微凝胶模板法制备PNIPAM/PbS有机-无机复合微球

采用反相乳液聚合方法合成了包埋有Pb2+的PNIPAM微凝胶,利用微凝胶的限域和导向作用,通过外源沉积法制备了PNIPAM/PbS有机 无机结构型复合微球.采用扫描电镜(SEM)、X射线衍射分析和热重分析对复合微球的形貌、无机沉积物PbS的晶型和相对含量等进行了表征.结果表明,高分子微凝胶的三维网络结构和所采用的制备方法确保了有机 无机复合材料复合的均匀性;微凝胶的模板作用使得复合材料呈现球状结构,微球的大小决定于模板的尺寸;复合微球中PbS具有面心立方结构;复合微球中无机物含量约为10%.实验所得PNIPAM/PbS复合微球明显兼有无机物的刚性和有机物的柔性.

高弹性聚丙烯酰胺水凝胶的制备及拉伸性能研究

为了提高水凝胶的弹性性能,采用微凝胶法制备了高弹性的聚丙烯酰胺(PAAM)水凝胶.先采用沉降聚合法制备了PAAM微凝胶,再以此充当交联剂代替传统的化学交联剂和引发剂,制备了高机械性能的PAAM水凝胶.同时探讨了丙烯酰胺浓度、凝胶成型温度、微凝胶与水的体积比对PAAM水凝胶弹性性能的影响.结果表明:随着丙烯酰胺的浓度的增大,凝胶柱的弹性模量变大;随微凝胶成型温度越高,形成的水凝胶的弹性模量越小;当微凝胶与水的体积比为1︰1时,水凝胶的弹性模量较大,增加或减少微凝胶的量均会使得水凝胶的弹性模量变小.

星形聚合物合成方法研究进展

介绍了星形聚合物的结构与特性、理论研究的意义和工业应用的前景,主要从合成途径上综述了星形聚合物的3种合成方法(多官能团偶联剂法、微凝胶法、多官能团引发剂法)的特点及其最新研究进展。

Preparation of Manganese Oxide Hollow Spheres Using pH-responsive Microgels as Templates

Manganese oxide hollow spheres were prepared by a novel and facile approach using pH- responsive microgels as templates. The final products were thoroughly characterized with X-ray powder diffraction, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared, and transmission electron microscopy. The results reveal that the shell thickness of manganese oxide hollow spheres increased with the dosage of KMnO4, which implies that a controllable and feasible strategy for manganese oxide hollow spheres prepa- ration has been established. Further studies on the microgels template showed some of them had an irreversible swelling/deswelling transition due to the uneven cross-link extent. Based on the results, a probable formation mechanism for the hollow spheres was proposed.

Photocatalytic H_2 evolution activity of CuO/ZrO_2 composite catalyst under simulated sunlight irradiation

Zirconia-supported CuO （CuO/ZrO2） composite photocatalysts were successfully synthesized via citric acid-assisted sol-gel technique. For comparison, CuO/ZrO2 materials were also prepared by solid state reaction and co-precipitation method. The as-prepared powders were characterized by X-ray diffractometry （XRD）, transmission electron microscopy （TEM）, and thermogravimetric-differential thermal analysis （TG-DTA）. The photocatalytic activity of CuO/ZrO2 catalyst was investigated based on the H2 evolution from oxalic acid solution under simulated sunlight irradiation. The effects of molar ratio of CuO to ZrO2, preparation method, phase change with the calcination temperature and the durability on the photocatalytic activity of the photocatalyst were investigated in detail. It is found that the optimal activity of photocatalytic H2 evolution （2.41 mmol.h i.g-~） can be obtained when CuO/ZrO2 composite photocatalyst is synthesized by sol-gel technique and the mole ratio of CuO to ZrO2 is 40%. The activity of copper oxide supported on monoclinic ZrO2 calcined at higher temperature is much higher than that on tetragonal ZrO2 calcined at lower temperature, and the best calcination temperature is 900 ℃.

Investigation of Swelling and Dissolution Process of Natural Rubber in Aromatic Oil

Aromatic oil has been used to promote the properties of crumb rubber modified asphalt which is an ideal method to deal with the resource utilization of waste rubber tires and by-product of refinery. Furfural extract oil(FEO) was separated into the light fraction and the heavy fraction. Swelling and dissolution process of natural rubber sheet in these three oil samples was investigated to shed light on the interaction mechanism. Crumb rubber also interacted on FEO and asphalt respectively. Energy dispersive spectrometer(EDS), thermo-gravimetric analysis(TGA) and scanning electron microscope(SEM) were used to characterize the chemical and structural properties of processed rubber. The chemical composition of processed oils and asphalt was investigated by using the hydrocarbon group analysis(SARA) and gel permeation chromatography. The results revealed that the swelling rate and mass loss of rubber in oils were much higher than those in asphalt and rose with an increasing processing temperature. The heavy fraction of FEO had more diffusion and dissolving capability than the light fraction, whilst compatibility was observed between the heavy fraction and the light fraction. Selective absorption was not observed in the study and detachment of dissolved rubber was disseminated from the outside to the inside. The cross-linking degree of the residue rubber was unchanged with the processing time, and sulfur predominantly remained in the undissolved rubber. Dissolution of crumbed rubber in oils was attributed to devulcanization, while that in the asphalt was mainly attributed to depolymerization.

Microstructure and electrical properties of La_2 O_3-doped ZnO-based varistor thin films by sol-gel process

Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.

Study on Microcapsulation of Onion Oil with Complex Coacervation and Spray Drying Method

[Objective] The aim was to study the microcapsulation of onion oil with double place separation-coacevation and spray drying. [Method] The effect of processing parameters which included the different wall material combination,the ratio between the wall material,the core material content and the feed concentration on the efficiency and yield of microencapsulated was evaluated by single factor experiments. [Result] Through orthogonal optimization experiments, the optimum condition was as follows: the ratio of Arabic gum and maltodextrin ration was 1∶1, the core content was 25%, feed composition was 18%, and the microencapsulation efficiency and yield can reach 80.7% and 95.3% respectively. [Conclusion] The microcapsulaiton of onion oil with complex coacervation spray drying method can increase membrane thickness, improve core stability and prolong shelf life of products.

Enhanced electrochemical property of FePO_4-coated LiNi_(0.5)Mn_(1.5)O_4 as cathode materials for Li-ion battery

Pristine LiNi0.5Mnl.5O4 and FePO4-coated one with Fd-3m space groups were prepared by a sol-gel method. The structure and performance were studied by X-ray diffraction （XRD） rietveld refinement, scanning electron microscopy （SEM）, high resolution transmission electron microscopy （HRTEM）, energy dispersive spectrometer （EDS） mapping, electrochemical impedance spectroscopy （EIS） and charge- discharge tests, respectively. The lattice parameters of all samples almost remain the same from the Rietveld refinement, revealing that the crystallographic structure has no obvious difference between pris- tine LiNi0.5Mn1.5O4 and FePO4-coated one. All materials show similar morphologies with uniform particle distribution with small particle size, and FePO4 coating does not affect the morphology of LiNi0.5Mnl05O 4 material. EDS mapping and HRTEM show that FePO4 may be successfully wrapped around the surfaces of LiNio.sMnl.s04 particles, and provides an effective coating layer between the electrolyte and the surface of LiNi0.5Mn1.5O4 particles. FePO4 （1 wt%）-coated LiNio.sMnl.504 cathode shows the highest discharge capac- ity at high rate （2 C） among all samples. After 80 cycles, the reversible discharge capacity of FePO4 （1 wt%） coated LiNi0.5Mn0.5O4 is 117 mAh g^-1, but the pristine one only has 50 mAh g^-1. FeP04 coating is an effec- tive and controllable way to stabilize the LiNi0.5Mn1.5O4/electrolyte interface, and avoids the direct con- tact between LiNi0.5Mn1.5O4 powders and electrolyte, then suppresses the side reactions and enhances the electrochemical performance of the LiNi0.5Mn1.5O4.