Overview of Ceramic Properties and Applications Flashcards
What are ceramics?
solid compounds that are formed by the application of heat, and sometimes heat and pressure
What do ceramics comprise of at least? 4 things
- one metal and nonmetallic elemental solid or a nonmetal
- a combination at least of two nonmetallic elemental solids
- a combination of at least 2 nonmetallic elemental solids and a nonmetal or metal
is electrical movement harder or easier within an element than other material types
harder
What is the second definition for what ceramics are? Examples?
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
What kinds of bonds are in ceramics?
ionic or covalent bonds, electrons are not free to move from atoms
What are the three options for the arrangements of the atoms in solids?
- long-range order - crystalline
- short-range order - amorphous
- mixture
What is the def of ceramics involving grains?
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)
What is a “microstructure”
The size and shape of the grains, together with the presence of porosity, second phases, etc. and their distribution
What are a few features about glasses?
- high disorder atom structure / amorphous
- different properties
- solidified upon cooling from melt
- based on silica (SiO2)
What are features of glass-ceramics?
- combination of siliceous glass and oxide crystals in the same microstructure
- long and short range order in same compound
- different properties than glasses and ceramics
CMP high temp stability
C - high
M - low/med
P- low
What are 6 properties that ceramics have high that metals and polymers don’t?
- temperature strength
- elastic modulus
- compressive strength
- hardness
- wear resistance
- high temp stability
List in order of low to heigh specificity or application (common tech and advanced ceramics)
common, technical, advanced
What are the two largest ceramic industries?
glass and glass-ceramics
cements
What are the 5 medium-sized ceramic industries?
- structural clay products
- technical
- advanced
- whitewares
- refractories
What are examples of common ceramics?
- construction materials: concrete, blocks, brick, plasters, gypsum
- clays, sand, feldspars
What are some applications of common ceramics (not glass)? Types of ceramics they would use for them?
- floor and wall tiles
- containers
- sanitary ware
- construction materials
clays/sands/feldspars
What are some applications of glasses and glass ceramics? Types of ceramics they would use for them?
- porcelain enamels
- bulbs and windows
- stove tops and cook ware
soda-lime-silica glass/lithia-silicate glass/borosilicate glass
What are two broad category applications of common ceramics?
- refractories (furnace liners, filters for metal production)
- abrasives (sandpaper, grinding and cut-off wheels)
What are some technical ceramic applications?
What are some advanced ceramics applications?
List in order of low to heigh required reliability (common tech and advanced ceramics)
common, technical, advanced
List in order of low to heigh unit cost (common tech and advanced ceramics)
common, tech, advanced
List in order of low to heigh raw material particle size (common tech advanced)
advanced, technical, common
List in order of low to height purity of raw materials (advanced tech common)
common, tech, advanced
Specificity of application for common, tech, and advanced
common, tech, advanced
what are the categories of differences between common, technical, and advanced ceramics
- purity of raw materials
- raw material particle size
- unit cost
- required reliability
- specificity of application
What kind of processing is ceramic processing?
powder processing
Why is powder processing used for ceramics?
- very high melting temp– casing is not economical
- ceramics are brittle– large flaws reduce strength (casting produces large grains- flaws)
- fine grain microstructures can be produced by sintering submicron particles
what is the ceramic processing scheme?
powders —- shaping (forming/ green body)— sintering (densification/ dense body)
Why is ceramic processing a powder processing?
- very high melting temp so casting isn’t economical
- ceramics are brittle- large flaws reduce strength– casting produces large grain flaws
- fine grain microstructures can be produced by sintering submicron particles
What do properties of ceramics depend on?
composition and structure
what are 8 properties that we talk about in ceramics?
- chemical intertness,
- photonics/optical
- electrical/dielectric
- magnetic
- thermal
- mechanical
- density
- high temp stability
What is the significance of the chemical inertness of ceramics?
- good stability when it aqueous environments in neutral pH range
- 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)
what kind of property is corrosion
chemical inertness
when can ceramics corrode? what is it dependent on?
- in extreme conditions
- complex corrosion mechanisms
- themodynamics and kinetics of corrosion are very dependent on composition and structure
what are four examples of applications where ceramics can be used because of their chemical inertness?
- containment of nuclear waste using borosilicate glass
- TiB2 for aluminum smelting cathodes
- bioglass to repair bones
- ceramic implants (ZrO2 and TiO2)
what is an optical property defined by
how a material interacts with light
what is photonics
photonics is a broad category that includes any phenomena and devices that deal with the generation, manipulation, and sensing of light
what are the 5 parameters of optical properties
- absorption
- refraction
- transmission
- reflection
- scattering
what are 4 different categories of optical property behavior in ceramics?
- translucency, transparency, and opacity
- glass
- birefringence
- color
What are 4 different examples of optical applications of materials
- fiber optics
- LASERs
- photochromics (glass, silver halides, pigments)
- transparent ceramic armor
What are electric/dielectric properties controlled by
- long range transport (conductivity) of mobile carriers (electrons, ions, etc.)
- short range movement of electrical dipoles (polarization) in specific domains
What are some examples of ceramics being used for their electric/dielectric properties?
capacitors, insulators, electronic packaging, batteries
What are three different properties we study relating to the thermal properties of ceramics?
- thermal conductivity
- thermal expansion
- thermal shock resistance (TSR)
What is thermal conductivity
ability of a material to conduct heat (W/m-K)
are most ceramics good or poor thermal conductors
poor
What are three examples of ceramics with high thermal conductivity
AIN, TiB2, ZrB2
what is the symbol for thermal conductivity
k
what happens when you add porosity to a ceramic
lowers the thermal conductivity (k) of ceramics
What is thermal expansion
the ability of a ceramic to expand/contact during heating and cooling
do ceramics exhibit lower or higher thermal expansion than metals
lower
what ceramic has the lowest expansion coefficient
SiO2
what is thermal shock resistance
TSR, the ability of the ceramic to resist fracture when cooled/heated
what does high TSR relate to
high TSR = high k + low thermal expansion
what are 4 examples of ceramics where their thermal properties are used
- Si3N4 rotors
- leading edges (aircraft)
- shuttle tiles
- SiO2 aerogel
what are three different properties that you look at when evaluating the mechanical properties of materials
- strength
- fracture toughnes
- hardness
what are the symbols for strength, fracture toughness, and hardness
Strength σƒ
fracture toughness K IC
Hardness Hv
what is strength and what is it measured in
resistance to fracture (MPa)
how do you test for strength
4-point bend test
what is the general strength of ceramics
ceramics have theoretical strengths higher than most other material but have a wider variation in values because of flaws
what is fracture toughenss
resistance to crack propogation (MPa-m^1/2)
how do you test for fracture toughness
single edge notched beam (SENB) or Vickers indentation
do ceramics have a high or low fracture toughness and why?
low because they can’t plastically deform
what can improve ceramic fracture toughness
microstructural design and reinforcement
what is hardness and what is the unit
resistance to indentation (Kg/mm^2)
how do you test for hardness
diamond pyramic method (Vickers)
do ceramics generally have high or low hardness? why?
high hardness due to their ionic/covalent bonding than other mateirals
what are three different applications that take advantage of the mechanical properties of ceramics?
- protective armor
- ceramic implants
- engines
What are the significant properties where ceramics outperform other materials?
- high temperature stability
- elastic modulus
- compressive strength
- chemical inertness
- thermal coeff. expans. coeff
