Engineering Ceramics For Advanced Applications Flashcards
Define a ceramic
A solid compound formed by heat and pressure with a non metal and a metal
Characteristics of a ceramic
Hard Wear resistant Prone to thermal shock Refractory Electrically/thermally insulative Non magnetic Chemically stable Oxidation resistant
Define refractory
A non metallic material having those chemical and physical properties that make them applicable for structures
Name all applications of ceramics
Glass Clay products Refractories (fireclay silica) Abrasives Cements Advanced ceramics
What is the difference between a functional ceramics?
Functional - physical and chemical properties are sensitive to change in the environment
What is the piezoelectric effect
The internal generation of electrical charge resulting from a an applied force
Define glass
Super cooled no crystalline amorphous high viscous fluid
Define viscosity
Measure of a fluids resistance
Define specific volume
Volume/mass
What is Crystallisation
Long order arrangement of atoms during processing
What is annealing
Removing internal stress caused by uneven causes cooling
What is tempering
When a hot piece of glass has the surface out into compression to suppress the growth of cracks
What is sintering ?
Conversion of powder and grains into an object by heat and pressure
What desired microstructure is needed for the following:
High strength High toughness High creep resistance Transparency Low dielectric loss Good varistor behaviour Catalyst
Strength - small grains Toughness - duplex microstructure Creep - large grains and no amorphous grain boundary Transparency - pore free microstructure Dielectric - small uniform grains Catalyst - large surface area
Benefits of hot pressing
Industrially viable
Up scalable
Economical
Complex designs
Mechanical properties or ceramics
All ceramics are brittle (amorphous and polycrystalline)
What is brittleness?
Fracture propagates at high speed and little energy absorption
Can occur well below the yield strength of the material
Advantages of tensile testing
Uniform stress
Large effect volume
Disadvantages of tensile testing
Expensive samples Complex shape Difficult to machine High surface quality Difficult to grasp Difficult alignment
Advantages of Compression testing
Ceramics are more resistant to compression testing than tension.
Uniform stress
Simple shapes
Disadvantages of compressive testing
Need a jig for testing
Flat simple bases
What does a flexural testing test for?
Indication of a materials stiffness when bended
What is the formula for flexural strength
3PL/2BD^2
