[Effects of Biochar Application on the Structure and Function of Fungal Community in Continuous Cropping Watermelon Soil].

This study was conducted to clarify the long-term effects of biochar application on the structure and function of the fungal community in continuous cropping watermelon soil. Taking watermelon root soil as the research object, Illumina NovaSeq high-throughput sequencing and FUNGuild platform were used to analyze the differences in soil fungal community composition, diversity, and function after 3-year biochar additions of 7.5, 15.0, and 30.0 t·hm-2 and to explore the correlation between soil environmental factors and fungal community structure under the control of biochar. The results showed that compared to that in the absence of biochar (control), the soil pH, available phosphorus, available potassium, total nitrogen, organic matter, and cation exchange capacity increased, but available nitrogen decreased with biochar addition. High-throughput sequencing results showed that biochar amendment improved the fungal community structure in continuous cropping watermelon soil and increased the richness and diversity of soil fungi. A total of 922 OTU were obtained from all soil samples, and the species annotation results indicated that the dominant fungal groups were Ascomycota, Basidiomycota, Mortierellomycota, Chytridiomycota, and Glomeromycota, with these phyla accounting for 85.70 %-92.45 % of the total sequences.The relative abundance of Ascomycota and Basidiomycota decreased, whereas the abundance of Mortierellomycota and Glomeromycota increased with biochar addition.At the genus level, the application of biochar increased the relative abundance of Mortierella and Rhizophlyctis but decreased the abundance of Fusarium. The Mantel test showed that soil available potassium, available nitrogen, organic matter, and pH were the main environmental factors leading to the shift in the soil fungal community composition.The functional prediction with FUNGuild showed that the many nutrient types among the different treatments were saprotrophic, pathotrophic, and symbiotrophic. The relative abundance of pathotrophs significantly decreased, but the abundance of symbiotrophs significantly increased with the medium and high doses of biochar treatment. In conclusion, the application of biochar changed the soil physicochemical properties, promoted the development of soil fungal community structure and functional groups in a healthy and beneficial direction, and improved the quality of continuous cropping watermelon soil.

Breaking the Mutual Constraint between Polarization and Voltage Resistance with Nanograined High-Entropy Ceramic.

Dielectric ceramics with a high energy storage capacity are key to advanced pulsed power capacitors. However, conventional materials face a mutual constraint between polarization strength and the breakdown strength bottleneck. To address this limitation, the concept of nanograined high-entropy ceramics is introduced in this work. By introducing a large number of constituent elements into the A-site of perovskite material lattice, high-entropy (Bi0.2K0.2Ba0.2Sr0.2Ca0.2)TiO3-0.2 'CuO relaxor ceramic with nanoscale grains have been successfully prepared, which breaks the mutual constraint between polarization strength and breakdown strength bottleneck and results a recoverable energy density (Wrec ∼ 6.86 J/cm3) and an efficiency (η ∼ 87.7%) at 670 kV/cm. Moreover, its excellent stability makes it potentially useful under a variety of extreme conditions, including at high temperatures and high/low frequencies. These obtained results demonstrate that this nanograined high-entropy lead-free perovskite ceramic has great potential for energy storage applications.

Improved Leakage Behavior at High Temperature via Engineering of Ferroelectric Sandwich Structures.

The leakage behavior of ferroelectric film has an important effect on energy storage characteristics. Understanding and controlling the leakage mechanism of ferroelectric film at different temperatures can effectively improve its wide-temperature storage performance. Here, the structures of a 1 mol% SiO2-doped BaZr0.35Ti0.65O3 (BZTS) layer sandwiched between two undoped BaZr0.35Ti0.65O3 (BZT35) layers was demonstrated, and the leakage mechanism was analyzed compared with BZT35 and BZTS single-layer film. It was found that interface-limited conduction of Schottky (S) emission and the Fowler-Nordheim (F-N) tunneling existing in BZT35 and BZTS films under high temperature and a high electric field are the main source of the increase of leakage current and the decrease of energy storage efficiency at high temperature. Only an ohmic conductive mechanism exists in the whole temperature range of BZT35/BZTS/BZT35(1:1:1) sandwich structure films, indicating that sandwich multilayer films can effectively simulate the occurrence of interface-limited conductive mechanisms and mention the energy storage characteristics under high temperature.

Enhanced Energy Storage Performance of Lead-Free Capacitors in an Ultrawide Temperature Range via Engineering Paraferroelectric and Relaxor Ferroelectric Multilayer Films.

Industry has been seeking a thin-film capacitor that can work at high temperature in a harsh environment, where cooling systems are not desired. Up to now, the working temperature of the thin-film capacitor is still limited up to 200 °C. Herein, we design a multilayer structure with layers of paraferroelectric (Ba0.3Sr0.7TiO3, BST) and relaxor ferroelectric (0.85BaTiO3-0.15Bi(Mg0.5Zr0.5)O3, BT-BMZ) to realize optimum properties with a flat platform of dielectric constant and high breakdown strength for excellent energy storage performance at high temperature. Through optimizing the multilayer structure, a highly stable relaxor ferroelectric state is obtained for the BST/BT-BMZ multilayer thin-film capacitor with a total thickness of 230 nm, a period number N = 8, and a layer thickness ratio of BST/BT-BMZ = 3/7. The optimized multilayer film shows significantly improved energy storage density (up to 30.64 J/cm3) and energy storage efficiency (over 70.93%) in an ultrawide temperature range from room temperature to 250 °C. Moreover, the multilayer system also exhibits excellent thermal stability in such an ultrawide temperature range with a change of 5.15 and 12.75% for the recoverable energy density and energy storage efficiency, respectively. Our results demonstrate that the designed thin-film capacitor is promising for the application in a harsh environment and open a way to tailor a thin-film capacitor toward higher working temperature with enhanced energy storage performance.