Chapter 1 - What is MSE?

1.1

  • Early human eras:

    • Stone Age: stone, wood, clay, and animal skins (natural)

    • Bronze Age: metallurgical techniques (copper alloys )

    • Iron Age: high-temperature processing (iron)

  • Modern technological dependencies:

    • Automobiles → low-cost structural steel

    • Sophisticated electronic systems → semiconductor materials

1.2 MSE MANTRA

Processing→Structure→Properties→Performance\text{Processing} \rightarrow \text{Structure} \rightarrow \text{Properties} \rightarrow \text{Performance}

  • Structure: arrangement of a material's internal components

    • Subatomic: electrons within the individual atoms, their energies and interactions with the nuclei.

    • Atomic Structure: organization of atoms to yield molecules or crystals

    • Nanostructure: atoms that form particles (nanoparticles) that have nanoscale dimensions (less than about 100 nm)

    • Microstructure: observation using some type of microscope (between 100 nm and several millimeters).

    • Macrostructure: viewed with the naked eye (ranges from several millimeters to approximately 1m)

  • Property: how much and the kind of response a material has to an imposed stimulus (independent of shape or size ex. rubber bends regardless if its big or small)

    • Mechanical: deformation to an applied load or force (elastic modulus (stiffness), strength, and fractures)

    • Electrical: response to an applied electric field stimulus (electrical conductivity and dielectric constant)

    • Thermal: changes in temperature or temperature gradients across a material (heat capacity and thermal expansion)

    • Magnetic: responses to application of a magnetic field (magnetic susceptibility and magnetization)

    • Optical: stimulus is electromagnetic or light radiation (refraction and reflectivity)

    • Deteriorative Characteristics: chemical reactivity of materials (corrosion resistance of metals)

(example of the mse mantra is the three circles)

1.3 How engineer selects best material

  1. Operational In-Service Conditions: must accept tradeoffs because materials don’t always show ideal combinations (ex. trading high mechanical strength for reduced ductility)

  2. In-Service Material Degradation: potential property degradation (elevated operating temperatures, mechanical fatigue, or corrosive chemicals)

  3. Economic Considerations: total finished component costs, combining raw material expenses and manufacturing costs.

1.4 Classification of Materials

  • 4 solid materials: metals, ceramics, polymers, composites

Metals

  • Metals: one or more metallic elements (iron, aluminum, copper, titanium, gold, nickel) with small amounts of nonmetallic elements (carbon, nitrogen, oxygen)

    • stiff and strong but ductile (can deform not fracture)

    • have non localized electrons so can’t bond to some atoms (means are good conductors of electricity but not transparent), can be magnetic

Ceramics

  • Ceramics: compounds between metallic and nonmetallic elements (oxides, nitrides, and carbides)

    • traditional ceramics are composed of clay minerals, cement, glass

    • stiff and strong but brittle so they fracture

    • can insulate electricity and heat so low conductors of electricity and resistant to high temps and can be transparent (oxides)

Polymers

  • Polymers: familiar plastic and rubber materials (organic compounds so carbon, hydrogen and other nonmetallic elements)

    • large chainlike molectular structures w carbon backbone

    • not stiff and strong because of low densities (deform into shapes)

    • chemically unreactive, low conductors of electricity so can soften at high temps and not magnetic

Composites

  • Composites: two or more of the metals, ceramics, polymers

    • can be natural (wood and bone) but most human made

    • ex. carbon fiber–reinforced polymer (CFRP) composite is carbon fibers embedded within a polymer

      • stronger then glass fiber (which is stiff but flexible) but expensive

      • used in aerospace, sports, car bumpers

1.5 Advanced Materials and Technologies of the Future

  • 4 advanced materials: semiconductors, biomaterials, smart materials, nanomaterials

Semiconductors

  • Semiconductors: properties between electrical conductors (i.e., metals and metal alloys) and insulators (i.e., ceramics and polymers)

    • can change electrical properties when impurity atoms are added creating integrated circuits that has transformed electronics

Biomaterials

  • Biomaterials: nonliving materials implanted into body so they can function

    • must be biocompatible with body tissues and fluids

    • must neither elicit rejection or physiologically unacceptable responses nor release toxic substances so constraints are imposed

Smart Materials and Systems

  • Smart Materials: new materials

    • able to sense changes in their environment and respond

    • materials used for actuators: shape-memory alloys, piezoelectric ceramics, magnetostrictive materials, and electrorheological/magnetorheological fluids

    • materials used as sensors include optical fibers, piezoelectric materials, and microelectromechanical systems

    • ex. piezoelectric sensors inserted into helicopter blades to stress and deformations that are fed into computers to create noise cancellation

Nanomaterials

  • Nanomaterials: nanoscale of metals, ceramics, polymers, or composites

    • can be chemically dangerous being absorbed into bodies