CERAMICS, GLASS AND REFRACTORIESREFRACTORIES

DR KASSIM AL-JOUBORYUNIVERSITY OF TECHNOLOGY

BAGHDAD - IRAQ

2) Materials Structure

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٢

Electronegativity X - is a measure of the strength with which an atom in a molecule attracts electrons

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٣

energy (kJ/mol)BondType of bond Ionic 50–1000Covalent 200–1000Metallic 50–1000van der Waals 0.1–10Hydrogen 10–40

The building criteria for the crystal structure are Maintain neutralityMaintain neutralityCharge balance dictates chemical formula Achieve closest packing

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٤

IONIC CERAMICS

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٥

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٦

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٧

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٨

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq٩

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٠

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١١

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٢

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٣

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٤

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٥

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٦

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٧

STRUCTURE OF CILICATES

The general nature of silicate structures is the connection of the SiO4

4- tetrahedra. Additional oxides tend to break up the continuity of these tetrahedra. The remaining connectedness may be in the form of islands, chains or sheets:•Network silicate structures – these structures connect all 4 corners of the SiO4

4- tetrahedra to form a network. The Oxygen atoms are shared which accounts for the overall chemical formula of SiO2 not SiO4. of SiO2 not SiO4. •Island silicate structures – when positive ions bond with the oxygens of the SiO4

4- tetrahedral

•Chain or ring silicate structures – when 2 corners of each SiO44-

tetrahedra are bonded with corners of other tetrahedra with unit chemical formula SiO3

-2.•Sheet silicate structures – when 3 corners in the same plane of a silicate tetrahedron are bonded to the corners of 3 other silicate tetrahedra with chemical unit Si2O5

-2.Dr. Kassim Al-joubory - University of

Technology - Baghdad - Iraq١٨

Dr. Kassim Al-joubory - University of Technology - Baghdad - Iraq١٩

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