Rapid non-destructive monitoring and quality assessment of the fumigation process of Shanxi aged vinegar based on Vis-NIR hyperspectral imaging combined with multiple chemometric algorithms.

The quality of the grains during the fumigation process can significantly affect the flavour and nutritional value of Shanxi aged vinegar (SAV). Hyperspectral imaging (HSI) was used to monitor the extent of fumigated grains, and it was combined with chemometrics to quantitatively predict three key physicochemical constituents: moisture content (MC), total acid (TA) and amino acid nitrogen (AAN). The noise reduction effects of five spectral preprocessing methods were compared, followed by the screening of optimal wavelengths using competitive adaptive reweighted sampling. Support vector machine classification was employed to establish a model for discriminating fumigated grains, and the best recognition accuracy reached 100%. Furthermore, the results of partial least squares regression slightly outperformed support vector machine regression, with correlation coefficient for prediction (Rp) of 0.9697, 0.9716, and 0.9098 for MC, TA, and AAN, respectively. The study demonstrates that HSI can be employed for rapid non-destructive monitoring and quality assessment of the fumigation process in SAV.

Soft and Damping Thermal Interface Materials with Honeycomb-Board-Mimetic Filler Network for Electronic Heat Dissipation.

High-power-density electronic devices under vibrations call for soft and damping thermal interface materials (TIMs) for efficient heat dissipation. However, integrating low hardness, high damping, and superior heat transfer capability into one TIM is highly challenging. Herein, soft, damping, and thermally conductive TIMs are designed and prepared by constructing a honeycomb-board-mimetic boron nitride nanosheet (BNNS) network in a dynamic polyimine via one-step horizontal centrifugal casting. The unique filler network makes the TIMs perform a high through-plane thermal conductivity (> 7.69 W m-1 K-1) and a uniform heat transfer process. Meanwhile, the hierarchical dynamic bonding of the polyimine endows the TIMs with low compressive strength (2.16 MPa at 20% strain) and excellent damping performance (tan δ > ≈0.3 at 10-2-102 Hz). The resulting TIMs also exhibit electrical insulation and remarkable recycling ability. Compared with the commercial ones, the TIMs provide better heat dissipation (4.1 °C) for a high-power 5G base station and less temperature fluctuation (1.8 °C) for an automotive insulated gate bipolar transistor (IGBT) under vibrations. This rational design offers a viable approach to prepare soft and damping TIMs for effective heat dissipation of high-power-density electronic devices under vibrations.

On-Demand Preparation of Boron Nitride Nanosheets for Functional Nanocomposites.

Boron nitride nanosheets (BNNSs) have garnered significant attention across diverse fields; however, accomplishing on-demand, large-scale, and highly efficient preparation of BNNSs remains a challenge. Here, an on-demand preparation (OdP) method combining high-pressure homogenization and short-time ultrasonication is presented; it enables a highly efficient and controllable preparation of BNNSs from bulk hexagonal boron nitride (h-BN). The homogenization pressure and number of cycles are adjusted, and the production efficiency and yield of BNNSs reach 0.95 g g-1 h-1 and 82.8%, respectively, which significantly exceed those attained by using existing methods. The universality of the OdP method is demonstrated on h-BN raw materials of various bulk sizes from various producers. Furthermore, this method allows the preparation of BNNSs having specific sizes based on the final requirements. Both simulation and experimental results indicate that large BNNSs are particularly suitable for enhancing the thermal conductivity and electrical insulation properties of dielectric polymer nanocomposites. Interestingly, the small BNNS-filled photonic nanocomposite films fabricated via the OdP method exhibit superior daytime radiative cooling properties. Additionally, the OdP method offers the benefits of low energy consumption and reduced greenhouse gas emissions and fossil energy use. These findings underscore the unique advantages of the OdP method over other techniques for a high-efficiency and controllable preparation of large BNNSs.

Engineering a Dynamic Solvent-Phobic Liquid Electrolyte Interphase for Long-Life Lithium Metal Batteries.

The heterogeneity, species diversity, and poor mechanical stability of solid electrolyte interphases (SEIs) in conventional carbonate electrolytes result in the irreversible exhaustion of lithium (Li) and electrolytes during cycling, hindering the practical applications of Li metal batteries (LMBs). Herein, this work proposes a solvent-phobic dynamic liquid electrolyte interphase (DLEI) on a Li metal (Li-PFbTHF (perfluoro-butyltetrahydrofuran)) surface that selectively transports salt and induces salt-derived SEI formation. The solvent-phobic DLEI with C-F-rich groups dramatically reduces the side reactions between Li, carbonate solvents, and humid air, forming a LiF/Li3PO4-rich SEI. In situ electrochemical impedance spectroscopy and Ab-initio molecular dynamics demonstrate that DLEI effectively stabilizes the interface between Li metal and the carbonate electrolyte. Specifically, the LiFePO4||Li-PFbTHF cells deliver 80.4% capacity retention after 1000 cycles at 1.0 C, excellent rate capacity (108.2 mAh g-1 at 5.0 C), and 90.2% capacity retention after 550 cycles at 1.0 C in full-cells (negative/positive (N/P) ratio of 8) with high LiFePO4 loadings (15.6 mg cm-2) in carbonate electrolyte. In addition, the 0.55 Ah pouch cell of 252.0 Wh kg-1 delivers stable cycling. Hence, this study provides an effective strategy for controlling salt-derived SEI to improve the cycling performances of carbonate-based LMBs.

Application-Driven High-Thermal-Conductivity Polymer Nanocomposites.

Polymer nanocomposites combine the merits of polymer matrices and the unusual effects of nanoscale reinforcements and have been recognized as important members of the material family. Being a fundamental material property, thermal conductivity directly affects the molding and processing of materials as well as the design and performance of devices and systems. Polymer nanocomposites have been used in numerous industrial fields; thus, high demands are placed on the thermal conductivity feature of polymer nanocomposites. In this Perspective, we first provide roadmaps for the development of polymer nanocomposites with isotropic, in-plane, and through-plane high thermal conductivities, demonstrating the great effect of nanoscale reinforcements on thermal conductivity enhancement of polymer nanocomposites. Then the significance of the thermal conductivity of polymer nanocomposites in different application fields, including wearable electronics, thermal interface materials, battery thermal management, dielectric capacitors, electrical equipment, solar thermal energy storage, biomedical applications, carbon dioxide capture, and radiative cooling, are highlighted. In future research, we should continue to focus on methods that can further improve the thermal conductivity of polymer nanocomposites. On the other hand, we should pay more attention to the synergistic improvement of the thermal conductivity and other properties of polymer nanocomposites. Emerging polymer nanocomposites with high thermal conductivity should be based on application-oriented research.

Solar-powered clothes, for the heat and cold.

A wearable device allows the human body to adapt to changes in ambient temperature.

Engineering the Dielectric Constants of Polymers: From Molecular to Mesoscopic Scales.

Polymers are essential components of modern-day materials and are widely used in various fields. The dielectric constant, a key physical parameter, plays a fundamental role in the light-, electricity-, and magnetism-related applications of polymers, such as dielectric and electrical insulation, battery and photovoltaic fabrication, sensing and electrical contact, and signal transmission and communication. Over the past few decades, numerous efforts have been devoted to engineering the intrinsic dielectric constant of polymers, particularly by tailoring the induced and orientational polarization modes and ferroelectric domain engineering. Investigations into these methods have guided the rational design and on-demand preparation of polymers with desired dielectric constants. This review article exhaustively summarizes the dielectric constant engineering of polymers from molecular to mesoscopic scales, with emphasis on application-driven design and on-demand polymer synthesis rooted in polymer chemistry principles. Additionally, it explores the key polymer applications that can benefit from dielectric constant regulation and outlines the future prospects of this field.

Aromatic-Free Polymers Based All-Organic Dielectrics with Breakdown Self-Healing for High-Temperature Capacitive Energy Storage.

High-temperature dielectric polymers are becoming increasingly desirable for capacitive energy storage in renewable energy utilization, electrified transportation, and pulse power systems. Current dielectric polymers typically require robust aromatic molecular frameworks to ensure structural thermal stability at elevated temperatures. Nevertheless, the introduction of aromatic units compromises electrical insulation owing to pronounced π─π interactions that facilitate electron transport and eliminate the breakdown self-healing property owing to their high carbon content. Herein, an aromatic-free polynorborne copolymer exhibiting electrical conductivity-two orders of magnitude lower than that of state-of-the-art polyetherimide-at elevated temperatures and high electric fields owing to its large bandgap (≈4.64 eV) and short hopping conduction distance (≈0.63 nm) is described. Density functional theory calculations demonstrate that the copolymer can effectively suppress the excitation of high-field valence electrons. Furthermore, the incorporation of trace semiconductors results in high discharge density (3.73 J cm-3 ) and charge-discharge efficiency (95% at 150 °C), outperforming existing high-temperature dielectric polymers. The excellent electrical breakdown self-healing capability of the copolymer film at elevated temperatures further demonstrates its potential for use in dielectric capacitors capable of continuous operation under extreme conditions.

Application of Hyperspectral Imaging as a Nondestructive Technology for Identifying Tomato Maturity and Quantitatively Predicting Lycopene Content.

Maturity is a crucial indicator in assessing the quality of tomatoes, and it is closely related to lycopene content. Using hyperspectral imaging, this study aimed to monitor tomato maturity and predict its lycopene content at different maturity stages. Standard normal variable (SNV) transformation was applied to preprocess the hyperspectral data. Then, using competitive adaptive reweighted sampling (CARS), the characteristic wavelengths were selected to simplify the calibration models. Based on the full and characteristic wavelengths, a support vector classifier (SVC) model was developed to determine tomato maturity qualitatively. The results demonstrated that the classification accuracy using the characteristic wavelength led to the obtention of better results with an accuracy of 95.83%. In addition, the support vector regression (SVR) and partial least squares regression (PLSR) models were utilized to predict lycopene content. With a coefficient of determination for prediction (R2P) of 0.9652 and a root mean square error for prediction (RMSEP) of 0.0166 mg/kg, the SVR model exhibited the best quantitative prediction capacity based on the characteristic wavelengths. Following this, a visual distribution map was created to evaluate the lycopene content in tomato fruit intuitively. The results demonstrated the viability of hyperspectral imaging for detecting tomato maturity and quantitatively predicting the lycopene content during storage.

Engineering the Structural Uniformity of Gel Polymer Electrolytes via Pattern-Guided Alignment for Durable, Safe Solid-State Lithium Metal Batteries.

Ultrathin and super-toughness gel polymer electrolytes (GPEs) are the key enabling technology for durable, safe, and high-energy density solid-state lithium metal batteries (SSLMBs) but extremely challenging. However, GPEs with limited uniformity and continuity exhibit an uneven Li+ flux distribution, leading to nonuniform deposition. Herein, a fiber patterning strategy for developing and engineering ultrathin (16 µm) fibrous GPEs with high ionic conductivity (≈0.4 mS cm-1 ) and superior mechanical toughness (≈613%) for durable and safe SSLMBs is proposed. The special patterned structure provides fast Li+ transport channels and tailoring solvation structure of traditional LiPF6 -based carbonate electrolyte, enabling rapid ionic transfer kinetics and uniform Li+ flux, and boosting stability against Li anodes, thus realizing ultralong Li plating/stripping in the symmetrical cell over 3000 h at 1.0 mA cm-2 , 1.0 mAh cm-2 . Moreover, the SSLMBs with high LiFePO4 loading of 10.58 mg cm-2 deliver ultralong stable cycling life over 1570 cycles at 1.0 C with 92.5% capacity retention and excellent rate capacity of 129.8 mAh g-1 at 5.0 C with a cut-off voltage of 4.2 V (100% depth-of-discharge). Patterned GPEs systems are powerful strategies for producing durable and safe SSLMBs.

Ladderphane copolymers for high-temperature capacitive energy storage.

For capacitive energy storage at elevated temperatures1-4, dielectric polymers are required to integrate low electrical conduction with high thermal conductivity. The coexistence of these seemingly contradictory properties remains a persistent challenge for existing polymers. We describe here a class of ladderphane copolymers exhibiting more than one order of magnitude lower electrical conductivity than the existing polymers at high electric fields and elevated temperatures. Consequently, the ladderphane copolymer possesses a discharged energy density of 5.34 J cm-3 with a charge-discharge efficiency of 90% at 200 °C, outperforming the existing dielectric polymers and composites. The ladderphane copolymers self-assemble into highly ordered arrays by π-π stacking interactions5,6, thus giving rise to an intrinsic through-plane thermal conductivity of 1.96 ± 0.06 W m-1 K-1. The high thermal conductivity of the copolymer film permits efficient Joule heat dissipation and, accordingly, excellent cyclic stability at elevated temperatures and high electric fields. The demonstration of the breakdown self-healing ability of the copolymer further suggests the promise of the ladderphane structures for high-energy-density polymer capacitors operating under extreme conditions.

Modulus-Modulated All-Organic Core-Shell Nanofiber with Remarkable Piezoelectricity for Energy Harvesting and Condition Monitoring.

The low piezoelectricity of piezoelectric polymers significantly restricts their applications. Introducing inorganic fillers can slightly improve the piezoelectricity of polymers, whereas it is usually at the cost of flexibility and durability. In this work, using a modulus-modulated core-shell structure strategy, all-organic nanofibers with remarkable piezoelectricity were designed and prepared by a coaxial electrospinning method. It was surprisingly found that the introduction of a nonpiezoelectric polymeric core (e.g., polycarbonate, PC) can result in 110% piezoelectric coefficient (d33) enhancement in a poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) nanofiber. Accordingly, the all-organic PVDF-TrFE@PC core-shell nanofiber exhibits record-high energy-harvesting performance (i.e., 126 V output voltage, 710 mW m-2 power density) among the reported organic piezoelectric materials. In addition, the excellent sensing capability of the core-shell nanofiber enabled us to develop a wireless vibration monitoring and analyzing system, which realizes the real-time vibration detection of a power transformer.

Flexible, Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators.

Thermal management has become a crucial problem for high-power-density equipment and devices. Phase change materials (PCMs) have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition. However, low intrinsic thermal conductivity, ease of leakage, and lack of flexibility severely limit their applications. Solving one of these problems often comes at the expense of other performance of the PCMs. In this work, we report core-sheath structured phase change nanocomposites (PCNs) with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning, electrostatic spraying, and hot-pressing. The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m-1 K-1 at a low BNNS loading (i.e., 32 wt%), which thereby endows the PCNs with high enthalpy (> 101 J g-1), outstanding ductility (> 40%) and improved fire retardancy. Therefore, our core-sheath strategies successfully balance the trade-off between thermal conductivity, flexibility, and phase change enthalpy of PCMs. Further, the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators, displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.

Pillar[5]arene Derivatives Embedded with Aggregation-Induced Emission Luminogens and Their Fluorescence Regulation.

Through McMurry coupling reaction, three meso-position functionalized pillar[5]arene derivatives (H-1, H-2, and H-3) have been successfully prepared by embedding aggregation-induced emission luminogens (AIEgens, diphenyldibenzofulvene (DPDBF) and tetraphenylethylene (TPE)) into the skeleton of supramolecular macrocycles. H-1, bearing [15 ]paracyclophane ([15 ]PCP) and DPDBF moiety, exhibits yellow emission and demonstrates obvious AIE effect. In order to further improve the host-guest properties of this type of structure, H-2 and H-3 are prepared by replacing the [15 ]PCP moiety with pillar[5]arene backbone, both of which show significant AIE effect and excellent host-guest complexation properties with pyrazine salt guest G-1 and 1,4-dicyanobutane G-2. Our findings indicate that G-1 can decrease the fluorescence intensity of the AIE macrocycles, while G-2 can increase their fluorescence intensity in solution.

Qualitative and quantitative assessment of flavor quality of Chinese soybean paste using multiple sensor technologies combined with chemometrics and a data fusion strategy.

Multiple sensor technologies including electronic nose (E-nose), electronic tongue (E-tongue), colorimeter and texture analyzer combined with chemometrics and dada fusion strategies were applied to characterize the flavor quality of traditional Chinese fermented soybean paste. Principal components analysis (PCA) was performed to divide the selected soybean pastes into three clusters which was not completely consistent with geographical regions of selected samples. Support vector machine regression (SVR) outperformed partial least squares regression (PLSR) in quantitatively predicting sensory attributes. Additionally, prediction of overall flavor of soybean paste based on data fusion of multiple sensor information, with a correlation coefficient of prediction (Rp) of 0.9636 based on SVR, was better than prediction of E-nose and E-tongue data fusion (Rp = 0.9267). This study suggested multiple sensor technologies coupled with chemometrics can be a promising tool for flavor assessment and characterization of fermented soybean paste or other food matrixes.

AZ31B magnesium alloy matching layer for Lens-focused piezoelectric transducer application.

Compared with planar transducers, focused transducers have higher ultrasound intensity and better lateral resolution in the focal zone. At present, the matching layer materials for focused transducers are mainly 0-3 composite materials, which have problems such as non-uniformity, difficulty to fabricate at high frequencies, and large sound attenuation. In this paper, finite element analysis is carried out to simulate lens-focused transducers with different matching layer structures and materials. It is found that the focused transducer with magnesium alloy matching layer has the best comprehensive performance. A lens-focused PZT-5H ultrasonic transducer was then fabricated with AZ31B magnesium alloy as the first matching layer. The measured results show that the center frequency of the transducer is 4.38 MHz, the -6-dB bandwidth is 68.35 % and the insertion loss is -13.88 dB. Benefiting from the high uniformity, high acoustic impedance and extremely low acoustic attenuation of magnesium alloy, the transducers in this research exhibit superior performances than other reported transducers with conventional matching layer. The current work suggests that AZ31B magnesium alloy is a promising matching layer material for ultrasonic transducers.

Chemical adsorption on 2D dielectric nanosheets for matrix free nanocomposites with ultrahigh electrical energy storage.

Relaxor ferroelectric polymers display great potential in capacitor dielectric applications because of their excellent flexibility, light weight, and high dielectric constant. However, their electrical energy storage capacity is limited by their high conduction losses and low dielectric strength, which primarily originates from the impact-ionization-induced electronmultiplication, low mechanical modulus, and low thermal conductivity of the dielectric polymers. Here a matrix free strategy is developed to effectively suppress electron multiplication effects and to enhance mechanical modulus and thermal conductivity of a dielectric polymer, which involves the chemical adsorption of an electron barrier layer on boron nitride nanosheet surfaces by chemically adsorbing an amino-containing polymer. A dramatic decrease of leakage current (from 2.4 × 10-6 to 1.1 × 10-7 A cm-2 at 100 MV m-1) and a substantial increase of breakdown strength (from 340 to 742 MV m-1) were achieved in the nanocompostes, which result in a remarkable increase of discharge energy density (from 5.2 to 31.8 J cm-3). Moreover, the dielectric strength of the nanocomposites suffering an electrical breakdown could be restored to 88% of the original value. This study demonstrates a rational design for fabricating dielectric polymer nanocomposites with greatly enhanced electric energy storage capacity.

Hierarchically porous composite fabrics with ultrahigh metal-organic framework loading for zero-energy-consumption heat dissipation.

The long-term safe operation of high-power equipment and integrated electronic devices requires efficient thermal management, which in turn increases the energy consumption further. Hence, the sustainable development of our society needs advanced thermal management with low, even zero, energy consumption. Harvesting water from the atmosphere, followed by moisture desorption to dissipate heat, is an efficient and feasible approach for zero-energy-consumption thermal management. However, current methods are limited by the low absorbance of water, low water vapor transmission rate (WVTR) and low stability, thus resulting in low thermal management capability. In this study, we report an innovative electrospinning method to process hierarchically porous metal-organic framework (MOF) composite fabrics with high-efficiency and zero-energy-consumption thermal management. The composite fabrics are highly loaded with MOF (75 wt%) and their WVTR value can be up to 3138 g m-2 d-1. The composite fabrics also exhibit stable microstructure and performance. Under a conventional environment (30 ℃, 60% relative humidity), the composite fabrics adsorb water vapor for regeneration within 1.5 h to a saturated value Wsat of 0.614 g g-1, and a corresponding equivalent enthalpy of 1705.6 J g-1. In the thermal management tests, the composite fabrics show a strong cooling capability and significantly improve the performance of thermoelectric devices, portable storage devices and wireless chargers. These results suggest that hierarchically porous MOF composite fabrics are highly promising for thermal management of intermittent-operation electronic devices.

Authentication of duck blood tofu binary and ternary adulterated with cow and pig blood-based gel using Fourier transform near-infrared coupled with fast chemometrics.

This work aims to investigate a feasible and practical technique for the authentication of edible animal blood food (EABF) using Fourier transform near-infrared (FT-NIR) coupled with fast chemometrics. A total of 540 samples were used, including raw duck blood tofu (DBT), cow blood-based gel (CBG), pig blood-based gel (PBG), and DBT binary and ternary adulterated with CBG and PBG. The protein, fat, total sugar, and 16 kinds of amino acids were measured to validate the difference in basic organic matters among EABFs according to species. Fisher linear discriminate analysis (Fisher LDA) and extreme learning machine (ELM) were implemented comparatively to identify the adulterated EABF. To predict adulteration levels, four extreme learning machine regression (ELMR) models were constructed and optimized. Results showed that, by analyzing 27 crucial spectral variables, the ELM model provides higher accuracy of 93.89% than Fisher LDA for the independent samples. All the correlation coefficients of the optimized ELMR models' training and prediction sets were better than 0.94, the root mean square errors were all less than 3.5%, and the residual prediction deviation and the range error ratios were all higher than 4.0 and 12.0, respectively. In conclusion, the FT-NIR paired with ELM have great potential in authenticating the EABF. This work presents amino acids content in EABFs for the first time and built tracing models for rapid authentication of DBT, which can be used to manage the EABF market, thereby preventing illegal adulteration and unfair competition.