Material Science and Engineering CORREL

Structure-Property Relationship

investigates link between structure and material properties

Functional Perspective

focuses on developing new materials and creating applications

Crystalline materials

atoms arranged in 3D periodic lattice

Amorphous materials

random atomic arrangement (glass, polymers)

• Point

• Line

• Planar

Different types of defects

• Ionic

• Covalent

• Metallic

Different types of primary bonds

ionic bond

An __________ is formed when electrons are transferred from one atom to another, creating positively and negatively charged ions that attract each other through electrostatic forces.

• Occurs between metals and nonmetals

• Metals lose electrons → form cations (+)

• Nonmetals gain electrons → form anions (−)

What happens in ionic bonding?

covalent bond

A ______________ is formed when two or more nonmetal atoms share electrons to achieve a stable electron configuration

• Occurs between nonmetal + nonmetal

• Electrons are shared, not transferred

• Can be polar (unequal sharing) or nonpolar (equal sharing)

What happens in covalent bonding?

metallic bond

A ____________ is formed when metal atoms share a “sea” of delocalized electrons that move freely among positive metal ions.

• Occurs between metal + metal

• Valence electrons are not bound to any one atom → they flow freely

  • This creates a structure of positive metal ions surrounded by mobile electrons

What happens in metallic bonding?

σ = F/A

What is the formula of Stress?

Stress

It tells us how much force is acting on a certain area of the material.

Strain

________ is the measure of deformation of a material — basically, how much it stretches or compresses relative to its original length.

ε = ΔL/L₀

What is the formula of Strain?

Stress-Strain curve

It shows how a material behaves when loaded.

Linear (Elastic) Region

Region where Stress and strain are proportional. Material returns to its original shape when the load is removed.

Hooke’s Law

What principle is followed at the Linear Region?

Hooke's law

______________ states that the force (F) required to stretch or compress a spring by a distance (x) is directly proportional to that distance

Yield Point

The point where the material begins to deform permanently. Beyond this, even if you remove the load, it won’t return to its original shape.

Plastic region

Permanent deformation occurs.

Ultimate Tensile Strength (UTS)

Maximum stress the material can withstand before necking or breaking.

Fracture point

The point where the material breaks.

Yield strength/point

onset of plastic deformation

Toughness

energy before fracture (area under stress strain curve)

Ductility, hardness, and creep

time-dependent deformation

Because of free electrons

Why do metals have high thermal conductivity?

σ decreases with increasing temperature

What is the relationship of electrical conductivity (σ) and temperature for metals?

σ increases with increasing temperature

What is the relationship of electrical conductivity (σ) and temperature for semiconductors?

• Electrochemical process

• Oxidation at anode

• Reduction at cathode

What happens during corrosion of metals?

Cathodic protection

use of sacrificial anode

• Metals

• Ceramics

• Polymers

• Composites

Different types of materials

Metals

Typically malleable, ductile, and good conductors of heat and electricity

Non-ferrous metals are nonmagnetic

What is one of the main differences between ferrous and non-ferrous metals?

Ceramics

Inorganic, non-metallic materials formed by heating at high temperatures

Ceramic

What structure does glass have?

Ceramics

Excellent compressive strength, poor tensile strength

Through polymerization

How are polymers formed?

Thermoplastics

Type of polymer that soften with heat, recyclable

Thermosets

Type of polymer that permanently harden

Elastomers

Polymers that are highly elastic

Copolymer

Two or more monomers

glass transition temperature (Tg)

The _________________________ is the temperature at which a polymer changes from a hard, glassy, and brittle state to a soft, rubbery, and flexible state.

Directly proportional
Higher molecular weight = greater toughness and viscosity

In polymers, what is the relationship between molecular weight and toughness & viscosity?

Composites

Made up of two or more distinct components

• Matrix (Continuous phase)

• Reinforcement

Elements of a composite

Metal Matrix (MMC)

Type of Composite: metal + fibers/particles

Ceramic Matrix (CMC)

Type of Composite: ceramic + reinforcing elements

Polymer Matrix (PMC)

Type of Composite: polymer + fibers

Semiconductors

intermediate conductivity; controlled conductivity via doping (Si, GaAs)

Biomaterials

compatible with human tissues; biocompatible implants

Smart Materials

sense and respond to changes; respond to temperature, stress, or electric field

Nanomaterials

structures <100 nm with unique surface properties; nanoscale structural features

Nanomaterials

High surface area, quantum effects

Biomaterials

interact safely with biological systems

Semiconductors and Smart Materials

Band gap determines conductivity

Strength

ability to resist deformation

Ductility

ability to stretch into wires

Hardness

ability to resist scratching

Toughness

ability to resist impact

Elasticity

ability to return to shape

Plasticity

ability to deform permanently

E = σ/ε

What is the formula for Hooke’s law?

2

How many atoms are in BCC?

4r = √3a

What is the formula of BCC?

4

How many atoms are in FCC?

4r = √2a

What is the formula of FCC?

1

How many atoms are in SC?

a = 2r

What is the formula of SC?

Atomic Packing Factor (APF)

The _________________________ measures how tightly the atoms are packed in a crystal

Volume of atoms in unit cell divided by the volume of the unit cell

How is APF solved?

SC: 0.52

BCC: 0.68

FCC: 0.74

HCP: 0.74

What is the APF of the different crystal structures?

coordination number

The _________________ is the number of nearest neighbor atoms that surround a given atom in a crystal structure.

SC: 6

BCC: 8

FCC: 12

HCP: 12

What is the coordination number of the different crystal structures?

ρ = (n x A) / Vc x Na

n = atoms

A = atomic wt

Vc = volume of unit cell

Na = Avogadro’s number

What is the formula for Density (ρ) in crystal lattices?