Metals & Ceramics: Crash Course Engineering #19

Materials significantly affect the design and durability of products.
Examples of unsuitable materials: using candle wax for a stop sign or chocolate for a bench.
Essential for engineers to select the right materials for creating products.
Two main types of materials discussed: metals and ceramics.

Design decisions often involve trade-offs and careful consideration.
Analogous to choosing braces where both metal and ceramic options exist.
Understanding the pros and cons of each material type is crucial for decision-making.

Metals are familiar to many and are prevalent in various structures and products (cars, buildings, devices).
Metals undergo several processes before being used in final products:
- Start with ore extraction, which contains elements or minerals.
- Elements are refined from ore through processes like casting or forging.
- The resulting material can be formed into bulk shapes such as ingots or sheets.
Common characteristics of metals include:
- Good electrical and thermal conductivity.
- Malleable (easily shaped) and ductile (can be stretched without breaking).
- Strong, stiff, and resistant to fracture.
- Shiny appearance due to light reflection.

About 75% of known elements are metals.
Common metals: aluminum, iron, potassium, magnesium.
Alloys combine metals for enhanced properties:
- Steel is an example (iron alloy with carbon, sometimes chromium or nickel).
- Alloys often offer better impact resistance and corrosion resistance compared to pure metals.

The atomic structure allows electrons to move freely, facilitating heat and electrical conductivity.
This mobility explains the superior conductive properties of metals and their alloys.

Ceramics are compounds that are neither fully metallic nor organic.
They include materials like glass and traditional ceramics (e.g., porcelain, bricks).
Characteristics of ceramics include:
- Generally stiff, strong, and hard.
- Brittle, more prone to fracturing than metals.
- Poor electrical and thermal conductors (typically), though some exhibit conductive properties.
- Resistant to extreme temperatures and harsh environments.

Glass-Ceramics:
- Exhibit properties between glass and ceramics; strong, heat-resistant, biologically compatible; good insulators.
Clay:
- Inexpensive and easy to work with; naturally abundant; requires little refinement.
Cement:
- Used primarily as a binder in concrete; sets at room temperature; essential for construction projects.

Both materials are important in microelectromechanical systems (MEMS), which utilize tiny sensors for various applications.
Example: Accelerometers in smartphones and vehicles that trigger airbags; MEMS offers miniaturization, light weight, and cost-effectiveness.

Choosing materials requires consideration of their properties and suitability for specific applications.
For braces, metal is more durable while ceramic is less irritating and more discreet.
Engineers must balance personal preferences, resources, and design limitations when selecting materials.
Future lessons will cover polymers, the third main type of material in engineering.