Fly ash, a widespread by-product of coal combustion, is increasingly regarded as a promising raw material for mullite-based ceramics, particularly high-alumina fly ash (HAFA). In this study, three HAFA and two conventional fly ash (CFA) samples from northern China were systematically characterized by XRD, XRF, PSDA, MAS-NMR, SEM-EDS, and quantitative phase analysis. HAFA was found to contain high proportions of mullite (>47 wt%), corundum (>7 wt%), reactive alumina (3-10 wt%), and amorphous silica (20-30 wt%), whereas CFA was dominated by quartz and alkaline oxides. Five representative microstructures were identified, with sponge-like aggregates (mullite-amorphous silica eutectics) playing a crucial role as precursors for mullite crystallization. Based on these observations, three regulatory mechanisms were identified: (1) A/S (Al2O3/SiO2) ratio control, (2) flux phase modulation, and (3) whisker-oriented strengthening. To validate these mechanisms, a CaO-assisted sintering strategy was developed. Moderate CaO addition promoted liquid-phase formation, facilitated interlaced mullite whisker growth, and improved ceramic densification and strength, while excessive CaO caused lateral whisker growth and structural defects. Optimized ceramics prepared with similar to 4 wt% CaO at 1500 degrees C achieved a favorable balance of densification, microstructural integrity, and mechanical properties. This work establishes a comprehensive framework linking fly ash composition, microstructural evolution, and ceramic performance, offering fundamental insights and practical guidance for sustainable, high-value utilization of fly ash in mullite ceramics.

To improve the oxidation resistance and self-healing ability of ZrB2 based coatings, ZrB2-ZrSi2 coatings modified by powder alloying were successfully prepared, and the effect of different proportions of ZrB2-ZrSi2 alloy composition on the oxygen barrier layer was studied. The results showed that the 90 vol.% ZrB2- 10 vol.% ZrSi2 coating exhibited the lowest oxygen permeability (3.66%) and the highest cumulative protective efficiency (95.77%) among all components. The synergistic strengthening effect of ZrB2-ZrSi2 alloying significantly improved the stability and oxygen barrier performance of the coating at high temperatures. The dispersed distribution of Zr oxides helps to expand the crystallization region, enhance the structural densification of the glassy layer, suppress oxygen permeability, and reduce oxygen-induced damage to the glassy layer. The Zr-Si-O multiphase glass layer spontaneously formed during the oxidation process could effectively hinder the oxygen diffusion channel, which enhances the structural integrity of the coating in the oxidation environment and prolongs its protective function.

ABSTRACT This study presents a comprehensive theoretical investigation of the electronic structure, temperature‐dependent dielectric properties, and defect‐mediated doping mechanisms in BaTiO 3 ‐based perovskite ceramics, employing density functional theory (DFT) calculations integrated with deep neural network potential molecular dynamics simulations. First‐principles calculations using the Vienna Ab initio Simulation Package (VASP) with the GGA+U methodology ( U eff = 4.2 eV for Ti 3d states) provided accurate structural parameters, electronic band structures, and defect formation energies. A high‐fidelity deep potential was constructed using the DeePMD‐kit framework based on 15 247 DFT‐calculated configurations, achieving exceptional accuracy with energy RMSE of 0.87 meV/atom and force RMSE of 115 meV/Å. Critically, we demonstrate that conventional VASP/DFPT calculations on small 2 × 2 × 2 supercells severely underestimate dielectric constants ( ε r ≈ 120 for pure BaTiO 3 ), while large‐scale deep potential molecular dynamics on 10 × 10 × 10 supercells (5000 atoms) yields values ( ε r ≈ 2100 at room temperature, 298 K) in quantitative agreement with experiments (1700–2000), validating the necessity of large‐scale simulations for accurate dielectric property predictions. The computational results reveal fundamentally distinct doping mechanisms: acceptor doping with Mg 2+ (1.5 mol% at Ti‐sites) creates [Mg ″ Ti −V O •• ] defect‐dipole complexes with a binding energy of 0.53 eV, inducing compositional heterogeneity that transforms the sharp first‐order ferroelectric transition into a diffuse phase transition, yielding a room‐temperature dielectric constant of ε r ≈ 3400 (at 298 K) and a temperature coefficient of capacitance (TCC) of approximately ±12% across the X8R evaluation range, approaching X8R compliance. Donor doping with La 3+ (2 mol% at Ba‐sites) raises the room‐temperature permittivity to ε r ≈ 3800 and enhances the peak dielectric constant but preserves the sharp Curie transition with TCC exceeding +200%, failing X8R compliance. The amphoteric dopant Y 3+ exhibits 72% B‐site versus 28% A‐site occupancy (Δ E site = +0.35 eV), giving a room‐temperature dielectric constant of ε r ≈ 3100, while producing a broadened but insufficiently suppressed peak with TCC of approximately +35% near the diffuse maximum, also exceeding X8R limits at this concentration.

A new process for the controlled-synthesis of large surface area mesoporous silica nanoparticles (MSNs) from the unique (NH4)2SiF6-NH4F solution produced from coal fly ash was developed using template assisted rapid chemical precipitation method. This work achieved the synthesis of MSNs with specific surface area (SSA) ( 500 m2/g—1064 m2/g), small particle size ( 90 nm- 133 nm) with narrow pore size distribution ranging between (7.56 nm- 20.11 nm) and reduced agglomeration condition by proposing a unique reactant’s feeding pattern and studying other parameters aiding the controlled synthesis process. The effect of high concentration fluoride ion on cationic cetyltrimethylammonium bromide (CTAB) template was also investigated. A novel CTAB removal method from the highly porous cavities of the silica nanoparticles under mild conditions was proposed. At 50 °C and atmospheric pressure, the foam fractionation technique showed 61

Sustainable power generation in outdoor environments is crucial for realizing self-powered Internet of Things (IoT) and wearable applications. Among various approaches, thermoelectric generation is particularly attractive. However, its widespread deployment is inevitably hindered by unstable energy harvesting during diurnal environmental shifts. Here, we report a monolithic thermoelectric device based on Janus photonic metamaterials (JPM), which utilizes radiative cooling to drive continuous thermoelectric generation. Featuring an asymmetric concentration distribution of hexagonal boron nitride nanosheets (h-BNNs) within a polydimethylsiloxane (PDMS) matrix, coupled with pyramidal metastructures on the top surface, the resulting Janus photonic metamaterials simultaneously maximize solar reflectance and mid-infrared (MIR) emissivity to achieve radiative cooling. With single-walled carbon nanotube (CNT) arrays sandwiched between the JPM and a low-filler h-BNN composite substrate, the monolithic device achieves a considerable temperature difference of 27.5 K and an output voltage of 23.4 mV under a solar irradiance of 620 W m-2. Even at zero solar irradiance, it maintains a 1 mV voltage output driven solely by the cooling effect. Furthermore, the rear surface of the device successfully achieves subambient cooling once the solar irradiance falls below 500 W m-2. Ultimately, this work presents a viable strategy to realize sustainable self-powered operation and highly effective thermal management for diverse outdoor electronic systems.

Piezoelectric actuators are widely used industrial electronic devices. In recent years, driven by environmental concerns, lead-free piezoelectric materials, particularly KNN-based ceramics, have gained increasing attention. In this study, Mn-doped KNN piezoelectric ceramics were synthesized by the conventional solid-state reaction method and sintered in a reducing atmosphere. By employing a synergistic strategy involving defect dipoles and ferroelectric domain switching, a giant converse piezoelectric coefficient ( d* ) of 2676 pm/V and a strain of 0.67% are achieved in the KNNM ceramics 33 under an electric field of 2.5 kV/mm. In our ceramic samples, no obvious strain enhancement attributable to electrobending is observed. The ceramic exhibits excellent thermal stability, with performance degradation of less than 10% from room temperature to 170 degrees C, and maintains favorable performance after 2 million fatigue cycles. Considering the combination of excellent piezoelectric properties, high temperature stability, superior fatigue resistance, and reduction resistance, KNNM ceramics are expected to facilitate the development of lead-free piezoelectric actuators compatible with base-metal internal electrodes. (c) 2026 The Authors. Published by Elsevier B.V. on behalf of The Chinese Ceramic Society. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

The insulation resistance (IR) degradation of BaTiO3-based multilayer ceramic capacitors (MLCCs) is predominantly attributed to the migration and accumulation of oxygen vacancies () toward the cathode. This study innovatively investigates the spatial distribution characteristics of using cathodoluminescence (CL) spectroscopy. The physical mechanism of CL emission primarily involves the recombination of electrons and holes between defect energy levels, such as those associated with , barium vacancies (), and Ti3+, and the valence and conduction bands. CL test results indicated that the , , and Ti3+ concentration progressively increased from the central region of the MLCCs toward the electrode edges, and further to the external ceramic layer. Destructive physical analysis and computed tomography were performed on MLCCs that experienced breakdown failure after IR degradation. The analysis revealed that over 90% of the failure initiation sites were located at the electrode edges, indicating that a high concentration promotes failure occurrence. Furthermore, the combined effect of localized electric field concentration and the propensity for heat accumulation also plays a critical role, making the electrode edge along the W-direction the most susceptible site for failure initiation. This study provides a theoretical foundation for a comprehensive understanding of the IR degradation behavior in MLCCs.

High-power pulsed systems demand dielectric capacitors with high energy density and efficiency. Although perovskite ceramics dominate this field, simultaneously achieving high performance and fatigue endurance remains a significant challenge. Our study addresses this aim by incorporating a Ba1-xSrxTiO3 second phase into tungsten bronze-type Ba1-xSrxNb2-yTayO6 matrix, followed by chemical coating with a SiO₂ layer. The prepared ceramics achieve an energy density of 21.1 J/cm³ with an efficiency of 84.5%. Furthermore, by combining a rational multilayer ceramic capacitor design with the thickness effect, an energy density of 23.2 ± 1.2 J/cm³ and an improved efficiency of 92.8 ± 0.4% are attained, representing a record energy density for tungsten bronze-based ceramics and capacitors. The dual-core-shell structure and compositional gradients induce lattice mismatch, boosting polarization and breakdown strength. The fabricated devices also demonstrate remarkable stability under varying frequency, temperature, and fatigue cycling conditions.

In this study, the preparation, the Si infiltration densification treatment and the surface treatment of recrystallized SiC (RSiC) substrate were initial completed. Scanning electron microscopy (SEM) and x‐ray diffraction (XRD) were applied to observe the surface morphology and microstructure of RSiC substrate before and after the above steps of treatment. Then, the 3C‐SiC coating with the porous interface layer was prepared on the RSiC substrate using chemical vapor deposition (CVD) method. The purity of the 3C‐SiC coating was detected by high resolution glow discharge mass spectrometry (HR‐GDMS) for all elements (75 elements) content, and the results showed that the purity of the 3C‐SiC coating reached 99.99901

In this work, SiC/(NaAlSi3O8) and SiC/Al2O3 composites were successfully synthesized from high-alumina fly ash (HAFA), an industrial byproduct of coal-fired power plants, through an environmentally friendly process involving alkaline activation and carbothermal reduction at 1250-1550 degrees C. The SiC/(NaAlSi3O8) composite sintered at 1250 degrees C for 4 hours exhibited a low density of 1.41 g/cm3 and high porosity of 62%, achieving a minimum reflection loss (RLmin) of -57.04 dB at 12.08 GHz and a maximum effective absorption bandwidth (EABmax) of 4.11 GHz at 2.2 mm thickness. In comparison, the SiC/Al2O3 composite sintered at 1400 degrees C for 3 hours demonstrated excellent performance at reduced thickness (1.5 mm), with an RLmin of -43.64 dB and an EABmax of 4.28 GHz. The outstanding electromagnetic wave absorption performances are attributed to synergistic effects, including efficient impedance matching, strong dielectric loss, dipole and interfacial polarization, and enhanced attenuation capability of the composites.

The rapid rise of M2CSe2 (M = Nb, Ta) MXenes with a single type of selenium termination has brought new opportunities due to their layered nature and van der Waals interlayer coupling. However, their solid solutions remain unclear. Here, we report the molten salt synthesis and characterization of (NbxTa1-x)2CSe2 solid solutions at the M-site. With the assistance of molten salts acting as a liquid medium for both the reaction bed and mass transport, continuous solid solutions with a well-defined hexagonal shape can be synthesized from elemental powders. As evidenced by electron microscopy and Raman spectroscopy, Nb and Ta at the M-site are distributed randomly in the substitutional solid solutions. The solid solutions exhibit a metal-like behavior. The Nb/Ta composition dependence of both electrical resistivity and temperature coefficient shows a "W" shape. Intriguingly, the composition dependence of lattice parameter a also follows the same shape. In the whole Nb/Ta composition range, the work functions can be tuned from 5.10 eV (Nb2CSe2) to 5.35 eV (Ta2CSe2). The friction coefficients are approximately 0.2, indicating van der Waals interlayer coupling in the solid solutions.

To efficiently recycle high-alumina fly ash (HAFA), a solid waste from coal-fired power plants, and reduce the production costs of microwave absorbents, fly ash-based composites were synthesized using a simple alkaline activation and carbothermal reduction method. The results showed that the dielectric constant of the composites could be adjusted by varying the concentration of the alkaline solution, thereby improving their electromagnetic properties. The minimum reflection loss (RLmin) for FA50, FA100, FA150, and FA200 are -14.46 dB, -18.36 dB, -39.71 dB, and -54.91 dB at 7 mm, respectively. After activation, the composites were sintered at 1250 °C for 4 h, with S50 achieving an RLmin of -40.37 dB at 17.05 GHz and a maximum effective absorption bandwidth (EABmax) of 3.86 GHz at 1.5 mm. Meanwhile, composite S200 exhibited improved performance, with RLmin values of -58.82 dB at 7.88 GHz and -53.47 dB at 9.11 GHz, along with EABmax of 2.75 GHz at 3.0 mm and 3.81 GHz at 2.5 mm, achieving an absorption efficiency of approximately 99.9999%. The composites' strong wave attenuation results from excellent impedance matching and from various conduction and polarization losses (dipole and interfacial) within their components. Due to their simple preparation, outstanding electromagnetic wave absorption, and low cost, these composites are promising for high-performance electromagnetic wave absorption applications. This study also demonstrates the full recovery and utilization of HAFA.

Lead-free multilayer ceramic capacitors (MLCC) have received unprecedented attention for energy storage in constantly lightweighted and miniaturized electronic and electrical systems. However, their popularized application is still bottlenecked by the thermal runaway issues of energy-storage ceramics because of the common nature of temperature positive self-feedback characteristics that are reflected by continuously increasing power loss with elevated temperatures. In this work, temperature negative self-feedback that prevents thermal runaway is realized in NaNbO3 modified 0.87BaTiO(3)-0.13Bi[Zn-2/3(Nb0.85Ta0.15)(1/3)]O-3 (NN0, NN0.05, NN0.10, NN0.15, NN0.20) lead-free energy-storage ceramics as a demonstration, based on a strategy of peak shifting and loss suppression. Negative self-feedback at weak and strong electric fields was attained by the temperature dependent power loss extracted from dielectric-temperature curves and polarization-electric field loops, respectively, in which NN0.05 is the optimal selection because of the largest negative self-feedback range from 25 to 150 degrees C and minimally declined energy-storage performance compared to the pristine NN0. Thermal field simulation of single ceramic layers indicates that NN0.05 achieves faster thermal stabilization with lower than NN0. Based on the Monte Carlo method, MLCC consisting of 20 ceramic layers with different defect levels were created, and evenly distributed temperature was confirmed for NN0.05 with prevented thermal runaway. General applicability and advantages of temperature negative self-feedback preventing thermal runaway in energy-storage ceramics were verified by three artificial types of MLCC. This work offers a solution to the critical thermal runaway issues of lead-free energy-storage ceramics, facilitating their wide application in MLCC toward lightweighted and miniaturized electronic and electrical systems.

As a critical research direction in dielectric energy storage applications, achieving a synergistic balance between a high breakdown strength (E-b) and high polarization remains a significant challenge for lead-free relaxor ferroelectrics. In this work, we proposed a rational chemical design strategy by simultaneously doping A- and B-site ions into classical BaTiO3 (BT) ferroelectrics, breaking the long-range ordered polarization, increasing the maximum polarization (P-m), reducing the remnant polarization (P-r), and improving the E-b. An ultrahigh recoverable energy storage density (W-rec) of 15.3 J/cm(3), accompanied by a high energy storage efficiency (eta) of 82.4%, was finally achieved at 1150 kV/cm. Impedance spectroscopy and microstructure analyses reveal enhanced activation energies for both grains and grain boundaries, as well as multiphase coexistence and formation of polar nanoregions (PNRs). This collectively contributes to an elevated breakdown strength while maintaining robust polarization. This study presents a promising pathway to achieve advanced energy storage performance in lead-free dielectric systems.

The electrocatalytic nitrate reduction reaction (NO3RR) to ammonia (NH3) presents a sustainable pathway for wastewater treatment and green NH3 synthesis. However, developing catalysts that simultaneously achieve high activity, selectivity, and stability over a wide pH range remains a challenge due to the inadequate supply of active hydrogen (*H). Herein, an efficient Cu3P hollow nanocubes (Cu3P-HNCs) electrocatalyst has been successfully designed for high-performance NO3RR over a wide pH range. The as-prepared Cu3P-HNCs exhibit excellent performance for NO3RR, achieving NH3 yield rates of 19.77, 26.04 and 12.39 mg h-1 mgcat-1 in neutral, alkaline and acidic electrolytes, respectively. The experimental results and theoretical calculations prove that the hollow cubic architecture endows the Cu3P-HNCs with a high specific surface area and multiple catalytic active sites, while phosphoration induces a favorable downshift in the d-band center. This electronic optimization weakens intermediate adsorption and effectively reduces the energy barrier of the key reaction step, ultimately leading to the distinct NO3RR performance. This study elucidates a synergistic design strategy and offers insights into designing efficient and robust electrocatalysts for NO3RR across a broad pH range.

China has about 98% of the diasporic bauxite ores, with around 70% being low-grade. These low-grade bauxites containing high silica pose significant challenges in alumina recovery, as their reaction with sodium aluminate in the Bayer process leads to alumina loss and increased caustic consumption. This study presents a novel, sustainable process for upgrading low-grade bauxite with an initial alumina-to-silica mass ratio (A/S) of 2.39. The process involves muffle furnace heating and water quenching, as well as fragmentation of bauxite. In this process, low-grade bauxite was first treated in a muffle furnace at 350 degrees C for 50 min, using a particle size of 355-425 & micro;m, and then suddenly cooled in cold water for fragmentation. Subsequently, a separation of the parts into smaller sizes is needed. The results demonstrate a 130% increase in the A/S mass ratio, with 67% concentrate recovery for alumina extraction. This method offers a promising solution for efficiently using low-grade bauxites without further treatments, contributing to more sustainable alumina production practices. The process is adaptable to different bauxite sources and could significantly impact alumina refineries' economics and environmental footprint worldwide.

Catalytic oxidation reactions of hydrogen isotope gases are of significant importance for the chemical processing of hydrogen isotopes. In this study, a hydrogen adsorption energy-composition model for CeO2-based oxide materials was developed using machine learning. Materials genome engineering and density functional theory (DFT) calculations were integrated to construct a descriptor dataset. The support vector regression (SVR) model exhibited the best predictive performance on the test set, achieving a coefficient of determination (R-2) of 0.97. SHAP analysis indicated that the most influential descriptors include the highest oxidation state, surface energy, enthalpy of melting, atomic mass and bond parameter. Nanoparticles of CeO2-based oxides were synthesized via a sol-gel method and validated by hydrogen temperature-programmed reduction (H-2-TPR) experiments. The catalytic activity followed the order Co:CeO2 > Eu:CeO2 > La:CeO2 > CeO2, consistent with predictions. The kinetic analysis indicated that the catalytic activity of Co:CeO2 is up to 5.6 times higher than that of pristine CeO2. Thus, this work demonstrates a synergistic strategy integrating machine learning prediction, descriptor-based mechanistic interpretation and experimental validation, providing an efficient approach for the design and screening of high-performance hydrogen oxidation catalysts.

Co-doping of ions effectively modulates structures and properties of functional ceramic materials. This study fabricated the Mg2Al4Si5-x(Mn0.5Ti0.5)xO18 (0 <= x <= 0.16) ceramic via solid-state reaction method and achieved remarkable dielectric properties, with values of epsilon r = 4.907, Q x f = 159 681 GHz, and tau f = -21.075 ppm degrees C-1. The intricate connection between microwave dielectric characteristics and crystalline framework received comprehensive examination through the lens of the complex chemical bond theory. The dielectric constant (epsilon r) of Mg2Al4Si5-x(Mn0.5Ti0.5)xO18 (0 <= x <= 0.16) ceramics primarily depends on material density, bond ionization, and ionic polarization capacity. The quality factor (Q x f) rose 2.24-fold due principally to enhanced lattice energy, with this Q x f value also correlating to the symmetry of [Si4Al2] and [O6] hexagonal rings within the pyroxene crystal structure. The temperature coefficient of the resonant frequency (tau f) is mainly attributed to the bond energy and deformation of the [MgO6] octahedra. This study innovatively employs (Mn0.5Ti0.5)4+ to co-dope the Si4+ sites in Mg2Al4Si5O18 based on ionic radius matching, achieving synergistic optimization of Q x f and tau f. These findings offer critical guidance for developing silica ceramics featuring elevated Q x f values and near-zero tau f characteristics for 6G communication systems.

The explosive growth of artificial intelligence (AI) servers and high-performance computing (HPC) is driving an urgent demand for ultra-thin base-metal-electrode multilayer ceramic capacitors (BME-MLCCs) with superior reliability under high electric fields and elevated temperatures. Here, 150 nm BaTiO3 nanopowders were doped with high Dy concentrations (1.5–3.0 mol