Remarkably enhanced energy storage properties of lead-free Ba0.53Sr0.47TiO3 thin films capacitors by optimizing bottom electrode thickness

The lead-free Ba_0.53Sr_0.47TiO₃ (BST) thin films buffered with La_0.67Sr_0.33MnO₃ (LSMO) bottom electrode of different thicknesses were fabricated by pulsed laser deposition method on a (001) SrTiO₃ substrate. It was found that the roughness of electrode decreases and substrate stress relaxes gradually with the increase of LSMO thickness, which is beneficial for weakening local high electric field and achieving higher E_b. Therefore, the recoverable energy density (W_rec) of BST films can be greatly improved up to 67.3 %, that is, from 30.6 J/cm³ for the LSMO thickness of 30 nm up to 51.2 J/cm³ for the LSMO thickness of 140 nm after optimizing the LSMO thickness. Furthermore, the thin film capacitor with a 140 nm LSMO bottom electrode shows an outstanding thermal stability from 20 °C to 160 °C and superior fatigue resistance after 10⁸ electrical cycles with only a slightly decrease of W_rec below 1.6 % and 3.7 %, respectively. Our work demonstrates that optimizing bottom electrodes thickness is a promising way for enhancing energy storage properties of thin-film capacitors.     

Synthesis of N-methylglucamine modified macroporous poly(GMA-co-TRIM) and its performance as a boron sorbent

A chelating polymeric sorbent was developed by functionalizing poly(glycidyl methacrylate-co-trimethylolpropane trimethacrylate), poly(GMA-co-TRIM), with N-methylglucamine (MG) via a simple post-grafting route. The resulting well-defined millimeter-sized spheres of poly(GMA-co-TRIM)–MG had permanent macropore structures and low swelling degree, with accessible ligands of 1.84 mmol/g. The boron adsorption behavior of the sorbent was studied in batch mode by varying different parameters like the pH value, the initial concentration of boron and the adsorption time under noncompetitive conditions. It was found that the sorbent always maintained the high capacity between pH 2.6 and 8.6, in which the optimum pH was 7.5. The adsorption behavior of the sorbent obeyed the Langmuir isotherm well. The adsorption capacity of the sorbent for boron was in the same level as that of a commercially available N-methylglucamine-type polystyrene resin. However, it adsorbed boron more quickly. The sorbent also showed good durability and reusability through the fixed-bed adsorption tests. The study on the separation of boron from brine of salt lake showed a high selectivity of the sorbent, though the capacity for boron decreased due to the interference of diverse ions in brine.     

The preparation and gas sensitivity study of polypyrrole/zinc oxide

Polypyrrole (PPy) was prepared by chemical oxidation polymerization, analyzed by FT-IR, elemental analysis and HRTEM, and studied for gas sensitivity. It suggested that PPy had sensitivity to NH₃, H₂S and NO_x, and showed irreversibility to NO_x gas. The organic–inorganic hybrid materials PPy/ZnO with different PPy weight percents were prepared by mechanical mixing, and the sensitivity study of the materials to toxic gases NH₃, H₂S, NO_x was carried out at different operating temperatures 30, 60, and 90 °C. It was found that PPy/ZnO materials (PPy(1%)/ZnO, PPy(3%)/ZnO, PPy(5%)/ZnO, PPy(10%)/ZnO, PPy(20%)/ZnO) had better selectivity and reversibility to NO_x than pure PPy, and much lower working temperature than the reported working temperature of ZnO (about 350–450 °C). Their sensitivity increased with the increasing concentration of NO_x at particular working temperature, and among them PPy(10%)/ZnO had the maximum sensitivity to NO_x in the same condition. They showed no response to 1000, 1500, 2000 ppm NH₃ or H₂S. The response mechanism of PPy/ZnO materials to NO_x was discussed.     

Effect of temperature and moisture on electrical conductivity in polyaniline/polyurethane (PANI/PU) blends

Miscible blend of conductive polyaniline/polyurethane (PANI/PU) showed preferable electrical property at low percolation threshold compared to immiscible blend of PANI/polystyrene-isoprene-copolymer (PANI/SIS) and carbon black/PU composite (CB/PU). The time dependence of the electrical conductivity was investigated with these samples aged under different humidity and temperatures. The electrical conductivity of PANI/PU (11.5/88.5, v/v) decreased with aging time and the morphology changed with time in the coexistence of high moisture and high temperature. After the aging treatment, the film of the miscible blend was re-dissolved and re-cast. The morphology and electrical conductivity were found to recover to the same state as the original film. In addition, the recovery mechanism of the morphology and the conductivity was also proposed here.     

Effective composite image detection method based on feature inconsistency of image components

This paper proposes an effective composite image detection method that uses the feature inconsistency of image components of the composite image to detect tampered regions. The composite image is first divided into image components. Next, the variance of the noise remaining after de-noising in each image component is calculated and used as a feature. Finally, tampered regions are detected using this feature based on a tampering detection rule. Experimental results show that the proposed method has good composite image detection performance.     

A dually spontaneous reduction and assembly strategy for hybrid capsules of graphene quantum dots with platinum–copper nanoparticles for enhanced oxygen reduction reaction

The unique hybrid capsules of graphene quantum dots (GQDs) with platinum (Pt)–copper (Cu) nanoparticles have been prepared by a dually spontaneous reduction and assembly process of oxidized graphene quantum dots (ox-GQDs) and Pt precursor by galvanic displacement reaction on Cu microspheres. Cu@PtCu core–shell microspheres were first prepared by reaction of Cu with platinum (IV), which subsequently induced the reduction and assembly of ox-GQDs on them at room temperature. After removal of the Cu cores, the resultant capsules of PtCu@GQDs were collected. Based on the unique hybrid structure, PtCu@GQDs capsules showed remarkably enhanced catalytic activity for oxygen reduction reaction (ORR) with a 2 times higher mass activity and a 40 mV more positive onset potential than that of commercial Pt black, indicating the promise of the newly-prepared PtCu@GQDs capsules as catalysts for fuel cell applications.     

Effect of Eu3+-doping on morphology and fluorescent properties of neodymium vanadate nanorod-arrays

Tetragonal structural (t-NdVO₄) nanorod-arrays were fabricated by simple one-pot hydrothermal method. The phase, morphology and microstructure of NdVO₄ were characterized by X-ray diffractometer, scanning electron microscope (SEM), transmission electron microscope (TEM), dispersive X-ray spectrometer (EDS) and selected area electron diffraction (SAED) techniques. t-NdVO₄ nanorods are single-crystalline with a length of 100 nm and a diameter of 25 nm, which grow orientally along the direction of (112) crystalline plane and self-assemble to form nanorod-arrays. The results show that Eu³⁺-doping interrupts the formation of NdVO₄ nanorod-arrays, and then leads to the red-shift of the strongest luminescence emission of Nd³⁺ transition from ⁴D_3/2 state to ⁴I_11/2 and decreases its intensity of the fluorescence emission at 400 nm sharply. The research results have some reference values to optimize the photoluminescence performance of rare earth vanadates.     

Effect of K2O content on breakdown strength and energy-storage density in K2O-BaO-Nb2O5-SiO2 glass-ceramics

Phase evolution, dielectric properties, breakdown strength, and energy-storage performance were studied by varying K₂O content in K₂O-BaO-Nb₂O₅-SiO₂ glass-ceramics. It was found that dielectric loss with the increase of K₂O content increases owing to the un-crystallized K₂O into the glass network, while dielectric breakdown strength firstly increases and then decreases due to the competition between two physical mechanisms, i.e., interfacial polarization and bridging-oxygen bond broken by the non-bridging oxygen ions. With the increase of K₂O content, energy-storage density firstly increased up to 12.06±0.69 J/cm³ with a high breakdown strength of 1973 kV/cm, and then decreased. Also, the discharged efficiency is obtained as a high value of 92% from P-E hysteresis loops.     

基于石墨烯透明导电薄膜的OLED研究进展

作为透明导电薄膜材料,石墨烯（Graphene）因具有十分优异的力学、光学和电学特性,在未来的柔性光电器件如触摸屏、有机发光二极管（OLED）和有机光伏电池（OPV）中表现出极大的发展潜力和广阔的应用前景。然而,受面电阻大、功函数不匹配以及表面粗糙度等关键因素的影响,基于本征石墨烯薄膜的光电器件的性能较低、稳定性较差,严重阻碍了石墨烯薄膜在柔性光电器件中的发展和应用。主要针对近年来石墨烯透明导电薄膜在OLED中应用的研究进展进行概述,并总结得出可以通过石墨烯薄膜掺杂、表面功函数修饰、清洁无损转移,以及器件结构优化等方法,进一步提高器件的性能。最后分析了石墨烯透明导电薄膜在OLED器件应用中的关键技术瓶颈,并对石墨烯透明导电薄膜在OLED中的应用前景进行了展望。     

Relaxor antiferroelectric-like characteristic boosting enhanced energy storage performance in eco-friendly (Bi0.5Na0.5)TiO3-based ceramics

Ideal relaxor antiferroelectrics (RAFEs) have high field-induced polarization, low remnant polarization and very slim hysteresis, which can generate high recoverable energy storage W_rec and high energy storage efficiency η, thus attracting much attention for energy storage applications. True RAFEs, on the other hand, are extremely rare, and the majority of them contain environmentally hazardous lead. In this work, we use a viscous polymer rolling process to synthesize a novel and eco-friendly 0.65Bi_0.5Na_0.4K_0.1TiO₃-0.35[2/3SrTiO₃-1/3Bi(Mg_2/3Nb_1/3)O₃] (BNKT-ST-BMN) dielectric material, which possesses a very typical RAFE-like characteristic. As a result, this material has a high W_rec of 4.43 J/cm³ and a η of 86% at an electric felid of 290 kV/cm, as well as a high thermal stability of W_rec (>3 J/cm³) over a wide range of 30–140 °C at 250 kV/cm. Our findings suggest that the BNKT-ST-BMN material could be a potential candidate for use in energy storage pulse capacitors.