2025 Material Science Event Overview and Guidelines

Inter-Atomic Bonding

Different materials have various types of atomic bonds.

Ionic Bonding

Involves transfer of electrons between metals and nonmetals.

Example of Ionic Bonding

Sodium chloride (NaCl) demonstrates ionic bonding.

Covalent Bonding

Atoms share electrons to achieve stable configurations.

Example of Covalent Bonding

Hydrogen molecule (H2) shows covalent bonding.

Bonding Characteristics

Ionic bonds are nondirectional; covalent bonds are directional.

Bonding Energy Range

Ionic bonding energies range from 600 to 1500 kJ/mol.

Materials with Ionic Bonds

Typical materials include ceramics, which are hard and brittle.

Materials with Covalent Bonds

Common in nonmetals and compounds like diamond.

Lab Portion Materials

Supervisors provide materials; students bring safety gear.

Porosity Measurement

Calculate porosity by measuring mass and volume changes.

Electrical Conductivity Testing

Measure resistance of ceramic samples using a multimeter.

Melting Point Measurement

Heat ceramics to determine melting point and bonding type.

Thickness Limit for State

Puck thickness limit is up to 1.0 cm.

Thickness Limit for Nationals

Puck thickness limit is up to 0.5 cm.

Lab Example: Measuring Density

Soak ceramics to measure density before and after.

Lab Example: Testing Conductivity

Measure electrical resistance at room temperature and heat.

Bonding Strength

Varies; strong in diamond, weak in bismuth.

Metallic Bonding

Electrons form a 'sea', allowing conductivity.

Ion Cores

Positively charged nuclei shielded by free electrons.

Conductivity of Metals

Good conductors due to free electrons.

Van der Waals Forces

Weak forces attracting neutral molecules.

Johannes Diderik van der Waals

Physicist who studied real gas properties.

Melting Points and Softness

Lower melting points than ionic or covalent bonds.

Mixed Bonding

Combines covalent, ionic, and metallic characteristics.

Bonding Tetrahedron

Visual representation of four bonding types.

Electronegativity Differences

Greater differences indicate more ionic character.

Unit Cell

Small repeating unit defining crystal structure.

Crystalline Solids

Atoms form repetitive patterns in structure.

Types of Crystal Structures

Includes FCC, BCC, HCP, SC.

Face Centered Cubic (FCC)

Atoms at corners and face centers; densest packing.

Atomic Packing Factor (FCC)

0.74; four atoms per unit cell.

Coordination Number (FCC)

12; each atom surrounded by 12 others.

Body Centered Cubic (BCC)

Atoms at corners and center; less dense than FCC.

Atomic Packing Factor (BCC)

0.68; two atoms per unit cell.

Coordination Number (BCC)

8; each atom surrounded by 8 others.

Hexagonal Close Packing (HCP)

Atoms arranged in hexagonal layers for maximum density.

Hexagonal Close-Packing (HCP)

Arrangement with ABAB layering and 12 coordination.

Atomic Packing Factor (APF)

Ratio of atom volume to unit cell volume.

Simple Cubic (SC)

Basic structure with atoms at unit cell corners.

Coordination Number

Number of nearest neighbors surrounding an atom.

Face-Centered Cubic (FCC)

Structure with 12 coordination and APF of 0.74.

Body-Centered Cubic (BCC)

Structure with 8 coordination from corner atoms.

Crystallinity

Degree of structural order in a solid.

Poly-Crystalline

Materials with both crystalline and amorphous properties.

Amorphous Solids

Lack long-range order, short-range order present.

Defects in Crystalline Materials

Imperfections affecting physical and chemical properties.

Point Defects

Localized disruptions at one or two atomic sites.

Linear Defects

One-dimensional disruptions along a line of atoms.

Interfacial Defects

Two-dimensional boundaries between different crystal regions.

Vitrified Ceramics

Highly crystalline ceramics with ordered structures.

Semi-Crystalline Structures

Contain both crystalline and amorphous regions.

Atomic Volume Calculation

Volume occupied by atoms in a unit cell.

Geometrical Shape of Crystals

Identifiable flat faces and characteristic orientations.

Macroscopic Geometrical Shape

Visible external shape of large crystals.

Characteristic Orientations

Specific angles and arrangements in crystal faces.

Gels and Thin Films

Examples of common amorphous solids.

Vacancies

Missing atoms from lattice sites in ceramics.

Interstitial Cations

Atoms occupying unoccupied lattice interstitial sites.

Impurities

Foreign atoms substituting or occupying lattice sites.

Frenkel Defects

Cation moves to interstitial site, creating vacancy.

Schottky Defects

Equal cation and anion vacancies in lattice.

Edge Dislocation

Extra half-plane of atoms creates localized distortion.

Screw Dislocation

Atoms displaced in a spiral pattern around a line.

Grain Boundaries

Interfaces between grains of different orientations.

Twin Boundaries

Boundaries with mirror symmetry in atomic arrangement.

Phase Boundaries

Boundaries between different phases in ceramics.

Porosity

Void spaces in materials, affecting properties.

Open Porosity

Interconnected pores accessible from the surface.

Closed Porosity

Isolated pores not connected to the surface.

Total Porosity

Sum of open and closed porosity.

Archimedes' Method

Measures volume and displaced fluid volume.

Mercury Intrusion Porosimetry

Injects mercury to determine pore size.

Gas Pycnometry

Uses gas displacement to measure solid volume.

Bragg's Law

Describes conditions for X-ray diffraction in crystals.

X-Ray Diffraction

Technique to study atomic structure via scattering.

Light Microscopes

Use visible light to magnify specimens.

Visible light range

Light wavelength from 400 to 700 nm.

Ocular lens

Lens through which the image is viewed.

Electron Microscope

Uses electron beams for high-resolution imaging.

Electron beam

Approx. 1 nm used for scanning specimens.

Zinc sulfate screen

Displays images from electron microscope projections.

TTT Diagram

Shows material behavior at varying temperatures and times.

X-axis of TTT Diagram

Represents time on a logarithmic scale.

Y-axis of TTT Diagram

Indicates temperature during material processing.

Transformation Lines

Show phase transformations in materials.

Nose Curve

Indicates optimal time and temperature for transformations.

Start Line

Marks beginning of a phase transformation.

Finish Line

Marks completion of a phase transformation.

Isothermal Transformation Region

Area for constant temperature transformations.

No-Transformation Region

No significant phase changes occur here.

Phase change diagrams

Illustrate temperature, pressure, and phases at equilibrium.

Unary phase diagram

Shows phase behavior of a single substance.

Triple point

Point where solid, liquid, and gas coexist.

Binary phase diagram

Depicts phase behavior of two components.

Eutectic point

Specific composition with unique phase transitions.

Eutectoid point

Point where solid phases transform at specific composition.

X-axis of binary phase diagram

Represents composition of two components.

Y-axis of binary phase diagram

Indicates temperature affecting phase behavior.

Single-Phase Regions

Areas with only one phase present.