小麦粉中阿拉伯木聚糖氧化胶凝性质的研究

本文采用小振幅振荡流变测量法对小麦面粉中水可提取阿拉伯木聚糖 (WEAX)的氧化胶凝性质进行了研究。结果表明 ,WEAX的氧化胶凝能力与小麦粉的氧化处理情况、小麦粉的品种有关 ;增加过氧化物酶用量可加快凝胶形成速率 ,H2 O2 则有一最适用量 (30 0～ 1133ppm) ;WEAX浓度增加 ,凝胶结构的弹性增大。不同小麦粉中WEAX的组成和结构分析显示 ,WEAX的分子量对它们的氧化胶凝性质的影响最大。

Study on Properties of Composite Oxides TiO_2/SiO_2

The nanometer particles of TiO_2 and TiO_2/SiO_2 oxides wereprepared by sol-gel supercritical fluid drying method. The propertiesof TiO_2 and TiO_2/SiO_2 were characterized by means of BET(Brunner-Emmett- Teller method), TEM (transmission electronmicroscopy), SEM (scanning electron microscopy), XRD (X-ray diffrac-tion) and FTIR (Fourier transform-infrared) techniques. The effectsof different preparation route, prehydrolysis and non-prehydrolysis,on the properties of TiO_2/SiO_2 oxide were also examined.

Sol-Gel Synthesis and Structure-Property Relations in Nd4-xCs2（1＋x）Fe5-xZnxO14＋δ（0≤x≤1.0） Oxide Systems

Synthesis of composite oxides in the series Nd4-xCs2（1＋x）Fe5-xZnxO14＋δ（0≤x≤1.0） （B1-B5： x= 0.0, 0.25, 0.5, 0.75, 1.0） is performed by sol-gel method via nitrate-acetate precursor route. Analysis of the powder x-ray diffraction （XRD） patterns show tetragonal unit cell with lattice parameters a = 8.6545, 8.2520, 7.7645, 9.8952, 8.2863 A; b = 8.9800, 11.5788, 15.6305, 8.4766, 11.6465 A in B1-B5, respectively. The average crystallite sizes in the samples are found to be in the range 69.56-119.48 A. Energy dispersive analysis of x-rays （EDAX） result shows the presence of Fe, Nd, Cs and O, and Fe, Nd, Zn, Cs and O in B 1 （x=0） and B2（x=0.25）-B5（x= 1.0）, respectively. The IR results at 300 K show the presence of octahedral [NdO6/2]^3- （asymmetric stretch： 410-416 cml） and [FeO6/2]^3-（symmetric stretch： 562-572 cm^-1） units in the samples. Observed magnetic moments versus magnetic field plots in the range -10 kG to ＋10 kG exhibit hysteresis loops with average magnetic susceptibility values in the range 3.46 × 10^-5 -7.05 × 10^-5 emu/gG in B1-B5 shows fairly strong ferromagnetic nature of the samples. The observed EPR lineshapes at 300 and 77 K with giso=2.01-2.03 and giso=2.01-2.03, respectively is ascribed to the octahedral [FeO6/2]^3- coordination of Fe^3＋ （3d^5） ion. The optical absorption spectra show the transition of ^4I9/2→^4F7/2→^ 4S3/2 （750 nm） of optically active Nd^3＋ ions in samples.

Science Letters; In-situ synthesis and luminescence properties of titanium oxide gels containing 1,10-phenanthroline europium(Ⅲ) complex

It is difficult to directly dope europium complexes in gel because the excessive water or high acidic condition may lead to their decomposition. We prepared a novel homogeneous TiO2 gel containing Eu-phen complexes by using an in-situ synthesis method. The formation of Eu-phen complexes in sol-gel derived TiO2 was confirmed by luminescence excitation spectra. The effects of temperature and aging time on in-situ synthesis are discussed. The luminescence spectra of gel containing europium complexes were also compared with the pure Eu-phen complexes.

Electron-Irradiation Induced Nanocrystallization of Pb（ll） in Silica Gels Prepared in High Magnetic Field

In a previous study, structure of silica gels prepared in a high magnetic field was investigated. While a direct application of such anisotropic silica gels is for an optical anisotropic medium possessing chemical resistance, we show here their possibility of medium in materials processing. In this direction, for example, silica hydrogels have so far been used as media of crystal growth. In this paper, as opposed to the soft-wet state, dried silica gels have been investigated. We have found that lead （II） nanocrystallites were formed induced by electron irradiation to lead （ll）-doped dried Hydrogels made from a sodium metasilicate solution doped with silica gels prepared in a high magnetic field such as B = 10 T. lead （II） acetate were prepared. The dried specimens were irradiated by electrons in a transmission electron microscope environment. Electron diffraction patterns indicated the crystallinity of lead （II） nanocrystallites depending on B. An advantage of this processing technique is that the crystallinity can be controlled through the strength of magnetic field B applied during gel preparation. Specific skills are not required to control the strength of magnetic field.

Adsorption and Transfer Properties for Toluene and pDichlorobenzene in Dense CO_2/Silica Gel Packed Bed System by Moment Method and Time-Domain Analysis

Based on chromatographic theory, the moment method and the time-domain fitting analysis were applied to measure and evaluate the adsorption equilibrium constant and mass transfer properties (axial dispersion coefficient and effective intra-particle diffusivity) for toluene and p-dichlorobenzene on silica gel adsorbent in the subcritical and supercritical CO2. An apparatus based on supercritical fluid chromatography was established and the experiments were performed at temperatures of 298.15-318.15 K and pressures of 7.5-17.8 MPa. The two methods have been compared. The results show that for the systems studied here the moment method can give reasonable values for both adsorption equilibrium constant and mass transfer properties, but the time-domain analysis only can obtain the adsorption equilibrium constant. The dependence of adsorption equilibrium constant and mass transfer properties on temperature and pressure was investigated.