Colloidal silicon oxide

Colloidal anhydrous silica (colloidal silicon oxide) and magnesium stearate are used as lubricants in the preparation of capsules, tablets and powders (see Sect. 4.4.3). Addition of lubricants in the preparation of capsules, powders and tablets usually leads to a smoother fill of the capsules, or the moulds. An additional advantage is the reduction of the losses as a result of the elimination of the static charge of the powder mixture. 

Excipients play a key role in oxidation, either as a primary source of oxidants, trace amounts of metals, or other contaminants. Auto-oxidation of diethylstilbes-terol to the peroxide and conjugated quinone degradation products was attributable to the presence of colloidal silicon dioxide, used as a glidant in solid oral dosage forms [48]. This was ascribed to the fact that silicon dioxide can act as a Lewis acid (an election acceptor or oxidising agent), under anhydrous conditions. 

Clay Colloids. Three clay minerals are important components of the clay colloid fraction of soils, namely, montmorillonite, illite, and kaolinite (Adams, 1973). Mont-morillonite consists of one layer of aluminum oxide between two layers of silicon oxide (Figure 11.2). An important feature of this mineral is its multilayer arrangement, which permits smaller molecules such as pesticides to penetrate between them. This is referred to as an "expanding lattice" clay. Illite is also a three-layer clay but it does not form multilayers. Kaolinite is a two-layer mineral of aluminum oxide and silicon oxide. 

Nanoceramic particulates have been employed for the CMP process. The interactions of the ceramic particulates with organic additives, pad materials, and the wafer during the CMP process should be considered from the viewpoint of colloidal science. The surfaces to be polished involve silicon oxide and metals. 

Although it does not effectively protect ascorbic acid against oxidative degradation, colloidal silicon dioxide was found to increase the yield of spray-dried powder.f ... 

By using modified colloidal particles as templates, silicon oxide macroporous materials with uniform submicrometer-sized pores can be synthesized.[14] Modified polystyrene emulsion microspheres (200 1000 nm) can be electronegative (sulfates) or electropositive (amidines). After these microspheres are packed in an orderly fashion, they can interact with surfactants and silicon oxides to form macroporous solid composites, and further to form macroporous materials after the removal of the templates by calcination. The sizes of the macropores in the products range from 150 to 1000 nm. Macroporous Ti02 can also be prepared in a similar way. 

Ermakova, L.E., Sidorova, M.P., and Smirnov, V.M., Isoelectric point of silicon oxide particles coated by monolayers of oxides of titaninm and aluminum. Colloid J., 59, 523, 1997. 

The reaction of Eq. 16 is the chemistry that occurs during the sol-gel process, used to prepare colloids, films, or monoliths of porous silica from solution precursors (Brinker and Scherer 1990). This reaction explains why elemental silicon does not corrode appreciably at pH values <7 the oxide is insoluble at low pH and so provides a protective, passivating layer. The same is not tme in highly basic solutions here the solubility of silicon oxide drives sdicon dissolution by Eqs. 9 and 10. 

Ankerfors C, Ondaral S, Wagberg L et al (2010) Using Jet mixing to prepare polyelectrolyte complexes complex properties and their interaction with silicon oxide surfaces. J Colloid Interface Sci 351 88-95... 

Figure 23. Processing flow for 3-D electrode array fabrication using silicon micromachining with colloidal filling of the electrode material. The six steps are identified as the following (i) patterned photoresist (PR) on silicon substrate, (ii) PR removal after DRIB micromachining, (iii) insulate silicon mold by oxidation, (iv) colloidal electrode filling material centrifuged into the mold, (v) silver epoxy added to provide mechanical stability and electrical contact, (vi) the electrode flipped over and released from the mold by immersion in a TEAOH solution.

In addition to the soluble chemical species and possible solid phase species described in the previous sections no discussion on speciation can be complete without the consideration of surface species. These include the inorganic and organic ions adsorbed on the surface of particles. Natural systems such as soils, sediments and waters abound with colloids such as the hydrous oxides of iron, aluminium, manganese and silicon which have the potential to form surface complexes with the various cationic and anionic dissolved species (Evans, 1989). 

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