Chapter 1: Introduction to Material Science Flashcards
Characterization of Materials:
Processing
Properties
Performance
Structure
Content of Properties:
Material Characteristic
Response to external stimulus
Mechanical, electrical, thermal, magnetic, optical, etc.
Content of Performance
Behavior in a particular application
Content of Structure
Arrangement of internal components
Subatomic
Atomic
Microscopic
Macroscopic
Content of Processing
Method of preparing material
Classifications of Materials
Metals
Ceramics/Glasses
Polymers
Properties of Metals
Good conductors of electricity and heat
Susceptible to corrosion
Strong, yet deformable
Properties of Ceramics/Glasses
Thermally and electrically insulating
Resistant to high temperatures and harsh environments
Hard, but brittle
Properties of Polymers
Very large molecules
Low density, low weight
Can be extremely flexible
Properties of Biomaterials
Implanted in human bodies
Compatible with body tissues
Semiconductors
Electrical properties between conductors and insulators
Electrical properties can be accurately controlled
Composites
Consist of more than one material type
Designed to display combinations of properties of each component
Structure at Subatomic Level
Electronic structure of individual atoms that interact among atoms
Structure at Atomic Level
Arrangement of atoms in materials
Structure at Microscopic Level
Arrangement of small grains of material that can be identified by microscopy
Macroscopic Structure
Structural Elements that can be viewed with the naked eye
Angstron (1A)
10 ^ -10 meters
Nanometer (nm)
10 ^ -9 meters
Micrometer (µm)
10 ^ -6 meters
Millimeter (mm)
10 ^ -3 meters
Metallic Bonds
1, 2, or 3 valence electrons
Valence electrons free to drift through the entire materials forming “sea of electrons”
Non-directional bond
Ionic Bonds
Composed of metallic and non-metallic elements
Metallic elements give up valence electrons to non-metallic elements
All atoms have filled “inert gas” configuration
Ionic solid
Non-directional Bond
Covalent Bond
Electrons are shared between adjacent atoms, each contributing at least one electron
Shared electrons belong to both atoms
Directional bond
Types of Atomic Arrangements
Ordered and Disordered
Crystalline
Atoms arranged in a 3D periodic array, giving the material “long range order”
Properties of Crystalline
Stacking can effect properties
Anisotropic Materials
Non-Crystalline / Amorphous
Atoms only have short-range, nearest neighborly order
Properties of Amorphous
Viscous materials or rapid cooling
Isotropic Materials
Types of Microstructure
Single Crystal
Polycrystalline
Properties of Single Crystal
Periodic arrangement of atoms extends throughout the entire sample
Difficult to grow, environment must be tightly controlled
Anisotropic materials
Properties of Polycrystalline
Many small crystals or grains
Small crystals misoriented with respect to one another
Several crystals are initiated and grow towards each other
Anisotropic or isotropic materials
Macroscopic / Bulk Properties
Mechanical
Electrical
Optical
Thermal
Mechanical Bulk Properties
Elastic Modulus
Shear Modulus
Hardness
Electrical Bulk Properties
Conductivity
Resistivity
Capitance
Optical Bulk Properties
Reflectivity
Absorbance
Emission
Thermal Bulk Properties
Thermal Expansion
Heat Capacity
Thermal Conductivity
Properties
The way material responds to the environment and external forces
Mechanical Properties
Mechanical forces, strength, etc.
Electrical / Magnetic Properties
Electrical and magnetic fields, conductivity, etc.
Thermal Properties
Transmission of heat and heat capacity
Optical Properties
Absorption, transmission, scattering of light
Chemical Stability
Contact with environment; corrosion resistance
Rank of Characterization of Materials
Processing -> Structure -> Properties -> Performance
Optical Microscopy
Light used to study microstructure
Opaque materials use reflected light, where transparent materials use reflected/transmitted light
Electron Microscopy
Beams of electrons used for imaging
Electrons are accelerated across large voltages
High Velocity electron has wavelength of 0.003 nm
Electron beam focused and images are formed using magnetic lenses
Reflection and transmission imaging both possible
Scanning Electron Microscopy (SEM)
Electron beam scans surface and reflected electrons are collected
Samples must be electrically conductive
Material surface is observed
200,000x magnification possible
Transmission Electron Microscopy (TEM)
Electron beam passes through the material
Thin samples
Details of internal microstructure observed
1,000,000x magnification possible
Scanning Probe Microscopy (SPM)
3D topographical map of material surface
Probe brought into close proximity of material surface
Probe rastered across the surface experiencing deflection in response to interactions with material surface
Useful with many types of materials
X-Ray Diffraction
Form of light that has high energy and short wavelength
Strike a material and scattered in all directions
If atoms in material is crystalline or well-ordered, constructive interference can occur
