Materials Science

What are the two types of solids?

Crystalline solids have ordered molecules and a sharp melting point; amorphous solids have an irregular arrangement of atoms and do not melt suddenly.

What is a unit cell?

The smallest unit that exhibits the full structure of a crystal.

What is the coordination number in a crystalline solid?

The number of other particles that each particle touches in a crystalline solid.

What does the atomic packing factor (APF) represent?

The ratio of the volume occupied by the average number of atoms in a unit cell to the volume of the unit cell; the higher the APF, the more malleable/ductile the material.

How is the APF calculated?

APF = (N atoms * V atom) / (V unit cell)

Describe the FCC structure. What are its characteristics?

Face-centered cubic unit cell; coordination number is 12, contains 4 atoms, occupies 74.04% space, and has an APF of 0.74.

Describe the BCC structure. What are its characteristics?

Body-centered cubic unit cell; coordination number is 8, contains 2 atoms, occupies 68% space, and has an APF of 0.68.

Describe the HCP structure. What are its characteristics?

Hexagonal close-packed; coordination number is 12, contains 6 atoms, occupies 74.04% space, and has an APF of 0.74.

What is X-ray diffraction used for?

A non-destructive technique used to analyze the physical properties of a crystalline structure by measuring the intensity of X-rays that are scattered off the material.

What is Bragg's Law?

nλ = 2d sin θ, where n is an integer, λ is the wavelength of the incident rays, d is the distance between crystal planes, and θ is the angle of incidence.

What is ionization energy?

The minimum amount of energy needed to remove an electron from an isolated atom or molecule.

What is lattice energy?

The energy needed to separate a mole of an ionic solid into a gas of its ions.

How does the radius ratio rule define crystal structures?

It defines the critical radius ratio for different crystal structures based on their coordination geometry, and only applies to ionic substances.

What is the difference between stress and strain?

Stress is the external force acting on the unit area of a material, while strain is the effect of stress on a body.

What is the equation for stress?

σ = F / A, where σ is stress, F is the force applied, and A is the area on the surface.

What does Young's modulus represent?

A mechanical property of a solid material that tells us how easily the material can stretch or deform; it's the ratio of tensile stress to tensile strain.

What is yield strength?

A measurement of the maximum stress that can be applied to a material before it permanently deforms.

What is thermal conductivity?

The ability of a material to transfer heat from one location to another without the movement of the material itself.

What does thermal expansion refer to?

When an object gets larger due to a temperature change.

What is the purpose of tensile testing?

A destructive test process that provides information about the tensile strength, yield strength, and ductility of the material.

What is the difference between thermoplastics and thermosets?

Thermoplastics can be molded when heated and solidify upon cooling, while thermosets permanently harden when heated or cured.

What do fiber reinforcements do in composite materials?

They make the composite material stronger by transferring some of the structural role to fibers with higher modulus and strength.

What is a triple point in phase diagrams?

The condition where all three states of matter coexist.

What is a eutectic phase transformation?

A three-phase reaction where a liquid transforms into two solid phases simultaneously.

What is plastic deformation?

Permanent distortion when a material is subjected to stress that exceeds its yield strength.

What is thermal shock?

When a material is cooled or heated too quickly, increasing the stress and strain on the material.

What is specific heat capacity?

The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius.