Dispersions structure

Okamoto, M., Morita, S., Kim, H.Y., Kotaka, T. and Tateyama, H. 2001. Dispersed structure change of smectic clay/polyjmethyl methacrylate) nanocomposites by copolymerization with polar comonomer. Polymer 42 1201-1206. 

Cl Disperse Structure Diffusion coeff. x 1015 (m2/s) Rate constant... 

To obtain more detailed information on the ultrastructure of lipid dispersions and the morphology of the particles, electron microscopy is usually performed on replicas of freeze fractured or on frozen hydrated samples. These techniques aim to preserve the liquid-like state of the sample and the organization of the dispersed structures during preparation. By using special devices, the sample is frozen so quickly that all liquid structures, including the dispersion medium, solidify in an amorphous state. 

A half century ago, researchers described foams as disperse structures that contain a colloidal liquid, such as a protein solution, as the dispersion medium and a gas or air as the disperse phase ( ], ) The factors principally involved... 

The facts that we have explicitly included the intraparticle interference function P[Q) in the analysis of scattering intensities and that it is accessible experimentally allow us to characterize colloidal dispersions structurally in more detail than we have been able to so far. In order to understand this, we need to understand clearly what we mean by small or large values of 6 or s and how they affect the behavior of P(6). This will also help us to understand how (and why) it is possible to combine light scattering with x-ray or neutron scattering to study structures of particles and their aggregates. 

The stability and the structure of dispersions (structure here means the spatial organization of the colloidal particles) are topics of considerable research activity currently there is a lot that we do not know despite the long-standing focus on these topics in colloid science. The first step in approaching problems in this area is to study the origin and the nature of the interparticle forces and how they affect coagulation in dilute dispersions. This is what we focus on in this chapter. 

W/cm2. The FWHM of the strong peak (I2) was as small as 1.6 meV. The free-exciton peaks (A, B) could also clearly be observed. In addition, emission denoted by A2 in the higher energy region could clearly be seen and it is well-resolved into three peaks. FIGURE 5 shows a reflectance spectrum for the same sample at 5 K. Two sharp dispersive structures of A, B and C excitons can be seen. Furthermore, the first excited state (n = 2) transition of A and B excitons (A2, B2) can also be clearly observed. 

This value can be relatively low, nc - 2-4 in the initial aggregates.3 An increase in nc in the concentrated suspensions, and the shortening of distances between particles with increasing Csi02, affect the dispersion structure with time. Therefore, gelation of the concentrated dispersion (at 293 K) occurs faster, e.g. at Cs o2 = 16.7 wt.% in 2 days, than at Cs o2 <8 wt.%. Sonication leads to a lower turbidity of the suspensions compared to suspensions made from ball-milled silicas because of a different size of residual aggregates... 

Since a sequence of dispersion structures in bulk dispersions has been correlated with flooding results, the dependence of dispersion structure on phase behavior is also briefly reviewed. This leads to a discussion of phase behavior and its dependence on surfactant structure and other thermodynamic parameters. 

The cell tests consisted of three steps (1) In the first step, the cell was charged with approximately equal volumes of CO2 and an aqueous solution of the test surfactant in reservoir brine. The desired behavior was formation of an emulsion-like dispersion of the C02-rich phase in the aqueous phase. (2) In the second step, a small amount of reservoir oil was added. Desirable surfactants formed three-phase dispersions in which both the C02 rich and oil-rich phases were dispersed in the aqueous phase. (The crude oil was not miscible with CO2.) (3) In the third step of the test, the amount of oil in the cell was increased until it was somewhat larger than the volumes of CO2 and of aqueous phase. Although relatively few surfactants passed this third step, the desired dispersion structure was believed to be droplets of the C02-rich phase dispersed in the continuous oleic phase, with films of aqueous surfactant solution encasing the dispersed droplets (42,43, S. L. Wellington, Shell Development Company, personal communication, November 13, 1987). "Foaminess" tests performed under these conditions correlated with the results of flooding experiments. Both nonionic alkoxylated surfactants and their anionic sulfonated derivatives were tested by these methods (42,43). 

Usually, the liver contains 0.8-1.5% of its wet weight in the form of extractable, finely dispersed structural fats, which cannot be detected by normal histological techniques. Under the light microscope, the liver fat, which is mainly made up of small droplets of triglycerides, only becomes visible when an increase to >2-3% occurs. Above this value, hepatocytes register this event as a pathological process per se. 

Finally, DFT calculations [83] for different alkali coverages also provided an explanation for another unexpected property of alkali adsorption on aluminum, namely that many of the structure develop by island growth, even when no intermixing occurs with the substrate [51]. It was found that depolarisation of the adsorbate dipoles occurs already at quite low coverages, thereby reducing the tendency to form dispersed structures. 

The dispersion structure of the blends both in the melt and in the solid state was imaged partly by light microscopy (LM), and partly by scanning (SEM) and transmission electron microscopy (TEM). Wide-angle X-ray scattering (WAXS), Infrared (IR) measurements, and torsional pendulum analysis at IHz were performed too. 

It was the aim of the present paper to show that crystallization in incompatible polymer blends can exhibit a lot of peculiar effects beside the classical well known physical and physico-chemical phenomena. The effects considered here, in particular, are due to the dispersion structure of such blends, and to the changes in the crystallization nucleation conditions which are such caused. They are important from a physical, a material scientific, and a technological point of view as well. 

In Fig. 10, we plot the absorption rate Wn as a function of 8 for p 0.95 and different ft. When ft / 2A the absorption rate exhibits the familar Mollow absorption spectrum [38] with small dispersive structures at 8 = fl The absorption rate changes dramatically when ft = 2A. Here, the dominant features of the rate are emissive and absorptive components at 8 = ft, indicating that at 8 = —ft the weaker field is absorbed, whereas at 8 = ft is amplified at the expense of the strong field. The weaker field is always absorbed (amplified) at 8 = —ft (8 = ft) independent of the ratio r = Ti/I between the spontaneous emission rates 14 and 14. We illustrate this in Fig. 11, where we plot the absorptive rate for different values of r. The absorptive (emissive) peak remains absorptive (emissive) independent of the ratio r. 

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