Spinel Solid Solution Research Articles

High Voltage Mg-Ion Battery Cathode via a Solid Solution Cr–Mn Spinel Oxide

Lattice Mg2+ in a tailored solid solution spinel, MgCrMnO4, is electrochemically utilized at high Mn-redox potentials in a nonaqueous electrolyte. Complementary evidence from experimental and theor...

Phase Equilibrium Study of the CaO-SiO2-MgO-Al2O3-TiO2 System at 1300\xb0C and 1400\xb0C in Air

Due to the importance of the physicochemical properties of slag in the recovery of low-titanium ores and by-products, the equilibrium phase relationships of the CaO-MgO-Al2O3-SiO2-TiO2 system were experimentally determined using a high-temperature equilibration and quenching method at 1300°C and 1400°C. The equilibrium information was obtained by scanning electron microscope–energy dispersive x-ray spectrometer. Perovskite, spinel and pseudobrookite solid solution phases with MgO·2TiO2 and Al2O3·TiO2 end members were found to be coexisting with the liquid phase. The 1300°C and 1400°C isotherms were then constructed on a CaO-SiO2-TiO2-8 wt.% MgO-14 wt.% Al2O3 quasi-ternary section. Comparisons with predictions by Factsage and MTDATA indicated that the computational results agreed well only in the primary phase field of perovskite, while clear deviations existed within other primary phase fields. Therefore, the present results improve our knowledge about the utilization of titanium resources, and are also significant in providing novel equilibrium data for updating the related thermodynamic databases.

Patterns in the synthesis processes and the characteristics of silicate-spinal ceramic pigments when introducing mineralizers

The synthesis of ceramic pigments is conventionally carried out at a high temperature (not less than 1,200 °C). Its reduction implies using mineralizing additives, which have a different mechanism of action on the starting components of pigment charges. The effectiveness of the mineralizers is determined by their nature, content, degree of dispersion in the activated reagent. Thus, searching for the most effective mineralizers in the synthesis, in particular, of silicate-spinel ceramic pigments is an important scientific and practical task.We have investigated the effect of various mineralizing additives (B2O3, Na2B4O7, Na2O, NaF) on the processes of forming the crystal-phase composition of slag-containing ceramic pigments and the change in their color indicators. A direct dependence has been established between the melting point of the mineralizers and the efficiency of their influence on the formation of spinel phases, which are color carriers in such pigments. The tangible effect of the introduction of sodium fluoride, which has the highest melting point among the examined additives, is achieved as a result of the firing of pigments at a temperature not lower than 1,150 °C. The effect of sodium oxide is effective starting at a temperature of 1,100 °C. The most expedient to apply are the boron-containing compounds. Their introduction makes it possible to lower the firing temperature of slag-containing pigments to 1,050 °C while completely binding the starting components in the spinel solid solutions. The ceramic pigments that are thus synthesized enable the formation of glazed coatings, which, in terms of qualitative indicators, are not inferior to coatings obtained with the addition of high-temperature pigments (a firing temperature of 1,200–1,250 °С). The formation of silicate phases (diopside and wollastonite), which are not color carriers in the examined pigments, undergoes effective mineralized action from the supplements of NaF and B2O3

Synthesis and Polymorphism of Mixed Aluminum-Gallium Oxides.

The synthesis of a new solid solution of the oxyhydroxide Ga5–xAlxO7(OH) is investigated via solvothermal reaction between gallium acetylacetonate and aluminum isopropoxide in 1,4-butanediol at 240 °C. A limited compositional range of 0 ≤ x ≤ 1.5 is produced, with the hexagonal unit cell parameters refined from powder X-ray diffraction (XRD) showing a linear contraction in unit cell volume with an increase in Al content. Solid-state 27Al and 71Ga nuclear magnetic resonance (NMR) spectroscopies show a strong preference for Ga to occupy the tetrahedral sites and Al to occupy the octahedral sites. Using isopropanol as the solvent, γ-Ga2–xAlxO3 defect spinel solid solutions with x ≤ 1.8 can be prepared at 240 °C in 24 h. These materials are nanocrystalline, as evidenced by their broad diffraction profiles; however, the refined cubic lattice parameter shows a linear relationship with the Ga:Al content, and solid-state NMR spectroscopy again shows a preference for Al to occupy the octahedral sites. Thermal decomposition of Ga5–xAlxO7(OH) occurs via poorly ordered materials that resemble ε-Ga2–xAlxO3 and κ-Ga2–xAlxO3, but γ-Ga2–xAlxO3 transforms above 750 °C to monoclinic β-Ga2–xAlxO3 for 0 ≤ x ≤ 1.3 and to hexagonal α-Ga2–xAlxO3 for x = 1.8, with intermediate compositions of 1.3 < x < 1.8 giving mixtures of the α- and β-polymorphs. Solid-state NMR spectroscopy shows only the expected octahedral Al for α-Ga2–xAlxO3, and for β-Ga2–xAlxO3, the ∼1:2 tetrahedral:octahedral Al ratio is in good agreement with the results of Rietveld analysis of the average structures against powder XRD data. Relative energies calculated by periodic density functional theory confirm that there is an ∼5.2 kJ mol–1 penalty for tetrahedral rather than octahedral Al in Ga5–xAlxO7(OH), whereas this penalty is much smaller (∼2.0 kJ mol–1) for β-Ga2–xAlxO3, in good qualitative agreement with the experimental NMR spectra.

Newborn screening for Morquio syndrome: Results from the 8-plex assay for 70,000 newborns

Cu-Ni-Al ternary spinel solid solution catalysts with different Al content are prepared by the solid-phase ball milling method. The characterizations with XRD, H2-TPR, BET and XPS, and catalytic performance testing are carried out to study the effects of Al content on the physicochemical properties of the Cu-Ni-Al spinels and their sustained release catalytic performances in methanol steam reforming for hydrogen production. Characterization results show a significant increase in the specific surface area and pore volume of the catalysts with increasing the Al content (Al = 2, 3, 4) at a constant Cu/Ni molar ratio of 0.95:0.05. At the same time, both the cell parameters and crystallite sizes of Cu-Ni-Al spinel solid solutions decrease, and the catalysts become difficult to be reduced. Furthermore, the content of spinel Ni2+ increases slightly while the spinel Cu2+ decreases significantly, leading to a declined total content of spinel Cu2+ plus Ni2+. The results also indicate that the presence of Ni2+ inhibits the formation of spinel Cu2+. Surface analysis results show that the increase of Al content transforms the catalyst surface composition from Cu-rich to Al-rich, and the surface spinel Cu2+ decreases, but it is still higher than the spinel bulk. The catalyst testing results show that as the Al content in the catalysts increases, the initial activity increases notably, and the CO selectivity decreases, but too much Al results in an inferior catalytic stability. In general, the catalyst with an Al = 3 shows a better catalytic performance in terms of activity and stability. The results of this paper demonstrate that there is an optimal Al content for the Cu-Ni-Al spinel solid solutions used as the sustained release catalysts, playing a crucial role in obtaining high catalytic stability.

Effect of Mn Content on the Characteristics of Inclusions in Ti-Containing Steel Welds

Steel weld metals containing Ti were prepared with Mn contents of 0.35%–2.98%. The inclusion characteristics in the weld metals were investigated by means of thermodynamic calculations coupled with electron probe microanalyses and transmission electron microscopy. The results show that with an increase in Mn content, the primary constituent phases of the inclusions are changed from pseudobrookite to a combination of pseudobrookite and spinel and eventually to a mixture of (Mn–Si–Al)-oxide, spinel and ilmenite. Ti3O5, MnTi2O4 and MnTiO3 are the primary constituents of the pseudobrookite, spinel and ilmenite solid solutions, respectively. Spinel and ilmenite have higher amounts of Mn but lower amounts of Ti compared with that of pseudobrookite. The formation of large amounts of ilmenite and spinel leads to the development of a Mn-depleted zone (MDZ) in the vicinity of the matrix/inclusion interface. Acicular ferrite has a Baker–Nutting orientation relationship with MnTi2O4.

Co-stabilization of Pb/Cu/Zn by beneficial utilization of sewage sludge incineration ash: Effects of heavy metal type and content

The release and migration of heavy metals from the industrial sludge has become one of the most serious environmental threats, which is urgently required to be relieved. Heavy metals can be stabilized by using ceramic precursors, via interactions with aluminum (Al), silicon (Si) and iron (Fe) as the major components. The sewage sludge incineration ash (SSA) can be recognized as a type of ceramic raw materials due to the abundant content of Al, Si and Fe, which make it possible to be beneficially used for heavy metal stabilization. This study investigated the stabilization of lead (Pb), zinc (Zn), and copper (Cu) after ceramic sintering with the SSA as ceramic precursors, and further explored the influences of heavy metal types and contents on phase transformation and immobilization effect. Results show that the heavy metals could achieve co-stabilization by the SSA in reaction series with different metal types and contents (Pb-Zn and Pb-Cu). Pb tends to combine with Al, Si and P to form PbAl2Si2O8 and Pb3(PO4)3, while Zn was finally incorporated into a spinel solid solution (ZnFexAl2-xO4). Meanwhile, Cu is more likely to combine with Fe with the generation of CuFe2O4 which will be transformed to CuFeO2 with elevated temperatures. In both Pb-Zn and Pb-Cu series, the Zn and Cu were distributed in crystal grains while Pb was in regions around the grains. Moreover, the leachability of Pb, Zn and Cu can be substantially decreased with the eventual incorporation of the heavy metals into different product phases by the SSA. Therefore, through this study the coimmobilization of heavy metals in the simulated industrial waste can be realized by the utilization of sewage sludge incineration ash as ceramic precursors.

Color modulation by selective excitation activated defects and complex cation distribution in Zn1-xMgxAl2O4 nanocrystals.

Complex cation distribution in spinel solid solution, fosters defect generation and permutates the optical properties. To scrutinize the effect on structural properties, viz. the cation distribution and defect states upon substitution of Zn with Mg; and to tune the emission properties, Zn1-xMgxAl2O4 (0.01 ≤ x ≤ 0.30) nanocrystals are synthesized. The nanocrystals show increased inversion and generation of multiple defects, namely zinc vacancies, zinc interstitials, oxygen vacancies and antisite defects with increasing Mg content, which thereby impacts the optical band gap. Pentahedral coordination in addition to tetra- and octahedral coordination of Al has been observed, which infers the presence of oxygen vacancies and dangling bonds. Moire fringes formation has intimated the presence of two or more crystal lattices with higher Mg substitution. Band-to-band and defect-assisted photoluminescence shows the role of multiple defects, especially defect clusters, in deciphering the properties of the resulting crystals. Color change from bluish-white to pink has been achieved depending upon the excitation wavelength and emission mechanism, as proposed through a band model schematic. The presented study may be beneficial for designing the Zn1-xMgxAl2O4 nanocrystals with optimized emission properties.

Multicomponent Spinel Oxide Solid Solutions: A Possible Alternative to Platinum Group Metal Three-Way Catalysts

Single-phase quaternary spinel solid solutions, Cu0.05Ni0.95AlyCr2–yO4 (0 ≤ y ≤ 2.0), were prepared over the whole range of y by a polymerized complex method to study as platinum group metal-free three-way catalysts (TWC). Most conventional binary and/or ternary spinel oxides lose their NO reduction activity in the presence of water vapor and/or after high-temperature aging. In contrast, the present quaternary system with y = 1.8, which was aged at 900 °C for 25 h, preserved high activity even under a wet gas stream (5% H2O) simulating real TWC conditions. Comprehensive structural analyses via X-ray absorption fine structure and X-ray Rietveld analysis showed that, in the quaternary system, Cu and Cr prefer to occupy the tetrahedral site and the octahedral site, respectively, whereas Ni and Al are distributed across both sites. The partial replacement of Cr by Al increased the specific surface area from 7 m2 g–1 (y = 0) to 36 m2 g–1 (y = 1.8), which is a common feature of the NiAl2O4-based spinel platform...

Solid State Synthesis and Reversible Oxygen Capacity of Li/Mg Overstoichiometric Solid Solutions Based on the Spinel MgMnO3 – δ

Series of spinel solid solutions with a specified cation composition, Mg1 +xMnO3 – δ and, for the first time, MgLixMnO3 – δ, potential materials of catalytic systems for oxidation reactions such as oxidative conversion of methane and chemical looping combustion process were prepared by solid-state syntheses from mechanocomposites obtained by milling of ultra-high purity precursors (MgO, Mn2O3, MnO2, and Li2CO3). Their homogeneity region was found to be up to 1573 K at p(O2) = 0.21 atm. For both series of solid solutions, the synthesis from Mn2O3 and MnO2 in air was investigated by the TG-DSC method and the oxygen content in the resulting materials was determined (TG-DSC, titration). The products of extensive reduction of spinels Mg1 +xMnO3 – δ and MgLixMnO3–δ with an Ar + 4.8% H2 mixture were investigated. Parameters of conversion of the reduction products to the initial single-phase spinels on treatment with air were determined. The obtained materials showed good reproducibility of reversible oxygen capacity over 20 reduction–oxidation cycles.

Research on Corrosion Resistance of Al2O3-MgAl2O4 Refractories and SiC-MgAl2O4 Refractories to Gasifier Slag

Spinel-containing refractory is a kind of potential chromium-free refractory for coal gasification because MgAl2O4 spinel has good slag resistance. Corundum-spinel refractories with w(Al2O3)=94%, w(MgO)=5% and SiC-spinel refractories with w(SiC)=64%, w (Al2O3)=5% were prepared. The crucible specimens were tested for slag corrosion with commercial gasifier slag at 1 500°C for 1 h in reducing atmosphere. XRD analysis were researched on the sidewall of the crucible after slag test. Microstructure and chemical composition of samples in slag corrosion zone were analyzed by SEM and EDS. The results show that the slag resistance of SiC-MgAl2O4 refractory was significantly better than Al2O3-MgAl2O4 refractory. The corundum particles were decomposed into fine particles by the slag, and the microstructure was destroyed. The oxidation of the surface of the silicon carbide particles formed a high-viscosity glass phase with the infiltrated slag, which was benefit to prevent the slag penetration into the interior. And a solid solution of (Mg, Fe)O·Al2O3 composite spinel was formed in matrix of the sample after slag penetration because MgAl2O4 absorbed FeO in the slag. It is speculated that the spinel solid solution repairs and strengthens the structure of the matrix, which improves the slag resistance.

Critical evaluation and thermodynamic modeling of the Fe–V–O (FeO–Fe2O3–VO–V2O3–VO2–V2O5) system

Critical evaluation and optimization of the Fe–V–O ternary oxide system was carried out based on all the available phase equilibria and thermodynamic property data at 1 atm total pressure. The Fe3O4–FeV2O4 spinel solid solution was described within the framework of Compound Energy Formalism considering the cation distribution between tetrahedral and octahedral sites. The wüstite phase, corundum phase, and VO2 solid solution were described using a simple random mixing model. The Modified Quasichemical Model was used to describe liquid oxide solution in consideration of all multivalence states of Fe and V (Fe2+, Fe3+, V2+, V3+, V4+ and V5+). The variation of phase equilibria depending on the oxygen partial pressures and thermodynamic data in the system were well reproduced in the present study.

Thermodynamic optimization of the Al2O3–FeO–Fe2O3–SiO2 oxide system

A complete literature review, critical assessment, and thermodynamic modeling of the phase diagrams and thermodynamic properties of oxide phases in the Al2O3–FeO–Fe2O3–SiO2 system at a total pressure of 1 atm are presented. A set of optimized model parameters for all phases was obtained to reproduce all previously published thermodynamic and phase equilibrium data. Some discrepancies in the literature data were identified, particularly for liquidus measurements and the Fe3+/(Fe2+ + Fe3+) ratio in the slag phase (liquid oxide phase) at high temperatures. Analysis of internal consistency with the Al2O3–FeO–Fe2O3, FeO–Fe2O3–SiO2 and Al2O3–SiO2 sub-systems allowed to resolve the discrepancies. Previously published model parameters for the slag phase in the Al2O3–FeO–Fe2O3 system were slightly modified to achieve better overall agreement. The final set of model parameters for oxide phases reproduces all available data within experimental error limits. The Modified Quasichemical Model was used for modeling of the slag phase. The models based on the Compound Energy Formalism were applied for spinel and mullite solid oxide solutions. The database of model parameters optimized in the present study can be used along with software for Gibbs energy minimization to describe thermodynamic equilibria at all compositions and oxygen partial pressures, from the lowest corresponding to equilibrium with metal up to the highest P(O2) of 1 atm. The database was incorporated into the larger database for the multi-component Al–Ca–Cu–Fe–Mg–Pb–Zn–O–S–Si–(As, Sb, Bi, Sn, Ag, Au, Ni) chemical system and successfully used for calculations of equilibria relevant to copper, lead, zinc smelting and recycling.

Sewage sludge incineration ash for coimmobilization of lead, zinc and copper: Mechanisms of metal incorporation and competition

Heavy metals such as lead, zinc, and copper always coexist in industrial wastes and tend to be released if the wastes are not treated properly. With abundant contents of aluminum, iron and silicon, sewage sludge incineration ash can provide a ceramic matrix for potential heavy metal stabilization. By using ceramic sintering, this study explored the coimmobilization mechanisms of lead, zinc and copper, with detailed explications on phase transformation, metal distribution and the effect of metal content. PbAl2Si2O8 was identified as the major phase for lead immobilization in series with low heavy metal content, while most of the lead was incorporated into Pb9(PO4)6 in high metal series. The ZnxCu1-xFeyAl2-yO4 spinel solid solution was the predominant product phase for copper and zinc stabilization in both reaction series, but zinc was more competitively incorporated into the spinel structure. Moreover, the pattern of heavy metal distribution in the sintered products was largely affected by the metal type and elemental composition of the reaction system. Although different leaching behaviors were observed for the three heavy metals, their leachability was found to reach very low value after the thermal treatment processes. This study proposed a “waste-to-resource” strategy to largely alleviate the environmental burden of solid wastes and heavy metal pollution by using sewage sludge incineration ash as raw materials for low-temperature glass-ceramics, with a simultaneous effect on metal immobilization.

Post-annealing effect on transparent Mg-Zn aluminate solid solutions fabricated by spark plasma sintering

In MgAl2O4 (Mg aluminate) fabricated by pressure sintering, carbon contamination, oxygen vacancy, and other defects exist and cannot be completely removed even after post-annealing. ZnAl2O4 (Zn aluminate) has the same crystallographic structure as Mg aluminate and excellent light transmission by post-annealing. In this study, the transmission of (Mg1-XZnX)Al2O4 spinel, which is a solid solution between Mg aluminate and Zn aluminate, was investigated. After post-annealing, the transmission of (Mg1-XZnX)Al2O4 spinel was higher than Zn aluminate and Mg aluminate, which means that the absorption center disappeared. Besides, the real in-line transmission is improved by up to 30% by post-annealing, which is related to the driving force to increase the configurational entropy and form a more stable solid solution phase. In solid solution spinel, as the Zn content increases, the optical properties can be improved by post-annealing, but the mechanical properties are slightly decreased.

Broad band emission near-infrared material Mg3Ga2GeO8:Cr3+: Substitution of Ga-In, structural modification, luminescence property and application for high efficiency LED

Series of Cr3+ doped Mg3Ga2GeO8 magnesium gallogermanate near-infrared (NIR) materials were synthesized by solid state method. Mg3Ga2GeO8 with a spinel solid solution structure can provide three different sites for Cr3+, and the priority of Cr3+ entering the three sites has been clearly determined by analyzing the distortions of the three polyhedral sites and local crystal field strength. The emission of the phonon vibration line from the non-forbidden transition 2E→4A2 is observed at T = 10k in sub-peak 1, however, at room temperature, the spectrum presents a broad emission band 700–1200 nm superimposed on 2E→4A2 emission. When introduced In3+ into Mg3Ga2GeO8 to substitute for Ga3+, the emission intensity can be greatly enhanced and a red shift of emission spectra is observed, which may be ascribed to the crystal field environment getting weakened with increasing In3+. A novel NIR phosphor converted light emitting diode was fabricated by combining Mg3Ga1.87In0.1GeO8:0.03Cr3+ with 455 nm blue chip, of which an optical power is 6.143 mW, a photoelectric efficiency is 8.5%, importantly, the spectrum range of device covers 650–1200 nm with a full width at half maximum (FWHM) of 244 nm.

Thermodynamics and kinetics of FeO transferred to Fe3O4 in modified nickel slag during molten oxidation process

In view of the utilization of iron resources in nickel slag, water-quenched nickel slag from flash furnace was treated by using a molten oxidation method. During this process, the iron components in the nickel slag were melted and oxidized, finally transferred to magnetite phases (Fe3O4). In this paper, the thermodynamic analysis and calculation of the Fe-containing phase evolution during the molten oxidation process were carried out, the transfermation possibility of iron component as magnetite phase was analyzed, and the kinetics of FeO transfermation to Fe3O4 in modified nickel slag during molten oxidation process was studied. The study results show that the use of CaO in oxidizing process favors the decomposition of fayalite phase and formation of magnetite phase. The Fe3O4 spinel solid solution precipitated from the CaO-FeO-MgO-SiO2 system under the conditions of slag basicity of 0.90 and oxygen partial pressure of 0.21 atm. With the extension of oxidizing time, FeO transferred to Fe3O4 in modified nickel slag during molten oxidation process. The magnetite crystals gradually change from fine dendritic shape to granular shape at lower oxidizing temperature. But dendrites exist during the oxidization at the higher oxidizing temperature. The formation rate constant and apparent activation energy of magnetite crystals is calculated to be 0.0183 and 68.17 kJ mol−1, respectively.

Thermodynamics of ZnxMn3−xO4 and Mg1−zCuzCr2O4 spinel solid solutions

Abstract

Effects of ZnO addition on the sintering behavior and mechanical properties of magnesium aluminate spinel ceramics

AbstractThis article discusses the successful preparation of high‐strength solid solution spinel ceramics via a solid‐state reaction sintering process employing MgAl2O4. The effects of ZnO content on the sintering behavior, bulk density, apparent porosity, phase composition, microstructure, cold modulus of rupture, and modulus of elasticity of the MgAl2O4‐based ceramics are investigated. The results show that the formed MgAl2O4‐based ceramics represent an MgAl2O4–ZnO solid solution, which markedly improves the sinterability, densification, and mechanical properties of the pure MgAl2O4 ceramic and decreases the sintering activation energy.

Wear mechanism of a novel Al Si MgAl2O4Al2O3 composite used in the low vessel of an RH secondary refining furnace

Abstract A novel Al Si MgAl2O4 Al2O3 composite brick was prepared and evaluated in the low vessel of an RH (the initials of Ruhrstahl and Hereaeus) secondary refining furnace; it was characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The results show that after use, the Al Si MgAl2O4 Al2O3 composite has a functional gradient with an erosion zone–reinforced zone–original zone phase distribution, in which the phases in the erosion zone (0–1.8 cm) are a Mg-hercynite spinel solid solution, α-Al2O3, and minor amount of Al3Fe5O12. Furthermore, the phases in the reinforced zone (1.8–5.0 cm) are γ-AlON, 21R SiAlON, SiC, Mg0.388Al2.408O4, and α-Al2O3; i.e., the Al and Si in the composite are completely converted into non-oxide reinforced phases. Finally, the phases in the original zone (>5.0 cm) show no change. The reaction mechanism is as follows. During operation, a Mg-hercynite spinel solid solution is formed in the erosion zone due to a reaction between MgAl2O4 and FeO from a refinery operation. Therefore, the slag erosion of the material is improved. The Al and Si metals undergo active oxidation, and 21R SiAlON flakes are subsequently formed from the products of the metastable Al2O(g), SiO(g), and N2(g) in the ambient. The γ-AlON is formed by a carbothermal reduction nitridation of the α-Al2O3 and residual active carbon from the resin binder. The 21R SiAlON and γ-AlON reinforce the composite brick and improve its high temperature performance accordingly. Its service life is 110% that of the magnesia-chrome bricks used in the same period. The reaction model was also established.