What is the difference between colloidal silica and silica sol?

Link to Hebei Silicon Research Electronic Materials Co., L

Applied Material Solutions offers a variety of industrial chemical products. In addition to colloidal silica, we provide a selection of antifoams and defoamers, hydrophobic treated silica, and toll manufacturing services. You'll find our headquarters in Elkhorn, WI, while Burlington, WI, and Rockton, IL, are home to our manufacturing plants.

Here you'll learn the differences between fumed silica and colloidal silica, which are otherwise identical at the molecular level. While AMS is a manufacturer of colloidal silica, we are not outright a manufacturer of fumed silica. Instead, we take fumed silica and surface-treat it with silicone polymers to make it hydrophobic.

What Is Colloidal Silica?

Colloidal silica is a water-based, stabilized dispersion of amorphous silicon dioxide (aka silica) nanoparticles. Manufacturers produce colloidal silicathrough the polymerization of silica nuclei derived from silicate solutions. Polymerized under alkaline conditions, the silica nuclei convert into silica sols (solid particles) at the nano-scale and with a high surface area. The process then applies a charge to these silica sols, causing electrostatic resistance between each particle and creating a colloid'a type of stable dispersion.

These microscopic colloids remain suspended in a dispersion medium, typically water. What makes colloids different from other suspensions is their even distribution, without settling or separating. Colloids can be comprised of many types of solid, gaseous, and liquid substances within a dispersion media. In the case of colloidal silica, the colloid is a microscopic solid dispersed in water.

What Is Fumed Silica?

 

Fumed silica is an amorphous, nano-scale, powdered material. Fumed silica particles are formed by injecting air and hydrogen flames with silicon tetrachloride or other types of chlorosilanes. Like colloidal silica, fumed silica particles are extremely small and have large surface areas. Furthermore, fumed silica particles have the same molecular composition as colloidal silica particles, except that they are presented in powdered form as opposed to a stabilized liquid dispersion.

What Are the Applications of Fumed Silica and Colloidal Silica?

Fumed silica functions as a desiccant that thickens various substances. For example, food manufacturers may use it to thicken liquid food products or prevent caking in powdered products. Other potential applications for fumed silica include cosmetics, toothpaste, and fillers in silicone elastomers. It also adjusts viscosity, alters rheology and modifies the physical characteristics of paints, coatings, adhesives and sealants.

Similar to fumed silica, applications for colloidal silica include absorbing moisture in industrial settings with high moisture levels. Colloidal silica is also used to increase surface friction, facilitate the movement of materials, and as a binding agent.

Attributes of Fumed Silica and Colloidal Silica

Typical AttributesColloidal SilicaFumed Silica Physical StateLiquidPowder ConcentrationVariable - Often 6% - 50%Typically 100% CreationNucleation ReactionFlame Hydrolysis Common ApplicationsBinder, Densifier, CoagulantThickener, Stabilizer, Rheology Control Particle SizeVariable - Often 3 nm - 50 nmVariable - e.g. 5 nm - 20 nm Surface AreaVariable - Often 60 - 1,000 m2 /gVariable - e.g. 100 - 200 m2 /g Hydrophilic vs HydrophobicBoth. AMS manufactures hydrophilic colloidal silica.Both. AMS manufactures hydrophobic fumed silica.

Silicates From Applied Material Solutions

When selecting a colloidal silica or hydrophobic fumed silica, turn to Applied Material Solutions. We offer a wide variety of colloidal silica options, including winterized versions, and a versatile fumed silica in the form of our AMSil-F H22.

For more information about our silica products and other solutions, contact Applied Material Solutions today or call our offices at 262-723-.

Suspensions of fine amorphous silica particles in a liquid

Colloidal silicas are suspensions of fine amorphous, nonporous, and typically spherical silica particles in a liquid phase. It may be produced by Stöber process from Tetraethyl orthosilicate (TEOS).

Properties

[

edit

]

Want more information on hydrophilic silica? Feel free to contact us.

Usually they are suspended in an aqueous phase that is stabilized electrostatically. Colloidal silicas exhibit particle densities in the range of 2.1 to 2.3 g/cm3.

Most colloidal silicas are prepared as monodisperse suspensions with particle sizes ranging from approximately 30 to 100 nm in diameter. Polydisperse suspensions can also be synthesized and have roughly the same limits in particle size. Smaller particles are difficult to stabilize while particles much greater than 150 nanometers are subject to sedimentation.

Manufacture

[

edit

]

Colloidal silicas are most often prepared in a multi-step process where an alkali-silicate solution is partially neutralized, leading to the formation of silica nuclei. The subunits of colloidal silica particles are typically in the range of 1 to 5 nm. Whether or not these subunits are joined depends on the conditions of polymerization. Initial acidification of a water-glass (sodium silicate) solution yields Si(OH)4.

If the pH is reduced below 7 or if salt is added, then the units tend to fuse together in chains. These products are often called silica gels. If the pH is kept slightly on the alkaline side of neutral, then the subunits stay separated, and they gradually grow. These products are often called precipitated silica or silica sols. Hydrogen ions from the surface of colloidal silica tend to dissociate in aqueous solution, yielding a high negative charge. Substitution of some of the Si atoms by Al is known increase the negative colloidal charge, especially when it is evaluated at pH below the neutral point. Because of the very small size, the surface area of colloidal silica is very high.

The colloidal suspension is stabilized by pH adjustment and then concentrated, usually by evaporation. The maximum concentration obtainable depends on the on particle size. For example, 50 nm particles can be concentrated to greater than 50 wt% solids while 10 nm particles can only be concentrated to approximately 30 wt% solids before the suspension becomes too unstable.

Applications

[

edit

]

See also

[

edit

]

References

[

edit

]