Aluminum-modified silica sol

Alkali metal hydroxides, dissolution rate effect, 521-523f Alkoxides, formation of uniform precipitates, 451-464 Aluminum, silicic acid effect on adsorption in food, 612/ 613 Aluminum in biological systems, 604, 605f, 606 Aluminum-modified silica sol, formation, 62, 63/ Aluminum-silicon interactions in biology,... 

In a series of patent applications [28-31] Davies et al. show that the problems caused by high amounts of alkali metal ions could be overcome by using silica sols as the water-based binder instead of solutions of alkah silicates. The preferred sols had a particle size between 5 and 10 nm and a Si02/Na20 mole ratio of about 50 1. They also found that they could increase the pot life of the shop primer by using aluminum-modified silica sols. 

Aluminum-modified silica sol with a particle size of 12 nm in a pigmented ink-jet ink formulation gave a print with improved optical density and superior rub resistance compared with a reference ink [48]. 

Positive silica sols and alumina modified silica sols wherein the ultimate silica particles have been modified and/or made electrically positive by partially or completely coating the particle surface with aluminum compounds can also be used in the present invention as a source of amorphous silica. Such sols are described for example by G. B. Alexander and G. H. Bolt in U.S. Pat. No. 3,007,878 and... 

The industrial development of silica sol manufacturing methods is reviewed. Primary attention is focused on the preparation of monodispersed sols from water glass by the ion-exchange method. Details are given for variations of manufacturing process and for the characteristics of both the processes and sols obtained. Furthermore, the following surface modifications of particles are demonstrated silica sols stabilized with ammonia, amine, and quaternary ammonium hydroxide aluminum-modified or cation-coated silica sol and lithium silicate. Finally, future trends in silica sol manufacturing are discussed from the viewpoint of not only raw materials and improvement of the procedures but also the function of the silica sols and their particle shape. 

The continuous mullite fibers were first made by heat-treating the gel fibers spun from the sol prepared by hydrolyzing the stochiometric mixture of TEOS and acac-modified AIP (Tucker, 1990). The amorphous gel fibers were crystallized to mullite fibers above 1000°C. Thereafter, several cost-effective sol-gel methods of the mullite fiber formation have been developed. In one method, the mixture of silica sol and alumina sol prepared from aluminum salts were spun with the aid of polyethylene oxide (PEO) (Bhattacharya, 1996a). In others the stoichiometric mixture of inexpensive alumina sources (nitrate, acetates. 

The rate of silicate sol and gel formation is pH and water-alcohol-sensitive as is the solubility of the amorphous silica that is formed. Silica networks are based on (Si04) " tetrahedra modified by (O3 Si-O, M+) units and often addition of boron oxide, aluminum oxide, titanium IV oxide, or zirconium IV oxide. 

Her (324) prepared a series of sols modified with various amounts of aluminate. One series was made from an unmodified sol of 22 nm particles (Ludox TM) and another of 14 nm particles (Ludox HS). The coverage by aluminate ions ranged from 1.8 to 25% of the total silanol groups on the surface (assuming 8 SiOH nm ). Stabilization as an aluminate ion in the particle surface requires that each aluminum atom be surrounded by three oxygens linked to silicon, which means that no more than 25% of the surface silicon sites can be replaced by aluminum atoms. This assumes, of course, that the underlying silica surface is nonporous and not accessible to reaction with Al(OH)4" ions. 

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