High-energy colloids

The complexed halide atoms are produced by high energy radiation in solutions of colloids that contain halide anions X and are saturated with nitrous oxide. Hydrated electrons formed in the radiolysis of the aqueous solvent react with NjO according to NjO -f e -f H O - Nj -t- OH -I- OH to form additional OH radicals. Ions X are oxidized by OH, the atoms X thus formed react rapidly with X to yield XJ radicals. 

Removal to sediments. Removal of surface-reactive trace elements from the oceans readily occurs by adsorption onto settling particles, and this process is most pronounced in the typically high-energy, particle-rich estuarine environment. Particles are supplied by rivers, augmented by additions of organic material generated within the estuary. Also, floes are created in estuaries from such components as humic acids and Fe. The interaction between dissolved and colloidal species is enhanced by the continuous resuspension of sediments in... 

Successful systems have used colloidal platinum as an efficient catalyst for the multi-electron reduction process by which hydrogen is produced. The platinum acts as a charge pool in that electrons from one-electron processes are trapped, to be later delivered to the substrate in a concerted manner, thus avoiding formation of high-energy intermediates (Figure 12.12). 

Example 6 Emulsification of Nonmiscible Liquids. Liquid/liquid emulsions consist of two (or more) nonmiscible liquids. Classic examples of oil in water (0/W) emulsions are milk, mayonnaise, lotions, creams, water-soluble paints, and photo emulsions. As appliances serve dispersion and colloid mills, as well as high-pressure homogenizers. All of them utilize a high-energy input to produce the finest droplets of the disperse (mostly oil) phase. The aim of this oper-... 

We have already defined the stability ratio operationally. A stable colloidal dispersion is characterized by a high-energy barrier, that is, by a net repulsive... 

As high-energy electrons pass through an aqueous colloidal suspension of particles, energy is lost via electronic interactions in both the liquid and solid phases in a ratio determined by their relative electron densities and concentration. Thus, as the percentage of solid material increases, so does the fraction of energy deposited in the solid phase. It is common to conduct radiolytic experiments at constant volume (to ensure constant geometry relative to the radiation source). Thus, the dose absorbed in the sample increases with the increase of total density of the sample. This is shown in Fig. 2 as the upper solid curve. 

A situation peculiar to colloidal systems is that in which the free-energy curve has the form of Figure 2.8(d). Here aggregation is prevented by a high energy barrier, but preceding this is a relatively shallow minimum - called a secondary minimum to distinguish it from the deep primary minimum. If the depth of the... 

In the natural environment photolytic reactions leading to the production of high-energy unsaturated compounds (see Zika, Chapter 10) may play a role in the production of polymeric material in the euphotic zone, while on the other hand fluorescent substances may be degraded by sunlight excitation (Kramer, 1979). In deeper layers, adsorption onto colloids and further condensation of macromolecules may be determining processes. 

The high-energy input necessary for preparing multiphase polymer systems or other colloidal systems pushes these systems far from equilibrium at a critical concentration the energy input and the entropy export are so far above their critical values (i.e. they are supercritical) that a self-organisation process occurs in the form of a phase transition. This is the short, summarised main principle on which the new viewpoint [37] is based. 

The amphiphilic compounds used to stabilize aqueous colloidal dispersions of metals, semiconductors, and organic polymer particles are surfactants, broadly defined. The surfactant replaces the high energy of the particle-water interface with two lower energy interfaces of the surfactant with particles and of the surfactant with water. Amphiphilic polymers also stabilize colloidal dispersions by reducing the interfacial free energies of the system. 

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