Countering the Segregation of Transition‐Metal Ions in LiMn1/3Co1/3Ni1/3O2 Cathode for Ultralong Life and High‐Energy Li‐Ion Batteries

High‐voltage layered lithium transition‐metal oxides are very promising cathodes for high‐energy Li‐ion batteries. However, these materials often suffer from a fast degradation of cycling stability due to structural evolutions. It seriously impedes the large‐scale application of layered lithium transition‐metal oxides. In this work, an ultralong life LiMn_1/3Co_1/3Ni_1/3O₂ microspherical cathode is prepared by constructing an Mn‐rich surface. Its capacity retention ratio at 700 mA g^?1 is as large as 92.9% after 600 cycles. The energy dispersive X‐ray maps of electrodes after numerous cycles demonstrate that the ultralong life of the as‐prepared cathode is attributed to the mitigation of TM‐ions segregation. Additionally, it is discovered that layered lithium transition‐metal oxide cathodes with an Mn‐rich surface can mitigate the segregation of TM ions and the corrosion of active materials. This study provides a new strategy to counter the segregation of TM ions in layered lithium transition‐metal oxides and will help to the design and development of high‐energy cathodes with ultralong life.     

锶锌共掺杂磷酸八钙微球制备及其骨修复性能

本文研究了锶、锌共掺杂磷酸八钙多孔微球(Sr/Zn-OCP)的制备及其体内成骨生物学效应。实验运用湿化学合成工艺制备了粒径为105μm、280μm和500μm三种单分散微球颗粒材料,然后再考察微球材料对大白兔股骨缺血性坏死骨缺损的再生修复效应以及微球颗粒度对缺损修复效率的影响规律,运用理化表征与组织学分析考察了微球的微结构和骨组织修复特性。结果显示,利用低浓度聚丙烯酸可以诱导多层化尺度均一的Sr/Zn-OCP多孔微球颗粒形成,并且通过改变反应溶液的搅拌速率可以改变微球的尺度大小;同时,三种粒度微球堆积体均可见骨缺损内新骨再生,但是粒度最大的500μm微球修复骨缺损效率最高,在微球植入术后10、16周时新骨再生率达到37%和62%。以上研究结果表明多孔性Sr/Zn-OCP微球具有优良的生物活性效应,在解决病理性骨缺损再生修复方面具有良好应用价值。     

Synthesis,modification, and porous properties of new glycidyl methacrylate copolymers

Synthesis, copolymerization, and physicochemical properties of new, of different degrees of crosslinker tetrafunctional bis[4(2‐hydroxy‐3‐methacryloyloxypropoxy)phenyl]sulfide and glycidyl methacrylate copolymers are presented. The monomers were used for the synthesis of porous microspheres in the presence of pore‐forming diluents, decan‐1‐ol, and toluene. Influence of diluents composition on their porous structures was studied. Porous structure of the obtained microspheres in dry (from nitrogen adsorption–desorption measurements) states was studied. Their chemical structures were studied by the use of Fourier transform infrared. The number of epoxy groups of the obtained copolymers, their thermal properties (thermogravimetric analysis), and swelling characteristics in 10 solvents of different chemical nature were examined. Selected copolymers were modified by amines in the epoxide ring‐opening reaction. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Grafting of titanium dioxide microspheres with a temperature‐responsive polymer via surface‐initiated atom transfer radical polymerization without the use of silane coupling agents

Titania microspheres with narrow size distribution and diameters of about 1 µm were prepared and subsequently functionalized using surface‐initiated atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide. The ATRP initiator was immobilized on the particle surface via acylation of surface hydroxyl groups with α‐bromoisobutyryl bromide. Subsequently, an established ATRP reaction system was used for the preparation of titania surface‐grafted poly(N‐isopropylacrylamide) (PNiPAAm). Characterization was performed with electron microscopies, X‐ray diffraction, infrared spectroscopy and dynamic light scattering. It was found that the particle size in aqueous dispersions changed reversibly with temperature as expected for a shell of PNiPAAm, a polymer with a lower critical solution temperature at 32 °C. This confirmed the successful preparation of functional, stimuli‐responsive TiO₂ microparticles via a straightforward controlled surface‐initiated polymerization method.     

陶瓷UO2畸形球的控制方法

研究了用于高温气冷核反应堆燃料核芯中畸形球的种类、产生机理及其控制方法。在500 ℃以下空气中进行了脱碳研究，结果发现破裂球(缺裂球、沟槽球等)的产生基本上来源于干球的不完全脱碳所致。在振动分散条件下进行了溶胶的分散研究。结果发现，孪生球和椭圆球的形成基本上来源于溶胶的不均匀分散所致。因此，为了控制和防止上述两类畸形球的形成，最重要的方法是，(1)必须在一定脱碳程序下供给必要的空气量，确保脱碳完全；(2)必须采用合理的溶胶参数下保持均匀分散，以保证球形均匀。     

Simple and Sensitive HPLC Method with Fluorescence Detection for the Measurement of Ibuprofen in Rat Plasma: Application to a Long-Lasting Dosage Form

A simple and sensitive high-performance liquid chromatography (HPLC) assay applied to the measurement of ibuprofen in rat plasma has been developed. Two parameters have been investigated to improve ibuprofen detectability using fluorescence detection: variation of mobile phase pH and the use of β-cyclodextrin (β-CD). Increasing the pH value from 2.5 to 6.5 and adding 5 mM β-CD enhanced the fluorescence signal (λ_exc = 224 nm; λ_em = 290 nm) by 2.5 and 1.3-fold, respectively, when using standards. In the case of plasma samples, only pH variation significantly lowered detection and quantification limits, down to 10 and 35 ng/mL, respectively. Full selectivity was obtained with a single step for plasma treatment, that is, protein precipitation with acidified acetonitrile. The validated method was applied to a pharmacokinetic study of ibuprofen encapsulated in microspheres and subcutaneously administered to rats.     

Ketoprofen Spray-dried Microspheres Based on Eudragit® RS and RL: Study of the Manufacturing Parameters

The preparation of ketoprofen spray-dried microspheres can be affected by the long drug recrystallization time. Polymer type and drug–polymer ratio as well as manufacturing parameters affect the preparation. The purpose of this work was to evaluate the possibility to obtain ketoprofen spray-dried microspheres using the Eudragit® RS and RL; the influence of the spray-drying parameters on morphology, dimension, and physical stability of microspheres was studied. Ketoprofen microspheres based on Eudragit® blend can be prepared by spray-drying and the nebulization parameters do not influence significantly particle properties; nevertheless, they can be affected by drying and storage methods. No effect of the container material is found.     

Preparation of monodisperse hydrophilic polymer microspheres with N,N′‐methylenediacrylamide as crosslinker by distillation precipitation polymerization

Highly crosslinked cauliflower‐like poly(N,N′‐methylenebisacrylamide) particles were prepared by distillation precipitation polymerization in neat acetonitrile with 2,2′‐azobisisobutyronitrile as initiator. Monodisperse hydrophilic polymer microspheres with various functional groups, such as amide, pyrrolidone and carboxylic acid, with a spherical shape and smooth surface in the size range 120–600 nm were prepared by distillation precipitation copolymerizations of functional comonomers including N‐isopropylacrylamide, N‐vinylpyrrolidone, methacrylic acid with N,N′‐methylenebisacrylamide as crosslinker. The polymer particles were formed and precipitated out from the reaction medium during the distillation of the solvent from the reaction system through an entropic precipitation manner. The effects of the solvent and the degree of crosslinking on the morphology and the loading capacity of the functional groups of the resultant polymer particles were investigated. The resulting polymer particles were characterized with scanning electron microscopy, transmission electron microscopy, dynamic light scattering and Fourier transform infrared spectroscopy. Copyright © 2007 Society of Chemical Industry     

Subpixel position measurement using 1D, 2D and 3D centroid algorithms with emphasis on applications in confocal microscopy

The accuracy with which centroid algorithms in 1D, 2D and 3D can estimate an object's position has been investigated. Three factors that can influence the method's accuracy have been investigated: systematic error of the algorithm, influence of photon noise and the influence of perturbations such as scanning nonlinearity. The variation of the accuracy with parameters that are relevant for confocal microscopy, such as object diameter and photon noise/pixel, has been considered. Theory and simulations presented show that the variation of the accuracy with respect to such parameters can differ drastically between the 1D, 2D and 3D cases. Experiments performed using microspheres show that the magnitudes of the three types of error can be approximately the same under normal operating conditions and that it is therefore necessary to take all three into account when assessing the total error.     

Magnetite‐coated polystyrene hybrid microspheres prepared by miniemulsion polymerization

Hybrid microspheres with a polystyrene core coated with magnetite nanoparticles were prepared by miniemulsion polymerization. Acrylic acid was used as a comonomer to promote the anchoring of the magnetite nanoparticles onto the polymeric surface. The addition of a hydrophobic agent prevents effectively the monomer from diffusing into the aqueous phase. Magnetite was treated with a silane coupling agent in order to introduce some interactions with the polymers. The morphology and the structure of the hybrid microspheres were characterized using X‐ray diffraction, infrared spectroscopy, transmission electron microscopy and thermogravimetric analysis. The results show that the morphology of the hybrid microspheres was influenced by the concentrations of acrylic acid, hydrophobic agent and surfactant, and that the degree of coating can be tuned by changing these parameters. The miniemulsion polymerization technique is adaptable to the synthesis of magnetite‐coated polymer particles, and the synthesis can be scaled up. Copyright © 2008 Society of Chemical Industry