Exam 1 Review Flashcards
Amorphous materials can have a BCC crystal structure
False, amorphous materials lack a defined crystal structure. Atoms are arranged randomly with no repeating patterns.
What is a mechanical property a response to?
An applied load
What is an optical property a response to?
Light
What is a deteriorative property a response to?
Chemical reactivity
What are the characteristics of a polymer?
Plastics or rubbers. Organic compounds (C,H) and other non-metallic elements (O,N). Large Chain-like structures. Strong but lightweight.
What are the four molecular structures of polymers?
Linear, branched, crosslinked, and network
In a FCC lattice, the atoms touch along the
face diagonal
True or False: a weakly bonded material will have a shallower energy well and more gradual dF/dr slope
True
What are the four types of copolymers?
Random, alternating, block, graft
If a plane unit cell does not intersect a specific axis, the intercept for that axis is
Infinite
True or false: A deep, narrow energy well likely indicates that a material has a low coefficient of thermal expansion.
True
True or false: Van der Waals are not a primary bond
True
What does it mean that ionic bonding is non-directional?
The magnitude of the bond is equal in all directions around an ion.
True or False: for ionic materials to be stable, all positive ions must have negatively charged ions as nearest neighbors in a three dimensional scheme.
True
True or false: Positive and negative ions attract one another due to a difference in their net electrical charge.
True
What are the types of primary bonds?
Ionic, covalent, metallic
What are the types of secondary bonds?
Van der Waals, dipole, hydrogen honding
What are the types of secondary bonding?
Van der Waals, dipole, hydrogen bonding
Does this describe a schotty or frenkel defect: Vacancies in both the cations and anions in the correct ratio to maintain neutrality.
Schotty defect
Does this describe a Schotty or Frenkel defect: Formed when a cation leaves its lattice site and moves to an interstitial space, no change in charge?
Frenkel defect
The stronger the bond, the _____ the modulus, the _____ the CTE, and the _____ the heat of fusion?
higher, lower, higher
The slope of the bond-force curve at r0 allows you to measure the material’s ___?
stiffness
Name the criteria for a substantial solid solution (Hume-Rothery Rules)
Size difference of <15%, same crystal structure, similar valence, similar electronegativity
The primary bonding in plastics is
covalent
ceramic structures are composed of
ions
What is composed of metallic and non-metallic elements held together by ionic bonds?
Ceramics
True or false: a FCC is more densely packed than a BCC.
True
What is the coordination number of a crystal structure?
The number of nearest neighbor atoms.
What is the degree of polymerization?
The number of repeat units in the polymer, denoted by n.
What is polymorphism?
The fact that some metals and non metals may have more than one crystal structure.
What is N sub v?
The equilibrium number of vacancies
What is N?
The total number of atomic sites.
What is k?
Boltzmann’s constant (eV/atom K)
What is T?
temperature (in K)
What is N sub a?
Avogradro’s number
What is A?
the atomic weight (g/mol)
What is N measured in?
atoms/cubic centimeter
What can the addition of an impurity lead to?
A solid solution or anew phase
What is the solute/impurity atom in a solid solution?
The atom present in the least amount.
What is M sub i?
Mean molecular weight of size range “i”
What is X sub i?
The fraction of the size range
What is N sub i?
number of chains with Mw Mi
