Lecture 2 - How To Choose A Material ? Flashcards
What are 3 factors to consider when choosing a material
Stiffness, strength, density etc
What are the 6 classes of materials
Metals, ceramics, glasses, polymers, Composites and natural materials
What are 3 electrical properties of Cu
Highly conductive metals
Adding impurity atoms increases resistivity
Deforming Cu increases resistivity
What are 3 mechanical properties of metals
Stiff with range
High density of range
Mouldable ( can be shaped and worked)
What are ceramics
Crystalline, mainly metal oxide
What type of conductivity and chemical attack does ceramics have
Low thermal conductivity
Good resistance to chemical attack
What type of structure does ceramics have
A highly defined crystallographic structure
What are 5 typical properties of ceramics
Generally stiff and hard, but brittle
Medium density
Low liquid uptake
Good thermal stability
Can suffer from low crack growth
What type of material is glass
Disordered or amorphous ( no long range atomic order)
6 properties of glasses
Amorphous
Medium stiffness
Very brittle
Very notch sensitive
Generally transparent
Used in optical fibre for data transmission
What is a polymer
A large molecule composed of many subunits called monomers
What are polymers mostly made from
Carbon
Hydrogen
Oxygen
Synthetic polymers includes plastics and are natural biopolymers such as DNA
6 properties of polymers
Flexible
Long extension to failure
Tough
Low density
Many soften and melt at relatively low temperatures (thermoplastics)
Some don’t melt at any temperature ( thermosets)
In metals what are the charge carriers
Electrons
What are the charge carriers in semiconductors
Either electrons or missing electrons (a hole)
