Large EB Research Articles

Hierarchical Self-Aggregation of Multifunctional Steviol Glycosides in Aqueous Solutions.

Steviol glycosides (SGs) are a natural sweetener widely used in the food and beverage industry, but the low solubility and stability of SG aqueous solutions greatly limit their application performance, especially in liquid formulations. In this work, we explore the solubility behavior of rebaudioside A (Reb A) in water, a major component of SGs, with the aim of clarifying the underlying mechanisms of the solubility and stability constraints of SGs, as well as the impact on their multifunctional properties. We demonstrate for the first time that Reb A exhibits hierarchical self-assembly in solutions, forming spherical micelles first when the concentration exceeds its critical micelle concentration (5.071 mg/mL), which then further assemble into large rod-like aggregates. The formation of such large Reb A aggregates is mainly dominated by hydrogen bonding and short-range Coulomb interaction energy, thus leading to the low solubility and precipitation of Reb A solutions. Surprisingly, aggregated Reb A structures display significantly improved organoleptic properties, revealing that self-aggregation can be developed as a simple, efficient, and green strategy for improving the taste profile of SGs. Additionally, the self-aggregation of Reb A at high concentrations impairs active encapsulation and also affects its interfacial and emulsifying properties.

Enhanced energy storage performance in Ag(Nb,Ta)O3 films via interface engineering

Dielectric capacitors with ultrahigh power density and ultra-fast charge/discharge rate are highly desired in pulse power fields. Environmental-friendly AgNbO3 family have been actively studied for its large polarization and antiferroelectric nature, which greatly boost the electric energy storage performance. However, high-quality AgNbO3-based films are difficult to fabricate, leading to a low breakdown field Eb (<1.2 MV/cm) and consequently arising inferior energy storage performance. In this work, we propose an interface engineering strategy to mitigate the breakdown field issue. A Ag(Nb,Ta)O3/BaTiO3 bilayer film is proposed, where the BaTiO3 layer acts as a p-type semiconductor while Ag(Nb,Ta)O3 layer is n-type, together with the n-type LaNiO3 buffer layer on the substrate, forming an n-p-n heterostructure. The n-p-n heterostructure elevates the potential barriers for charge transport, greatly reducing the leakage current. An extremely large breakdown field Eb∼4.3 MV/cm is achieved, being the highest value up to date in the niobate system. A high recoverable energy density Wrec∼62.3 J/cm3 and a decent efficiency η∼72.3% are obtained, much superior to that of the Ag(Nb,Ta)O3 monolayer film (Wrec∼46.4 J/cm3 and η∼80.3% at Eb∼3.3 MV/cm). Our results indicate that interface engineering is an effective method to boost energy storage performance of dielectric film capacitors.

Excellent energy storage performance with high breakdown strength in Nb2O5-modified (Bi0.5Na0.5)TiO3-based ceramics

The development of lead-free dielectric capacitors with good energy storage performance and high reliability is of great practical significance for pulsed power systems. In this study, Nb2O5-modified 0.6(Bi0.5Na0.5)TiO3-0.4(Sr0.7Bi0.2)TiO3 (BNT-SBT-xNb, 0 ≤ x ≤ 0.07) ceramics were designed to enhance their energy storage performance and prepared using a hydrothermal method. The results show that Nb doping into the B site of BNT-SBT can induce lattice expansion and promote polar nanoregions, resulting in improved dielectric relaxation behavior. Moreover, the introduction of Nb can lead to the refinement of grain size, the increase in resistivity, the reduction of oxygen vacancies, and the broadening of band gap, thereby significantly enhancing the electrical breakdown strength (Eb). Accordingly, the BNT-SBT-0.05Nb system presents excellent energy storage performance with high Wrec ∼6.26 J/cm3 and η ∼87.9 % under an large Eb of 518 kV/cm in accompany with the wide temperature stability (Wrec and η vary within ±6.8 % and ±3.2 % at 40–100 °C). The significant improvement of Eb and energy storage performance demonstrates that the BNT-SBT-0.05Nb system is a potential candidate for applications in high-energy storage capacitors.

Π‐Skeleton Tailoring of Olefin‐Linked Covalent Organic Frameworks Achieving Low Exciton Binding Energy for Photo‐Enhanced Uranium Extraction from Seawater

AbstractAdsorption‐photocatalysis technology based on covalent organic frameworks (COFs) offers an alternative method for advancing the field of uranium extraction from seawater. When determining the photocatalytic activity of COFs, the binding energy of excitons (Eb) functions is the decisive factor. Nevertheless, the majority of reported COFs have a large Eb, which seriously restricts their application in the field of photocatalysis. Using a practical π‐skeleton engineering strategy, the current study synthesizes three donor‐acceptor olefin‐linked COFs containing amidoxime units in an effort to minimize Eb. Theoretical and experimental results reveal that the construction of planar and continuous π‐electron delocalization channels can significantly reduce Eb and promote the separation of electron‐hole pairs, thereby enhancing the photocatalytic activities. Moreover, the Eb of the TTh‐COF‐AO with a planar π‐skeleton donor is significantly reduced, and exhibits a substantially smaller Eb (38.4 meV). Under visible light irradiation, a high photo‐enhanced uranium extraction capacity of 10.24 mg g−1 is achieved from natural seawater without the addition of sacrificial reagents, which is superior to the majority of olefin‐linked COFs that have been reported to date. This study, therefore, paves the way for the development of tailored, efficient COFs photocatalysts for the extraction of uranium from seawater.

Ultrahigh Energy Storage Density in Superparaelectric-Like Hf0.2 Zr0.8 O2 Electrostatic Supercapacitors.

Electrostatic capacitors attract great interest in energy storage fields due to their advantages of high power-density, fast charge/discharge speed, and great reliability. Intensive efforts have been placed on the development of high-energy-density of capacitors. Herein, a novel supercapacitor with Hf0.2 Zr0.8 O2 /xAl2 O3 /Hf0.2 Zr0.8 O2 (HAHx) is designed to improve the breakdown strength (Eb ) through optimizing Al2 O3 (AO) film thickness. Low-temperature annealing is first proposed to enhance the polarization difference (Pm -Pr ) due to the formation of dispersed polar nanoregions, which is called "superparaelectric-like" similar to previous super-paraelectric behavior of perovskite structures. As results, both large Eb and Pm -Pr values are obtained, leading to an ultrahigh energy storage density of 87.66 Jcm-3 with a high efficiency of 68.6%, as well as a reliable endurance of 107 cycles. This work provides a feasible pathway to improve both the polarization difference and breakdown strength of HfO2 -based films by the combination of insulation insertion layer and low-temperature annealing. The proposed strategy can contribute to the realization of high-performance electrostatic supercapacitors with excellent microsystem compatibility.

Enhanced energy storage efficiency of Ba0.8Sr0.2TiO3 ceramics modified by BiTaO3

Lead-free (1-x)Ba0.8Sr0.2TiO3-xBiTaO3 (BST-xBTA) ceramics were prepared via a solid-state reaction process. The effect of BTA addition on the energy storage properties of BST ceramics was investigated. The pure perovskite phases were found in the BST-xBTA ceramic samples as x ≤ 0.12. With the increasing BTA content, the maximum breakdown strength (Eb) reached 130 kV/cm at x = 0.12, twice that of the undoped samples. The large Eb and slim ferroelectric loops of the 0.88BST-0.12BTA ceramics indicated an advantageous energy density of Wrec ∼0.526 J/cm3 and a high energy efficiency of η ∼98% at 130 kV/cm. The low dielectric loss and high η make this ceramic system a promising material applying pulsed-powder devices.

Prediction and Validation for Welding Deformation of the Upper Port Stub

The vacuum vessel (VV) as an ultrahigh vacuum pressure vessel is one of the essential components of the Chinese Fusion Engineering Test Reactor (CFETR) device. VV has strict position tolerance. The VV port stub is a typical large-scaled welded structure manufactured by electron beam welding (EBW) technique. Welding has the most significant influence on deformation. Therefore, it is essential to analyze welding deformation. A systematic welding simulation method aimed at welding deformation controlling for a large EB welded structure is proposed in this article. First, the dynamic process of EBW of 50-mm-thick ultralow carbon austenitic stainless steel was simulated based on the thermal elastoplastic theory. The weld forming mechanism of high energy density welding of the thick plate was revealed. Then the inherent strain extracted from the results of the simulation of local welding was introduced to the simulation of tailor welding of the port stub. Finally, optimal welding sequence and clamping conditions were obtained, and the reliability of the simulation was verified by the profile measurement results of the inner shell of the upper port stub.

Significantly Enhanced Energy Storage Performance of Lead-Free BiFeO3-Based Ceramics via Synergic Optimization Strategy.

Owing to the merits of giant power density and ultrafast charge-discharge time, dielectric capacitors including ceramics and films have inspired increasing interest lately. Nevertheless, the energy storage density of dielectric ceramics should be further optimized to cater to the boosting demand for the compact and portable electronic devices. Herein, an ultrahigh recoverable energy storage density Wrec of 13.44 J/cm3 and a high efficiency η of 90.14% are simultaneously realized in BiFeO3-BaTiO3-NaTaO3 relaxor ferroelectric ceramics with high polarization Pmax, reduced remanent polarization Pr, and optimized electric breakdown strength Eb. High Pmax originates from the genes of BiFeO3-based ceramics, and reduced Pr is induced by enhanced relaxor behavior. Particularly, a large Eb is achieved by the synergic contributions from complicated internal and external factors, such as decreased grain size and improved resistivity and electrical homogeneity. Furthermore, the ceramics also exhibit satisfactory frequency, cycling and thermal reliability, and decent charge-discharge property. This work not only indicates that the BiFeO3-based relaxor ferroelectric materials are promising choices for the next-generation electrostatic capacitors but also paves a potential approach to exploit novel high-performance dielectric ceramics.

Realizing enhanced energy storage performances in (Bi0.5Na0.5)0.7Sr0.3TiO3-based relaxor ferroelectrics via components regulation

For (Na0.5Bi0.5)0.7Sr0.3TiO3-based relaxor ferroelectrics, the early polarization saturation and low breakdown electric field (Eb) are considered critical bottlenecks. As a result, the further development of this kind of promising material is severely restricted. Along these lines, in this work, comprehensive energy storage performances were achieved by the Bi(Mg2/3Ta1/3)O3 modified (Bi0.5Na0.5)0.7Sr0.3TiO3 ceramics [abbreviated as (1-x)BNST-xBMT]. The restrained rapid polarization saturation and large difference in the polarization were observed by the domain relaxor behavior. The improved microstructures and decreased grain sizes further enhanced the Eb values of BNST-based ceramics. Consequently, the suppressing premature saturation polarization, large polarization difference and high Eb value synergistically contributed to the enhanced comprehensive energy storage performances [the recoverable energy density Wrec of >3.0 J/cm3 and efficiency η of >85.0%]. Impressive stabilities of temperature (20 °C–200 °C) and frequency (1 Hz–200 Hz) were also demonstrated for the corresponding ceramics. Our results pave the way for improving the energy storage properties and further promoting the development of BNST-based ceramics.

Enhanced Energy Storage Performance in Paraelectric–Ferroelectric Bipolymer-Based PMMA-P(VDF-HFP) Composite Films via Polydopamine-Coated KNb3O8 Fillers

Enhancing the breakdown strength (Eb) and polarization of the polymer-based composites through improving the effective interface bonding between the inorganic fillers and polymer matrix is always pursued to achieve high electrostatic energy storage performances. Along with this, paraelectric–ferroelectric (P–F) structured bipolymer PMMA-P(VDF-HFP) was copolymerized and blended to maintain the high Eb but reduce the residual polarization, and meanwhile, potassium triniobate (KNb3O8) rods synthesized by a molten salt (KCl and K2SO4) method were surface-modified using a polydopamine (PDA) shell to form fillers for the fabrication of the composite films that were prepared by a solution casting process. The fabricated PDA@KNb3O8/PMMA-P(VDF-HFP) composite film by filling only a tiny amount of PDA@KNb3O8 (1.0 wt %) exhibits a much enhanced dielectric constant (ε ∼ 9) and polarization (Pmax ∼ 6.9) and large Eb (∼600 MV m–1), therefore giving rise to a high energy density of 15.30 J cm–3 combined with a discharge energy efficiency of 65%. The results herein can be comparative and superior to those of many high-energy storage inorganic–polymer systems that may render this system much potential for dielectric energy storage capacitors.

Energy storage performance of BiFeO3–SrTiO3–BaTiO3 relaxor ferroelectric ceramics

AbstractDielectric capacitors reveal great potential in the application of high power and/or pulsed power electronic devices owing to their ultrafast charge–discharge rate and ultrahigh power density. Among various dielectric capacitors, the environment‐friendly lead‐free dielectric ceramics have drawn extensive investigations in recent years. Nevertheless, the relatively small recoverable energy storage density (Wrec) is still an obstacle for their application. Herein, the (0.55−x)BiFeO3–0.45SrTiO3–xBaTiO3 ternary ceramics with 0.1 wt% MnO2 were prepared by the solid‐state reaction, and achieved enhanced relaxor behavior as well as breakdown strength Eb. As a result, the x = 0.12 ceramic exhibited superior comprehensive energy storage performance of large Eb (50.4 kV/mm), ultrahigh Wrec (7.3 J/cm3), high efficiency η (86.3%), relatively fast charge–discharge speed (t0.9 = 6.1 μs) and outstanding reliability under different frequency, fatigue, and temperature, indicating that the BiFeO3‐based relaxor ferroelectric ceramics are prospective alternatives for electrostatic energy storage.

Grain size engineered (Ba,Sr)(Zr,Ti)O3 ceramics with excellent energy storage properties for high-voltage pulsed capacitors

The macroscopic physical properties of functional ceramics are strongly affected by grain morphology, almost resulting from the sintering process. For a given ceramic material, it has been experimentally confirmed that the enhancement of dielectric breakdown strength Eb can largely increase energy storage density (W). An effective method to increase Eb of ceramic materials is the control of grain morphology. Herein, the (Ba0.95Sr0.05)(Zr0.2Ti0.8)O3 ceramics have been intensively investigated by different sintering techniques to improve grain morphology. Compared with single-step sintering, two-step sintering can sharply inhibit grain growth and make size distribution uniform, which is conducive to the increase in the Eb. A competitive energy storage capacity can be achieved with a high Wch of 3.78 J/cm3, a high Wdi of 3.50 J/cm3, and a high η of 92.6% by two-step sintering due to large Eb of 350 kV/cm, accompanied with good thermal stability till to 160 °C and good fatigue characteristics up to 105 cycles, indicating that two-step sintering is an effective strategy of engineering grain morphology.

Density functional theory studies on C20 with substitutional TinNn impurities

In this paper, we have performed systematic theoretical surveys of C20 and its C20-2nTinNn nanocages with n = 1-8 at DFT. Full optimization indicates none of the structures collapse to open deformed as segregated heterofullerene. Also, in order to avoid the resulted strain of fused five-pentagon configuration, some of them deform their cage at the Ti-N bonds and appear cubic-like. Binding energy (Eb) increases, and the absolute heat of atomization │ΔHat│ of the designed C20-2nTinNn structures decreases, respectively, as the number of substituting Ti-N units increases. The calculated Eb of 57.05eV/atom and │ΔHat│ of 2437.40kcal/mol display C4Ti8N8 as the most thermodynamic stable heterofullerene where including eight separated Ti-N units through two double C═C bonds. In contrast, the calculated band gap of 2.06eV shows C18Ti1N1 as the best-insulated heterofullerene. Here isolable or extractable open-shell C18Ti1N1 heterofullerene must be kinetic stable species, and closed-shell C4Ti8N8 should be thermodynamic stable species. Compared to the suggested Ti-decorated B38 fullerene as a high capacity hydrogen storage material with large Eb (5.67eV/atom), our studied C20-2nTinNn heterofullerenes show the higher Eb with a range of 13.78 to 57.05eV/atom, the higher stability, and the higher capacity hydrogen storage. Each Ti-N unit can bind up to two hydrogen molecules with an average adsorption energy of 0.073eV/H2. While the C4Ti8N8 fullerene substituted with 8 Ti-N units can store 16 H2 molecules, the hydrogen gravimetric density (the hydrogen storage capacity) reaches up to 5.61 wt% with an average adsorption energy of 0.587eV/H2. Based on these results, we infer that C4Ti8N8 fullerene is a potential material for hydrogen storage with high capacity and might motivate active experimental efforts in designing hydrogen storage media.

Simultaneously increased discharged energy density and efficiency in bilayer-structured nanocomposites with AgNbO3 lead-free antiferroelectric nanofillers

PI–AgNbO3 NPs/P(VDF-HFP) bilayer nanocomposites possess slim D–E loops, large Eb, and high Dmax, thus displaying simultaneously a large Ue of 13.77 J cm−3 and high η of 86.87%.

Simultaneous achievement of ultrahigh energy storage density and high efficiency in BiFeO3-based relaxor ferroelectric ceramics via a highly disordered multicomponent design

The synergistic contributions of high Pmax, small Pr and large Eb endow the BiFeO3-based ceramics with relaxor ferroelectric characteristics, due to which an ultrahigh Wrec of 13.9 J cm−3 and high η of 89.6% have been achieved synchronously.

Remarkably enhanced recoverable energy density in lead-free relaxor Ba0.94Ca0.06Ti1−xSnxO3 ceramics by the synergistic effect of nano-domains and refined grains

High-performance dielectric ceramic capacitors is a promising candidate in energy storage devices. In this work, the energy storage performance of Ba0.94Ca0.06Ti1−xSnxO3 (x = 0.04, 0.08, 0.12, 0.16) ceramics was systematically studied. Through modifying Sn4+ doping content, the breakdown strength of the ceramics is enhanced by 112.3% from 133.4 kV/cm (Ba0.94Ca0.06Ti0.96Sn0.04O3) to 283.2 kV/cm (Ba0.94Ca0.06Ti0.84Sn0.16O3). Accordingly, the recoverable energy density is greatly increased by 276.2%, that is, from 0.42 J/cm3 grow to 1.58 J/cm3. The enhanced energy storage properties could be ascribed to the following aspects: (1) the doping of Sn4+ with a larger ionic radius inhibits the migration of grain boundaries and therefore refines grains, resulting in a higher activation energy and a larger Eb; (2) the long range polar order is broke and polar nano-regions are formed, giving rise to lower energy barrier and smaller Pr; (3) the weakened ferroelectricity and delayed polarization saturation lead to higher Wrec owing to the fact that Sn4+ with d10 electronic configurations substitutes Ti4+ with d0. Our work provides a novel approach for enhancing energy storage performance in dielectric ceramic capacitors.

Ultrafast and High-Yield Polaronic Exciton Dissociation in Two-Dimensional Perovskites.

Layered two-dimensional (2D) lead halide perovskites are a class of quantum well (QW) materials, holding dramatic potentials for optical and optoelectronic applications. However, the thermally activated exciton dissociation into free carriers in 2D perovskites, a key property that determines their optoelectronic performance, was predicted to be weak due to large exciton binding energy (Eb, about 100-400 meV). Herein, in contrast to the theoretical prediction, we discover an ultrafast (<1.4 ps) and highly efficient (>80%) internal exciton dissociation in (PEA)2(MA)n-1PbnI3n+1 (PEA = C6H5C2H4NH3+, MA = CH3NH3+, n = 2-4) 2D perovskites despite the large Eb. We demonstrate that the exciton dissociation activity in 2D perovskites is significantly promoted because of the formation of exciton-polarons with considerably reduced exciton binding energy (down to a few tens of millielectronvolts) by the polaronic screening effect. This ultrafast and high-yield exciton dissociation limits the photoluminescence of 2D perovskites but on the other hand well explains their exceptional performance in photovoltaic devices. The finding should represent a common exciton property in the 2D hybrid perovskite family and provide a guideline for their rational applications in light emitting and photovoltaics.

Intra-unitcell cluster-cluster magnetic compensation and large exchange bias in cubic alloys

Composite quantum materials are the ideal examples of multifunctional systems, which simultaneously host more than one novel quantum phenomenon in physics. Here, we present a combined theoretical and experimental study to demonstrate the presence of an extremely large exchange bias in the range 0.8--2.7 T and a fully compensated magnetic state (FCF) in a special type of Pt and Ni-doped ${\mathrm{Mn}}_{3}\mathrm{In}$ cubic alloy. Here, oppositely aligned uncompensated moments in two different atomic clusters sum up to zero, which are responsible for the FCF state. Our density functional theory (DFT) calculations show the existence of several possible ferrimagnetic configurations with the FCF as the energetically most stable one. The microscopic origin of the large exchange bias can be interpreted in terms of the exchange interaction between the FCF background and the uncompensated ferrimagnetic clusters stabilized due to its negligible energy difference with respect to the FCF phase. We utilize pulsed magnetic field up to 60 T and 30 T static-field magnetization measurements to confirm the intrinsic nature of exchange bias in our system. Finally, our Hall effect measurements demonstrate the importance of uncompensated noncoplanar interfacial moments for the realization of large EB. The present finding of gigantic exchange bias in a unique compensated ferrimagnetic system opens up a direction for the design of novel quantum phenomena for the technological applications.

Spin-glass mediated large exchange bias and coercivity in hexagonal Mn1+xCu1−xGa (x = 0.3–0.5) alloys

Ni2In-type MnMX alloys possess interesting noncollinear magnetic structures that may embed a variety of physical phenomena. In this work, magnetic and electrical transport properties of pure Ni2In-type structure Mn1 +xCu1−xGa (x = 0.3–0.5) alloys are investigated systematically. A cluster spin-glass phase is identified below the Curie temperature by magnetization and ac susceptibility measurements in x = 0.5 sample. Mediated by the exchange interaction between Mn-Mn clusters, significant exchange bias effect and coercivity are established, in which a giant exchange bias field of up to 0.323 T is observed in x = 0.5 sample. The exchange bias effect and coercivity, as well as the anomalous Hall effect are found to be greatly tuned via field cooling process. The large EB and coercivity identified in Mn–Cu–Ga alloys make them potentially applied in rare-earth-free magnets and spintronic devices.

Correction Method for Hydraulic Conductivity Measurements Made Using a Fixed Wall Permeameter

Hydraulic conductivity measurement through a fixed wall permeameter is a common practice to obtain the fluid transmissibility characteristics of soil matrix; however, sidewall leakage due to rigid wall effect may significantly influence the observed values for coarse-grained soils. In this study, the boundary flow error was identified through characterizing the geometrical properties of voids adjacent to the sidewall, and a parameter known as the boundary void ratio (eb) was proposed to account for this effect. The findings suggest that a fixed wall cell containing coarse soils would unavoidably generate extra voids at the interface between soil grains and inner rigid wall, contributing to a larger eb at the wall than void ratio within the soil bed; the measured hydraulic conductivity is increased primarily due to the apparatus-induced error. A two-dimensional geometric model was then established to estimate the eb value for uniformly sized coarse soils confined by a rigid permeameter wall, based on which a method was obtained for eliminating the boundary flow error from a fixed wall cell. The mathematical method was finally validated against experimental data from existing literature. It can be concluded that the boundary condition at sidewall featuring unwanted gaps lead to overestimation of the coefficient of permeability; however, the proposed correction method could adequately eliminate the boundary flow error for uniformly sized coarse-grained soils tested within a rigid wall cell.