Material Science Practice

Plastic Deformation

Plasticity/Plastic Behavior; the ability of a solid material to undergo permanent deformation, a non-reversible change of shape in response to applied forces

Hardness

1. Measure of resistance to Plastic Deformation

2. Measure of an object’s resistance to scratching, with it being used in Mohs hardness scale

Density

Mass over volume; how tightly molecules are within a structure

Boiling Point

The temperature at which a liquid turns into a gas

Corrosion Resistance

A measure of an object's resistance to corrosion or oxidation

Viscosity

A measure of a liquid or gas’s resistance to movement, caused by friction between molecules, other molecules, and surfaces

Thermal Expansion

A measure of how much an object expands with an increase in temperature of 1 degree

Thermal Conductivity

A material’s ability to conduct heat

Electrical Conductivity

A materials ability to conduct electricity

Elasticity (from Young’s Modulus)

1. A measure of how difficult a material is to deform

2. Higher value indicates greater difficulty

3. Must be positive

4. Decreases at higher temperatures

Elastic Limit

The point at which the stress value becomes too large and the material no longer performs elastically and becomes permanently deformed

Linearity Limit/Proportionality Limit

The stress value beyond which stress is no longer proportional to strain; the end of linearity in a stress-strain diagram

Stress

Measure that describes fores during deformation; the cause of deformation

Strain

Measure of the relative deformation of the material; the response to stress

Ductility

A material’s ability to undergo plastic deformation before fracturing; directly related to temperature

Shear Modulus

Rigidity; Measure of the elastic shear stiffness of a material; the ration of shear stress to shear strain

Bulk modulus

Measure of an object’s resistance to compressibility in all directions

Specific Heat Capacity

Massic heat capacity; The amount of heat that must be added to one unit of mass in a substance in order to cause an increase of one unit in temperature

Can ceramic structures only have one type of bonding?

Ceramic structures can have multiple types of bonding

yield point

the stress point at which a material begins to perform plastically as opposed to elastically

Grain boundaries and their significance

planar defect in polycrystaline solid that seperates regions of different crystal orientations ; important to consider during the construction of structures

Commonly used for shaping ceramics and involves pouring a liquid slurry into a mold

Slip Casting

In a binary phase diagram, what is the significance of the lever rule?

It estimates the relative amounts of each phase in a two-phas region

How porosity can affect the mechanical properties of a cermaic material

Higher porosity decreases the resistance to thermal shock of the material

In the context of electrical conductivity, what is the role of grain boundaries in ceramics?

Decrease electrical conductivity

Are ceramics generally poor electrical conductors?

Ceramics are generally poor electrical conductors.

Can piezoelectric materials generate mechanical stress when an electric field is applied to them?

They can generate mechancial stress when an electric field is applied to them.

Are dielectric materials used primarily because of their ability to conduct electricity well?

They are not used because they cannot conduct electricity well.

Is one of the key applications of piezoelectric materials the production of sensors and actuators?

One of the key applications of piezoelectric materials is the production of sensors and actuators.

Is the dielectric constant the ability of a material to resist electric flow?

The dielectric constant is the ability of a material to resist electric flow.

Are high dielectric constants often used in capacitors to increase their storage capacity?

High dielectric constants are often used in capacitors to increase their storage capacity.

Does aluminum oxide have good insulating properties?

Aluminum oxide does have good insulating properties.

Formula for Saturated Hydrocarbons

2 (number of carbons) + 2 = number of hydrogens

Organic compounds typically have:

low melting points

Atomic Diffusion

Diffusion where thermally-activated atoms can diffuse through a solid (think of air leaving a ballon)

Lattice diffusion

Atomic diffusion within a crystalline lattice by interstitial or substitutional mechanisms

Polymers are primarily _____ in nature

Organic

What is the advantage of glass-ceramics?

Reduced risk of thermal shock

What can be found in nature as a stable dispersion of polymer microparticles?

Latex

Density of water at STP

1000 kg/m³

What is the range of textile strengths exhibited by fibers?

4000-15000

All piezoelectric crystaline solids lack:

Inversion symmetry

What technique is used to study phase transitions in ceramics as a function of temperature?

Differential scanning calorimetry (DSC)

Why is glass transparent?

The amorphous structure disrupts the band gaps that would have absorbed the visible light

Creep

Time-dependent deformation that occurs under sustained stress at elevated temperatures

What does it mean to lap a ceramic?

Using an abrasive surface to remove bits of ceramic to smooth it