Nacre-Inspired,Liquid Metal-Based Ultrasensitive Electronic Skin by Spatially Regulated Cracking Strategy

The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering.     

Enhanced transduction coefficient in piezoelectric PZT ceramics by mixing powders calcined at different temperatures

Large transduction coefficient ($d_{33}\times g_{33}$) is difficult to obtain in piezoelectric ceramics because these two parameters show opposite trends with compositional modifications. Herein, the Pb(Zr_0.53Ti_0.47)O₃ ceramic powders were calcinated under different temperatures (A:830 °C, B:860 °C, and C:890 °C), and then mixed together according to different weight ratios (1A:1B:1C, 1A:2B:1C, 1A:2B:3C and 3A:2B:1C) for ceramics preparation. Both d₃₃ and g₃₃ are improved successfully, and the transduction coefficient with the weight ratio of 1A:2B:3C reaches up to 17,500 × 10⁻¹⁵ m²/N, which is 60 % higher than that with the powders calcinated under 830 °C, and at least twice those of commercial PZT-4, PZT-5A and PZT-8 ceramics. The improved transduction coefficient is owing to the enhanced piezoelectric constant and spontaneous polarization resulted from the increased grain size, relative density and the fraction of tetragonal phase. These results indicate that this is a simple but effective way to tailor the transduction coefficient in piezoelectric ceramics.     

Three-phase induction motor operating from single-phase supply with an electronically controlled capacitor

In this paper the performance of a three-phase induction motor operating from single-phase supply with a new electronically controlled capacitor using an electronic switch in series with a fixed capacitor to achieve a minimum unbalance of the motor phase voltages at all loading conditions is proposed. No mechanical or centrifugal switch is used here. Basic system operation, theoretical analysis, simulated and experimental results in comparison with conventional operation using one and two fixed capacitors are presented in this paper. The optimum effective capacitor value can be on-line adjusted at any operating speed by periodically changing the duty cycle of the controlled switch to achieve minimum unbalance in phase voltages to improve the motor performance at different speeds.     

Co^3＋—modified Surface of LiMn2O4 Spinel for its Improvementof Electrochemical Properties

Cobalt was used to modify the surface of spinel LiMn2O4 by a solution technique to produce Co^3 -modified surface material (COMSM). Cobalt was only doped into the surface of LiMn2O4 spinel. XPS(X-ray photoelectron spectroscopy) analysis confirms the valence state of Co^3 . COMSM has stable spinel structure and can prevent active materials from the corrosion of electrolyte. The ICP(inductively coupled plasma) determination of the spinel dissolution in electrolyte showed the content of Mn dissolved from COMSM was smaller than that from the pure spinel. AC impedance patterns show that the charge-transfer resistance (Rct) for COMSM is smaller than that for pure spinel. The particles of COMSM are bigger in size than those of pure spinel according to the micrographs of SEM(scanning electron microscopy). The determinations of the electrochemical characterization show that COMSM has both good cycling performance and high initial capacity of 124.1 mA/h at an average capacity loss of 0.19 mAh/g per cycle.     

超重力对燃烧合成Ti（C，N）-TiB2复合粉体的影响

以Ti和B4C为起始反应物，分别在常规和超重力条件下通过燃烧合成技术制备出Ti（C,N）-TiB2复合粉体，利用XRD和SEM对燃烧产物进行了表征，研究了起始组成和超重力条件对燃烧产物相组成和微观形貌的影响。结果表明，燃烧产物主要由Ti（C，N）和TiB2组成，通过改变起始配方中Ti／B4C的摩尔比，可以调节产物中Ti（C，N）和TiB2的相对含量。超重力条件下，反应物颗粒接触更加充分，碰撞更加频繁，因而晶粒形态发育更加完整，生成规则的多面体。     

Effect of high temperature on the mechanical properties of hierarchical porous cenosphere/geopolymer composite foams

A hierarchical porous cenosphere/geopolymer composite foam (FHCs/KGP) was fabricated by the simultaneous incorporation of O₂ pore from hydrogen peroxide and cenosphere filler addition. Effects of both H₂O₂ content and high-temperature treatment on the microstructure, porosity and strength of porous FHCs/KGP foams were investigated systematically. The obtained FHCs/KGP foams showed typical amorphous structure and desirable porosity from 65 to 82%. The composites could crystallize in situ to FHCs/leucite foams above 1000℃. Compression strength of the FHCs/leucite foams showed a maximum value of 5 ± 0.3 MPa when treated at 1000°C. The improvement of mechanical properties for the composite foams was attributed to crack deflection, fractured microspheres and the good bond between the FHCs and matrix. This study could open opportunities to employ cellular foams as alternatives in structure and filtration applications.     

Electrode–Ceramic Inter-Diffusion of Ba(Ti,Zr)O3-Based Y5V MLCCs with Ni Electrodes

The Ba(Ti,Zr)O₃-based multilayer ceramic capacitors (MLCCs) with Ni electrodes, which meet the Electronic Industry Association Y5V standard (from −30° to 85°C, at a temperature capacitance coefficient between −82% and 22%), have been studied in view of the electrode-ceramic inter-diffusion by several microstructual techniques (scanning electron microscopy/transmission electron microscopy/high-resolution transmission electron microscopy (HRTEM)) with an energy-dispersive X-ray spectrometer (EDS). The EDS analysis shows that the elements' inter-diffusion took place along the metal–dielectric interface and the migration of Ni toward the dielectric layers dominated this process. The incorporation of Ni did not transform the crystal structure but introduced lattice distortions, which were characterized by HRTEM, X-ray diffraction, and EDS. The degree of Ni diffusion in the sample with the thinner dielectric layer was more severe. It was concluded from the results that the Ni diffusion is related to the formation of oxygen vacancies after the annealing process, which should be a noticeable factor in the degradation behavior and reliability of base metal electrode MLCCs. The factors influencing the inter-diffusion are also discussed.     

锂离子电池固态聚合物电解质研究进展

电解质是制备高功率密度和高能量密度、长循环寿命的锂离子电池的重要材料之一,而聚合物电解质是实现全固态锂离子电池的关键技术.总结近几年来为提高聚合物电解质电导率所作研究的新进展,并提出了今后的研究方向.