Metals Overview 1

Question 1

The technical materials used to build most structures are divided into four classes:

Answer 1

• Metals
• Ceramics (including glasses)
• Composites
• Polymers

Question 2

Biomaterials and biomedical devices are used throughout the human body.

2 Important aspects:

Answer 2

• Functional performance

- Biocompatibility

Question 3

The material must satisfy it’s design requirements in service:

Answer 3

• Load transmission and stress distribution (e.g. bone replacement)
• Articulation to allow movement (e.g. artificial knee join)
• Electrical stimuli (e.g. pacemaker)
• Light transmission (e.g. implanted lenses)
• Sound transmission (e.g. cochlear implant)

Question 4

The biomaterials/devices must not ______ in it’s properties within the body( unless this is wanted)

The biomaterials/devices (and any degradation product) must not cause any ________ reaction within the host’s body.

Answer 4

• degrade

- adverse

Question 5

Properties of Metals (8)

Answer 5

• Lust (shininess)
• Good conductors of heat and electricity
• High density (heavy for their size)
• High melting point
• Ductile (most metals can be drawn out into thin wires)
• Malleable (most metals can be hammered into thin sheets)
• Easily lose electrons
• Surface reactive

Question 6

Metals are widely used as biomaterials due to their

___________ and __________

Answer 6

Strength and thoughness

Question 7

-
-

Answer 7

• Stainless steel
• Titanium
• Cobalt alloys

Question 8

Some people are allergic to ions released from these metals.
Major Problem:
-Generation of sine wear particles in service can lead to :
-
-

Answer 8

• Inflammation and

- Implant loosening

Question 9

Applications (4)

Answer 9

• Bone and joint replacement
• Dental Implants
• Cardiovascular devices
• Surgical instruments

Question 10

Electronegativity

Answer 10

• Ranges from 0.7 to 4.0
• Large values: tendency to acquire electrons

~Important because of bonding and reactions

Question 11

Atomic Bonding: Ionic Boding

• Occurs between + and - ions
• Requires _______ transfers
• Large difference in _______required
• Ex. _____
• Predominant bonding in _________

Answer 11

• electron
• electronegativity
• Ex. NaCl
• Ceramics

Question 12

Covalent Bonding

• Similar _______ - Share electrons
• Bonds determined by ______ - s & p orbitals dominate bonding
• Ex. _______

Answer 12

• electronegativity
• valence
• Ex. CH4

Question 13

Secondary Bonding

• Arises form interaction between ______
  - Fluctuating dipoles
  - Permanent dipoles-molecules induced

Answer 13

-dipoles

Question 14

Type Bond Energy Comments
Ionic Large! Non-directional (______)
_______ Variable Directional
(semiconductors, ceramics
polymer chains)
Metallic Variable Non-directional (_____)
Secondary _______ Directional
inter-chain (polymer)
inter-molecular

Answer 14

Type Bond Energy Comments
Ionic Large! Non-directional (ceramics)
Covalent Variable Directional
(semiconductors, ceramics
polymer chains)
Metallic Variable Non-directional (metals)
Secondary Smallest Directional
inter-chain (polymer)
inter-molecular

Question 15

Densities of material classes

p_____ > p______ > p_______

Answer 15

p metals > p ceramics > p polymers

Question 16

Metals have:

• _______-packing (metallic bonding)
• often ______ atomic masses

Answer 16

• close-packing

- large

Question 17

Ceramics have:

• _____ dense packing
• often ______ elements

Answer 17

• Less

- lighter

Question 18

Polymers have:

• ____ packing density ( often _______)
• _______ elements

Answer 18

• Low
• amorphous
• Lighter

Question 19

Composites have

-________ values

Answer 19

-Intermediate

Question 20

Metals: Energy and Packing

• Non dense , ______ packing
• Dense, _______ packing
  
  • Tend to have _______ energies

~Lower energy state = more stable

Answer 20

• random
• ordered
• lower

Question 21

Materials and Packing
Crystalline materials
   - Atoms pack in periodic, \_\_\_\_ arrays
   - Typical of:
          - 
          - 
          -

Answer 21

• 3D arrays
  
  • Metals
  • Many ceramics
  • Some polymers

Question 22

Materials and Packing
Non-crystalline materials
   - Atoms pack \_\_\_\_ periodic packing
   - Occurs for:
          - 
          -

Answer 22

• no periodic
  
  • Complex structures
  • Rapid cooling

Question 23

Materials and Packing

__________ = Non-crystalline

Answer 23

-Amorphous

Question 24

Crystalline solids composed of elemental ________ positively charged ions in a cloud of electrons

Answer 24

-positively

Question 25

Unit cell:

Answer 25

Smallest repetitive volume which contains the complete lattice pattern of a crystal

Question 26

Micorstructure of Metals - Basic atomic architecture is a _________ structures - Different elements have different crystalline architectures and can combine with ______ partners

Answer 26

- crystal | - different

Question 27

Metallic Crystal Structures - Tend to be ______ packed - Reasons for dense packing - Typically, only _____ element is present, so all atomic _______ are the same. - Metallic bonding is not _________. - Nearest neighbor distances tend to be small in order to ______ bond energy. - Electron cloud shields cores from each other

Answer 27

- densely - one - radii - directional - lower

Question 28

Simple Cubic Structure (SC) - ______ due to low packing density (only Po has this structure) - _____-________ directions are cube edges - Coordination # = ______

Answer 28

- Rare - Closed-packed - 6

Question 29

Body Centered Cubic Structure (BCC) - Atoms touch each other along ______ diagonals - Coordination # = _____

Answer 29

- cube | - 8

Question 30

Face Centered Cubic Structure (FCC) - Atoms touch each other along ______ diagonals - ABCABC.....stacking sequence - ____ projection

Answer 30

- face | - 2D

Question 31

X-rays to Determine Crystal Structure - Incoming X-rays _______ from crystal planes - Measurement of critical angle, 0c, allows computation of planar spacing, d.

Answer 31

-diffract

Question 32

X-Ray Diffraction Pattern - Rectangle - Square - Triangle

Answer 32

- (110) - (200) - (211)

Question 33

Formation of Grain Structure -_________-result of casting of molten material - 2 Steps - - -Start with a molten material - all liquid -Crystal grow until they meet each other

Answer 33

- Solidification - Nuclei form - Nuclei grow to form crystals - grain structure

Question 34

Crystal Defects - _______ crystals are not perfect - Sometimes there are empty spaces called _______, where an _____ is missing - These and other __________, as well as the existence of grains and grain boundaries determine many of the _________ properties - When a _____ is applied to a metal, _________ are generated allowing the metal to deform

Answer 34

- Metallic - vacancies - atom - imperfections - mechanical - stress - dislocations

Question 35

``` Types of Imperfections -Point Defects - - - -Line Defects - - Area Defects - ```

Answer 35

- Point Defects - Vacancy atoms - Interstitial atoms - Substiutional atoms - Line Defects - Dislocations - Area Defects - Grain Boundaries

Question 36

Vacancies: - Vacant ______ sites in a structure - Distortion of ______

Answer 36

- atomic | - planes

Question 37

Self-Interstitials: - "_____" atoms positioned between atomic sites - Distortion of ______

Answer 37

- extra | - planes

Question 38

Dislocations: - Are ______ defects - ______ between crystal planes result when ________ move, - Produce permanent (______) deformation

Answer 38

- line - Slip - dislocations - plastic

Question 39

Polycrystalline Materials - Interfacial Defects: Grain Boundaries - _______ between crystals - Transition from ______ of one region to that of the other - Slightly _______ - ____ density in grain boundaries - High mobility - High diffusivity - High chemical reactivity

Answer 39

- Regions - lattice - disordered - Low