EGRB 427 Biomaterials test 1 study set

Which type of degradation includes water flowing in faster than rate of polymer hydrolysis?

Bulk (no change in size, reduce mechanical properties)

What is the CN, # of atoms, and APF of face centered cubic?

CN = 12, atoms = 4, APF = 0.74

What is the CN, # of atoms, and APF of simple cubic?

CN = 6, atoms = 1, APF = 0.52

What is the CN, # of atoms, and APF of body centered cubic?

CN = 8, atoms = 2, APF = 0.68

Which material must maintain electroneutrality?

Ceramics

What are the factors affecting Tg?

Chain flexibility, Chemical constituents, crosslinking, increased MW

What is isomerism?

Compounds that have the same molecular formula but different structural formula. cis and trans cis is more flexible, trans more crystalline

What is crevice corrosion?

Corrosion driven by repetitive breakdown and re-passivation. Low pH and lack of oxygen.

What are the 3 stages of fatigue?

Crack initiation, Crack propagation, final failure

A smaller R group means the material is more crystalline or amorphous?

Crystalline

What are the 5 chemical determinants of polymers?

Crystallinity, Side group (R) type and size, R configuration, chain structure, and molecular weight

What are spherulites?

Crystals radiating from a nucleus with amorphous material in between (rubber)

What is creep?

Deformation over time under constant pressure

What is a regenerative material?

Degrades and replaces in a way that stimulates cell response

What are the factors affecting Tm?

Degree of branching and MW

Which characterization technique works for identifying percent crystallinity of polymer?

Differential Scanning Calorimetry

Where is burger's vector in edge, screw, and mixed dislocation?

Edge - magnitude and direction of dislocation is perpendicular to dislocation line screw - parallel mixed - changes as you move through material

Which characterization technique works for identifying the composition and structure of polymer?

FTIR

How do brittle fractures happen in relation to grain boundaries?

Fractures go through or along grain boundaries

What are the 2 types of defects in ceramics?

Frenkel and Schottky defects

Which characterization technique works for identifying PI of polymer sample?

Gel Permeation Chromatography

For copolymers chain structure, order crystallinity from most to least

Graft, block, alternating, random

What is precipitation hardening?

Heat treatment to strengthen material (includes quenching for rapid cooldown)

What are the 2 steps for initiating oxidation?

Homolysis and heterolysis

What are the 2 secondary bonds?

Hydrogen, van der waal

What are the 3 steps to create a polymer?

Initiation (add free radical) propagation (repetition) termination

What are the 3 classes of biomaterials?

Inorganic materials, inorganic ceramics, and organic polymers

What are the 3 primary bonds?

Ionic, covalent, metallic

What are the 3 types of tacticity?

Isotactic (all R groups on one side) syndiotactic (alternating R group placement) atactic (no pattern)

What conditions are favorable for hydrolysis?

*carbon double bond to oxygen* higher cleavable bonds, hydrophilic material, higher MW lower crystallinity, lower cross linking

What is a bioactive material?

a material with a bong between it and the host

What are point defects?

1-2 atoms that are either vacant or self-interstitial which result in local lattice strain

What are the 4 steps to determining the miller index?

1. Determine intercepts ( if parallel, intercept is infinity) (1,inf,inf) 2. take reciprocal (1,0,0) 3. multiply to clear fractions (1,0,0) 4. record in parenthesis with no commas (1 0 0)

What is galvanic corrosion?

2 similar metals coupled in body that cause corrosion via redox reaction.

What are linear defects?

5 to 100M one dimensional defect of atom misalignment that results in large mechanical deformation in crystalline solid

What is passivation?

A layer of oxides formed on the surface of a metal that provides corrosion protection.

What is a bioinert material?

A material with no toxic response or scar tissue formation

What is crazing?

A network of fine cracks. Can't be felt on the surface, can continue to support load.

What is alloying?

Adding metals to reduce lattice strain, which makes it harder for dislocation glide to occur

What are the 2 types of polymerization?

Addition polymerization and condensation (aka step growth) polymerization

What are the methods to add defects in metals?

Alloying strain hardening (cold work) grain size refinement (annealing) precipitation hardening (volume defects)

What are the 4 different chain structures?

Linear, branched, cross-linked, network

For the least amount of variation, should the Polydispersity index (Mw/Mn) be high or low

Low (as close to 1 as possible)

What is annealing?

Manipulation of Microstructure to recover ductility lost from strain hardening by heating up material.

What is the molecular cause of creep in polymers?

Movement of chains in amorphous region via viscous flow, relative to Tg

Which characterization technique works for identifying structure by relative H atoms

Nuclear Magnetic Resonance spectroscopy

How do you predict corrosion?

Pourbaix diagram

For volume defects, what is the difference between precipitate and void defects?

Precipitate are a cluster of impurities while void is an aggregate of vacancies

What are the 3 stages of creep?

Primary - repositioning of dislocations secondary - creep slows tertiary - formation of gross defects (leads to failure)

What kind of bonds are polymers?

Primary bonds / covalent bonds

What kind of bonds are ceramics?

Primary bonds / ionic bonds

What is pitting corrosion?

Processing that leads to small flaws where passivation film is disrupted

Are sigma or pi bonds stronger?

Sigma

What are the 3 crystal unit cells?

Simple cubic, body centered cubic, face centered cubic

What is the difference between spectroscopy and chromatography?

Spectrography is how different components absorb different types of energy. Chromatography is physically separating molecules based on chemical properties.

What type of degradation includes water flowing in slower than hydrolysis?

Surface ( hydrophobic, maintains chemical properties but shrinks)

What are the 2 primary mechanisms of polymer degradation?

Swelling/Dissolution and chain scission

What is a mer?

The basic repetitive unit of a polymer structure

Which characterization technique works for identifying the concentration of a component in a meterial

UV-vis spectrography

Is a chain structure with double and triple bonds saturated or unsaturated?

Unsaturated

What is hydrlysis?

Water driven cleavage of bonds.

Which characterization technique works for identifying atomic crystal structure?

X-ray diffraction (XRD)

What is a bioresorbable material?

a material that degrades in the body, dissolutes, and is secreted

What type of copolymers have the highest probability of crystallization?

alternating and block. Graft is inclined to hinder secondary interactions and now allow for ordered packing

What is the second quantum number and what does it mean?

angular momentum (l) is the shape orbital. l=n-1. 0=s 1=p 2=d 3=f

Why do we create pores? What are some disadvantages to this?

cell proliferation, new tissue growth, tissue vascularization. Some disadvantages are mechanics, biodegradability, and corrosion

What are the different types of linear defects?

edge, screw, and mix dislocations

For metallic bonds, more mobile electrons around the core cation means more what?

electrical conductivity

Why can failure occur at stress below yield strength

fatigue failure (90% of failure in metals)

What is Tc?

temperature where polymers with the ability to crystallize will do so. Used as processing parameter

What is Tg?

glass transition temperature

What is the molecular cause of creep in metals and ceramics?

grain boundary movement

What affects the rate of polymer degradation?

hydrolysis and enzymatic degradation

Describe the relationship between stress relaxation with crystallinity and Tg

inc. crystallinity = dec. SR If temp is less than Tg, no SR If temp is more than Tg, SR happens

What do double and triple covalent bonds do to the material?

increase rigidity

What is strain hardening / cold work?

increasing number of line defects, carried out at low temp relative to Tm. Improves strength, decreases ductility

For solutes, what is the difference between interstitial and substitutional solution.

interstitial fill the space between atoms. substitutional take the place of a solvent atom. They typically cause less than 15% difference in atomic radii.

For 2D planar defects, having a small angle grain boundary means what?

larger grains, increased stability, decreased energy

What is the third quantum number and what does it mean?

magnetic quantum number (ml) is the orientation of the orbital. l=0: m=0. l=1: m=-1,0,1. l=2: m=-2,-1,0,1-2. l=3: m=-3,-2,-1,0,1,2,3

How do you indicate negative values in miller indices?

negative bar over the number

what is a coordination number?

number of nearest atomic neighbors

What is solid state diffusion?

point defects are not fixed in place, so higher temperature means more diffusion. This results in movement of atoms through a solid to form a new mineral

What are elastomers?

polymers that are fluid at room temperature and turn into solid via polymerization processes with cross linking return to coiled state because it is more thermodynamically favorable

What is the first quantum number and what does it mean?

principal quantum number (n) is the distance from the center of the nucleus

What does the stability of ceramics depend on?

radius of cations / radius of anions (rc/ra). Higher = more stable. MUST MAINTAIN ELECTRONEUTRALITY

What is intergranular corrosion?

remove grain boundary Material from a metal.

What happens at Tm?

secondary bonds break

What are the determinants of crystallinity?

side groups, tacticity, degree of branching, and regularity in mer placement

If you want a more crystalline structure, what kind of R group do you want?

small R group because it allows the chains to pack more closely together.

For 2D planar defects, having a large angle grain boundary means what?

small grains, decreased stability, increased energy, surface tension

What is the fourth quantum number and what does it mean.

spin (ms) which direction electron is spinning (2,6,10,14)

What is the formula for atomic packing factor?

volume of atoms / size of atom

What is a lamella?

weight-bearing, column-like matrix tubes composed mainly of collagen. Basic unit of crystalline structure