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Biomaterials > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

What are the three classes of materials?

A

Ceramics, metals, and polymers

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2
Q

Describe a crystalline structure.

A

Atoms vibrate in place in a fixed pattern (organized hexagonal pattern)

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3
Q

Describe the structure of an amorphous material.

A

Atoms vibrate in place in more random arrangements

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4
Q

What are the three states of solid material?

A

Crystalline, polycrystalline, and amorphous

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5
Q

What is a unit cell in a crystal structure?

A

a smaller section that is repeated on a crystal

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6
Q

What is the coordination number of a crystal structure.

A

number of nearest-neighbor atoms

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7
Q

What is the formula for atomic packing factor?

A

𝐴𝑃𝐹 = volume of atoms in unit cell / total unit cell volume

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8
Q

What are the three crystal structures for common metals?

A

Face-centered cubic (FCC), Body-centered cubic (BCC), Hexagonal Closed Packed (HCP)

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9
Q

Which crystal structure has the highest APF?

A
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10
Q

Which crystal structure has the highest coordination number?

A
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11
Q

How does APF impact a structure?

A

denser packed atoms (better strength and hardness), increase stability, increased thermal and electrical conductivity

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12
Q

How does coordination number impact a structure?

A

higher number means stronger bonding (better strength and durability), determines its coordination number, and phase behavior

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13
Q

What are the two types of metal formation?

A

Single crystal and polycrystalline

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14
Q

How are single-crystal metals formed?

A

by carefully controlled processes that allow only one crystal orientation to dominate. This process requires strict control over temperature and cooling rates to prevent additional crystals from forming.

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15
Q

How are polycrystalline metals formed?

A

metal cools, tiny crystals start to form and grow in random orientations. These crystals eventually meet and form grain boundaries where they connect

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16
Q

Which may be faster to produce: single-crystal or polycrystal materials?

A

polycrystal materials

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17
Q

How long does single-crystal materials take to form and why?

A

single-crystal metals take longer to produce due to the complex methods needed to avoid multiple crystal formations. Processes are slow, as any misstep can lead to additional crystals, which compromises the single-crystal structure.

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18
Q

How long do polycrystal materials take to form and why?

A

Much faster to produce because they involve conventional casting or cooling methods where crystals naturally form as the metal solidifies.

19
Q

Which is cheaper, polycrystal materials or single-crystal materials?

A

Polycrystalline metals are significantly cheaper due to faster production and less stringent requirements for environmental control during the cooling process.

20
Q

What are the different point defects in crystal structures?

A

Vacancy and Self-interstitial

21
Q

What is a self-interstitial defect in a crystal structure?

A

When a molecule of the same type inserts itself in between other molecules disrupting the pattern
* * * *
*
* * * *

22
Q

What are the different types of impurities in a crystal structure?

A

Interstitial impurity atoms and Substitutional impurity atoms

23
Q

What is an interstitial impurity atom?

A

An atom of a different molecule squeezes in between the atoms of the structure (the overall structure keeps its form)
* * * *
* * * + *
* * * *
* * * *

24
Q

What is a substitutional impurity atom?

A

An atom of the same molecule takes the place of one of the atoms and does not disrupt the structures form
* * * *
* + * *
* * * *
* * * *

25
Q

How does diffusion work when there is a vacancy in a crystal structure?

A

an atom jumps to an adjacent vacancy, thereby exchanging the location of the atom and the vacancy

26
Q

How does diffusion work when there is an impurity in a crystal structure?

A

an atom migrates from one interstitial position to a neighboring position. This usually occurs only with small atoms that can easily fit into the interstitial spaces

27
Q

Describe the characteristics of a metal.

A

They have high electrical and thermal conductivity as well as
malleability, ductility, high wear resistance, and high reflectivity of light

28
Q

What are common uses for metals?

A

– Orthopedic reconstruction
– Fracture fixation
– Oral/maxillofacial reconstruction
– Cardiovascular interventions
– Conductive Electrodes / Cables

29
Q

What is a metal-alloy?

A

Mixture of two or more elements
(at least one is a metal)

30
Q

What are common metals used for biomedical applications?

A
  • Stainless steel
  • Cobalt Chromium based alloys
  • Titanium-based alloys
31
Q

What is stainless steel made of?

A

An alloy of Iron (Fe) and Carbon

32
Q

Why was stainless steel developed?

A

Developed to decrease rust (introduces passive film)

33
Q

Describe the characteristics of Titanium.

A

light weight, low density
Good corrosion resistance
Increase in Oxygen in in grades increases yield strength

34
Q

What is a ceramic?

A

An inorganic, non-metallic material that consists of two or more metallic and non-metallic elements

35
Q

What are ceramics made of?

A

Comprised largely of ionic bonds, some covalent, amorphous (glass) or
crystalline (porcelain)

36
Q

What are the classifications of ceramics?

A

– Form (powder, coating, bulk)
– Composition
– Reactivity (inert, degradable, surface reactive)

37
Q

What properties do ceramics have?

A

– High strength (in certain directions)
– Brittle (not ductile)
– Resistant to chemicals and heat (good insulators)

38
Q

Which one is bigger, cations or anions? Why?

A

The addition of electrons increases electron-electron repulsion within the atom, causing the electrons to spread out further from the nucleus. This results in a larger atomic radius

39
Q

____ materials are not strictly considered metals, ceramic or polymer.

A

Pure C

40
Q

What types of material is graphite considered and why?

A

It is considered a ceramic because it has planes of hexagonally arranged carbon

41
Q

What is pyrolytic carbon used for?

A

Used in artificial heart valves due to high strength, wear resistance, fatigue resistance

42
Q

What is calcium phosphate used for?

A

Good for bone ingrowth, but can be brittle

43
Q

What is the building block of glass?

A

SiO2

44
Q
A

Biomaterials (11 decks)

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