Science Olympiad Material Science

Alloy

A metallic material that is obtained by chemical combinations of different elements (e.g. steel is made frm iron and carbon). Typically, have better mechanical properties than pure metals.

Ceramics

A group of crystalline inorganic materials characterized by good strength, especially in compression, and high temperatures. Many have very good electrical and thermal insulation behavior.

Composites

A group of materials formed from mixtures of metals, ceramics, or polymers in such a manner that unusual combinations of properties are obtained (e.g. fiberglass).

Composition

The chemical make-up of a material.

Crystalline Material

A material composed of one or many crystals. In each crystal, atoms or ions show a long-range periodic arrangement.

Density

Mass per unit volume of a material, usually expressed in units of g/cm^3 or lb/in^3.

Fatigue Failure

Failure of a material due to repeated loading and unloading.

Glass

An amorphous material derived from the molten state, typically, but not always, based on silica

Glass-Ceramics

A special class of materials obtained by forming a glass and then heat treating it to form small crystals.

Grain Boundaries

Regions between grains of a polycrystalline material.

Grains

Crystals in a polycrystalline material.

Materials Science and Engineering Tetrahedron

A tetrahedron diagram showing how the performance-to-cost ratio of materials depends upon the composition microstructure, synthesis, and processing.

Mechanical Properties

Properties of a material, such as strength, that describe how well a material withstands applied forces, including tensile or compressive forces, impact forces, tensile or compressive forces, impact forces, cylindrical or fatigue forces, or forces at high temperatures.

Metal

An element that has metallic bonding and generally good ductility, strength, and electrical conductivity.

Microstructure

The structure of a material at the microscopic length scale.

Physical Properties

Characteristics such as color, elasticity, electrical, or thermal conductivity, magnetism, and optical behavior that generally are not significantly influenced by forces acting on a material.

Plastics

Polymers containing other additives

Polycrystalline Material

A material composed of many crystals (as opposed to a single-crystal material that has only one crystal).

Polymerization

The process by which organic molecules are joined into giant molecules or polymers.

Polymers

A group of materials normally obtained by joining organic molecules into giant molecular chains or networks. Characterized by low strengths, low melting temperatures, and poor electrical conductivity. (e.g. rubber, plastics, gels)

Processing

Different ways for shaping materials into useful components or changing their properties

Semiconductors

A group of materials having electrical conductivity between metals and typical ceramics (e.g. Si, GaAs)

Single Crystal

A group of materials that is made up of only one crystal there are no grain boundaries).

Smart Material

A material that can sense and respond to an external stimulus such as change in temperature application of a stress, or change in humidity or chemical environment.

Strength-to-Weight Ratio

The strength of a material divided by density; high = strong but light.

Structure

Description of the arrangement of atoms or ions in a material. Has profound influence on many properties of materials even if overall composition does not change.

Synthesis

The process by which materials are made form naturally occurring or other chemicals.

Thermoplastics

A special group of polymers in which molecular chains are entangled but not interconnected. They can easily be melted and formed into useful shapes. Harden when cooled. Can be melted/cooled over and over unlike thermosets. Normally, these polymers have a chainlike structure (e.g. polyethylene).

Thermosets

A special group of polymers that decompose rather than melt upon heating. They are normally quite brittle due to a relatively rigid, three-dimensional network structure (e.g. polyurethane).

Amorphous

"without form" Solid substance that lacks the definite structure of a crystal. Atoms and molecules don't align in a lattice pattern. Many polymers including glass, gel, and thin films.

Chirality

Chiral molecules are those for which there is another identical molecule arranged as a mirror image (human hands). Achiral molecules are symmetrical when reflected.

Crystallinity

The degree to which a substance's molecules and atoms align. More = less amorphous. High = harder, tougher, and durable. (e.g. polyethylene).

Fluoropolymers

Polymers with fluorine atoms are high-performance plastics used in a variety of intense fields. (e.g. tetrafluoroethylene "Teflon").

Glass Transition Temperature

Temperature at which a polymer changes from a hard material to a soft rubbery substance. Not a distinct temperature, a range over which the polymer chains increase mobility.

Hydrolysis

The process of breaking chemical bonds using water.

Melt Phase

The process when a substance transitions from a crystalline solid to an amorphous liquid through heat or pressure the molecules become less ordered and solid liquefies.

Melting Point

The temperature at which the melt phase of a substance occurs.

Molecular Weight

A number that is related to the length and number of monomer repeats units that comprise a polymer. A polymer material typically has polymer chains of various lengths (average).

Monomer

A molecule that can bond with others of the same kind to form a polymer chain- can form at least two bonds.

Co-Monomers

Two different monomers that bond together.

Morphology

Physical properties of a substance (e.g. shape, size, composition, and phase distribution).

Plasticizers

Substances that may be added to a material to increase its flexibility and resilience. (e.g. Water to clay).

Polydispersity

The degree to which objects in a mixture have varying size, shape, and weight. A uniform mixture contains identical objects, whereas a mixture with a high degree contains widely different objects. To polymers, range of molecular weights that exist in the material.

Solvent

A substance that can dissolve another substance resulting in a solution.

Tensile Strength

the ability of a substance to resist breaking from a pulling force. High = takes great force to cause it to snap by simply pulling on it (e.g. steel beam).

Thermal Stability

A substance's ability to resist breaking down under intense heat. High = withstand high temperatures. When overheat chemical bonds will break and change the substance's properties.

Toughness

"Ability to take a punch" refers to a substance's ability to absorb energy without suffering structural damage or fracturing.

Viscoelasticity

A substance that demonstrates properties of both a fluid and an elastic solid. (e.g. silly putty)

Viscosity

The resistance of a material to flow. High = higher resistance. Low = flow freely. May change depending on temperature. (e.g. Molasses vs Honey)

Stress

Force per unit area.

Strain

The amount of deformation an object experiences compared to its original size and shape.

Young's Modulus

A measure of the stiffness of an elastic material.It is equal to the stress over the strain.

Plastic Deformation

Irreversible deformation, as opposed to the reversible elastic deformation.

Yield Strength

The stress at which a material begins to deform plastically.

Creep Rate

The slow permanent deformation under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material.

Viscosity

A measure of fluids resistance to gradual deformation by stress.

Surface tension

The tendency of fluid to resist external force, caused, by cohesion.

Contact Angle

The angle where a liquid/vapor interface meets a solid surface. It qualifies the wettability of a solid surface by a liquid via the Young equation.

Ionic Bond

The bonding between a non-metal and a metal that occurs when charged atoms (ions) attract after one loses one or more of its electrons.

Covalent Bond

The chemical bond that involves the sharing of pairs of electrons between atoms.

Crystalline

A solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three spatial dimensions.

Semi-Crystalline

A material composed partially of crystalline and partially of amorphous matter.

Amorphous

Also known as a non-crystalline solid, they lack the long-range order characteristic of a crystalline material.

Atomic Packing Factor

The fraction of volume in a crystal structure that is occupied by atoms.