Journal articles: 'High entropy oxides'

1

Meisenheimer, P. B., and J. T. Heron. "Oxides and the high entropy regime: A new mix for engineering physical properties." MRS Advances 5, no. 64 (2020): 3419–36. http://dx.doi.org/10.1557/adv.2020.295.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

AbstractHistorically, the enthalpy is the criterion for oxide materials discovery and design. In this regime, highly controlled thin film epitaxy can be leveraged to manifest bulk and interfacial phases that are non-existent in bulk equilibrium phase diagrams. With the recent discovery of entropy-stabilized oxides, entropy and disorder engineering has been realized as an orthogonal approach. This has led to the nucleation and rapid growth of research on high-entropy oxides – multicomponent oxides where the configurational entropy is large but its contribution to its stabilization need not be significant or is currently unknown. From current research, it is clear that entropy enhances the chemical solubility of species and can realize new stereochemical configurations which has led to the rapid discovery of new phases and compositions. The research has expanded beyond studies to understand the role of entropy in stabilization and realization of new crystal structures to now include physical properties and the roles of local and global disorder. Here, key observations made regarding the dielectric and magnetic properties are reviewed. These materials have recently been observed to display concerted symmetry breaking, metal-insulator transitions, and magnetism, paving the way for engineering of these and potentially other functional phenomena. Excitingly, the disorder in these oxides allows for new interplay between spin, orbital, charge, and lattice degrees of freedom to design the physical behavior. We also provide a perspective on the state of the field and prospects for entropic oxide materials in applications considering their unique characteristics.

2

Ding, Yiwen, Keju Ren, Chen Chen, Li Huan, Rongli Gao, Xiaoling Deng, Gang Chen, et al. "High-entropy perovskite ceramics: Advances in structure and properties." Processing and Application of Ceramics 18, no. 1 (2024): 1–11. http://dx.doi.org/10.2298/pac2401001d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High-entropy ceramic materials usually refer to the multi-principal solid solution formed by 5 or more ceramic components. Due to its novel ?high-entropy effect? and excellent performance, it has become one of the research hotspots in the field of ceramics in recent years. As the research system of high-entropy ceramics has gradually expanded from the initial rock salt oxides (Mg-Ni-Co-Cu-Zn)O to fluorite oxides, perovskite oxides, spinel oxides, borides, carbides and silicates, its special mechanical, electrical, magnetic and energy storage properties have been continuously discovered. Based on the basic principle of high-entropy materials, this paper mainly introduces the prominent perovskite-type oxide high-entropy ceramics in recent years from the perspective of ceramic structure and properties, and predicts the development trend of high-entropy perovskite-type ceramics in the next few years.

3

Gild, Joshua, Mojtaba Samiee, Jeffrey L. Braun, Tyler Harrington, Heidy Vega, Patrick E. Hopkins, Kenneth Vecchio, and Jian Luo. "High-entropy fluorite oxides." Journal of the European Ceramic Society 38, no. 10 (August 2018): 3578–84. http://dx.doi.org/10.1016/j.jeurceramsoc.2018.04.010.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Li, Haoyang, Yue Zhou, Zhihao Liang, Honglong Ning, Xiao Fu, Zhuohui Xu, Tian Qiu, Wei Xu, Rihui Yao, and Junbiao Peng. "High-Entropy Oxides: Advanced Research on Electrical Properties." Coatings 11, no. 6 (May 24, 2021): 628. http://dx.doi.org/10.3390/coatings11060628.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The concept of “high entropy” was first proposed while exploring the unknown center of the metal alloy phase diagram, and then expanded to oxides. The colossal dielectric constant found on the bulk high-entropy oxides (HEOs) reveals the potential application of the high-entropy oxides in the dielectric aspects. Despite the fact that known HEO thin films have not been reported in the field of dielectric properties so far, with the high-entropy effects and theoretical guidance of high entropy, it is predictable that they will be discovered. Currently, researchers are verifying that appropriately increasing the oxygen content in the oxide, raising the temperature and raising the pressure during preparation have an obvious influence on thin films’ resistivity, which may be the guidance on obtaining an HEO film large dielectric constant. Finally, it could composite a metal–insulator–metal capacitor, and contribute to sensors and energy storage devices’ development; alternatively, it could be put into application in emerging thin-film transistor technologies, such as those based on amorphous metal oxide semiconductors, semiconducting carbon nanotubes, and organic semiconductors.

5

Bridges, Craig A., Bishnu Prasad Thapaliya, Albina Borisevich, Juntian Fan, and Sheng Dai. "(Invited) High Entropy Multication Oxide Battery Materials." ECS Meeting Abstracts MA2022-02, no. 1 (October 9, 2022): 29. http://dx.doi.org/10.1149/ma2022-02129mtgabs.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy oxides (HEOs), in which multication occupation of a single crystallographic site plays an important role in the properties, have become relevant in energy storage [1,2], catalysis [3.4], and many more areas. In a subset of these compounds the entropy, rather than enthalpy, plays a dominant role in stabilizing a single-phase structure at high temperatures. In other cases, the multication occupation merely contributes to stability and properties, but the entropy remains dominant in the stability. The field originated with high entropy metal alloys (HEAs)[5], and then expanded to oxides, borides, sulfides, and more. In the case of HEOs, the first example is the rock salt (Mg0.2Ni0.2Co0.2Cu0.2Zn0.2)O, which has generated a great deal of interest in this class of materials.[6,7] It has been shown that HEOs are of interest for high ionic conductivity and electrochemical energy storage. We have examined the electrochemical performance of new high entropy elecrolytes and found an effect of composition on the cycling performance. Samples were prepared through sol-gel routes and high energy milling of starting binary oxides. We have investigated the synthesis using high temperature in-situ X-ray diffraction on a Panalytical diffractometer equipped with an XRK900 stage. STEM/EDS studies on ex-situ samples will be presented that show elemental distribution, with Raman and EIS measurements providing information on ionic diffusion. The results of this study will be highly impactful for the growing community of researchers investigating the design and synthesis of the new class of materials, the high entropy oxides. [1] Q. Wang, et. al., Multi-anionic and -cationic compounds: new high entropy materials for advanced Li-ion batteries, Energy Environ. Sci., 2019, 12, 2433; [2] D. Berardan, et. al., Room temperature lithium superionic conductivity in high entropy oxides, J. Mater. Chem. A, 2016, 4, 9536.; [3] H. Chen, et al., Mechanochemical Synthesis of High Entropy Oxide Materials under Ambient Conditions: Dispersion of Catalysts via Entropy Maximization, ACS Materials Lett. 2019, 1, 1, 83–88; [4] H. Chen, et. al., Entropy-stabilized metal oxide solid solutions as CO oxidation catalysts with high-temperature stability, J. Mater. Chem. A 2018, 6, 11129-11133; [5] Y. Lu, et. al., Sci. Rep. 4, 6200 (2014); Y. F. Ye, et. al., Mater. Today 19 (6), 349 (2016); Zhang, Y., et. al., Nature Commun. 6, 8736 (2015); [6] C. M. Rost, et. al., Nature Commun. 6, 8485 (2015); [7] B. Jiang, et. al., Probing the Local Site Disorder and Distortion in Pyrochlore High-Entropy Oxides. Journal of the American Chemical Society 2021, 143, (11), 4193-4204

6

YILDIZ, İlker. "Synthesis and characterization of b-site controlled la-based high entropy perovskite oxides." Journal of Scientific Reports-A, no. 055 (December 31, 2023): 124–31. http://dx.doi.org/10.59313/jsr-a.1370632.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy perovskite oxide materials are a highly promising class of materials with a wide range of potential applications. They offer a unique combination of perovskite oxides and high entropy oxides, making them suitable for various fields, particularly in electrochemical energy storage systems and hydrogen production. Given the growing demand for clean energy and efficient energy storage solutions, the development of high entropy materials holds great significance. In this study, a cost-effective and rapid fabrication method was employed to produce several single-phase high entropy perovskite oxides by altering the B-site cations. The results demonstrated that these high entropy perovskite oxides could be synthesized with the same crystal structure, despite having significantly different elemental compositions. These variations in elemental composition led to differences in lattice parameters, metal-oxygen bond strengths, and oxygen vacancy content within the materials. Understanding and manipulating these factors can have important implications for the design of high entropy materials for energy storage and other applications.

7

Dupuy, Alexander D., Xin Wang, and Julie M. Schoenung. "Entropic phase transformation in nanocrystalline high entropy oxides." Materials Research Letters 7, no. 2 (December 14, 2018): 60–67. http://dx.doi.org/10.1080/21663831.2018.1554605.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Oh, Seeun, Dongyeon Kim, and Kang Taek Lee. "High Entropy Perovskite Electrolytes for Reversible Protonic Ceramic Electrochemical Cells." ECS Meeting Abstracts MA2023-01, no. 54 (August 28, 2023): 270. http://dx.doi.org/10.1149/ma2023-0154270mtgabs.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Reversible protonic ceramic electrochemical cells (R-PCECs) become cornerstones of low-temperature solid oxide electrochemical cells (SOCs) below 600 °C. Low activation energy and high energy conversion efficiency are primary significance of R-PCECs. However, electrolytes of high-performance R-PCECs still suffer from poor tolerance to complex operating conditions. To overcome their low stability and enhance proton conductivity, various cations have been doped into the Ba-based perovskite oxide electrolyte. Developing high entropy oxides by introducing multiple metal cations into A- or B- sites of the perovskite structure can be an effective solution for the structural stability. Due to the effect of the entropy-dominated stabilization in multi-doped perovskite oxides, the material can remain single phase under extreme temperatures and chemical environments. Promising high entropy stabilization concepts were adapted to electrolytes, and finally, durable proton-conducting perovskite oxide was designed. Here, we will present our recent progress on development of high entropy perovskite oxide electrolytes for R-PCECs.

9

Oh, Seeun, Dongyeon Kim, and Kang Taek Lee. "High Entropy Perovskite Electrolytes for Reversible Protonic Ceramic Electrochemical Cells." ECS Transactions 111, no. 6 (May 19, 2023): 1743–49. http://dx.doi.org/10.1149/11106.1743ecst.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Reversible protonic ceramic electrochemical cells (R-PCECs) have become the cornerstone of low-temperature solid oxide electrochemical cells (SOCs) below 600 °C. Low activation energy and high energy conversion efficiency are primary significance of R-PCECs. However, electrolytes of high-performance R-PCECs still suffer from poor tolerance to complex operating conditions. To overcome their low stability and enhance proton conductivity, various cations have been doped into the Ba-based perovskite oxide electrolyte. Developing high entropy oxides by introducing multiple metal cations into A- or B- sites of the perovskite structure can be an effective solution for the structural stability. Due to the effect of the entropy-dominated stabilization in multi-doped perovskite oxides, the material can remain single phase under extreme temperatures and chemical environments. Promising high entropy stabilization concepts were adapted to electrolytes, and finally, durable proton-conducting perovskite oxide was designed. Here, we will present our recent progress on development of high entropy perovskite oxide electrolytes for R-PCECs.

10

McCormack, Scott J., and Alexandra Navrotsky. "Thermodynamics of high entropy oxides." Acta Materialia 202 (January 2021): 1–21. http://dx.doi.org/10.1016/j.actamat.2020.10.043.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Tanveer, Rubayet, and Veerle M. Keppens. "Resonant ultrasound spectroscopy studies of high-entropy fluorites." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A131. http://dx.doi.org/10.1121/10.0015786.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy oxides (HEOs), also referred to as multicomponent oxides or compositionally complex oxides (CCOs), have attracted attention due to the tunability of multiple cations on a single site. Since the introduction of HEOs stabilized in the rocksalt phase, the high entropy oxide concept has been expanded to various structures, offering a path for the discovery of innovative compounds with unique structure-property relations. Here, we present a study of high entropy fluorites, which have gained recognition for their low thermal conductivity and possible applications as thermal barrier coatings. We have successfully synthesized single phase samples using multiple cations on a single site, in equimolar and non-equimolar ratios. Resonant ultrasound spectroscopy was used to evaluate the elastic moduli as a function of temperature. The results obtained on these multi-component pyrochlores are compared to those of their single-component counterparts.

12

Sarkar, Abhishek, Qingsong Wang, Alexander Schiele, Mohammed Reda Chellali, Subramshu S. Bhattacharya, Di Wang, Torsten Brezesinski, Horst Hahn, Leonardo Velasco, and Ben Breitung. "High‐Entropy Oxides: High‐Entropy Oxides: Fundamental Aspects and Electrochemical Properties (Adv. Mater. 26/2019)." Advanced Materials 31, no. 26 (June 2019): 1970189. http://dx.doi.org/10.1002/adma.201970189.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Kajitani, Tsuyoshi, Yuzuru Miyazaki, Kei Hayashi, Kunio Yubuta, X. Y. Huang, and W. Koshibae. "Thermoelectric Energy Conversion and Ceramic Thermoelectrics." Materials Science Forum 671 (January 2011): 1–20. http://dx.doi.org/10.4028/www.scientific.net/msf.671.1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Oxide thermoelectrics are relatively new materials that are workable at temperatures in the range of 400K≤T≤1200K. There are several types of thermoelectric oxide, namely, cobalt oxides (p-type semi-conductors), manganese oxides (n-type) and zinc oxides (n-type semi-conductors) for high temperature energy harvesting. The Seebeck coefficient of 3d metal oxide thermoelectrics is relatively high due to either high density of states at Fermi surfaces or spin entropy flow associated with the carrier flow. The spin entropy part dominates the Seebeck coefficient of 3d-metal oxides at temperatures above 300K. Introduction of impurity particles or quantum-well structures to enhance thermionic emission and energy filtering effects for the oxide semiconductors may lead to a significant improvement of thermoelectric performance.

14

Hashishin, Takeshi, Haruka Taniguchi, Fei Li, and Hiroya Abe. "Useful High-Entropy Source on Spinel Oxides for Gas Detection." Sensors 22, no. 11 (June 1, 2022): 4233. http://dx.doi.org/10.3390/s22114233.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

This study aimed to identify a useful high-entropy source for gas detection by spinel oxides that are composed of five cations in nearly equal molar amounts and free of impurities. The sensor responses of the spinel oxides [1# (CoCrFeMnNi)3O4, 2# (CoCrFeMnZn)3O4, 3# (CoCrFeNiZn)3O4, 4# (CoCrMnNiZn)3O4, 5# (CoFeMnNiZn)3O4, and 6# (CrFeMnNiZn)3O4] were evaluated for the test gases (7 ppm NO2, 5000 ppm H2, 3 ppm NH3, and 3 ppm H2S). In response to NO2, 1# and 2# showed p-type behavior while 3–6# showed n-type semiconductor behavior. There are three p-type and one n-type AO structural compositions in AB2O4[AO·B2O3] type spinel, and 1# showed a stable AO composition because cation migration from site B to site A is unlikely. Therefore, it was assumed that 1# exhibited p-type behavior. The p-type behavior of 2# was influenced by Cr oxide ions that were present at the B site and the stable p-type behavior of zinc oxide at the A site. The spinel oxides 3# to 6# exhibited n-type behavior with the other cationic oxides rather than the dominant p-type behavior exhibited by the Zn oxide ions that are stable at the A site. In contrast, the sensor response to the reducing gases H2, NH3, and H2S showed p-type semiconductor behavior, with a particularly selective response to H2S. The sensor responses of the five-element spinel oxides in this study tended to be higher than that of the two-element Ni ferrites and three-element Ni-Zn ferrites reported previously. Additionally, the susceptibility to sulfurization was evaluated using the thermodynamic equilibrium theory for the AO and B2O3 compositions. The oxides of Cr, Fe, and Mn ions in the B2O3 composition did not respond to H2S because they were not sulfurized. The increase in the sensor response due to sulfurization was attributed to the decrease in the depletion layer owing to electron sensitization, as the top surface of the p-type semiconductors, ZnO and NiO, transformed to n-type semiconductors, ZnS and NiS, respectively. High-entropy oxides prepared using the hydrothermal method with an equimolar combination of five cations from six elements (Cr, Mn, Fe, Co, Ni, and Zn) can be used as a guideline for the design of high-sensitivity spinel-type composite oxide gas sensors.

15

Chroneos, Alexander. "Oxygen Self-Diffusion in Fluorite High Entropy Oxides." Applied Sciences 14, no. 12 (June 19, 2024): 5309. http://dx.doi.org/10.3390/app14125309.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High-entropy oxides have recently attracted the interest of the community as a way of attuning the properties of oxides to energy applications. Here, we employ molecular dynamics simulations combined with empirical pair potential models to examine the predicted oxygen diffusivity of fluorite-structured high-entropy oxides. We show that lower levels of the dopants increase the overall diffusivity of the composition, but not to the levels of diffusion seen in yttria-doped zirconia. We attribute this to an increased resistance of the cation sublattice to the distortion that occurs through any multiple substitutions on the cation sublattice. To conclude, it is calculated that oxygen self-diffusion in high-entropy oxides is suppressed as compared to isostructural ternary oxides.

16

Chen, Hao, Yifan Sun, Shize Yang, Hui Wang, Wojciech Dmowski, Takeshi Egami, and Sheng Dai. "Self-regenerative noble metal catalysts supported on high-entropy oxides." Chemical Communications 56, no. 95 (2020): 15056–59. http://dx.doi.org/10.1039/d0cc05860b.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

A reversible temperature-dependent dissolution–exsolution process was discovered for noble metal species supported on high-entropy oxides, which indicates the potential to exploit the enhanced entropic effects to access self-regenerative catalysts.

17

Sarkar, Abhishek, Robert Kruk, and Horst Hahn. "Magnetic properties of high entropy oxides." Dalton Transactions 50, no. 6 (2021): 1973–82. http://dx.doi.org/10.1039/d0dt04154h.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Mazza, Alessandro R., Elizabeth Skoropata, Yogesh Sharma, Jason Lapano, Thomas W. Heitmann, Brianna L. Musico, Veerle Keppens, et al. "Designing Magnetism in High Entropy Oxides." Advanced Science 9, no. 10 (February 11, 2022): 2200391. http://dx.doi.org/10.1002/advs.202200391.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

CAYIRLI, Meltem, Esra ERDOGAN-ESEN, Ersu LOKCU, and Mustafa ANIK. "Synthesis and Electrochemical Performance of Spinel Crystal Structured ((FeNiCrMn)1-xCox)3O4 (x=0.1, 0.2, 0.3) High Entropy Oxides." Eurasia Proceedings of Science Technology Engineering and Mathematics 16 (December 31, 2021): 140–44. http://dx.doi.org/10.55549/epstem.1068579.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy oxides are a new class of materials with a single-phase structure consisting of five or more components. Due to their high structural stability and electrochemical performance, they have attracted a lot of attention in recent years. In this study, high entropy oxides with the composition ((FeNiCrMn)1-xCox)3O4 (x=0.1, 0.2, 0.3) were synthesized using the solid state method and their electrochemical performances as anode material for lithium-ion battery were investigated. Spinel crystal structured of high entropy oxides were characterized by X-ray diffraction (XRD) technique. The electrochemical performance of anodes were evaluated by assembling CR2016 type coin cell. As a result of galvanostatic charge/discharge experiments the initial discharge capacities of ((FeNiCrMn)1-xCox)3O4 (x=0.1, 0.2, 0.3) anodes at a current density of 50 mA g-1 werecalculated as 1993 mA h g-1, 1651 mA h g-1 and 1706 mA h g-1, respectively. Among the synthesized high entropy oxide anodes, the ((FeNiCrMn)0.9Co0.1)3O4 anode shows high initial discharge capacity, while their capacity retention rates at the end of 10th cycle were calculated as 53.9%, 55.1%, 59.7%. This study clearly indicates that the electrochemical performances of high entropy oxide anodes are affected by the Co content.

20

Bérardan, D., S. Franger, A. K. Meena, and N. Dragoe. "Room temperature lithium superionic conductivity in high entropy oxides." Journal of Materials Chemistry A 4, no. 24 (2016): 9536–41. http://dx.doi.org/10.1039/c6ta03249d.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Impedance spectroscopy measurements evidence superionic Li⁺ mobility (>10⁻³ S cm⁻¹) at room temperature and fast ionic mobility for Na⁺ (5 × 10⁻⁶ S cm⁻¹) in high entropy oxides, a new family of oxide-based materials with the general formula (MgCoNiCuZn)_1−x−yGa_yA_xO (with A = Li, Na, K).

21

Sarkar, Abhishek, Ben Breitung, and Horst Hahn. "High entropy oxides: The role of entropy, enthalpy and synergy." Scripta Materialia 187 (October 2020): 43–48. http://dx.doi.org/10.1016/j.scriptamat.2020.05.019.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Sun, Yifan, and Sheng Dai. "High-entropy materials for catalysis: A new frontier." Science Advances 7, no. 20 (May 2021): eabg1600. http://dx.doi.org/10.1126/sciadv.abg1600.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Entropy plays a pivotal role in catalysis, and extensive research efforts have been directed to understanding the enthalpy-entropy relationship that defines the reaction pathways of molecular species. On the other side, surface of the catalysts, entropic effects have been rarely investigated because of the difficulty in deciphering the increased complexities in multicomponent systems. Recent advances in high-entropy materials (HEMs) have triggered broad interests in exploring entropy-stabilized systems for catalysis, where the enhanced configurational entropy affords a virtually unlimited scope for tailoring the structures and properties of HEMs. In this review, we summarize recent progress in the discovery and design of HEMs for catalysis. The correlation between compositional and structural engineering and optimization of the catalytic behaviors is highlighted for high-entropy alloys, oxides, and beyond. Tuning composition and configuration of HEMs introduces untapped opportunities for accessing better catalysts and resolving issues that are considered challenging in conventional, simple systems.

23

Yurchenko, Nikita, Evgeniya Panina, Sergey Zherebtsov, Gennady Salishchev, and Nikita Stepanov. "Oxidation Behavior of Refractory AlNbTiVZr0.25 High-Entropy Alloy." Materials 11, no. 12 (December 12, 2018): 2526. http://dx.doi.org/10.3390/ma11122526.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Oxidation behavior of a refractory AlNbTiVZr0.25 high-entropy alloy at 600–900 °C was investigated. At 600–700 °C, two-stage oxidation kinetics was found: Nearly parabolic oxidation (n = 0.46–0.48) at the first stage, transitioned to breakaway oxidation (n = 0.75–0.72) at the second stage. At 800 °C, the oxidation kinetics was nearly linear (n = 0.92) throughout the entire duration of testing. At 900 °C, the specimen disintegrated after 50 h of testing. The specific mass gains were estimated to be 7.2, 38.1, and 107.5, and 225.5 mg/cm2 at 600, 700, and 800 °C for 100 h, and 900 °C for 50 h, respectively. Phase compositions and morphology of the oxide scales were analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was shown that the surface layer at 600 °C consisted of the V2O5, VO2, TiO2, Nb2O5, and TiNb2O7 oxides. Meanwhile, the scale at 900 °C comprised of complex TiNb2O7, AlNbO4, and Nb2Zr6O17 oxides. The oxidation mechanisms operating at different temperatures were discussed and a comparison of oxidation characteristics with the other alloys was conducted.

24

Pikalova, Elena Y., Elena G. Kalinina, Nadezhda S. Pikalova, and Elena A. Filonova. "High-Entropy Materials in SOFC Technology: Theoretical Foundations for Their Creation, Features of Synthesis, and Recent Achievements." Materials 15, no. 24 (December 8, 2022): 8783. http://dx.doi.org/10.3390/ma15248783.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

In this review, recent achievements in the application of high-entropy alloys (HEAs) and high-entropy oxides (HEOs) in the technology of solid oxide fuel cells (SOFC) are discussed for the first time. The mechanisms of the stabilization of a high-entropy state in such materials, as well as the effect of structural and charge factors on the stability of the resulting homogeneous solid solution are performed. An introduction to the synthesis methods for HEAs and HEOs is given. The review highlights such advantages of high-entropy materials as high strength and the sluggish diffusion of components, which are promising for the use at the elevated temperatures, which are characteristic of SOFCs. Application of the medium- and high-entropy materials in the hydrocarbon-fueled SOFCs as protective layers for interconnectors and as anode components, caused by their high stability, are covered. High-entropy solid electrolytes are discussed in comparison with traditional electrolyte materials in terms of conductivity. High-entropy oxides are considered as prospective cathodes for SOFCs due to their superior electrochemical activity and long-term stability compared with the conventional perovskites. The present review also determines the prioritizing directions in the future development of high-entropy materials as electrolytes and electrodes for SOFCs operating in the intermediate and low temperature ranges.

25

Brahlek, Matthew, Maria Gazda, Veerle Keppens, Alessandro R. Mazza, Scott J. McCormack, Aleksandra Mielewczyk-Gryń, Brianna Musico, et al. "What is in a name: Defining “high entropy” oxides." APL Materials 10, no. 11 (November 1, 2022): 110902. http://dx.doi.org/10.1063/5.0122727.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy oxides are emerging as an exciting new avenue to design highly tailored functional behaviors that have no traditional counterparts. Study and application of these materials are bringing together scientists and engineers from physics, chemistry, and materials science. The diversity of each of these disciplines comes with perspectives and jargon that may be confusing to those outside of the individual fields, which can result in miscommunication of important aspects of research. In this Perspective, we provide examples of research and characterization taken from these different fields to provide a framework for classifying the differences between compositionally complex oxides, high entropy oxides, and entropy stabilized oxides, which is intended to bring a common language to this emerging area. We highlight the critical importance of understanding a material’s crystallinity, composition, and mixing length scales in determining its true definition.

26

Bérardan, David, Sylvain Franger, Diana Dragoe, Arun Kumar Meena, and Nita Dragoe. "Colossal dielectric constant in high entropy oxides." physica status solidi (RRL) - Rapid Research Letters 10, no. 4 (March 1, 2016): 328–33. http://dx.doi.org/10.1002/pssr.201600043.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Sealy, Cordelia. "High-entropy perovskite oxides promise better catalysts." Nano Today 50 (June 2023): 101871. http://dx.doi.org/10.1016/j.nantod.2023.101871.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Csík, D., D. Zalka, K. Saksl, D. Capková, and R. Džunda. "Four-component high entropy spinel oxide as anode material in lithium-ion batteries with excellent cyclability." Journal of Physics: Conference Series 2382, no. 1 (November 1, 2022): 012003. http://dx.doi.org/10.1088/1742-6596/2382/1/012003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Nowadays, energy storage technologies are in focus of public interest, especially in the field of the automotive industry. Lithium-ion batteries (LIBs) are evaluated as one of the most advanced energy storage devices because of their high energy density, which can meet rapidly growing energy requirements. Graphite based anode materials in LIBs are reaching their fundamental limits, especially their specific capacities. Recently, it has been demonstrated that high entropy oxides (HEOs) possess promising and unexpected electrochemical properties, such as remarkable reversible capacity and cycle stability due to the high entropy of the system. The highly disordered structure can provide self-healing properties resulting in regeneration of the capacity by applying low current densities. In addition, they can alleviate volume changes during the cycling process, unlike simple oxides. Among the various types of high entropy oxides, spinel-structured HEOs are the most studied because they ensure the three-dimensional transport of lithium ions ensuring high rate capability. Herein, we report a simple method of preparation of high entropy oxide (HEO) with a spinel structure consisting of 4 different elements (Co, Fe, Cr, Ni). The prepared HEO exhibited excellent cycle stability during (116 mAh.g-1) 500 cycles at a current density of 500 mA.g-1, which confirms their usage as anode active materials in lithium-ion batteries.

29

Matovic, Branko, Jelena Maletaskic, Vesna Maksimovic, Jelena Zagorac, Aleksa Lukovic, Yu-Ping Zeng, and Ivana Cvijovic-Alagic. "Heavily doped high-entropy A2B2O7 pyrochlore." Processing and Application of Ceramics 17, no. 2 (2023): 113–17. http://dx.doi.org/10.2298/pac2302113m.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

A novel class of high-entropy pyrochlore compounds with multiple elements at the A and B site positions (A2B2O7) was successfully obtained. Powders with (La1/7Sm1/7Nd1/7Pr1/7Y1/7Gd1/7Yb1/7)2(Sn1/3Hf1/3Zr1/3)2O7 nominal composition were fabricated from pure metal oxides obtained through a reaction of metal nitrates (for site A) and metal chlorides (for site B) with sodium hydroxide during the solid-state displacement reaction (SSDR). The phase evolution was analyzed using XRD method. During the thermal treatment of ten individual metal oxides, the single pyrochlore phase was created. The present study showed that the highdensity (98%TD) ceramics with a hardness of 8.1GPa was successfully obtained after pressureless sintering at 1650 ?C for 4 h. Results of the Raman study and the Rietveld structural refinement showed that sintered highentropy ceramics is characterized by a single-phase pyrochlore structure, which was investigated in detail.

30

Ke, Lingsheng, Long Meng, Sheng Fang, Chun Lin, Mingtian Tan, and Tao Qi. "High-Temperature Oxidation Behaviors of AlCrTiSi0.2 High-Entropy Alloy Doped with Rare Earth La and Y." Crystals 13, no. 8 (July 27, 2023): 1169. http://dx.doi.org/10.3390/cryst13081169.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High-entropy alloys (HEAs) were prepared with strong antioxidant metals Al, Cr, Ti, and Si as matrix elements, and the effects of rare earth (RE) lanthanum (La) and yttrium (Y) doping on their microstructures and high-temperature oxidation resistance were explored in this study. The AlCrTiSi0.2RE0.02 HEAs were prepared by using vacuum arc melting and were oxidized mass gain at 1000 °C. After oxidation for 53 h, AlCrTiSi0.2 HEA had a mass increase of 1.195 mg/cm2, and it had the best oxidation resistance of three HEAs (AlCrTiSi0.2, AlCrTiSi0.2La0.02, and AlCrTiSi0.2Y0.02). The surface oxide layers of three HEAs mainly consisted of Al and Ti oxides; the layered oxide film of AlCrTiSi0.2 alloy was mainly composed of dense Al2O3, and the acicular oxide films of AlCrTiSi0.2La0.02 and AlCrTiSi0.2Y0.02 alloys were primarily composed of loose Ti oxide. Doping La and Y decreased the oxidation resistance of AlCrTiSi0.2. In the early stage of oxidation of rare earth HEAs, the surface oxide layer was loose because La and Y reacted with the matrix metal, which slowed down the diffusion of element Al or accelerated the diffusion of element Ti. In the late stage of oxidation, La and Y interacted with O and entered the matrix metal to form rare earth oxides.

31

Roy, Indranil, Pratik K. Ray, and Ganesh Balasubramanian. "Modeling Oxidation of AlCoCrFeNi High-Entropy Alloy Using Stochastic Cellular Automata." Entropy 24, no. 9 (September 8, 2022): 1263. http://dx.doi.org/10.3390/e24091263.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Together with the thermodynamics and kinetics, the complex microstructure of high-entropy alloys (HEAs) exerts a significant influence on the associated oxidation mechanisms in these concentrated solid solutions. To describe the surface oxidation in AlCoCrFeNi HEA, we employed a stochastic cellular automata model that replicates the mesoscale structures that form. The model benefits from diffusion coefficients of the principal elements through the native oxides predicted by using molecular simulations. Through our examination of the oxidation behavior as a function of the alloy composition, we corroborated that the oxide scale growth is a function of the complex chemistry and resultant microstructures. The effect of heat treatment on these alloys is also simulated by using reconstructed experimental micrographs. When they are in a single-crystal structure, no segregation is noted for α-Al2O3 and Cr2O3, which are the primary scale-forming oxides. However, a coexistent separation between Al2O3 and Cr2O3 oxide scales with the Al-Ni- and Cr-Fe-rich regions is predicted when phase-separated microstructures are incorporated into the model.

32

Shi, Yunzhu, Rui Li, and Zhifeng Lei. "Influences of Synthetic Parameters on Morphology and Growth of High Entropy Oxide Nanotube Arrays." Coatings 13, no. 1 (December 27, 2022): 46. http://dx.doi.org/10.3390/coatings13010046.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Nanoscale and nanostructured materials have drawn great attention owing to their outstanding and unique properties. Enlightened by the study of “entropy-stabilized oxides”, nanotubes consisting of multi-component mixed metal oxides are developed, which formed on equi-atomic TiZrHfNbTa high-entropy alloy (HEA). However, the growth mechanism and how the oxidation conditions influence the nanotube growth and morphology remains unknown. In the present study, by controlling the anodization parameters (applied voltages and time) and bath compositions (fluoride concentration and water content), scanning electron microscope and transmission electron microscopy are conducted to reveal the morphological evolution. The present work uncovers how the synthetic parameters influence the tube growth and morphology formed on equi-atomic TiZrHfNbTa HEA, therefore gaining insight into the growth mechanism and the feasibility of controlling the morphology of multi-component oxide nanotubes.

33

Leong, Zhaoyuan, Pratik Desai, and Nicola Morley. "Can Empirical Biplots Predict High Entropy Oxide Phases?" Journal of Composites Science 5, no. 12 (November 26, 2021): 311. http://dx.doi.org/10.3390/jcs5120311.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy oxides are entropy-stabilised oxides that adopt specific disordered structures due to entropy stabilisation. They are a new class of materials that utilises the high-entropy concept first discovered in metallic alloys. They can have interesting properties due to the interactions at the electronic level and can be combined with other materials to make composite structures. The design of new meta-materials that utilise this concept to solve real-world problems may be a possibility but further understanding of how their phase stabilisation is required. In this work, biplots of the composition’s mean electronegativity are plotted against the electron-per-atom ratio of the compounds. The test dataset accuracy in the resulting biplots improves from 78% to 100% when using atomic-number-per-atom Z/a ratios as a biplot parameter. Phase stability maps were constructed using a Voronoi tessellation. This can be of use in determining stability at composite material interfaces.

34

Lin, Ling, Kai Wang, Raheleh Azmi, Junbo Wang, Abhishek Sarkar, Miriam Botros, Saleem Najib, et al. "Mechanochemical synthesis: route to novel rock-salt-structured high-entropy oxides and oxyfluorides." Journal of Materials Science 55, no. 36 (September 14, 2020): 16879–89. http://dx.doi.org/10.1007/s10853-020-05183-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Abstract A facile mechanochemical reaction at ambient temperature was successfully applied to synthesize novel single-phase rock-salt-structured high-entropy oxides, containing five, six and seven metal elements in equiatomic amounts. This synthesis approach overcomes the limitations of the commonly known synthesis procedures, which would result in multiple-phase compounds. Redox-sensitive elements, such as Fe2+ and Mn2+, can now be considered. The corresponding single-phase Li-containing high-entropy oxyfluorides were obtained by introducing LiF into the lattice using the same strategy. All materials show single-phase rock-salt structures with lattice parameters depending on the incorporated ion sizes. Solid solution states result in high configurational entropies, and all elements appear homogenously distributed over the whole cationic and anionic sublattice. The straightforward synthesis technique, combined with utilized simple binary oxide precursors, paves the way for a multitude of novel high-entropy oxide and oxyfluoride compounds. The compounds were studied by means of X-ray diffraction, transmission electron microscopy, energy-dispersive X-ray spectroscopy and Mössbauer spectroscopy.

35

Pitike, Krishna Chaitanya, Antonio Macias, Markus Eisenbach, Craig A. Bridges, and Valentino R. Cooper. "Computationally Accelerated Discovery of High Entropy Pyrochlore Oxides." Chemistry of Materials 34, no. 4 (February 7, 2022): 1459–72. http://dx.doi.org/10.1021/acs.chemmater.1c02361.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Gao, Yu, Yuzhi Liu, Haiyang Yu, and Donglei Zou. "High-entropy oxides for catalysis: Status and perspectives." Applied Catalysis A: General 631 (February 2022): 118478. http://dx.doi.org/10.1016/j.apcata.2022.118478.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Ushakov, Sergey V., Shmuel Hayun, Weiping Gong, and Alexandra Navrotsky. "Thermal Analysis of High Entropy Rare Earth Oxides." Materials 13, no. 14 (July 14, 2020): 3141. http://dx.doi.org/10.3390/ma13143141.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Phase transformations in multicomponent rare earth sesquioxides were studied by splat quenching from the melt, high temperature differential thermal analysis and synchrotron X-ray diffraction on laser-heated samples. Three compositions were prepared by the solution combustion method: (La,Sm,Dy,Er,RE)2O3, where all oxides are in equimolar ratios and RE is Nd or Gd or Y. After annealing at 800 °C, all powders contained mainly a phase of C-type bixbyite structure. After laser melting, all samples were quenched in a single-phase monoclinic B-type structure. Thermal analysis indicated three reversible phase transitions in the range 1900–2400 °C, assigned as transformations into A, H, and X rare earth sesquioxides structure types. Unit cell volumes and volume changes on C-B, B-A, and H-X transformations were measured by X-ray diffraction and consistent with the trend in pure rare earth sesquioxides. The formation of single-phase solid solutions was predicted by Calphad calculations. The melting point was determined for the (La,Sm,Dy,Er,Nd)2O3 sample as 2456 ± 12 °C, which is higher than for any of constituent oxides. An increase in melting temperature is probably related to nonideal mixing in the solid and/or the melt and prompts future investigation of the liquidus surface in Sm2O3-Dy2O3, Sm2O3-Er2O3, and Dy2O3-Er2O3 systems.

38

Teng, Zhen, Lini Zhu, Yongqiang Tan, Sifan Zeng, Yuanhua Xia, Yiguang Wang, and Haibin Zhang. "Synthesis and structures of high-entropy pyrochlore oxides." Journal of the European Ceramic Society 40, no. 4 (April 2020): 1639–43. http://dx.doi.org/10.1016/j.jeurceramsoc.2019.12.008.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Jiang, Sicong, Tao Hu, Joshua Gild, Naixie Zhou, Jiuyuan Nie, Mingde Qin, Tyler Harrington, Kenneth Vecchio, and Jian Luo. "A new class of high-entropy perovskite oxides." Scripta Materialia 142 (January 2018): 116–20. http://dx.doi.org/10.1016/j.scriptamat.2017.08.040.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Anand, G., Alex P. Wynn, Christopher M. Handley, and Colin L. Freeman. "Phase stability and distortion in high-entropy oxides." Acta Materialia 146 (March 2018): 119–25. http://dx.doi.org/10.1016/j.actamat.2017.12.037.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Sarkar, Abhishek, Qingsong Wang, Alexander Schiele, Mohammed Reda Chellali, Subramshu S. Bhattacharya, Di Wang, Torsten Brezesinski, Horst Hahn, Leonardo Velasco, and Ben Breitung. "High‐Entropy Oxides: Fundamental Aspects and Electrochemical Properties." Advanced Materials 31, no. 26 (March 6, 2019): 1806236. http://dx.doi.org/10.1002/adma.201806236.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Yin, Yinong, Fanfan Shi, Guo-Qiang Liu, Xiaojian Tan, Jun Jiang, Ashutosh Tiwari, and Baohe Li. "Spin-glass behavior and magnetocaloric properties of high-entropy perovskite oxides." Applied Physics Letters 120, no. 8 (February 21, 2022): 082404. http://dx.doi.org/10.1063/5.0081688.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The high-entropy concept has been recently proposed to be a promising paradigm to enhance the magnetocaloric properties of materials. Motivated by this, the magnetic properties and the magnetocaloric performance of two high-entropy perovskites (Dy1/4Ho1/4Er1/4Tb1/4)FeO3 and (Gd1/5Dy1/5Ho1/5Er1/5Tb1/5)FeO3 have been investigated. The magnetic measurements indicate that a spin-glass phase occurs at low temperatures in the high-entropy compounds, which is induced by the strong compositional disorder of rare-earth sublattice. The glassy state can lead to a sluggish magnetic transition and consequently a potential improvement in the magnetocaloric performance. Due to the increase in configurational entropy, large refrigerant capacity of 247 and 203 J/kg for a magnetic field change of 70 kOe is obtained in the (Gd1/5Dy1/5Ho1/5Er1/5Tb1/5)FeO3 and (Dy1/4Ho1/4Er1/4Tb1/4)FeO3 compounds, respectively. Our findings highlight the availability of spin order control through tuning the configurational entropy and demonstrate the key role of high-entropy design in enhancing the magnetocaloric properties of materials.

43

Edalati, Kaveh, Hai-Wen Li, Askar Kilmametov, Ricardo Floriano, and Christine Borchers. "High-Pressure Torsion for Synthesis of High-Entropy Alloys." Metals 11, no. 8 (August 11, 2021): 1263. http://dx.doi.org/10.3390/met11081263.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High-pressure torsion (HPT) is widely used not only as a severe plastic deformation (SPD) method to produce ultrafine-grained metals but also as a mechanical alloying technique to synthesize different alloys. In recent years, there have been several attempts to synthesize functional high-entropy alloys using the HPT method. In this paper, the application of HPT to synthesize high-entropy materials including metallic alloys, hydrides, oxides and oxynitrides for enhanced mechanical and hydrogen storage properties, photocatalytic hydrogen production and high light absorbance is reviewed.

44

Ting, Yin-Ying, and Piotr M. Kowalski. "(Best Student Presentation) Accurate First-Principle Study of High-Entropy Materials for Lithium-Ion Batteries." ECS Meeting Abstracts MA2023-01, no. 4 (August 28, 2023): 851. http://dx.doi.org/10.1149/ma2023-014851mtgabs.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The availability of well performing and cost efficient energy storage devices is of utmost importance for a smooth transition to sustainable energy. Lithium-ion batteries (LIBs) have been successfully commercialized and widely used in various portable devices. Functional materials with higher voltages and greater capacity are needed to further boost the energy density of these batteries. Recently, high-entropy materials (HEMs), with their unique structural characteristics and tunable functional properties, are actively investigated by several research groups [1]. High-entropy alloys (HEAs) with superior mechanical properties were first reported about a decade ago. Afterwards, the concept was adapted to high-entropy ceramic (HECs), such as high-entropy oxides, which are promising materials for electrodes as well as electrolytes in LIBs [2-4]. These materials usually contain more than 5 metals in a single disordered phase [5]. HECs are constructed with different type of cations and anions. Their structural and electronic complexity represent a challenge to the computational methods. We discuss the refined Density Functional Theory (DFT)-based methods that are able to successfully describe the electronic structure of these materials. The correct assignment of oxidation states of transition metals is one of the challenges, and we will show importance of correct description of d orbitals for achieving this task. Besides, we will also discuss the cycling performance, as well as thermodynamic aspects of selected HECs [6,7]. Last but not least, we will briefly discuss how accurate atomistic simulations could accelerate design of high-performance materials for Li-ion batteries of the future. [1] Zhang, R.-Z. & Reece, M. J. Review of high entropy ceramics: design, synthesis, structure and properties. J. Mater. Chem. A 7, 22148–22162 (2019). [2] Lun, Z. et al. Cation-disordered rocksalt-type high-entropy cathodes for Li-ion batteries. Nat. Mater. 20, 214–221 (2021). [3] Sarkar, A. et al. High entropy oxides for reversible energy storage. Nat Commun 9, 3400 (2018). [4] Jung, S.-K. et al. Unlocking the hidden chemical space in cubic-phase garnet solid electrolyte for efficient quasi-all-solid-state lithium batteries. Nat Commun 13, 7638 (2022). [5] Rost, C. M. et al. Entropy-stabilized oxides. Nat Commun 6, 8485 (2015). [6] Cui, Y. et al. High entropy fluorides as conversion cathodes with tailorable electrochemical performance. Journal of Energy Chemistry 72, 342–351 (2022). [7] Ting,Y. & Kowalski, P., Refined DFT+U method for computation of layered oxide cathode materials, Electrochimica Acta, in press.

45

Yan, Shengxue, Shaohua Luo, Liu Yang, Jian Feng, Pengwei Li, Qing Wang, Yahui Zhang, and Xin Liu. "Novel P2-type layered medium-entropy ceramics oxide as cathode material for sodium-ion batteries." Journal of Advanced Ceramics 11, no. 1 (November 10, 2021): 158–71. http://dx.doi.org/10.1007/s40145-021-0524-8.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

AbstractHigh-entropy oxides (HEOs) and medium-entropy oxides (MEOs) are new types of single-phase solid solution materials. MEOs have rarely been reported as positive electrode material for sodium-ion batteries (SIBs). In this study, we first proposed the concept of the application of MEOs in SIBs. P2-type 3-cation oxide Na2/3Ni1/3Mn1/3Fe1/3O2 (NaNMF) and 4-cation oxide Na2/3Ni1/3Mn1/3Fe1/3−xAlxO2 (NaNMFA) were prepared using the solid-state method, rather than the doping technology. In addition, the importance of the concept of entropy stabilization in material performance and battery cycling was demonstrated by testing 3-cation (NaNMF) and 4-cation (NaNMFA) oxides in the same system. Thus, NaNMFA can provide a reversible capacity of about 125.6 mAh·g−1 in the voltage range of 2–4.2 V, and has enhanced cycle stability. The capacity and decay law of the MEO batteries indicate that the configurational entropy (1.28 R (NaNMFA) > 1.10 R (NaNMF)) of the cationic system, is the main factor affecting the structural and cycle stability of the electrode material. This work emphasizes that the rational design of MEOs with novel structures and different electrochemically active elements may be the strategy for exploring high-performance SIB cathode materials in next-generation energy storage devices.

46

Wang, Lin, Quanqing Zeng, Zhibao Xie, Yun Zhang, and Haitao Gao. "High Temperature Oxidation Behavior of an Equimolar Cr-Mn-Fe-Co High-Entropy Alloy." Materials 14, no. 15 (July 30, 2021): 4259. http://dx.doi.org/10.3390/ma14154259.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The oxidation behavior of an equimolar Cr-Mn-Fe-Co high-entropy alloy (HEA) processed by 3D laser printing was investigated at 700 °C and 900 °C. The oxidation kinetics of the alloy followed the parabolic rate law, and the oxidation rate constant increased with the rising of the temperature. Inward diffusion of oxygen and outward diffusion of cations took place during the high-temperature oxidation process. A spinel-type oxide was formed on the surface, and the thickness of the oxide layer increased with the rising of experimental temperature or time. The exfoliation of the oxide layer took place when the test was operated at 900 °C over 12 h. During oxidation tests, the matrix was propped open by oxides and was segmented into small pieces. The formation of loose structures had great effects on the high-temperature oxidation resistance of the HEA.

47

Choi, Yun-Hyuk. "Electrocatalytic Activities of High-Entropy Oxides for the Oxygen Evolution Reaction." ECS Meeting Abstracts MA2023-02, no. 54 (December 22, 2023): 2604. http://dx.doi.org/10.1149/ma2023-02542604mtgabs.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

Electrocatalytic water-splitting hydrogen generation consists of the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER), where the four-electron-relevant OER is the rate-determining step. So far, there have been many efforts to substitute for the highly expensive noble-metal electrocatalysts (platinum, ruthenium or rhodium oxides, etc.). Transition-metal oxides based on Co, Ni, Mn, and V have been suggested as such alternatives, due to their low cost, high efficiency, and high stability. Recently, since the compositional diversity can provide a new breakthrough in that area, a high-entropy oxide (HEO) with five transition-metal cations has been suggested as a promising electrocatalyst toward the OER. In our studies, two kinds of HEOs were prepared and their OER activities were investigated. To begin with, for the (Mg0.2Fe0.2Co0.2Ni0.2Cu0.2)O, the effect of constituent cations on the OER activity was unveiled. Furthermore, a core cation driving the high OER activity was found. For it, the medium-entropy oxides (MEOs) with four cations are prepared by subtracting each cation (Mg, Fe, Co, Ni, or Cu) from the HEO, exhibiting homogeneous morphology, equiatomic composition, and single-phase rocksalt structure. As a result, it is found that the highest concentration of Co3+ in the MEO (w/o Cu) leads to the best OER activity, and thus Co3+ is the core ion driving the high OER activity. Furthermore, it is regarded that Cu2+ ions prevent the conversion of Co or Fe cations from 2+ to 3+ in the HEO and MEOs. Accordingly, maximizing the concentration of Co3+ within electrocatalysts is suggested as an effective design strategy for the high-efficiency electrocatalysts based on high or medium entropy materials. Secondly, the relationship between structure and OER activity was elucidated for the (Mg0.2Fe0.2Co0.2Zn0.2Cu0.2)O with a temperature-dependent rocksalt-to-spinel transition.

48

Samoilova, O. V., N. A. Shaburova, M. V. Sudarikov, and E. A. Trofimov. "High-temperature oxidation resistance of Al0.25CoCrFeNiSi0.6 high entropy alloy." Ferrous Metallurgy. Bulletin of Scientific , Technical and Economic Information 78, no. 11 (January 10, 2023): 978–86. http://dx.doi.org/10.32339/0135-5910-2022-11-978-986.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

High entropy alloys (HEAs) are a relatively new type of alloys and, unlike traditional alloys based on one or two main components, HEAs include five or more components in close to equimolar ratios. These alloys are currently considered as promising materials for the manufacture of coatings on parts operating in difficult operating conditions – parts of gas turbines, turbojet and jet engines, etc. The possible use of HEAs at high temperatures makes it relevant to assess the ability of HEAs to resist high-temperature oxidation. In the course of this work, the behavior of the HEA of the composition Al0.25CoCrFeNiSi0.6 was studied during isothermal exposure for 10 hours for temperatures of 700 and 1000 °C in air. The kinetic curves of oxidation were constructed, on the basis of which it was established that the spe-cific weight gain after 10 hours of exposure at 700 °C was 1 mg/cm2, at 1000 °C – 4 mg/cm2. Samples before and after oxidation were studied using scanning electron microscopy, X-ray spectral microanalysis, and X-ray phase analysis. It has been established that the phase composition of the oxide film after exposure at 700 °C is represented only by Al2O3 and Cr2O3 oxides, while after exposure at 1000 °C were found Al2O3, Cr2O3, SiO2, Al2SiO5, Fe2SiO4, Fe3O4, CoFe2O4 and FeCr2O4. The use of the Al0.25CoCrFeNiSi0.6 HEA with the ratio Si/Al = 2.4 under operating conditions at elevated temperatures can be considered inappropriate.

49

Barbarossa, S., M. Murgia, R. Orrù, and G. Cao. "Processing Conditions Optimization for the Synthesis and Consolidation of High-Entropy Diborides." Eurasian Chemico-Technological Journal 23, no. 3 (November 10, 2021): 213. http://dx.doi.org/10.18321/ectj1104.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Abstract:

The fabrication by Spark Plasma Sintering (SPS) of bulk high entropy ceramics from powders obtained by Self-propagating High temperature Synthesis (SHS) is addressed in this work. The effect produced by the introduction of 1 wt.% of graphite to the powders before SPS is investigated under different temperature conditions. The final density and composition of sintered (Hf0.2Mo0.2Zr0.2Ti0.2Ta0.2)B2 and (Hf0.2Mo0.2Zr0.2Ti0.2Nb0.2)B2 ceramics are found to be negatively affected by the presence of oxide impurities in the powders. While product composition can be progressively improved when the temperature is increased from 1800 to 1950 °C, residual porosities remain relatively high if using additive-free powders. In contrast, the introduction of 1 wt.%C markedly allows for oxides elimination by carbothermal reduction mechanism. Products consolidation is correspondingly enhanced so that relative densities of about 97% are attained. Other than the latter effect, surface oxides removal also makes powders more reactive, thus the synthesis of single-phase products is promoted. In particular, fully homogeneous (Hf0.2Mo0.2Zr0.2Ti0.2Ta0.2)B2 ceramics are obtained at relatively lower temperature conditions (1850 °C).

50

Ma, Jinxu, Kepi Chen, Cuiwei Li, Xiaowen Zhang, and Linan An. "High-entropy stoichiometric perovskite oxides based on valence combinations." Ceramics International 47, no. 17 (September 2021): 24348–52. http://dx.doi.org/10.1016/j.ceramint.2021.05.148.

Full text

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'High entropy oxides'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles