Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fails in explaining the superior stability of colloid particles in aqueous suspensions under conditions of high ionic strengths where electrostatic forces are effectively screened. Accumulating evidence shows that the formation of a thin rigid layer of solvent molecules in the vicinity of a colloidal particle surface provides an additional repulsive interaction when the interparticle distance is reduced to several nanometers. The effective determination of the thickness of the solvation layer however remains a challenge. Here, we demonstrate a simple yet powerful magnetophotonic technique that can be used to study the thickness of the solvation layers formed on the colloidal silica surface in various polar solvents. A relationship between the hydrogen-bonding ability of the solvents and the thickness of solvation layer on colloidal silica surfaces has been identified; this observation is found to be consistent with the previously proposed hydrogen-bonding origin of the solvation force.
"ls increases the size of asphaltene particles . Therefore , addition of DBSA enhances heavy oil viscosity due to the decreased size of asphaltene particles while LA reduces heavy oil viscosity due to the increased of size asphaltene particles . It is also well known that a solvation layer is formed around the colloidal particles in aqueous phase ( He et al . , 2012 ) . This solvation layer moves with colloidal particles and protect the particles from coagulation . Solvation of colloidal particles takes place not only in aqueous phase but also in oil phase . A lot of works ( Storm et al . , 1994 ; Storm and Sheu , 1995 ; Luo and Gu , 2007 ; Ghanavati et al . , 2013 ) have shown that a thick solvati"
[Show abstract][Hide abstract] ABSTRACT: The effects of two amphiphiles, DBSA and LA, on the associating state and viscosity of three heavy oils with different resin/asphaltene (R/A) mass ratios were investigated through DSC analysis, rheological test and electrical conductivity measurement. The wax appearance temperatures of the three heavy oils are lower than 40 °C. The viscosity of heavy oils at temperature range 50~70 °C increases with increasing DBSA concentration but decreases with increasing LA concentration. Addition of DBSA increases the electrical conductivity of heavy oils, which implies that the DBSA acts as asphaltene dispersants; the electrical conductivity of heavy oils decreases after LA addition, which implies that the LA acts as asphaltene flocculants. The addition of DBSA decreases the size of asphaltene particles and generates new solvation layers, both of which favor the increase of heavy oil viscosity; the addition of LA increases the size of asphaltene particles and releases some liquid oils bounded by asphaltene particles, both of which favor the decrease of heavy oil viscosity. With the increase of R/A mass ratio, the stability of heavy oils increases while the viscosity enhancing/reducing efficiency of DBSA/LA decreases.
Journal of Petroleum Science and Engineering 12/2014; 124. DOI:10.1016/j.petrol.2014.10.004 · 1.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have developed electrically driven photonic crystals (PCs) from a quaternized polystyrene-b-poly(2-vinyl pyridine) (PS-b-P2VP) block copolymer which can form a one dimensional periodic lamellar structure. The variation of applied voltage from −4.50 to +2.36 V on the PCs can lead to color display over the entire visible region with a sub-second fast response, where the periodic structure swells from 4.3 to 7 times that at dry state. The fast response is attributed to the charging of the P2VP block. Besides, the photonic crystal exhibits a reverse volatility behavior, that is, as the applied voltage increases, the reflective peak wavelength decreases. Such fast switching PCs are facilely prepared with low driving voltage and good durability. The PCs are expected to find applications in information technologies.
[Show abstract][Hide abstract] ABSTRACT: Photonic crystal materials are developed from colloidal crystal fibers or beads. As the fibers have cylindrical symmetry, the fiber-composed PhCs show anisotropic angle independence. By contrast, the bead-composed PhCs display angle-independent structural colors because of the spherical symmetry of their bead elements.
Small 07/2013; 9(13). DOI:10.1002/smll.201203179 · 8.37 Impact Factor
Arundhati Roy, Tanmoy Saha, Marina L Gening, Denis V Titov, Alexey G Gerbst, Yury E Tsvetkov, Nikolay E Nifantiev, Pinaki Talukdar
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.