Tuning magnetic properties of BiFeO3 thin films by controlling Mn doping concentration

Mn-doped BiFeO₃ (BiFe_1–xMn_xO₃, x = 0, 0.03, 0.05, 0.10, 0.15 and 0.20) polycrystalline multiferroic thin films were successfully synthesized using the facile sol-gel spin-coating method. The crystal structures, surface features, elements valences, and magnetic properties of as-prepared samples were systematically explored. X-ray diffraction and Raman spectroscopy studies revealed the substitutions of Mn into the Fe site and a rhombohedral-to-orthorhombic phase transition. The Field Emission Scanning Electron Microscopy showed a decrease in the average particle sizes and an improvement of surface morphology with increasing the concentration of the substitutes. Energy-dispersive X-ray spectroscopy confirmed the doping concentration of Mn²⁺ in the samples. X-ray photoelectron spectroscopy indicated the co-existence of Mn²⁺/Mn³⁺ ions in the doped films. The remnant magnetization value of BiFe_0.90Mn_0.10O₃ thin film was found to be approximately six times than that of pure BiFeO₃ thin film under a magnetic field of 10 kOe. The enhanced magnetic property of BiFe_0.90Mn_0.10O₃ thin film was mainly ascribed to the structural distortion of spin cycloid and the enhancement of super-exchange interaction between the Fe³⁺ (Mn²⁺) and O^2- ions.     

Synthesis of blue-emitting AlN:Eu2+ spherical phosphors by carbothermal reduction nitridation method

In this study, blue-emitting AlN:Eu²⁺ spherical phosphors were successfully synthesized for the first time by the carbothermal reduction nitridation (CRN) method, assisted with high nitrogen pressure, appropriate synthesis temperature, and the addition of CaF₂. The influence of typical experimental parameters, such as N₂ pressure, heating temperature, CaF₂ content and Eu²⁺ concentration on the morphologies and luminescence properties of AlN phosphors were comprehensively investigated. The formation mechanism of spherical morphology were significantly proffered, indicating that sufficient liquid Ca-aluminates during the AlN growth stage were essential for the spheroidization process under the action of surface tension. The synthesized AlN:Eu²⁺ spherical phosphors presented an intense blue emission band centered in the range of 427- 476 nm relative to the reaction temperature. The lifetime of AlN:Eu²⁺ phosphor was calculated to be around 1.89 μs. The temperature-dependent PL spectra suggested that the emission band did not shift until 225°C. In addition, the spectral analysis strongly suggested that the luminescence property of AlN:Eu²⁺ phosphors was significantly enhanced by the large particle size, spherical morphology, reduced impurity content, and appropriate Eu²⁺ concentration.     

Metal organic frameworks as electrocatalysts: Hydrogen evolution reactions and overall water splitting

The development of clean energy technologies to protect the environment is an important demand of the times. Electrocatalysis is emerging as a promising method for evolution of hydrogen and overall water splitting. Nowadays, metal organic frameworks (MOFs) have emerged as electrocatalysts having uniformly distributed active sites and high electrical conductivity. This review summarizes the latest advances in heterogeneous catalysis by MOFs and their composite/derivatives for efficient hydrogen evolution reaction (HER) and water splitting. Pristine MOFs with their recent development are summarized first followed by composites of MOFs with their enhanced electrocatalytic performances. Overall water splitting by using bifunctional electrocatalysts derived from MOFs with different synthetic approaches is provided and this review gives the metal-based categorisation of precursor MOFs. Different strategies to improve chemical stability, conductivity, and overall electrocatalytic properties have been discussed. In the last, perspectives on the synthesis of efficient MOF-based electrocatalyst materials are provided.     

Phenol degradation by isolated bacterial strains: kinetics study and application in coking wastewater treatment

BACKGROUND: In biological treatment of coking wastewater, phenol may decrease the treatment efficiency because of its high concentration and toxicity to microorganisms. Bioaugmentation has been regarded as a good improvement of the traditional biological treatment using isolated degrading strains. In this study, two phenol degrading strains, Pseudomonas sp. PCT01 and PTS02, were isolated and investigated for degradation ability and application to real coking wastewater treatment. RESULTS: Complete phenol degradation was achieved after 18 h inoculation in medium containing 229‐461 mg L^?1 of phenol for both strains. The presence of phenol, pyridine and other compounds in mixed substrate or in coking wastewater prolonged the degradation to 20‐32 h with an initial phenol concentration of 160‐280 mg L^?1. The study of degradation kinetics yielded a two‐stage model to describe the effect of the initial phenol concentration and inhibitory compounds on phenol degradation. The highest degradation rate constant of the second stage, 1.25 h^?1 for PCT01 and 0.75 h^?1 for PTS02, was obtained at low phenol concentration in a single substrate. CONCLUSION: It was found that both strains could degrade phenol effectively and maintain their phenol degradation ability in coking wastewater, and therefore could be used for bioaugmentation treatment of coking wastewater. Copyright © 2011 Society of Chemical Industry     

Preparation and properties of polymer-encapsulated phthalocyanine blue pigment via emulsion polymerization

Polymer-encapsulated phthalocyanine blue pigment dispersion was prepared with a polymerizable dispersant by emulsion polymerization method, and the effect of preparation conditions on the particle size of dispersion was investigated. Dynamic light scattering measurement demonstrated that allyloxy nonyl-phenoxypropanolpolyoxyethyleneetherammonium sulfonate (ANPS) was suitable for phthalocyanine blue pigment modification. The polymer-encapsulated phthalocyanine blue pigment dispersion with the small particles was obtained when the mass ratio of ANPS to phthalocyanine blue pigment, styrene (St) to phthalocyanine blue pigment, and ammonium persulfate (APS) to St was about 0.2, 0.2, and 0.01, respectively. Transmission electron microscopy (TEM), Fourier transforms infrared spectra (FTIR) and thermogravimetric analyses (TGA) provided supporting evidences for the encapsulation of phthalocyanine blue pigment with the formed copolymer. The polymer-encapsulated phthalocyanine blue pigment dispersion showed excellent stabilities to freeze–thaw treatment and centrifugal force.     

气候变化背景下室外计算干球温度统计时长的选取

阐述了气候变化背景下用于确定室外计算干球温度的气象数据统计时长的方法。基于确定统计时长的两个基本原则,根据标准差方法和最优气候均态模型,分别确定室外计算干球温度最小统计时长和气象要素最优平均数,通过两者的对比选取室外计算干球温度统计时长。以天津为例进行分析,结果表明,天津地区基于ASHRAE方法的累积发生频率为0.4%,1.0%和2.0%干球温度的统计时长应取15年,累积发生频率为99.0%和99.6%干球温度的统计时长应取10年;基于中国方法的供暖室外计算温度、冬季空调室外计算温度和夏季空调室外计算干球温度的统计时长分别应取13,10和15年。     

桥梁预制施工流程优化的若干建议措施

预制拼装属于一种现代化的桥梁施工技术，为进一步解决存在的各种技术问题，本文将在探讨如何选择和布置桥梁预制场的基础上，深入分析桥梁预制节段拼装技术的应用，以此总结出桥梁预制施工流程优化的建议措施。