PVP改性氧化硅溶胶的微结构和流变性

以正硅酸乙酯为前驱体,聚乙烯吡咯烷酮（PVP）为聚合物改性添加剂,在碱性条件下制备氧化硅溶胶,通过小角X射线散射测量了改性溶胶的微结构参数,辅以动态光散射观测溶胶颗粒生长,研究了聚合物量、碱催化剂量和水量对溶胶颗粒度、分形特征以及流变性的影响规律.由于PVP链中强极性的分子内酰胺基团和氧化硅颗粒表面的羟基形成氢键,致使溶胶颗粒被聚合物链包裹,严重阻碍了溶胶颗粒的生长,使凝胶时间延长,流变性发生变化,同时对溶胶颗粒的微结构产生影响.     

小角X射线散射技术在高分子表征中的应用

小角X射线散射(SAXS)技术是表征高分子材料微观结构的一种重要手段.当X射线穿过材料时,在材料不均一的电子云密度分布作用下,发生散射并形成特定的散射图案,使得我们可以根据特定的模型来反推材料的微观结构,并计算相关结构参数.SAXS特有的对微观结构的统计平均及无损探测使其成为了一种不可或缺的高分子材料微观结构分析手段....     

NaCl、KCl、Na_2CO_3、K_2CO_3等电解质溶液对含水卵磷脂液晶结构影响的SAXS研究

关于电解质溶液对卵磷脂液晶结构的影响前人有过报导。例如Chapman和G. Shiply等在研究碱金属氯化物对卵磷脂液晶结构的影响时指出:随着Li~ 到Cs~ 离子半径增加,脂双层的厚度也发生相应变化。Plainer等也指出KCI,NaCl溶液使磷脂层厚度发生变化。关于磷脂蛋白复合膜与Na~ ,K~ 、Ca~(2 )离子的作用也有一些报导。本文报导用小角X射线散射(SAXS)方法研究几种电解质溶液对卵磷脂形成液晶结构的影响。     

单分散SiO2体系制备中TEOS水解动力学研究

采用一种与他人不同的萃取－冷冻分离－气相色谱法，跟踪形成单分散二氧化硅体系条件下正硅酯乙酯（TEOS）的水解过程，考察了温度（25～45℃）、氨浓度（0．5～0．2mol•L－1）、水浓度（6．0～15．0mol•L－1）等实验条件范围内，以上实验参数对TEOS水解速度的影响；并回归得到目前适用于在乙醇介质中氨催化下，形成单分散二氧化硅微粒常用实验条件范围内，唯一的较完整的水解动力学方程式．     

NaCl、KCl、Na2CO3、K2CO3等电解质溶液对含水卵磷脂液晶结构影响的SAXS研究

This paper describs the structural character of liquid-crystal of 5%H_2O-egg yolk phospholipid (PC) containing in avarious salt's solution, the layer distance was determined by means of SAXS method. Experimental results show that the layer distance of liquid crystal phase is increased in the 5%H_2O-PC system as the amount of solution of NaCl or KCl is increased. But on the addition of Na_2CO_3 or K_2CO_3 solution into the 5%H_2O-PC system the layer distance of liquid-crystal phase is held constant. It is considered that Na_2CO_3 or K_2CO_3, might be hydrolyzed producing OH~- ions, so that the latter could stablize the interfacial potential between water and egg yolk phospholipid. Absence of this behavior for solution of NaCl or KCl might be due to NaCl and KCl are salts which formed by strong acids and strong bases.     

疏水增透SiO2膜的制备及其性能研究

以正硅酸乙酯(TEOS)和二甲基二乙氧基硅烷(DDS)为前驱体，在碱催化体系中通过选择合适的原料配比以及对体系溶胶 凝胶过程的控制使DDS和TEOS的水解产物发生共缩聚反应，进而制备出改性的SiO2溶胶，并采用旋转镀膜法(spin coating)直接获得了同时具有良好疏水和增透性能的SiO2光学膜，克服了增透膜防潮性能差的缺点.同时采用透射电子显微镜（TEM）、粒度分布（SDP）等手段研究了不同条件下溶胶的性质及其对膜层性能的影响，并与未经改性的SiO2增透膜进行了比较，结果表明改性后的膜层不仅疏水性大大增加，且在相同镀膜条件下，膜层的厚度随着老化时间的延长增加较小，故其透过率曲线在300～800 nm范围内不易出现多个增透峰.     

紫外光辐射对TiO2溶胶的影响研究

用紫外-可见吸收光谱、动态光散射与透射电镜研究紫外光辐射对T₂溶胶的影响,结果表明,光辐射使T₂溶胶在可见光区的吸收减少,紫外区吸收增加,吸收带隙增大.与非光辐射的T₂溶胶粒子相比,光辐射使T₂溶胶粒子分布均匀且平均粒径减小,提高了T₂纳米粒子在室温下的晶化程度.     

SiO2 溶胶及其静电自组装薄膜的制备

Silica sols were prepared by hydrolysis of Si（OC2H5）4（TEOS）using HCl,NH3·H2O,HCl/NH3·H2O as catalyzers,and the different granularities of SiO2 sols which catalyzed by HCl first and then NH3·H2O have the same terminal pH value were prepared. The silica colloidal particles were investigated with Transmission Electron Microscope（TEM）. The results showed sol catalyzed by HCl possesses very little particle,catalyzed by NH3·H2O has particle configuration,catalyzed by HCl/NH3·H2O possesses consecutive configuration. Poly（diallyldimethylammonium chloride）（PDDA）and SiO2 nanoparticulate complex thin films were prepared by electrostatic self-assembly multiplayer（ESAM）method. After assembling films,thin films surface conformation was observed with Electron Microscope and their transmittance was tested with 721 Spectrophotometer. The results showed that the silica sol catalyzed with HCl is not good for the fabrication of ESAM films and the silica sol catalyzed with HCl first and then NH3·H2O or by NH3·H2O only are very suitable for ESAM film fabrication. TEM data indicate that the microstructure of PDDA/ SiO2 prepared from silica sol catalyzed with HCl first and then NH3·H2O is consecutive and that the microstructure of PDDA/ SiO2 prepared from silica sol catalyzed by NH3·H2O only is particulate-parking like. The dependence of the transmittance of assembled films on the bilayer number of the films and the anti-scratching properties of the films were investigated. The results show that PDDA/ SiO2 films prepared from silica sol catalyzed by NH3·H2O only possess higher transmittance but lower anti-scratching properties. The effect of granularity of sols on optical performances of the thin films was studied,results showed the less the granularity of sol,the better the optical performances. For the sake of improving the light transmittance of films,we can reduce the granularity of sol,but it may play down its mechanical damage resist intensity.     

PbF2·SiO2基玻璃陶瓷的溶胶-凝胶制备及结构转变研究

采用溶胶-凝胶法制备了PbF2·SiO2纳米晶玻璃陶瓷块体;利用TG-DSC和IR技术分析了干凝胶在热处理过程中有机基团的分解及内部原子键合方式的演变;结合XRD和TEM研究了凝胶玻璃中PbF2纳米晶粒的长大过程,并分析了Er3+掺杂的影响.结果表明,采用此方法制备的PbF2.SiO2纳米晶粒玻璃陶瓷具有较好的成形性,晶化温度在320℃左右;经480℃热处理,镶嵌在玻璃基体中的PbF2晶粒尺度约为10-25nm,材料透明性良好.在PbF2·SiO2系统中掺入少量的Er3+,将提高PbF2的晶化温度,降低玻璃陶瓷的显微硬度;掺杂可能对PbF2晶粒表面原子的活性起抑制作用,阻碍晶粒的表面迁移,使晶粒的生长速度明显降低.     

溶胶-凝胶法原位生成SiO2改性硅基耐烧蚀材料

建立了在硅基耐烧蚀材料中用溶胶-凝胶法原位生成SiO2的方法.首先将硅橡胶、气相白炭黑、纤维等原料混炼硫化制备出硫化胶.然后将硫化胶依次浸入四氢呋喃、原硅酸乙酯和正丁基胺水溶液中进行预溶胀处理、物理扩散和化学反应,得到原位生成SiO2.SEM照片显示,在硅基耐烧蚀材料中原位生成的SiO2颗粒呈球形,粒径在40~60 nm,但分布不均匀,在硫化胶表层存在富集现象.实验结果表明,原位生成SiO2平均含量增加,硅基耐烧蚀材料的抗拉强度增加,线烧蚀率下降;含13.7%原位生成SiO2硅基耐烧蚀材料抗拉强度为5.82 MPa,线烧蚀率为0.071 mm/s.     

Microstructure Analysis of Nylon 66 by WAXD and SAXS

IntroductionNylon 66,one of the most successfulcommercial polyamides,has been widely usednowadays as an engineering plastic in many fields.The development of the structure of nylons is acontinuing area of their technological and scientificstudy.The structure of nylon 66 during thephotoinduced decomposition process has beenstudied by resonance Raman[1] ,and the effect oftranscrystalline layers have been investigated[2— 4] .Moreover,the crystallization and meltingbehavior[5] have been learned …     

SAXS测定二氧化硅胶体粒子结构

本文考察了正硅酸乙酯(TEOS)在碱性催化条件下通过水解和缩聚而制得的二氧化硅胶体的小角X-射线散射(SAXS)特征，通过散射数据对Porod负偏离的分析和校正，测定了胶体粒子的几何结构，包括胶团尺度分布、胶核尺度分布及平均界面层厚度，这有助于认识胶体的物理化学特征。     

培养真核微生物矿化生成纳米SiO2构筑体及其表征

细胞模板;生物矿化;纳米结构SiO2;TEOS;Na2SiO3     

Tensile tests of polypropylene monitored by SAXS. Comparing the stretch‐hold technique to the dynamic technique

Advanced instrumentation at synchrotron beamlines facilitates considerable reduction of the exposure required for the recording of low‐noise small‐angle X‐ray scattering (SAXS) patterns. Concerning the monitoring of tensile tests on polymer materials by SAXS means that change‐over from the stretch‐hold technique to more practical dynamic straining is possible, although the strain rate is still by a factor of 100 lower than that relevant in industry and service. As hard‐elastic polypropylene (PP) is tested, considerably different scattering patterns are recorded after switching to the dynamic technique. Even though during exposure the elongation is no longer constant when applying the dynamic technique, the images collected in stretch‐hold technique appear much more blurred. The observed immediate relaxation of nanostructure induced by stopping the extensometer is analyzed by means of the multidimensional chord distribution function (CDF): The extension of the crystalline lamellae is increasing. Their thicknesses are becoming non‐uniform. The range of order is shortening. Cross‐hatched lamellae are formed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 721–726, 2008     

Small strain behavior of polyethylene: In situ SAXS measurements

Stack lamella deformation depends on their orientation with respect to the loading axis, the intrinsic properties of the lamellae, and the mechanical coupling between crystalline and amorphous phases. The aim of this work is to investigate the influence of the stress transmitter (ST) density and the crystallinity X_c on the local deformation. A wide experimental campaign has been undertaken on several polyethylenes with controlled molecular parameters and subjected to different thermal treatments. The ST density has been evaluated by the natural draw ratio and calculated by the Brown's model. The local deformation was measured by SAXS along a tensile test by using the long period stretching of the equatorial lamella stacks. The ratio ε_local/ε_macro was found to be a constant close to 0.5. This surprising low value has highlighted that the equatorial regions could be either the stiffest zone of the spherulite or submitted to a lower stress. It is proposed that the stability of the ratio ε_local/ε_macro is the result of two opposite phenomena: On one hand, the increase of X_c leads to unload the equatorial regions due to partial percolation of the crystalline phase and so decreases the stresses. On the other hand, when increasing X_c, the ST density decreases which causes the decrease in the local equatorial modulus. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1535–1542, 2010     

Study of secondary porosity by SAXS and N2 adsorption in composite materials obtained from a Cuban natural clinoptilolite

In this work, a study of the secondary porosity of two zeolite-based composites is carried out by small angle X-ray scattering (SAXS) and N₂ adsorption at 77 K. The composites were obtained by the inclusion of ZnO nanoparticles in a Cuban natural clinoptilolite by mechanosynthesis and ‘in situ’ methods. It was observed a decrease in the specific surface area as a result of ZnO nanoparticles inclusion from 149 m² g⁻¹ in the started material to 60 m² g⁻¹ in the composite prepared by in situ method, whereas the mesopore diameter remained almost constant. The results confirmed the presence of mesopores with diameter between 3 and 36 nm, with good match by both methodologies. These materials were developed in view of their future application as catalysts and adsorbents, where the presence of secondary porosity is key to favor the diffusion processes.     

酵母细胞为模板矿化合成SiO2纳米结构材料的研究

根据无机盐可以在生物细胞膜上沉积形成纳米结构材料的现象和生物矿化理论, 在人工培养条件下, 成功地以低等真核生物细胞-酵母菌为模板, 以正硅酸乙酯(TEOS)作为硅源, 矿化合成了一种壳鞘状的SiO2纳米结构材料, 厚度达150 nm左右, 并采用TEM、SEM、EDX、FT-IR、TGA等表征手段对实验结果进行了深入细致的研究, 获得了大量的实验数据, 为利用生物细胞模板合成介观尺寸有序SiO2纳米材料作出了有益的尝试.     

溶胶—凝胶法制备NiO／SiO2催化剂研究

分别以正硅酸乙酯、硝酸镍为硅源和镍源,采用溶胶－凝胶法,经超临界流体干燥和普通干燥制备了NiO-A-SiO2、NiO-G-SiO2催化剂;以气凝胶和干凝胶为载体,采用浸渍法制备了NiO/A-SiO2、NiO/G-SiO2催化剂。并用XRD、TEM、BET、TPR等手段,研究了制备方法对催化剂织构、结构和Ni物种存在形态的影响,发现NiO-A-SiO2和NiO-G-SiO2催化剂上高度分散的NiO簇团与SiO2之间有较强的相互作用,其顺酐液相选择加氢转化率低于10％;NiO/G-SiO2催化剂上,以单一物种形态存在的NiO与SiO2相互作用弱,顺酐转化率为42％;NiO/A-SiO2催化剂上,以多种形态存在的微量NiO与SiO2间的相互作用较复杂,其顺酐液相选择加氢的转化率和丁二酸酐的选择性分别可达100％和98％。     

小角X射线散射法研究CH2Cl2,CHCl3和CCl4对PE液晶结构的影响

采用小角X射线散射法研究了CH_2Cl_2、CHCl_3和CCl_4对磷脂酰乙醇胺(PE)液晶结构影响的机理.CH_3Cl_2、CHCl_3和CCl_4对PE液晶结构影响的差别主要是其空间旋转电子云密度分布形状不同所致.空间旋转电子云密度分布呈椭球状的物质有使PE液晶形成六角形H_1相的趋向;呈圆锥状的物质有诱发PE液晶形成立方六角相的趋向;呈球状的物质有使PE液晶形成片层立方相的趋向.