1. Technological World – CH 12 Manufacturing Technical Objects
Materials and their Properties

2. Question of the Day
How did ancient Egyptians refrigerate their food? Specifically their liquids like milk?

3. Answer of the Day Evaporation / Pots / Ceramics
Zeer Pot

4. Material Properties
Different types of materials have characteristic properties that are useful depending on the desired project
Materials degrade over time due to their surrounding environments
Material degradation can be slowed down by protecting the material by applying certain steps
Materials we will discuss:
Wood, ceramics, metals+alloys, plastics, and composites

5. Wood Obtained from harvesting and processing trees
Different types of wood can vary the mechanical properties
Advantages
Hardness, elasticity, resilience and toughness
Low thermal and electrical conductivity
Easily shaped and assembled
Light and cheap
Aesthetically pleasing

7. Modified Wood
Wood that has been treated or made from wood mixed with other substances
Example
Plywood
Particleboard
Fibreboard

8. Degradation + Protection of Wood
Wood can degrade rapidly if not properly treated
Fungi, microorganisms and insects cause wood to rot
To protect, you can varnish, paint or treat the wood.
Wood treatments:
Dipping in an alkaline copper solution
Heat to high temperature

11. Ceramics
Solid material obtained from heating inorganic matter containing various compounds, usually oxides
Most ceramics are fragile, but we can manufacture highly resilient items
Example: brick, glass, porcelain, clay pots
Advantages
Cheap and plentiful (sandglass, claypots)
Low electrical conductivity
High hardness
Heat resistant and low thermal conductivity
Resistance to corrosion

12. Chimney + Pots – Primitive Technology

13. Degradation + Protection of Ceramics
Not necessary
Certain acids and basics can degrade ceramics
Thermal shock (quick change in temperature) can shatter ceramics

14. Metals and Alloys Metal is made from mineral ore Advantage:
Good conductors of heat and electricity
Alloy = mixture of metal with one or more substances (either metallic or nonmetalic)

16. Degradation + Protection of Metals
Main cause of degradation is oxidation (rust)
The metal reacts with oxygen in the atmosphere
To protect, we isolate the metal with a protective coating
Example:
Metal coating (zinc, chrome, gold, etc…) (see p. 395)
Other coating (paint, enamel, grease, resin)

17. Degradation + Protection of Metals
Other techniques are also used.
Steel heat treatments enhance certain properties
Heating – quench hardening
Cooling
Heating – tempering
Blacksmith quenching:

19. Plastics
Material made of polymer chains. The properties of a plastic can be modified based on added substances
Thermoplastic:
Becomes soft when heated and can be molded
Thermosetting plastics:
Plastic remains hard even when heated

21. Degradation + Protection of Plastics
Plastics take a long time to degrade
Main causes - Protection
Liquid – Waterproof coating
Oxidation – Add antioxidants
UV rays – Add pigments that absorb UV

22. Composites
A composite is formed by combining materials from different categories to obtain a material with enhanced properties