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The Mars Rovers - Spirit and Opportunity
Spirit and Opportunity are made up of materials such as
* Metals * Ceramics * Composites * Polymers * Semiconductors www.nasa.gov

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What are Materials?
•
Materials may be defined as substance of which something is composed or made.
•
We obtain materials from earth crust and atmosphere.

Silicon and Iron constitute 27.72 and 5.00 percentage of weight of earths crust respectively.
 Nitrogen and Oxygen constitute
78.08 and 20.95 percentage of dry air by volume respectively.

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Why the Study of Materials is Important?
• Production and processing of materials constitute a large part of our economy.
•
Engineers choose materials to suite design.
• New materials might be needed for some new applications.

Example :- High temperature resistant materials.
 Space station and Mars Rovers should sustain conditions in space.
* High speed, low temperature, strong but light.
•
Modification of properties might be needed for some applications.
 Example :- Heat treatment to modify properties.

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Materials Science and Engineering
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Materials science deals with basic knowledge about the internal structure, properties and processing of materials.
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Materials engineering deals with the application of knowledge gained by materials science to convert materials to products.
Materials Science
Basic
Knowledge of
Materials
Materials Science and
Engineering
Resultant
Knowledge of Structure and
Properties
Materials Engineering
Applied
Knowledge of Materials

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Types of Materials
•

Composed of one or more metallic elements.

Example:Iron, Copper, Aluminum.

Metallic element may combine with nonmetallic elements.

Example:Silicon Carbide, Iron Oxide.

Inorganic and have crystalline structure.

Good thermal and electric conductors.
Metals and Alloys
Ferrous
Eg: Steel,
Cast Iron
Nonferrous
Eg:Copper
Aluminum

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Types of Materials
•

Organic giant molecules and mostly noncrystalline.

Some are mixtures of crystalline and noncrystalline regions.

Poor conductors of electricity and hence used as insulators.

Strength and ductility vary greatly.
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Low densities and decomposition temperatures.
 Examples :Poly vinyl Chloride (PVC),
Polyester.
 Applications :Appliances, DVDs, Fabrics etc.

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Types of Materials
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 Metallic and nonmetallic elements are chemically bonded together.

Inorganic but can be either crystalline, noncrystalline or mixture of both.

High hardness, strength and wear resistance.
 Very good insulator. Hence used for furnace lining for heat treating and melting metals.
 Also used in space shuttle to insulate it during exit and reentry into atmosphere.
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Other applications : Abrasives, construction materials, utensils etc.

Example:Porcelain, Glass, Silicon nitride.

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Types of Materials
•

Mixture of two or more materials.
 Consists of a filler material and a binding material.
 Materials only bond, will not dissolve in each other.

Mainly two types :o Fibrous: Fibers in a matrix o Particulate: Particles in a matrix o Matrix can be metals, ceramic or polymer
 Examples :-

Fiber Glass ( Reinforcing material in a polyester or epoxy matrix)

Concrete ( Gravels or steel rods reinforced in cement and sand)

Applications :- Aircraft wings and engine, construction.

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Types of Materials
• Electronic Materials

Not Major by volume but very important.

Silicon is a common electronic material.
 Its electrical characteristics are changed by adding impurities .
 Examples:Silicon chips, transistors

Applications :Computers, Integrated
Circuits, Satellites etc.

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Competition Among Materials
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Materials compete with each other to exist in new market
1600
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Over a period of time usage of different materials changes depending on cost and performance.
1400
1200
1000
800
600
Example:-
Aluminum
Iron
Plastic
Steel
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400
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New, cheaper or better materials replace the old materials when there is a breakthrough in technology
200
0
1985 1992 1997
Model Year
Figure 1.14
Predictions and use of materials in US automobiles.
After J.G. Simon, Adv. Mat. & Proc., 133:63(1988) and new data

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Future Trends

Production follows US economy closely.
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Alloys may be improved by better chemistry and process control.

New aerospace alloys being constantly researched.
o Aim: To improve temperature and corrosion resistance.
o Example: Nickel based high temperature super alloys.

New processing techniques are investigated.
o Aim: To improve product life and fatigue properties.
o Example: Isothermal forging, Powder metallurgy.

Metals for biomedical applications

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Future Trends
•

Fastest growing basic material (9% per year).

After 1995 growth rate decreased due to saturation.

Different polymeric materials can be blend together to produce new plastic alloys .

Search for new plastic continues.

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Future Trends
•

New family of engineering ceramics are produced last decade
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New materials and applications are constantly found.
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Now used in Auto and Biomedical applications.

Processing of ceramics is expensive.
 Easily damaged as they are highly brittle.
 Better processing techniques and high-impact ceramics are to be found.

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Future Trends
•

Fiber reinforced plastics are primary products.

On an average 3% annual growth from
1981 to 1987.

Annual growth rate of 5% is predicted for new composites such as Fiberglass-
Epoxy and Graphite-Epoxy combinations.

Commercial aircrafts are expected to use more and more composite materials.

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Future Trends
•

Use of electronic materials such as silicon increased rapidly from 1970.

Electronic materials are expected to play vital role in
“Factories of Future”.

Use of computers and robots will increase resulting in extensive growth in use of electronic materials.

Aluminum for interconnections in integrated circuits might be replaced by copper resulting in better conductivity.

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Future Trends
Change their properties by sensing external stimulus.
 Shape memory alloys : Strained material reverts back to its original shape above a critical temperature.
 Used in heart valves and to expand arteries.
 Piezoelectric materials : Produce electric field when exposed to force and vice versa.

Used in actuators and vibration reducers.

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MEMS and Nanomaterials
•

Miniature devices

Micro-pumps, sensors
•

Examples: ceramics powder and grain size < 100 nm

Nanomaterials are harder and stronger than bulk materials.

Have biocompatible characteristics ( as in
Zirconia)
 Transistors and diodes are developed on a nanowire.

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Case Study – Material Selection
Steel and alloys
Wood
Carbon fiber
Reinforced plastic
Aluminum alloys
Ti and Mg alloys
Low cost but
Heavy. Less
Corrosion resistance
Light and strong. But
Cannot be shaped
Very light and strong. No corrosion.
Very expensive
Light, moderately
Strong. Corrosion
Resistance.
expensive
Slightly better
Than Al alloys. But much expensive
Cost important? Select steel
Properties important? Select CFRP