Academic literature on the topic 'High entropy oxide'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'High entropy oxide.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "High entropy oxide"
1
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 textAbstract:
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
2
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 textAbstract:
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.
3
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 textAbstract:
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.
4
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 textAbstract:
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.
5
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 textAbstract:
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.
6
Sharma, Yogesh, Min-Cheol Lee, Krishna Chaitanya Pitike, Karuna K. Mishra, Qiang Zheng, Xiang Gao, Brianna L. Musico, et al. "High Entropy Oxide Relaxor Ferroelectrics." ACS Applied Materials & Interfaces 14, no. 9 (February 28, 2022): 11962–70. http://dx.doi.org/10.1021/acsami.2c00340.
Full text
7
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 textAbstract:
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.
8
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 textAbstract:
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.
9
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 textAbstract:
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.
10
Lin, Wei-Chih, Yi-Wen Lien, Louis Etienne Moreau, Hideyuki Murakami, Kai-Chi Lo, Stéphane Gorsse, and An-Chou Yeh. "High-Temperature Oxidation of NbTi-Bearing Refractory Medium- and High-Entropy Alloys." Materials 17, no. 18 (September 18, 2024): 4579. http://dx.doi.org/10.3390/ma17184579.
Full textAbstract:
The oxidation of six NbTi-i refractory medium- and high-entropy alloys (NbTi + Ta, NbTi + CrTa, NbTi + AlTa, NbTi + AlMo, NbTi + AlMoTa and NbTi + AlCrMo) were investigated at 1000 °C for 20 h. According to our observation, increased Cr content promoted the formation of protective CrNbO4 and Cr2O3 oxides in NbTi + CrTa and NbTi + AlCrMo, enhancing oxidation resistance. The addition of Al resulted in the formation of AlTi-rich oxide in NbTi + AlTa. Ta addition resulted in the formation of complex oxides (MoTiTa8O25 and TiTaO4) and decreased oxidation resistance. Meanwhile, Mo’s low oxygen solubility could be beneficial for oxidation resistance while protective Cr2O3/CrNbO4 layers were formed. In NbTi + Ta, NbTi + AlTa and NbTi + CrTa, a considerable quantity of Ti-rich oxide was observed at the interdendritic region. In NbTi + AlCrMo, the enrichment of Cr and Ti at the interdendritic region could fasten the rate of oxidation. Compared to the recent research, NbTi + AlCrMo alloy is a light-weight oxidation-resistant alloy (weight gain of 1.29 mg/cm2 at 1000 °C for 20 h and low density (7.2 g/cm3)).
Dissertations / Theses on the topic "High entropy oxide"
1
Raison, Antoine. "Synthèse de couches minces d'oxydes à haute entropie et étude de leurs propriétés de transport." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF032.
Full textAbstract:
Les oxydes stabilisés par entropie sont une famille de matériaux étudiés pour la première fois par Rost et al. en 2015 et caractérisés par leur grande entropie de configuration. L'entropie de configuration est prépondérante dans l’enthalpie libre de Gibbs à partir d’une certaine température et compense une enthalpie de formation positive, entrainant ainsi la formation des nouveaux composés. L’oxyde stabilisé par entropie (MgCoNiCuZn)O, reporté en 2015, possède une grande résistivité et une grande constante diélectrique, ce qui rend prometteuse son intégration dans des composants électroniques, comme les condensateurs. Dans ce but, il serait utile de réussir à synthétiser ces matériaux par CVD, ce qui permettrait des dépôts conformes sur des substrats complexes. L’objectif de cette thèse était donc de déposer par MOCVD l’oxyde stabilisé par entropie (MgCoNiCuZn)O et d’étudier ses propriétés de transport. Au cours de ce travail, nous avons pu réaliser des films par dépôt chimique en phase vapeur (CVD) des oxydes multicationiques contenant jusqu'à cinq éléments. Ces couches minces ont été déposées sur différents substrats (silicium, saphir, MgO et inconel) et nous avons étudié la formation de ces oxydes ainsi que l'influence du substrat. Il est montré dans cette thèse que la phase stabilisée par entropie ne se forme pas après le dépôt par MOCVD. Pour l’obtenir, un traitement thermique post-dépôt à une température supérieure à 875 °C est nécessaire. D’autre part, il est décrit dans ce travail comment synthétiser une couche monocristalline de l’oxyde stabilisé par entropie à partir d’un dépôt de (CoNiCuZn)O sur un substrat monocristallin de MgO, par diffusion des éléments déposés dans ce dernier. À chaque étape, les dépôts ont été caractérisés par plusieurs techniques comme la DRX en incidence rasante, la MEB, l’AFM, l’XPS ou encore le STEM. Les propriétés électriques des films ont été étudiées à l’aide de diverses méthodes, en prenant en compte notamment la conductivité du substrat. La spectroscopie d’impédance réalisée sur les échantillons déposés sur les substrats conducteurs a permis de mesurer une très grande résistance, qui augmente lors de la formation de la phase stabilisée par entropie. En revanche, la capacitance est assez faible. L’ensemble de ce travail ouvre la voie à des perspectives intéressantes, en particulier la synthèse de nouveaux oxydes à haute entropie ou d’autres oxydes complexes par MOCVDEntropy-stabilized oxides are a family of materials first studied by Rost et al. in 2015 and characterized by their high configurational entropy. Configurational entropy dominates Gibbs free enthalpy above a certain temperature and compensates for a positive enthalpy of formation, driving the formation of new compounds. The entropy-stabilized oxide (MgCoNiCuZn)O, reported in 2015, has a high resistivity and dielectric constant, making it promising for integration in electronic components, such as capacitors. To this end, it would be useful to be able to synthesize these materials by CVD, enabling conformal deposition on complex substrates. The aim of this thesis was therefore to deposit the entropy-stabilized oxide (MgCoNiCuZn)O by MOCVD and to study its transport properties. In the course of this work, we were to produce chemical vapor deposition (CVD) films of multicationic oxides containing up to five elements. These thin films were deposited on various substrates (silicon, sapphire, MgO and inconel) and we studied the formation of these oxides and the influence of the substrate.It is shown in this thesis that the entropy-stabilized phase does not form after MOCVD deposition. To obtain it, post-deposition heat treatment at temperatures above 875°C is required. On the other hand, this work describes how to synthesize a single-crystal layer of the entropy-stabilized oxide from a (CoNiCuZn)O deposit on a single-crystal MgO substrate, by diffusion of the deposited elements into the latter. At each stage, the deposits were characterized by several techniques, including grazing incidence XRD, SEM, AFM, XPS and STEM. The electrical properties of the films were studied using a variety of methods, taking into account the conductivity of the substrate. Impedance spectroscopy of samples deposited on conductive substrates revealed very high resistance, which increases with the formation of the entropy-stabilized phase. On the other hand, capacitance is quite low. Taken together, this work opens the way to interesting prospects, in particular the synthesis of new high-entropy oxides or other complex oxides by MOCVD
2
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.
Full text
3
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.
Full text
4
Osenciat, Nicolas. "Propriétés de transport dans les oxydes à haute entropie." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF005.
Full textAbstract:
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
5
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.
Full textAbstract:
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.
6
Aliyu, Ahmed. "Microstructure and Electrochemical Properties of Electrodeposited High Entropy Alloys Coatings." Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5540.
Full textAbstract:
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.
7
Patel, Ranjan Kumar. "Electronic behavior of epitaxial thin films of doped rare-earth nickelates." Thesis, 2023. https://etd.iisc.ac.in/handle/2005/6129.
Full textAbstract:
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.
8
Sarkar, Abhishek. "High Entropy Oxides: Structure and Properties." Phd thesis, 2020. https://tuprints.ulb.tu-darmstadt.de/14345/1/Doctoral_thesis_Abhishek_Sarkar.pdf.
Full textAbstract:
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.
9
張毓倫. "Study on High-Entropy Oxides Synthesized by Nitrate-Solution Method." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/95510250685674090556.
Full text
10
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.
Full textBook chapters on the topic "High entropy oxide"
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.
Full text
2
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.
Full text
3
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.
Full text
4
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.
Full text
5
Cantor, Brian. "A History of Alloys." In Fundamentals of Multicomponent High-Entropy Materials, 1–84. Oxford University PressOxford, 2024. http://dx.doi.org/10.1093/9780191986710.003.0001.
Full textAbstract:
Abstract This chapter gives a brief overview of some of the key developments in human history. It shows how all the major events in the evolution of humankind have been both driven by and underpinned by the development of new materials. It also shows how new materials are always alloys, i.e. mixtures of simpler starting materials or components. It covers the following: the discovery in the Stone Age of how to use minerals (oxide alloys), and how this supported the emergence of human beings at the beginning of the last ice age and their development of agriculture-based settlements when the ice age ended; the discovery of smelting and the extraction of metals, notably copper and iron alloys in the Bronze and Iron Ages, which drove the growth of cities and civilisation, culture, trade and empires; the engineering and the manufacture of steels (low-carbon iron alloys) in the Industrial Revolution, leading to motors and engines, bridges, mills and factories, cars and planes, and most of the accoutrements of our modern technology-dominated economies and associated high-quality way of life; and the (microalloyed) semiconductors and the silicon chips that fuel the Information Revolution, computers, telecommunications, the internet, and the digital age.
6
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.
Full textAbstract:
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.
7
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.
Full text
8
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.
Full text
9
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.
Full textAbstract:
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 oxide"
1
Komarasamy, Mageshwari, and Glenn Grant. "Material Synthesis and Advanced Manufacturing Without Melting: Advantages of Bulk, High-Shear Processing." In AM-EPRI 2024, 473–82. ASM International, 2024. http://dx.doi.org/10.31399/asm.cp.am-epri-2024p0473.
Full textAbstract:
Abstract The next generation of materials and assemblies designed to address challenges in power generation, such as molten salt or supercritical carbon dioxide thermal transfer systems, corrosion, creep/fatigue, and higher temperature operation, will likely be highly optimized for their specific performance requirements. This optimization often involves strict control over microstructure, including homogeneity, grain size, texture, and grain boundary phases, as well as precise alloy chemistry and homogeneity. These stringent requirements aim to meet the new demands for bulk mechanical performance and durability. Some advanced materials, like oxide-dispersion strengthened or high-entropy alloys, necessitate specialized synthesis, fabrication, or welding/joining processes. Traditional methods that involve melting and solidifying can compromise the optimized microstructure of these materials, making non-melting synthesis and fabrication methods preferable to preserve their advanced characteristics. This paper presents examples where solid-phase, high-shear processing has produced materials and semi-finished products with superior performance compared to those made using conventional methods. While traditional processing often relies on thermodynamics-driven processes, such as creating precipitate phases through prolonged heat treatment, high-shear processing offers kinetics-driven, non-equilibrium alternatives that can yield high-performance microstructures. Additionally, examples are provided that demonstrate the potential for more cost-effective manufacturing routes due to fewer steps or lower energy requirements. This paper highlights advances in high-shear extrusion processing, including friction extrusion and shear-assisted processing and extrusion, as well as developments in solid-phase welding techniques like friction stir welding for next-generation power plant materials.
2
Zhou, Chen. "High-Entropy Oxides Modified Separators for Lithium Sulfur Battery." In 2024 3rd International Conference on Energy and Electrical Power Systems (ICEEPS), 1043–46. IEEE, 2024. http://dx.doi.org/10.1109/iceeps62542.2024.10693153.
Full text
3
GUMEN, O. "High-Temperature Oxidation of High-Entropy FeNiCoCrAl Alloys." In Quality Production Improvement and System Safety. Materials Research Forum LLC, 2023. http://dx.doi.org/10.21741/9781644902691-4.
Full textAbstract:
Abstract. Phase composition and mechanical properties and the formation of oxide layers on Fe40-xNiCoCrAlx (x = 5 and 10 at.%) alloys in long-term oxidation at 900 and 1000°C were studied. In the initial cast state, depending on the aluminum content and valence electron concentration, the alloys contain only an fcc solid solution (VEC = 8 e/a) or a mixture of fcc and bcc phases (VEC = 7.75 e/a). Thin continuous oxide scales containing Cr2O3 and NiCr2O spinel formed on the surface of both alloys oxidized at 900°C for 50 h. A further increase in the annealing time to 100 h leads to the formation of aluminum oxide Al2O3 in the scale on the Fe30Ni25Co15Cr20Al10 alloy, having high protective properties. An increase in the oxidation temperature to 1000°C results in partial failure of the protective layer on the alloy with 10 at.% Al. Long-term holding at 900°C (100 h) + 1000°C (50 h) does not change the phase composition of the Fe35Ni25Co15Cr20Al5 alloy matrix, being indicative of its high thermal stability. In the two-phase Fe30Ni25Co15Cr20Al10 alloy, the quantitative ratio of solid solutions sharply changes: the amount of the bcc phase increases from 4 to 54 wt.% and its B2-type ordering is observed. The mechanical characteristics of the starting alloys and those after long-term high-temperature annealing were determined by automated indentation. The hardness (HIT) and elastic modulus (E) of the cast Fe35Ni25Co15Cr20Al5 alloy are equal to 2 and 147 GPa, respectively, and decrease to 1.8 and 106 GPa after a series of long-term annealing operations. The Fe30Ni25Co15Cr20Al10 alloy shows the opposite dependence: HIT increases from 2.5 in the initial state to 3.1 GPa after annealing and E decreases from 152 to 134 GPa. This indicates that the Fe30Ni25Co15Cr20Al10 alloy is promising as a high-temperature oxidation-resistant and creep-resistant material. Introduction
4
Gorr, Bronislava, Steven Schellert, Bjorn Schäfer, Hans-Jürgen Christ, Stephan Laube, Alexander Kauffmann, and Martin Heilmaier. "Development of oxidation resistant refractory high entropy alloys within the system Ta-Mo-Cr-Ti-Al." In IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-bg7505.
Full textAbstract:
Refractory High Entropy Alloys (RHEA) are considered novel promising high temperature materials for structural applications at ultra-high temperatures primarily due to their attractive mechanical properties. By contrast, the oxidation behavior of RHEA has raised concern owing to pest oxidation, significant weight changes, scale spallation or even complete oxidation at elevated temperatures. In this contribution, results on high temperature oxidation behavior of RHEA within the alloy system Ta-Mo-Cr-Ti-Al will be presented. The isothermal oxidation kinetics of alloys was continuously recorded in thermogravimetric devices. The oxidation experiments were performed in laboratory air in wide temperature range from 500°C to 1500°C. The crystal structures of corrosion products were analyzed using X-ray diffraction. The morphology of oxides scales and internal precipitates was characterized applying scanning electron microscopy in conjunction with energy dispersive X-ray spectroscopy. The high-resolution images of the oxide layers were generated in transmission electron microscope. In order to identify the oxidation states, electron energy-loss spectroscopy was utulized in combination with scanning transmission electron microscopy. The experimental results show that the equiatomic alloy Ta-Mo-Cr-Ti-Al exhibits very high oxidation resistant despite the high amount of refractory metals. It was found that the superior oxidation behavior of this alloy is attributed to formation of the rutile-type oxide (Cr,Ta,Ti)O2. The studies on oxidation mechanism of alloys in the system Ta-Mo-Cr-Ti-Al revealed that the growth of this oxide is governed by the inward diffusion of oxygen via oxygen vacancies. A pronounced zone of internal corrosion was, however, observed underneath the oxide scale indicating the notable inward diffusion of oxygen and nitrogen. Due to additions of higher valency metals, e.g. W, the thickness of the zone of internal corrosion was successfully reduced. This experimental finding confirmed the hypothesis that the doping of higher valency cations of n-type oxides leads to decrease in the oxygen vacancy concentration. This study showed that while many RHEA indeed suffer from poor oxidation resistance, some RHEA, e.g. the equiatomic Ta-Mo-Cr-Ti-Al alloy, exhibit very good protectiveness which is attributed to the formation of rarely encountered Ta-Cr-Ti-based complex oxides which possess high thermodynamic stability and low growth rates.
5
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.
Full textAbstract:
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.
6
Bhattacharya, R., O. N. Senkov, A. K. Rai, X. Ma, and P. Ruggiero. "High Entropy Alloy Coatings for Application as Bond Coating for Thermal Barrier Coating Systems." In ITSC 2016, edited by A. Agarwal, G. Bolelli, A. Concustell, Y. C. Lau, A. McDonald, F. L. Toma, E. Turunen, and C. A. Widener. DVS Media GmbH, 2016. http://dx.doi.org/10.31399/asm.cp.itsc2016p0279.
Full textAbstract:
Abstract High-entropy alloys (HEAs) are well suited for use in high-temperature environments due to their combination of strength, ductility, thermal stability, and corrosion and wear resistance. In this study, NiCoCrAlSi-based HEA coatings are deposited by HVOF and air plasma spraying (APS) and their phases, microstructure, and composition are evaluated by means of XRD, SEM, and EDS analysis. The results show that BCC/B2 phases are the main constituent in HVOF coatings that were diffusion heat treated. APS coatings of the same composition, on the other hand, exhibited a two-phase structure consisting of L12 and BCC/B2 phases. The HEA coatings produced by HVOF were tested for oxidation resistance and their morphology and oxide scales were examined with the aim of developing a high-quality bond coat for thermal barrier coating (TBC) systems.
7
Shahbazi, H., H. Vakilifard, R. B. Nair, A. C. Liberati, C. Moreau, and R. S. Lima. "High Entropy Alloy (HEA) Bond Coats for Thermal Barrier Coatings (TBCs)—A Review." In ITSC 2023. ASM International, 2023. http://dx.doi.org/10.31399/asm.cp.itsc2023p0659.
Full textAbstract:
Abstract Due to the aggressive operation conditions of turbine hot sections, protective coatings are required to provide oxidation and hot corrosion resistance for superalloy components. Thermal barrier coatings (TBCs) are comprised of a ceramic top coat and a metallic bond coat (BC) and are typically used as thermal protection systems against these aggressive environments. Conventional BC materials are MCrAlX, with M being metals or alloys (e.g., Ni, Co or NiCo) and X being reactive elements such as Y, Hf, Ta, Si. Due to their strength, thermal stability, and oxidation resistance, high-entropy alloys (HEAs) have presented promise for use as BC materials in hightemperature applications. Owing to its cocktail effect, optimally chosen HEAs could help to enhance the hot corrosion resistance of BCs by forming a more continuous, dense, and uniform thermally grown oxide (TGO). Furthermore, HEAs could help to control the diffusion between the bonding layer and substrate in elevated temperature environments. This paper will discuss the thermodynamic, mechanical, and microstructural behaviour of HEAs. Furthermore, the selection and usage of HEAs as BCs will be explored and compared to conventional BCs in TBC systems.
8
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.
Full textAbstract:
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.
9
Csík, Dávid, Gabriela Baranová, Dániel Száraz, Róbert Džunda, L'ubomír Medvecký, and Karel Saksl. "Dual-Phase High Entropy Oxide Based on AlFeCoNiCu as an Advanced Anode Material for Lithium-Ion Batteries with Self-Healing Properties." In 2023 13th European Space Power Conference (ESPC). IEEE, 2023. http://dx.doi.org/10.1109/espc59009.2023.10298173.
Full text
10
Pal, S., R. Bhaskaran Nair, and A. McDonald. "Influence of Microstructure on Hardness and Electric Resistivity of Flame-Sprayed High Entropy Alloy Coatings." In ITSC2022. DVS Media GmbH, 2022. http://dx.doi.org/10.31399/asm.cp.itsc2022p0534.
Full textAbstract:
Abstract High entropy alloys (HEAs) are classified as a new class of advanced metallic materials that have received significant attention in recent years due to their stable microstructures and promising properties. In this study, three mechanically alloyed equiatomic HEA coatings – AlCoCrFeMo, AlCoCrFeMoW, and AlCoCrFeMoV – were fabricated on stainless steel substrates using flame spray manufacturing technique. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Vicker’s microhardness were utilized to characterize the fabricated HEA coatings. Furthermore, Joule heating experiments using a modified version of a two-probe test was used to measure the electrical resistivity of the HEA coatings. To prevent short-circuiting of the metallic coatings, a thin layer of alumina was deposited as a dielectric material prior to the deposition of HEA coatings. The microstructure of the HEA coatings showed the presence of multiple oxide regions along with solid-solution phases. The porosity levels were approximately 2 to 3% for all the HEA coatings. The HEA coatings had a thickness of approximately 130 to 140 μm, whereas the alumina layer was 120 to 160 μm thick. The electrical resistivity values were higher for all the HEA coatings compared to flame-sprayed Ni-20Cr and NiCrAlY coatings and AlCoCrFeNi HEA thin film, which may be attributed to the characteristics of HEAs, such as severe lattice distortion and solute segregations. The combined interaction of high hardness and increased electrical resistivity suggests that the flame-sprayed HEA coatings can be used as multifunctional wear-resistant materials for energy generation applications.