Porous glass

The specific properties and commercial availability of porous glass make it one of the most extensively researched and characterized amorphous solids.

They show a high chemical, thermal and mechanical resistance, which results from a rigid and incompressible silica network.

By extraction using mineral acids the soluble phase can be removed and a porous silica network remains.

You can generate various moulds, for example, irregular particles (powder, granulate), spheres, plates, sticks, fibers, ultra thin membranes, tubes and rings.

Using an initial glass composition, which lies on the line of anomaly, it is possible to attain a maximum decomposition, which is almost strainless.

The texture is influenced by the composition of the initial glass, which directs size and type of decomposition areas.

Furthermore, the texture of porous glasses is influenced by the concentration of the extraction medium and the ratio of fluid to solid.

Also, colloidal silica is solving in the sodium-rich borate phase, when time and temperature of thermal treatment are increased.

The fact that porous glasses can be produced in many different shapes is another advantage for application in industry, medicine, pharmacy research, biotechnology and sensor technology.

An adaptation of stationary phase for a separation problem is possible by a specific modification of the surface of the porous glass.

With the ability to form porous glasses as platelets, membrane technology is another important area of application.

Ternary Phase diagram in the sodium borosilicate system
Porous glass filled with water, sample about 1 mm thick, made by phase separation in a thermal gradient (high temperature on the right) of a sodium borosilicate glass, followed by acid leaching
Same porous glass as above, but dry. The increased difference between the refractive indices glass/air as compared to glass/water is causing greater whiteness based on the Tyndall effect .