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Wang J.,Shandong University | Liu G.,Shandong University | Liu G.,Shandong Institute of Education | Wang L.,Shandong University | And 3 more authors.
Colloids and Surfaces A: Physicochemical and Engineering Aspects

Liquid paraffin-water emulsions were prepared which were stabilized by Laponite particles in situ modified with poly(oxypropylene)diamines in the absence of electrolytes. First, the characteristics of the Laponite dispersions in the presence of increasing concentrations of diamines were studied in detail. Infrared absorption spectra and zeta potential measurements confirm the adsorption of diamines on the Laponite particles. Adsorption isotherms further indicate highly affinitive L-type behaviors and the diamine molecules are deduced to lie with both end groups anchored on the particle surface and the poly(oxypropylene) chain exposed to the aqueous solution. Then, emulsions were prepared using the diamine-modified particles. Diamines and Laponite particles alone are ineffective emulsifiers, but a strong synergism is exhibited between them. Laser-induced fluorescent confocal micrographs and TEM observations demonstrate the arrangement of the particles on the emulsion surfaces and also reveal the stability mechanisms. The emulsion stability was also explored with optical microscopy and droplet size measurements. As the diamine concentration increases, the extent of emulsion creaming decreases and the droplet size correspondingly decreases. At a certain low diamine concentration, the extent of emulsion creaming decreases down to a minimum and the corresponding droplet size is the smallest. This optimal emulsion state is unchanged when the diamine concentration is further increased. © 2009 Elsevier B.V. All rights reserved. Source

Liu G.,Shandong University | Liu G.,Shandong Institute of Education | Liu S.,Shandong University | Dong X.,Shandong University | And 3 more authors.
Journal of Colloid and Interface Science

Hollow colloidosomes consisting of plate-like Mg/Al layered double hydroxide (LDH) nanoparticles have been prepared by a facile route from a Pickering emulsion. The particles are first adsorbed onto the surface of paraffin oil-in-water emulsion droplets. After the core oil is dissolved in the surrounding bulk liquid, using solvents that are miscible with both the internal and external phases of the droplets, colloidosomes are formed. In this process, we find that the diameters of the colloidosomes are significantly reduced compared to those of the emulsion droplets. The reduction in the diameter is caused by rearrangement of the LDH platelets. That is, the platelets change their orientation from lying flat on the emulsion droplet surface to standing erect in a dense, face-to-face connecting pattern in the colloidosome shell. The main reason for the particle rearrangement is the increase of the attractive forces among the particles due to the reduced polarity of the solvents used during colloidosome preparation. © 2010. Source

Li S.,Shandong Institute of Education | Du L.,University of Jinan | Guan Y.,University of Jinan
Proceedings - 2010 7th International Conference on Fuzzy Systems and Knowledge Discovery, FSKD 2010

In an ordered decision information system, dominance-based rough set approach (DRSA) were used to compute reducts of the system which preserve the lower and upper approximations of upward union and downward union of decision classes. Recently, class-based reducts (L-reduct and U-reduct) which preserve respectively lower and upper approximates of each decision classes was proposed. In this paper, we modify the definition of U-reduct and propose the concept of U*-reduct which is comprehensive and convenient for drawing decision rules. We give an equivalent description of L-reduct and U*-reduct, and compute the L-reduct and U*-reduct utilizing discernibility function defined by discernibility sets of objects. ©2010 IEEE. Source

Wang J.,Shandong University | Yang F.,China University of Petroleum - East China | Tan J.,Shandong University | Liu G.,Shandong Institute of Education | And 2 more authors.

Liquid paraffin?water emulsions were prepared by homogenizing oil phases containing sorbitan oleate (Span 80) and aqueous phases containing layered double hydroxide (LDH) particles or Laponite particles. While water-in-oil (w/o) emulsions are obtained by combining LDH with Span 80, the emulsions stabilized by Laponite?Span 80 are always o/w types regardless of the Span 80 concentration. Laser-induced fluorescent confocal micrographs indicate that particles are absorbed on the emulsion surfaces, suggesting all the emulsions are stabilized by the particles. The difference of the particle-stabilized emulsion type may be explained by comparing particle contact angles and the oil?water interfacial tensions, indicating that more Span 80 molecules are adsorbed on the LDH particles than on Laponite. Apparently, the LDH particles are rendered more hydrophobic by Span 80, resulting in the formation of w/o emulsions. The long-term stability of the emulsions was also compared. Emulsions stabilized by Span 80 alone completely separate into two bulk phases of oil and water after 3 months. However, emulsion stability is greatly enhanced with the addition of LDH or Laponite particles. This synergism was accounted for by an increase of the dilational viscoelasticity modulus of the oil?water interface after particles were added to the aqueous phase. This increase indicates that the gel-like particle layer stays at the oil?water interface and resists emulsion coalescence. Scanning electron microscope (SEM) images display the presence of a firm layer surrounding the emulsion droplets and a three-dimensional particle network which extends into the bulk phase aiding emulsion stability. © 2009 American Chemical Society. Source

Jiang W.,Shandong University | Jiang W.,Shandong Institute of Education | Liu L.,Shandong University | Hao J.,Shandong University
Journal of Nanoscience and Nanotechnology

Manganese(II)-substituted polyoxometalate, Na 6(NH 4) 4[(Mn II(H 2O) 3) 2(WO 2) 2(BiW 9O 33) 2] · 37H 2O (POM-Mn), was assembled within lyotropic hexagonal liquid crystal (LLC) formed in the roomtemperature ionic liquids (RT-ILs), ethylammonium nitrate (EAN), fabricating the POM-LLC inorganic-organic hybrid materials. Polarized optical microscope images combined with small-angle X-ray scattering (SAXS) results indicate that the introduction of POM-Mn does not destroy the structure of hexagonal LLCs. The increase of d spacing demonstrates the integration of POM-Mn within the basic unit of the hexagonal LLCs. The FTIR spectra of the POM-LLC hybrid material show the characteristic absorption peaks of W-O bond. The rheological results indicate POM-LLC hybrid materials are highly viscoelastic and that the apparent viscosity is enhanced due to the introduction of the POM-Mn. The tribological properties were explored to greatly extend the applications of POM-LLC composites in RT-ILs as lubricating materials. The research of magnetic properties indicates the POM-LLC composite is ferromagnetic, therefore illuminating the potential application in the fields of magnetic materials. © 2011 American Scientific Publishers. Source

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