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Question 1

(T/F) When hardening metals, the grain size hardening increases with the grain size because the barrier for any dislocations becomes more robust

Answer 1

False. Smaller grain size –> more barriers for dislocations

Question 2

(T/F) One main disadvantage with titanium for bio-implant use, is their proneness to fatigue failure

Answer 2

False. Cobalt-chromium is prone to fatigue, Titanium has poor friction properties

Question 3

Poly(ethelene terephthalate) is less susceptible to hydrolysis than poly(tetrafluoroethylene) because of the chemical moieties along the backbone (i.e ester groups)

Answer 3

False.

Question 4

In ceramics, with decreased temperature, the surface to mass ratio decreases

Answer 4

False.

Question 5

Poly(methyl methacryalate) (PMMA) is a thermoplastic.

Answer 5

True.

Question 6

Generally, ceramics have a very high Young’s modulus as well as hardness and, exhibit a high melting point and density.

Answer 6

False. The atoms are small so they have a low density.

Question 7

Hydroxyapatite is an example of a bioactive ceramic that specifically is used for heavy load bone implants

Answer 7

False.

Question 8

PGA is considered a crystalline polymer.

Answer 8

True. Crystalline polymers have regions of regular and neat packing, like crystals.

Question 9

Mixing the two isotactic PLLA and PDLA, decreases the tensile strength over time compared to PLLA and PDLA alone.

Answer 9

False.

Question 10

When a material is deformed, all bonds break simultaneously

Answer 10

False.

Question 11

Metals are brittle

Answer 11

False. Metals are tough and have high tensile strength.

Question 12

Silicon in the fcc structure has directional bonds

Answer 12

False. FCC comes from non directional bonding.

Question 13

Body-centered cubic crystal structure shows a higher packing density than the hexagonal close-packed crystal structure.

Answer 13

False. Close-packed=high density

Question 14

The diamond structure is typical for directional bonds.

Answer 14

True.

Question 15

Generally, ionic bonds are displaying a higher heat of vaporization than metallic bonds.

Answer 15

True. More energy is required to break the bonds.

Question 16

The green body formation is a step in the ceramic fabrication process.

Answer 16

True. It is when the powder is compacted/shaped

Question 17

With decreased temperature, the surface to mass ratio in ceramics increases.

Answer 17

True. Grains are packed more tightly in higher temperatures

Question 18

Hydroxyapatite is a resorbable ceramic type

Answer 18

False.

Question 19

The permeability of a hydrogel increases with increased swelling of the gel.

Answer 19

True.

Question 20

Hydrogels are commonly used for loading of hydrophobic drug substances

Answer 20

False. Hydrogels have a poor loading capacity

Question 21

Stress shielding is a positive characteristic referring to how well a material withstands chemical degradation.

Answer 21

False. Stress shielding is when bone around an implant gets weaker due to an implant taking on the pressure and stress the bone normally has.

Question 22

Ceramics have a good high temperature stability

Answer 22

True.

Question 23

Metals are brittle

Answer 23

False.

Question 24

Metallic bonding is directional

Answer 24

False. Electrons can be found in any direction from a given atom

Question 25

The ionic bonds in MgO have a lower heat of vaporization than the covalent bonds present in a diamond.

Answer 25

False. Ionic bonds are stronger than covalent bonds

Question 26

The bonding orbital in sigma bonds show rotational symmetry

Answer 26

True. They are just balls

Question 27

Silicon in the FCC structure is a semi-conductor

Answer 27

False.

Question 28

Metals can form the HCP structure

Answer 28

True. They are close-packed structures and a result of non-directional (i.e metallic) bonding

Question 29

Diamond structure is a more densly packed structure than BCC

Answer 29

False. Diamond structure is 34% while BCC is 68%

Question 30

A rubbery-like polymer (elastomers) is weak, but highly extensible

Answer 30

True. Low youngs modulus but high failure strain.

Question 31

In an isotactic polymer, the R group is randomly located in or behind the polymer backbone.

Answer 31

False. In an isotactic polymer all R groups are on one specific side

Question 32

An elastomere has high flexibility and low crystallinity

Answer 32

True. Crystallinity prevents stretching

Question 33

Elastomers are usually thermoplasts

Answer 33

False. They are usually thermosets

Question 34

The two most common synthesis methods for polymers are condensation and hydrolysis

Answer 34

False

Question 35

One characterization method that determines Tg and Tm is differential scanning microscopy

Answer 35

False. Its called differential scanning calorimetry. Another method is “dynamic mechanical analysis”

Question 36

The chemical compostition of polymers is usually determined via Auger electron spectroscopy

Answer 36

False. NMR or IR that is used for bulk and XPS/ESCA is used for surface.

Question 37

The “PDI” describes the degree of polymerization of a specific polymer

Answer 37

False. Its depicted as “DP”

Question 38

One main degradation rate determinant of polymers is susceptibility of the polymer backbone to hydrolytic cleavage. (L17)

Answer 38

True. Polymers that undergo hydrolytic cleavage are preferred as medical implants due to predictable degradation, compared to enzymatically degradable implants.

Question 39

PGA erodes faster than the PLA but a 50:50 mixture of the two degrades the fastests

Answer 39

True.

Question 40

Degradation rate increases with high surface area to volume ratio

Answer 40

True.

Question 41

Degradation rate decreases with compactness of the material

Answer 41

True.