Multi-element Mixtures Research Articles

High-Entropy Oxides Prepared by Dealloying Method for Supercapacitors

High-entropy oxides (HEOs) are materials with a multielement mixture and a stable structure, which are widely used in energy storage due to their electrochemical properties. For application to supercapacitors, the method of preparation of HEOs needs to be improved, and the energy storage mechanism of the material needs to be investigated. In this experiment, 3 M NaOH was used to etch the FeCoNiCrMnAl95 alloy, and then (FeCoNiCrMn)3O4 was successfully produced by a facile oxidation treatment. HRTEM images show that the materials have a porous structure, and EDS mapping suggests that the individual elements are evenly distributed. The XRD and SAED patterns indicate that it has a stable crystal structure. The HEOs prepared by dealloying exhibited excellent supercapacitor characteristics, with a specific capacitance of 639 F/g at 1 A/g and retention of 80.77% at 10 A/g. Density functional theory (DFT) simulations back up this excellent energy storage capability. This work offers a novel method for manufacturing HEOs and a solid option for supercapacitor anode materials.

Advanced characterization of two novel Fe-rich high entropy alloys developed for laser powder bed fusion in the Al-Co-Cr-Fe-Ni-Zr system

Laser powder bed fusion (LPBF) was used to manufacture two high entropy alloys (HEAs) within the Al-Co-Cr-Fe-Ni-Zr system. The selected compositional ranges were similar to alumina forming austenitic (AFA) steels but omitting interstitials and replacing Nb with Zr as the Laves forming element. The Fe-rich austenitic HEAs were prepared with varying Al and Zr content to evaluate the influence on the presence, size, and distribution of the intermetallic (IM) precipitates. The LPBF process combined with a single (950 °C 6 h) heat treatment formed large, elongated grains with a fine dispersion of multiple different nano-sized IM phases. Synchrotron high energy x-ray diffraction (HEXRD) revealed the cubic M23Zr6 as the main Zr-rich IM phase, stabilized by the multi-element mixture (M=Co, Fe, Ni) and the high cooling rates of the LPBF process. Further HEXRD in-situ compression was performed from room temperature to 900 °C to evaluate the phase stability, thermal expansion, and the strength contribution of the austenitic matrix and the M23Zr6 and NiAl B2 IM phases. The evolution of lattice strain and full width at half maximum of the reflexes was tracked using a statistical model, enabling quantitative analysis along the deformation.

РАСПРЕДЕЛЕНИЕ ХРОМА И ВОЛЬФРАМА В ДИФФУЗИОННОМ СЛОЕ СТАЛИ 35Х2Н3 ПРИ СОВМЕСТНОМ ТЕРМОДИФФУЗИОННОМ НАСЫЩЕНИИ

Chemical-thermal treatment (CHT) of structural parts operating under conditions of wear, friction, shock loads make it possible to obtain a unique combination of surface and core properties of the product. However, such traditional CTO methods as carburizing and nitriding, while improving the mechanical characteristics of the surface, are not suitable for all types of steels. Diffusion metallization methods, in particular, thermal diffusion chromium plating, are more effective in terms of the achieved set of properties. Currently, chromium plating is carried out both by saturation of the metal with one element – chromium, and by multi-element mixtures. The article describes the technology of thermal diffusion saturation of steel X35CrNi2-3 with chromium and tungsten at a temperature of 1000 °С. A technique for analyzing the obtained coating is presented, based on the possibilities of X-ray spectral microanalysis (XMS) of the diffusion layer on transverse microsections of the obtained samples. The elemental composition of the diffusion layer was monitored using a JEOL JSM-6460 LV universal scanning (scanning) electron microscope. The microstructure was studied on an optical metallographic microscope Axio Observer D1.m. X-ray phase analysis was carried out on a Rigaku Ultima IV diffractometer. The hardness measurement was carried out on an FM-800 microhardness tester at a load of 100 g. Data were obtained on the qualitative and quantitative distribution of chromium and tungsten in the surface layer of steel. It is shown that the resulting thermal diffusion coating consists of a substitutional solid solution based on Cr–Fe with a bcc lattice, chromium and tungsten carbides. The depth of the outer coating on the sample was about 20 μm, the depth of the diffusion layer in the base metal was 50–55 μm. The absence of a decarburized area in the surface layer of the base metal was noted. The average diffusion coefficients of chromium in the α-phase of chromium were determined to be DCr = 3,58·10–13 m2/s; in the γ-phase of iron DCr = 2,83·10–15 m2/s. The microhardness of the outer surface layer was 1800–2000 HV, the diffusion layer in the base metal was 1300–550 HV, and the base metal was about 540–510 HV.

Design of dielectric-mode and air-mode slotted photonic crystal nanofiber cavities for refractive index sensing

We propose two different designs of slotted photonic crystal nanofiber cavities (SPCNCs), dielectric-mode (DM) SPCNC and air-mode (AM) SPCNC, and numerically investigate their refractive index sensing performances when they are immersed in an aqueous environment. By using the three-dimensional finite-difference time-domain method, we demonstrate that the DM-SPCNC (AM-SPCNC) simultaneously possesses a high quality factor of 1.49 × 107 (7.96 × 106) and a high sensitivity of 598 nm/refractive index unit (RIU) (423 nm/RIU) at the resonant wavelength of 1525.94 nm (1585.06 nm), yielding a figure of merit as high as 5.8 × 106 RIU−1 (2.1 × 106 RIU−1). Moreover, the mode volume of the DM-SPCNC’s (AM-SPCNC’s) fundamental resonant mode is found to be as small as 0.12 (λ/n)3 (0.24 (λ/n)3), resulting in a very compact effective sensing area. With these distinct features, we believe our proposed cavities are potentially ideal platforms for applications in multiplexed biochemical sensing, multielement mixture detection, and optical trapping of single biomolecules or nanoparticles.

Design and analysis of refractive index sensors based on slotted photonic crystal nanobeam cavities with sidewall gratings.

We propose and numerically investigate a refractive index sensor based on a one-dimensional slotted photonic crystal nanobeam cavity with sidewall gratings for refractive index sensing in a gaseous environment. By using the three-dimensional finite-difference time-domain method, we demonstrate that our proposed sensor simultaneously possesses a high quality factor of $ 3.71 \times {10^6} $3.71×106 and a high sensitivity of 508 nm/RIU (refractive index unit) at the resonant wavelength near 1583 nm, yielding a detection limit as low as $ 1.97 \times {10^{ - 6}} $1.97×10-6 RIU. Moreover, the mode volume of the cavity's fundamental resonant mode is found to be as small as $ 0.022(\lambda /n)^3 $0.022(λ/n)3, resulting in a very compact effective sensing area. We finally study and assess the effect of fabrication disorder on the performances of our proposed sensor. We believe our proposed sensor will be a promising candidate for applications not only in multiplexed biochemical sensing and multielement mixture detection, but also in optical trapping of single biomolecules or nanoparticles.

Column and batch sorption investigations of nickel(II) on extractant-impregnated resin.

Macroporous resin-supported reagents have been identified as potential adsorbents for removal of toxic pollutants. This article presents an experimental designed to evaluate the sorption and desorption of nickel(II) with the help of column and batch procedure using simple extractant-impregnated resin (EIR). Isonitroso-4-methyl-2-pentanone (IMP) as an extractant was impregnated on a solid support like Amberlite XAD-4 to prepare the EIR sorbent. Column experimental conditions such as pH, sample flow rate and volume, eluting solution, and interfering ions were studied to optimize the nickel(II) sorption and recovery from aqueous media. The column results suggest that the quantitative nickel(II) sorption was observed at pH 5-6, and the quantitative recovery (≥ 95%) was achieved by using 1.0 M HNO3. The high concentrations of cations and anions (except EDTA) present in the spiked binary and multi-element mixture solution show no interferences in both quantitative sorption and recovery of nickel(II), whereas the batch experiments were performed to evaluate nickel(II) sorption behavior using the linearized and non-linearized kinetic and isotherm models. By error function analysis, the Freundlich isotherm and the pseudo-first-order kinetic model were found to describe best the experimental data obtained over the studied concentration range and sorption time, respectively. The maximum sorption capacity of nickel(II) onto the EIR sorbent was found to be ~ 81 mg/g. The mean free energy (E = 10.1 kJ/mol) determined using Dubinin-Radushkevich isotherm suggests chemical nature of nickel(II) sorption on EIR. The novelty of the EIR adsorbent lies in its potential for separation and recovery of nickel(II) at trace level in water samples of different origin.

Simultaneously high-Q and high-sensitivity slotted photonic crystal nanofiber cavity for complex refractive index sensing

We proposed and theoretically investigated a one-dimensional slotted photonic crystal nanofiber cavity (SPCNC) for complex refractive index sensing in a gaseous environment. Three-dimensional finite-difference time-domain simulations show that a high quality factor (Q) of 1.45×106 and a high sensitivity of 756 nm/refractive index unit (RIU) can be simultaneously achieved for the detection of the real part of the refractive index (RI) of the surrounding gas. In addition, we demonstrated that the SPCNC possesses the capability of detecting the change of the imaginary part of the RI. A high sensitivity of 1525 nm/RIU is obtained, and Q is found to decrease with increasing absorption strength but still remains as high as 1.1×104 for strong absorption. We believe our proposed SPCNC with excellent sensing performances, ultra-small mode volume, and compact footprint may offer the potential to develop multiplexed sensing techniques for applications in multielement mixture detection.

IPOPv2 online service for the generation of opacity tables

In the framework of the present phase – IPOPv2 – of the international Opacity Project (OP), a new web service has been implemented based on the latest release of the OP opacities. The user may construct online opacity tables to be conveniently included in stellar evolution codes in the format most commonly adopted by stellar physicists, namely the OPAL format. This facility encourages the use and comparison of both the OPAL and OP data sets in applications. The present service allows for the calculation of multi-element mixtures containing the 17 species (H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Cr, Mn, Fe and Ni) considered by the OP, and underpins the latest release of OP opacities. This new service provides tables of Rosseland mean opacites using OP atomic data. We provide an alternative to the OPAL opacity services allowing direct comparison as well as study of the effect of uncertainties in stellar modeling due to mean opacities.

Making low concentration in-house pressed pellet trace element standards for carbonate rock analyses by WD-XRF

We describe a simple method for making in-house, low concentration (0–100ppm) pressed pellet standards for analyzing Ni, Cu, Mo, V and U in carbonate lithologies by wavelength dispersive X-ray fluorescence (WD-XRF) spectrometry. This method can easily be modified to include other elements of interest and to encompass a different range of concentrations. The purpose here was to circumvent the general lack of adequate geological certified reference materials (CRMs) having the necessary concentrations of the above five elements that are commonly used in paleoceanographic studies as proxies for changes in bioproductivity and paleoredox conditions in the water column and near the sediment–water interface. Standards were prepared by spiking 99.999% pure calcium carbonate powder with single element, inductively coupled plasma mass spectrometry (ICP-MS) standard stock solutions to yield final multi-element mixtures containing 0, 1, 2, 5, 10, 20, 50 and 100ppm of Ni, Cu, Mo, V and U, independently verified using acid digestion ICP-MS and PROTrace XRF trace element analyses. The level of in-house standard homogeneity was determined statistically using ANOVA tests (analyses of variance) on count rate data generated for each analyte from three surface transects (50×500μm) ablated on each standard using laser-ablation ICP-MS, demonstrating that all are statistically distinguishable and sufficiently homogenous for the intended purposes of larger spatial scale XRF measurements. The in-house standards were then used to refine preexisting XRF calibrations based on a broad suite of non-carbonate geological CRMs. The refined calibrations yield close agreement with ICP-MS and PROTrace XRF-derived values for the suite of in-house standards when analyzed repeatedly as ‘unknown samples’ by the XRF analytical protocol. The precision of sample preparation and analysis was assessed statistically by ANOVA tests on the results of repeated analyses of analyte concentrations for replicate XRF samples prepared from a representative carbonate sample, yielding reproducibility on the order of 1) <2.5% at the 50–100ppm level, 2) within ±5–10% or better at the 10–20ppm level, 3) within ±5–15% at the 5ppm level, and 4) ±10–55% at the 1–2ppm level which approaches analytical detection limits. Analytical detection limits and residual calibration backgrounds of the XRF protocol were constrained empirically by repeated analyses of ultrapure calcite blanks.

Alloying behavior of iron, gold and silver in AlCoCrCuNi-based equimolar high-entropy alloys

High-entropy alloys are newly developed alloys that are composed, by definition, of at least five principal elements with concentrations in the range of 5–35 at.%. Therefore, the alloying behavior of any given principal element is significantly affected by all the other principal elements present. In order to elucidate this further, the influence of iron, silver and gold addition on the microstructure and hardness of AlCoCrCuNi-based equimolar alloys has been examined. The as-cast AlCoCrCuNi base alloy is found to have a dendritic structure, of which only solid solution FCC and BCC phases can be observed. The BCC dendrite has a chemical composition close to that of the nominal alloy, with a deficiency in copper however, which is found to segregate and form a FCC Cu-rich interdendrite. The microstructure of the iron containing alloys is similar to that of the base alloy. It is found that both of these aforementioned alloys have hardnesses of about 420 HV, which is equated to their similar microstructures. The as-cast ingot forms two layers of distinct composition with the addition of silver. These layers, which are gold and silver in color, are determined to have a hypoeutectic Ag–Cu composition and a multielement mixture of the other principal elements, respectively. This indicates the chemical incompatibility of silver with the other principal elements. The hardnesses of the gold (104 HV) and silver layers (451 HV) are the lowest and highest of the alloy systems studied. This is attributed to the hypoeutectic Ag–Cu composition of the former and the reduced copper content of the latter. Only multielement mixtures, i.e. without copper segregation, form in the gold containing alloy. Thus, it may be said that gold acts as a ‘mixing agent’ between copper and the other elements. Although several of the atom pairs in the gold containing alloy have positive enthalpies, thermodynamic considerations show that the high entropy contribution is sufficient to counterbalance these positive enthalpies, and permit effective mixing. The considerably higher positive enthalpies between the elements of the silver alloy, however, are too great to be counterbalanced by the entropy. This work highlights the importance of the entropy contribution and mixing enthalpy between atom pairs, i.e. bonding energy, on the structural evolution and related properties of high-entropy alloys, and provides essential information for the future development of this new breed of alloy system.

Extraction and Recovery of Zirconium from Zircon Using Cyanex 923

A liquid–liquid extraction study has been carried out to recover pure zirconium from zircon using 0.1 mol/L Cyanex 923 solution in toluene. Some of the parameters influencing the percentage extraction of Zr(IV), such as equilibration time, temperature, and concentration of mineral acid, extractant, and metal ion were investigated. Apparently the rate of extraction of Zr(IV) in Cyanex 923 is reasonably fast. The distribution increases with increasing temperature, suggesting that the reaction is endothermic. The distribution ratio of Zr(IV) is independent of the metal ion concentration in the range 1×10−4 to 8.5×10−4 mol/L, beyond which loading conditions begin. The stoichiometry of the extracted species is observed to be 1:1 (metal to extractant). The stability of Cyanex 923 against prolonged contact with nitric acid has been checked and the regeneration capacity of the extractant solution assessed. Based on the distribution data, Zr(IV) has been separated from some commonly associated metal ions, namely U(VI), Th(IV), Ti(IV), Ce(III), Yb(III), Fe(III), Al(III), and Mn(II). The identified conditions of separation have been successfully utilized to recover pure Zr(IV) from multielement mixtures.

Theoretical Study of the Opacity for Mixture Materials at HighTemperatures

Using a detailed configuration accounting model with term structurestreated by the unresolved transition array model, we have extensively investigatedthe opacities of mixture materials. For plasmas at the temperature of 250 eV anddensity of 1 g/cm3, our calculated Rosseland mean opacities are in good agreementwith other theoretical results. A high increase in the Rosseland mean opacity to2944 cm2/g is achieved for a multi-element mixture compared to the value of1729 cm2/g for pure gold. Various mixtures at other plasma conditions are also studied.

A New Ferroelectric Varactor From Water Based Inorganic Precursors

AbstractSolution deposition processes for the production of thin multi-element metal oxide films continue with great interest and varied success. Solution deposition via either sol-gel or MOD (Metal Organic Decomposition) methods are of interest due to the ability to produce a wide variety of compositional products at low capital investment cost. The sol-gel method generally uses hydrolytically sensitive metal alkoxides as the starting materials. Manipulation of the reagents and different hydrolysis rates for multi-element mixtures are issues. The MOD method utilizes large organic acid metal salts as the starting materials. In general, MOD solutions are more hydrolytically stable than the sol-gel solutions. MOD process challenges include large quantities of carbon to be decomposed during the firing, shrinkage and stress of the thin films, variable chemistry in synthesis of the starting materials (especially when the starting materials for the MOD precursors are metal alkoxides), and long reaction times for the synthesis. For both the sol-gel and MOD precursors, toxic and volatile organic chemical (VOC's) solvents are employed as the vehicle.This paper will review the chemistry-related issues to production of consistent highquality metal oxide films via the MOD process. The fabrication of thin BaxSr(1-x)TiO3 (BST) films is described. A new class of MOD precursor has been implemented using polyether acids as the organic vehicle. These new materials are both water stable and water soluble. High quality BST thin films made from these precursors are described and capacitors made from these films are compared to the aliphatic acid MOD materials. Improved capacitors using lower resistance electrodes and interconnects are described, as well as devices designed specifically for our specific application.

Synthesis of water soluble precursors for ferroelectric materials

Solution deposition processes for the production of thin multi-element metal oxide films continue with great interest and varied success. Solution deposition via either sol-gel or MOD (Metal Organic Decomposition) methods are of interest due to the ability to produce a wide variety of compositional products at low capital investment cost. The sol-gel method generally uses hydrolytically sensitive metal alkoxides as the starting materials. Manipulation of the reagents and different hydrolysis rates for multi-element mixtures are issues. The MOD method utilizes large organic acid metal salts as the starting materials. In general, MOD solutions are more hydrolytically stable than the sol-gel solutions. MOD process challenges include large quantities of carbon to be decomposed during the firing, variable chemistry in synthesis of the starting materials (especially when the starting materials for the MOD precursors are metal alkoxides), and long reaction times for the synthesis. For both the current state of the art sol-gel and MOD precursors, toxic and volatile solvents are employed as the vehicle. This paper will review the chemistry related issues to production of consistent high quality metal oxide films via the MOD process. The solid solution BaxSr(1-x)TiO3 will be used as an example. A new technique to quickly obtain controlled carbon content MOD precursor solutions from available starting materials is described. Several new water stable and water soluble BST precursors are described. Details of the electrical properties of capacitors made from the new water based precursors are shown.

Comparison of the retention behaviour of uranium and thorium on high-efficiency resin substrates impregnated or dynamically coated with metal chelating compounds

A study of the separation of trace uranium from multi element mixtures using high-performance chelating ion chromatography (HPCIC) is described. Three different chelating columns were compared in the investigations and the results are discussed. Two types of neutral polystyrene substrates were used for forming the chelating surfaces, a hypercrosslinked macronet and a standard low crosslinked polymer. Calmagite, 4-(2-pyridyl) azoresorcinol (PAR) and dipicolinic acid were the chelating compounds selected to impregnate or coat the resins. One unusual finding was the different retention orders for uranium(VI) and thorium(IV) on the three columns. The best separation of uranium(VI) was obtained on the macronet resin dynamically coated with dipicolinic acid. The column gave a uranium peak of good symmetry well separated from thorium(IV), lanthanum(III) and iron(II). The reproducibility of retention and quantitative performance for uranium(VI) was evaluated using arsenazo III post-column reaction detection.

Silica Gel-Bonded Cationic Polyelectrolyte with Ferron as Counterion. Application to Preconcentration or Elimination of Trace Metals

Abstract An integral N-based cationic polymer, poly[N-xylylene N,N′-dicyclohexylethylenediammonium dibromide], was immobilized through hydrogen bonding on the surface of silica gel. The chelating ligand, 7-iodo-8-hydroxyquinolino 5-sulfonic acid (Ferron), was subsequently attached to the matrix by ion-exchange method; this renders an extremely stable stationary phase, free from leaching complications, under electrostatic (salt) bond interactions. Analytical characteristics of this sorbent were studied. The optimum sorption conditions for Cu2+, Cd2+, Zn2+, Pb2+, Co2+, Ni2+, and Fe3+ under static and dynamic (column) methods were ascertained. The chelator was found to be selective for the retention of Cu2+, Pb2+, and Fe3+ from multi-element mixtures. The relatively fast kinetics of the sorbent with the time required to reach half of the maximum sorption (t1/2 value 2 min) and the percentage attainment of equilibrium in 2 min (P2 min value &amp;gt; 50%) for most of the heavy metals, excluding Ni2+, reveal the suitability of the chelating resin in column operation, especially in single column ion-chromatography. The specific applications of the sorbent in purification of supporting electrolyte/buffers required for voltammetric detection are also explored.

Correlation-based detection of spectral information using microliter volumes, in-torch vaporization (ITV) sample introduction and inductively coupled plasma atomic emission spectrometry with photodiode array detection

The application of Fourier transform-based cross-correlation techniques for automatic detection of spectral information using 10 μl volumes is presented. The basic approach involves interrogation of a spectral pattern from a multielement mixture for the presence of spectral features obtained by running single element standard(s). In essence, the multielement mixture is “interrogated” for the presence of the sought-for element and, thus, automatic interpretation of spectral information is obtained. Spectral patterns from 10 μl volumes of single element standards and multielement mixtures were acquired using an electrically heated wire-loop, in-torch vaporization (ITV) sample introduction system and an inductively coupled plasma (ICP) spectrometer equipped with a photodiode array detector (Leco Plasmarray). The wavelength region from about 280 nm to about 410 nm was covered. Spectral patterns for 10 elements (Al, Be, Co, Ni, Sc, Sr, V, Y, Yb and Zr) obtained using 10 μl volumes of single element standards were converted to spectral interference-free and noise-free binary software masks. Cross-correlation of these binary software masks with spectral patterns obtained from 10 μl volumes of multielement mixtures is discussed and a graphical user interface that utilizes a color-coded periodic table to present the likely composition (i.e. qualitative and semi-quantitative analysis) of a mixture on the computer screen is described.

Separation and quantitation of some metal ions by RP-HPLC using EDTA as complexing agent in mobile phase

Ion pair reversed-phase high performance liquid chromatography has been used to achieve the simultaneous separation of some transition metal ions including Ni(II), Co(II), Cu(II), Mn(II), Fe(III), Pb(II), Cr(III), and Hg(II) as complexes of ethylenediaminetetraacetic acid (EDTA) originated, in the column itself. Due to the negative charge of the metal complexes, the separation of metal ions from inorganic anions such as Cr2O72− and NO3− is possible by employing a positively charged counterion in the mobile phase. The influence of the nature and concentration of counterion, organic modifier content, ionic strength, EDTA concentration and pH of the mobile phase on the retention and selectivity has been investigated. Quantitation of metal ions was achieved with spectrophotometric detection. Detection limits ranged from 300 pg for Fe(III) to 35 ng for Cr(III) with a linearity of 2–3 orders of magnitude. Some applications of the technique to the separation of multielement mixtures are shown.

A Comparison of Mineral Extraction Techniques of Citrus Juices as Analyzed by Inductively Coupled Plasma Atomic Emission Spectrometry

ABSTRACTTwo methods of mineral extraction for citrus juices were investigated: dry ashing in a muffle furnace and wet ashing in a microwave oven. Elemental concentrations were determined by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP‐AES). For reference, a synthetic multielement mixture was prepared and analyzed. Results for the multielement solution using wet ashing in a microwave oven or dry ashing in a muffle furnace differed by less than 10% from those for an undigested, but diluted solution. An exception was boron, of which 96% was lost in the muffle furnace. Grapefruit juice analysis showed differences in concentration of less than 10% for all elements. Orange juice samples, however, showed greater losses for Na (16%), Si (13%), and Sn (11%) with the dry ashing method.

A data bank for high pressure vapour—liquid equilibria

The Berlin Thermodynamics Data Bank (die Berliner Datenbank Thermodynamik, BDBT) records experimental data on high pressure vapour—liquid equilibria of binary, ternary and multi-element mixtures. The information contained in the data bank is useful for several purposes:(1) as a reference for process design;(2) as a basis for fitting binary parameters in correlations;(3) as a data file for checking the accuracy of correlations.The structure of the data bank, the fitting procedures for binary parameters and the tabular or graphical representation of the comparison of calculated and experimental data are shown and discussed. The Data Bank is available from the INKA (Informations-System Karlsruhe), from Dechema, Frankfurt, and from FIZ Chemie, West Berlin. Part of the BDBT has been published in the Dechema Data Series.