Materials Science: Polymers, Ceramics, Glasses, and Metals

Vocabulary practice flashcards covering polymers, ceramics, glasses, phase diagrams, solid solution strengthening, work hardening, and annealing processes.

Polymer

A long, chain-like organic molecule composed of repeating structural units, typically possessing molecular weights ranging from $10,000$ to more than $1 \times 10^6\,\text{g/mol}$.

Polymerization

The chemical process by which smaller monomer molecules are joined together to create long polymer chains.

Thermoplastic Polymer

A polymer consisting of flexible linear chains that exhibits plastic, ductile behavior and is softened and formed by viscous flow when heated.

Thermoset Polymer

A polymer consisting of a rigid three-dimensional network of strongly cross-linked molecular chains that has no fixed melting temperature, is stronger and more brittle than thermoplastics, and cannot be easily reprocessed.

Elastomer

A polymer composed of linear cross-linked chains capable of undergoing enormous elastic deformation under an applied load and returning to its original shape once the load is removed.

Hydrocarbon

An organic chemical compound composed entirely of carbon and hydrogen atoms.

Alkane

A saturated hydrocarbon containing only single covalent carbon-carbon bonds, such as methane and ethane.

Alkene

An unsaturated hydrocarbon containing one or more carbon-carbon double bonds, such as ethylene and propylene.

Addition Polymerization

A rapid chain-growth polymerization process in which monomers are linked together without producing byproducts, typically by breaking unsaturated carbon-carbon double bonds.

Condensation Polymerization

A polymerization reaction that combines two different monomers to produce a polymer chain while releasing a small molecular byproduct (such as methyl alcohol or water).

Vulcanization

An irreversible chemical process that introduces cross-linking strands of sulfur atoms between polymer chains; adding more sulfur produces a harder, more rigid, and more brittle elastomer.

Polymer Branching

A structural occurrence where an atom attached to the main linear chain is replaced by another linear chain branch, hindering dense chain packing and crystallization.

Ceramics

Inorganic solid materials composed of compounds containing metallic and non-metallic elements held together by strong ionic or covalent bonds.

Compaction (Ceramic Processing)

The step in ceramic manufacturing where ceramic compound is ground to target particle size, mixed with binding agents, and pressed into a cohesive shape prior to binder removal and firing.

Sintering

A high-temperature firing process carried out below the melting temperature where ions diffuse across particle boundaries, bonding particles, shrinking pores, and increasing material density.

Vitrified Structure

A ceramic microstructure in which crystalline grains are held together by an amorphous glassy or organic bonding phase.

Glass

A rigid, solid material that has hardened and cooled from a molten state without crystallizing, retaining a random amorphous structure.

Glass Transition Temperature ($T_g$)

The critical transition temperature at which an undercooled liquid transforms into a disordered, rigid amorphous solid with immobile molecular segments.

Solid Solution Strengthening

A strengthening mechanism in metals and ceramics achieved by intentionally dissolving substitutional solute atoms into a solvent lattice to disrupt the crystal structure and impede dislocation movement.

Phase

A homogeneous region of material characterized by identical atomic arrangement, roughly uniform composition and properties, and a definite interface separating it from adjacent regions.

Unary Phase Diagram

A phase diagram describing the thermodynamic phase equilibrium of a single-component system as a function of temperature and pressure.

Unlimited Solubility

The condition in which two components completely dissolve into each other in all proportions in both the liquid and solid states, producing only a single phase.

Isomorphous Phase Diagram

A binary equilibrium phase diagram in which the two components display complete solid solubility, resulting in only one solid phase across the entire composition range.

Liquidus Temperature

The upper boundary curve on a phase diagram above which an alloy or ceramic system is entirely liquid.

Solidus Temperature

The lower boundary curve on a phase diagram below which an alloy or ceramic system is completely solid.

Tie Line

An isothermal horizontal line drawn across a two-phase region of a phase diagram at the temperature of interest to determine the equilibrium chemical compositions of both coexisting phases.

Lever Law

A quantitative rule used to calculate the relative phase fraction in a two-phase region, expressed as: $\text{Phase percent} = \frac{\text{opposite arm of lever}}{\text{total length of tie line}} \times 100\%$.

Work Hardening (Strain Hardening)

A process where a metal is plastically deformed at low temperatures (cold working), increasing dislocation density and entanglement to enhance strength while lowering ductility.

Grain Size Strengthening

A strengthening mechanism in polycrystalline metals where decreasing grain size (increasing the number of grain boundaries) increases the required deformation force by disrupting lattice continuity.

Drawing (Metalworking)

A cold-working forming operation in which a metal rod, wire, or polymer is pulled through a tapered die under tension to reduce its cross-sectional area.

Annealing

A heat-treatment process designed to reverse the effects of cold working by restoring softness and ductility through recovery, recrystallization, and grain growth.

Recovery (Annealing)

The low-temperature stage of annealing where tangled dislocations utilize thermal energy to rearrange into lower-energy boundaries, relieving internal residual stress without decreasing strength.

Recrystallization

The annealing stage occurring above the recrystallization temperature in which new, strain-free, equiaxed grains nucleate and consume the deformed cold-worked microstructure, substantially reducing strength and restoring ductility.

Recrystallization Temperature

The minimum temperature at which cold-worked grains begin transforming into new, strain-free, dislocation-free grains.

Grain Growth (Annealing)

The high-temperature final stage of annealing where larger grains coarsen and consume smaller grains to lower boundary surface energy, causing an undesirable decrease in material strength.

Hot Working

Plastic deformation of a metal conducted at temperatures above its recrystallization temperature, enabling almost unlimited deformation without strain hardening while yielding poorer surface finish and tolerance control than cold working.