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Cerium oxide (CeO2), one of the most significant heterogeneous catalysts, has attracted extensive research interest. Herein, ultrafine spherical CeO2 with a diameter of 5 nm is successfully synthesized within a reaction time of 25 min by a simple and environmentally friendly sonochemical method without any additional oxidants or high temperature and pressure conditions, and 50 nm spherical CeO2 was obtained by heat treating the 5 nm spherical CeO2 in 400°C air atmosphere condition for 3 h. By controlling the ultrasonic condition, a specific surface area of up to 194.2 m2/g and a bandgap as low as 2.2 eV are achieved in the CeO2 nanoparticles without any heat treatment. Further study has shown that the as‐prepared spherical CeO2 without heat treatment exhibits remarkable photocatalytic and antibacterial activities under visible light conditions. The study is beneficial for energy conservation in fabricating ultrafine photocatalytic and antibacterial nanomaterials. [ABSTRACT FROM AUTHOR]

The construction of p–n heterojunction is critical to reduce the electron–hole recombination rate and broaden the light absorption edge of photocatalysts. In this study, we successfully synthesize the Cu2O/CeO2 p–n heterojunctions through a rapid, simple, and environmentally friendly sonochemical method without any additional oxidants or elevation of the temperature and pressure. The prepared Cu2O/CeO2 heterojunction shows excellent adsorption of light, low electronic transfer resistance, and higher electron transfer efficiency. Under the irradiation of visible light, the as‐prepared Cu2O/CeO2 heterojunction exhibits exceptional capability for the degradation of methylene blue as well as outstanding reusability. The photo‐generated h+ is found to have a significant influence on the photocatalytic antibacterial of the as‐prepared Cu2O/CuO2 heterojunction under visible‐light irradiation and the sterilization rate toward Staphylococcus aureus and Escherichia coli of our samples can achieve up to 100%. Our work provides a green and rapid way to produce Cu2O/CeO2 p–n heterojunctions with enhanced photocatalysis. [ABSTRACT FROM AUTHOR]

Estimating the synthesizability is the prerequisite to discovering novel high‐entropy ceramics with exotic properties. Herein, combined with the high‐throughput experiments and machine learning (ML) methods, the synthesizability of high‐entropy hexaborides (HEB6) is investigated. To construct the database, 100 equimolar quinary HEB6 samples synthesized using a self‐developed high‐throughput solid‐state reaction technique and 20 potential synthesizability descriptors calculated from fundamental parameters of constituent precursors are simultaneously collected. By employing the ML and the genetic algorithms, an optimal model consisting of five synthesizability descriptors (l¯$\bar{l}$, δl${\delta }_l$, δχP${\delta }_{{\chi }^{\mathrm{P}}}$, δI1${\delta }_{{I}_1}$, and δEF${\delta }_{{E}_{\mathrm{F}}}$) is determined for predicting the synthesizability of equimolar HEB6 with a high validation accuracy (93.0%), and 7 005 new equimolar quinary HEB6 are then proposed. Moreover, the applicability of our established model on non‐equimolar HEB6 is explored by the prediction of 30 synthesizability diagrams of non‐equimolar quinary HEB6. A high accuracy of 90.9% is further validated by the synthesis experiments of 11 non‐equimolar HEB6 candidates. Our work establishes an effective ML model for assessing the synthesizability of both equimolar and non‐equimolar HEB6 and paves a promising way to accelerate the discovery of new synthetic accessible high‐entropy ceramics. [ABSTRACT FROM AUTHOR]

Compositional screening is an important strategy to improve the oxidation resistance of high‐entropy diborides (HEB2), yet the related studies are limited. Here, we report a rare‐earth (RE) element compositional screening strategy to improve the oxidation resistance of HEB2. To be specific, the single‐phase (Hf0.28Zr0.28Ta0.28RE0.16)B2 (HEB2‐RE) samples with 12 different RE elements are fabricated via ultrafast ultrahigh‐temperature synthesis and spark plasma sintering techniques, and their oxidation resistance is explored by isothermal oxidation tests. The results show that the as‐obtained HEB2‐Sc samples possess the best oxidation resistance among all the as‐fabricated HEB2‐RE samples. Such outstanding oxidation resistance is ascribed to the enhanced viscosity of the generated B2O3 glass originating from the solid solution of (Zr, Me)0.84Sc0.16O2 complex oxides, as confirmed by transmission electron microscope observations and first‐principles calculations. [ABSTRACT FROM AUTHOR]

Due to the huge composition space, composition screening is of great importance to the optimization of high‐entropy diborides (HEBs) with exceptional oxidation resistance. However, related studies are lacking. Here, a novel rapid, effective strategy to fully screen the compositions on the oxidation resistance of HEBs is proposed. Specifically, the synthesis of the equiatomic 1‐ to 9‐cation multicomponent diborides of the IVB, VB, and VIB groups in seconds via an ultrafast ultrahigh‐temperature synthesis technique is realized. Subsequently, combined with the thermogravimetric analysis and first‐principles calculations, the roles of incorporated elements are systematically explored. The results show that Zr, Cr, Ta, Nb, and W elements are the key to the improved oxidation resistance of HEBs, while Ti, Mo, and V elements are destructive. In particular, the positive roles of metal elements are mainly attributed to the partial dissolution of the generated metal oxides into the generated B2O3 glass, which can improve the viscosity of B2O3 and thus enhance its high‐temperature stability and reduce the oxygen diffusion rate, as confirmed by the first‐principles calculations. This study paves a way to rapidly screen the elements in HEBs, which can be a guide for further anti‐oxidation designs. [ABSTRACT FROM AUTHOR]

Synthesis of ultrafine powders of high‐entropy rare‐earth silicates (HERESs) is critical for expanding their applications. Here, we report the synthesis of ultrafine HERES powders via a simple molten salt method for the first time. The results show that the single‐phase high‐entropy rare‐earth disilicates (HEREDs) and monosilicates (HEREMs) with monoclinic crystal structures can be successfully synthesized at 1073 and 1173 K, with the content ratios of raw rare‐earth oxides to SiO2 of 1:2.4 and 1:0.9, respectively. The average particle sizes of the as‐synthesized HEREDs and HEREMs powders are measured to be 1.32 and 1.64 μm, respectively. Meanwhile, uniform elemental distributions are confirmed in these powders without any element separation or segregation. In addition, a "dissolution–precipitation" mechanism is proposed to clarify the synthesis process of HERESs. This study not only provides a new synthesis methodology for HERES powders but also reveals a new insight into the growth mode for HERES powders. [ABSTRACT FROM AUTHOR]