Water-soluble and amphiphilic polymers

Summary Three PEO-PSt-PEO triblock polymers and their parent ho-nopolystyrene have been studied by means of light scattering technique in chloroform, toluene and ethyl acetate. It has been found that the weight average molecular weights calculated by using the equation Mapp- were unbelievable negative values; and the largest deviation appeared for the sample with PEO mole content of about 50%. Data of PSt-PEO-PSt triblock polymers in literature have been quoted and discussed.     

Microstructure and Microchemistry of Polymer-Derived Crystalline SiC Fibers

Stoichiometric and near-stoichiometric silicon carbide fibers, derived from the polymer polycarbosilane, have been characterized by scanning Auger and transmission electron microscope techniques. Excess carbon usually appeared in the fibers, but it could be eliminated by controlling processing conditions. The fibers consisted mainly of submicrometer-sized SiC microcrystals, with a considerably twinned and stacking-faulted β-SiC structure. Free carbon, which appeared in the form of graphite, was the only detectable intergranular phase in the nonstoichioinetric SiC fibers, while the stoichiometric SiC fibers contained no detectable second phase whatsoever.     

基于Jpcap的Webmail邮件还原技术

基于Smtp和Pop3的邮件还原技术已经日臻成熟,而由于主要Webmail邮件格式不同,Webmail邮件还原技术一直是难点。通过对主要Webmail的内容格式分析,针对不同网站的Webmail建立相应的还原模块,实现对主要Webmail的内容还原。实验结果验证了该技术的有效性。     

The determination of the pore structural parameters of isoporous resins by inverse GPC

The swollen pore structure of a series of microporous isoporous resins (7.4–140 Å) are investigated with inverse GPC, n-alkylbenzenes and linear polystyrenes being used as probe molecules. The results indicated that, with the lowering of crosslinking degree of isoporous resins, the average pore diameter increased and the pore distribution curve broadened. All pore volume distribution obeyed a log-normal distribution. Based on the linear regression method, the experimental data were fitted to a monotonously declining exponential function and a normal distribution function by a computer, and some important structural parameters such as average pore diameter, pore volume distribution, specific surface area, etc. were obtained. The specific surface area of swollen gels were found much greater than those in the dry state measured by N₂ adsorption.     

Formation Mechanisms of Platelet Sr3Ti2O7 Crystals Synthesized by the Molten Salt Synthesis Method

The molten salt synthesis (MSS) method is utilized to synthesize the anisotropic platelet Sr₃Ti₂O₇ (S3T2) single-crystal particles. The aim of this study is to identify the essence of platelet Sr₃Ti₂O₇ crystal growth and guide the synthesis of anisotropic platelet SrTiO₃ crystals as well as various technologically important materials. Based on the results of X-ray diffraction, scanning electron microscopy, and high-resolution transmission electron microscopy, the formation mechanism of platelet Sr₃Ti₂O₇ crystals conforms to a nucleation–structure rearrangement–dissolution–diffusion in situ epitaxial growth mechanism model. First, SrCO₃ reacts with TiO₂ to form submicrometer SrTiO₃ nuclei. Then, most of the nuclei surrounded by salt ions aggregate and rearrange to form a large SrTiO₃ matrix. The structural rearrangement and the subsequent in situ epitaxial growth processes control the morphology, composition, and size of the final Sr₃Ti₂O₇ crystals. In the synthesis process, the conversion between SrTiO₃ and Sr₃Ti₂O₇ is as follows: and the crystallographic orientation relationship between Sr₃Ti₂O₇ and SrTiO₃ in the interface is (100)_S3T2//{100}_ST, (010)_S3T2//{010}_ST, and (001)_S3T2//{001}_ST.     

Preparation,characterization, and adsorption properties for metal ions of a novel chelating resin containing sulfoxide and diethylene glycol

A novel chelating resin containing sulfoxide and diethylene glycol, poly{4‐vinylbenzyl‐[2‐2‐(hydroxyethyl)ethoxyl]sulfoxide} (PVESO) was synthesized using chloromethylated polystyrene (PS‐Cl) as material. Its structure was characterized by elemental analysis, infrared spectra, and scanning electron microscopy (SEM). The adsorption capacities of the resin for Hg²⁺, Ag⁺, Cu²⁺, Zn²⁺, and Pb²⁺ at various pH values were determined. The maximum adsorption capacities for Hg²⁺ and Ag⁺ were 1.56 and 0.75 mmol g^?1 respectively. The resin had high selectivity for Hg²⁺ and Ag⁺ over the pH range 1.0–7.0. The adsorption capacities for Hg²⁺ and Ag⁺ under competitive condition were also determined by batch experiment method. In addition, the adsorption kinetics of the resin towards Hg²⁺ at different temperatures was also investigated. The results showed that the adsorption rate was governed by film diffusion at 20°C and 25°C, by particle diffusion at 30°C and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6054–6059, 2006     

冷却器盘管失效分析及防范措施

本文介绍了冷却器盘管破裂泄漏的情况，分析了失效破坏的原因，并提出防止冷却器盘管破裂泄漏的措施。     

T.C.Powcrs模型若干问题的研究

从T.C.Powers水泥石模型出发,提出了描述水泥混凝土材料初始结构的主要参数是初始孔隙率。由此池绎了水泥浆体组成与结构的定量关系,比原模型有更明了的物理意义,研究结果表明,Powers模型在高孔隙率范围内具有适用性,但不适用于低孔隙率硬化水泥浆体,且在低孔隙率条件下不存在28％的固有凝胶孔隙率,水化产物成份和性质是渐变的。