Electrochemical Reaction for High Performance Lithium Ion Batteries

The substitutional solid solution Mn1-xVxP compounds are proposed as a high performance anode for lithium ion batteries (LIBs) through a novel alloying/insertion hybrid electrochemical reaction concept by combining alloying reaction-type MnP and insertion reaction-type VP. The solid solution series of Mn1-xVxP are successfully synthesized via a facile high energy mechanical milling. Their electrochemical properties as an anode for LIBs are systematically studied and compared with those of MnP/VP mixture, particularly focusing on the verification of simultaneous alloying/insertion hybrid electrochemical reaction in the solid solution compounds. The Mn0.75V0.25P solid solution electrode shows the excellent high rate cyclability delivering the reversible capacity of 321 mAh g−1 after 5000 cycles at a high current density of 1.0 A g−1, resulting from the synergistic effects of two reaction mechanisms. The homogeneously substituted vanadium ions enable the alloying/insertion hybrid electrochemical reaction in a Mn1-xVxP single phase, which can effectively reduce the rate of volume change, hinder the pulverization and agglomeration of alloying reaction-type Li-Mn-P crystallite during cycling, and ensure the fast electron and ion transport. This simple, yet innovative, solid solution design with the consideration of structural relationships and electrochemical properties inspires the development of advanced ternary or multi-component compound electrode materials for LIBs or other energy storage devices.

Morphological and structural features of the CdxPb1−xS films obtained by CBD from ethylenediamine-citrate bath

The calculating of ionic equilibria in the system «Pb(CH3COO)2 - CdCl2 - Na3C6H5O7 - ‎(NH3)2(CH2)2 - N2H4CS» allowed us to find conditions and concentration regions of PbS and CdS co-deposition. The determined conditions provided the CBD obtaining of CdxPb1−xS (0 ≤ x ≤ 0.033) substitutional solid solutions films with a cubic structure B1 (space group Fm ) with the grains preferred orientation (200). We established the evolution of the surface morphology of the synthesized films from cubic crystallites to hierarchical structure of globular aggregates by scanning electron microscopy. A quantitative analysis of diffraction patterns showed a decrease of microstrains in CdxPb1−xS films by a about factor of 3 with an increase of the cadmium chloride concentration in the reaction mixture from 0.005 to 0.14 mol/l. The excess of the cadmium content, established by EDX analysis, in the studied films as compared to its content in the solid solution is associated with the additional formation of the amorphous CdS phase up to 72 mol %.A Corrigendum is available for this article at https://doi.org/10.15826/chimtech.2021.8.2.12.