High energy storage properties of lead-free Mn-doped (1-x)AgNbO3-xBi0.5Na0.5TiO3 antiferroelectric ceramics

In this work, 0.2 wt.% Mn-doped (1-x)AgNbO₃-xBi_0.5Na_0.5TiO₃ (x = 0.00–0.04) ceramics were synthesized via solid state reaction method in flowing oxygen. The evolution of microstructure, phase transition and energy storage properties were investigated to evaluate the potential as high energy storage capacitors. Relaxor ferroelectric Bi_0.5Na_0.5TiO₃ was introduced to stabilize the antiferroelectric state through modulating the M₁-M₂ phase transition. Enhanced energy storage performance was achieved for the 3 mol% Bi_0.5Na_0.5TiO₃ doped AgNbO₃ ceramic with high recoverable energy density of 3.4 J/cm³ and energy efficiency of 62% under an applied field of 220 kV/cm. The improved energy storage performance can be attributed to the stabilized antiferroelectricity and decreased electrical hysteresis ΔE. In addition, the ceramics also displayed excellent thermal stability with low energy density variation (<6%) over a wide temperature range of 20−80 °C. These results indicate that Mn-doped (1-x)AgNbO₃-xBi_0.5Na_0.5TiO₃ ceramics are highly efficient lead-free antiferroelectric materials for potential application in high energy storage capacitors.     

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.     

A dinuclear copper(II) complex and a zigzag chain iron(II) polymer based on the 4-antipyrine derived Schiff base ligands: The hydroxylation and redox occurred under the solvothermal conditions

A new dinuclear copper(II) compound, [Cu₂(L1-O)₂] (1) (L1 = (4E)-4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one), and zigzag chain polymer, {[FeCl₂(L2)]}_n (2) (L2 = 1,5-dimethyl-2-phenyl-4-{[(1E)-pyridine-4-ylmethylene]amino}-1,2-dihydro-3H-pyrazol-3-one), were synthesized by solvothermal reactions and structurally characterized. The methyl group hydroxylation and the redox have been observed in the preparation of 1 and 2, respectively.     

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.     

Multi-component assembly of luminescent rare earth hybrid materials

This review focuses on the recent research progress in the multi-component assembly of luminescent rare earth hybrid materials, which is based on the luminescent rare earth compounds and two or more other building units, including the other photoactive species. It covers the multi-component luminescent rare earth hybrids which was assembled with different (a) organic-inorganic polymeric units, (b) nanoporous units, (c) nanoparticle composites or (d) other developing special units. Finally, future challenges and opportunities in this field are discussed. Herein it mainly focuses on the work of Yan's group in recent years.