In the case of making a glass, do we get different results in terms of structure, properties and etc. if we:
1- heat the mixed raw materials from room temperature to the desired temperature , i.e. 1325 degree C.
or
2- raise the temperature of furnace to 1325 degree C then put the mixed powder in it.
Thank you in advance for your time and consideration.
That may indeed differ due to the joint time-temperature influence in redox processes that may possibly affect the valence state of some elements, the likely distinct content of the melt in water and dissolved gases; and the distinct melting and finning process, where the partially molten raw materials may act as flux and disengaged gases may possibly favour finning to some extent. Possible composition deviation due to volatilization from melt may also act distinctly for both cases. Also the furnace atmosphere plays a role. Pre-calcinated raw materials are typically water and carbonate free.
It is also distinct to either melt glass from carbonate or oxide raw materials, from broken or powdered annealed glass (e.g. cullet), or from glass frit (glass melt poured in water).
Note, however, that many significant oxide glass properties are usually chiefly determined by its formulated oxide composition.
In practice, both variants are used for the same glasses: in the case of discontinuous glass melts (small melting furnaces with crucibles and others), the entire batch of the component mixture is heated from room temperature, and in the case of continuous glass melts in glass tubs, new small batches of the components mixture are dumped on glass melt into the running glass furnace by 1300-1600°C.
Glasses are inherently non-equilibrium structures. In the case of equilibrium structures the end state should not depend on the "path" followed, but it is not necessarily true for complex oxide glasses. Although the cooling rate is much more important in influencing the glass structure, variations may be expected aeven as a function of heating rate. Maybe in a technologiecal process, where the composition does nto vary and the components are well-defined, perhaps a sudden heaitn may also do, as the final structure can be opitmalized for this process, but in reasearch it is advisable first to use gradual heating ant o observe the processes (e.g. by TGA/DTA).
- Badges
- Science topic
- Similar topics
- Engineering
- Materials Engineering
- Powders