There glass ceramic it’s a polycrystalline material shatterproof and corrosion resistant, developed in 1952 due to a malfunction of the thermostat of a furnace that brought the glass inside it above 1000 °C. Chemist SD Stookey found the glass covered with a fine white layer and observed that it did not exhibit the characteristic brittleness of glass. This is how glass ceramic was born, a material capable of having the best characteristics of glass and of ceramic thanks to the presence of an amorphous phase, typical of glass, and a crystalline phase, typical of ceramics. They are produced through controlled recrystallization.
What material is glass ceramic and how is it produced
Glass ceramic has a partly glassy (therefore amorphous) and partly crystalline structure. Its manufacturing initially consists of the typical steps of glass production: an amorphous, transparent and hard but fragile material. The glass is then heated to high temperatures (between 750-1150°C) to induce the partial recrystallization. It can be defined as glass ceramic when the fraction of the crystalline phase exceeds 50% (in some cases it can even reach 95%), and usually to favor it, nucleating agents are added which also help to control the process.
During the growth of crystalline grains, insoluble elements or compounds are added which guarantee fundamental properties, some examples are gold, silver, platinum or palladium (metals) or even titanium oxide or phosphoric anhydride (non-metals). The main types of glass ceramics are distinguished according to the compounds added:
- Oxide of THEithium, oxide of TOaluminum and oxide Silicium: LAS, resistant to thermal shock, zero thermal expansion factors and high chemical-mechanical properties;
- Oxide of Magnesium, oxide of TOaluminum and oxide Silicium: MAShigh mechanical resistance at high temperatures;
- Oxide of Zinco, oxide of TOaluminum and oxide Silicium: ZAS, used in the mechanical sector;
From induction hobs to space telescopes: why its use is increasingly frequent
The property from the glass ceramic they really make it a material versatile. For example, it can withstand extreme temperature changes without breaking, making it ideal for applications involving high temperatures, such as induction hobs and fireplaces. Another notable feature is the scratch-resistant surface, making it perfect for environments where wear and tear is a problem, such as dental reconstruction.
Furthermore, glass ceramic has a almost zero thermal expansion coefficientthat is, it remains stable and does not deform, even with large temperature variations (up to approximately 700 °C). Finally, the aesthetic aspect also plays an important role: glass ceramic is available in many finishes and colours, adapting perfectly to modern and design projects.
But glass ceramic is not only used in design objects or in the kitchen. In astronomy, it is used in high-precision instruments such as the Hubble Space Telescopethanks to its dimensional stability and heat resistance. The aerospace industry also uses glass ceramics for components exposed to extreme temperatures. Today, many glass ceramics for common objects are produced recycling industrial glassthus representing a more sustainable choice for the environment.
