Microbeads composition

Apart from manifold structures, carbons can have various shapes, forms, and textures, including powders with different particle size distributions, foams, whiskers, foils, felts, papers, fibers [76, 77], spherical particles [76] such as mesocarbon microbeads (MCMB s) [78], etc. Comprehensive overviews are given, for example in [67, 71, 72], Further information on the synthesis and structures of carbonaceous materials can be found in [67, 70, 72, 75, 79]. Details of the surface composition and surface chemistry of carbons are reviewed in Chapter II, Sec. 8, and in Chapter III, Sec. 6, of this handbook. Some aspects of surface chemistry of lithiated carbons will also be discussed in Sec. 5.2.2.3. 

The silica microspheres provide some diversity but not enough for many complex discrimination tasks. To introduce more sensor variety, hollow polymeric microspheres have been fabricated8. The preparation of these hollow microspheres involves coating silica microspheres by living radical polymerization, using the surface as the initiation site. Once the polymer layer forms on the silica microbead surface, the silica core is removed by chemical etching. These hollow spheres can be derivatized with the dye of interest. The main advantage of these polymer microspheres is the variety of monomers that can be employed in their fabrication to produce sensors with many different surface functionalities and polymer compositions. 

Carbon-matrix composites, 26 751 Carbon microbeads, phenolic resins in,... 

There is a wide range of morphologies and compositions of polymeric microspheres. Core-shell microbeads can be created by sequentially polymerizing vinyl monomers, typically methacrylates and styrene. Each layer may consist of a homopolymer or a copolymer in the copolymers multifunctional vinyl monomers (e.g., diacrylates and divinylbenzene) may be used to create a cross-linked material. An optional final step can be grafting of functional groups to the surface in order to enhance compatibility to the surrounding medium. 

Another high-temperature approach for generating silicon/carbon composites is to deposit silicon particles on carbon or vice versa using CVD. Xie et al. [44] reported the deposition of silicon on mesocarbon microbeads (MCMB) by CVD of silane at 450°C and 500°C, but only a very small amount of silicon actually deposited on the MCMB. The material also demonstrated a very high (55%) irreversible loss. Vacuum deposition of nanometer-sized silicon particles on graphite surfaces has also been reported [45, 46]. The as-prepared anode showed an... 

Table 4.7 provides information on the composition of microbeads used in skin cleansers. 

Subban, R.H.Y. and Arof, A.K. (2004) Charge-discharge characteristics of LiCo02/mesocarbon microbeads battery with poly(vinyl chloride)-based composite polymer electrolyte. /. Power Sources, 134,211-221. 

Qjr depends on the electrolyte type (solvent and salts), the impurity level of the carbon and the electrolyte, the real surface area of the carbon including inner pores which the electrolyte can enter, the surface morphology, and the chemical composition of the carbon. It typically decreases in the order powders > microbeads > fibers. Impurities such as acids and alcohols, water, or heavy metals may contaminate the SEI, causing side-reactions [1, 2] such as hydrogen evolution and electrolyte reduction this results in larger Qjr values [99, 100]. 

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