Heat treatment of glasses Glass Product stresses resulting from inhomogeneous temperatures during ling (similar to an ring: heating glass above glass transition rature but below softening point then quench in an 9 Containers or oil bath o Light Bulb Glass The interior, cools later than outside. tries to contract while in a plastic state after exterior has already become rigid, Causes residual compressive stresses on surface and tensile es inside stress, making tempered glass less susceptible to fr wields, gl lenses, etc. Glass- Ceramics 5. Other Important Element .By heat treating glass into a polycrystalline Replace ceramics in some applications. makes stronger .A semimetallic element abundant on earth OPaque (gray or white) in color b Brittle, lightweight and chemically inactive at +After heating and forming into a desired geometry. it is cooled and reheated to crystallize at a high t Used to make glass and clay, alloying ingredient, density of nucleation sites .Efficient processing, close dimensional control and excellent properties e Scarce on Earth, lightweight PUsed in cooking ware and heat exchangers lectrically insulator at low temp. and conductor at e Used in Cutting tool (CBN), fibers pplication of Fine Ceramics Important Methods for Solid State Materials 1. Soft chemistry Intercalation and De-intercalation Sol-Gel process 2.Molten..Fluxes 3. High Pressure Synthesis Ceramic rotors under -CVD(Chemical Vapor Deposition) oduction materials 5. Single crvstal growth ntered silicon g13 Heat Treatment of Glasses Annealing: elevate temperature to remove thermal stresses resulting from inhomogeneous temperatures during cooling (similar to annealing of metals) Tempering: heating glass above glass transition temperature but below softening point; then quench in an air jet or oil bath. The interior: cools later than outside, tries to contract while in a plastic state after exterior has already become rigid. Causes residual compressive stresses on surface and tensile stresses inside. In fracture: crack has to overcome residual compressive stress, making tempered glass less susceptible to fracture. Used in automobile windshields, glass doors, eyeglass lenses, etc. Glass Product Window glass Containers Light Bulb Glass Laboratory Glassware Glass fibers Optical glasses Glass-Ceramics By heat treating glass into a polycrystalline structure (90-98%) Grain size usually ranges from 0.1 to 1.0mm, which makes stronger. Opaque (gray or white) in color After heating and forming into a desired geometry, it is cooled and reheated to crystallize at a high density of nucleation sites. Efficient processing, close dimensional control and excellent properties Used in cooking ware and heat exchangers 5.Other Important Elements Replace ceramics in some applications. Silicon A semimetallic element abundant on earth. The same structure as diamond but lower in hardness Brittle, lightweight and chemically inactive at room temperature Used to make glass and clay, alloying ingredient, semiconductors Boron Scarce on Earth, Lightweight Electrically insulator at low temp. and conductor at high temp. Used in Cutting tool (CBN) , fibers Application of Fine Ceramics Ceramic rotors under commercial production materials: Sintered silicon nitride Important Methods for Solid State Materials 1. Soft Chemistry Intercalation and De-intercalation Dehydration Ion Exchange Sol-Gel Process 2. Molten Salt Fluxes 3. High-Pressure Synthesis 4. CVT (Chemical Vapor Transport) CVD (Chemical Vapor Deposition) 5. Single Crystal Growth