Fabrication of uniform porous alumina materials by radio frequency (RF) magnetron sputtering

Fabrication of porous materials with uniform pore size distribution remains a challenge. In this paper, a kind of uniform porous alumina material was fabricated on a template of polystyrene microspheres by radio frequency (RF) magnetron sputtering. Surface of samples was observed by scanning electron microscopy (SEM), and the phase of porous materials was confirmed by X-ray diffraction (XRD). The pore size distribution of samples was tested by mercury intrusion method.     

Geometry of random sequential adsorption

By sequentially adding line segments to a line or disks to a surface at random positions without overlaps, we obtain configurations of the one- and two-dimensional random sequential adsorption (RSA) problem. We have simulated the one- and two-dimensional problem with periodic boundary condition. The one-dimensional simulations are compared with the exact analytical solutions to give an estimate of the accuracy of the simulation. In two dimensions the geometrical properties of the RSA configuration are discussed and in addition known results of the RSA process are reproduced. Various statistical distributions of the Voronoi-Dirichlet (VD) network corresponding to the RSA disk configuration are analyzed. In order to characterize pores in the RSA configuration, we introduce circular holes. There is a direct correspondence between vertices of the VD network and these holes, and also between direct/indirect geometrical neighbors and these holes. The hole size distribution is found to be a parabola. We also find general relations that connect the asymptotic behavior of the surface coverage, the correlation function, and the hole size distribution.     

Effects of fiber diameter and CO2 activation temperature on the pore characteristics of polyacrylonitrile based activated carbon nanofibers

The effects of fiber diameter and activation temperature on the pore characteristics of polyacrylonitrile based activated carbon nanofibers are investigated. It was found that lower fiber diameters as well as higher activation temperatures lead to a higher weight loss, specific surface area and total pore volume. The nitrogen adsorption capacity of activated carbon nanofibers is almost three times that of activated carbon fiber with a diameter of 10 µm. As far as the size of pores in activated carbon nanofibers is concerned, it is basically the micropores that dominate the scene. Moreover, tailoring the pore characteristics by adjusting the activation temperature and fiber diameter is plausible. Copyright © 2009 John Wiley & Sons, Ltd.     

黑龙江省的界河坍塌地质灾害及其防治对策

界河坍塌是黑龙江省特殊的、主要的地质灾害,也是当前亟待解决的问题。本文总结了黑龙江省的两条主要界河—黑龙江和乌苏里江的塌岸状况;说明了界河坍塌的分布规律;论证了界河坍塌的形态类型;探讨了界河坍塌的形成机制;分析了界河坍塌的原因;最后提出了防止界河坍塌的一系列对策。     

Percolation theory approach to transport phenomena in porous media

The percolation theory approach to static and dynamic properties of the single- and two-phase fluid flow in porous media is described. Using percolation cluster scaling laws, one can obtain functional relations between the saturation fraction of a given phase and the capillary pressure, the relative permeability, and the dispersion coefficient, in drainage and imbibition processes. In addition, the scale dependency of the transport coefficient is shown to be an outcome of the fractal nature of pore space and of the random flow pattern of the fluids or contaminant.     

高温下煤焦的碳微晶及孔结构的演变行为

以贵州煤为原料,在热解温度950℃~1400℃制备了各种慢速和快速热解焦,主要对高温热解过程中煤焦的碳微晶和孔结构的演变行为进行了研究,同时也研究了高温气化过程中煤焦的孔结构变化规律。结果表明,慢速热解焦和快速热解焦的C和H含量明显不同;随热解温度的升高,煤焦的碳微晶结构向有序化方向发展,但慢速热解煤焦比快速热解煤焦的"石墨化"程度大;快速热解煤焦的微孔比表面积和微孔容积明显高于慢速热解煤焦,即快速热解煤焦的孔隙结构明显比慢速热解煤焦发达;在气化反应初期,煤焦的微孔比表面积下降,微中孔比表面积增加,反应后期煤焦的总比表面积快速下降。     

Strategies for the on-line preconcentration and separation of hypolipidaemic drugs using micellar electrokinetic chromatography

Three strategies were investigated for the simultaneous separation and on-line preconcentration of charged and neutral hypolipidaemic drugs in micellar electrokinetic chromatography (MEKC). A background electrolyte (BGE) consisting of 20 mM ammonium bicarbonate buffer (pH 8.50) and 50 mM sodium dodecyl sulfate (SDS) was used for the separation and on-line preconcentration of the drugs. The efficiencies of sweeping, analyte focusing by micelle collapse (AFMC), and simultaneous field-amplified sample stacking (FASS) and sweeping, were compared for the preconcentration of eight hypolipidaemic drugs in different conductivity sample matrices. When compared with a hydrodynamic injection (5 s at 50 mbar, 0.51% of capillary volume to detection window) of drug mixture prepared in the separation BGE, improvements of detection sensitivity of 60-, 83-, and 80-fold were obtained with sweeping, AFMC and simultaneous FASS and sweeping, respectively, giving limits of detection (LODs) of 50, 36, and 38 μg/L, respectively. The studied techniques showed suitability for focusing different types of analytes having different values of retention factor (k). This is the first report for the separation of different types of hypolipidaemic drugs by capillary electrophoresis (CE). The three methods were validated then applied for the analysis of target analytes in wastewater samples from Hobart city.     

Fructose-selective calorimetric biosensor in flow injection analysis

A highly selective, interference free biosensor for the measurement of fructose in real syrup samples was developed. The assay is based on the phosphorylation of d(−)fructose to fructose-6-phosphate by hexokinase and subsequent conversion of fructose-6-phosphate to fructose-1,6-biphosphate by fructose-6-phosphate-kinase. The heat liberated in the second reaction is monitored using an enzyme thermistor. The major advantages of this biosensor are rapid and selective measurement of fructose without the need to eliminate glucose and inexpensive FIA-based, mediator-free calorimetric measurement suitable for regular fructose analysis. This method was optimised for parameters, such as pH, ionic strength, interference, operational stability and shelf life. Good and reproducible linearity (0.5-6.0 mM) with a detection limit of 0.12 mM was obtained. Fructose determination in commercial syrup samples and spiked samples confirmed the reliability of this set-up and technique. The biosensor gave reproducible results with good overall stability for continuous measurements over a period of three months besides a useful shelf life of six months. The method could be used for routine fructose monitoring in food samples.     

调控介孔硅分子筛的孔壁结构以提高吸附亚硝胺的效率

 针对高空速下捕获痕量毒物分子的环境净化要求, 尝试调控介孔材料孔壁结构以提高其吸附小分子环境污染物的效率. 通过调节合成体系的 pH 值、加入无机盐以及控制表面活性剂浓度等方法, 改变硅物种与模板剂胶束的组装速度或无机-有机液晶相的存在形态, 研制含有孔壁缺陷位的介孔分子筛新材料. 通过 X 射线衍射和低温氮气吸附研究了样品的结构特性, 并采用高分辨透射电镜和固体核磁技术证实了介孔材料孔壁缺陷位的形成. 以挥发性吡咯烷亚硝胺为靶标分子, 考察了所得材料的吸附性能. 结果表明, 大量缺陷空位的存在成倍地提高了介孔分子筛吸附挥发性亚硝胺的效率, 为设计研制环保新材料提供了新思路.     

冲击作用下HMX晶体孔洞塌缩热点生成机制的细观数值模拟

热点的形成、点火以及成长过程是理解非均匀炸药冲击起爆的关键.采用离散元法,对冲击作用下含孔洞的HMX晶体进行了细观数值模拟.计算结果表明:在较低冲击作用下,孔洞边缘发生了较大的剪切变形,粘塑性功形成热点;而在较高冲击作用下,孔洞塌缩产生射流,汇聚流动,冲击下游炸药形成热点,并获得了孔洞塌缩和热点生成演化的细观过程.