Glass-ceramics are polycrystalline materials produced through controlled crystallization of base glass, producing a fine uniform dispersion of crystals throughout the bulk material.
Crystallization is accomplished by subjecting suitable glasses to a carefully regulated heat treatment schedule, resulting in the nucleation and growth of crystal phases.
In many cases, the crystallization process can proceed to near completion, but in a small proportion of processes, the residual glass phase often remains.
Glass-ceramic materials share many properties with both glasses and ceramics. Glass-ceramics have an amorphous phase and one or more crystalline phases and are produced by a so-called
“controlled crystallization” in contrast to a spontaneous crystallization, which is usually not wanted in glass manufacturing.
Glass-ceramics have the fabrication advantage of glass, as well as special properties of ceramics.
When used for sealing, some glass-ceramics do not require brazing but can withstand brazing temperatures up to 700 °C.
Glass-ceramics usually have between 30% [m/m] and 90% [m/m] crystallinity and yield an array of materials with interesting properties like zero porosity, high strength, toughness, translucency or opacity,
pigmentation, opalescence, low or even negative thermal expansion, high temperature stability, fluorescence, machinability, ferromagnetism, resorbability or high chemical durability, biocompatibility,
bioactivity, ion conductivity, superconductivity, isolation capabilities, low dielectric constant and loss, corrosion resistance, high resistivity and break-down voltage.
These properties can be tailored by controlling the base-glass composition and by controlled heat treatment/crystallization of base glass. In manufacturing, glass-ceramics are valued for having the
strength of ceramic but the hermetic sealing properties of glass.
Admission Requirements for Glass / Ceramics Technology
Biology/Agricultural Science/Mathematics, Physics and Chemistry and two others from:
- Biology/Agricultural Science
- Technical/Engineering Drawing
- Fine Art
- Basic Electricity
- Further Mathematics
Plus a minimum of pass grade in English Language.
- English Language,
- Fine Arts or Chemistry
Nigerian Polytechnics Offering Glass / Ceramics Technology
Below is the List of Polytechnics Offering Glass / Ceramics Technology in Nigeria
Akanu Ibiam Federal Polytechnic Unwana
Akanu Ibiam Federal Polytechnic Unwana, P.M.B 1007, Afikpo, Ebonyi State is a Federal Polytechnic Established in 1981.
Auchi Polytechnic, Auchi
Auchi Polytechnic, Auchi, Edo State is a Federal Polytechnic Established in 1973.
Federal Polytechnic Ado Ekiti
Federal Polytechnic Ado Ekiti, Ekiti State is a Federal Polytechnic Established in 1977.
Institute of Management and Technology
Institute of Management and Technology, Enugu, P.M.B 01079, Enugu, Enugu State is a State Polytechnic Established in 1965.