Solid immersion techniques

An incremental analysis of the contributions of various groups can be made by the heat of immersion technique. Heat of interaction of adsorbed layers with the equilibrium solutions can be directly determined by removing the equilibrated solid from the solution, drying it, and then re-immersing it into the equilibrium solution in the calorimeter. Lateral interactions can be determined from measurements at low and high coverages. 

Applications of the heat of immersion technique to determinations of polarity of surfaces, site heterogeneities, wetting of surfactants, hydrophilicity, and the interaction of specific groups from solution with solids are on the increase. The technique is certain to provide new and valuable information about the solid-liquid interface in the near future. 

Past strategies for increasing the storage capacity of optical disks were based on a reduction of A and an increase in NA, as can be seen from Table 12.1. In principle, a reduction in the spot size can be achieved with the aid of solid immersion lenses. This as yet not practically exploited technique, operating with a hemispherical or a Weierstrass superspherical lens placed near the recording medium (< 100 nm), yields a reduced spot size, S, as is evident from Eqs. (12-2) and (12-3), respectively, where n denotes the refractive index of the lens [8],... 

When a solid adsorbent is immersed in a binary mixture, the heat of wetting is greatly affected by the composition of the bulk phase, and values intermediate between the heat effects of wetting A, // and measured in the pure components 2 and 1, respectively, are obtained. This is the so-called immersion technique, which supplies direct information on the strength of the solid-liquid interaction with the mixture (Fig. 2) [41-44],... 

Stoeckli F, Hugi-Cleary D, Centeno TA. The characterization of solids by adsorption and immersion techniques and by ATM/STM. J Eur Ceram Soc 1998 18 1177-1185. 

A new technique based on electrocapillary phenomena at partially immersed solid metal electrodes has been developed by Jin-Hua et al. 146,147 jhe involves the detection of the rise of a solution... 

The terminology of L-B films originates from the names of two scientists who invented the technique of film preparation, which transfers the monolayer or multilayers from the water-air interface onto a solid substrate. The key of the L-B technique is to use the amphiphih molecule insoluble in water, with one end hydrophilic and the other hydrophobic. When a drop of a dilute solution containing the amphiphilic molecules is spread on the water-air interface, the hydrophilic end of the amphiphile is preferentially immersed in the water and the hydrophobic end remains in the air. After the evaporation of solvent, the solution leaves a monolayer of amphiphilic molecules in the form of two-dimensional gas due to relatively large spacing between the molecules (see Fig. 15 (a)). At this stage, a barrier moves and compresses the molecules on the water-air interface, and as a result the intermolecular distance decreases and the surface pressure increases. As the compression from the barrier proceeds, two successive phase transitions of the monolayer can be observed. First a transition from the gas" to the liquid state. 

Solids of different densities can be separated by immersing them in a fluid of intermediate density. The heavier solids sink to the bottom and the lighter float to the surface. Water suspensions of fine particles are often used as the dense liquid (heavy-medium). The technique is used extensively for the benefication (concentration) of mineral ores. 

Substantial improvements in LB techniques have been elfected—in terms of immersed or embedded boundary methods for dealing with moving and curved boundaries (impeller blades, solid particles) and of grid refinement techniques— which have had a positive impact on the fast proliferation of dedicated CFD tools. Here, too, the details of the computational techniques do matter. 

In the 1990s, Pawliszyn [3] developed a rapid, simple, and solvent-free extraction technique termed solid-phase microextraction. In this technique, a fused-silica fiber is coated with a polymer that allows for fast mass transfer—both in the adsorption and desorption of analytes. SPME coupled with GC/MS has been used to detect explosive residues in seawater and sediments from Hawaii [33]. Various fibers coated with carbowax/divinylbenzene, polydimethylsiloxane/divinylbenzene, and polyacrylate are used. The SPME devices are simply immersed into the water samples. The sediment samples are first sonicated with acetonitrile, evaporated, and reconstituted in water, and then sampled by SPME. The device is then inserted into the injection port of the GC/MS system and the analytes thermally desorbed from the fiber. Various... 

The mechanism of the iodide formation at platinum immersed in aqueous electrode was recently studied by laser-activated voltammetry in a channel flow cell system [161]. In this technique, solid deposits of iodine are removed from the electrode continuously by short nanosecond high-power laser pulses. By removing deposits on electrode surfaces within a channel flow cell, the voltammetric measurements becomes time independent and data can be analyzed and modeled quantitatively. Laser activation using a 10-Hz pulsed Nd YAG 532-nm laser was shown to remove bulk iodine from the electrode surface so that under sustained pulsed... 

These drawbacks can be avoided to a large extent, using the voltammetry of microparticles—a technique involving solid state electrochemistry where down to about 10 to 10 mol of sample [74-78] can be transferred by abrasion into the surface of an inert electrode, usually paraffin-impregnated graphite electrodes, and the electrode is later immersed in a suitable electrolyte for recording its voltam-metric response. The response of this sample-modified electrode, consisting of the reduction or oxidation of the solid materials, becomes phase-characteristic. 

To obtain fundamental information concerning interactions of surfaces with adsorbate molecules, particularly where other techniques are not suitable. Included are organics, molten metals, or solutions. It should be stressed now that heat-of-immersion values for a given solid in a variety of liquids can be misleading and that heat values as a function of the amount of preadsorbed wetting liquid are usually necessary. 

To rate the polarity of solid surfaces from their heats of immersion in simple organic liquids having different peripheral dipole moments. For the first time, this technique allows an experimentally derived number to be put on the average force field emanating from solid surfaces. 

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