Overview of Ceramic Properties and Applications

Question 1

What are ceramics?

Answer 1

solid compounds that are formed by the application of heat, and sometimes heat and pressure

Question 2

What do ceramics comprise of at least? 4 things

Answer 2

1. one metal and nonmetallic elemental solid or a nonmetal
2. a combination at least of two nonmetallic elemental solids
3. a combination of at least 2 nonmetallic elemental solids and a nonmetal or metal

Question 3

is electrical movement harder or easier within an element than other material types

Answer 3

harder

Question 4

What is the second definition for what ceramics are? Examples?

Answer 4

Any of a large class of inorganics, nonmetallic products

High temps are used to fabricate.

composition and processing conditions can be varied considerably

including metallic oxides, borides, carbides, nitrides, sulfides, and mixtures or compounds

Question 5

What kinds of bonds are in ceramics?

Answer 5

ionic or covalent bonds, electrons are not free to move from atoms

Question 6

What are the three options for the arrangements of the atoms in solids?

Answer 6

1. long-range order - crystalline
2. short-range order - amorphous
3. mixture

Question 7

What is the def of ceramics involving grains?

Answer 7

ceramics are polycrystalline solids, composed of a collection of many single crystals (grains), which are separated from each other by areas of disorder (grain boundaries)

Question 8

What is a “microstructure”

Answer 8

The size and shape of the grains, together with the presence of porosity, second phases, etc. and their distribution

Question 9

What are a few features about glasses?

Answer 9

1. high disorder atom structure / amorphous
2. different properties
3. solidified upon cooling from melt
4. based on silica (SiO2)

Question 10

What are features of glass-ceramics?

Answer 10

1. combination of siliceous glass and oxide crystals in the same microstructure
2. long and short range order in same compound
3. different properties than glasses and ceramics

Question 11

CMP high temp stability

Answer 11

C - high
M - low/med
P- low

Question 12

What are 6 properties that ceramics have high that metals and polymers don’t?

Answer 12

1. temperature strength
2. elastic modulus
3. compressive strength
4. hardness
5. wear resistance
6. high temp stability

Question 13

List in order of low to heigh specificity or application (common tech and advanced ceramics)

Answer 13

common, technical, advanced

Question 14

What are the two largest ceramic industries?

Answer 14

glass and glass-ceramics

cements

Question 15

What are the 5 medium-sized ceramic industries?

Answer 15

1. structural clay products
2. technical
3. advanced
4. whitewares
5. refractories

Question 16

What are examples of common ceramics?

Answer 16

1. construction materials: concrete, blocks, brick, plasters, gypsum
2. clays, sand, feldspars

Question 17

What are some applications of common ceramics (not glass)? Types of ceramics they would use for them?

Answer 17

1. floor and wall tiles
2. containers
3. sanitary ware
4. construction materials

clays/sands/feldspars

Question 18

What are some applications of glasses and glass ceramics? Types of ceramics they would use for them?

Answer 18

1. porcelain enamels
2. bulbs and windows
3. stove tops and cook ware

soda-lime-silica glass/lithia-silicate glass/borosilicate glass

Question 19

What are two broad category applications of common ceramics?

Answer 19

1. refractories (furnace liners, filters for metal production)
2. abrasives (sandpaper, grinding and cut-off wheels)

Question 20

What are some technical ceramic applications?

Answer 20

Question 21

What are some advanced ceramics applications?

Answer 21

Question 22

List in order of low to heigh required reliability (common tech and advanced ceramics)

Answer 22

common, technical, advanced

Question 23

List in order of low to heigh unit cost (common tech and advanced ceramics)

Answer 23

common, tech, advanced

Question 24

List in order of low to heigh raw material particle size (common tech advanced)

Answer 24

advanced, technical, common

Question 25

List in order of low to height purity of raw materials (advanced tech common)

Answer 25

common, tech, advanced

Question 26

Specificity of application for common, tech, and advanced

Answer 26

common, tech, advanced

Question 27

what are the categories of differences between common, technical, and advanced ceramics

Answer 27

1. purity of raw materials 2. raw material particle size 3. unit cost 4. required reliability 5. specificity of application

Question 28

What kind of processing is ceramic processing?

Answer 28

powder processing

Question 29

Why is powder processing used for ceramics?

Answer 29

1. very high melting temp-- casing is not economical 2. ceramics are brittle-- large flaws reduce strength (casting produces large grains- flaws) 3. fine grain microstructures can be produced by sintering submicron particles

Question 30

what is the ceramic processing scheme?

Answer 30

powders ---- shaping (forming/ green body)--- sintering (densification/ dense body)

Question 31

Why is ceramic processing a powder processing?

Answer 31

1. very high melting temp so casting isn't economical 2. ceramics are brittle- large flaws reduce strength-- casting produces large grain flaws 3. fine grain microstructures can be produced by sintering submicron particles

Question 32

What do properties of ceramics depend on?

Answer 32

composition and structure

Question 33

what are 8 properties that we talk about in ceramics?

Answer 33

1. chemical intertness, 2. photonics/optical 3. electrical/dielectric 4. magnetic 5. thermal 6. mechanical 7. density 8. high temp stability

Question 34

What is the significance of the chemical inertness of ceramics?

Answer 34

1. good stability when it aqueous environments in neutral pH range 2. better performance than metals/polymers when exposed to combos of high/low pH and high/low temps and some mid chemical solutions (basically it takes a lot longer to corrode)

Question 35

what kind of property is corrosion

Answer 35

chemical inertness

Question 36

when can ceramics corrode? what is it dependent on?

Answer 36

- in extreme conditions - complex corrosion mechanisms - themodynamics and kinetics of corrosion are very dependent on composition and structure

Question 37

what are four examples of applications where ceramics can be used because of their chemical inertness?

Answer 37

1. containment of nuclear waste using borosilicate glass 2. TiB2 for aluminum smelting cathodes 3. bioglass to repair bones 4. ceramic implants (ZrO2 and TiO2)

Question 38

what is an optical property defined by

Answer 38

how a material interacts with light

Question 39

what is photonics

Answer 39

photonics is a broad category that includes any phenomena and devices that deal with the generation, manipulation, and sensing of light

Question 40

what are the 5 parameters of optical properties

Answer 40

1. absorption 2. refraction 3. transmission 4. reflection 5. scattering

Question 41

what are 4 different categories of optical property behavior in ceramics?

Answer 41

1. translucency, transparency, and opacity 2. glass 3. birefringence 4. color

Question 42

What are 4 different examples of optical applications of materials

Answer 42

1. fiber optics 2. LASERs 3. photochromics (glass, silver halides, pigments) 4. transparent ceramic armor

Question 43

What are electric/dielectric properties controlled by

Answer 43

1. long range transport (conductivity) of mobile carriers (electrons, ions, etc.) 2. short range movement of electrical dipoles (polarization) in specific domains

Question 44

What are some examples of ceramics being used for their electric/dielectric properties?

Answer 44

capacitors, insulators, electronic packaging, batteries

Question 45

What are three different properties we study relating to the thermal properties of ceramics?

Answer 45

1. thermal conductivity 2. thermal expansion 3. thermal shock resistance (TSR)

Question 46

What is thermal conductivity

Answer 46

ability of a material to conduct heat (W/m-K)

Question 47

are most ceramics good or poor thermal conductors

Answer 47

poor

Question 48

What are three examples of ceramics with high thermal conductivity

Answer 48

AIN, TiB2, ZrB2

Question 49

what is the symbol for thermal conductivity

Answer 49

k

Question 50

what happens when you add porosity to a ceramic

Answer 50

lowers the thermal conductivity (k) of ceramics

Question 51

What is thermal expansion

Answer 51

the ability of a ceramic to expand/contact during heating and cooling

Question 52

do ceramics exhibit lower or higher thermal expansion than metals

Answer 52

lower

Question 53

what ceramic has the lowest expansion coefficient

Answer 53

SiO2

Question 54

what is thermal shock resistance

Answer 54

TSR, the ability of the ceramic to resist fracture when cooled/heated

Question 55

what does high TSR relate to

Answer 55

high TSR = high k + low thermal expansion

Question 56

what are 4 examples of ceramics where their thermal properties are used

Answer 56

1. Si3N4 rotors 2. leading edges (aircraft) 3. shuttle tiles 4. SiO2 aerogel

Question 57

what are three different properties that you look at when evaluating the mechanical properties of materials

Answer 57

1. strength 2. fracture toughnes 3. hardness

Question 58

what are the symbols for strength, fracture toughness, and hardness

Answer 58

Strength σƒ fracture toughness K IC Hardness Hv

Question 59

what is strength and what is it measured in

Answer 59

resistance to fracture (MPa)

Question 60

how do you test for strength

Answer 60

4-point bend test

Question 61

what is the general strength of ceramics

Answer 61

ceramics have theoretical strengths higher than most other material but have a wider variation in values because of flaws

Question 62

what is fracture toughenss

Answer 62

resistance to crack propogation (MPa-m^1/2)

Question 63

how do you test for fracture toughness

Answer 63

single edge notched beam (SENB) or Vickers indentation

Question 64

do ceramics have a high or low fracture toughness and why?

Answer 64

low because they can't plastically deform

Question 65

what can improve ceramic fracture toughness

Answer 65

microstructural design and reinforcement

Question 66

what is hardness and what is the unit

Answer 66

resistance to indentation (Kg/mm^2)

Question 67

how do you test for hardness

Answer 67

diamond pyramic method (Vickers)

Question 68

do ceramics generally have high or low hardness? why?

Answer 68

high hardness due to their ionic/covalent bonding than other mateirals

Question 69

what are three different applications that take advantage of the mechanical properties of ceramics?

Answer 69

1. protective armor 2. ceramic implants 3. engines

Question 70

What are the significant properties where ceramics outperform other materials?

Answer 70

1. high temperature stability 2. elastic modulus 3. compressive strength 4. chemical inertness 5. thermal coeff. expans. coeff