BME 318 Practice Exam 1 Questions Multiple Choice
Self-Interstitial Point Defect
"Extra" atoms positioned between atomic sites occupying a space that would normally be empty
What are the three types of polymerization?
(1) Addition (2) Condensation (3) Genetic engineering methods (insert genes, peptide synthesis via ribosome)
What are the three steps of ADDITION Polymerization?
(1) Initiation (light, heat, catalyst) (2) Propagation = attachment of monomer at the ends of the "active" chain (3) Termination = coupling, disproportionation (transfer of hydrogen atom from one growing chain to another
What are the 4 different types of polymer structures?
(1) Linear (2) Branched (3) Crosslinked (4) Network
What are the two types of Point Defects?
(1) Vacancies (2) Self-Interstitials
Which of the following is NOT true about fatigue? (a) It is tested using a rotating-bending apparatus (b) Only some materials have a fatigue limit (c) The fatigue life is the number of cycles required to cause fatigue fracture at a specified stress (d) Fatigue strength is the stress level that will cause failure after a given number of cycles (e) All are true
(b) Only some materials have a fatigue limit
Which of the following is NOT true about fatigue? (a) It is tested using a rotating-bending apparatus. (b) All materials have a fatigue limit. (c) The fatigue life is the number of cycles required to cause fatigue fracture at a specified stress. (d) Fatigue strength is the stress level that will cause failure after a given number of cycles. (e) All are true.
(e) All are true.
Characteristics of ADDITION polymerization
* Free radical polymerization - Random termination * Ionic polymerization - Termination via reactions with water/solvent = less polydisperse than free radical
Suspension Polymerization
- Aqueous solution with nonsoluble monomers/initiators - Mechanical agitation - Reaction in droplets = polymeric beads - Can help with heat dissipation
What are the requirements for ADDITION polymerization?
- Bifunctional monomers - Initiator = free radical/anion/cation
Methods of Polymer Synthesis
- Bulk - Solution - Suspension - Emulsion - Solid-State - Gaseous - Plasma
Copolymers
- Composed of more than one monomer
Homopolymers
- Composed of one monomer
What are the two types of molecular compositions of polymers?
- Homopolymers - Copolymers
Emulsion Polymerization
- Hydrophobic monomer, water soluble initiator and surfactant (emulsifier) with stirring - Polymer beads/rods
Solution Polymerization
- Include organic solvent with thermal conductivity - Helps with heat dissipation - Low yield and need to remove solvent
Characteristics of CONDENSATION polymerization
- Long reaction time required to generate high MW - Random termination - Ex: Nylons and polycarbonates - Type of step growth polymerization
Bulk Polymerization
- Monomer + initiator - High yield and high purity - Issues with heat dissipation
Types of Copolymers
- Statistical - Random - Alternating - Block - Graft
What are coordination numbers for FCC, BCC, HCP (hexagonal close packing) cubic structures?
12, 8, 12
What is an unsaturated polymer?
2 carbon atoms in "mer" unit are bonded with double bonds
What is an oligomer?
A molecule containing 2-10 "mer" units
What is a polymer?
A molecule containing >10 "mer" units
What is a monomer?
A molecule containing one "mer" unit
Free radical polymerization is a type of: _________ polymerization
Addition
Which of the following is NOT true about the molecular events during creep? (a) Grain boundaries sliding is an example of a molecular event during creep in metals. (b) Dislocation climb is when a dislocation moves one atomic spacing by diffusion of an entire row of vacancies to the extra partial plane of atoms in an edge dislocation. (c) Ceramics rarely exhibit creep but do so through grain boundary sliding. (d) Creep in polymers happens through viscous flow. (e) All are true.
All are true
Which is NOT a mechanism of creep? (a) Vacancies moving through the bulk of the grain (b) Vacancies move along grain boundaries (c) Amorphous regions becoming "frozen" (d) Dislocations climb (e) Grain boundary sliding
Amorphous regions becoming "frozen"
Which of the following sterilization processes utilizes high temperature to kill microorganisms? (a) Autoclave (b) Ethylene oxide (c) E-beam (d) Gamma radiation (e) None of the above
Autoclave
Which of the following is true regarding infrared spectroscopy (IR)? (a) Frequency dec. with inc. atomic weight (b) Frequency inc. with inc. atomic weight (c) Frequencies inc. with inc. bond energy (d) Both (a) and (c) (e) Both (b) and (c)
Both (a) and (c) Atomic weight ↑ = Frequencies ↓ Bond energy ↑ = Frequencies ↑
Which type(s) of bond involves NO electron sharing or transfer?
Both Van der Waals and Secondary Bonds
Stress concentrators are more significant in _______ materials (a) Brittle (b) Ductile
Brittle
What is a saturated polymer?
Carbon atoms in "mer" unit is bonded to 4 other atoms
What is a Schottky defect?
Cation vacancy + anion vacancy
What is a Frenkel defect?
Cation vacancy + cation interstitial
Ionic bonds are common in which material?
Ceramics
Which class of biomaterials is described by the following: brittle, can be easily sterilized, and low strength in tension and bending?
Ceramics
Polymer Conformation
Conformation refers to the structure of a molecule that can be changed by ROTATION around SINGLE BONDS - Functional side groups influence rotational flexibility
What type of bond is directional with variable bond energies?
Covalent
Polymers contain _________ bonds that are ________ (directional/non-directional)
Covalent, directional
Which of the following is NOT true about thermal transitions? (a) They can be determined using differential scanning calorimetry. (b) The glass transition temperature is found in materials that have an amorphous region. (c) Crystallization is an endothermic process. (d) Melting is an endothermic process. (e) c & d
Crystallization is an endothermic process
Time to rupture ______ with increasing temperature or stress during creep testing (a) increases (b) decreases
Decreases
Which of the following is NOT considered a type of chemical failure (a) Crazing (b) Degradation (c) Corrosion (d) Deformation (e) Calcification
Deformation
Random Copolymers
Distribution of repeating units is random ABBBAABABABBAB
Statistical Copolymers
Distribution of repeating units obeys laws of statistics
Which sterilization method uses gas and requires aeration after sterilization?
Ethylene Oxide
Polymer crystallization is: exothermic or endothermic?
Exothermic
What are Miller Indices used for?
Explaining and understanding the form of many microstructural features of many materials. The faces of single crystals form on certain lattice planes, typically with low indices
Which of the following relationships is true? (a) Simple Cubic Structure: 2 atom/unit cell and Coordination # = 6 (b) Simple Cubic Structure: 4 atom/unit cell and Coordination # = 4 (c) Simple Cubic Structure: 8 atom/unit cell and Coordination # = 2 (d) FCC Structure: 6 atom/unit cell and Coordination # = 8 (e) FCC Structure: 4 atom/unit cell and Coordination # = 12
FCC Structure: 4 atom/unit cell and Coordination # = 12
Which crystal structure has 4 atoms/unit cell?
Face-centered cubic (FCC)
True or false: Defects in ceramics are more common than in metals
False
True or false: Grain boundaries with lower degrees of misalignment have higher boundary energy
False
Crystalline polymer chain arrangement
Individual chains are organized into a regular structure - Extended chain - Planar zigzag
Amorphous polymer chain arrangement
Individual polymer chains are randomly tangled and have no long-range ordered arrangement
Charge neutrality must be maintained for defects in ______ solids
Ionic
Which class of primary bonds are common in ceramics?
Ionic
Ceramics contain _________ bonds that are_________ (directional/non-directional)
Ionic, non-directional
Tg is ______ for polymers with increased chain flexibility (large constituents) (a) lower (b) higher
Lower
Metals contain __________ bonds that are ______ (directional/non-directional)
Metallic, non-directional
Number Average Molecular Weight (Mn)
Mn treats all sizes of chains equally
Weight-Average Molecular Weight (Mw)
Mw places more emphasis on larger chains. Mw can more accurately correlate with mechanical and physical properties of the material
What type of higher order structure is ideal for drug delivery?
Networks
Which of the following is NOT true about planar defects? (a) It is a 2D defect. (b) All biomaterials have planar defects. (c) External surfaces are an example of a planar defect. (d) Tilt, twist, and twin boundaries are examples of planar defects. (e) None of the above
None of the above
Which of the following material characterization techniques can be used to determine the structure and location of protons in organic molecules? (a) XRD (b) Mass Spectrometry (c) NMR Spectroscopy (d) SEC (Size-Exclusion chromatography) (e) UV-Vis Spectroscopy
Nuclear magnetic resonance (NMR)
Solid-State Polymer Synthesis
Peptide synthesis
Grain boundary is a type of _____ defect
Planar
______ is the ratio describing the strain in the transverse direction to the applied force, and the strain in the axial direction of the force
Poisson's Ratio
Which class of biomaterial has the most flexible properties?
Polymers
Which would NOT improve the mechanical strength of a biomaterial? (a) Reduce movement of dislocation (b) Use additives to stabilize the dislocations (c) Rapid cooling (d) Add Fillers for crosslinking (e) Use smaller grains with more grain boundaries per volume
Rapid cooling
What are the steps of CONDENSATION polymerization?
Reaction: - No initiation - Elimination of small molecule (ex: H2O)
Block Copolymers
Repeat units are in long sequences • Two major types AAABBB (diblock) and AAABBBAAA (triblock)
Alternating Copolymers
Repeating units alternate ABABABABABABAB
Which is NOT true of edge dislocations? (a) Caused by crystal growth process (b) Burger's vector is perpendicular to the dislocation line (c) Caused by internal stresses from other defects (d) Interaction of resident dislocations during plastic deformation (e) Result of shear forces on part of the material
Result of shear forces on part of the material
Substitutional Point Defect in Alloys
Results in a substitutional solid solution = solute atom takes the place of solvent atoms
Interstitial Point Defect in Alloys
Results in an interstitial solid solution = solute atoms fill the space between the solvent atoms
Which of the following characterization methods relies on the size of the molecules? Also, what is the relationship between molecular size and retention time? (elute first or last?) (a) Mass Spectrometry, molecular size ↑ elute first (b) Mass Spectrometry, molecular size ↑ elute last (c) SEC, molecular size ↑ elute first (d) SEC, molecular size ↑ elute last (e) None of the above.
SEC, molecular size ↑ elute first
You have samples of the same dimension and decide to do a deflection test to find the stiffer material. Sample A deflects 20mm for a given load, and Sample B deflects 10mm. Which statement is true? (a) Sample A's Young's modulus is 2x Sample B's Young's modulus. (b) Sample A's Young's modulus is 0.5x Sample B's Young's modulus. (c) You cannot determine Young's modulus using the deflection test. (d) Sample A's shear modulus is 2x Sample B's shear modulus. (e) Sample A's shear modulus is 0.5x Sample B's shear modulus.
Sample A's Young's modulus is 0.5x Sample B's Young's modulus.
In ______________ dislocations, burger's vector is ____________________ to the line of dislocation. (a) Edge, parallel (b) Screw, perpendicular (c) Screw, parallel (d) a & c (e) b & c
Screw, parallel
Which of the following is NOT true about slip systems? (a) Deformability increases as the number of slip systems increases. (b) Slip systems exist both in crystalline and amorphous materials. (c) Slip systems are made up of the slip planes and the directions (axes) they can move. (d) Slip occurs along the plane with the highest atomic packing. (e) All are true
Slip systems exist both in crystalline and amorphous materials.
_____________ is a time-dependent property found in materials where a constant strain is applied and a change in stress over time is observed. (a) Stress relaxation (b) Strain relaxation (c) Creep (d) Fatigue (e) None of the above
Stress-relaxation
Which of the following describes the crystallinity temperature? (a) Temperature above which atomic movement is large enough to break material's ordered structure. (b) Temperature below which a material is considered a glass solid. (c) Temperature at which polymers with the ability to crystallize, do. (d) None of the above (e) b & c
Temperature at which polymers with the ability to crystallize, do.
What does this formula represent? (r cation)/(r anion)
The coordination number of an ionic crystalline solid. Used for ceramic crystal structures. The ratio of cation radius to anion radius determines the coordination number of the ionic crystal.
For BCC crystal structure, the close-packed directions are:
The cube diagonals
True or false: Brittle materials show little or no signs of deformation before failure
True
True or false: For polymers, a high strain rate can make the material appear brittle and have a higher strength?
True
True or false: Metals with lower slip system numbers are more brittle than those with higher slip system numbers
True
Which will result in higher stresses when graphed together? (a) Engineering Stress-Strain Curve (b) True Stress-Strain Curve (c) They will be the same
True Stress-Strain Curve
What are the requirements for CONDENSATION polymerization?
Two different types of bifunctional monomers, polyfunctional monomers, monomer with two functional groups
Which of the following is the maximum value of stress in a stress-strain curve?
Ultimate strength
The ______ is the basic repetitive unit for crystalline materials such as ceramics and metals
Unit cell
Vacancy Point Defect
Vacant atomic sites in a structure where there would normally be an atom
Which of the following is NOT a type of primary bond? (a) Covalent (b) Ionic (c) Metallic (d) Van der Waals (e) All are primary bonds
Van der Waals
Pores are a type of _____ defect
Volume
You have an unknown material and need to know the crystal structure. Which assay do you use?
X-ray Diffraction
Which of the following material characterization techniques can be used to determine Miller Indices? (a) XRD (b) Mass Spec (c) NMR (d) SEC (e) UV-Vis Spec
XRD
Which of the following is the slope of the Elastic Deformation region of a tensile stress/strain curve? (a) Young's Modulus (b) Shear Modulus (c) Yield Point Stress (d) Yield Point Strain (e) None of the above
Young's Modulus
Which of the following is NOT a type of polymer synthesis? (a) Substitution (b) Evaporation (c) Addition (d) b & c (e) a & b
a & b
Which of the following is NOT true about viscous flow/viscosity? (a) It can be modeled as a spring. (b) There is no linear relationship between shear stress and the rate of deformation. (c) It is how non-crystalline regions deform. (d) a & b (e) All are true.
a & b
In ______ dislocations, Burger's vector is ______ to the line of dislocation: (a) Edge, parallel (b) Edge, perpendicular (c) Screw, parallel (d) A and B (e) B and C
b & c
Which crystal structure has the best atomic packing factor (highest packing density) ? (a) SCC (b) BCC (c) FCC (d) HCP (e) c & d
c & d
