类球形正交LiMnO2的制备、微结构和电化学性能

以共沉淀法得到的类球形MnCO₃为前驱物，制备了类球形正交LiMnO₂(So-LiMnO₂)，采用XRD、SEM和N₂吸附技术对样品进行表征；与非球形正交LiMnO₂(No-LiMnO₂)进行了对比研究。结果表明：o-LiMnO₂的堆垛层错度、结晶状况、颗粒形貌和大小与前驱物的微结构密切相关；在80次电化学循环测试过程中，So-LiMnO₂经15次循环可达最大的放电容量152 mAh·g^-1，其容量衰减平均每次循环0.58 mAh·g^-1；而No-LiMnO₂要经过38次循环才能达到最大放电容量128 mAh·g^-1，容量衰减平均每次循环高达1.24 mAh·g^-1。TEM和EDS分析证明：由一次粒子团聚的类球形So-LiMnO₂能有效地抑制电解液对材料的腐蚀、减少Mn的溶解，从而提高了电化学循环能力。     

硅氧烷乳液聚合过程中大颗粒形成机理研究：Ⅰ.阳离子型乳液的耐电解质…

探讨了二甲基聚硅氧烷阳离子型乳液耐电解质稳定性的影响因素。结果表明，加入少量的非离子型表面活性剂与阳离子型乳化剂并用进行乳液聚合，可以保护乳液粒子，防止由于电解质引的乳液粒子的相互凝聚而形成大颗粒。     

Janus particles with a functional gold surface for control of surface plasmon resonance

We report in this study the presence of Janus particles, which are candidates for use with electronic color papers. We used negatively charged polystyrene particles (370 nm) as the core particles, and gold was then sputtered onto their packed monolayer under several conditions. The sputtered particles were next redispersed into the aqueous medium by gentle sonication. Gold nanoparticles localized on one side of the cores could also serve as seeds for subsequent shell growth by electroless gold plating. Through these treatments, a series of well-dispersed Janus particles were obtained with gold nanostructures of different size and shape only on one side. Their dispersions showed different colors originating from the surface plasmon resonance absorption of gold nanoparticles localized on the hemisphere. The particles obtained by this approach have potential applications such as in sensors and electronic color paper.     

Future of biological aerosol detection

Biological aerosol detection in real time is an urgent civilian and military requirement. Such detection capability will be useful in environmental monitoring, for example, in gathering information in perceived hazardous areas such as housing developments downwind of sewage treatment plants. To be truly functional, the instrument has to operate continuously, 24 h a day and 7 days a week with minimal maintenance and few false alarms. A novel concept is proposed. The system employs a rapid front-end warning/alarming mechanism based on optical technologies that provides useful information for protection decision makers. This is connected to a sample collector that feeds a slower back-end liquid chemistry system that provides analytical results to the medical personnel to assist in prophylaxis and therapy decisions. Experience gained from measuring fluorescence signals of single bacterial spores under flow cytometry (FCM) using UV excitation at 340-360 nm, was applied to concept testing of a prototype instrument, built to do the same for aerosols. This machine was capable of resolving particle size as well as fluorescence intensity of each particle under laboratory and field conditions; it was called the fluorescent aerodynamic particle sizer (FLAPS). This paper describes practical aspects of measuring biological aerosols when the results must be compared to reference samplers that provide culturable or “live” data. Treatment of particle size and fluorescence information is discussed with respect to FLAPS and reference data fidelity. Along with an objective method to evaluate FLAPS data correlation to reference data, an approach for determining limit of detection in the field is discussed. In addressing the back-end detector chemistry, we have prioritized a number of important biological characteristics that must be given to a clinician to help in prophylaxis and therapy decisions. A series of biochemical measurements are proposed to define the threat of a sample and different solutions are given to implement these tests. We predict that the future for biological detection looks promising for fluorescence in situ hybridization (FISH) techniques in identifying microorganisms. A conceptual instrument based on merging FCM and microchip-based analysis is described.     

Influence of the particle size distribution on the CRTA curves for the solid-state reactions of interface shrinkage type

The kinetic curves at infinite temperature for the solid-state reactions of the interface shrinkage type were drawn theoretically by taking account the particle size distribution in the sample mixture. The CRTA curves for the reactions with the particle size distribution can be drawn by utilizing the universal kinetic curves at infinite temperature. The proper kinetic treatment for the CRTA curves with the particle size distribution is discussed in connection with the property of the kinetic equation with respect to the particle size distribution. The present kinetic consideration is taken as a simulation for the reactions with a certain distribution in among the reactant particles, produced preferably by the mass and heat transfer phenomena during the thermoanalytical measurements. The merit of the rate jump method by a single cyclic CRTA curve is also discussed on the basis of the present results.     

SiO2/α-FeOOH和SiO2/γ-Fe2O3微粒的界面研究

α－FeOOH微粒由于其表面高活性，在转变成γ－Fe2O3的热处理过程中容易烧结，一旦这种烧结现象发生，得到的γ－Fe2O3磁粉磁性能大大下降[1]．为了克服这一困难，目前采用在α-FeOOH微粒表面包敷有机物[2]和无机物[3]来隔离颗粒，阻止其聚集．其中SiO2表面包敷处理是最令人感兴趣的研究课题之一[4，5]．SiO2是一种难烙性的非磁性材料，它包敷在α-FeOOH微粒表面外，不仅可提高α－FeOOH转变成γ－Fe2O3的热处理温度，有利于得到外形完好、晶格完整的γ－Fe2O3磁粉，而且由包效层与内核之间的界面相互作用引起的表面各向异性常…     

On the Hydrolytic Stability of Organic Ligands in Al-, Ti- and Zr-Alkoxide Complexes

The complexation degrees of Al-, Ti- and Zr-butoxide (M) with unsaturated and saturated -diketones (3-allylpentane-2.4-dione-APD, acetylacetone-ACAC) and -ketoesters (methacryloxyethyl-acetoacetate-MEAA, allylacetoacetate-AAA, ethylacetoacetate-EAA) as organic ligands (L) were examined by IR and ¹³ C NMR spectroscopy and were found to be L:M 1.5. The hydrolytic stability of the ligands of the metal alkoxide complexes (L:M = 1) during hydrolysis/condensation reactions at the molar ratio h (H₂O : OR) = 0.5–2.0 decreases with increasing H$$₂O:complex ratio. Furthermore, the ligand stability depends on the type of metal in the complexes and decreases in the order Al- > Zr- > Ti-butoxide complexes at h=1. The ACAC ligand likewise shows in the Al-, Ti- and Zr-butoxide complexes a high hydrolytic stability (95–100%) at h=1 within 7 days. The Ti- and Zr-butoxide complexes with -ketoesters as ligand show at h=1> a release to a different extent e.g., up to 60% in the case of the MEAA-ligand in the Ti-butoxide complex after 2 days. In general, the hydrolytic stability of the ligands in the Ti-butoxide complexes (L:M = 1, h=1) decreases in the order ACAC > APD > AAA > EAA MEAA. The hydrolysis/condensation reaction of complexes having a weak ligand stability leads to larger particle sizes in the sols than those with stable ACAC ligands. The results contribute to a more controlled synthesis of sols and of new inorganic-organic hybrid polymers via the sol-gel process.     

Thermocapillary Alignment of Gas Bubbles Induced by Convective Transport

The effect of a weak convective heat transfer on the thermocapillary interaction of two bubbles with an arbitrary orientation relative to an externally imposed temperature gradient is examined. Asymptotic analysis of the case of large separation distances, Z, suggests that the corrections to the bubbles' velocities are of (Pe/Z²), rather than (Pe²) previously found for an isolated bubble. Equal-sized bubbles are known to move with the same velocities, as if they were isolated, when heat conduction is the only transport mechanism. However, the convective transport results in a relative motion of the bubbles. The tendency of equal bubbles to line up in a plane perpendicular to the applied thermal gradient is shown analytically in the weakly nonlinear limit of small Pe numbers, and an interesting interaction behavior in the case of unequal bubbles is discussed.     

DIFFUSION OF LONG CHAINS THROUGH A POROUS THIN GEL NETWORK

Using a core(142 nm)made of linear polystyrene(PS)chains as a seed,we further polymerized a thin layer of cross-linked PS shell(7 nm)on it in water to form a core-shell particle.Such a particle swells in toluene,which enables linear PS chains inside the core to gradually diffuse out through the porous shell.Using a combination of static and dynamic laser light scattering,we examined the chain diffusion process by following the change of the scattering intensity(i.e.the average molar mass of the particles).For the first time,we have revealed that the diffusion exhibits three stages.In the first stage,the chain diffusion through the shell is even faster than their translational diffusion in a dilute solution.The three stages respectively correspond to the change of the solution in the core from concentrated to semidilute and then from semidilute to dilute.     

Template functions of particle monolayers on hydrophobic solid substrates

The template function of cationic particle monolayers bearing quaternary ammonium groups on their surfaces towards anionic colloids was investigated in this paper. Monodispersed cationic polymer particles having quaternary ammonium groups were self-organized on octadecylated glass plates through hydrophobic interaction. The morphology of the resulting particle monolayers was changed by tuning hydrophilic–hydrophobic balance of particles to fabricate aggregated type and dispersed type of particle monolayers. Gold and silver colloids were selectively deposited onto the particle monolayers through electrostatic interaction. The deposited gold and silver colloids on particle monolayers showed plasmon absorbance. Fluorescent silica colloids were also selectively deposited on particle monolayers to permit fluorescence labeling of the particle monolayers. Cationic particle monolayers fabricated on hydrophobic solid octadecylated were found to effectively work as templates for the deposition of above mentioned inorganic colloids.