Multicomponent Oxide Research Articles

Zeolite-induced defect engineering for synthesis of CuBTC-derived novel carbon-zeolite bifunctional support catalyst for multicomponent VOCs catalytic oxidation removal

In this study, a novel carbon-zeolite hybrid supported Cu catalyst (CuC@NaY) was facilely fabricated by zeolite-induced CuBTC self-assembled growth. The CuC@NaY-3 had a homogeneous spongy nanocage structure, coupled with rich active centers and most oxygen vacancy defects, making it have improved catalytic activity, multi-pollutant adaptability, as well as superior robustness and stability for practical applications. Proper volume of acetone enhanced the catalytic oxidation of toluene on CuC@NaY-3. The T90 for toluene and acetone mono-component catalytic oxidation on CuC@NaY-3 were 265.0 and 214.0 °C, respectively. Whereas for toluene/acetone mixture oxidation, due to the generated enol functional group (−o–) of acetone oxidation the T90 of toluene was reduced to 260.5 °C. The CuC@NaY-3 has also exhibited better water resistance and stability in the catalytic oxidation of toluene/acetone mixture. The DFT calculation proved that CuO led to a more pronounced activity in mono-component oxidation, while Cu2O played a facilitating role when the two pollutants co-exist.

Liquidus temperatures in the La2O3-SrO-TiO2-ZrO2-Fe2O3 system: Calculation and experiment

Ceramics based on the La2O3-SrO-TiO2-ZrO2-Fe2O3 system is of considerable interest for the development of the materials based on high-entropy oxides when their high-temperature endurance is required. However, limited information on its high-temperature behavior greatly limits its applications. In the present work, the potential of the geometric method for liquidus temperature calculation (GMLTC) in five-component oxide systems using data on the corresponding binary systems is verified for the first time with the example of the La2O3-SrO-TiO2-ZrO2-Fe2O3 system. The liquidus temperatures in the studied system calculated accordingly were experimentally confirmed by visual polythermal analysis within the limits not exceeding 10 % of the determined melting temperature. This allows us to recommend the proposed GMLTC approach for prediction of the position of liquidus curves in multicomponent oxide systems, which is particularly important for the calculations of liquidus temperatures of high-entropy oxides with unique physicochemical properties valuable for application at high temperatures up to 3000 K.

Formation and mechanical properties of Y-substituted (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ high-entropy fluorite oxide

In this paper, in order to improve the mechanical properties of high-entropy fluorite oxides (HEFOs), five equimolar multicomponent oxides were synthesized by solid-phase reaction method by using element Y replacing one of the five cations in (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ. The substitution of La, Sm or Nd in (Ce0.2Zr0.2La0.2Sm0.2Nd0.2)O2-δ with Y element are able to form single-phase HEFOs at 1600 °C, while Ce4+ and Zr4+ replaced by Y3+ contains a large number of secondary phase. The former three components are almost dense and smooth, and all the elements are uniformly distributed with no obvious segregation and agglomeration. The Ce3+ concentration of Y-substituted Sm HEFOs is calculated to be 13.7%, yielding a nominal composition of (Ce0.2Zr0.2Y0.2Sm0.2Nd0.2)O1.6863. In addition, the HEFOs have the best mechanical properties with Vickers hardnesses, flexural strengths and fracture toughnesses of 15.12 GPa, 101.1 MPa and 7.88 MPa-mm1/2, respectively, which have potential applications in high-performance structural materials.

Development and Validation of Neural Network Potentials for Multicomponent Oxide Glasses

Development and Validation of Neural Network Potentials for Multicomponent Oxide Glasses

Thermoelectric and electrical transport properties of mixed-conducting multicomponent oxides based on Ba(Zr,Ce)O3-δ

In this work, the chosen physicochemical properties of single-phase multicomponent oxides BaTi1/8Fe1/8Co1/8Y1/8Zr1/8Sn1/8Ce1/8Hf1/8O3-δ and BaTi1/9Fe1/9Co1/9Y1/9Zr1/9Sn1/9Ce1/9Hf1/9Bi1/9O3-δ were studied. The microstructure of the compounds strongly depended on the presence of bismuth in the structure. The electrical transport studies showed a level of electrical conductivity of ∼10-3 - 10-2 S/cm in the temperature range 673 – 1073 K. Electrical conductivity was thermally activated and the dominant conduction mechanism was the hopping of small polarons. Moreover, total electrical conductivity changes in the dry and humidified atmosphere at lower temperatures due to the presence of protonic defects in the structure. Thermoelectric measurements showed a relatively high value of the Seebeck coefficient for studied ceramics. Its values ranged between 50 and 250 μV/K depending on the sample and temperature. The Seebeck coefficient sign was positive, meaning that electron holes and/or oxygen vacancies were predominant charge carriers in oxidising atmospheres. Additionally, the Seebeck coefficient was found to be different in the humidified atmosphere which indicates an influence of protonic defects on thermoelectric transport. The obtained power factor Pf turned out to be low and dependent on the presence of protonic defects in the structure. This indicates, that the efficiency of the MOs-based operating thermoelectric generators can be controlled by changing the partial pressure of water vapor.

Tailored engineering of intracrystalline mesopores for boosting multicomponent volatile organic compounds simultaneous deep oxidation

Tailored engineering of intracrystalline mesopores for boosting multicomponent volatile organic compounds simultaneous deep oxidation

Manipulating Electron Delocalization of Metal Sites via a High-Entropy Strategy for Accelerating Oxygen Electrode Reactions in Lithium-Oxygen Batteries.

High-entropy perovskite oxides, in which the B-type metal site of perovskite oxides (ABO3) is occupied by over five kinds of transition metal ions, show promising applications in energy storage and conversion fields. Herein, high-entropy perovskite oxides (LaSr(5TM)O3) composed of Cr, Mn, Fe, Co, and Ni at the B-type metal site are prepared as oxygen electrocatalysts for Li-O2 batteries. The presence of compressive strain in LaSr(5TM)O3 effectively regulates the 3d orbit occupancy of the active Co site (Co2+ → Co3+) and lifts the energy level of the Co d-band center, thus leading to enhanced adsorption toward the LiO2 intermediate on Co sites. Furthermore, the high electron-drawing capability of Cr sites ensures sufficient electron exchange and further strengthens the adsorption of LiO2. As expected, the Li-O2 battery with a LaSr(5TM)O3 electrode delivers a low overpotential (0.79 V) and superior cyclability (226 cycles). This study provides a meaningful strain strategy to improve the electrocatalytic activity of multicomponent oxides via fabricating high-entropy materials.

Accelerating the screening of high-entropy Co-Mn-Fe-Ni-Zn-O gradient films for highly stable NTC materials through co-sputtering combinatorial synthesis

High-entropy negative temperature coefficient (NTC) thermistor thin films, renowned for their exceptional stability, represent a significant advancement in the field of temperature measurement, facilitating the miniaturization of next-generation information and electronic devices. However, “trial and error” approach to developing multi-component NTC oxides significantly constrains the efficiency of the design process. To accelerate development process, we prepared Co-Mn-Fe-Ni-Zn-O gradient films by co-sputtering combinatorial synthesis. The effects of stoichiometric ratios on the resistance (R25), material constant (B25/50) and stability (ΔR/R0) of gradient films were visually represented through color-coded maps for straightforward and intuitive analysis. Samples close to the MnCoFe target in gradient films showed a trend of decreasing resistance and increasing material constant, both reaching 1.71 MΩ and 4083 K, respectively. The high-entropy Co21Mn17Fe19Ni21Zn22O4±δ film exhibited the lowest resistance drift rate only 2.68 % after 500 h ageing at 125 ℃. Another delightful result was that the corresponding homogeneous films, achieved through sputtering with a composite target, had a relative deviation in resistance drift rate of merely 0.18 %. This showcased the successful translation from the screening outcome to the homogeneous film, significantly accelerating the development of NTC materials via the utilization of gradient films screening.

An Investigation of the Interface between Transition Metal Oxides (MnOx, FeOx, CoOx and NiOx)/MoO3 Composite Electrocatalysts for Oxygen Evolution Reactions

This study presents the synthesis of a multicomponent metal oxide electrocatalyst that increases the activity of the oxygen evolution reaction (OER). We synthesized transition metal oxides (MnOx, FeOx, CoOx, and NiOx) with MoO3 heterostructures through a solid-state reaction approach at low cost. In comparison to the other compositions, CoOx garnered higher attention and demonstrated superior performance on account of its large surface area and varied crystal facets. The MnOx-MoO3, FeOx-MoO3, CoOx-MoO3, and NiOx-MoO3 compositions attained an overpotential of 390 mV, 350 mV, 310 mV, and 340 mV, respectively, at a current density of 10 mA cm−2 in alkaline solution. The performance of OER was enhanced in CoOx-MoO3 at 10 mA cm−2, while FeOx-MoO3 exhibited a lower current density at 100 mA cm−2 than other metal oxides. The CoOx-MoO3 material exhibited a favorable crystal interface transition due to the presence of MoO3 oxide. For the first time, we report on the MoO3-to-(MnOx, FeOx, CoOx, and NiOx) interface crystal transition and the active surface area for OER catalytic activity in water-splitting processes. This investigation intends to develop an electrocatalyst that is capable of producing hydrogen with the use of heterostructure metal oxides.

Evolution of surface oxide layers during isothermal oxidation of a multi-component oxide dispersion strengthened Fe3Al alloy

Evolution of surface oxide layers during isothermal oxidation of a multi-component oxide dispersion strengthened Fe3Al alloy

Hydrogen technologies for decarbonization of ferrous metallurgy: scientific background and technical capabilities

To date, the use of ferrous hydrogen in metallurgy is considered from several positions. First, the partial or complete replacement of carbon with hydrogen reduces greenhouse gas emissions of CO2. Secondly, due to the different chemical affinity for oxygen, it becomes possible to selectively (selectively) extract components from complex complex ores and man-made materials. Thirdly, the absence of carbon in the reaction zone will make it possible to obtain a metal with a low content of carbides, which in many cases increases the demand for the product. Thermodynamic calculations of a multicomponent oxide system (Ni, Fe, P, Zn, Mn, V, Cr, O) in the presence of various reducing agents: carbon, hydrogen are performed using the TERRA software package, and their combined effects are considered. It is shown that the type of reducing agent affects the temperature of the beginning of the reduction of metals and the degree of their metallization. Thus, by selecting the type of reducing agent, its quantity, and the temperature of the process, it is possible to selectively extract some metals, and leave others in an oxidized state. Ilmenite concentrate in the form of a briquette was used in laboratory tests. The analysis of the iron reduction process using carbon or hydrogen as a reducing agent has been carried out. In comparison with the results obtained using carbon, the kinetics of iron reduction with hydrogen is higher. At the same time, the reduction proceeds with the formation of metallic iron, rutile (TiO2) and residual ilmenite. Whereas, in a carbothermic process occurring at higher temperatures (1000–1300 ℃), the reduction products are iron and iron ditanate (FeTi2O5). In addition, an important advantage of selective reduction by gas is the possibility of subsequent separation of the metallic and oxide phases by melting, without fear of secondary reduction due to solid carbon residues.

(Invited) Design of Photoactive Inorganic Nanomaterials for Environmental Challenges

Nowadays, one of the main technological challenges that we are facing is the ability to provide a sustainable supply of clean energy and, among all renewable sources, solar energy displays the greatest potential. Recently, the development of novel synthetic strategies has led to the preparation of nanostructured materials displaying unique properties compared to the bulk counterpart systems, with controlled and tunable morphologies able to enhance the activity and selectivity of a catalytic process. In particular, nanostructured materials synthesized via the bottom–up approach present an opportunity for future generation manufacturing of devices.This talk will focus on the importance of tuning the morphological features of a catalyst as a strategy to improve its optical and photocatalytic properties, focusing on how rationally designing inorganic materials at the nanoscale can lead to morphologies and structures suitable to enhance the performance of industrially and environmentally important processes. The talk will discuss some environmental applications that can be addressed by photoactive multi-component oxide systems synthesized via the bottom–up approach, highlighting their structure-reactivity relationship. Water contamination, in particular, is one of the upfront issues to be solved and complex organic molecules and pharmaceuticals, including antibiotics, are gaining attention due to their abuse and their low degradability. Photocatalytic drugs degradation will be presented as a successful case history [1-3] to provide inspiration to produce cheap, environmentally friendly, stable, and efficient photocatalysts, which hold a great potential for the development of new technologies not only for water remediation applications but also for energy applications in the field of solar fuel production.[1] E. Moretti, L. Storaro, A. Talon, P. Riello, A. Infantes Molina, E. Rodríguez-Castellón, Appl. Catal. B: Environmental 168 (2015) 385.[2] M. Telkhozhayeva, B. Hirsch, R. Konar, E. Teblum, R. Lavi, M. Weitman, B. Malik, E. Moretti, G.D. Nessim, Appl. Catal. B: Environmental 318 (2022) 121872.[3] L. Liccardo, M. Bordin, P.M. Sheverdyaeva, M. Belli, P. Moras, A. Vomiero, E. Moretti, Adv. Funct. Mater. 33 (2023) 2212486.

Ellingham diagrams of binary oxides

Controlling the oxidation state of constituents by tuning the oxidizing environment and materials chemistry is vital to the successful synthesis of targeted binary or multicomponent oxides. We have conducted a comprehensive thermodynamic analysis of 137 binary oxides to calculate their Ellingham diagrams. It is found that the “reactive” elements that oxidize easily are the f-block elements (lanthanides and actinides), elements in groups II, III, and IV (alkaline earth, Sc, Y, Ti, Zr, and Hf), and Al and Li. In contrast, the “noble” elements are easily reduced. These are coinage metals (Cu, Ag, and especially Au), Pt-group elements, and Hg and Se. Machine learning-based sequential feature selection indicates that the ease of oxidation can be represented by the electronic structures of pure elements, for example, their d- and s-valence electrons, Mendeleev numbers, and groups, making the Periodic Table a useful tool for qualitatively assessing the ease of oxidation. The other elemental features that weakly correlate with the ease of oxidation are thermochemical properties such as melting points and the standard entropy at 298 K of pure elements. Applying Ellingham diagrams enables the oxidation of multicomponent materials to be predicted, such as the Fe–20Cr–20Ni alloy (in wt. %) and the equimolar high entropy alloy of AlCoCrFeNi. These Ellingham diagram-based predictions are in accordance with thermodynamic calculations using the CALPHAD approach and experimental observations in the literature.

Enhanced bioactivity and mechanical properties of silicon-infused titanium oxide coatings formed by micro-arc oxidation on selective laser melted Ti13Nb13Zr alloy

The titanium scaffolds and surface-porous implants are manufactured by fast and cheap additive methods such as selective laser melting (SLM). The obtained irregularity and relative biological inertness of the titanium need proper surface modification. This research is aimed at forming bioactive multicomponent oxide coatings by micro-arc oxidation (MAO) at different process parameters on the selective laser-melted Ti13Zr13Nb alloy. The MAO process was carried out in a base solution containing 0.15 mol/L Ca and 0.1 mol/L GP, with different amounts of metasilicate added under two different applied voltages. Scanning electron microscopy, atomic force microscopy, X-ray electron diffraction spectroscopy, nanomechanical and nano scratch tests, water contact angle measurements, phosphate deposition observed in long-term immersion tests, and biological LDH and MTT assays were performed. The results showed that the coating microstructure, morphology, and properties were significantly dependent on process parameters. In particular, the metasilicate addition and its rising content in the electrolyte resulted in the higher development of the surface followed by better viability of osteoblasts at no necrosis, with no negative change in the other parameters, usually close to those obtained on silicon-free coatings. The obtained results prove that the addition of silicon to the electrolyte at the partial expense of calcium can be favorable for long-term titanium implants made by selective laser melting.

Extreme mixing in nanoporous high-entropy oxides for highly durable energy storage

The ability to mix many different metal cations in a single-phase nanoscale oxide is critical for property adjusting and new material discovery. However, synthesizing multicomponent high-entropy oxides (HEOs) consisting of over ten metal cations remains a challenge due to dissimilarity and immiscibility among these elements. Herein, we explore the accommodation ability of Al3Ni-type and Al3Ti-type intermetallic phases and find that the Al3Ni-type phase is powerful to accommodate many different kinds metal elements. By chemically dealloying the Al from the multicomponent Al3Ni-type intermetallic phase, multicomponent spinel oxides such as 7-component (AlNiCoRuMoCrFe)3O4, 8-component (AlNiCoRuMoCrFeTi)3O4, 13-component (AlNiCoCrFeCuMoVTaNbHfZrTi)3O4, 16-component (AlNiCoCrFeCuMoTaNbHfZrTiRuVPdY)3O4 et al., with nanoporous structure and poor crystallity are obtained. As a case study, we find that when applied in Li-ion battery anode, our 16-component nanoporous HEO exhibits a high capacity of ∼1141.2 mAh g−1 after 290 cycles at 0.1 A g−1 and excellent cycling stability. This study greatly expands the composition space of nanoscale HEOs and provides an interesting route for new materials discovery.

Strategies for regulating crystallinity and surface quality based on solvent multistage volatilization

In this paper, Bi2212 superconducting thin films were prepared with metal acetate as salt source and a mixture of acetic acid and N,N-dimethylformamide (DMF) as solvent. The volatilization process of the solvent was regulated by changing the ratio of the mixed solvent, which in turn achieved the regulation of the surface morphology and crystallinity of the Bi2212 superconducting films. The mechanism of the mixed solvents on the crystallinity and surface quality of Bi2212 superconducting films was systematically investigated. The results showed that the Bi2212 superconducting films were all (00l) epitaxial growth. The grain size of Bi2212 increased continuously with the increase of the proportion of acetic acid in the solvents. The grain size of the largest grain size was 43.8 nm when the proportion of acetic acid was 80 %. However, the high proportion of acetic acid in the mixed solvents reduced the surface quality of Bi2212 thin films. The minimum surface roughness was 15.0 nm at 40 % acetic acid. All the samples exhibited good superconducting properties. This work provides a research basis for the systematic preparation of multicomponent oxide thin films.

Nanoparticles of MnFeNiCuBi high entropy alloy as catalyst for Fenton and photo-Fenton decomposition of p-nitrophenol

We report here preparation of an equi-atomic high entropy alloy (HEA) where Bi (hexagonal) was used along with Mn, Fe, Ni and Cu. The HEA assumed fcc structure after ball milling for 60 h of the arc melted component which was initially having multiple phases. XRD and TEM studies corroborated the HEA formation. The XPS studies of the milled sample inferred a probable formation of multicomponent oxide shells on the surface, which could generate a band gap of 1.62 eV. Hence, the present material emerged as an efficient catalyst, which could completely decompose, PNP in 60 min for Fenton and 20 min for photo-Fenton processes. When tested for four cycles, the HEA also displayed appreciable stability as a photo-Fenton catalyst. Further, the catalyst’s soft ferromagnetic nature (MS = 4.55 emu/g) contributes to its recyclability. Given the associated challenges with conventional Fe catalysts utilized in Fenton and photo-Fenton processes, this work provides an alternative as a promising catalyst for treating PNP-containing wastewater.

Porous hollow sphere structure PrFeO3 as an efficient sensing material for n-butanol detection

N-butanol is a harmful volatile gas, so creating an appropriate n-butanol sensor is critical for preserving human health and the manufacturing environment. In contrast to single metal oxide semiconductors, multicomponent metal oxides, especially perovskite ternary metal oxides with the ABO3 structure, exhibit significant potential for development owing to their precise structures and diverse physicochemical properties. In this paper, three-dimensional porous hollow spheres PrFeO3 were synthesized by combining air annealing and hydrothermal techniques. The crystal structure, surface composition, chemical state, and morphology of PrFeO3 materials were evaluated using several kinds of characterization approaches. The gas sensitivity of PrFeO3 materials was also thoroughly explored. The results show that at the optimal working temperature of 280 ℃, the PrFeO3 material excels in n-butanol gas sensing, with a response of 85 for 100 ppm n-butanol. Additionally, the sensor demonstrates high selectivity for n-butanol gases, low concentration detection capability, outstanding repeatability, rapid reaction recovery time (18 s/13 s), long-term stability, and exceptional reproducibility. The unique morphology and high oxygen vacancy content of PrFeO3 provide numerous active sites on its surface, promoting the adsorption and desorption of n-butanol gas molecules and enhancing its gas-sensitive properties.

Ablation mechanism of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composite during plasma ablation above 2000 °C

Air plasma ablation behavior of Cf/(Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C-SiC composite was studied systematically with the surface temperature above 2000 °C at the ablation center. It presents a linear recession rate of 0.15 μm/s and a mass recession rate of 2.05 mg/s after ablation at 4 MW/m2 (2000 °C) for 300 s. Associated with the temperature gradient of the ablation surface, the oxidation products at different locations mainly consist of (TiZrHfNbTa)Ox, (ZrxHf1–x)6(NbyTa1–y)2O17, Ti(NbxTa1–x)2O7, (HfxZr1–x)SiO4, and SiO2. Due to the synergistic effect of the multi-component oxides, oxidation products form a protective structure composed of high melting point oxide skeleton filled with relatively low melting point phases. It retards oxygen inward diffusion and prevents the composite fragmentation caused by plasma mechanical scouring. It is believed that the results would be helpful for further improving the ablation resistance by component design of high entropy ceramics and their composites.

Investigation of the CMAS corrosion resistance of high-entropy oxides through B-site cation doping

High-temperature erosion caused by calcium magnesium aluminum silicate (CMAS) poses a significant challenge to the advancement of thermal barrier coatings (TBCs). In this investigation, four multi-component A2B2O7 type oxide TBC materials, namely Eu2(Y0.2Ce0.2Zr0.2Hf0.2Ta0.2)2O7, Eu2(Y0.2Yb0.2Ce0.2Nb0.2Ta0.2)2O7, Eu2(Y0.2Yb0.2Zr0.2Nb0.2Ta0.2)2O7, and Eu2(Y0.2Yb0.2Hf0.2Nb0.2Ta0.2)2O7, were synthesized using the solid-state method. We investigated the corrosion behavior of molten CMAS on the samples at 1300 °C for durations of 1 h, 20 h, and 50 h. The resulting corrosion products consist of apatite and cubic fluorite structures. Our analysis reveals that as the ionic radius of RE3+ increases, the stability of the apatite structure improves. Furthermore, molten CMAS exhibits varied wetting behaviors on different substrates at the same temperature. A higher contact angle suggests that the CMAS melt will encounter difficulty in diffusing and penetrating the substrate surface. This research will contribute to the development of TBC materials with enhanced resistance to CMAS corrosion.