Midterm 1 (ch.1-3) Flashcards
What are the types of material properties?
- mechanical
- physical (electric, magnetic, optical, thermal, elastic, chemical)
- transport
- radiation response
What is a structure-insensitive property?
one that does not depend on the mass of the substance or system
What are examples of structure-intensive properties?
- temperature, pressure, density
- elastic modulus
- thermal coefficient of expansion (TCE) - (may change depending on porosity and texturing)
- specific gravity
What is a structure-sensitive property?
- a property that depends on impurities and the imperfection of the crystal structure of a material
What are some examples of structure-sensitive properties?
- yield strength
- thermal conductivity
electrical resistivity - fracture toughness
What do material sciences and engineering study?
- different types of materials
- the structure-property-process relationships
What are the different types of materials?
- metals
- ceramics/ glasses
- polymers
- composites
- semiconductors
What are examples of metals?
- iron
- copper
- aluminum
- silver
- gold
Metals description
atoms located in regularly defined, repeating positions (crystal), have free electrons
Metals strengths (pros)
- good electrical conductors
- strong
- ductile
Define Ductile
- term for materials that can absorb energy by “bending” rather than by fracture when subject to external loads
- (able to be drawn out into a thin wire/ plasticity)
Metals weaknesses
- dense
- moderate temperature resistance
Ceramics/glasses examples
- sand
- dinnerware
- window glass
- graphite
- sanitary ware (toilets, bathtubs, etc)
Ceramics/ glasses description
- combination of metallic and non-metallic atoms
- some ceramics are crystalline
Ceramics/ glasses strengths (pros)
- very strong and moderate density
- high temperature stability
- chemically resistant
Ceramics glasses weaknesses
- no free electrons (not conductive)
- brittle
Polymers examples
- nylon
- cellulose
- Teflon
- kevlar
- polystyrene
Polymers description
- long chain molecules with repeating groups
- can be ductile or brittle
Polymers strengths (pros)
- low density
- easy to form into complex shapes
- inexpensive
Polymers weaknesses
- low strength
- temperature sensitive
Composites examples
- Carbon/carbon
- Carbon/epoxy
- plywood
- steel belted tires
Composites description
- 2+ materials combined
Composites strengths (pros)
- strong and rigid
- low density
Semi-conductors examples
- silicon
- germanium
- GaAs
- CdTe
- InP
Semi-conductors description
- bonding and mechanical properties similar to ceramics
- conductive
Semi-conductors strengths (pros)
used in electronic and optical devices
Define brittle
- unable to absorb energy from external loads by bending
- fracture easily
Define conductivity
the ease with which electric charge is transported through a material in response to an external electric field
Define stiff
an object is rigid as it resists bending
Define crystalline
having atoms or ions arranged on a 3D lattice having long-range order
Define amorphous
lacks the long-range order that is characteristic of crystalline solid
- either rubbers or glasses
what are the main components of an atom?
protons, neutrons, and electrons
What are the properties of an atom determined by?
- the atomic mass number (Z)
- mass of the atom
- spatial distribution of electrons in orbits
- energy of the electrons
- ease of adding or removing an electron to make a charged atom
What atomic properties can be changed by an external field?
- spatial distribution of electrons in orbits
- energy of the electrons
- ease of adding or removing an electron to form an ion
What kind of characteristics do electrons exhibit?
characteristics of particles and waves
What is the principle quantum number?
- n
- integer number (1,2,3…)
- refers to shell/ energy level
- K: n=1; L: n=2; M: n=3
What is the Azimuthal quantum number?
- l
- assigned numbers from l=0 (n-1)
- refers to sub-shell
- s: l=0; p: l=1; d: l=2; f: l=3
What is the magnetic quantum number?
- m
- assigned numbers between positive and negative l
- total number = (2l+1)
What is the spin quantum number?
- M s (M sub s)
- either +1/2 or -1/2
- reflects the different electronic spins of an electron
Which quantum numbers are the energy of a shell primarily dependent on?
- n and l
What is the periodic table trend of electronegativity?
it increases from left to right and upwards in the periodic table
What does electronegative describe; what kind of elements?
elements with high electronegativity (non-metals)
What does electropositive describe; what kind of elements?
elements with low electronegativity (metals)
What is electronegativity difference? What does it determine?
- the difference between 2 elements’ electronegativities
- determines bond type between those elements
What change in electronegativity values correspond with different bonds?
> 1.7 = ionic bond
0.6-1.7 = polar covalent bond
<0.6 = nonpolar covalent bond
What does primary bonding determine?
physical, mechanical, and chemical properties
What does primary bonding involve in terms of electrons?
a transfer or sharing of outer electrons
Are atoms shared or transferred with ionic bonding?
transferred
What are some properties of ionic bonds?
- non-directional bond
- low electrical conductivity
- brittle
- high melting temperature
- happens when ions of opposite charge attract as a result of coulombic attraction
Are electrons transferred or shared in covalent bonds?
shared
What are some properties of covalent bonds?
- directional bonds
- low electrical conductivity
- very hard/strong
- high melting temperature
- > or equal to 4 valence electrons
Are electrons shared or transferred in metallic bonds
shared
What are some properties of metallic bonds?
- non-directional bonds
- good electrical conductivity (free electrons)
- ductile and opaque
- <3 valence electrons
