Papers by Keyword: Colloids

Abstract: Number concentration of colloidal particles and concentration of several drinking water contaminants (iron, aluminium, AOX) were determined in river water, water treated at WTP, tap water and their filtrates (pore diameter of filter 60 nm). It was shown that almost all AOX were present in highly disperse state (less than 60 nm), 55...90% of iron and 55...80% of aluminium belonged to impurities with size over 60 nm. Changes of contaminants state and concentration were explained by influence of water treatment processes and corrosion of steel water distribution pipes.

Abstract: A selected material, polystyrene microsphere series, is created as a building block of two-dimensional (2D) aggregates to examine scaling behaviors of the compressive stress condition. The 2D aggregated clusters are confined between the two cantilevers of 30 micron in diameter. These cantilevers can slide and force the aggregates move in the lateral direction. The compressive yield stress is directly measured during experiments by quantitative image analysis on the optical microscope. Locations of polystyrene aggregates are traced by Discrete Element Method (DEM), computer simulation. The 2D mechanical properties are examined for the particle size scaling behaviors as a function of particle area fraction and the average particle coordination number. The larger the particle size, the greater the modulus and the yield stress.

Abstract: In this work, TiO₂ nanoparticles (NPs) were prepared through a well-developed hydrothermal method. The dry products were characterized by digital camera, transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric method (TGA). These results suggested that TiO₂NPs were well-crystallized and oleic acid-capped (OA-capped; 33.42 wt.%). In order to investigate the flocculation and stability of TiO2NPs colloids, redispersed experiments were carried out by altering the preparative parameters (e.g., redispersion solvent, washing times). In addition, the compounding stability of TiO₂NPs colloids with AuNPs colloids and MnO_4- solution under processing conditions (e.g., aging with stirring and under UV irradiation) were also studied. In principle, systematic investigations of flocculation and stability of TiO₂NPs will be useful for their potential applications including novel photocatalysts and biosensors.

Abstract: Colloidal packing by evaporation is a process that particles are packed by Stokes’ forces. As particles are far from each other, interactions among them are too weak to be taken into account and it’s the Stokes’ force on free particles that is in charge of packing. However, when they are close to some extent, the force is countered by particle interactions. Here, with the aid of force balance model, we demonstrate that the further packing is achieved by all drag forces of particles in the upstream.

Abstract: Convective self-assembly of colloidal spheres provides a simple method for fabricating two and three dimensional colloidal crystals. In this work, we investigated the layer transitions phenomena during colloidal self-assembly in a sessile drop by using an in-situ videoscopic set-up. The effects of surface charge, colloidal concentration, and surfactant additions were examined. The results show that the chemical environment plays an important role in colloidal self-assembly. In the case of ordered growth, different layer transition phenomena were observed when the colloidal concentration is different.