Academic literature on the topic 'High entropy oxides'
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Journal articles on the topic "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.
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.
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.
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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.
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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.
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.
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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.
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
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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.
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.
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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.
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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.
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.
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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.
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.
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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.
Dissertations / Theses on the topic "High entropy oxides":
1
Sarkar, Abhishek Verfasser], Horst [Akademischer Betreuer] [Hahn, and Jürgen [Akademischer Betreuer] Janek. "High Entropy Oxides: Structure and Properties / Abhishek Sarkar ; Horst Hahn, Jürgen Janek." Darmstadt : Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1222674432/34.
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Sarkar, Abhishek [Verfasser], Horst [Akademischer Betreuer] Hahn, and Jürgen [Akademischer Betreuer] Janek. "High Entropy Oxides: Structure and Properties / Abhishek Sarkar ; Horst Hahn, Jürgen Janek." Darmstadt : Universitäts- und Landesbibliothek, 2020. http://d-nb.info/1222674432/34.
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Osenciat, Nicolas. "Propriétés de transport dans les oxydes à haute entropie." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF005.
Abstract:
Ces travaux de thèse visent à estimer le potentiel d'un nouveau matériau pour des applications d'électrolyte solide dans des accumulateurs électrochimiques tout-solide et/ou dans des micro-batteries. Ce nouveau composé, qui possède une conductivité ionique du Li+ et du Na+ remarquable, appartient à une nouvelle classe d'oxydes découverts récemment par Rost et al. (Nature Communication, 2015). Cette nouvelle famille est formée suite à la stabilisation par entropie de configuration à haute température d'une phase simple à partir d'un mélange complexe d'oxydes binaires (dans notre cas, en une structure de type NaCl). Nous avons étudié les mécanismes de compensation de charges opérant lors de la synthèse de la série de composés (MgCoNiCuZn)1−xLixO et l'influence de leur composition sur leurs propriétés de conductivité ionique. Nous avons tenté d'utiliser la méthode originale de Cold Sintering Process pour densifier ces composés à basse température, sans parvenir à obtenir des céramiques exempt de défaut. Enfin, nous avons également développé et décrit structuralement, ainsi qu'électrochimiquement, un nouveau matériau d'électrode négative, potentiellement compatible avec ces oxydes stabilités par entropie, le titanate de lithium multi-cationique Li2(Mg,Co,Ni,Cu,Zn)Ti3O8The aim of this thesis is to assess the potential of a new material for solid-state electrolyte applications in all-solid-state batteries and/or micro-batteries. This new compound, which exhibits remarkable Li+ and Na+ ionic conductivity, belongs to a new class of oxides, recently discovered by Rost et al. (Nature Communication, 2015). This new family is formed through configuration entropy stabilisation, at high temperature, into a simple single phase, from a complex mixture of binary oxides (in our case NaCl-Rocksalt structure). We have studied the charge compensation mechanisms involved in the synthesis of the (MgCoNiCuZn)1−xLixO series and the influence of their composition on their ionic conductivity properties. We have attempted to densify these compounds at low temperature using the original Cold Sintering Process, without succeeding in obtaining defect-free ceramics. Finally, we have also developed and described the crystallographic structure and the electrochemical behaviour of a new anode material (possibly compatible with these entropy-stabilised oxides), the Li2(Mg,Co,Ni,Cu,Zn)Ti3O8 multicationic lithium titanate
4
Sarkar, Abhishek. "High Entropy Oxides: Structure and Properties." Phd thesis, 2020. https://tuprints.ulb.tu-darmstadt.de/14345/1/Doctoral_thesis_Abhishek_Sarkar.pdf.
Abstract:
Since the origin of humankind numerous approaches have been employed to develop new materials. Of these approaches, changing the composition of a given system, typically referred as alloying for metallic and doping for non-metallic systems, is undoubtedly the most common way of designing new materials. Conventionally, alloying or doping implies introduction of relatively small amounts of secondary elements to a base system. The base system typically consists of one major component, e.g., Fe for steels, while in yttria-stabilized zirconia, ZrO2 is considered as the base system. The concept of high entropy materials (HEMs) can be considered as an extreme adaption of alloying or doping, where five or more elements all in (nearly) equal proportions are incorporated into a system. Hence, there is no base element (“baseless”) as such in HEMs. Their unexpected tendency to form single phase solid solutions despite the high chemical complexity makes HEMs unique. Essentially, the combination of several elements in near equiatomic proportion enhances the configurational entropy of HEMs. It is believed, in some cases proven, that this enhanced configurational entropy drives the formation of a single phase solid solution. Due to these distinctive features, the high entropy based design concept is often considered as an original approach, and not a mere extension to alloying or doping.
The subject of studies in this doctoral thesis is high entropy oxides (HEOs). HEOs are phase-pure solid solutions arising from the inclusion of five or more elements into the cationic sub-lattice(s) of oxide materials. Building upon the initial reports on HEOs, the first one published in 2015, the main objective of this work is to investigate the unexplored regions of oxide compositions and structures offered by the high entropy based design approach.
The initial task was the identification and optimization of a suitable synthesis technique for fabrication of HEOs with rocksalt and fluorite structures. In this regard, several techniques, each possessing certain advantages and disadvantages, were explored. Out of these considered ones, aerosol based nebulized spray pyrolysis (NSP) was found to be the most versatile technique for preparation of HEOs on a laboratory scale and was used as the primary synthesis tool in this thesis. The exploration of new HEO systems with different compositions and crystallographic structures was the next challenge. Perovskite type HEOs (P-HEOs) were developed, in which up to 10 different cations in equiatomic proportion can be homogeneously incorporated into a single-phase orthorhombic structure. Besides the synthesis aspect, emphasis was placed on comprehensive understanding of the underlying phase stability mechanisms in different crystal types of HEOs, such as rocksalt, fluorite and perovskite. It was observed that the governing principles were rather distinct for different types of HEOs. In some cases, such as in rocksalt-HEOs (R-HEOs), an entropy-driven phase transformation is dominant, whereas in the other HEOs, aspects like tolerance factors, oxidation state of the cations and related internal charge compensations play determining roles.
Apart from these structural investigations, a major part of this doctoral work is dedicated to explore the functional properties of HEOs. Oxides, in general, show rich structure-composition-property relationships. Hence, the properties of HEOs were explored based on their crystal structure and composition characteristics. Three different classes of properties were investigated: electrochemical, optical and magnetic. Transition metal (TM) based R-HEO was probed as electrode material for secondary Li-ion batteries (LIBs). Highly reversible lithium storage capacities (above 600 mAh/g for more than 900 cycles) were observed. A major part of the capacity is drawn from electrochemical reactions below 1 V (vs Li+/Li), which warrants its possible use as an anode in LIBs. Importantly, a unique electrochemical reaction mechanism, possibly stemming from an entropy effect, was discovered. Rare earth (RE) based fluorite-HEOs (F-HEOs), on the other hand, showed interesting optical properties like narrow band gap of ∼2 eV, which could be reversibly tuned (from 2 – 3.2 eV) by conducting heat treatments under different atmospheres. Element specific techniques, like X-ray absorption spectroscopy (XAS) and energy electron loss spectroscopy (EELS), allowed to disentangle the individual effects of the constituent cations in complex F-HEOs and identify the relevant features in the electronic band structure underpinning the observed reversible changes in the optical behavior. The reason behind the change in band gap is closely associated with the presence of redox active multivalent cations, like Pr3+,4+, which result in the formation of intermediate unoccupied energy states. Finally, P-HEOs comprising of multiple RE cations on the A-site and/or multiple TM cations on the B-site exhibited an interesting interplay between the magnetic exchange interactions and the high degree of chemical disorder in the systems. Additional ferromagnetic interactions in otherwise predominant antiferromagnetic environment leading to exchange anisotropy were observed in phase-pure P-HEOs, wherein the former could be attributed to either small ferromagnetic clusters or spin canting.
In brief, this doctoral work highlights the versatility of the high entropy based design concept in oxides by demonstrating the structure-property relationships in three different crystal structure types of HEOs. As the research on HEOs is still in its early state, a plethora of fundamental aspects of HEOs are yet to be explored to assess their full potential for practical applications.
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張毓倫. "Study on High-Entropy Oxides Synthesized by Nitrate-Solution Method." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/95510250685674090556.
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Yeh, Kuan-Cheng, and 葉冠成. "On the conductivity of high-entropy oxides prepared by nitrate solution method." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/54976830998525260702.
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任德育. "Study on conductivity of high-entropy oxides prepared by solid-state reaction method." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/62206179086891984028.
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CHIANG, CHIA-LIANG, and 江家樑. "Optical Properties of RF-Sputtered High-Entropy Alloy CrNiTiSiZr Oxide Thin Films." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/43m7sb.
Abstract:
碩士輔仁大學
物理學系碩士班
106
In this study, the high-entropy alloy CrNiTiSiZr filmsare coated by using an RF sputtering system. The optical properties and compositions of high-entropy alloy CrNiTiSiZr films are observed under different deposition pressures. It is expected that high-entropy alloy CrNiTiSiZr films could be used on the optical system in the future. The samples were illustrated by ellipsometry, spectrometer, X-ray diffractometry (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The optical properties of the films were analyzed for their refractive index, absorption, and binding energy. The results show that the high-entropy alloy CrNiTiSiZr film deposited at the argon flow rate of 30 sccm has the maximum variation in refractive index and extinction coefficient as increasing the visible wavelength. The oxygen composition in the high-entropy alloy CrNiTiSiZr becomes less as decreasing the argon flow rate. The optical energy gap is directly proportional to the oxygen content. However, the XRD peaks didn’t change apparently as increasing the argon flow rate. When the film deposited at the argon flow rate 20 sccm, it contains the minimum oxygen composition of (26.36 at.%) and the minimum energy gap of (3.97 eV).The transmittance is also affected by the oxygen content, refractive index and extinction coefficient of the films. Such as, the film deposited at argon flow of 30 sccm has the lowest transmittance.The absorption is the largest at argon flow of 30 sccm.
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Aliyu, Ahmed. "Microstructure and Electrochemical Properties of Electrodeposited High Entropy Alloys Coatings." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5540.
Abstract:
High entropy alloys (HEA) are composed of five or more alloying elements in a nearly equi-atomic ratio. HEAs exhibit high oxidation and corrosion resistance behaviour. In this work, HEA coatings were electrodeposited over mild steel substrate from an aqueous electrolyte bath. Microstructure-corrosion property correlation for as-deposited pristine HEA and HEA-graphene oxide (GO) composite coatings was examined. Four different HEA coating systems were investigated: CrNiCoFeCu, CrNiCoFeMn, AlNiCoFeCu, and AlCrNiCoFeCu HEA coatings. Corrosion behaviour and passive film constitution of CrNiCoFeCu and CrNiCoFeMn coatings were compared, and it was observed that the formation of relatively stable protective Cr, Co, and Mn oxide corrosion products on the surface of the CrNiCoFeMn coating enhanced the corrosion resistance of this coating. In contrast, the formation of Fe, Cr, and Cu oxide corrosion products on the surface of CrNiCoFeCu coating were de-stabilized by the inter-dendritic segregation of the Cu-rich phase leading to the lower corrosion resistance of the CrNiCoFeCu coating. In the case of AlNiCoFeCu and AlCrNiCoFeCu coating, the effect of Cr on the evolution of oxide phase in Al-containing HEA coatings was compared. The formation of a denser and more stable protective oxide layer on the surface of AlCrNiCoFeCu HEA coating resulted in better corrosion resistance performance compared to the AlNiCoFeCu HEA coating, which had a lesser stable and defective protective oxide layer. It was observed that Cr facilitates the formation of other metallic oxides in the passive film, which enhanced its ability to reduce ionic diffusion and improve the corrosion resistance of the Cr containing AlCrNiCoFeCu HEA coating. In the case of CrNiCoFeCu HEA-GO composite coatings, with GO addition, the corrosion current density and corrosion rate reduced. while, the polarization resistance increased, indicating an enhancement in the corrosion resistance property of the CrNiCoFeCu HEA-GO coatings with increase in the GO content. The microstructural characterization of the coatings showed that GO addition into the CrNiCoFeCu matrix resulted in two distinct microstructural changes; one was increase in the Cr-rich phase, and the other was the formation of Cu-rich and Cr-rich layer over the coating surface which can facilitate the formation of the protective oxide film that can hinder the penetration of the electroactive media. These factors, along with the impermeability imparted by GO resulted in enhancement in the corrosion resistance of the CrNiCoFeCu HEA-GO coatings. In the case of CrNiCoFeMn HEA-GO composite coating, morphology of the coating showed that the relative smoothness and compactness of the coatings increased with GO additions. A significant improvement in the corrosion resistance in terms of reduction in the corrosion current density and corrosion rate and increased corrosion potential and polarization resistance was recorded for the GO containing CrNiCoFeMn HEA coatings, which implied enhancement in the corrosion resistance performance of the coatings. Microstructural characterization of CrNiCoFeMn HEA coatings revealed that the GO addition resulted in distinct microstructural changes; with GO addition, the microstructure transformed from a nearly homogenous microstructure to a microstructure containing FeCoNi rich regions embedded in an Mn-Cr rich matrix. The formation of a strongly oxidizing matrix capable of forming relatively stable protective oxide layers and impermeability imparted by the GO were accounted for the observed enhancement in the corrosion resistance of the CrNiCoFeMn HEA-GO composite coatings as compared to the pristine CrNiCoFeMn HEA coating. In the case of AlNiCoFeCu HEA-GO composite coatings, the as-deposited AlNiCoFeCu HEA coating exhibited a granular morphology, which became finer and relatively more compact with increasing in the GO amount. Structural characterization revealed a mixture of BCC and FCC phases, with a fraction of the FCC phase increasing with GO. The coatings' electrochemical properties showed that AlNiCoFeCu HEA-GO composite coatings' corrosion rate progressively decreased with increase in the GO content. Microstructural characterization revealed a highly Al-rich matrix phase and Co, Ni, Cu, and Fe containing dendritic phase in the coating microstructure for the pristine coating. With the addition of GO, the coating microstructure progressively became more compositionally homogeneous. Al distribution between the matrix and dendritic phases became more uniform. Microstructural homogenization reduced the extent of galvanic coupling between phases and uniform distribution of Al, which can form stable and protective alumina phase along with the impermeability properties of GO enhanced the corrosion resistance performance of the AlNiCoFeCu HEA-GO composite coatings when compared to pristine AlNiCoFeCu HEA coating. In the case of AlCrNiCoFeCu HEA-GO composite coatings, the corrosion resistance of the AlCrNiCoFeCu HEA-GO composite coatings was higher than the AlCrNiCoFeCu HEA coating without GO. Corrosion resistance gradually increased with increase in the GO content in the coating. Detailed microstructural characterization revealed that GO addition facilitated microstructural and compositional homogeneity, eliminating localized corrosive attack due to elemental segregation induced galvanic coupling, thereby increasing the corrosion resistance for the AlCrNiCoFeCu HEA-GO composite coatings.
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Patel, Ranjan Kumar. "Electronic behavior of epitaxial thin films of doped rare-earth nickelates." Thesis, 2023. https://etd.iisc.ac.in/handle/2005/6129.
Abstract:
Rare-earth nickelates (RENiO3), a family of transition metal oxides, exhibit a complex phase diagram involving electronic, magnetic, and structural phase transitions. While LaNiO3 remains paramagnetic, metallic down to very low temperature, RENiO3 members with RE=Nd, Pr exhibit simultaneous metal-insulator transition (MIT), paramagnetic to antiferromagnetic transition, structural phase transition and a bond disproportionation (BD) transition as a function of temperature. The other members of the series such as EuNiO3, SmNiO3, etc. first undergo simultaneous MIT, BD, and structural phase transition and further becomes antiferromagnetic upon lowering the temperature. Understanding the origin of the MIT in this family remains a challenging problem and has attracted a lot of attention in recent times. The MIT temperature can be tuned by a variety of parameters such as chemical doping, pressure, epitaxial strain, light, etc. In this thesis, we have grown epitaxial thin films of doped rare-earth nickelates and investigated their electronic and magnetic behavior using several experimental techniques, including synchrotron-based measurements.
In the first part, we have investigated Ca2+ (divalent) and Ce4+ (tetravalent) doped NdNiO3 thin films. Doping with divalent ions at the Nd sites introduces holes, whereas doping with tetravalent ions introduces electrons, resulting in a change in the formal valence of Ni. Both electron and hole doping suppress the insulating phases with asymmetric suppression rates for the metal-insulator phase transition. We have shown that the effective charge transfer energy changes with carrier doping and the formation of the BD phase is not favored above a critical doping, suppressing the insulating phase. Our research clearly shows that the appearance of BD mode is critical for the appearance of MIT in RENiO3 family.
In the second part, we have investigated rare-earth nickelate in high entropy oxide (HEO) form. HEOs are defined as a class of materials containing equimolar or nearly equimolar portions of five or more elements stabilizing in a single phase. HEOs have been explored in recent years to achieve tunable properties in unexplored parts of the complex phase diagram. However, epitaxial stabilization of such multi-element systems is challenging, and it is unknown how epitaxial strain will affect the electronic and magnetic behavior of HEO. We have been able to grow (LaPrNdSmEu)0.2NiO3 [(LPNSE)NO] thin films on different substrates having different epitaxial strains. We have shown that, in spite of having multi-element and strong disorder at the RE site, the average tolerance factor determines the electronic and magnetic properties. We further studied the strain effect on MIT of those HEO thin films. We have observed that (LPNSE)NO film grown under tensile strain (substrates: NdGaO3 and SrTiO3) exhibits a metal-insulator transition. We have found that this transition can be completely suppressed by compressive strain exerted by SrLaAlO4 substrate. Surprisingly, HEO film, grown on SrPrGaO4 substrate, where the strain is almost negligible, does not exhibit any MIT. We have further demonstrated that the octahedral rotation pattern of the substrate governs the octahedral rotation and Ni-O-Ni bond angle of the epitaxial thin films, which in turn controls the MIT.
In the third part, we have explored (LPNSE)NO thin films as electrocatalysts. Oxygen evolution reaction (OER) is a key process in several alternative energy generation platforms such as solar and electric driven water splitting, fuel cells, rechargeable metal-air batteries, etc. We have investigated the thickness dependent OER of (LPNSE)NO thin films and found that the increase of film thickness results in higher OER activity. X-ray absorption spectroscopy measurements find an increase in Ni d-O p covalency and a decrease in charge transfer energy with the increase in film thickness. These facilitate higher charge transfer between Ni and surface adsorbates, resulting in higher OER activity.
Book chapters on the topic "High entropy oxides":
1
Gautam, Ashwani, and Md Imteyaz Ahmad. "Stability Landscape and Charge Compensation Mechanism for Isovalent and Aliovalent Substitution in High Entropy Oxides." In High Entropy Materials, 78–90. Boca Raton: CRC Press, 2024. http://dx.doi.org/10.1201/9781003391388-7.
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Musicó, Brianna L., Cordell J. Delzer, John R. Salasin, Michael R. Koehler, and Claudia J. Rawn. "Experimental Characterization of High-Entropy Oxides with In Situ High-Temperature X-Ray Diffraction Techniques." In High-Entropy Materials: Theory, Experiments, and Applications, 413–34. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77641-1_9.
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Yang, Yu, Tongxiang Ma, Mengjun Hu, Pengjie Liu, Liangying Wen, Liwen Hu, and Meilong Hu. "Preparation of CoCrFeNi High-Entropy Alloy via Electro-Deoxidation of Metal Oxides." In TMS 2020 149th Annual Meeting & Exhibition Supplemental Proceedings, 1593–601. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-36296-6_147.
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Kumari, Priyanka, Amit K. Gupta, Shashi Kant Mohapatra, and Rohit R. Shahi. "Nanocrystalline High Entropy Alloys and Oxides as Emerging Materials for Functional Applications." In Nanomaterials, 145–76. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-7963-7_6.
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Sarkar, Abhishek, Horst Hahn, and Robert Kruk. "High Entropy Oxides." In Reference Module in Materials Science and Materials Engineering. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-12-819728-8.00096-6.
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Pu, Yuguang, Saifang Huang, and Peng Cao. "High-entropy oxides for energy storage and catalysis." In Advanced Ceramics for Energy Storage, Thermoelectrics and Photonics, 209–36. Elsevier, 2023. http://dx.doi.org/10.1016/b978-0-323-90761-3.00015-2.
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Mebratie Bogale, Gedefaw, and Dagne Atnafu Shiferaw. "Iron-Based Superconductors." In High Entropy Materials - Microstructures and Properties [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.109045.
Abstract:
Superconductivity is the phenomenon of vanishing an electrical resistivity of materials below a certain low temperature and superconductors are the materials that show this property. Critical temperature is the temperature below which superconducting state occurs. Based on temperature superconductors can be grouped into high-temperature superconductors and low-temperature superconductors. Based on the mechanism, they can be grouped into conventional and unconventional superconductors. Based on magnetism superconducting materials can also be separated into two groups: type-I and type-II superconductors. In this chapter, we will discuss superconductivity, the Meissner effect, type-I and type-II superconductors, convectional and unconvectional superconductors, heavy fermions, cuprates, iron-based superconductors, and high entropy alloy superconductors. High-entropy alloys (heas) are defined as alloys containing at least five elements with concentrations between 5 and 35 atom%. The atoms randomly distribute on simple crystallographic lattices, where the high entropy of mixing can stabilize disordered solid-solution phases with simple structures. The superconducting behavior of heas is distinct from copper oxide superconductors, iron-based superconductors, conventional alloy superconductors, and amorphous superconductors, suggesting that they can be considered as a new class of superconducting materials.
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Saadat Arif, Huseynova, Panakhova Nushaba Farkhad, Orujova Pusta Ali, Hajiyeva Nurangiz Nizami, Hajiyeva Adila Sabir, Mukhtarova Sevinj Nabi, and Agayeva Gulnaz Telman. "Endothelial Dysfunction and Intestinal Barrier Injury in Preterm Infants with Perinatal Asphyxia." In Maternal and Child Health [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.110352.
Abstract:
Perinatal asphyxia is one of the most frequent causes of perinatal morbidity, accounting for approximately 23% of neonatal deaths worldwide. Fetuses that suffer from hypoxia-ischemia are at high risk of developing multiorgan dysfunction, including the gut. Hypoxie-induced gut injury may result in adverse clinical outcomes, such as feeding intolerance and necrotizing enterocolitis. Increased permeability and subsequently an enhanced entry of bacteria and endotoxins into the systemic circulation can contribute to endotoxin aggression and further trigger numerous diseases. The aim of study is to investigate the effect of perinatal asphyxia on the integrity of the intestinal barrier and the state of antiendotoxin immunity. The study included preterm neonates exposed to perinatal asphyxia, who were comparable with non-asphyxiated infants. The concentrations of intestinal mucosa barrier injury markers (intestinal fatty acid binding protein, liver fatty acid protein, lipopolysaccharide binding protein), neurospecific proteins (neurospesific enolase, NR-2 antibodies), and also endothelial dysfunction markers (endothelin-1, nitric oxide) were determined in serum of included neonates on day of 1 and 7. The high risk of intestinal mucosal injury in newborn exposed to perinatal asphyxia decreases the level of antiendotoxic immunity and should be considered as an unfavorable factor for sepsis.
Conference papers on the topic "High entropy oxides":
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Riley, Christopher, Stanley Chou, Datye Abhaya, and Andrew De La Riva. "Catalytic High Entropy Oxides Stabilized with Vacancy Contributed Configurational Entropy." In Proposed for presentation at the Materials Research Society Spring held April 17-23, 2021 in virtual, virtual, US. US DOE, 2021. http://dx.doi.org/10.2172/1862768.
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Lowry, Daniel, Mia Blea-Kirby, Nichole Valdez, Joseph Boro, Mark Rodriguez, Eric Coker, and Sean Bishop. "Designing High Entropy RE2Zr2O7 Oxides Through Composition Considerations." In Proposed for presentation at the Ultra-High Temperature Ceramics: Materials for Extreme Environment Applications V held June 5-8, 2022 in Snowbird, Utah United States. US DOE, 2022. http://dx.doi.org/10.2172/2003437.
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Vakilifard, H., H. Shahbazi, A. C. Liberati, R. B. Nair, C. Moreau, and R. S. Lima. "High Entropy Oxides as Promising Materials for Thermal Barrier Topcoats—A Review." In ITSC 2023. ASM International, 2023. http://dx.doi.org/10.31399/asm.cp.itsc2023p0667.
Abstract:
Abstract Multi-layered thermal barrier coatings (TBCs) are deposited on gas-turbine metallic components to protect them against high temperatures, oxidation, and corrosion. However, TBCs have limited working temperatures and lifetimes due to their material properties. Several approaches are being tested to increase TBC topcoats' phase stability and properties. Increasing entropy to stabilize phases is a concept introduced in 2004 and required decreasing the Gibbs free energy. Many high-entropy ceramics are being developed for structural and functional applications, and high-entropy oxides (HEOs) are promising TBC ceramics due to their unique characteristics. HEOs are single-phase solid solutions that contain five or more cations, usually a mixture of transition metals and rare earths. Due to the cocktail effect, the final material has a different behavior from its constituents, making it a viable method to improve the properties of traditional materials. Generally, high entropy materials are characterized by three additional phenomena: sluggish diffusion, severe lattice distortion, and high entropy. A review of possible improvements in the lifetime of TBC topcoats using different HEOs in terms of their composition, properties, and stability are presented here. Different HEOs are then examined and various thermophysical properties, high-temperature stability, and sintering resistance are discussed.
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Riley, Christopher, Abhaya Datye, and Stanley Chou. "Designing high entropy oxides (HEOs) as effective catalysts for pollution abatement." In Proposed for presentation at the 2020 MRS Fall Meeting. US DOE, 2020. http://dx.doi.org/10.2172/1831010.
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Anwer, Zahid, Jef Vleugels, and Shuigen Huang. "High Entropy Carbide - Ni Based Cermets Prepared By In-Situ Carbothermal Reduction Of Transition Metal Oxides." In Euro Powder Metallurgy 2023 Congress & Exhibition. EPMA, 2023. http://dx.doi.org/10.59499/ep235763795.
Abstract:
Fully dense high entropy carbide (Nb0.2Ta0.2V0.2Ti0.2W0.2)C - 10.64 wt.% Ni-based cermets were prepared by in-situ carbothermal reduction of mixtures of transition metal oxides from Group IV, V and VIB by a one-step reactive sintering technique. The molar ratio of metal oxides and graphite in the starting powder mixtures was varied and the evolution of the microstructure, grain size and morphology of the HEC phase was studied in detail. The in-situ carbothermal reduction of oxides resulted in a high entropy carbide phase with a homogeneous backscattered electron atomic number contrast with an extremely faint core-rim structure. This study demonstrates a facile and cost-effective alternative synthesis approach to prepare chemically complex high entropy carbide based cermets in a one-step pressureless sintering cycle. The two-phase HEC-Ni cermets exhibits an excellent hardness around 16.5 GPa and an acceptable fracture toughness around 7.5 MPa.m1/2.
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Kenyi, A., R. Bhaskaran Nair, and A. McDonald. "Towards Highly Durable High Entropy Alloy (HEA) Coatings Using Flame Spraying." In ITSC2022. DVS Media GmbH, 2022. http://dx.doi.org/10.31399/asm.cp.itsc2022p0827.
Abstract:
Abstract High entropy alloys (HEAs) constitute a new class of advanced metallic alloys that exhibit exceptional properties due to their unique microstructural characteristics. HEAs contain multiple (five or more) elements in equimolar or nearly equimolar fractions compared to traditional alloy counterparts. Due to their potential benefits, HEAs can be fabricated with thermal spray manufacturing technologies to provide protective coatings for extreme environments. In this study, the AlCoCrFeMoW and AlCoCrFeMoV coatings were successfully developed using flame spraying. The effect of W and V on the HEA coatings were investigated using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and micro-hardness testing. Furthermore, performance of the coating under abrasive loading was investigated as per ASTM Standard G65. Microstructural studies showed different oxides with solid-solution phases for all the HEA coatings. Hardness results were higher for the AlCoCrFeMoV coatings followed by AlCoCrFeMoW and AlCoCrFeMo coatings. Lower wear rates were achieved for the AlCoCrFeMoV coatings compared to AlCoCrFeMoW and AlCoCrFeMo coatings. The evolution of multiple oxide phases and underlying microstructural features improved the resistance to abrasive damage for the AlCoCrFeMoV coatings compared to other HEA coatings. These results suggest that the flame-sprayed HEA coatings can be potential candidates for different tribological interfaces while concurrently opening new avenues for HEA coating utilization.
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Chikhradze, Nikoloz, Nikoloz Jalabadze, Mikheil Chikhradze, Davit Tsverava, and George Janikashvili. "SHOCK-WAVE SYNTHESES OF HIGH ENTROPY ALLOYS IN Fe-W-Al-Ti-Ni-B-C SYSTEM." In 23rd SGEM International Multidisciplinary Scientific GeoConference 2023. STEF92 Technology, 2023. http://dx.doi.org/10.5593/sgem2023/6.1/s24.10.
Abstract:
High-Entropy Alloys (HEAs) have higher mixing entropy than the conventional alloys and intermetallic compounds and form the stabile solid solutions with disordered structure. They exhibit unique and special properties, in particular high hardness, wearresistance, significantly high strength, structural stability, good corrosion, and oxidation-resistance. HEAs �exotic�, core effects are followings: high configurational entropy; sluggish diffusion; lattice distortion and cocktail effect. At the current stage, the volume of investigations towards high entropy materials extended from single-phase solid solution structure to multi-phase structures, containing solid solution phases, intermetallic compounds, oxides, borides etc. Promised direction in this field are the high-entropy composites, prepared based on the HEAs matrix- reinforced with hard ceramic compounds. Accordingly, there is a huge potential to find new properties in the field of multi-component high-entropy nanostructure materials. The Fe-W-Al-Ti-Ni�BC composition considered in article for fabrication of HEA�s. The content of elements in blend were determined on the base of phase diagrams available in scientific databases. The planetary ball mill is used for Mechanical Alloying (MA) and nanopowder production. Industrial explosives are used for shock wave generation and consolidation of the blend. The MA blend charged in low carbon cylindrical steel tube container and closed both sides. A cardboard box with blend container was filled with explosives and detonated. The phase analyses and structure-property of obtained bulks HEA compacts investigated. Results of investigations discussed and presented in the paper.
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Ilinich, Margarita, Xiao Huang, and Kourosh Zanganeh. "Oxidation Performance of Fe-Ni-Co-Cr-Mn High Entropy Alloy and its Al-Containing Variants in Supercritical CO2." In ASME Turbo Expo 2023: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/gt2023-101647.
Abstract:
Abstract In this study, a new material type, known as high entropy alloy (HEA), is being evaluated for use in supercritical CO2 (sCO2) Brayton power cycle. This cycle is a promising power generation technology that offers an increased efficiency and smaller footprint compared to the conventional Rankine steam cycle. However, the construction of components that operate in the high temperature and pressure regions of the cycle requires the use of expensive high-performance alloys such as Inconel 740H and Incoloy 800HT. As an alternative to these alloys, three compositions of HEAs are evaluated, namely, FeNiCoCrMn (HEA-1), FeNi1.5CoCrMnAl0.5 (HEA-2), FeNi1.5CoCrAl0.5 (HEA-3). The alloy samples were exposed to sCO2 at 700 °C, 20 MPa for 600 hours. They were then evaluated through weight measurements and characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and x-ray diffraction (XRD). The results showed that HEA-3 outperformed the two other compositions. It experienced an impressively low mass gain of 0.04 mg/cm2, compared to 0.65mg/cm2 and 0.25 mg/cm2 for HEA-1 and HEA-2, respectively. The lack of Mn enabled HEA-3 to form protective Cr2O3 oxides, whereas the other two compositions formed porous oxides containing MnO and Mn3O4. Furthermore, the results showed that HEA-3 has the potential to outperform many conventional superalloys being evaluated for sCO2 applications. Additional test campaign has been planned to study the effects of prolonged exposure of HEA-3 to high temperature and pressure sCO2 environment to further assess its performance and to do initial benchmarking with respect to other Ni-based alloys.
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Ružičić, Branka, Dragana Grujić, Blanka Škipina, Mladen Stančić, Đorđe Vujčić, and Miroslav Dragić. "Enhancement of macro-uniformity of copper(I) oxide printed linen fabrics by addition of Pinus sylvestris L. plant extract." In 11th International Symposium on Graphic Engineering and Design. University of Novi Sad, Faculty of technical sciences, Department of graphic engineering and design, 2022. http://dx.doi.org/10.24867/grid-2022-p83.
Abstract:
High surface texture of textile materials is rougher than other printing substrates which can cause excessive macro non-uniformity. Adding metal oxides into the ink to enhance material properties usually add to surface roughness and increase print mottle. In this paper copper(I)oxide particles and different amounts of Pinus sylvestris L. plant extract were added to modified alginate paste (CHT-NV) prior to printing. The aim of this paper is to inspect the influence of added metal oxide and plant extract on the print quality of linen based material via surface macro non-uniformity GLCM determination method. In the pattern recognition phase, the co-occurrence matrix is applied to calculate the texture characteristics, such as contrast, correlation, energy, entropy and homogeneity. The research results indicated that the metal oxide particles have had a negative influence on macro uniformity of printed linen. Increasing of the concentration of extract leads to a dilution of the printing paste, and thus to a greater penetration of copper ions between the threads of the fabric, as well as into the yarn itself.
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Djerdj, Igor, Dalibor Tatar, Jelena Kojcinovic, Srijita Nundy, Habib Ullah, Aritra Ghosh, Asif Ali Tahir, and Bernd Smarsly. "Band gap engineering in novel fluorite-type rare earth high-entropy oxides (RE-HEOs) with computational and experimental validation for photocatalytic water splitting applications." In RAD Conference. RAD Centre, 2022. http://dx.doi.org/10.21175/rad.sum.abstr.book.2022.11.20.