From Inorganic to Organic Iodine: Stabilization of I+ Enabling High-Energy Lithium-Iodine Battery.

Organic materials have been considered a class of promising cathodes for metal-ion batteries because of their sustainability in preparation and source. However, organic batteries with high energy density and application potential require high discharge voltage, multielectron transfer, and long cycling performance. Here, we report an exceptional lithium-iodine (Li//I2) battery, in which the organic iodine (BPD-HI) cathode formed by the Lewis acid-base coordination between hydroiodic acid (HI) and 4,4'-bipyridine (BPD) allows 2e- transfer via the I-/I0 and I0/I+ redox couples. The I+ stabilized by BPD exhibits a high discharge voltage plateau at ∼3.4 V. Remarkably, from inorganic to organic iodine, it realizes a 2-fold increase in the achieved capacity, up to ∼400 mA h gI-1 (Theor. 422 mA h gI-1 and 245.6 mA h g-1 based on the mass of BPD-HI), and an over 2-fold energy density, reaching 1160 W h kgI-1 (Theor. 1324 W h kgI-1). More importantly, a capacity retention rate of 85% over 850 cycles is attained for the Li//BPD-HI battery at a current density of 2 A gI-1. This facile strategy enables positively charged I+ to be electrochemically active in a rechargeable lithium battery. The new redox chemistry discovered provides new insights for developing organic batteries with high energy density.

Functional materials for aqueous redox flow batteries: merits and applications.

Redox flow batteries (RFBs) are promising electrochemical energy storage systems, offering vast potential for large-scale applications. Their unique configuration allows energy and power to be decoupled, making them highly scalable and flexible in design. Aqueous RFBs stand out as the most promising technologies, primarily due to their inexpensive supporting electrolytes and high safety. For aqueous RFBs, there has been a skyrocketing increase in studies focusing on the development of advanced functional materials that offer exceptional merits. They include redox-active materials with high solubility and stability, electrodes with excellent mechanical and chemical stability, and membranes with high ion selectivity and conductivity. This review summarizes the types of aqueous RFBs currently studied, providing an outline of the merits needed for functional materials from a practical perspective. We discuss design principles for redox-active candidates that can exhibit excellent performance, ranging from inorganic to organic active materials, and summarize the development of and need for electrode and membrane materials. Additionally, we analyze the mechanisms that cause battery performance decay from intrinsic features to external influences. We also describe current research priorities and development trends, concluding with a summary of future development directions for functional materials with valuable insights for practical applications.

Porosity effect on the mechanical properties of nano-silver solder.

Nano-silver has the characteristics of low-temperature sintering and high-temperature service, which can reduce the thermal stress in the packaging process. Because of the high melting point and good high-temperature mechanical properties, silver is widely used in high-temperature packaging and connection fields. Sintered nano-silver has a porous structure on the microscopic level, it is necessary to study the mechanical properties of nano-silver with porosity. In this paper, we proposed a method for finite element modeling of porous nano-silver. Finite element analysis and nanoindentation test were used to investigate the Young's modulus of nano-silver. At the same time, and the quadratic equation of porosity and Young's modulus was fitted, and it was verified by Ramakrishnan model and nanoindentation results. These results show that the Young's modulus of nano-silver decreases with the increase of internal porosity, and the Young's modulus and porosity show a quadratic function correlation. As the porosity increases, the Young's modulus of nano-silver decreases at a slower rate. The modeling method presented in this paper can well predict the Young's modulus of nano-silver.

Activation of Bulk Li2 S as Cathode Material for Lithium-Sulfur Batteries through Organochalcogenide-Based Redox Mediation Chemistry.

Lithium sulfide (Li2 S) is considered as a promising cathode material for sulfur-based batteries. However, its activation remains to be one of the key challenges against its commercialization. The extraction of Li+ from bulk Li2 S has a high activation energy (Ea ) barrier, which is fundamentally responsible for the initial large overpotential. Herein, a systematic investigation of accelerated bulk Li2 S oxidation reaction kinetics was studied by using organochalcogenide-based redox mediators, in which phenyl ditelluride (PDTe) can significantly reduce the Ea of Li2 S and lower the initial charge potential. Simultaneously, it can alleviate the polysulfides shuttling effect by covalently anchoring the soluble polysulfides and converting them into insoluble lithium phenyl tellusulfides (PhTe-Sx Li, x>1). This alters the redox pathway and accelerates the reaction kinetics of Li2 S cathode. Consequently, the Li||Li2 S-PDTe cell shows excellent rate capability and enhanced cycling stability. The Si||Li2 S-PDTe full cell delivers a considerable capacity of 953.5 mAh g-1 at 0.2 C.

Ferroelectric Metal-Organic Framework as a Host Material for Sulfur to Alleviate the Shuttle Effect of Lithium-Sulfur Battery.

Ferroelectricity has an excellent reversible polarization conversion behavior under an external electric field. Herein, we propose an interesting strategy to alleviate the shuttle effect of lithium-sulfur battery by utilizing ferroelectric metal-organic framework (FMOF) as a host material for the first time. Compared to other MOF with same structure but without ferroelectricity and commercial carbon black, the cathode based on FMOF exhibits a low capacity decay and high cycling stability. These results demonstrate that the polarization switching behaviors of FMOF under the discharge voltage of lithium-sulfur battery can effectively trap polysulfides by polar-polar interactions, decrease polysulfides shuttle and improve the electrochemical performance of lithium-sulfur battery.

Correction of thermal airflow distortion in warpage measurements of microelectronic packaging structures via deep learning-based digital image correlation.

The projected speckle-based three-dimensional digital image correlation method (3D-DIC) is being increasingly used in the reliability measurement of microelectronic packaging structures because of its noninvasive nature, high precision, and low cost. However, during the measurement of the thermal reliability of packaging structures, the thermal airflow generated by heating introduces distortions in the images captured by the DIC measurement system, impacting the accuracy and reliability of noncontact measurements. To address this challenge, a thermal airflow distortion correction model based on the transformer attention mechanism is proposed specifically for the measurement of thermal warpage in microelectronic packaging structures. This model avoids the oversmoothing issue associated with convolutional neural networks and the lack of physical constraints in generative adversarial networks, ensuring the precision of grayscale gradient changes in speckle patterns and minimizing adverse effects on DIC calculation accuracy. By inputting the distorted images captured by the DIC measurement system into the network, corrected images are obtained for 3D-DIC calculations, thus allowing the thermal warpage measurement results of the sample to be acquired. Through experiments measuring topography with customized step block specimens, the effectiveness of the proposed method in improving warpage measurement accuracy is confirmed; this is particularly true when captured images are affected by thermal airflow at 140 °C and 160 °C, temperatures commonly encountered in thermal reliability testing of packaging structures. The method successfully reduces the standard deviation from 9.829 to 5.943 µm and from 12.318 to 6.418 µm, respectively. The results demonstrate the substantial practical value of this method for measuring thermal warpage in microelectronic packaging structures.

Molecular Engineering of Organic Species for Aqueous Redox Flow Batteries.

Redox flow batteries (RFBs) are promising candidates for large-scale energy storage systems (ESSs) due to their unique architecture that can decouple energy and power. Aqueous RFBs based on organic molecules (AORFBs) work with a non-flammable and intrinsically safe aqueous electrolyte, and organic compounds are performed as redox couples. The application of redox-active organics tremendously expands the development space of RFBs owing to the highly tunable molecule structure. Molecular engineering enables the exceptional merits in solubility, stability, and redox potential of different organic molecules. Herein, this review summarizes the application of molecular engineering to several organic compounds, focusing on the fundamental overview of their physicochemical properties and design strategies. We discuss the electrochemical merits and performances along with the intrinsic properties of the designed organic components. Finally, we outline the requirements for rational design of innovative organics to motivate more valuable research and present the prospect of molecule engineering used in AORFBs.

Design and Optimization of a Novel MEMS Tuning Fork Gyroscope Microstructure.

This paper presents the design and optimization of a novel MEMS tuning fork gyroscope microstructure. In order to improve the mechanical sensitivity of the gyroscope, much research has been carried out in areas such as mode matching, improving the quality factor, etc. This paper focuses on the analysis of mode shape, and effectively optimizes the decoupling structure and size of the gyroscope. In terms of structural design, the vibration performance of the proposed structure was compared with other typical structures. It was found that slotting in the middle of the base improved the transmission efficiency of Coriolis vibration, and opening arc slots between the tines reduced the working modal order and frequency. In terms of size optimization, the Taguchi method was used to optimize the relevant feature sizes of the gyroscope. Compared with the initial structure, the transmission efficiency of Coriolis vibration of the optimized gyroscope was improved by about 18%, and the working modal frequency was reduced by about 2.7 kHz. Improvement of these two indicators will further improve the mechanical sensitivity of the gyroscope.

Effect of Oxygen-Containing Group on the Catalytic Performance of Zn/C Catalyst for Acetylene Acetoxylation.

In this study, a series of activated carbon-based supports with different oxygen-containing groups (OCGs) proportions were obtained via thermal treatment in an ozone flow. Semiquantitative analyses indicated that the performance of the catalyst attained a maximum after 30 min of treatment with ozone flow, and had a positive correlation with the content ratios of carboxyl and hydroxyl groups. Further, temperature-programmed desorption analysis demonstrated that the high performance (63% acetic acid conversion) of the prepared catalyst for the acetoxylation of acetylene could be ascribed to the reduced strength of increased capacity of acetylene adsorption. Density functional theory proved that the additional -COOH in the dicarboxylic catalytic system could be employed as a support for the active sites, and enhancing C2H2 adsorption strength in the rate-limiting step in the actual experimental process effectively accelerated the reaction rate. Thus, the OCGs on the surface of activated carbon play a crucial role in the catalytic performance of the acetylene acetoxylation catalyst.

Effect of inclusion on 4H-SiC during nano-scratching from an atomistic perspective.

Inclusion, a common three-dimension defect, can be introduced during SiC epitaxy. In this study, we constructed nano-scratching molecular dynamics models embedded in two common types of inclusion-C-inclusion and Si-inclusion-to explore the effect of inclusion during scratching. Furthermore, the microstructure and atomistic behavior, surface morphology, scratching force, stress, and temperature were analyzed to bridge the simulation and processing parameters. The results showed that inclusion could affect the microstructure and atomistic behavior, and machinability. To eliminate inclusion completely, high penetration depth was required, but it would promote the process parameter sensitivity of inclusion. In summary, the behavior of C-inclusion embedded in SiC more likes a hard particle, while the behavior of Si-inclusion embedded in SiC more likes a soft particle.

Investigation of the Turbulent Drag Reduction Mechanism of a Kind of Microstructure on Riblet Surface.

With the k-ε renormalization group turbulence model, the drag reduction mechanism of three- dimensional spherical crown microstructure of different protruding heights distributing on the groove surface was studied in this paper. These spherical crown microstructures were divided into two categories according to the positive and negative of protruding height. The positive spherical crown micro-structures can destroy a large number of vortexes on the groove surface, which increases relative friction between water flow and the groove surface. With decreasing the vertical height of the spherical crown microstructure, the number of rupture vortexes gradually decreases. Due to the still water area causes by the blocking effect of the spherical crown microstructure, it was found that the shear stress on the groove surface can be reduced, which can form the entire drag reduction state. In another case, the spherical crown microstructures protrude in the negative direction, vortexes can be generated inside the spherical crown, it was found that these vortexes can effectively reduce the resistance in terms of pressure and friction. In a small volume, it was shown that the surface drag reduction rate of spherical crown microstructures protrudes in negative directions can be the same as high as 24.8%.

A powder-metallurgy-based strategy toward three-dimensional graphene-like network for reinforcing copper matrix composites.

Three-dimensional graphene network is a promising structure for improving both the mechanical properties and functional capabilities of reinforced polymer and ceramic matrix composites. However, direct application in a metal matrix remains difficult due to the reason that wetting is usually unfavorable in the carbon/metal system. Here we report a powder-metallurgy based strategy to construct a three-dimensional continuous graphene network architecture in a copper matrix through thermal-stress-induced welding between graphene-like nanosheets grown on the surface of copper powders. The interpenetrating structural feature of the as-obtained composites not only promotes the interfacial shear stress to a high level and thus results in significantly enhanced load transfer strengthening and crack-bridging toughening simultaneously, but also constructs additional three-dimensional hyperchannels for electrical and thermal conductivity. Our approach offers a general way for manufacturing metal matrix composites with high overall performance.

Ultrafast Absorption of Polysulfides through Electrostatic Confinement by Protonated Molecules for Highly Efficient Li-S Batteries.

The lithium-sulfur battery is a promising high-energy-density storage system, which suffers from severe capacity fading due to the "shuttle effect" and low Coulombic efficiency caused by the dissolution of lithium polysulfides. At the molecular level, suppressing the shuttle effect has been greatly required for high-performance Li-S batteries. Herein, we propose a new strategy by utilizing a protonated organic absorbent (N1,N4-bis(pyridine-3-ylmethyl)butane-1,4-diammonium nitrate ([H2PBD]2+·(NO3)22-) for ultrafast absorption of polysulfides through electrostatic attractions and for fixing the polysulfides in the cathode by hydrogen-bond interactions. A lithium-sulfur battery cathode based on a commercial carbon black (CB) and an absorbent (10%) with high sulfur content (70%) exhibits a low capacity decay of 0.099% per cycle over 400 cycles at a rate of 0.5C along with 91% Coulombic efficiency. This strategy and the finding of an electrostatic absorbent offer a new alternative insight into designing cheaper lithium-sulfur batteries for their practical application in the future.

High-Performance Metal-Organic Framework-Based Single Ion Conducting Solid-State Electrolytes for Low-Temperature Lithium Metal Batteries.

Single-ionic conducting electrolytes are important for the improvement of lithium metal batteries with high energy density and safety. Herein, we propose a new strategy to anchor a large anionic group on the skeleton of metal-organic frameworks (MOFs) and achieve preeminent single-ionic conducting electrolytes. Utilizing a postsynthetic modification method, the trifluoromethanesulfonyl group is covalently coordinated to the amino groups of the UiO-66-NH2 framework. Such a single-ionic conducting solid-state electrolyte (SSE) has a high ionic conductivity (2.07 × 10-4 S cm-1 at 25 °C), a low activation energy of 0.31 eV, a wide electrochemical window up to 4.52 V, as well as a high Li+ transference number of 0.84. Simultaneously, it can effectively inhibit the formation of lithium dendrite. Solid-state batteries assembled with LiFePO4 as the cathode exhibit outstanding rate performance and cyclic stability, especially for low-temperature Li-metal batteries at 0 °C with trace amounts of propylene carbonate as wetting agents. More importantly, the corresponding all-solid-state batteries based on an MOF-based SSE also have nearly 100% Coulombic efficiency at different current densities.

Syntheses and magnetic properties of high-dimensional cucurbit[6]uril-based metal-organic rotaxane frameworks.

Three new high-dimensional cucurbit[6]-based metal-organic rotaxane frameworks [Co2(PR43)(BDC)2Cl2]·4H2O (1), [Co2(PR43)(BTC)2]·6H2O (2) and [Co2(PR43)(BPT)2]·20H2O (3) were obtained via the hydrothermal synthesis method. Compound 1 comprised a two-dimensional layered structure, while compounds 2 and 3 exhibited three-dimensional pillared structures. All the compounds showed good thermal stabilities. Furthermore, the magnetic properties of compounds 1-3 were also investigated in detail.

Investigation of Mechanical Properties of Silicone/Phosphor Composite Used in Light Emitting Diodes Package.

Mass fraction of phosphor in silicone and aging time play important roles in the optics and mechanical performance of the silicone that is used in the light emitting diode (LED) package. In this paper, the mechanical properties of silicone/phosphor composites are investigated experimentally by separate tensile and compression tests. Distribution of the phosphors is observed by scanning electron microscopy (SEM) to ensure the homogeneity of the samples. Different loading rates are applied to study the silicone material's rate-dependent properties. The experimental results of the tensile and compression test show that the Young's modulus increases with the mass fraction of phosphor in silicone. Longer aging time stiffens the silicone composite and weakens the ductility of the materials. A three-dimensional model used cohesive zone material (CZM) between the interface of the phosphor particles, and matrix silicone is built up to study the degradation mechanism at a micro-scale level. The simulation results indicate that the diameter of particles in silicone also impacts its interface debonding and crack growth. The theoretical results concerning the mass fraction of phosphor are in good agreement with the experiments.

Guest exchange in a porous cucurbit[6]uril-based metal-organic rotaxane framework probed by NMR and X-ray crystallography.

The first CB[6]-based 3D porous metal-organic rotaxane framework is constructed by the reaction of CuCl2, terephthalic (H2BDC) and CB[6]-based [2]pseudorotaxanes ([PR44]2+·2[PF6]-) under solvothermal conditions. The structure of MORF-1 is a pillared-layer structure with 5-connected sqp topology, in which the effective free volume is 45.4% of the crystal volume. The guest molecules exchange in a single-crystal-to-single-crystal fashion, which was investigated using NMR spectroscopy and X-ray crystallography.

Ultrasonic power measurement system based on acousto-optic interaction.

Ultrasonic waves are widely used, with applications including the medical, military, and chemical fields. However, there are currently no effective methods for ultrasonic power measurement. Previously, ultrasonic power measurement has been reliant on mechanical methods such as hydrophones and radiation force balances. This paper deals with ultrasonic power measurement based on an unconventional method: acousto-optic interaction. Compared with mechanical methods, the optical method has a greater ability to resist interference and also has reduced environmental requirements. Therefore, this paper begins with an experimental determination of the acoustic power in water contained in a glass tank using a set of optical devices. Because the light intensity of the diffraction image generated by acousto-optic interaction contains the required ultrasonic power information, specific software was written to extract the light intensity information from the image through a combination of filtering, binarization, contour extraction, and other image processing operations. The power value can then be obtained rapidly by processing the diffraction image using a computer. The results of this work show that the optical method offers advantages that include accuracy, speed, and a noncontact measurement method.