Chapter1 Introduction

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Chapter-1 Introduction
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Historical development

• Early humans (Stone, wood, clay, skins, ..)
• New material discovered (e.g., pottery, ..)
• Properties can be altered by heat treatment and
  alloying.
• Transformation from material selection to
  material synthesis (relating microstructure to
  properties)

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Definitions

• Material science
• Investigating the relationships that exist
  between the structures and properties of
  materials.
• Materials engineering
• Designing or engineering the structure of a
  material to produce predetermined set of
  properties (based on structure property
  relationship).

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Processing - Structure Properties
-Performance

• Materials are... engineered structures...not
  black boxes!
• Structure
• Subatomic (electrons), Atomic (atoms and
  molecules), Microscopic (dislocations),
  Macroscopic (Naked eye).

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Structure

• Structure...has many dimensions...

Structural feature
Dimension (m)
-10
lt 10
atomic bonding
-10
missing/extra atoms
-10
10
-8
-1
crystals (ordered atoms)
10
second phase particles
-8
-4
10
-10
crystal texturing
-6
gt 10
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Structure, Processing, Properties

• Properties depend on structure (e.g.,
  hardness vs. structure of steel)
• Processing can change structure (e.g.,
  structure vs. cooling rate of steel)

Hardness (BHN)
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Electrical

• Electrical Resistivity of Copper
• Adding impurity atoms to Cu increases
  resistivity.
• Deforming Cu increases resistivity.

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Optical

• Transmittance
• Aluminum oxide
• may be
• transparent, translucent, or
• opaque depending on the material structure.

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Deteriorative
10
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Material classification

• Based on what ?
• Chemical makup and atomic structure
• (1) Metals
• (2) Ceramics
• (3) Polymers
• Composites
• Semiconductors
• BIOMATERIALS

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Metals

• Combinations of metallic elements.
• Large number of nonlocalized electrons (sea of
  electrons) This determines metal properties.
• Good conductors to heat and electricity.
• Opaque to visible light.
• Strong BUT deformable (THUS, heavily used in
  structures).

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Ceramics

• Compounds between metallic and nonmetallic
  elements (oxides, nitrides, carbides, ..) (e.g.,
  clay minerals, cement, glass, ..)
• Insulative to heat and electricity.
• Hard BUT brittle
• Resist harsh environment than metals.

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Polymers

• Many are organic compounds based on carbon,
  hydrogen and other nonmetals (e.g. rubber,
  plastic, ..).
• Large molecular structure.
• Low density and extremely flexible.

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CompositesSemiconductors

• More than one material e.g., fiberglass
  (glass in polymers), glass gives strength,
  polymer gives flexibility.
• Electrical properties between conductors and
  insulators, properties depend on amount of
  impurities present.

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Biomaterials

• Employed in compounds implanted into the human
  body.
• Must be compatible with body tissues.
• All previous materials can be employed.