Material science 1

Flashcard Deck: Materials Science Exam Review (Based on Callister 10th ANZ Edition)

What is the difference between an atomic structure and a crystal structure?

Atomic structure describes the arrangement of particles inside a single atom  where as in an crystal structure the multiple atoms are ordered together in a neat geometric pattern.

Chapter 3: Structure of Crystalline Solids (3.1-3.15)

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What is a crystal structure?

The manner in which atoms, ions , or molecules are spatially arranged in a crystalline material.

What is the coordination number?

the number nearest neighbour atoms/ions that surround the central atom

What is the formula for unit cell length BCC?

What is the formula for unit cell length FCC?

What are the three common crystal structures and the amount of atoms in them?

• FCC (Face centered Cubic)
  Atoms per unit cell = 4

• BCC (Body Centered Cubic)
  Atoms per unit cell = 2

  • HCP (Hexagonal Close-packed)
    Atoms per unit cell = 6
    

What is the most efficient crystal structure?

FCC

Difference between crystal system and crystal structure?

Crystal system refers to unit cell geometry; crystal structure includes lattice type and atomic positions

What is the formula for Atomic Packing Factor (APF?)

What is a unit cell?

The smallest repeating unit of a crystal lattice.Wha

What is polymorphism?

The ability of a material to exist in more than one crystal structure.

What is anisotropy?

Directional dependence of properties.W

What is the miller index?

A notation to describe crystal planes and directions.

Chapter 12: Structure & Properties of Ceramics

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What is the coordination number in ceramic structures dependent on?

The ratio of cation to anion radii.Wh

What is a glass?

An amorphous non-crystalline solid.

What is a defect structure?

The arrangement and concentration of point defects in ceramics.W

Why are ceramics brittle?

Because of strong ionic/covalent bonds that restrict dislocation motion.

Why are ceramics unable to cunduct electricity?

Ceramics are unable to conduct electricity because of their structure. The strong covalent/ionic bonds do not allow free electron movement thus leading to no current.

Chapter 4: Imperfections in Solids

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What are the 4 main types of crystal imperfections?

• Point defects

• Line defects

• Interfacial defects

  • Bulk defects

What is a vacancy?

A missing atom in a lattice site

What is a self interstitial?

An atom positioned in the interstitial siter of its own lattice.Wha

What is a dislocation?

A linear defect around which some atoms are misaligned

What is a grain boundary?

An interfacial defect between two grains of different orientation.

Chapter 6: Mechanical Properties of Metals

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What is stress?

Force applied per unit are (Pa)

What is strain?

Deformation per unit length

What is youngs modulus?

Ratio of stress to strain in the elastic region

What is yield strength?

The stress at which plastic deformation begins.

What is tensile strength

Maximum stress a material can withstand while being stretched.

What is ductility?

A measure of plastic deformation before fracture.

What is toughness?

The ability to absorb energy up to fracture

Chapter 7: Dislocations and Strengthening Mechanisms

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What is slip?

Plastic deformation by dislocation motion

What are common strengthening mechanisms?

• Grain size reduction

• Solid solution strengthening

• Strain hardening

  • Precipitation hardening

What is strain hardening?

Increase ins trength due to plastic deformation

What is the Hall-Petch relationship?

Where strength increases with decreasing grain size.

Chapter 8: Failure

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What is fatigue?

Failure under cyclic stress.

What is creep?

Time-Dependent deformation under constant stress

Waht is fracture toughness

Resistance to fracture when a crack is present

What is brittle fracture?

The sudden fracture with little or no plastic deformation

Chapter 9: Phase Diagrams

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What is a phase diagram?

A map showing phase stability as a function of temperature and composition

In a phase diagram, alpha, L and alpha + L regions are used, what are they?

The alpha region represents a solid solution phase. The L region shows the liquid phase. Alpha + L means coexistence.

What is the eutectic point?

The lowest temperature at which liquid can coexist with two solids.

What is the lever rule.

A method used to calculate phase fractionsWha

What is solid solubility?

The extent to which one solid dissolves in another

Chapter 10: Phase Transformations

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What is nucleation?

The initial formation of a new phaseW

What is growth?

The increase in size of a new phaseW

What is the TTT diagram?

Time Temperature Transformation diagram for phase changes

What are the main phases of iron ?

• Austenite
  High temp

• Ferrite
  Room temp up to 900 celsius

• Cementite
  

• Pearlite

• Martensite

  • Bainite
    

Chapter 14: Polymer Structures

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What are the types of polymer structures?

• Linear

• Branched

• Crosslinked

  • Networked

What is tacticity?

Arrangement of side groups in a polymer chain

What is injection molding?

A process where molten polymer is injected into a moldWh

What are thermoplastics

Polymers that can be reheated and reshapedW

What are thermosets

Polymers that harden permanently when heated

Chapter 21: Optical Properties & Liquid Crystals

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What is birefringence?

Property of having different refractive indices for different light polarizations

What is transmittance?

Fraction of incident light that passes through a material

What is a nematic liquid crystal?

These are molecules that are both liquid and solid and inbetween. They are aligned in the same direction without long-range positional order

What is fluorescence

Immediate emission of light after absorption Wha

What is phosphorescence

Delayed light emission due to trapping in metastable states

How does band gap affect optical properties?

Larger gaps mean transperent in visible. Smaller gaps mean visible light gets absorbed

What is photoconductivity’?

This is the increase in electrical conductivity due to light exposure

What is luminescence?

Emission of light not due to heat

Chapter 20: Magnetic Properties

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What is diamagnetism?

Negative susceptibility due to changes in electron orbital motion, present in all materials

What is paramagnetism?

Positive magnetism due to unpaired electrons

What is ferromagnetism?

Strong magnetism due to aligned spins

What is ferrimagnetism?

Unequal opposing spins cancel eachother out

What is the Curie temperature?

Above this, ferromagnets become paramgnetic

What is the Neel temperature?

Above this antiferromagnets become paramagnetic

What is coercivity?

Magnetic field required to bring magnetization to zero

What is remanence ?

Residual magnetization after removing the external magnetic field

Chapter 18: Electrical Properties

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What is conductivity?

The ability of a material to conduct electric current

What are intrinsic semiconductors?

Pure semiconductors with no doping

What is the band gap?

Energy gap between valence and conduction band

How does the band gap affect electrical behaviour?

Conductors have no gap, semiconductors have small gaps, insulators have large gaps. Smaller gaps allow electron excitation more easily

What is the Hall effect?

A voltage developed across a current carrying conductor placed in a magnetic field

Chapter 16: Composites

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What are composites

Man made multiphase materials

What is the role of the matrix in a composite?

It binds and protects reinforcement, transfers load and prevents crack propagation.

What is the rule of mixtures?

A mathematical model to estimate composite properties based on volume fraction and properties

What are the main classifications of composites

• Particle reinforced

• Fiber reinforced

• Structural

  • Nanocomposites

What distinguishes dispersion strengthened composites

Use of extremely small dispersed particles to hinder dislocation motion and improve strength

What is the critical fiber length?

Minimum length reuired for efective stress transfer from matrix to fiber

What are the types of fiber reinforced composites based on fiber length and orientation

• continous aligned

• Discontinous aligned

• Discontinous random
  

What is the advantage of continous aligned fiber composites?

High anisotropic strength in the fiber direction

What are the types of fibers used as reinforcement

• Whiskers (strong single crystals)

• Fibers (polymeric or ceramic)

• Wires (metallic)

What are polymer-matrix composites (PMC’’s)

Most common composites

What is pultrusion?

A process for forming continous composite parts by pulling fibers through a resin bath and a heated die

What are struvctural composites?

Include laminar composites and sandwich panels for enhanced strength and stiffnessWh

What are sandwich panels?

Two strong face sheets bonded to alightweight coreWh

What are nano composites?

Materials reinforced with nanoscale particles