Materials Science Review: Polymers, Ceramics, Composites, Corrosion, Electrical, Light, and Magnetism

Comprehensive vocabulary flashcards covering seven chapters of material science, including polymers, ceramics, composites, corrosion, electrical, optical, and magnetic properties.

Monomer

A small molecule (often containing a carbon–carbon double bond or functional groups) that can chemically react with other monomers to form a polymer.

Polymer

A large molecule made of repeating monomer units connected by covalent bonds into long chains.

Repeat Unit (Mer)

The basic repeating structure within a polymer chain that comes from the original monomer.

Thermoplastic

A polymer consisting of long chains with no cross-links, held together by secondary forces; they can move when heated, allowing the material to melt and be reshaped.

Thermoset

A polymer in which chains are connected by permanent covalent cross-links, forming a rigid 3D network; they do not melt when heated and instead degrade.

Cross-links

Covalent bonds between polymer chains that restrict chain motion, increasing stiffness, strength, and heat resistance.

Branches

Side chains attached to the main polymer backbone that can affect packing, density, and mechanical properties.

Addition Polymerization

A process where monomers with carbon–carbon double bonds ($C=C$) react to form a polymer without producing a byproduct; steps include initiation, propagation, and termination.

Condensation Polymerization

A process where monomers with functional groups react to form a polymer while releasing a small molecule such as water; requires difunctional monomers.

Homopolymer

A polymer made from only one type of monomer.

Copolymer

A polymer made from two or more different monomers, arranged in patterns such as alternating, block, random, or graft.

Degree of Polymerization (DP)

The number of repeat units in a polymer chain, calculated as DP = rac{\text{molecular weight of polymer}}{\text{molecular weight of repeat unit}}.

Average Molecular Weight

The average mass of polymer chains, accounting for chains of different lengths.

Viscoelasticity

Behavior where a polymer exhibits both an elastic (solid-like) response and a viscous (fluid-like) response.

Stress Relaxation

The decrease in stress over time when a polymer is held at constant strain due to molecular rearrangement.

Glass Transition Temperature ($T_g$)

The temperature at which a polymer changes from glassy (rigid, brittle) to rubbery (flexible).

Melting Temperature ($T_m$)

The temperature at which crystalline regions of a polymer melt and the material becomes a viscous liquid.

Elastomer

A polymer with light cross-linking that allows large elastic deformation (rubber-like behavior).

Vulcanization

A process that introduces cross-links (typically sulfur) into rubber to improve strength, elasticity, and thermal stability.

Extrusion

A process where molten polymer is forced through a die to create continuous shapes like pipes or sheets.

Ceramic

An inorganic, non-metallic material composed of metal and nonmetal elements, bonded primarily by ionic and/or covalent bonds, typically processed at high temperatures.

Radius Ratio

The ratio of cation radius to anion radius ($\frac{r_{cation}}{r_{anion}}$), which determines which crystal structure forms.

Coordination Number

The number of nearest neighbor ions surrounding a central ion, determined by the radius ratio.

Critical Radius

The minimum radius ratio required for a stable coordination structure; the structure becomes unstable if the cation is too small.

Deformation in Ceramics

Highly limited because slip systems are restricted and ionic charge balance (electroneutrality) must be maintained.

Sintering

Heating particles below their melting point so they bond together via diffusion, resulting in increased strength and reduced porosity.

Vitrification

The formation of a glassy phase during heating that fills pores and binds particles, increasing density and strength.

Slip Casting

A manufacturing method where a liquid ceramic slurry is poured into a mold; water is absorbed, leaving a solid shape.

Piezoelectric Ceramics

Materials that generate electrical charge when mechanically stressed and vice versa.

Glass

An amorphous ceramic characterized by no long-range order, typically based on silica ($SiO_2$) and modifiers like $Na_2O$ or $CaO$.

Strain Point

The temperature below which glass behaves as a rigid solid and internal stresses no longer relax.

Composite

A material made by combining two or more distinct materials (macroconstituents) to achieve improved properties the individual materials alone cannot provide.

Matrix

The continuous phase that holds the composite together, transfers load to the reinforcement, and protects the reinforcement.

Reinforcement

The strong phase (fibers or particles) that carries most of the load and provides strength and stiffness.

Anisotropic

A material state where properties depend on direction; a key concept for composites.

Rule of Mixtures (Parallel to Fibers)

Used when the load is along the fiber direction: $E_c = V_fE_f + V_mE_m$.

Inverse Rule of Mixtures (Perpendicular)

Used when the load is perpendicular to fibers, resulting in lower stiffness: $E_c = (\frac{V_f}{E_f} + \frac{V_m}{E_m})^{-1}$.

Sandwich Structure

A composite with strong outer layers (faces) and a lightweight core, providing high stiffness with low weight.

Prepreg

Fibers pre-impregnated with resin before shaping.

Corrosion

The deterioration of a material (usually a metal) due to chemical or electrochemical reactions with its environment.

Oxidation

The loss of electrons ($M \rightarrow M^{n+} + e^-$) which happens at the anode.

Reduction

The gain of electrons ($X + e^- \rightarrow X^-$) which happens at the cathode.

Anode

The location where oxidation occurs and where corrosion happens.

Standard Electrode Potential

A measure of a material's tendency to lose electrons (oxidize) compared to a hydrogen reference (0 V).

Nernst Equation

Used for non-standard conditions to account for ion concentration effects: $E = E^0 + \frac{0.0592}{n} \log(C)$.

Pitting Corrosion

A dangerous form of localized corrosion that results in the formation of holes.

Oxygen Concentration Cells

A microscopic corrosion mechanism where high oxygen areas act as the cathode and low oxygen areas act as the anode (and corrode).

Faraday’s Law

Used to calculate mass loss due to corrosion: $W = \frac{ItM}{nF}$.

Cathodic Protection

A prevention method that makes the metal the cathode so it doesn't corrode.

Passivation

The formation of a protective oxide layer on a material's surface that slows corrosion.

Electrical Conduction

The movement of charge carriers (electrons or holes) through a material under an applied electric field.

Ohm’s Law

The relationship describing current flow: $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance.

Resistivity ($\rho$)

An intrinsic material property measuring resistance: $\rho = \frac{RA}{l}$, where $A$ is cross-sectional area and $l$ is length.

Conductivity ($\sigma$)

The ability of a material to conduct electricity, defined as $\sigma = \frac{1}{\rho}$.

Drift Velocity ($v_d$)

The average velocity of electrons moving under an electric field: $v_d = \mu E$, where $\mu$ is mobility and $E$ is electric field.

Band Gap ($E_g$)

The energy required for electrons to jump from the filled Valence Band to the empty Conduction Band.

Doping

The intentional addition of impurity atoms to a semiconductor to create N-type (extra electrons) or P-type (holes) charge carriers.

Photon

A discrete packet or quantum of light energy; used in the packet model where light energy is not continuous.

Wien’s Law

Relates temperature to the peak wavelength of light: $\lambda_{max}T = 2900 \, \mu m \cdot K$.

Critical Wavelength ($\lambda_c$)

Determined by band gap energy ($E_g$) as $\lambda_c = \frac{hc}{E_g}$. If \lambda > \lambda_c, there is no absorption.

Energy Balance Equation (Optical)

Describes the outcomes of incident light: $I_0 = I_r + I_a + I_t$, representing incident, reflected, absorbed, and transmitted intensities.

Phosphorescence

An optical phenomenon where light is absorbed and then re-emitted slowly, creating a delayed glow.

Index of Refraction ($n$)

A measure of how much light slows down in a material: $n = \frac{c}{v}$, where $c$ is the speed of light in a vacuum.

Diamagnetic

Materials weakly repelled by magnetic fields with no permanent magnetism, caused by induced currents opposing the field.

Paramagnetic

Materials weakly attracted to magnetic fields; they possess unpaired electrons with random orientations and are only magnetic when a field is applied.

Ferromagnetic

Strongly magnetic materials with aligned electron spins in regions called domains; they can become permanent magnets.

Magnetic Domain

A region where magnetic moments (spins) are aligned in the same direction.

Exchange Interaction

The phenomenon where electron wave functions overlap, causing spins to align and lower the energy, giving rise to ferromagnetism.

Curie Temperature ($T_c$)

The temperature above which a material loses its magnetic properties (domain alignment) and becomes paramagnetic.

Coercivity ($H_c$)

The amount of external magnetic field required to demagnetize a material.

Soft Magnetic Materials

Magnetic materials that are easy to magnetize and demagnetize and have low coercivity.

Hard Magnetic Materials

Magnetic materials that are hard to demagnetize and are used for permanent magnets.