matsci flashcards

Materials Science

Investigates the relationships between structure and properties of materials

Materials Engineering

Involves designing the structure of a material for specific properties

Materials Scientist

The role is to develop or synthesize new materials

Structure

Refers to the arrangement of a material's internal components

Subatomic, atomic, microstructure, macrostructure

Four types of material structure

In-service condition

First criteria for material evaluation

Deterioration

Second criteria for material evaluation

Economics

Third criteria for material evaluation

Material Property

While in use a material is subjected to an external stimulus that results in a particular response

Mechanical properties

Deformation in response to applied force

Electrical properties

Response to an electric field

Thermal properties

Response to heat

Magnetic properties

Response to a magnetic field

Optical properties

Response to light radiation

Processing, Structure, Properties, Performance

Four components in material science

Metals, Ceramics, Polymers, Composites, Advanced materials

Major material groups

CFRP (Carbon fiber reinforced polymer)

Stiff and strong material

High Technology

device or product that uses intricate and sophisticated principles

Semiconductors

have electrical properties that are intermediate between conductors (metals, metal alloys) and insulators (ceramics, polymers)

Biomaterials

Used to replace body parts

Smart materials

materials that are able to sense changes in their environment and respond to the changes in a predetermined manner

Shape-memory alloys

are metals that after being deformed revert back their original shape when temperature is changed

Piezoelectric ceramics

expand and contract when exposed to an electric field; they also generate an electric field when their dimensions are changed

Magnetostrictive materials

has the same behavior as piezoelectric ceramics when exposed to a magnetic field

Nanomaterial

Material with nanometer dimensions

Atomic number (Z)

Number of protons in the nucleus

Atomic Mass (A)

Sum of protons and neutrons

Isotopes

Elements with different neutron numbers

Bohr Atomic Model

Proposed by Niels Bohr

Quantum Mechanics

Principles for atomic entities

Valence electrons

Electrons in unfilled shells

Ionic Bonding

Occurs between metallic and non-metallic elements

Covalent bonding

Sharing of electrons between atoms

Metallic Bonding

Valence electrons are free to drift

Electric dipole

Separation of charges in an atom

Polar molecules

Have permanent dipoles

Catalytic Converter

Reduces pollutants in car exhaust

Point defects, Line defects, Area defects

Types of imperfections in materials

Dislocations

Cause permanent deformation in materials

Interfacial defects

Boundaries separating regions with different structures

Metals

arranged in an orderly manner

Ceramics

are compounds between metallic and non-metallic elements

Polymers

many are organic compounds that are chemically based on carbon, hydrogen, and other non-metallic elements (e.g. O, N, Si)

Composites

the objective is to have a combination of properties not available in any single material

Advanced Materials

materials used in high technology applications

electrorheological/magnetorheological fluids

experience changes in viscosity when exposed to electric or magnetic fields

Vacancies, Self-interstitial, Substitutional

Types of point defects

Dislocations

slip between crystal planes result when dislocations move, produce permanent (plastic) deformation.

Edge dislocation

extra half-plane of atoms inserted in a crystal structure. Perpendicular (⊥) to dislocation line

Screw dislocation

spiral planar ramp resulting from shear deformation. Parallel (||) to dislocation line

Burger’s vector (b)

measure of lattice distortion

Crystalline Material

Material in which its atoms are arranged in a repeating or periodic array

Noncrystalline/Amorphous

long range order is absent

Crystal structure

manner in which atoms, ions or molecules are arranged

unit cell

basic structural unit or building block of the crystal structure

Parallelipipeds

Most unit cells are __

Coordination number

refers to the nearest neighbor or touching atoms

Atomic packing factor

vol. of atoms per unit cell/volume of unit cell

lattice

three-dimensional array of points coinciding with atom positions

Simple cubic structure

Structure that is rare due to its low packing density

Body centered cubic strucuture

atoms touch each other along cube diagonals

Polymorphism

occurs when a metal or a nonmetal possess more than one crystal strucuture

Allotropy

if the metal is an elemental solid

Polycrystals

most engineering materials are ___

Diffusional processes

(conducted at elevated temperatures) are often utilized to introduce impurity atoms into silicon semiconductors

Diffusion

the phenomenon of material transport by atomic motion

Diffusion couple

which is formed by joining bars of two different metals together so that there is intimate contact between the two faces;

Interdiffusion/impurity diffusion

atoms of one metal diffuse into another

self-diffusion

Diffusion also occurs for pure metals, but all atoms exchanging positions are of the same type

vacancy diffusion

interchange of an atom from a normal lattice position to an adjacent vacant lattice site or vacancy

interstitial diffusion

type of diffusion involves atoms that migrate from an interstitial position to a neighboring one that is empty

steady-state diffusion

Diffusion in which the diffusion flux does not change with time

diffusion flux

it is necessary to know how fast diffusion occurs, or the rate of mass transfer. This rate is frequently expressed as ___

concentration profile

When concentration C is plotted versus position (or distance) within the solid x, the resulting curve is termed the ___

concentration gradient

the slope at a particular point on this curve on the concentration profile

Diffusion coefficient

The constant of proportionality D

Fick’s first law

substances will diffuse from areas of high concentration to lower concentration

driving force

is used in the context of what compels a reaction to occur

Ficks second law

predicts how diffusion causes the concentration to change with respect to time

Carburizing

a thermo-chemical process in which iron or steel absorbs carbon from a carbon-bearing material at processing temperatures between 850–1000°C, with the intent of hardening the metal

electron configuration

represents the manner in which these states are occupied of an atom

Crystalline defect

refers to a lattice irregularity having one or more of its dimensions on the order of an atomic diameter

solid solution

The addition of impurity atoms to a metal will result in the formation of

Grain Boundaries

boundary separating two small grains or crystals having different crystallographic orientations in polycrystalline materials

Phase boundaries

wherein a different phase exists on each side of the boundary; furthermore, each of the constituent phases has its own distinctive physical and/or chemical characteristics

twin boundary

A special type of grain boundary across which there is a specific mirror lattice symmetry; that is, atoms on one side of the boundary are located in mirror-image positions of the atoms on the other side