Changes in the physicochemical property and sensory quality of heat-processed beef flavour in the storage process

This study aimed to investigate changes in the quality of heat-processed beef flavour (HPBF) during 168-day storage period at 4, 20 and 50 °C through evaluating 10 physicochemical indexes and sensory profiles. The sensory score of HPBF reduced dramatically at 50 °C compared with those at other temperatures. The correlation analysis indicated that among the 10 physicochemical indexes, oxidation–reduction potential (ORP), which is positively correlated to lipid oxidation, possessed the strongest association with the total sensory score of HPBF. The kinetic analysis showed that the increasing rate of ORP during the first 50-day period at 50 °C was more than 10 times larger than those at 4 and 20 °C. These results suggested that lipid oxidation played a major role in affecting the quality of HPBF, especially during the early storage period. Reducing lipid oxidation via for instance maintaining a relatively low storage temperature should be given better attention for obtaining high-quality HPBF.     

Interfacial bonding mechanism and joint weakness area of brazed SiC and Nb with AuNi filler alloy: First-principles and experimental perspective

The implementation of Ni-based brazing filler metal for bonding SiC to metals can effectively expand the high-temperature applications of SiC-based composite materials. To reduce the excessive brittle phases formed in the reaction between SiC/Ni, this study used Au, a chemically stable element, as an additive to investigate the experimental mechanism of Au regulating the reaction between Ni and SiC. The study found that under certain temperature and reaction time conditions, Au can hinder the diffusion of Ni into SiC while suppressing the reaction between Ni and SiC at the interface. The microstructure evolution of the SiC-Nb joint brazed with an AuNi alloy was investigated, and the theoretical analysis was verified. The optimized mechanical strength reached 30 MPa. Based on experimental and theoretical analysis, the weakness area of the joint was identified and the formation mechanism was analyzed. Importantly, the interface behavior analysis obtained in this study can provide some new ideas for the optimization of alloy composition in brazing experiments.     

Defect Dipole-Induced Fatigue Strain Recoverability in Lead-Free Piezoelectric Ceramics

Piezoelectric ceramics have garnered extensive utilization in high-precision actuators, where the magnitude of electric field-induced strain and fatigue resistance play crucial roles in actuation applications. Herein, an innovative strategy based on defect dipoles is proposed to form a defect-engineered polymorphic phase transition and achieve a giant piezoelectric strain coefficient of 3080 pm V⁻¹ in Li/Sr-doped (K_0.5Na_0.5)NbO₃ lead-free piezoceramics. The mechanism responsible for the enhanced strain performance lies in the optimized strain compatibility between the refined stripe domains and the nanosized domains. Additionally, the results demonstrate that the material is able to recover from fatigue-induced strain depletion under the stimulation of bipolar electric fields. This property can be phenomenologically explained by the rigid ion model, in which the application of reversal electric fields can facilitate the restoration of defect dipoles, thereby greatly contributing to strain recoverability. This study establishes a close correlation between the unipolar strain properties and the inherent flexibility of defect dipoles and provides new insight into the design of high-reliability, large-stroke piezoceramics.     

Giant Electric Field-Induced Strain with High Temperature-Stability in Textured KNN-Based Piezoceramics for Actuator Applications

Large-strain (K,Na)NbO₃ (KNN) based piezoceramics are attractive for next-generation actuators because of growing environmental concerns. However, inferior performance with poor temperature stability greatly hinders their industrialized procedure. Herein, a feasible strategy is proposed by introducing ${\mathrm{V}}_{\text{K/Na}}^{{}^{\prime }}$-${\mathrm{V}}_{\stackrel{\mathrm{..}}{\mathrm{O}}}$ defect dipoles and constructing grain orientation to enhance the strain performance and temperature stability of KNN-based piezoceramics. This textured ceramics with 90.3% texture degree exhibit a giant strain (1.35%) and a large converse piezoelectric coefficient d₃₃^* (2700 pm V⁻¹), outperforming most lead-free piezoceramics and even some single crystals. Meanwhile, the strain deviation at high temperature of 100 °C–200 °C is obviously alleviated from 61% to 35% through texture engineering. From the perspective of practical applications, piezo-actuators are commonly utilized in the form of multilayer. In order to illustrate the applicability on multilayer actuators, a stack-type actuator consisted of 5 layers of 0.4 mm thick ceramics is fabricated. It can generate large field-induced displacement (11.6 µm), and the promising potential in precise positioning and optical modulation are further demonstrated. This work provides a textured KNN-based piezoceramic with temperature-stable giant strain properties, and facilitates the lead-free piezoceramic materials in actuator applications.     

Unusual Post Modulation of Pore Size,Nanostructure, and Composition of Metal–Organic Frameworks via Cooperative Ozone/Water Co-Etching

Rational engineering of pore structure and size, nanostructure, and local composition of metal-organic frameworks (MOFs) plays a crucial role for their applications. Herein, a facile O₃/H₂O co-etching strategy is reported to treat ZIF-67 to synthesize derivatives with novel and hard-to-acquire structures and properties, including mesoporous ZIF-67 dodecahedra with variable mesopore sizes (3–30 nm), core–shell and core-void-shell mesoporous ZIF-67@amorphous cobalt hydroxide dodecahedra, and hollow dodecahedral frameworks. In the cooperative etching mechanism, O₃ diffuses into the hydrophobic ZIF-67 to progressively oxidize the ligand to create functional groups, mesopores and voids, while the enhanced hydrophilicity and pore size allow H₂O to diffuse inside to hydrolyze the metal centers to form cobalt hydroxide shells. The co-etching boosts the performance of ZIF-67 in the electrocatalytic oxygen evolution reaction. The derived core-void-shell material possesses a highly attractive performance (an overpotential of 286 mV, a Tafel slope of 59.5 mV dec⁻¹, and a stability of >20 h) because of the presence of amorphous cobalt species, large pores, hierarchal structure, and high hydrophilicity. This work provides a general approach for post engineering of MOFs to create novel structures and functionalities.     

Insight of BaCe0.5Fe0.5O3−δ twin perovskite oxide composite for solid oxide electrochemical cells

One-pot synthesized twin perovskite oxide composite of BaCe_0.5Fe_0.5O_3−δ (BCF), comprising cubic and orthorhombic perovskite phases, shows triple-conducting properties for promising solid oxide electrochemical cells. Phase composition evolution of BCF under various conditions was systematically investigated, revealing that the cubic perovskite phase could be fully/partially reduced into the orthorhombic phase under certain conditions. The reduction happened between the two phases at the interface, leading to the microstructure change. As a result, the corresponding apparent conducting properties also changed due to the difference between predominant conduction properties for each phase. Based on the revealed phase composition, microstructure, and electrochemical properties changes, a deep understanding of BCF's application in different conditions (oxidizing atmospheres, reducing/oxidizing gradients, cathodic conditions, and anodic conditions) was achieved. Triple-conducting property (H⁺/O²⁻/e⁻), fast open-circuit voltage response (∼16–∼470 mV) for gradients change, and improved single-cell performance (∼31% lower polarization resistance at 600°C) were comprehensively demonstrated. Besides, the performance was analyzed under anodic conditions, which showed that the microstructure and phase change significantly affected the anodic behavior.     

Oriented Assembled Prussian Blue Analogue Framework for Confined Catalytic Decomposition of Ammonium Perchlorate

The design of highly dispersed active sites of hollow materials and unique contact behavior with the components to be catalyzed provide infinite possibilities for exploring the limits of catalyst capacity. In this study, the synthesis strategy of highly open 3-dimensional frame structure Prussian blue analogues (CoFe-PBA) was explored through structure self-transformation, which was jointly guided by template mediated epitaxial growth, restricted assembly and directional assembly. Additionally, good application prospect of CoFe-PBA as combustion catalyst was discussed. The results show that unexpected thermal decomposition behavior can be achieved by limiting AP(ammonium perchlorate) to the framework of CoFe-PBA. The high temperature decomposition stage of AP can be advanced to 283.6 °C and the weight loss rate can reach 390.03% min⁻¹. In-situ monitoring shows that CoFe-PBA can accelerate the formation of NO and NO₂. The calculation of reaction kinetics proved that catalytic process was realized by increasing the nucleation factor. On this basis, the catalytic mechanism of CoFe-PBA on the thermal decomposition of AP was discussed, and the possible interaction process between AP and CoFe-PBA during heating was proposed. At the same time, another interesting functional behavior to prevent AP from caking was discussed.     

Influence of Electron Beam Powder Bed Fusion Process Parameters on Transformation Temperatures and Pseudoelasticity of Shape Memory Nickel Titanium

Electron beam powder bed fusion (PBF-EB) is used to manufacture dense nickel titanium parts using various parameter sets, including the beam current, scan speed, and postcooling condition. The density of manufactured NiTi parts is investigated in relation to the linear energy input. The results imply that the part density increases with increasing linear energy density to over 98% of the bulk density. With a constant energy input, a combination of low power and low scan speed leads to denser parts. This is attributed to lower electrostatic repulsive forces from lower number density of the impacting electrons. After manufacturing, the densest parts with distinct parameter sets are categorized into three groups: 1) high power with high scan speed and vacuum slow cooling, 2) low power with low scan speed and vacuum slow cooling, and 3) low power with low scan speed and medium cooling rate in helium gas. Among these, a faster cooling rate suppresses phase transformation temperatures, while vacuum cooling combinations do not affect the phase transformation temperatures significantly. Herein, all the printed parts exhibit almost 8% pseudoelasticity regardless of the process parameters, while the parts cooled in helium have a higher energy dissipation efficiency (1 − η), which implies faster damping of oscillations.     

Dual Molecules Cooperatively Confined In-Between Edge-oxygen-rich Graphene Sheets as Ultrahigh Rate and Stable Electrodes for Supercapacitors

Noncovalent modification of carbon materials with redox-active organic molecules has been considered as an effective strategy to improve the electrochemical performance of supercapacitors. However, their low loading mass, slow electron transfer rate, and easy dissolution into the electrolyte greatly limit further practical applications. Herein, this work reports dual molecules (1,5-dihydroxyanthraquinone (DHAQ) and 2,6-diamino anthraquinone (DAQ)) cooperatively confined in-between edge-oxygen-rich graphene sheets as high-performance electrodes for supercapacitors. Cooperative electrostatic-interaction on the edge-oxygen sites and π–π interaction in-between graphene sheets lead to the increased loading mass and structural stability of dual molecules. Moreover, the electron tunneling paths constructed between edge-oxygen groups and dual molecules can effectively boost the electron transfer rate and redox reaction kinetics, especially at ultrahigh current densities. As a result, the as-obtained electrode exhibits a high capacitance of 507 F g⁻¹ at 0.5 A g⁻¹, and an unprecedented rate capability (203 F g⁻¹ at 200 A g⁻¹). Moreover, the assembled symmetrical supercapacitor achieves a high energy density of 17.1 Wh kg⁻¹ and an ultrahigh power density of 140 kW kg⁻¹, as well as remarkable stability with a retention of 86% after 50 000 cycles. This work may open a new avenue for the efficient utilization of organic materials in energy storage and conversion.