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Item Anomalous Deformation Behavior in ULE Glass upon Microindentation: A Vibrational Spectroscopic Investigation in the Induced Structural Changes of a Ti-Silicate Glass(American Chemical Society, 2021-02) Möncke, Doris; Lind, Felix; Topper, Brian; Kamitsos, Efstratios I.Ultralow expansion (ULE) glass, a binary TiO2–SiO2 glass with 5.67 mol % TiO2, was exposed to microindentation. Vitreous silica was similarly treated and used as a reference material, including the characterization of mechanical properties by means of ultrasonic echography and nanoindentation. The structural modifications induced by indentation were analyzed by micro-Raman spectroscopy. The observed structural changes are consistent with an anomalous, densification-driven, deformation mechanism similar to those observed for vitreous silica or commercially relevant low alkali borosilicate glasses like Duran. As for these fully polymerized glasses, the Raman spectra of indents in the ULE glass are characterized by an upshift of the 407 cm–1 band and an increase in the intensity of the D1 and D2 defect bands, all consistent with structural rearrangements from mostly larger five- and six-member rings to a larger population of smaller four- and three-member rings and an overall lowering of the free volume in the glass. However, contrary to silicon, titanium may change its coordination number under the impact of microindentation. Raman spectra of selected reference materials such as TiO2 and BaTiO3, with known octahedral titanium coordination and known connectivity, as well as fresnoite Ba2TiSi2O8 with known fivefold Ti4+ coordination, are therefore included in this study in support of assigning the new activity appearing in the Raman spectra after an indentation of the ULE glass sample.Item Valence-induced effects on the electrical properties of NiMn2O4 ceramics with different Ni sources(Wiley, 2021-03) Wu, Yiquan; Guan, Fang; Milisavljevic, Iva; Cheng, Xin; Huang, ShifengSpinel-structured NiMn2O4 ceramics, with different valence Ni sources, were originally prepared using Ni2O3 and NiO as raw materials, and the effects of different valence Ni sources on their electrical properties were first investigated. XRD patterns show that both Ni2O3-based and NiO-based NiMn2O4 ceramics are single cubic spinel structures. SEM/EDS images indicate that the NiMn2O4 ceramics exhibited high density at the experiment-determined sintering temperatures. XPS results and Raman drifts prove that the Ni valence-induced changes in Mn ions at B sites played a significant role in the electrical properties and thermal stability of NiMn2O4 ceramics. Compared with NiO-based NiMn2O4, the resistivity at 25°C (ρ25°C) of Ni2O3-based NiMn2O4 increased dramatically from 3109 to 106958 Ω cm, the thermal constant (B25/50) increased from 3264 to 4473 K, and the resistance shifts after annealing for 1000 h at 150°C decreased from 0.80% to 0.74%. The investigation of the relationship between the material properties and valence of Ni sources has provided a new and effective way for designing the spinel-structured negative temperature coefficient (NTC) materials by modulating the valence of ions at A sites in the raw materials.Item Network former mixing effects in alkali germanotellurite glasses: A vibrational spectroscopic study(Elsevier, 2021-06) Möncke, Doris; Tagiara, Nagia S.; Chatzipanagis, Konstantinos I.; Bradtmüller, Henrik; Rodrigues, Ana C. M.; Kamitsos, Efstratios I.Alkali germanotellurite glasses of composition 0.3M2O–0.7[(1-x)GeO2–xTeO2], M=Li, Na and 0 ≤ x ≤ 1, were investigated by Raman and infrared vibrational spectroscopic techniques to search for the origins of the alkali ion-dependent network former mixing (NFM) effect in these ion-conducting glasses. The vibrational spectra measured on mixed network-former glasses, and the spectral comparison between equimolar-mixed glasses (x = 0.5) and pellet-mixtures of the endmember glasses, 0.3M2O–0.7GeO2 and 0.3M2O–0.7TeO2, provided evidence for the formation of hetero-atomic Ge–O–Te linkages and structural rearrangements in the germanate and tellurite components of the glass. The mixing-induced structural rearrangements were expressed in terms of chemical equilibria between the network-building units and were used to make qualitative predictions for changes in the network cross-linking density and the related network-strain energy, as well as in the binding energy part of the activation energy for ion conduction. Thus, it is proposed that the mixing-induced structural modifications in the germanate and tellurite parts of glass cause the cancelation of changes in the binding energy and the network-strain energy contributions to the activation energy for ion transport. These qualitative predictions were discussed in the context of the previously found absence of an NFM effect in ionic conductivity for M=Na and the presence of a weak positive NFM effect for M=Li.Item Illumination-Controlled Color Behavior in Doped Glasses(Elsevier, 2021-07) Clare, Alexis; Bellows, C.H.Photochromism is the phenomenon of an object exhibiting a noticeable color change as a result of its interaction with the light illuminating it. However, this effect can be caused by a number of mechanisms. This paper examines some of these mechanisms, specifically as they pertain to glass systems. Specifically, we will investigate three general mechanisms: those resulting from direct light interactions with the glass matrix and dopants, those resulting from light interactions with inclusions within the glass, and those that do not depend on the glass matrix directly. Areas covered include rare-earth-doped silicates, smart windows, the Lycurgus cup, and commercial ‘dichro’ glass.Item Niobate in Silicate and Phosphate Glasses: Effect of Glass Basicity on Crucible Dissolution(Wiley, 2021-08) Möncke, Doris; Wójcik, Natalia A.; Ali, Sharafat; Kamitsos, Efstratios I.Using niobium crucibles for melting phosphate and silicate glasses of various modifier oxide contents, and therefore varying optical basicity (Λ), was found to result in varying dissolution rates of niobate during melting. Because of their high electronic polarizability, even small concentrations of niobates are detectable in the Raman spectra of glasses. Even <1 mol% Nb2O5 can be identified, as independently confirmed by SEM-EDX analysis. Silica-rich glasses (~60% SiO2, Λ ~0.6) did not show significant Nb dissolution from the crucible, while higher basicity metasilicate glasses (~50% SiO2, Λ ~0.65) and pyrophosphate glasses (~30% P2O5, Λ ~0.7) did show the typical niobate signature in the Raman spectra at 810–840 cm−1, depending on composition. While niobium is well-dissolved throughout the pyrophosphate glass, metasilicate glasses showed a much more intense Raman signature of niobate units near the outer surface of the glass. Measurements along the cross-section of a fractured metasilicate glass showed a steady decrease of the strength of the niobate signature from the surface toward the bulk of the material. Besides correlation with optical basicity, the tendency of melts to dissolve Nb crucible was discussed in terms of the connectivity or polymerization of the network and the corresponding melt viscosity.Item rGO–CMC fiber supercapacitors with core-sheath structure manufactured by coaxial extrusion printing(Springer Nature, 2021-08) Ding, Junjun; Gao YuqiFiber-shaped supercapacitors are attractive as an energy storage unit due to their excellent flexibility. However, fabricating robust fibers with large yields remains a challenge. In this work, we prepare flexible core-sheath fibers via coaxial extrusion printing. Carboxymethylcellulose sodium salt (CMC) slurry with controlled rheological properties is extruded from the outer channel, while the graphene oxide (GO) slurry is extruded from the inner channel simultaneously. The followed freeze-drying process protects GO sheets from agglomeration, providing more efficient chemical reduction. The reduced GO (rGO) sheets are separated and expanded to fill in the CMC sheath, which eliminates the delamination between the CMC sheath and rGO core. We study the influences of the freeze-drying process on the fiber microstructures, and explore the slurry design, fiber quality, reduction condition, and electrochemical performance. The fabrication method allows scalable manufacturing of the core-sheath electrodes and fiber-shaped supercapacitors with more efficient conductive networks.Item Short-term nodal load forecasting based on machine learning techniques(Wiley, 2021-08) Lu, Dan; Zhao, Dongbo; Li, ZuyiThis paper introduces an advanced Short-term Nodal Load Forecasting (STNLF) method that forecasts nodal load profiles for the next day in power systems, based on the combined use of three machine learning techniques. Least Absolute Shrinkage and Selection Operator (LASSO) is employed to reduce the number of features for a single nodal load forecasting. Principal Component Analysis (PCA) is used to capture the features of historical loads in low-dimensional space compared to the original high-dimensional load space where features are barely possible to depict. Bayesian Ridge Regression (BRR) is utilized to decide the parameters of the prediction model from a statistics perspective. Tests based on modified PJM load data demonstrate the effectiveness of the proposed STNLF method compared to the state-of-the-art General Regression Neural Network (GRNN) method. Moreover, the reliability of the day-ahead Unit Commitment (UC) solution is shown to have been improved, based on the forecasted load data using the proposed STNLF method.Item Charge transfer transitions in glasses - Attempt of a systematic review(Elsevier, 2021-09) Möncke, Doris; Ehrt, DorisIn glasses, even low levels of dopants or impurities can give rise to very intense and broad charge transfer transitions from ligands (e.g. oxygen or fluorine ions) to the metal ion (L→M), absorbing strongly in the short wavelength ultraviolet. In an attempt of a systematic review of charge transfer transitions, we compile data of various glass systems with high intrinsic transmission that allow the observation of charge transfer (CT) transitions involving cations of different electronic configurations. Various glasses of different composition were selected as matrices, including fluoroaluminate glasses with low P2O5 content (FP10 = 35AlF3–10MgF2–30CaF2–15SrF2–10Sr(PO3)2), phosphate [SrP = Sr(PO3)2, NSP = Na2O-40SrO-50P2O5], silicate (NS = 15Na2O–85SiO2, DS = 33Na2O–67SiO2), aluminosilicate (BCAS = 10BaO–10CaO–15Al2O3–65SiO2) and borosilicate (NBS1 = 16Na2O–10B2O3–74SiO2, NBS2 = 4Na2O–1Al2O3–21B2O3–74SiO2, Duran = 5Na2O/K2O–1Al2O3–12B2O3–82SiO2) compositions. All glasses were prepared from very high purity materials and doped with various metal ions. Charge transfer transitions of electrons to or from these cations induce absorption and photoluminescence phenomena in the ultraviolet and visible spectral region, which were recorded by optical spectroscopy. Charge transfer transitions were considered for empty valence orbitals, that is, for the high valent 3d, 4d and 5d ions, and for Zn2+, Ag+, Cu+ with full d10 orbitals. 3d, 4d and 5d ions with partially filled valence orbitals that could be stabilized in the named glasses are studied as well. Doping concentrations for these allowed transitions typically ranged from 5 to 5000 wt-ppm of metal ions, with some samples also displaying higher dopant levels. Inter valence charge transfer (IVCT) transitions directly from one metal ion to a neighboring metal ion (M→M) of the same element or metal to metal charge transfer (MM-CT) between ions of different elements can also induce strong visible absorption and deep coloring for which some examples will be discussed.Item Tunable Large-Scale Compressive Strain Sensor Based on Carbon Nanotube/Polydimethylsiloxane Foam Composites by Additive Manufacturing(Wiley, 2021-12) Ding, Junjun; Liu, Chao; Le, Linh; Zhang, MingshaoThe compressive strain sensor is an extensively used flexible electronic device because of its capability to convert mechanical deformation to an electrical signal. However, the difficulty in tuning the performance of the strain sensor limits its further applications. Herein, the approach of fabricating a carbon nanotube (CNT)/polydimethylsiloxane (PDMS) compressive strain sensor, which has both tunable mechanical and electrical performances, is presented. CNT plays the role of reinforcement due to its outstanding mechanical strength and electrical conductivity. PDMS is a widely used matrix because of its softness and nontoxicity. The material extrusion 3D printing method is used to fabricate the composites, due to its advantages of design flexibility and compatibility with liquid-based materials. The foam microstructure formed by removing sodium chloride provides a large-scale deformation of at least 50% compressive strain and excellent elasticity. The strain sensor works durably over 10 000 cycles, with a gauge factor (GF) of 17.4. The compressive strain sensor in detecting both large- and small-scale human motions due to the tunability of CNT/PDMS composites is also tested.Item Novel transparent MgGa2O4 and Ni2+-doped MgGa2O4 ceramics(Springer, 2022-01) Wu, Yiquan; Zhang, Guangran; Goldstein, AdrianIn this study we fabricated, for the first time, magnesium gallate (MgGa2O4, a partially inverted spinel) transparent ceramics, both undoped and doped with 1 at% Ni. The specimens were derived from in-house prepared powder, with a crystallite size of ∼10 nm (by wet chemistry) and densified by pulsed electric current sintering (PECS; peak temperature 950 °C for 90 min). Densification levels of 99.84% and 99.52% of theoretical density were attained for doped and undoped materials, respectively. Doping with Ni was seen to marginally improve the densification level. Quite transparent specimens were produced: the best showing transmission of ∼89% of the theoretical level (thickness t = 0.85 mm). The absorption spectra revealed that the dopant was accumulated as Ni2+ in the octahedral sites of the lattice, as occurs in single-crystal specimens. After excitation at 980 nm, the doped disks exhibited a wide fluorescence band centered at 1264 nm.Item Mechanism of hopping conduction in Be–Fe–Al–Te–O semiconducting glasses and glass–ceramics(Springer, 2022-01) Möncke, Doris; Wójcik, Natalia A.; Tagiara, Nagia S.; Kamitsos, Efstratios I.; Ali, Sharafat; Ryl, Jacek; Barczyński, Ryszard J.Electrical properties of beryllium-alumino-tellurite glasses and glass–ceramics doped with iron ions were studied using impedance spectroscopy. The conductivity was measured over a wide frequency range from 10 mHz to 1 MHz and the temperature range from 213 to 473 K. The D.C. conductivity values showed a correlation with the Fe-ion concentration and ratio of iron ions on different valence states in the samples. On the basis of Jonscher universal dielectric response the temperature dependence of conductivity parameters were determined and compared to theoretical models collected by Elliott. In glasses, the conduction process was found to be due to the overlap polaron tunneling while in glass–ceramics the quantum mechanical tunneling between semiconducting crystallites of iron oxides is proposed. The D.C. conductivity was found not to follow Arrhenius relation. The Schnakenberg model was used to analyze the conductivity behavior and the polaron hopping energy and disorder energy were estimated. Additionally, the correlation between alumina dissolution and basicity of the melts was observed.Item Durable Cr-substituted (Ba,Cs)1.33(Cr,Ti)8O16 hollandite waste forms with high Cs loading(Wiley, 2022-02) Misture, Scott; Zhao, Mingyang; Birkner, Nancy; Schaeperkoetter, Joseph; Koch, Robert; Russell, Patrick; Besmann, Theodore; Amoroso, Jake; Brinkman, KyleA series of Cr-substituted hollandite solid solution BaxCsyCr2x+yTi8−2x−yO16 over a broad range of Cs content (x + y = 1.33, 0 ≤ x and y ≤ 1.33) were systematically investigated. A monoclinic-to-tetragonal phase transition was induced by increasing Cs content in the tunnel sites of the hollandite structure, and all members of the series show structure modulations related to the ordering of the Ba/Cs and vacancies along the tunnels. The thermodynamic stability of the Cr-substituted hollandite samples was measured via high-temperature oxide melt solution calorimetry, which included making the first measurements of the enthalpies of drop solution for Cs2O and BaO in sodium molybdate solvent at 800°C. Thermodynamic stability increased with increasing Cs content for the series of Cr-substituted hollandite, which also exhibited a greater thermodynamic stability compared to other substituted hollandite analogs including Zn, Ga, Fe, and Al variants. The leaching performance, also known as aqueous durability, demonstrated that the fractional Cs release in the Cr hollandite samples is much lower than in other hollandite systems. After 7 days of leaching at 90°C, the lowest Cs release was observed in the sample with the highest Cs content, approximately 22 wt.% Cs. The Cs release could be further suppressed, by approximately 3× if the sample was further densified and sintered. The Cs release results correlated inversely to the thermodynamic stability, suggesting that the thermodynamic stability may be used in future materials design for nuclear waste immobilization.Item Synthesis, Processing and the Effect of Thermal Treatment on the Solubility, Antioxidant Potential and Cytocompatibility of Y2O3 and CeO2 doped SiO2-SrO-Na2O Glass-Ceramics(SAGE, 2022-04) Wren, Anthony; Keenan, Timothy; Placek, Lana; Coughlan, AislingThermal treatment of a 0.52SiO2-0.24SrO-0.24-xNa2O-xMO glass-ceramic series (where x = 0.08 and MO = Y2O3 or CeO2) was conducted in order to synthesize yttrium (Y3+) and cerium (Ce3+) crystalline species that may act as radical oxygen specie (ROS) scavengers. The prominent phase for the Control is a sodium-strontium-silicate while the experimental glass-ceramics (HY, YCe, and HCe) present sodium-Y/Ce-silicate and oxide phases. Disk shrinkage during thermal processing ranges from 1–7% for Control, HY, YCe, and HCe in both diameter and thickness. Solubility studies determined that the release of Si4+ and Na+ are greatest from the Control disks which peaks at 1550 µg/mL. Release from the Y3+ and Ce3+ glass-ceramics reached 320 µg/mL for Si4+ and 630 µg/mL for Na+. The range of antioxidant capacity (ABTS assay) for all samples was 0.31–3.9 mMTE. No significant reduction in MC 3T3 Osteoblast cell viability was observed for any composition tested.Item Glass as a State of Matter—The “newer” Glass Families from Organic, Metallic, Ionic to Non-silicate Oxide and Non-oxide Glasses(Mineralogical Society of America, 2022-05) Möncke, Doris; Topper, Brian; Clare, Alexis G.In theory, any molten material can form a glass when quenched fast enough. Most natural glasses are based on silicates and for thousands of years only alkali/alkaline earth silicate and lead-silicate glasses were prepared by humankind. After exploratory glass experiments by Lomonosov (18th ct) and Harcourt (19th ct), who introduced 20 more elements into glasses, it was Otto Schott who, in the years 1879–1881, melted his way through the periodic table of the elements so that Ernst Abbe could study all types of borate and phosphate glasses for their optical properties. This research also led to the development of the laboratory ware, low alkali borosilicate glasses. Today, not only can the glass former silicate be replaced, partially or fully, by other glass formers such as oxides of boron, phosphorous, tellurium or antimony, but also the oxygen anions can be substituted by fluorine or nitrogen. Chalcogens, the heavier ions in the group of oxygen in the periodic table (S, Se, Te), on their own or when paired with arsenic or germanium, can function as glass formers. Sulfate, nitrate, tungstate and acetate glasses lack the conventional anion and cation classification, as do metallic or organic glasses. The latter can occur naturally—amber predates anthropogenic glass manufacture by more than 200 million years. In this chapter, we are going to provide an overview of the different glass families, how the structure and properties of these different glass types differ from silicate glasses but also what similarities are dictated by the glassy state. Applications and technological aspects are discussed briefly for each glass family.Item Luminescence and Scintillation in the Niobium Doped Oxyfluoride Rb4Ge5O9F6:Nb(MDPI, 2022-06) Misture, Scott; Carone, Darren; Klepov, Vladislav; Schaeperkoetter, Joseph; Jacobsohn, Luiz; Aziziha, Mina; Schorne-Pinto, Juliano; Thomson, Stuart; Hines, Adrian; Besmann, Theodore; zur Loye, Hans-ConradA new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation.Item Future of optical glass education(Optica Publishing Group, 2022-06) Clare, Alexis; Ballato, John; Seddon, Angela; Petit, Laeticia; Hu, Juejun; Richardson, KathleenIn homage to the United Nations International Year of Glass 2022 (IYoG 2022), this article discusses the past, present, and future of glass education, with a focus on inorganic systems of value to optical and photonic applications.Item The intrinsic strength prediction by machine learning for refractory high entropy alloys(Springer Nature, 2022-08) Wang, Kun; Yan, Yong-GangHerein, we trained machine learning (ML) model to quickly and accurately conduct the strength prediction of refractory high entropy alloys (RHEAs) matrix. Gradient Boosting (GB) regression model shows an outstanding performance against other ML models. In addition, the heat of fusion and atomic size difference is shown to be paramount to the strength of the high entropy alloys (HEAs) matrix. In addition, we discussed the contribution of each feature to the solid solution strengthening (SSS) of HEAs. The excellent predictive accuracy shows that the GB model can be efficient and reliable for the design of RHEAs with desired strength.Item Structure-terahertz property relationship in sodium borosilicate glasses(Wiley, 2022-08) Möncke, Doris; Tostanoski, Nicholas; Youngman, Randall; Sundaram, S.K.We report, for the first time, an early evidence of structure-terahertz (THz) property relationship for two tie-lines within the sodium borosilicate glass system. The NaBSi series was chosen to study the effect of the substitution of silicon dioxide for boron oxide, whereas the BNaSi series studies the substitution of silicon dioxide for sodium oxide. Nuclear magnetic resonance, infrared absorption, and Raman spectroscopies were used to determine structural changes across both series. THz time-domain spectroscopy was used to record the refractive index over the measured bandwidth. Individual measurements at .502 THz were used as a frequency of focus for comparisons. The foundation for the proposed structure-THz property relationship is based on higher measurable THz refractive index changes correlated to a depolymerized glass network, R > .5, a network consisting of SiO4 tetrahedra and charge-deficient [BØ4]− tetrahedra-forming borosilicate danburite and reedmergnerite rings with mixed Si–O–B bridges, and the formation of nonbridging oxygen (nbO) atoms on silicate tetrahedra. A polymerized glass network, R < .5, consists of homonuclear boroxol and silica rings within sodium borate and silicate subnetworks. Calculated and experimental fractions of tetrahedral borate and silicate tetrahedra with one nbO, optical basicity, density, and network connectivity data support the structure-THz property relationship.Item Structural and Optical Properties of High Entropy (La,Lu,Y,Gd,Ce)AlO3 Perovskite Thin Films(Wiley, 2022-08) Wu, Yiquan; Corey, Zachary; Lu, Ping; Zhang, Guangran; Sharma, Yogesh; Rutherford, Bethany; Dhole, Samyak; Roy, Pinku; Wang, Zhehui; Wang, Haiyan; Chen, Aiping; Jia, QuanxiMixtures of Ce-doped rare-earth aluminum perovskites are drawing a significant amount of attention as potential scintillating devices. However, the synthesis of complex perovskite systems leads to many challenges. Designing the A-site cations with an equiatomic ratio allows for the stabilization of a single-crystal phase driven by an entropic regime. This work describes the synthesis of a highly epitaxial thin film of configurationally disordered rare-earth aluminum perovskite oxide (La0.2Lu0.2Y0.2Gd0.2Ce0.2)AlO3 and characterizes the structural and optical properties. The thin films exhibit three equivalent epitaxial domains having an orthorhombic structure resulting from monoclinic distortion of the perovskite cubic cell. An excitation of 286.5 nm from Gd3+ and energy transfer to Ce3+ with 405 nm emission are observed, which represents the potential for high-energy conversion. These experimental results also offer the pathway to tunable optical properties of high-entropy rare-earth epitaxial perovskite films for a range of applications.Item The oxidation-resistance mechanism of WTaNbTiAl refractory high entropy alloy(Elsevier, 2022-08) Wang, Kun; Yan, Yonggang; McGarrity, Kade; Delia, Daniel; Fekety, CurtisThe WTaNbTiAl alloy demonstrated excellent oxidation resistance with a 31.83 mg/cm2 of specific mass gain after 48 h oxidation at 1000 °C in the air environment. Based on the multi-scale microstructural characterizations, a diffusion-controlled three-layers oxide scale model was proposed to explain the oxidation kinetics of this RHEA. In addition, thermodynamic calculation results shed light on the formation mechanism of the oxides based on the standard free energy of formation. The present work uncovered the oxidation-resistance mechanism of WTaNbTiAl RHEA via delicate microstructural analysis of oxides, which assists to guide the design of oxidation-resistant high entropy alloys.