1. Metals, Alloys and Smart Alloys
Learning Objectives:
To understand that the uses for certain metals relate to their specific properties.
To understand that the properties of metals can be improved by producing alloys.
To recall that some of the latest alloys, called ‘Smart Alloys’ can alter their properties on demand.

2. Metals and Alloys

3. Metallic bonding Metals form a special form of giant lattice structure
Metal atoms are packed closely together in a regular arrangement
Since they are so close together, the valence electrons tend to move away from their atomic nuclei
A ‘sea’ of free delocalised electrons is formed surrounding a lattice of positively charged metal ions
The positive ions are held together by their strong attraction to the mobile electrons which move in between the ions
Let’s watch a video!

4. Remember those properties of metals?
Most (not all group 1) metals have high melting and boiling points
It takes a lot of energy to weaken the strong forces of attraction between metal ions and delocalised ions in the lattice…

5. Metals are good conductors of heat and electricity
When a voltage is applied, the delocalised electrons move through the metal lattice towards the positive pole of the cell

6. In pure metals the atoms arrange themselves closely together into regular patterns. This makes them dense and also gives them many of their other useful properties.

7. Metals are malleable and ductile
The layer arrangement of the atoms allows the metals to change shape if a force is applied. The layers can slip over each other.
This can be useful if you want to shape the metal but not so useful if you want it to resist the force and be strong.

8. What is an alloy?
An alloy is a special mixture of two or more metals or one or more metals with a non-metal
An alloy is NOT just a mixture of metal crystals
In fact, the atoms of the second metal form part of the metal crystal lattice

9. Structure of an alloy

10. Alloys contain atoms of different sizes, which distorts the regular arrangements of atoms. This makes it more difficult for the layers to slide over each other, so alloys are harder than the pure metal.
It is more difficult for layers of atoms to slide over each other in alloys

11. Why use alloys?
Alloys often have properties that are different to the metals they contain.
This makes them more useful than the pure metals alone.
For example, alloys are often harder than the metal they contain.

12. Common alloys Alloy Main metal in alloy Uses Properties Amalgam
mercury
Dental fillings
‘smart’ amalgam
Brass
Copper and zinc
Hinges and plugs, musical instruments
Stronger than copper but still malleable
Solder
Lead and tin
Joining metals
Very tough
Bronze (5000 BC!)
Copper and tin
Machines, statues, bells
Stainless steel
Iron +chromium + nickel
Cutlery, surgical instruments
Doesn’t rust

13. By mixing two or more metals together the regular arrangement of the atoms is disrupted. This prevents the atoms forming layers and makes it harder for the atoms to slide over each other. The alloy is stronger than the pure metals.
Metal A
Metal B

14. Steel is an alloy. Pure iron is not strong enough to be used in structures. Steel contains a small amount of carbon. This disrupts the layers of atoms in the metal and increases the strength of the metal considerably.
Although it is very strong steel will corrode (rust) easily and it has to be constantly protected from the effects of water and air.

15. Stainless steel is an alloy that contains other metals such as Nickel and Chromium. Stainless steel has the strength of steel combined with the corrosion resistance of nickel and the shininess of chromium. This makes it a useful material in applications where you need strength combined with beauty and corrosion resistance..

16. Smart alloys Nickel-titanium spectacles have ‘memory’!
These are alloys that can ‘remember’ their original shape. If they are deformed they can return to their original shape.
Nickel-titanium spectacles have ‘memory’!

17. Smart alloys: your braces!
Cobalt nickel titanium
OR multiple memory materials

18. Smart alloys – blood vessel stents
Vascular stents are made of platinum-chromium or cobalt-chromium

19. Metals, Alloys and Smart Alloys
Learning Objectives:
To understand that the uses for certain metals relate to their specific properties.
To understand that the properties of metals can be improved by producing alloys.
To recall that some of the latest alloys, called ‘Smart Alloys’ can alter their properties on demand.

20. Metal Properties Uses Aluminium Copper Gold Steel
Copy the table below. Working with a partner, complete as much of the table as you can.
Metal
Properties
Uses
Aluminium
Copper
Gold
Steel
Low density, strong, resistant to corrosion, good conductor of electricity
Lightweight structures, aircraft, drinks cans, high voltage cables.
Electrical wiring, water pipes.
Good conductor of electricity, resistant to corrosion, easily shaped, flexible
Jewellery.
Shiny, very resistant to corrosion, very unreactive, soft, easily shaped
Very strong, very dense.
Large structures and heavy duty engineering such as bridges, trains, cars etc.