Neutron scattering dispersions

Figure 4 Schematic vector diagrams illustrating the use of coherent inelastic neutron scattering to determine phonon dispersion relationships, (a) Scattering m real space (h) a scattering triangle illustrating the momentum transfer, Q, of the neutrons in relation to the reciprocal lattice vector of the sample t and the phonon wave vector, q. Heavy dots represent Bragg reflections.

Figure 3 Phonon dispersion curves obtained by inelastic neutron scattering revealing precursor behaviour prior to the 14M transformation in Ni-AI. The dip at q = 1/6 [110] (a) deepens upon cooling and (b) shifts under an external load .

In addition, theoretically calculated dispersion curves and Raman intensities have been reported as well as results of neutron scattering experiments [113, 115]. 

Flocculation studies (6) indicated that the mechanism of steric stabilization operates for the PMMA dispersions. The stability of PMMA dispersions was examined further by redispersion of the particles in cyclohexane at 333 K. Above 307 K, cyclohexane is a good solvent for PS and PDMS, and if the PS-PDMS block copolymer was not firmly anchored, desorption of stabilizer by dissolution should occur at 333 K followed by flocculation of the PMMA dispersion. However, little change in dispersion stability was observed over a period of 60 h. Consequently, we may conclude that the PS blocks are firmly anchored within the hard PMMA matrix. However, the indication from neutron scattering of aggregates of PS(D) blocks in PMMA particles may be explained by the observation that two different polymers are often not very compatible on mixing (10) so that the PS(D) blocks are tending to... 

Yurekli K, Mitchell CA, Krishnamoorti R (2004) Small-angle neutron scattering from surfactant-assisted aqueous dispersions of carbon nanotubes. J Am Chem Soc 126 9902-9903. 

The different microstructures, shown in Fig. 3, are highly dynamic aggregates. They can be detected by well established scattering techniques, like X-ray, light or neutron scattering [ 13]. Beside scattering techniques, the transitions between the microstructures can be detected from the changes of the viscosity of w/o-micro emulsion. For a diluted dispersion of spherical droplets without interactions, the relative viscosity is expected to obey the Einstein-relation ... 

Even the traditional methods discussed in this chapter can be used for concentrated dispersions through contrast matching. For example, silica particles coated with silane coupling agents in a refractive index-matched mixture of ethanol and toluene can be used in combination with visible probe particles to study the dynamics of particles in dense systems. In the case of microemulsions (Chapter 8), selective deuteration of a component (oil, water, or surfactant) can be used in neutron scattering experiments even to measure the curvature of the oil-water interface. 

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. 

Because there is no general microscopic theory of liquids, the analysis of inelastic neutron scattering experiments must proceed on the basis of model calculations. Recently1 we have derived a simple interpolation model for single particle motions in simple liquids. This derivation, which was based on the correlation function formalism, depends on dispersion relation and sum rule arguments and the assumption of simple exponential decay for the damping function. According to the model, the linear response in the displacement, yft), satisfies the equation... 

It is not possible to discuss all the methods available for characterizing foods critically and systematically in a single volume. Methods pertaining to interfaces (food emulsions, foams, and dispersions), fluorescence, ultrasonics, nuclear magnetic resonance, electron spin resonance, Fourier-transform infrared and near infrared spectroscopy, small-angle neutron scattering, dielectrics, microscopy, rheology, sensors, antibodies, flavor and aroma analysis are included. 

Neutron scattering is also useful for the study of adsorbed material on hydrosol particles. The neutron scattering length densities of hydrogen and deuterium differ considerably. By preparing a hydrosol in an appropriate H20/D20 mixture, it is possible to match the neutron scattering length densities of the dispersion medium and the core particles. The neutron beam thus sees only the adsorbed layer, the thickness of which can be estimated. Alternatively, the dispersion medium can be matched to the adsorbed layer to permit estimation of the core-particle size. 

Not any feature was observed in the single-magnon dispersion that would correlate with the lower-energy two-magnon peak in the inelastic neutron scattering measurements of the stripe-ordered nickelate Lai.69Sr0.3iNiC>4 also.311... 

In addition to light, x-ray and neutron scattering can be used to obtain size distribution information [79,80]. The latter two techniques can provide information on smaller dispersed species sizes, down to about 0.5 nm. 

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