稳态时剪应力作用下胶体簇团形成/破裂的机理

Population correlation function P(t) has been used to examine the mechanism of breakage and coalescence of clusters at steady-state under shear, the results are in qualitative agreement with experiments. The research indicates that with a weak potential the mechanism of breakage and coalescence of clusters at steady-state under shear is predominately controlled by the particle-particle model, but that with a strong potential the mechanism shifts to that of cluster-cluster for large clusters; for small clusters, however, the mechanism of particle-particle model seems still to remain predominate, further work needs to be done.     

具有多体效应的胶体聚团的特征

考察了多体效应（用Ｓｔｕｔｔｏｎ－Ｃｈｅｎ势，ＳＣ）对胶体聚团的影响并与双体（ＬＪ）势下的结果作了比较。研究表明，ＳＣ和ＬＪ势下簇团的性质有其相似的一面，如：随着剪应力的增加，系统里颗粒的平均势能增加，而每个簇团的颗粒数减少；在较强的剪应力场里，簇团沿剪应力方向（Ｘ轴）被明显拉长且其主轴偏离Ｘ轴等。但它们间的差异也是明显的，在剪应力下ＳＣ系统内颗粒排列得更合理，从而使得平均位能比ＬＪ系统低约１－３     

稳态时剪应力作用下肢体簇团形成/破裂的机理

胶体簇团形成／破裂过程机理研究一直是胶体研究中一个十分活跃的领域．因为不同的聚团机理导致胶体不同的物理化学性质：粘度、空隙度、导电性甚至光学特性等,因而使其备受注目．当前,实验研究证明了簇团边缘的胶体颗粒和介质有着频繁的交换’‘’,特别是在受到外力的作用下,这种交换会更加激烈．计算机模拟研究证实了簇团和介质间颗粒交换的机理可以是颗粒一颗粒型的,也可以是簇团一簇团型的”、”．所谓颗粒一颗粒型机理是指（接近或完全）由单个颗粒互相结合,或单个颗粒被结合进大的簇团．在结合期间,被结合的颗粒可以在簇团边缘…     

胶体颗粒大小的分布——Ⅱ.物理显影中胶体催化剂颗粒大小的分布函数

本文用对数正态分布对物理显影中常用的Au、Ag及Ag_2s胶体催化剂的颗粒大小的实验分布进行了拟合。理论分布与实验分布的比较表明:本实验条件下制备的十二组胶体溶液其颗粒大小都服从了对数正态分布,并且不依赖于胶体的组成、大小及制备方法。因此,它们很可能遵从了同样的成核成长规律。     

带同种电荷胶体颗粒间的相互吸引

带同种电荷颗粒间存在静电吸引是当前胶体科学领域的一大研究热点, 也是颇有争议的一个课题。经典的DLVO 理论认为, 电解质溶液中一对孤立、带同种电荷的球型胶粒将表现出纯粹的库仑排斥。以往的实验事实也证实了DLVO 理论的正确性。然而, 近十几年来的实验研究表明, 在一定条件下, 同性颗粒间的有效相互作用势能可能表现出静电吸引。对此, 至今还没有一个令人信服的理论描述, 甚至连其产生根源也未有定论。带同种电荷颗粒的静电吸引将是一个很值得探讨的问题。     

胶体颗粒在聚电解质多层膜表面的可控组装

利用原子力显微镜和扫描电子显微镜研究了磺化聚苯乙烯胶体颗粒在由聚二甲基二烯丙基氯化铵和聚苯乙烯磺酸钠层状自组装而成的多层膜表面的组装.该组装受表面性质影响,通过对多层膜的最外层的组装条件或利用盐溶液对多层膜进行后处理可以控制胶体颗粒在膜表面的组装密度.     

胶体化学中计算机模拟的进展

简述了当前计算机模拟在胶体化学中的主要应用，特别涉及到数值方法的改进，热力学性质的模拟，簇团形成或破裂的动力学性质的模拟以及簇团结构和形貌特征的模拟。基本揭示了当前计算机模拟在胶体化学中的主要应用和最新进展。     

重力场和电解质浓度对胶体凝聚体分形结构的影响

运用李航等提出的新方法, 克服了DLVO理论中无法理论计算不同电解质浓度下颗粒的表面电位这一困难, 从而可以直接计算出不同电解质浓度下胶体颗粒间的位能. 同时, 还运用胶体颗粒动能的玻耳兹曼分布原理和蒙特卡罗方法来模拟胶体的运动, 并采用非弹性碰撞理论解决了碰撞后凝聚的有效概率问题. 在改进DDA模型的基础上, 成功地建立了以往的模拟中未能建立的重力场中电解质浓度与碰撞凝聚概率间的联系, 结果发现, (1)重力场作用下的凝聚体分形维数随电解质浓度变化的曲线完全不同于无重力条件下的曲线. 无重力作用下, 凝聚结构体分形维数随电解质浓度的变化比较缓慢, 曲线呈“L”形；而重力作用下的分形维数则呈明显的“S”形曲线. (2) 在重力条件下, 慢凝聚包括两个区域, 对电解质浓度不敏感区域和敏感区域. 在敏感区域存在一个电解质浓度的拐点. (3)无重力条件下,不同大小的胶体颗粒在快凝聚时的分形维数都是在1.86±0.01.当电解质浓度降低,凝聚速率变慢,分形维数增加,最大达到2.01±0.02,但不会形成重力条件下的分形维数接近3的结构体.     

扩散控制胶体聚集的Monte Carlo模拟

本文运用Ｍｏｎｔｅ Ｃａｒｌｏ方法模拟了三种不同情形下扩散控制的胶体聚集过程；（１）胶体扩散系数与聚集数的平面方成反比；（２）胶体扩散系数与聚集数成指数关系减小；（３）胶体扩散系数为常数。     

Characteristics of Colloidal Aggregates with Weakly Bound Potential under Shear

Research on characteristics of colloidal aggregates with Lennard-Jones potential an tier shear has been carried out. The features included cluster sire distribution, radial distribution function, fractal dimension and coordination numbers. It revealed that cluster size distribution approached to smaller site radial distribution function and coordination number reduced graduately with increasing shear rates. When shear rates increased. fractal dimension ranging 1.9-24, increased first then decreased slightly. Shear did not change fractal dimension obviously, however. clusters were stretched at X (shear rate) direction and deviated from the X direction at high shear rates.     

Colloidal adhesion of phospholipid vesicles: high-resolution reflection interference contrast microscopy and theory

High-resolution reflection interference contrast microscopy (HR-RICM) was developed for probing the deformation and adhesion of phospholipid vesicles induced by colloidal forces on solid surfaces. The new technique raised the upper limit of the measured membrane–substrate separation from 1 to 4.5 μm and improved the spatial resolution of the heterogeneous contact zones. It was applied to elucidate the effects of wall thickness, pH and osmotic stress on the non-specific adhesion of giant unilamellar vesicles (ULV) and multilamellar vesicles (MLV) on fused silica substrates. By simultaneous cross-polarization light microscopy and HR-RICM measurements, it was observed that ULV with the wall thickness of a single bilayer would be significantly deformed in its equilibrium state on the substrate as the dimension of its adhesive–cohesive zone was 29% higher than the theoretical value of a rigid sphere with the same diameter. Besides, electrostatic interaction was shown as a significant driving force for vesicle adhesions since the reduction in pH significantly increased the degree of deformation of adhering ULV and heterogeneity of the adhesion discs. The degree of MLV deformation on the solid surfaces was significantly less than that of ULV. When the wall thickness of vesicle increased, the dimension of contact zone was reduced dramatically due to the increase of membrane bending modulus. Most important, the adhesion strength of colloidal adhesion approached that of specific adhesion. Finally, the increase of osmotic stress led to the collapse of adhering vesicles on the non-deformable substrate and raised the area of adhesive contact zone. To interpret these results better, the equilibrium deformation of adhering vesicle was modeled as a truncated sphere and the adhesion energy was calculated with a new theory.     

Colloidal crystals made of poly(N-isopropylacrylamide) microgel particles

Poly (N-isopropylacrylamide) microgel particles are found to form colloidal crystals similar to those occurring in typical hard-sphere colloids like poly(methylmethacrylate) beads. Samples made of particles with different cross-linker concentrations are investigated and their deswelling ratio is determined using dynamic light scattering. Small-angle neutron scattering data are also presented and analysed in terms of a face-centred-cubic crystal structure. The characteristic length, a, of the elementary cell is found to be 535 ± 16 and 495 ± 15 nm for the two systems investigated. This leads to particle radii of 189 ± 6 and 175 ± 5 nm, respectively. These values compare well to the radii determined using several different methods. Received: 26 July 1999/Accepted: 21 March 2000     

Colloidal magnesium aluminum hydroxide and heterocoagulation with a clay mineral. I. Properties of colloidal magnesium aluminum hydroxide

Magnesium aluminum hydroxide, the most important member of layered double hydroxides, was peptized by intense washing. The particle diameter, 70–130 nm, depended on the temperature of aging the parent material. The electrophoretic mobility of the particles decreased with increasing pH, from 3.7 × 10⁻⁸ m²/Vs at pH 5 to 0.5 × 10⁻⁸ m²/Vs at pH 12.3. An isoelectric point at pH∼7 was reached with the addition of 87 mmol/l NaSCN, 3 mmol/l Na₂SO₄ and Na₂CO₃, and 0.7 mmol/l Na₂HPO₄. The critical coagulation concentration for the 2% (w/w) dispersion was 88 mmol/l NaCl, 1.8 mmol/l Na₂CO₃, 1.4 mmol/l Na₂SO₄, and 1.2 mmol/l Na₂HPO₄ at pH∼7. The 2% dispersion at pH∼7 showed an almost Newtonian flow behavior. Yield values were developed after salt addition. The 2% dispersion reached a yield value of 2 Pa at 100 mmol/l NaCl, 3 Pa at 100 mmol/l Na₂SO₄, and 5 Pa at 100 mmol/l Na₂CO₃. Sodium phosphate in comparison with the other salts showed a liquefying effect. The yield value increased to 3 Pa at 1–10 mmol/l Na₂HPO₄ and decreased to 0.5 Pa at 100 mmol/l Na₂HPO₄. Received: 28 February 2001 Accepted: 8 March 2001     

用积分方程方法决定胶粒之间的空耗势

Binary components Ornstein-Zernike integral equation with the concentration of large particle component being set to zero was employed to study the depletion potential behavior between two large neutral colloid particles （modeled as hard spheres）immersed in a sea of small neutral solvent particles. The prediction for the depletion potential behavior compared well with simulation data and experimental data available in the literature. It is found that the Hansen-Verlet one phase criterion,based on the effective one component system with the present depletion potential,for the freezing transition is completely not suitable for the real binary components system. It is disclosed that the unsuitability is due to the volume term of the solid phase and liquid phase which can not be treated selfconsistently in the Hansen-Verlet one phase criterion.     

胶体晶体剪切模量的影响因素

利用自行搭建的扭转共振谱仪,研究了不同粒子体系胶体晶体在不同体积分数下的剪切模量,利用反射光谱测量了相应的晶体结构及内部孔洞等参数.结果表明,同一粒子体系的剪切模量均随体积分数的增加而增大;而对于同样的粒子数密度,不同粒子体系的剪切模量随体系内部孔洞所占比例增加呈增大趋势.对实验结果的分析及与理论分析的对比表明,决定胶体晶体剪切模量大小的主要因素是胶体晶体中粒子的最近邻间距,从而统一解释了体积分数和内部孔洞对胶体晶体剪切模量的影响.