布朗扩散系数对胶体聚集粒子簇大小动态标度影响的MonteC …

通过对胶体扩散控制聚集机理的ＭｏｎｔｅＣａｒｌｏ模拟，表明粒子簇的布朗扩散系数与其大小和形状有关，粒子簇的大小分布可被标度、在微观或介观的层次上，揭示了表征粒子簇结构的几何形状因子在扩散控制聚集过程中对动态标度和粒子簇分布的影响。     

布朗扩散系数对胶体分形粒子簇扩散控制聚集动力学影响的Monte Carlo模拟

使用表征粒子簇结构的几何形状因子,通过对扩散控制聚集过程的模拟,从微观或介观层次研究了粒子簇结构对粒子簇增长速率和速率常数的影响规律,并与实验结果进行了对比分析.     

布朗扩散系数对胶体分形粒子簇扩散控制聚集动力学影响的 …

使用表征粒子簇结构的几何形状因子，通过对扩散控制聚集过程的模拟，从微观或介观层次研究了粒子簇结构对粒子簇增长速率和速率常数的影响规律，并与实验结果进行了对比分析。     

胶粒分形粒子簇反应控制聚集动态行为位垒影响的Monte Carlo模拟

通过对反应控制聚集过程的MonteCarlo模拟,从微观及介观层次上探讨了胶粒间相互作用位能曲线上位垒高度的变化对胶粒分形粒子簇大小分布和动态标度函数及聚集动力学行为的影响规律。     

炭黑填充聚苯乙烯熔体流变行为

研究了炭黑(CB)填充聚苯乙烯(PS)熔体的稳态和动态流变行为. CB/PS复合体系在CB体积分数φ=0.06时发生逾渗转变. 结果表明, 低应变区熔体模量降低主要归因于粒子-粒子及粒子-高分子间作用力的破坏, 高应变下模量的急剧下降则主要与高分子链间解缠结有关. 采用“两相”模型拟合线性动态流变行为, 发现应变放大因子A_f(φ)、填充相模量及松弛指数与温度有关. A_f(φ)~φ关系符合Guth方程和扩散控制的粒子簇聚集模型. “粒子相”形状参数与聚集体分维度均随温度升高而有所降低, 说明CB粒子聚集体因团聚而趋于各向同性, 应变放大效应减弱. “粒子相”特征模量G'_f1(φ)和G"_f0(φ)与φ关系满足标度律. 当φ > 0.06时, G'_f1(φ)和G"_f0(φ)及其标度指数均随温度升高而明显降低, 其G'_f1(φ)变化幅度略大于G"_f0(φ), 说明“粒子相”弹性与黏性组分具有不同的温度依赖性. 随着温度升高, 扩散控制的CB粒子团聚过程加快, 应变放大效应减弱.     

Patchy粒子聚集的统计力学研究

应用统计力学原理对A_aB_b型Patchy粒子的聚集过程进行研究, 考察了典型平均物理量在聚集过程中的变化情况. 首先基于配分函数导出体系的平衡自由能及描述Patchy粒子之间联接作用的质量作用定律, 进而获得团簇的数量分布函数. 进一步给出Patchy团簇的数均和重均聚合度以及物理凝胶化条件, 探讨了凝胶化区域与Patchy粒子数之间的依赖关系. 同时给出Patchy团簇生长的微分动力学方程, 并进行了相应的Monte Carlo模拟. 本文旨在揭示Patchy粒子的内在和外在因素对体系聚集态结构的影响, 为实现对Patchy粒子体系的有效调控提供理论依据.     

聚酰胺-胺树枝形大分子导致α-突触核蛋白聚集动力学变缓

采用基于Martini力场的粗粒化分子动力学模拟研究了聚酰胺-胺(PAMAM)树枝形大分子对α-突触核蛋白NAC区域聚集行为的影响,发现PAMAM树枝形分子的存在延缓了NAC区域聚集过程,增长了聚集体形成的时间.团簇形成的主要时间段里,大小与时间满足一定标度关系(～t^γ),且存在PAMAM时,标度指数γ减小. PAMAM大分子的代数和浓度越高,聚集体形成时间就越长;研究结果支持实验提出的“动力学抑制”猜想.     

聚合物PVP保护的贵金属纳米结构材料电化学合成新方法

以不同聚合度的聚乙烯吡咯烷酮(PVP)作为金纳米团簇的稳定剂和形状控制剂,应用电化学还原方法制备尺寸可控的金纳米晶体.借助PVP聚合物的动态伸缩和卷曲特性将电化学还原得到的金纳米粒子前驱体组装成线状和环状的纳米粒子聚集体,再由不稳定前驱体粒子的定向聚集制备厚度为几十纳米的金纳米棱柱.并用分步电化学还原法合成核壳结构的金银纳米复合粒子.本文为制备不同形状和结构的贵金属纳米结构材料提供了一种可行的电化学合成新方法.     

盐酸羟胺络合法制备银溶胶及表面增强拉曼基底

报道了一种制备银溶胶的新方法.用紫外-可见光谱和透射电镜研究了银纳米粒子的形成过程、粒子形状及粒径分布.紫外光谱结果表明,在还原剂中加入碘化银溶胶后立即形成银纳米粒子,开始时粒子的粒径较小,很快聚集成较大的粒子.随着反应的进行,较大的粒子又逐渐碎裂为较小的粒子.同时,粒子的粒径分布逐渐变窄,说明银纳米粒子的形成过程也是粒子粒径均化的过程.透射电镜的研究结果表明,银纳米粒子为形状均一的球形,平均粒径约35nm.将这种银纳米粒子转移到固体基片上可得到活性较高的表面增强拉曼(SERS)基底.     

激光溅射下原子团簇生长的非平衡动力学(Ⅱ)

在“半球模型”(即假设激光溅射产生的等离子体向空间均匀膨胀 )的基础上 ,在考虑了因等离子体膨胀和热辐射等引起的温度和体积的变化的情况下 ,进一步考虑了碳簇的链状、单环、双环、多环及富勒烯等五种结构及中性粒子与中性粒子、中性粒子与离子两种反应 ,计算了碳簇中性分子和离子的形成动力学及其尺寸分布.计算结果表明离子的尺寸分布可以近似代表中性粒子的尺寸分布 ,动力学计算所模拟的碳簇的尺寸分布与实验记录的碳簇离子的质谱特征较为相似.     

Computer simulation of selective aggregation in binary colloids

The morphology of clusters formed by selective aggregation of binary colloids is studied in a two-dimensional Monte Carlo simulation for a large range of number fractions (200:1, 100:1, 10:1, 2:1). We find remarkable similarity in morphology to those observed in experiments, from the formation of closed "micelles" to large branched clusters. Quantitative studies of the fractal dimension, kinetics, and cluster size distribution are also carried out and compared with diffusion-limited cluster aggregation and reaction-limited cluster aggregation models.     

Direct imaging of nanoscale acidic clusters in a polymer electrolyte membrane

One of the factors hindering the development of technologies that rely on the use of proton-conducting polyelectrolyte membranes is the lack of control over the membrane morphology on the nanoscale. Of particular importance is the rearrangement and clustering of acidic groups, which may seriously degrade the electrical properties. Although electron microscopy is capable of imaging the morphology of the clusters, images of unmodified membranes with sufficient quality to discriminate between different proposed cluster morphology models have not been presented. Here we show the first determination of the cluster size distribution in a model polymer electrolyte membrane from electron micrographs of individual acidic clusters. Imaging of the sulfur-rich clusters by dark-field microscopy was facilitated by the spontaneous formation of thin, cluster-containing layers on the top and bottom surfaces of free-standing films with a thickness of ~35 nm.     

原子簇离子产生的动力学方程与分布函数

由激光等离子体反应产生的原子簇分子与离子，经历了分子-离子反应的过程．本文尝试将Smoluchowski方程加以扩展，用于描述原子簇离子的生成过程．通过应用解析方法，求解不可逆聚合过程的动力学方程，推导出了原子簇离子统计分布的函数关系式，证实了实验中观察到的原子簇的统计分布规律．     

Nucleation and growth of cobalt nanostructures on highly oriented pyrolytic graphite

Cobalt in the form of three-dimensional (3D) hemispherical clusters (size approximately 10-30 nm) were observed to grow on pristine graphite surfaces via a Volmer-Weber growth mode. X-Ray photoelectron spectroscopy (XPS) reveals that these clusters are physisorbed on the surface. In the presence of minute surface contamination, the morphology of Co changes into a mixture of irregular and hemispherical three-dimensional islands. The formation of irregular islands appears to be mediated by the chemical interactions between Co and the surface contaminants as evidenced from analysis of the carbon pi-pi* transitions. Further analysis of size distribution of Co nanoclusters grown on pristine surfaces shows a critical nucleus size of i* = 1, i.e. a Co dimer forms the smallest stable cluster on a pristine graphite surface.     

Driven Brownian coagulation of polymers

We present an analysis of the mean-field kinetics of Brownian coagulation of droplets and polymers driven by input of monomers which aims to characterize the long time behavior of the cluster size distribution as a function of the inverse fractal dimension, a, of the aggregates. We find that two types of long time behavior are possible. For 0≤a<1/2 the size distribution reaches a stationary state with a power law distribution of cluster sizes having exponent 3/2. The amplitude of this stationary state is determined exactly as a function of a. For 1/2相似文献   

微乳液和均匀沉淀耦合法制备CeO2纳米粒子

用W/O微乳液和草酸二甲酯均匀沉淀耦合法制备出单分散性好并具有较窄粒度分布的CeO2纳米粒子,测试了其形貌、粒径及粒径分布和晶体结构等特征.实验结果表明,表面活性剂的种类和反应物的相对初始浓度对产物平均粒径具有规律性的影响;随着焙烧温度升高,产物的平均粒径明显增大.     

剪应力下弱作用势胶体颗粒聚团的特点

探讨了不同剪应力下，具有Ｌｅｎｎａｒｄ－Ｊｏｎｅｓ势的胶体颗粒聚团的结构特性，包括簇团的大小分布，径向分布函数，分形维数和原子配位数。研究表明，在弱作用力下，胶体簇团的分布随剪应力的增加而趋向小簇团一边；径向分布函数曲线随剪应力的增加而降低，胡在近程距离内降低得最多；分形维数随剪应力的增加表现为先增加后减小的趋势，其值随模拟条件的不同而在１．９－２．４之间变动。剪应力“场”对分形维数的大小没有太大     

Altering the crystal morphology of silicalite-1 through microemulsion-based synthesis

The crystal morphology of silicalite-1 was adjusted through a microemulsion-based hydrothermal synthesis. The surfactant cetyltrimethylammonium bromide (CTAB) with cosurfactant butanol was used to form water-in-oil microemulsions containing the silicalite-1 synthesis gel. The crystal morphology of silicalite-1 was adjusted from coffin-shaped to novel rod-shaped and to irregular-shaped nanoparticles by varying the microemulsion composition. Silicalite-1 synthesized in the microemulsion has a smaller size and a more narrow size distribution than that produced by conventional synthesis without the microemulsion. The novel morphology of silicalite-1 may facilitate assembly into films and find applications in separation and catalysis.     

可控大小与形态的(Sr0.70Mg0.07Ba0.10Ca0.11Eu0.02)5(PO4)3Cl荧光粉的研究

以不同大小和形态的SrHPO4为主要原料, 固相反应合成了(Sr0.70Mg0.07Ba0.10Ca0.11Eu0.02)5(PO4)3Cl荧光粉. 通过SEM, XRD, PL测定了颗粒大小与形态、晶体结构和发光性能. 结果表明, SrHPO4的颗粒大小与形态决定了固相反应产物荧光粉的大小与形态; 颗粒分布均匀、类球形荧光粉发光强度最大; 与其比较, 菱形、大小分布不均匀的荧光粉的发光强度是它的80%, 而多晶聚集体仅为65%.