materials

what is materials science

how a material’s composition and structure affects its properties and performance

what are the four material families

metals, polymers, ceramics and glasses, composites

reading a materials selection chart

up the chart = higher stiffness

across the chart = higher density

uses logarithmic scales

four mechanical properties

elastic modulus (E), yield strength (σy), fracture toughness (KIC), density (ρ)

metals (examples, used where, properties)

e.g. Aluminium, nickel, steel, copper, titanium

 

Used in reaction vessels, pipes, catalysts etc.

 

PROPERTIES: strong, tough, high stiffness, good conductor, corrosion resistance depends on metal and environment

polymers (examples, used where, properties)

e.g. PVC, PTFE, kevlar, thermoplastics

 

Used in coatings, insulation, making clothes, packaging, sutures

 

PROPERTIES: low density, easy to shape, lower stiffness than metals and ceramics, sensitive to (environmental) conditions

ceramics and glasses (examples, used where, properties)

e.g. Alumina, clay, silica glass, quartz

 

Used in bricks, sanitary ware, glassware, dental ceramics

 

PROPERTIES: high stiffness and resistance to abrasion, many tolerate harsh (corrosive) conditions (e.g. high temp.), vulnerable to cracking/fracture

composites (examples, used where, properties)

e.g. Wood, concrete

 

Used in bike frames, vehicle components, composite decking

 

PROPERTIES: good performance for their weight, expensive, difficult to recycle/repair (sustainability)

what is atomic structure

number of protons and neutrons in the nucleus of an atom

what is crystal structure

arrangement of atoms in the crystalline solid material

what are the three types of metallic crystal structures

FCC, BCC, HCP

FCC (stands for, number of atoms in one unit cell, how to calculate Vc, APF)

face centered cubic

4 atoms (made up of eight 1/8 s and six ½ s)

Vc = 16R³√2

APF = 0.74

BCC (stands for, number of atoms in one unit cell, how to calculate Vc, APF)

body centered cubic

2 atoms (made up of 1 whole atom and eight 1/8 s → more energy required to move the whole atom so moves less freely than FCC)

Vc = ((4 / √3) * R)³

APF = 0.68

what does HCP stand for

hexagonal close packed

atomic packing factor formula and why it’s important

APF = Vs / Vc

Vs = volume of atoms in a unit cell = (4 / 3)𝜋R³ * n → where n is the number of atoms in one unit cell

Vc = total unit cell volume = different for FCC and BCC

APF describes the proportion of a unit cell occupied by atoms and can influence mechanical properties

density formula

ρ = (n A) / (Vc Nₐ)

n = number of atoms in one unit cell

A = atomic weight (g/mol)

Vc = volume of unit cell (cm³)

Nₐ = avagadro’s number (6.022 × 10²³ atoms/mol)

nm (nanometers) → µm (micrometers) → mm (millimeters)

÷1000

what is it called when polymers/ceramics are ordered

crystalline

what is it called when polymers/ceramics have a lack of order

amorphous

what is a cross link

a bond that joins one polymer chain to other polymer chains (makes it stronger)