1. LECTURE 2.2

2. From the Sublime to the Ridiculous!
CLASSIFICATION OF MATERIALS II: THE (MICROSCOPIC) STRUCTURE OF MATERIALS
From the Sublime to the Ridiculous!

3. THE MICROSCOPES The Light Microscope
The Scanning Electron Microscope (SEM)
The Transmission Electron Microscope (TEM)
The Atomic Force Microscope (AFM)
The Field-Ion Microscope (FIM)

4. THE SPACE SHUTTLE
The skin of the Space Shuttle must withstand temperatures in excess of 1200˚C
The “tiles” are made from a silica (SiO2) glass
Amorphous Ceramic/Glass

5. THE SPACE SHUTTLE TILE SEM image of the silica (SiO2) fibers
Non-Metallic
Inorganic
Amorphous
Synthetic
Ceramic
Amorphous Ceramic/Glass

6. THE MACROSTRUCTURE OF A DIAMOND
SEM Image (false color) of a small, synthetic diamond
The shape of the diamond is an “octahedron”
Many naturally occurring diamonds are also octahedral.
Non-Metallic
Inorganic
Crystalline
Synthetic
Ceramic
Crystalline Ceramic

7. GRAPHITE: AN UNUSUAL CERAMIC
A Non-Metallic, Elemental Solid
Non-Metallic
Inorganic
Crystalline
Natural
Ceramic
Crystalline Ceramic:
Natural Ceramic

8. THE ODESSA METEORITE Native Metal/Crystalline Metal
Iron-nickel (~95%fe - 5%ni)
Scanning electron microscope (SEM) image
Two different polymorphs of iron: austenite and ferrite
Note the scale marker
The finger-like mixture of austenite and ferrite is called plessite
Metallic
Inorganic
Crystalline
Naturally Occurring
Metal
Native Metal/Crystalline Metal

9. SECTIONED ALUMINUM CASTING
The casting solidified or “crystallized” from the “outside-in”
The casting is “polycrystalline”,
The term “polycrystalline” means “consisting of many small, differently oriented grains, or crystals”
Metallic
Inorganic
Crystalline
Synthetic
Metal
Crystalline Metal

10. BRONZE (COPPER-TIN) POWDER
SEM image of bronze powder
Metallic
Inorganic
Crystalline
Synthetic
Metal
Crystalline Metal

11. PARTIALLY SINTERED STEEL
Steel: iron with ~ 0.8% carbon
Light micrograph
The powder particles have begun to sinter
There is much “residual porosity”
Metallic
Inorganic
Crystalline
Synthetic
Metal
Crystalline Metal

12. “DISLOCATIONS” IN ALUMINUM
A “transmission electron microscope” (TEM) image of dislocations in aluminum
Dislocations are “atomic-scale” defects that disrupt the crystalline perfection of the aluminum
Metallic
Crystalline
Metal
Synthetic
Crystalline Metal

13. IMAGES OF ATOMS I
Field-ion microscope (FIM) image of atoms of tungsten
Each “bright spot” corresponds to a tungsten atom
The atom was first “seen” at Penn State, in the 1950s, by professor Irwin Mueller
Note that the tungsten is crystalline.
Metallic
Inorganic
Crystalline
Synthetic
Metal
Crystalline Metal

14. IMAGES OF ATOMS II Atomic force microscope (AFM) image of gold atoms
Metallic
Inorganic
Crystalline
Synthetic
Metal
Crystalline Metal

15. POLYPROPYLENE 200µm Light microscope image of polypropylene
The thin polymer film was crystallized from an initially amorphous film
Each “crystal” is seen to radiate from a “nucleation site,” until adjacent crystals impinge
Non-metallic
Organic
Crystalline
Synthetic
Polymer
200µm
Crystalline Polymer

16. HIGH DENSITY POLYETHYLENE
Light microscope image of “high density polyethylene” (HDPE)
The thin polymer film was crystallized from an initially amorphous (LDPE) film
Each “crystal” is seen to radiate from an “nucleation site,” until adjacent crystals impinge
Non-Metallic
Organic
Crystalline
Synthetic
Polymer
Crystalline Polymer

17. CASHMERE SEM image of a single thread of cashmere Non-Metallic Organic
Crystalline (?)
Natural
Polymer
Natural Polymer/Crystalline Polymer

18. THE COLUMNS OF STEIDLE BUILDING I
The columns of Steidle Building are constructed from “drums” of sandstone
Sandstone is a naturally occurring composite
Sandstone is also a ceramic
Sandstone is a rock!
Non-Metallic
Inorganic
Crystalline
Naturally Occurring
Rock/Composite
Ceramic/Ceramic Composite:
Natural Ceramic:
Crystalline Ceramic

19. THE COLUMNS OF STEIDLE BUILDING II
At low magnification, the original sand (quartz) grains are seen
The quartz grains are somewhat less than 1mm in size
But what caused the sand to “lithify?” What material “sintered” the sand grains together? What is the “cement” which binds the composite into a “monolithic” material?

20. THE COLUMNS OF STEIDLE BUILDING III
At high magnification, a “plate-like” phase is seen in the spaces between the sand grains.
The “cement” that sinters the sand grains together is called Calcite: calcium carbonate (CaCO3).

21. ELECTRON DIFFRACTION PATTERNS—THE BEAUTY OF CRYSTALLINE PERFECTION!