Crack Patterns in Ceramic Plates after Quenching

The crack patterns generated in a real ceramic plate and in a plate stacked by ceramic slabs under quenching are experimentally studied. The results here reveal that there are some distinct differences between the two crack patterns. The reasons that caused the differences are the size and boundary effects of the slabs. These crack patterns are very useful to understand the failure mechanisms of ceramic materials in thermal shock.

Universal Biot number determining stress duration and susceptibility of ceramic cylinders to quenching

A universal Biot number, which not only describes the susceptibility of ceramic cylinders to quenching but also determines the duration that ceramic cylinders are subjected to thermal stress during thermal shock, is theoretically obtained. The analysis proves that thermal shock failure of ceramic cylinders with a Biot number greater than the critical value is a rapid process, which only occurs in the initial heat conduction regime. The results provide a guide to the selection of ceramic materials for thermostructural engineering, with particular reference to thermal shock.

Preparation of silver nanowires in ion-track membranes

Polycarbonate (PC) membranes were irradiated with swift heavy ions and latent tracks were created along the ions' trajectories. Nanopores, diameters between 100 and 500 nm, were obtained after illuminating the membranes with UV light and etching in NaOH solution. Silver nanowires were produced in the etched ion-track membranes by electrochemical deposition. The morphology and crystallinity of the silver nanowires were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). Under certain conditions (deposition voltage 25 mV, current density 1-2 mA.cm(-2), temperature 50 degrees C, electrolyte 0.1 mol.L-1 AgNO3), single-crystalline silver nanowires with preferred orientation along the [111] direction can be synthesized.

Preparation of Microporous Membranes by Swift Heavy Ion Irradiation and Impedance Characterization

Polypropylene (PP) microporous membranes were successfully prepared by swift heavy ion irradiation and track-etching. Polypropylene foils were irradiated with Au-197 ions of kinetic energy 11.4 MeV.u(-1) (total energy of 2245.8 MeV) and fluence 1x10(8) ions.cm(-2) at normal incidence. The damaged regions produced by the gold ions along the trajectories were etched in H2SO4 and K2Cr2O7 solutions leading to the formation of cylindrical pores in the membranes. The pore diameters of the PP microporous membranes increased from 380 to 1610 nm as the etching time increased from 5 to 30 min. The surface and cross-section morphologies of the porous membranes were characterized by scanning electron microscopy (SEM). The micropores in the membranes were found to be cylindrical in shape, homogeneous in distribution, and equal in size. Some mathematical relations of the porosity of the PP microporous membranes were established by analytic derivation. The microporous membranes were used in lithium-ion batteries to measure their properties as separators. The electrical conductivity of the porous membrane immersed in liquid electrolyte was found to be comparable to that of commercial separators by electrochemical impedance spectroscopy (EIS). The results showed that the porosity and electrical conductivity were dependent on the ion fluence and etching time. By adjusting these two factors, microporous membranes with good porosity and electrical conductivity were made that met the requirements for commercial use.

重离子辐照制备电池用微孔膜及其阻抗性质；Preparation of Microporous Membranes by Swift Heavy Ion Irradiation and Impedance Characterization

利用离子辐照结合径迹蚀刻方法制备聚丙烯(PP)微孔膜.用加速器产生的单核能为11.4MeV·u-1(总能量2245.8MeV)的197Au离子束辐照PP膜,剂量为1×108ions·cm-2.辐照后PP膜沿离子路径产生损伤区域,用硫酸与重铬酸钾的混合液进行蚀刻(5-30min),制备出孔径为380-1610nm的聚丙烯微孔膜.对膜的表面和断面形貌进行表征,微孔膜的孔径大小及空间分布均匀,孔道上下贯通,形状近似为圆柱形.给出了微孔膜的孔隙率理论公式.将制备的聚丙烯微孔膜用作锂离子电池隔膜,用电化学阻抗谱(EIS)测定浸满电解液的微孔膜的离子电导率,并与商用隔膜进行比较.分析表明辐照剂量和孔径大小均会影响膜的孔隙率和离子电导率,选择合适的辐照剂量和蚀刻时间,可以制备出孔隙率和离子电导率符合应用标准的聚丙烯微孔膜.

Preparation and performance of cellulose acetate/polyethyleneimine blend microfiltration membranes and their applications

A modified microfiltration membrane has been prepared by blending a matrix polymer with a functional polymer. Cellulose acetate (CA) was blended with polyethyleneimine (PEI), which was then crosslinked by polyisocyanate, in a mixture of solvents. In the membrane, PEI can supply coupling sites for ligands in affinity separation or be used as ligands for metal chelating, removal of endotoxin or ion exchange. The effects of the time of phase inversion induced by water vapor, blended amount of PEI and amount of crosslinking agent on membrane performance were investigated. The prepared blend membranes have specific surface area of 12.04-24.11 m(2)/g and pure water flux (PWF) of 10-50 ml/cm(2) min with porosity of 63-75%. The membranes, made of 0.15 50 wt.% PEI/CA ratio and 0.5 crosslinking agent/PEI ratio, were applied to adsorbing Cu2+ and bovine serum albumin (BSA) individually. The maximum adsorption capacity of Cu2+ ion on the blend membrane is 7.42 mg/g dry membrane. The maximum adsorption capacities of BSA on the membranes with and without chelating Cu2+ ion are 86.6 and 43.8 mg/g dry membrane, respectively. (C) 2004 Elsevier B.V. All rights reserved.

Methanol synthesis from CO2 using a silicone rubber/ceramic composite membrane reactor

A one-dimensional isothermal pseudo-homogeneous parallel flow model was developed for the methanol synthesis from CO2 in a silicone rubber/ceramic composite membrane reactor. The fourth-order Runge-Kutta method was adopted to simulate the process behaviors in the membrane reactor. How those parameters affect the reaction behaviors in the membrane reactor, such as Damkohler number Da, pressure ratio p(r), reaction temperature T, membrane separation factor alpha, membrane permeation parameter phi , as well as the non-uniform parameter of membrane permeation L-1, were discussed in detail. Parts of the theoretical results were tested and verified; the experimental results showed that the conversion of the main reaction in the membrane reactor increased by 22% against traditional fixed bed reactor, and the optimal non-uniform parameter of membrane permeation rate, L-1.opt ,does exist. (C) 2003 Elsevier B.V All rights reserved.

Enlarged area A-type zeolite membranes prepared by vacuum seeding method

High quality A-type zeolite membranes, with enlarged area over 70 cm(2), were successfully synthesized on a tubular alpha-Al2O3 support by applying the vacuum seeding method.

Gas permeation performance of cellulose hollow fiber membranes made from the cellulose/N-methylmorpholine-N-oxide/H2O system

Cellulose hollow fiber membranes (CHFM) were prepared using a spinning solution containing N-methylmorpholine-N-oxide as solvent and water as a nonsolvent additive. Water was also used as both the internal and external coagulant. It was demonstrated that the phase separation mechanism of this system was delayed demixing. The CHFM was revealed to be homogeneously dense structure after desiccation. The gas permeation properties of CO2, N-2, CH4, and H-2 through CHFM were investigated as a function of membrane water content and operation pressure. The water content of CHFM had crucial influence on gas permeation performance, and the permeation rates of all gases increased sharply with the increase of membrane water content. The permeation rate of CO2 increased with the increase of operation pressure, which has no significant effect on N-2, H-2, and CH4. At the end of this article a detailed comparison of gas permeation performance and mechanism between the CHFM and cellulose acetate flat membrane was given. (C) 2003 Wiley Periodicals, Inc.

Preparation of A-type zeolite membranes on nonporous metal supports by using electrophoretic technique

A-type zeolite membranes were prepared on the nonporous metal supports by using electrophoretic technique. The as-synthesized membranes were characterized by XRD and SEM. The effect of the applied potential on the formation of the A-type zeolite membrane was investigated, and the formation mechanism of zeolite membrane in the electric field was discussed. The results showed that the negative charged zeolite particles could migrate to the anode metal surface homogenously and rapidly under the action of the applied electric field, consequently formed uniform and dense membranes in short time. The applied potential had great effect on the membrane formation, and more uniform and denser zeolite membranes were prepared on the nonporous metal supports with 1 V potential.