Surfactant phase, crystallites

Transmission electron microscopy (TEM) has been an underutilized yet valuable too in particle size characterization of MC particles in LB films. Monolayer films of trioctylphosphine oxide-capped CdSe (18), spread as a monolayer on an aqueous subphase, were transferred to a TEM grid. A close-packed hexagonal arrangement of 5.3-nm (cr —4%) crystallites was found. TEM images were also obtained for HMP-stabilized CdS incorporated in BeH/octadecylamine films (79) and for CdS formed under an amine-based surfactant monolayer and transferred to a TEM grid (14). In one study, direct viewing of CdS and CdSe particles made from Cd2+-FA films on TEM grids was not possible due to poor phase contrast between the particles and the film (30). Diffraction patterns were observed, however, that were consistent with crystalline (3-CdS or CdSe. Approximately spherical particles of CdSe could... 

At temperatures just below the transition of C19 to the orthorhombic phase, penetration of C,2E04 is inhibited. However, the presence of the surfactant during the transition still affects the adhesion of the C19 crystallites to the IRE surface, resulting in some removal by the displacement mechanism. 

We examined the effect of surfactant removal by means of XRD. Fig.2 shows the wide-angle (WA) XRD patterns of mesoporous Ti02 obtained after different CTMACl removal procedures. The XRD patterns show the characteristic of anatase phase (JCPDS 21-1272). Moreover, highly crystalline mesostructure with minor brookite ( ) was obtained when samples were calcined. In fact, the strongest peak in the XRD is sharpened by the calcination at 773 K. On the other hand, the use of cyclohexane and soluble starch improves the cristallinity of the mesoporous Ti02- The crystallite size calculated by the scherer equation fi-om anatase (101) peak is about 23 nm... 

Very recently, Kluson et al. [268] prepared mesoporous titania by using a Triton X-lOO/cyclohexane/aqueous phase system with w = 1. The rationale behind the selection of such a low w value was that this amount of water should be mainly associated with the hydroxyl group of the surfactant and not compete with the oil phase for solvating the chain oxyethylene groups. Titanium isopropoxide was the source material for Ti. The titania crystallite size varied from 4.1 to 11.3 nm depending on the particle processing temperature. At 200 C, the product was amorphous to pseudoamorphous at 550"C, anatase started appearing, and rutile was found to appear in addition at 650"C. At 850°C, both anatase and rutile were obtained. 

Delfort et al. [337] probably showed for the first time that residual volatiles in the dispersed phase after completion of synthesis could be removed by evaporation to collect the product. In case of portlandite, Ca(OH)2, they first dispersed calcium hydride in a solution of the surfactant Ca-alkylarylsulfonate (Ca-salt of C-24 monoalkylarylsulfonic acid) in mineral oil. A solution of water in tetrahydrofuran was slowly added to it under vigorous stirring for several hours. This was followed by filtration and removal of volatile matter by vacuum evaporation. The conversion in the W/O microemulsions took place by rapid hydrolysis of the hydride. The crystallite size was 3 nm in the c-direction and 18 nm in the (a, b)-direction. 

Kim J, Montero G, Habibi Y et al (2009) Dispersion of cellulose crystallites by noniraiic surfactants in a hydrophobic polymer matrix. Polym Eng Sci 49 2054-2061 Kimura F, Kimura T, Tamura M et al (2005) Magnetic alignment of the chiral nematic phase of a cellulose microfibril suspension. Langmuir 21 2034—2037 Klemm D, Philipp B, Heinze T, Heinze U, Wagenknecht W (1998) Comprehensive cellulose chemistry. Wiley VCH, Chichester... 

A microemulsion is a thermodynamically stable three-component system two immiscible components (generally water and oil) and a surfactant molecule that lowers the interfacial tension between water and oil resulting in the formation of a transparent solution. Water-in-oil microemulsions involve dispersion of the aqueous phase as nanosized droplets (5-25 nm in diameter) surrounded by a monolayer of surfactant molecules in the continuous hydrocarbon phase. These micellar droplets exhibit a dynamic exchange of their contents, which further facilitates the reactions between reactants dissolved in different droplets. One can synthesize size-controlled crystallites by carrying out a wide variety of chemical reactions in nanodroplets using this micellar exchange. Different types of microemulsions are... 

SDS forms direct micelles in the bath. The surface of the micelles, formed by polar groups, constitutes a charged interface that may have an influence on precursor nucleation (favoured sites), on phase transformation (modification of zinc hydroxide surface reactivity by surfactants) and on ZnO nanocrystallites assemblies (adsorption of surfactant molecules on the crystallites faces). 

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