Materials Science and Engineering

Professor Ed Palermo & Professor Chaitanya Ullal

Materials Science & Engineering

Gave a lecture and demos on how different chemical structures and environmental variables affect a material’s properties. Civilization is determined by the advances in materials.

Types of Materials (characterized by performance, properties, processing and structure)

• Metals

• Pure metal (Groups 1-12 + Al, Ga, In, Tl, Sn, Pb, Bi, Po only)
• Ductility Varies
• Opaque
• Crystalline Structure
• Ceramics
• One metal and one nonmetal
• Brittle
• Opaque
• Crystalline Structure
• Glass
• Mostly Silicon Dioxide or “Silica” (Sand)
• Brittle (additives affect how much (Plexiglass / fiberglass) )
• Transparent
• Amorphous Structure
• Polymers
• Plastics
• Long hydrocarbon chains
• Most variable of all materials (Ductile, brittle, transparent, translucent, opaque, etc.)
• Types include PET, HDPE, LDPE, PVC, PP, Polystrene
• He showed us a demo of heat changing HDPE to LDPE

Structure

• Crystalline Materials

• Metals, Ceramics and Some Polymers
• Organized atomic structure
• Prone to defects
• Cubic Structure

• Primitive Cubic (Nothing but the edge vertices of the cube)
• Body-Centered Cubic (Extra atom in center of cube)
• Face-Centered Cubic (Extra atom in center of each face of the cube)

• Hexagonal Packing (Cannonball Problem)

• Most efficient method of stacking objects
• Each atom has six surrounding it
• Structures made of spherical components naturally pack hexagonally

• Amorphous Materials

• Glasses and Some Polymers
• Non-specific atomic structure

• Defects

• Vacancy
• Smaller/Larger atoms
• Differing number of neighboring atoms
• Dislocations – necessary in ductile materials – the dislocation propagates in response to pressure

Properties

• Ductility

• Object’s ability to change shape
• Brittle (Shatters easily) ←→ Ductile (Bends easily)
• Dependent on atomic structure
• Transparency
• Object’s ability for light to pass through it
• Opaque (Cannot see through) ← Translucent → Transparent (Can see through)
• Elasticity
• Object’s ability to absorb force, bend and reanimate back to its original shape
• Inelastic (Does not allow for bending) ←→ Elastic (Allows for bending)

External Factors

• Temperature

• Mostly affects ductility
• Demonstrated through rapid cooling by way of liquid nitrogen and shattering a plastic water bottle
• Demonstrated through rapid heating by way of a torch and blowing a bubble out of the heated plastic of a water bottle

Connections

• Cleanroom

• Structure matters (single crystal versus grain boundaries)
• Potential material change adds advantages and disadvantages
• SME:
• annealing to strengthen with regard to grain boundary structure
• Thermoset versus thermoplastic polymers
• Dr. Chen – polymers and polymer conformation (RNA and proteins)
• Dr. Koratkar – sometimes there are advantages to material defects