Material Science Midterm 1

Ionic Percentage

1-e^(E1-E2)/4

Point Defects

Vacancies, Interstitials, and Substitutions

Linear Defects

Edge Dislocations and Screw Dislocations

Caused by applied stresses

Volume Defects

Voids, Precipitates, and Inclusions

Interfacial/Planar Defects

Grain Boundaries

Twin Boundaries

Stacking Faults

Thermosets

Crosslinked and Networked

-Chains held with covalent bonds

-stiff/rigid

-formed by chemical reactions

-will not melt

Covalent Bonding

Highly Directional

Shares electrons

Thermoplastics

Linear and Branched

-Chains held with secondary bonding

-Melts when heated

-Flexible

FCC

4 atoms

CN 12

74% packed

BCC

2 atoms

CN 8

68% packed

SC

1 atom

CN 6

52%

FCC Interstitials

4 Octahedral (edges and center)

8 Tetrahedral (almost corners/diamond structure)

BCC Interstitials

6 Octahedral (faces and edges)

12 Tetrahedral (off-center faces)

Melting point/Bond length

BCC Linear Atomic Density [100]

(√3)/4R

1/a

FCC Linear Atomic Density [100]

(√2)/4R

1/a

FCC Planar Atomic Density (100)

1/4R^2

BCC Planar Atomic Density (100)

3/16R^2

Thermal Expansion Coefficient

ΔL=αL0​ΔT

Amorphous

Atoms are arranged irregularly (opposite of crystalline)

Twin Grain Boundary

ABCBA

HCP Stacking Sequence

ABABAB

FCC Stacking Sequence

ABCABCABC

SC Lattice Points

000

BCC Lattice Points

0 0 0

.5 .5 .5

Precipitates/Inclusions

Secondary phases in the material

strengthens the material

Voids

holes/pores in the crystal

weakens the material

can affect transparency

FCC Lattice Points

0 0 0

.5 0 .5

0 .5 .5

.5 .5 0

Molecular Weight

Based on length of chain

DP

Number of Mers per chain

Frenkel Defect

opposite charged pair of vacancy and interstitial

Shottky Defect

opposite charged pair of vacancies

Edge Dislocation

Burger's Vector Perpendicular to dislocation line

Screw Dislocation

Burger's Vector Parallel to dislocation line

Burger's Vector Steps

Define dislocation line

Use Right Hand Rule to determine Circuit direction

Calculate Burger's Vector from start to end

Grain Boundaries

High Energy States

High atomic mobility

High chemical reactivity

Will decide properties