Photovoltaic Properties of Multiferroic BiFeO3/BiCrO3 Heterostructures

We report a power conversion efficiency of ~0.01% in multistacking of BiFeO₃/BiCrO₃ bilayer thin films used as active layers in a photovoltaic (PV) device. The films were epitaxially deposited by pulse laser deposition onto (100) oriented CaRuO₃‐coated LaAlO₃ substrates and were subsequently illuminated with 1 sun (AM 1.5). The fill factor is determined to be 0.31%, a remarkable value for ferroelectric‐ and multiferroic‐based PV devices. Our results demonstrate that photocurrent density and photovoltage can be tuned by varying the thickness and number of respective bilayers in the improvement of PV properties of multiferroic heterostructures. The maximum photocurrent is generated at an optimal multilayer thickness of 60 nm, with its origin being mainly ascribed to the contribution of ferroelectric polarization.     

纳米BiFeO3的制备及其光催化性能研究进展

在众多多铁性化合物中,铁酸铋是目前已知唯一一种在室温下同时具有磁性和强铁电性的材料。近年来,纳米BiFeO_3(BFO)材料常用于光催化领域研究,目前主要通过控制粒子大小和形状来提高其光催化性能,或掺杂各种金属元素以及设计相关复合材料等。本文从BFO纳米材料的制备工艺入手,综述了几种常见方法,包括溶胶-凝胶法、水热法、共沉淀法。总结了铁酸铋光催化剂的性能改进方式及其研究进展。     

Pr和Co共掺杂BiFeO3结构和多铁性的研究

溶胶-凝胶法制备了BiFe0.95Co0.05O3、Bi0.95 Pr0.05FeO3和Bi0.95Pr0.05Fe0.95Co0.05O3样品。X射线衍射仪、铁电分析仪和振动样品磁强计测量与分析了样品结构、铁电和铁磁性能。结果表明:共掺杂的样品磁性有所增强,这与样品的结构变化有关。Pr掺杂提高了材料的铁电性能,这是因为Pr掺杂减少了氧空位。     

Optimization of Parameters to Improve the Properties of AA7178/Si3N4 Composites Employing Taguchi Approach

Silicon - In the recent days, the employ of aluminum alloy has enriched dramatically especially in engineering applications extensively employed in ship building, aerospace, structural,...     

BiFeO3 Ceramics: Processing,Electrical, and Electromechanical Properties

Bismuth ferrite (BiFeO₃), a perovskite material, rich in properties and with wide functionality, has had a marked impact on the field of multiferroics, as evidenced by the hundreds of articles published annually over the past 10 years. Studies from the very early stages and particularly those on polycrystalline BiFeO₃ ceramics have been faced with difficulties in the preparation of the perovskite free of secondary phases. In this review, we begin by summarizing the major processing issues and clarifying the thermodynamic and kinetic origins of the formation and stabilization of the frequently observed secondary, nonperovskite phases, such as Bi₂₅FeO₃₉ and Bi₂Fe₄O₉. The second part then focuses on the electrical and electromechanical properties of BiFeO₃, including the electrical conductivity, dielectric permittivity, high‐field polarization, and strain response, as well as the weak‐field piezoelectric properties. We attempt to establish a link between these properties and address, in particular, the macroscopic response of the ceramics under an external field in terms of the dynamic interaction between the pinning centers (e.g., charged defects) and the ferroelectric/ferroelastic domain walls.     

Influences of Cr Doping on the Electrical Properties in BiFeO3 Thin Films

Cr-doped BiFeO₃ (BFO) thin films were deposited on Pt(200)/TiO₂/SiO₂/Si(100) substrates by a chemical solution deposition method. The dielectric constant and dissipation factor of the BFO thin films decrease from 165 and 0.054 (undoped) to 100 and 0.02 (3 mol% Cr-doped) at a frequency of 10 kHz as the Cr content increases. The leakage current and ferroelectric properties were improved significantly by means of Cr doping. The leakage current density of 4.1×10^-6 A/cm² for the 3 mol% Cr-doped BFO thin film is about four orders of magnitude lower than that of undoped BFO thin film at an external electric field of 100 kV/cm. The 3 mol% Cr-doped BFO thin film exhibited a well-saturated hysteresis loop with a large remanent polarization (P_r) of 61 μC/cm² at room temperature. The reason for the improved leakage current and ferroelectric properties in Cr-doped BFO thin films can be attributed to the reduced oxygen vacancies in the films by Cr doping.

Communicated by Dr. George W. Taylor     

提高石化产品质量管理新途径探析

质量是企业的生命,企业要想在激烈的市场竞争中占稳脚跟,必须练好内功,强化生产过程的质量管理。油品质量管理是企业科技水平的体现。石油化工企业生产运行全程存在着明显的连续性特点,在质量控制中,对生产过程进行合理有效控制是其核心。由于石化产品品种多、牌号杂,为保证产品质量必须要加强质量管理,降低生产成本,使企业的各项经济指标达到世界先进水平。     

Synthesis and photocatalytic activity of BiFeO3 and Bi/BiFeO3 cubic microcrystals

BiFeO₃ and Bi/BiFeO₃ cubic microcrystals were synthesized in this work. The phase, microstructure, optical and photo electrochemical properties, as well as the photocatalytic activities in photocatalytic hydrogen generation were investigated. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results demonstrate the successful synthesis of BiFeO₃ and Bi/BiFeO₃. The scanning electron microscope (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray (EDX) results give the evidence of cubic morphology and the deposition of metal Bi on the surface of BiFeO₃. The absorption spectra show that Bi/BiFeO₃ has longer absorption edge and stronger absorption capability to visible light. The photocurrent curves, emission spectra, and electrochemical impedance spectroscopy (EIS) spectra demonstrate that Bi/BiFeO₃ has higher efficiency of electron-hole separation and charge transfer, as well as longer lifetime of the charge carriers. These benefit to the enhancement of activity in photocatalytic hydrogen generation.     

Dielectric,Ferroelectric, and Piezoelectric Properties of BiFeO3–BaTiO3 Ceramics

Perovskite solid solution ceramics of (1 ? x)BiFeO₃–xBaTiO₃ (1 ? x)BF–xBT, 0.2 ≤ x ≤ 0.45) with high electrical resistivity were prepared by solid‐state reaction method. Actual ferroelectric hysteresis loops and temperature dependence of dielectric constant of the ceramics were obtained. Ceramics of 0.7BF–0.3BT with small rhombohedral distortion show highest remnant polarization (P_r = 26.0 μC/cm²) and piezoelectric coefficient (d₃₃ = 134 pC/N). Compositions with pseudo‐cubic symmetry (intermediate phases) show relaxor‐like dielectric anomaly. The values of P_r and d₃₃ decrease with increasing BT content, from 24.8 μC/cm² and 104 pC/N for 0.65BF–0.35BT to 8.2 μC/cm² and 5 pC/N for 0.55BF–0.45BT.     

Novel Formulations Containing Fluorescent Sensors to Improve the Resolution of 3D Prints

Three-dimensional printing in SLA (stereolithography) and DLP (digital light processing) technologies has recently been experiencing a period of extremely rapid development. This is due to the fact that researchers recognise the many advantages of 3D printing, such as the high resolution and speed of the modelling and printing processes. However, there is still a search for new resin formulations dedicated to specific 3D printers allowing for high-resolution prints. Therefore, in the following paper, the effects of dyes such as BODIPY, europium complex, and Coumarin 1 added to light-cured compositions polymerised according to the radical mechanism on the photopolymerisation process speed, polymerisation shrinkage, and the final properties of the printouts were investigated. The kinetics of the photopolymerisation of light-cured materials using real-time FT-IR methods, as well as printouts that tangibly demonstrate the potential application of 3D printing technology in Industry 4.0, were examined. These studies showed that the addition of dyes has an effect on obtaining fluorescent prints with good resolution.     

A Novel Approach to Sintering Nanocrystalline Barium Titanate Ceramics

A novel approach to pressureless sintering based on the combination of rapid-rate sintering, rate-controlled sintering, and two-step sintering under a controlled atmosphere is proposed. This combined sintering method facilitates control of grain and pore morphology. The application of this sintering approach for pure nanocrystalline barium titanate powder enables the suppression of grain growth during the intermediate and final stages of sintering and the production of fully dense ceramics with 108 nm grain size. The grain growth factor is 3.5, which is three and 17 times smaller than rate-controlled and conventional sintering, respectively.     

A Novel Approach to the Preparation of a Highly Crystallized BaTiO3 Layer on Ni Nanoparticles

A novel chemical approach is proposed to facilitate the crystallization of the BaTiO₃ coating layer on Ni nanoparticles for multilayer ceramic capacitors. Based on the chemical equilibrium principle, the polycrystalline coating layer can be obtained at atmospheric pressure and at a relatively low temperature by a one‐step reaction. The details of the coating process of the Ni nanoparticles are clearly discussed. The coating is uniform, dense, and well crystallized, and can protect the Ni from oxidation and also shift the starting point of Ni densification to a higher temperature, reducing differential shrinkage issues in the co‐firing.     

Novel Techniques to Improve Precise Cell Injection

We noted recently that the injection of cells with a needle through a cystoscope in the urethral sphincter muscle of pigs failed to deposit them nearby or at the intended target position in about 50% of all animals investigated (n > 100). Increasing the chance for precise cell injection by shotgun approaches employing several circumferential injections into the sphincter muscle bears the risk of tissue injury. In this study, we developed and tested a novel needle-free technique to precisely inject cells in the urethral sphincter tissue, or other tissues, using a water-jet system. This system was designed to fit in the working channels of endoscopes and cystoscopes, allowing a wide range of minimally invasive applications. We analyze key features, including the physical parameters of the injector design, pressure ranges applicable for tissue penetration and cell injections and biochemical parameters, such as different compositions of injection media. Our results present settings that enable the high viability of cells post-injection. Lastly, the method is suitable to inject cells in the superficial tissue layer and in deeper layers, required when the submucosa or the sphincter muscle of the urethra is targeted.     

水热法制备BiFeO3粉体

以FeC l3.6H2O和B i(NO3)3.5H2O为原料,氨水为沉淀剂,KOH为矿化剂,采用共沉淀法制备前驱物,水热法合成了纯相的B iFeO3粉体。X射线衍射结果表明,在160℃,碱浓度仅为0.15 mol/L的水热条件下,即可合成纯相的B iFeO3粉体。该工艺大大降低了水热温度,减小了碱浓度,从而节约了能源,降低了成本,减轻了碱对水热设备的腐蚀。扫描电镜显示,前驱沉淀物陈化时间为1 d时,水热制备的B iFeO3粉体中有发育良好的六方短柱状晶体形成;陈化时间增加到3 d时,所得B iFeO3粉体呈双层板状。差热-失重分析表明,所得B iFeO3粉体的尼尔温度(TN)为301℃,居里温度(TC)为828℃,分解温度为964℃。     

MG-Pe: A Novel Galectin-3 Ligand with Antimelanoma Properties and Adjuvant Effects to Dacarbazine

Melanoma is a highly metastatic and rapidly progressing cancer, a leading cause of mortality among skin cancers. The melanoma microenvironment, formed from the activity of malignant cells on the extracellular matrix and the recruitment of immune cells, plays an active role in the development of drug resistance and tumor recurrence, which are clinical challenges in cancer treatment. These tumoral metabolic processes are affected by proteins, including Galectin-3 (Gal-3), which is extensively involved in cancer development. Previously, we characterized a partially methylated mannogalactan (MG-Pe) with antimelanoma activities. In vivo models of melanoma were used to observe MG-Pe effects in survival, spontaneous, and experimental metastases and in tissue oxidative stress. Analytical assays for the molecular interaction of MG-Pe and Gal-3 were performed using a quartz crystal microbalance, atomic force microscopy, and contact angle tensiometer. MG-Pe exhibits an additive effect when administered together with the chemotherapeutic agent dacarbazine, leading to increased survival of treated mice, metastases reduction, and the modulation of oxidative stress. MG-Pe binds to galectin-3. Furthermore, MG-Pe antitumor effects were substantially reduced in Gal-3/KO mice. Our results showed that the novel Gal-3 ligand, MG-Pe, has both antitumor and antimetastatic effects, alone or in combination with chemotherapy.     

A Novel Approach to Bioleach Soluble Phosphorus from Rock Phosphate

A novel approach to bioleach soluble phosphorus from rock phosphate, involving the bio-oxidation of pyrite by adaptated Acidithiobacillus ferrooxidans (At. f) and the product of sulfuric acid to dissolve rock phosphate, has been proposed in this paper. The soluble phosphorus could be leached more effectively in the presence of pyrite by At. f than that leached directly by sulfuric acid. The optimal technological parameters are presented. The highest phosphorus leaching rate is 9.00% when the culture substrate is the mixture of FeSO4·7H2O and pyrite, the phosphorus leaching rate is 8.00% when the initial pH and culture time are 2.5 and 5 d, respectively. The optimal rock phosphate particle size is 0.05 mm for the leaching of phosphorus. The bigger the grains of pyrite, the lower the phosphorus leaching rate. The bacterium At. f should be appropriately adaptated, which makes it easier to bioleach soluble phosphorus from rock phosphate.     

Magnetic and Dielectric Properties of Nanostructured BiFeO3 Prepared by Sol–Gel Method

Polycrystalline BiFeO₃ was synthesized at 400°C–700°C. Distinctive difference in the magnetic and dielectric properties was observed between the samples sintered at 400°C–500°C and those sintered at 600°C–700°C. The former showed ferromagnetic‐like hysteresis loops with an increased magnetization of 0.54 emu/g, whereas the later showed linear loops with a small magnetization of 0.065 emu/g. Although X‐ray did not identify any secondary phase, the suspected trace of some magnetic phase (Fe₃O₄) in the samples was conceded by the occurrence of an exchange bias. The difference in dielectric response between the two groups of samples arose mainly from a different conductivity at the grain boundaries. Owing to Fe₃O₄ coating at grain surface, the 400°C–500°C sintered samples behaved like a single parallel R–C circuit, whereas the dielectric response of the samples sintered at 600°C–700°C was represented by a series of two parallel R‐C units for grains and grain boundaries, respectively. Two dielectric relaxation peaks observed at <700 Hz and 0.3~6 MHz in the high‐temperature sintered samples were attributed to the Maxwell–Wagner relaxation and electron hopping, respectively.