Core coating, conductive

Figure 4. Conductive core coating by solvent dispersion process...

TABLE IV Comparison Of Energy Consumption For Coating Conductive Core With Liquid Silicone Rubber vs Silicone Rubber Dispersion... 

TABLE V Calculation Of Energy Required For Conductive Core Coating, LPS Process vs Solvent Dispersion Process... 

Recently it has been shown that the oxides of the platinum metals can have a higher corrosion resistance than the metals themselves , and have sufficient conductivity to be used as coatings for anodes, e.g. with titanium cores. Anodes with a coating of ruthenium dioxide are being developed for use in mercury cells for the electrolysis of brine to produce chlorine , since they are resistant to attack if in contact with the sodium-mercury amalgam. 

Another method to synthesize hollow nanocapsules involves the use of nanoparticle templates as the core, growing a shell around them, then subsequently removing the core by dissolution [30-32]. Although this approach is reminiscent of the sacrificial core method, the nanoparticles are first trapped and aligned in membrane pores by vacuum filtration rather than coated while in aqueous solution. The nanoparticles are employed as templates for polymer nucleation and growth Polymerization of a conducting polymer around the nanoparticles results in polymer-coated particles and, following dissolution of the core particles, hollow polymer nanocapsules are obtained. 

Similarly, Pd, Ag, and Pd-Ag nanoclusters on alumina have been prepared by the polyol method [230]. Dend-rimer encapsulated metal nanoclusters can be obtained by the thermal degradation of the organic dendrimers [368]. If salts of different metals are reduced one after the other in the presence of a support, core-shell type metallic particles are produced. In this case the presence of the support is vital for the success of the preparation. For example, the stepwise reduction of Cu and Pt salts in the presence of a conductive carbon support (Vulcan XC 72) generates copper nanoparticles (6-8 nm) that are coated with smaller particles of Pt (1-2 nm). This system has been found to be a powerful electrocatalyst which exhibits improved CO tolerance combined with high electrocatalytic efficiency. For details see Section 3.7 [53,369]. 

The liquid-phase reaction kinetics of doped molecules in silica nanomatrixes was conducted using the metalation of meso-tetra (4-Ai,Ai,Ai-trimethylanilinium) porphyrin tetrachloride (TTMAPP) with Cu(II) as a model. To demonstrate the effect of the silica nanomatrix on the diffusion, pure silica shells with varied thickness were coated onto the same silica cores, which doped the same amount of TTMAPP molecules. The Cu(II) from the suspension could penetrate into the silica nanomatrixes and bind to the TTMAPP. The reaction rate of TTMAPP metalation with Cu(II) was significantly slower than that in a bulk solution. The increase in the thickness of the silica resulted in a consistent decrease of reaction rates (Fig. 8). 

It is frequently desirable to cover a given particle with a layer of different chemical composition. In doing so, one can alter the surface reaction sites, as well as optical, magnetic, conductive, and other properties of the dispersed matter. Finally, if a material of a given particle shape is needed, but cannot be obtained directly, it is possible to use cores of a different composition but of the desired morphology and coat them with a shell of the chemical compound of interest. This approach combines the needed overall morphology with the surface reactive sites of choice. 

In addition to adhering strongly to substrates, it is often both desirable and advantageous in many applications to form coatings that are readily removable from a substrate with a minimum amount of force. In the wire sheathing industry, it is often desirable to have sheaths which can be readily removed, or stripped, to allow easy access to the conductive core for making electrical contact with the wires. 

For coated products, since this is the finished form, sampling and testing should also be conducted. The emphasis is usually on the cores, however, where the sample identity across the batch is known and can be evaluated. At the coated stage, the effect of the coating solution on dissolution is probably of most interest. Individual coating pans, either all of them or some portion of them, should be sampled and tested, with pan number identity maintained. 

The first experiments were conducted using stearyl alcohol (C18H38O, obtained from Merck) as the coating material and different core materials (see Table 1). The melting point... 

As shown in Table 10.2, the impurity peak at RRT 0.38 was specific to active and placebo cores and hlm-coated tablets stored with desiccant. An investigation was conducted using desiccant extracts prepared using the sample dissolving solvents. 

A commercial controlled release, polymer coated spheroid/bead product (Slophyllin, Rona) was used as received. The spheroids were microtomed to expose a cross-sectional area of the inner drugladen core and the surrounding polymer film coating, and subsequently mounted on the sample holder using conductive silver paint with the microtomed surface uppermost. 

---