Thermal Characterisation of Porous Silicon Membranes

Results of thermal characterisation based on the phase lag of photoacoustic signal for front-rear surface illumination of porous silicon and nitrided porous silicon membranes for gas sensing devices are presented. Thermal conductivity values in good agreement with literature values have been obtained, confirming the usefulness and reliability of photothermal methods in the investigation of new materials for sensors and microsystems. Preliminary results of stokes-antistokes Raman investigations are also reported.     

基于多孔硅及MEMS技术的微型质子交换膜燃料电池

分析了研究和发展微型质子交换膜燃料电池(μPEMFC)的重要意义和应用前景,介绍了基于多孔硅及MEMS技术的μPEMFC最新研究动态,讨论了μPEMFC的结构设计、加工过程及性能,提出了μPEMFC仍存在的问题及其技术发展对策。     

Structuring of Macroporous Silicon for Applications as Photonic Crystals

Uniformity and high refractive index contrast make macroporous silicon an ideal two-dimensional photonic crystal, that can be tailored over a wide range of frequencies. For optical transmission measurements the porous silicon has to be structured further. Light has to be coupled in perpendicular to the pore axis and to traverse a well defined number of pore layers. For this purpose a lateral structuring technique has been developed that allows to remove the porous silicon with a precision of less than one pore lattice constant. Bars of macroporous silicon which are 100 m high, 2–200 m wide and several mm long have been prepared. These bars have been aligned with designed defect structures like linear or bent waveguides in the porous silicon. The achieved samples are well suited to investigate the optical properties of these defects with light traveling perpendicular to the pore axis.     

多孔硅的形貌、制备和应用

介绍了近年来制备多孔硅的主要方法,以及多孔硅在光电传感器、发光器件、电池、生物技术等新领域的应用。     

SPE膜电极及其在反应器和传感器中的应用与发展

本文概述了固体高聚物电解质复合膜电极的制备技术和发展,重点介绍其在低温燃料电池,膜反应器和乙及氧传感器中的应用。     

室内环境苯浓度检测的不确定度分析

文章系统分析了热解吸直接进样气相色谱法检测室内空气中苯浓度的不确定度来源,对各不确定度分量进行了量化,提出该方法的合成不确定度。通过对各不确定度分量的分析得到,室内空气中苯浓度检测主要来源于苯标准气体浓度、苯标准曲线的拟合和整个实验的重复性,计时误差、温度和气压引入的不确定度基本可以忽略。     

活性硅醇改性PVC膜的研究

以廉价的水玻璃为原料,用酸化法从水玻璃中得到硅的有机化合物——活性硅醇,并将活性硅醇直接掺杂到PVC膜中。实验结果表明:用活性硅醇掺杂,流涎法制得的PVC膜,硅在PVC膜中的分布均匀,粒径在10μm以下;硅改性后的PVC膜耐热性有了较为明显的改善。活性硅醇改性PVC膜经NaOH浓溶液处理溶去其中的SiO_2粒子后,形成了具有均匀微小孔洞的膜。其孔径与SiO_2粒子的粒径相近。通过控制活性硅醇在PVC膜中的质量分数制备含有不同孔径的PVC膜。     

Novel Structures for Porous Silicon Light-Emitting Diodes

In this paper, two novel structures of porous silicon (PS) light-emitting diodes (LEDs) are proposed aiming at the reduction of series resistance, R_s. The basic idea of the novel structures is to suppress the excessive growth of nanoporous silicon (nano-PS) layer that is electroluminescence- (EL-) active but highly resistive. The initial wafer of the first structure consists of a lightly-doped layer stacked on a highly-doped substrate. As a consequence of anodization, nano-PS layer is formed only in the lightly-doped layer, while meso-PS layer with moderate resistivity is formed in the highly-doped substrate. The second structure consists of alternately stacked nano- and meso-PS layers, since it is expected that multiple thin nano-PS layers connected in series are less resistive than a single thick nano-PS layer. Preliminary experimental results proved the effectiveness of these novel structures on the reduction of R_s.     

介孔分子硅剂改善茶浓缩膜结构特性应用研究

为有效提高功能性茶浓缩反渗透膜的回收效率和抗污性能,探究了3种介孔分子硅材料(MCM-41、SBA-15和MCFs)对浓缩膜面聚酰胺层聚合形成过程的结构影响。结果表明,添加质量分数0.02%经磺化预处理的MCM-41于间苯二胺水相可接枝酰氯基团,形成的聚酰胺结构层峰谷粗糙跨度仅为220 nm且交联紧致,膜抗拉伸强度增加37.8%;SBA-15和MCFs相膜面峰谷跨度达500~780 nm,横向褶皱和团聚,结构存在孔道塌陷;改性膜在3 h内对茶多酚、茶多糖、茶蛋白即可达到最大浓缩度,减少50%浓缩时间;MCM-41和SBA-15膜长时间运行的浓缩降率仅为2.8%~6.1%,48 h下降率比显示改性膜达标使用时长增加112.5%~137.5%,亲水性和抗污堵能力均大幅提升,可有效满足功能化茶浓缩精度。     

A Flat Polymeric Membrane Sensor for Carbon Dioxide/Nitrogen Gas Mixture

A gas sensor was developed to measure the concentration of binary gas mixtures. This sensor works based on the permeability change of different gas mixtures across the polymeric membranes. Although high values of permeability and selectivity are needed for an ideal separation, the performance of this sensor mainly depends on the permeability factor. Polysulfone and silicone rubber were applied as the membrane base and coat, respectively. Moreover, in contrast to existing polymeric sensors that use hollow fibers, the present sensor is made of flat membranes. This new design is cheaper, smaller, and easier to use in comparison to the hollow fiber polymeric sensors. In order to test the sensor applicability, nitrogen and carbon dioxide were used as model gases. The effect of pressure on the response time and sensor accuracy was studied for the aforementioned gases. The response time (T_95%) of this low price sensor was 50?s, and the tolerance of measuring concentration was approximately 1.4% at 2?bar feed pressure. Also, increasing the feed pressure can improve the response time or accuracy of the sensor.     

碳化硅多孔陶瓷的制备工艺比较

多孔碳化硅陶瓷由于具有优良的高温强度、耐磨性、耐腐蚀性以及抗热震性而得到越来越广泛的关注.随着科技的发展,其已在环境保护、过滤分离、尾气吸收、吸声降噪、生物医学、航空航天和能源化工等方面发挥着重要的作用.本文着重分析了多孔碳化硅陶瓷的传统制备工艺与先进制备工艺的优缺点,并对其未来的制备工艺作出展望.     

Separation of Water and Nitric Acid with Porous Hydrophobic Membrane by Air Gap Membrane Distillation (AGMD)

Abstract

This study investigates the effect of operation parameters on the separation of nitric acid‐water mixture using air gap membrane distillation (AGMD). Porous hydrophobic PTFE membrane was used. The performance was evaluated based on the permeate flux and the nitric acid selectivity. Operating parameters such as feed solution temperature, feed concentration, flow rate, and air gap width were varied. Nitric acid selectivity was found to increase with the increase in feed solution temperature, feed concentration, flow rate, and air gap width. Permeate flux increased, when the feed temperature and the flow rate were increased. The effect of recirculation of the feed solution was also studied. With the recirculation mode, at different initial solution volumes, it was observed that the nitric acid concentration in the feed and the permeate, increased. The rate of flux decline was greater, when the initial feed solution volume was lower.     

硅橡胶复合膜渗透蒸发串联阻力扩展模型研究

介绍了国内外硅橡胶复合膜渗透蒸发脱除微量有机物的传质研究现状;提出了硅橡胶复合膜渗透蒸发串联传质阻力扩展模型;分析了渗透蒸发过程各部分传质阻力的影响因素,包括液相边界层、膜的致密皮层、膜的多孔支撑层;得到了便于工程设计的计算方法。结果表明,该模型对进一步的应用研究以及渗透蒸发过程的优化具有指导意义。     

多孔二氧化硅对酸性橙吸附性能的研究

以水玻璃和盐酸为原料,采用化学沉淀法制备出多孔、高比表面积的SiO2。改变灼烧温度,得到不同灼烧温度下SiO2对酸性橙的吸附曲线,找出了最佳灼烧温度。在此温度下制备出SiO2并对一定浓度的酸性橙溶液进行"吸附-灼烧-吸附"的反复吸收试验。实验结果表明400℃灼烧的SiO2的吸附性最好,并且随着循环次数的增多吸附能力慢慢下降。     

Studies of Air Slug Distributions and Preliminary Membrane Fouling by Optical Monitoring in a Side-Stream Membrane Module

Abstract

This article is aimed to propose an alternative method to characterize an air/water flow and new designs of rotating air distributors for membrane fouling control in a side-stream membrane module for a membrane bioreactor. A new optical sensor technique was experimentally demonstrated for the characterization of slug flows in a tubular ultrafiltration membrane module. The experimental results showed that the optical sensor system had high sensitivities for measurements of slug velocities, lengths, and frequencies in each membrane tube. The phenomena of slug coalescence/spilt were discussed. The rotating air distributor significantly improved the air slug distributions and had the potential to reduce the membrane fouling.     

Electronic Structure and PL Spectrum of the Diffusion-Limited Model for Porous Silicon

We present the results of theoretical calculations for electronic structures and photoluminescence (PL) spectrum of porous silicon whose morphology is generated through the diffusion limited aggregation process of pores in a two-dimensional honeycomb lattice. We have found that due to irregularity of the structure most of its eigenstates near band gap are localized while some of them are relatively delocalized. The localization of the eigenstates near band gap causes band-gap narrowing analogous to the quantum confinement effect. Solving the time-dependent equations for the occupation numbers of the eigenstates, we show that the present model reproduces the stretched exponential decay of PL intensity observed in the experiments.     

多孔陶瓷膜反应器用于非均相超细纳米催化的研究进展(英文)

Heterogeneous catalysts with ultrafine or nano particle size have currently attracted considerable attentions in the chemical and petrochemical production processes, but their large-scale applications remain challenging because of difficulties associated with their efficient separation from the reaction slurry. A porous ceramic membrane reactor has emerged as a promising method to solve the problem concerning catalysts separation in situ from the reaction mixture and make the production process continuous in heterogeneous catalysis. This article presents a review of the present progress on porous ceramic membrane reactors for heterogeneous catalysis, which covers classification of configurations of porous ceramic membrane reactor, major considerations and some important industrial applications. A special emphasis is paid to major considerations in term of application-oriented ceramic membrane design, optimization of ceramic membrane reactor performance and membrane fouling mechanism. Finally, brief concluding remarks on porous ceramic membrane reactors are given and possible future research interests are also outlined.     

Chemically Cross-linked Polysilanes as Stable Polymer Precursors for Conversion to Silicon Carbide

Cross-linked polysilanes were prepared by the co-polymerization of Me₂SiCl₂ or PhMeSiCl₂ with varying amounts of divinylbenzene (2–15% by weight) using molten sodium as the dehalogenating agent. All the cross-linked polysilanes were stable to air and could be processed thermally for conversion to silicon carbide. Polymers containing from 5–15% of the cross-linking agent underwent a uniform shrinkage during thermal treatment (1500 °C) to afford β-SiC in good yields. The ceramic was characterized by a variety of techniques including Raman and infrared spectroscopy, powder XRD, as well as Scanning Electron Microscopy (SEM). Dedicated to Prof. C. W. Allen in recognition of his outstanding contributions to inorganic polymers. Deceased in a tragic car accident in July 2004.     

硅纳米线阵列电极作为细胞色素c传感器的研究

利用化学刻蚀法由p型硅片制备了硅纳米线阵列,经过表面去氧化层处理后,制备了检测蛋白质细胞色素c的电化学传感器.实验表明,硅纳米线阵列电极对细胞色素c有良好的电化学响应,并且在低浓度条件下具备线性响应的特点.根据与未经表面处理的硅纳米线阵列电极的实验结果相对比,提出了细胞色素c所具备的羧基末端与硅纳米线阵列电极表面的Si-H相互作用从而改善传感性能的检测机理.     

Fabrication of a Highly Sensitive Stretchable Strain Sensor Utilizing a Microfibrous Membrane and a Cracking Structure on Conducting Polymer

Recently, the detection of human motion has attracted considerable attention for the development of smart healthcare systems. Flexible or stretchable strain sensors are required to measure deformations on arbitrarily shaped human skin areas caused by human motion, and numerous studies have explored the development of such sensors. Here, a highly sensitive stretchable strain sensor is introduced, which consists of elastic fibrous membrane coated with conducting polymer. The membrane can be utilized to detect applied strain by measuring the conductance change caused by the change in the nanocracking structure on the coated conducting polymer layer. Furthermore, by collecting aligned microfibers as the fibrous membrane during electrospinning process, the sensor exhibits higher sensitivity (more than 40‐fold higher than the nonaligned version). Although limitations still remain in the repeatability and the applicability of the sensor, the developed sensor will demonstrate great potential for measuring applied strain and stress over a wide sensing range with high sensitivity is expected.