Silicate solutions characterization techniques

Once again, NMR appears so far the most sensitive and non-invasive characterization technique, but its potential seems not to be as great as in the study of silicate solutions. Figure 6 shows that all the Si NMR lines of an aluminosilicate solution are broadened with respect to their originating silicate solution [19]. 

As of the mid-1990s, soluble sihcates are used primarily as sources of reactive siUca (57%), in detergency (qv) (23%), in pulp (qv) and paper (qv) production (7%), for adhesives and binders (5%), and in other appHcations (8%). The stmcture and chemistry of solutions containing polymeric siHcate species have been characterized using modem analytical techniques. This improved understanding of siHcate speciation contributes to the development of new markets. Thus, the sodium silicates constitute a versatile, stable, and growing commodity and are ranked among the top 50 commodity chemicals. 

The development and application of multidimensional solid state homo- and heteronuclear correlation (HETCOR) NMR techniques have lead to an increasingly important role in structure solution of zeolitic materials and have had many practical applications in the detailed structural characterization of completely siliceous zeolites[6,7] and AlPOs.[8-ll] However, HETCOR NMR is not readily applicable to aluminosilicates... 

Amorphous silica-aluminas are high-surface-area materials that can be prepared by co-precipitation or sol-gel techniques from solutions containing sodium silicate and sodium aluminate. Because of their high surface acidities they are potent hydrocarbon cracking catalysts, but their activity is strongly dependent on the silica/alumina ratio and on the method of preparation. Solid-state NMR studies have addressed the structural origins of these variations and have served to characterize the surface acidities. 

William et al. (2005) reviewed various techniques for characterization and trends in the field of nanocomposites. These are new materials made with fillers, which have nanosize and have a big potential for applications in the automotive and aerospace industiy as well as in construction, electrical applications and food packing. There is a tremendous interest for using bio-nanoparticles in the new era of biocomposites by using synthetic and natural fillers in polymer nanocomposites. Aranda et al. (1998) studied the microwave-assisted blending-intercalation of ion-conductor polymers into layered silicates. They prepared organo-inorganic hybrid nanocomposites derived from poly(ethylene oxide) and montmorillonite silicate. They observed that ionic conductivity was enhanced as compared to samples prepared by intercalation from solution. 

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