LECTURE 2.2

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

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)

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

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

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

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

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

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

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

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

“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

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

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

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

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

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

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

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?

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).

ELECTRON DIFFRACTION PATTERNS—THE BEAUTY OF CRYSTALLINE PERFECTION!