Comparative study of La0.5Nd0.2Ca0.3–xKxMnO3 (x = 0.0 and 0.05) nanoparticles: Effect of A-cation size and calcination temperature

In order to study the effect of sintering temperature and A-site cation radius on the structural, magnetic and transport properties, a systematic investigation of La_0.5Nd_0.2Ca_0.3–xK_xMnO₃ (x = 0.0 and 0.05) nanoparticles has been undertaken. Rietveld analysis of X-ray diffraction data confirmed the presence of orthorhombic symmetry with Pbnm space group for all the samples. A paramagnetic-ferromagnetic transition is shown by all our investigated compounds. The materials exhibit semiconducting behavior and the metal-semiconductor transition temperatures (T_MS) are found to be close to Curie temperatures (T_c), indicating a strong correlation between their electrical and magnetic properties. Both T_c and T_MS of K-doped samples were found to be higher than their undoped counterparts at same calcination temperatures. In the high temperature region, it was observed that the resistivity data was best fitted by SPH model.     

Study on low temperature brazing of magnesium alloy to aluminum alloy using Sn–xZn solders

In this article, a series of Sn–xZn solders are designed for joining Mg/Al dissimilar metals by low temperature brazing. The effect of Zn content in Sn–Zn solders on microstructure evolution and mechanical properties of the different brazed joints are investigated. The experimental results indicate that Sn–30Zn alloy is identified as the optimized solder. Al–Sn–Zn solid solutions form and disperse in the brazing zone of the Mg/Sn–30Zn/Al brazed joint, decreasing the risk of embrittlement of the brazed joint. The average shear strength of Mg/Sn–30Zn/Al brazed joint can reach 70.73 MPa. The joint fractures in the coarse blocky Mg₂Sn intermetallic phases in the center of the brazing zone.     

CuS Electrode for All-pH Electrolyte in Aqueous Batteries

用于水系电池中全pH电解质的CuS电极

杨亮亮^{1, 3}, 崔芒伟^1,3, 刘清江^{1, 3}, 雷浩^{1, 3} ，黄燕^1,2,3

(1. 哈尔滨工业大学（深圳） 索维奇智能材料实验室，材料科学与工程学院，深圳 518055；2. 哈尔滨工业大学 先进焊接与连接国家重点实验，哈尔滨 150001；3. 哈尔滨工业大学（深圳） 深圳市柔性印刷电子技术重点实验室，深圳 518055）

中文说明：

水系电池以其优异的安全性、经济性、环境友好性和高离子导电性成为替代锂离子电池的有力竞争者。然而，电池中电解液的pH值通常会影响电池的电化学性能，甚至影响电池的正常运行。因此，开发能够在各种pH环境下工作的电极材料至关重要。本文采用水热法和硫化处理成功制备了硫化铜纳米片。它可以存储和传输非金属和金属离子以及具有高电荷半径比的多价离子，同时在各种pH条件下正常工作。特别是，CuS电极在碱性条件下具有高容量（900 mAh g-1）、高倍率性能以及超长的放电平台，该平台贡献了总容量的80%。

关键词：水系电池；硫化铜；全pH电解质

     

Enhanced ions and electrons transmission enables high-performance KxMnO@C cathode for hybrid supercapacitors

Manganese oxides have been regarded as one of the most promising electrode materials for energy storage systems. Especially, they can be used as battery-type electrodes in hybrid supercapacitors to achieve high energy density and power density at the same time. In such an application, the redox reaction on the battery-type electrodes needs to speed up to match the fast charging-discharging process of the counter capacitive electrodes. Herein, we intercalated K⁺ ions into MnO₂ to enlarge the interlayer space as channels for ion diffusion, and coated the particles with carbon layer to achieve fast charging/discharging ability. The obtained K_xMnO@C particles delivered a high specific capacitance of 1039 F g^?1 in 5 M LiTFSI aqueous electrolyte. Coupled with activated carbon anode, the hybrid supercapacitor showed outstanding energy and power density.     

Enhancing the Solubility and Transdermal Delivery of Drugs Using Ionic Liquid-In-Oil Microemulsions

The development of hydrophobic drug and protein delivery carriers remains a challenge. To synthesize L-(-)-carnitine-based ionic liquid (IL), this study applies the density functional theory to investigate the hydrogen bonds and van der Waals force that govern L-(-)-carnitine-based IL formation. An ionic liquid-in-oil microemulsion (IL/O ME) is then developed to facilitate the transdermal delivery of proteins and increase the solubility of drugs. IL/O ME is prepared using isopropyl myristate (IPM), Tween 80/Span 20, and L-(-)-carnitine-based IL. The skin permeation studies conducted using mouse skin show that the insulin permeation percentage of the developed IL/O ME is 3.55 folds higher than that of phosphate-buffered saline and 2.91 folds better than that of a hydrophilic L-(-)-carnitine-based IL. In addition, the solubility of two drug molecules, that is, rosiglitazone and bezafibrate, in IL/O ME is at least 49.28 folds higher than their solubility in water or IPM. Therefore, IL/O ME can significantly improve the solubility of drugs and increase the permeability of proteins (e.g., insulin), thus demonstrating a promising potential as a delivery carrier.     

Highly efficient photocatalytic reduction of Cr(VI) by bismuth hollow nanospheres

Uniform bismuth hollow nanospheres with efficient Cr(VI) adsorption capacities were used to the photodegradation of highly toxic Cr(VI) for the first time, which exhibited outstanding visible-light photocatalytic abilities for the reduction of Cr(VI) to less toxic Cr(III).     

An investigation into the enhanced permittivity properties of Zr co-doped (Ga0.5Nb0.5)0.03Ti0.97O2 ceramics

Dielectric materials with high permittivity and low dielectric loss have a range of promising applications within electronic devices. Here, we report on Zr co-doped (Ga_0.5Nb_0.5)_0.03Ti_0.97O₂ ceramics, fabricated using a solid-state reaction. The colossal permittivity (CP) of (Ga_0.5Nb_0.5)_0.03-(Zr_xTi_1-x)_0.97O₂ ceramics was investigated (x = 0%, 1%, 4%, 6%, 10%, 20%). When the doping value of Zr was 4%, the dielectric loss was reduced to 0.098 and, at room temperature and at a frequency of 1000 Hz, the dielectric permittivity was recorded as 2420. In addition, the material's dielectric permittivity exhibited good stability at temperatures ranging from −50 °C to 200 °C. Using X-ray photoelectron spectroscopy (XPS) and Scanning electron microscopy (SEM), we have observed that Zr doping reduces grain size and increases grain boundary regions. According to our XPS and impedance analysis, Zr doping also reduces the concentration of oxygen vacancies, which are considered to be the main cause of dielectric loss. We believe that the Zr doping is an effective method for reducing the dielectric loss of CP materials.     

Nb4C3Tx (MXene) as a new stable catalyst for the hydrogen evolution reaction

This article reports, for the first time, the application of Nb₄C₃T_x in the MXene series satisfying the formula of M₄C₃T_x in the field of hydrogen evolution reaction (HER). New etching parameters are proposed to obtain Nb₄C₃T_x with the largest c-lattice constant (3.165 nm) to date. Notably, Nb₄C₃T_x shows higher catalytic activity under the alkaline condition. Consequently, Nb₄C₃T_x has an overpotential of 398 mV at a current density of 10 mA cm^?2, which is considerably less than that of other reported MXenes. Moreover, Nb₄C₃T_x has superior cycling performance and long-term stability in both acidic and alkaline environments. After 1000 cycles of CV, the overpotential of Nb₄C₃T_x clearly decreased by approximately 30 mV, and the current density significantly increased after the timing current test up to 50 h. This work demonstrates the excellent electrochemical performance that Nb₄C₃T_x can provide to benefit broad application prospects in energy fields.     

织物/纸基柔性印刷电子薄膜导电性能研究

为解决织物/纸基表面缺陷多,与导电油墨结合力差等问题,以更具有普适性的方法即采用PVA改性与PVC改性方式和导电银墨水通过涂布法制备了基于织物/纸基的柔性电子薄膜,其方块电阻均小于10 Ω.通过扫描电子显微镜表征了基底原始形貌、中部改性层和表面银颗粒烧结层微观特征,通过四探针表征了随弯折次数、黏结次数和浸水时间增加其方块电阻值的变化规律.弯折10万次、浸水120 h、黏结20次以上,柔性电子薄膜仍表现出优异的导电性能.探究了丝网印刷工艺参数对印刷精度的影响并总结了丝网印刷常见的印刷缺陷.初步探讨了柔性电子薄膜的应用价值,设计并印制了LED阵列电路,建模并仿真分析了印刷线路板表面贴装电阻工作时的温度及应变分布,设计制备了用于葡萄糖检测的丝网印刷电极,印刷电极具有优良的电子传递性能,其对葡萄糖浓度具有较好的检测性能.