The Formation of Porous Membranes by Filtration of Aerosol Nanoparticles

Flame-generated aerosol particles of Al₂O₃ were deposited by gas filtration on two types of porous and ceramic tubes of -Al₂O₃ with mean pore diameters of 450 and 2700nm, respectively. The particles were aggregates with average mobility diameters in the range of 30–100nm and primary particle diameters of 4–8nm. The particles are characterized by differential mobility analysis, transmission electron microscopy, and by their specific surface area. The deposited membranes are characterized by gas permeability measurements, scanning electron microscopy, and by their pore size distribution from nitrogen capillary condensation. The particles form a distinct, homogeneous membrane layer with a porosity of 90% on top of the substrate surface and only penetrate slightly into the substrate structure. The mean pore sizes of the deposited membranes determined by nitrogen condensation agree approximately with those determined by gas permeation and the specific surface area. The mean pore diameter varies in the range of 30–70nm. The gas permeability of the deposited membranes is related to the specific surface area but influenced by the high porosity. The mean pore size and the permeability of the membranes are almost independent of the substrate structure.The development of a membrane with uniform properties is preceded by a short initial period in which the deposited particles, with an equivalent membrane thickness of roughly 2m, have a significantly lower permeability than the ultimately developed uniform membrane layer. This effect is particularly significant for the aerosol particles with the lowest mean size, probably due to particles deposited in the pore mouths of the substrate.The particles and the deposited membranes are X-ray amorphous but retain their specific surface area on heating to even high temperatures. When the membranes are heated to 1473K for 10h, X-ray diffraction shows a mixture of - and -alumina, accompanied by a partial disintegration of the membrane and a considerable loss of surface area.     

贮存条件对纤维素/大豆蛋白膜结构与性能的影响

通过流延成膜法制备一系列纤维素/大豆分离蛋白复合膜材料,分别以10%醋酸溶液、5%醋酸和5%乙醇的混合溶液、75%乙醇溶液等3种水溶液及蒸馏水为贮存体系,通过力学性能测试、扫描电镜观察、紫外测试等方法研究了不同贮存条件对纤维素/大豆分离蛋白复合膜结构与性能的影响.结果表明,10%醋酸水溶液贮存纤维素/大豆分离蛋白复合膜30d能够较好地维持其力学性能和微观结构,可作为该复合膜较为适合的贮存体系.     

相变过程的格子Boltzmann方法模拟

应用Shan提出的伪势多相模型替代R-K着色模型,建立一种新的描述气液相变过程的格子Boltzmann理论模型,模拟蒸发(高密度转化为低密度)过程.改进了计算效率,且得到较好的计算结果.同时应用该模型从孔隙尺度模拟了多孔介质中的相变现象,验证了该模型模拟复杂相变问题的可行性.     

分形多孔介质的粒子扩散特点(Ⅱ)

本文进一步讨论了粒子在分形结构中的扩散,首先计算测定了各分形结构的谱维数,然后对其布朗运动特点进 行了分析讨论,最后模拟得到了粒子扩散概率分布,它们表现出很多有趣的特征:不均匀性,内含空洞和标度性等.这些 结果可以更好地了解气体在分形结构中的扩散。     

Luminescence and scintillation of Eu2+‐doped high silica glass

High silica glass doped with Eu²⁺ ions was prepared as a scintillating material by impregnation of Eu ions into a porous silica glass followed by reduction sintering in CO atmosphere. A dominant emission band of the Eu²⁺ 5d–4f transition peaking around 430 nm was observed in the luminescence spectrum with the excitation peak around 280 nm and no emission from Eu³⁺ was present. Photoluminescence decay kinetics was governed by decay times of a few microseconds. The Eu²⁺‐doped high silica glass exhibited comparable energy resolution and slightly higher photoelectron yield with respect to the Bi₄Ge₃O₁₂ crystal in the pulse height spectra for X‐ray photon energies within 22–60 keV. Furthermore, a factor of 1.2 higher radioluminescence intensity was observed as well. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Monitoring membrane rafts in colorectal cancer cells by means of correlative fluorescence electron microscopy (CFEM)

Detergent-resistant membrane (DRM) rafts have been shown to play a pivotal role in regulating key cell biological processes, such as signal transduction, cellular transport and cell survival. The fine structure of membrane rafts are studied using various different imaging approaches and the outcomes are largely dependent on the detection methodology applied. All these microscopy techniques which employ light-, laser- and photon-optics, electrons as well as atomic force probing are characterized on their turn by their strengths and limitations for membrane raft identification. This explains in part the diversity of definitions available to describe these peculiar membrane structures. We present herewith an alternative and uncomplicated microscopy tool to study fluorescently labelled DRMs with information at the transmission electron microscopical level of the same cell, enabling us to obtain a snapshot of the morpho-functional relationships between the cell's interior and DRMs. The proposed approach of correlative fluorescence electron microscopy (CFEM) can therefore be considered as an additional alternative imaging approach to unravel DRM structure–function relationships from micro- to nanometre length scales, from the cell to the molecule.     

多孔阳极氧化铝膜形成机理的研究

为了探讨多孔阳极氧化铝膜的形成机理,在0．3mol／L的草酸溶液中,通过二次阳极氧化法制备了多孔氧化铝膜．X射线衍射和扫描电镜测量表明,本实验制备了高度有序的、非晶态结构的多孔氧化铝膜．通过分析阳极氧化过程中的电解电流随时间变化的关系,研究了多孔氧化铝膜的形成机理．     

制备工艺对多孔阳极氧化铝特性的影响

通过对草酸溶液中制备的多孔阳极氧化铝(PAA)的形貌、晶态结构和光致发光(PL)特性的表征和机理分析,研究了草酸电解液浓度、阳极氧化电压和退火等丁艺对PAA的形成及特性的影响.PAA的孔径在50～120 nm之间,且随着阳极氧化电压的升高而增大,而受电解液浓度的影响较小.X射线衍射结果表明:PAA为非晶态结构,退火之后结晶,并有多相共存.PL测试表明PAA在375～500 nm之间有一较宽的蓝色发光带,发光峰在425 nm左右,是由氧空位引起的,且其峰强可通过改变阳极氧化电压和草酸浓度等参数来调制.     

多孔介质中基质和微生物耦合输运问题的三次样条分析

本文用三次样条和全隐式逐次迭代方法,对描述多孔介质中基质-微生物耦合输运微分方程组进行数值计算,结果表明:数值求解这种具一定对流优势的非线性扩散方程,该计算方案是可行的,且获得了良好的结果。通过数值分析,对微生物在多孔介质中的传输行为有了个大概的了解,还探明了各参数对耦合系统的影响作用。     

A Scanning Electron Microscopy study of water in soil

Cold stage Scanning Electron Microscopy (SEM) with a rapid cooling technique makes it possible to investigate the water phase within unsaturated porous media. It is thought that this technique preserves the main features of the micromorphology of the water menisci as it exists in the liquid phase in soils. Saddle-shaped elements, as well as pendular rings of water, were observed with concave and convex curvatures of the water-air interface. The hydraulic conductivity of an unsaturated soil may be inferred from SEM photographs. Observations of isolated water menisci indicate the existence of an immobile water domain. The surface geometry of the water menisci was analyzed quantitatively and surface tension and capillary pressure were determined.