Inorganic encapsulation

This problem can easily be solved by using stabilized aluminum pigments. Pigments inhibited with phosphoorganic compounds, chrome treatments or by organic or inorganic encapsulation are commercially available. Further possibilities are published in Ref [5.183]. 

For inorganic encapsulation the possibility of electrochemically depositing silicon and then converting it irreversibly to silicon dioxide has been investigated. The primary reaction is the electrochemical reduction of trichlorosilane to silicon. The reaction is done in tetrahydrofuran under inert atmosphere. 

Silicon dioxide and silicon nitride which have previously been described on Sect. 3.1.1 to 3.1.3 are commonly used inorganic encapsulants. (See Sect. 3.1.1 to 3.1.3). 

Inorganic Materials. Sol—gel chemistry involves first the formation of a sol, which is a suspension of soHd particles in a Hquid, then of a gel, which is a diphasic material with a soHd encapsulating a solvent. A detailed description of the fundamental chemistry is available in the Hterature (2—4). The chemistry involving the most commonly used precursors, the alkoxides (M(OR) ), can be described in terms of two classes of reactions ... 

Applicability Surface encapsulation (macroencapsulation) is appropriate for both organic and inorganic wastes. 

The aim of this chapter is to encapsulate the work performed on inorganic PLC dnring the last 25 yr. 

Biocides are by their nature intrinsically toxic, in this respect any adventitious release to the environment requires an assessment of the relative risk posed. The 5th Environmental Action Plan of the EU is committed to a substantial reduction in the use of biocides. In particular, the Biocidal Products Directive (98/08/EC) is concerned with controlling biocidal products in the market place. Compliance with this directive is required from all member states by 14th May 2000. In this context, a strategy to control the release of biocides is timely, if continued protection is to be afforded to industry and consumer alike. One approach to controlling the release of biocide is to encapsulate in an inert inorganic framework, prior to incorporation in the coating.1... 

Macro encapsulation in plastic containers is widely used, usually for inorganic PCM. Examples of macro encapsulation are shown in Figure 113 (plastic... 

Figure 115. Macro encapsulation in capsule stripes as produced by TEAP/Australia and Dorken/Germany for inorganic PCM.

At this moment, the price of the used granular PCM exceeds 10 EURO/kg due to the test production stage. Our calculation showed the cost payback time can be less than 10 years when the PCM cost would be reduced to 4 EURO/kg under the electrical utility rate condition in Japan. Further cost reduction will be needed to promote the actual system. In addition we have to care of flammability of paraffin wax as PCM in use of inside the buildings. Fortunately, PCM is placed under the OA floor board made of fireproof cement-mortal and above the concrete slab in this system. It may not have any problems under the Fire Defense Law in Japan. However, further development of noninflammable PCM granules, for example micro encapsulation of mixture of inorganic and organic PCM, is required. 

Layered inorganic solids have been used for site isolation, for example, nickel phosphine complexes confined within the interlayer spaces of sepiolite have been used as olefin hydrogenation catalysts [63], and similarly there has been the encapsulation of metal complexes into zirconium phosphates [64], The principal idea is illustrated in Figure 5.8. The metal complex can be encapsulated by covalent means (a) or by non-covalent interactions (b). 

Common to all encapsulation methods is the provision for the passage of reagents and products through or past the walls of the compartment. In zeolites and mesoporous materials, this is enabled by their open porous structure. It is not surprising, then, that porous silica has been used as a material for encapsulation processes, which has already been seen in LbL methods [43], Moreover, ship-in-a-bottle approaches have been well documented, whereby the encapsulation of individual molecules, molecular clusters, and small metal particles is achieved within zeolites [67]. There is a wealth of literature on the immobilization of catalysts on silica or other inorganic materials [68-72], but this is beyond the scope of this chapter. However, these methods potentially provide another method to avoid a situation where one catalyst interferes with another, or to allow the use of a catalyst in a system limited by the reaction conditions. For example, the increased stability of a catalyst may allow a reaction to run at a desired higher temperature, or allow for the use of an otherwise insoluble catalyst [73]. 

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