Ceramic Final Review
Application of pyrex in the astronomy feild
used as large telescope mirrors bc of its low thermal expansion coefficient it wouldnt break or blur in changes of heat
what prevents lightening from burning out an electrical circuit
varistor
Application of SiC in automobil
water pump
Critical properties of thermally conducting ceramics
*conductivity melting temp thermal shock
Critical Properties of Thermally insulating ceramics and if you want them to be high or low
- Thermal conductivity-low - Melting/Decomposition Temp- High -Heat capacity-depends on application
4 steps in forming glass
- batching - melting - formation - annealing
Define Refractory Ceramics
- cost effective materials that maintain form and function at elevated temperatures. -used to build a furnace or other high temperature vessel.
how does tempered glass fail
- outside cools fast- into compression -inside cools slow- into tension - fails when outside compressive layer is broken and inside layers shatter into may peices inside is still contained in compressive layer
What's the basic idea behind thermally insulating ceramics
- protect something against heat (a lower Tm material) - keep heat in and around a certain area - keep heat away from critical components
what two main aspects of glass distinguish it from other materials
-no definite melting temp -no long range order in their structure
List and describe the four formation techniques that were discussed in class and indicate the approximate water range for each.
1. Dry Processing a. <5% volume H2O b. This uses uniaxial pressure and a constant cross section to press the clay based material into a uniform shape. 2. Stiff Plastic-Extrusion a. 5-15% volume H2O b. This also uses a uniform cross section to press clay based materials into a uniform, easily repeatable shape. 3. Soft Plastic-Throwing a. 15-30% volume H2O b. There are two types: jiggering and jollying. Jiggering can be used to make a more shape that has edges (like a bowl) and jollying uses a flat knife to make more flat shapes (such as plates). The thickness can be controlled. Molds, such as Plaster of Paris, may be used. 4. Slip Casting a. 30% volume H2O b. A slip is poured into a mold of any shape and left in until the slip reaches the desired thickness.
List and describe four techniques discussed in the lecture that are used to produce refractory ceramics
1. Press and Fire: Refractory ceramics are pressed with uniaxial pressing and then fired at a high temperature. 2. Press and Cured: This uses polymeric binding and cured to cross link the polymer. 3. Unshaped/Castable/Monolithic: Refractory ceramics are procured from a bag of material that is mixed with water and poured into a form, 4. Fusion Cast: Molten glass is poured and takes 7-14 days to cool. It ends up having less than .5% porosity.
How to achieve low thermal conductivity
1. choose a ceramic with a low conductivity (heavy) 2. form ceramics as porous bricks or fibrous insulation
What are the 5 critical material properties that are important for thermal shock resistant ceramics and if you want them high or low
1. coefficient of thermal expansion-low 2. elastic modulus- low 3. thermal conductivity- high 4. strength- high 5. fracture toughness-high
5 examples of thermally insulating ceramic applications
1. refractory bricks and linings 2. space shuttle tiles 3. thermal barrier coatings 4. flaps and seals for jet aircrafts 5. divert and altitude control systems for missals
typical conversion efficiency of an Si based solar cell
15-20%
Thermal conductivity of diamond
2000
What is the typical thickness of a TBC Zirconia? How much does it lower the operating temp of the underlying metal
25/1000 of an inch lowers by 400 degrees Fahrenheit
what is the wavelength humans can see and which are the higheste
400nm(blue)-700nm (red) blue has more energy than red gamma rays are the highest
What wavelength do humans give off
9.6 um
Which of the following oxides is notconsidered to be a glass forming oxide? a) B2O3, b) TiO2, c) SiO2
B
what is the most important ceramic being used in the armed forces to protect against small arms fire
Boron Carbide
What typical phases are present in cement? Which of them is the major phase
C2C, C3S, C3A and C4AF. C3S
name and chem compound for a non Si used to make solar cells
Cadmium Telluride (CdTe)
Which two alloys are most commonly used in load bearing implant applications?
CoCrMo and Titanium
List two disadvantages and 3 advantages of fiber-based refractory ceramics.
Dis: Fiber based refractory ceramics are very weak and potentially hazardous. Adv: great insulator, cheap, energy efficient
Ceramics were the namesake of the Stone Age. What role did ceramic materials play in the evolution of the Stone Age to the Bronze Age and then on to the Iron Age?
During the stone age, primitive people used rocks for many things because it was the only material they were able to use. They created weapons to hunt with, drew on cave walls with soil mixed with water, and crafted clay into shapes. Earthenware allowed for a transition to settled life and the earliest stages of communication began with clay tokens with markings scratched into them, eventually expanding into pictographs on tablets. As the metal ages began, ceramics were the only materials that could handle the high temperatures required for extracting ores from metals, and thus the kiln was developed. The high heat the ceramics were exposed to also strengthened the ceramics themselves and it was discovered that flame sensitive paint could be put on the kilns when they were exposed to heat and then become permanent parts of the kiln. Glazes were also discovered in this time. A final major e - during metal ages ceramics had a high heat resistance and could handle the temps it took to extract the ores from metals, pottery continued to degelop, kiln improved, high intesneity firing increased the strength of ceramics, was discovered that flame sensitive paint could be put on a kiln and it would become permananemtyl part of the pot during firing, glazes discovred, Potter's wheel invented when metals were expensive and could only be afforded by the wealthy
How did the development of earthenware impact world exploration?
Earthenware was the earliest stages of ceramics and pottery. It allowed people to transition from a nomadic lifestyle to a more settled lifestyle because earthenware could be used for cooking and food storage so people did not have to constantly follow their food. The settled lifestyle allowed for planting and growing of crops. Exploration was able to begin because travellers could go farther from home carrying food and water in earthenware containers.
T or F Glass has a greater density than a crystal of the same composition:
F
T of F: A good way to raise the thermal conductivity of a material is to increase the amount of porosity ("dead-air")?
False
4 examples of ceramic materials with melting point over 3300 C
HfC (Hafnium Carbide 3890C) ZrC (Zirconium Carbide 3532C) NbC (Niobium Carbide 2490C) TaC (Tantalum Carbide 3880C)
Explain the concept and utility of classifying oxides based on anion to cation ratio
Many oxides are in the form of MeO, with various numbers of molecules of metals and oxygen. A high metal to oxide ratio (cation to anion ratio)-one that has many metals compared to few oxygens- will mean the oxide is more basic. A small metal to oxide (cation to anion ratio)-one that has many oxygens compared to few metals-is more acidic. Determining if an oxide is acidic or basic will help determine its properties and what areas it will be most useful in.
Where are venetian glassmakers located and how did they keep their techniques secret from the world
Murano Italy-if they left they could be killed no one except masters and apprentices were allowed in glass shops location trade respect and government enforcement kept the techniques a secret
doping Si with an electron acceptor makes a __-type for junctions
N
doping Si with an electron donor makes a __-type for junctions
P
what fuel cell can make H2 and O2 by electrolysis
PEM cell
what in hair dryers detects heat
PTCR devices that increase resistance with increase temp increases to the point that the current can no longer flow and the device is shut off
Why do we want to use glass in composites
Plastics in composites form matrices that holds fibers together and protects the,, the structures of fibers provide high strength and stiffness when incorporated into composites. Fibers in composites require less maintenance and have corrosive resistance
What impact does porosity have on heat conduction
Porosity determines how fast it slow the material will cool down. Pores are dead air and a poor conductor of heat
list and describe the 5 processes that occur when light is shined on a glass
Reflection: the light hits the surface and bounces off; there is a loss of intensity Refraction: light hits the glass and bends to a slightly different angle Transmission: where the light has gone all the way through the glass Absorption: Light goes into the glass but does not go back out Scattering: light hits an impurity in the glass and goes in many different directions
T or F The symmetry of polycrystalline systems is described using what are called the Curie Limiting Groups:
T
a varistor is a type of resistor used to protect electrical equipment from voltage surges T or F
T
What is the process engineers developed to allow production of millions of tons of high purity alumina annually? (name, date, description)
The Bayer Process: 1887 Takes Bauxite (30-60% alumina) and sifts it to get only alumina. The Bauxite is crushed and milled, heated in a pressurized vessel with NaOH , and then Na(Al(OH)4) is extracted. The alumina is crystalized and put in a kiln
What distinguishes between modern and traditional ceramics?
Traditional ceramics are prepared from abundant materials; modern ceramics are made from specifically purified or synthetic starting materials AND modern ceramics are more specified to do their job
SI units for thermal conductivity
W/mk
Describe microstructure changes in typical cement paste over the course of hydration.
Water gets bound into solid products, water in pores reduces and solid volume increases as strength develops. Solid to solid connectivity increases and a percolated network is formed.
Freeze-thaw cycles could damage concrete. Explain how such damage occurs, and state two mechanisms to mitigate such damage.
Water seeps into concrete, forms ice that expands and causes cracks to form. Use less water to reduce porosity, pore connectivity and permeability, or use reactive cements that consume more water, or corrosion resistant reinforcing steels.
What ceramic material is often made into cutting tools
Zirconia
Describe an application that currently uses a TBC in a production aerospace component
Zirconia (ZrO2) is used as ceramic tiles to cover the space shuttle. Also used for commercial and military engines. It allows the underlying metals to withstand more heat and the engine can run at a hotter temp. This increases the power of the engine and decreases the amount of fuel used
Which one of the following is a good example of a ceramic being used as a thermal conductor: a) substrates for microelectronics, b) armor, c) space shuttle tile
a
t of f most material properties change with temp
a
define the term mineral
a naturally occurring crystal structure that has a known range of chemistry and crystal structure
Define the term rock
a solid made up of 2 or more minerals
List and explain the steps involved in producing a clay-based ceramic?
a. Batching: This is where one will define and collect the necessary ingredients and supplies. b. Mixing: The ingredients are mixed until homogeneous. c. Formation: One of four techniques is applied to the clay to mold it into the desired shape. d. Dry: The mold is heated in a way that keeps the rate of evaporation and the rate of internal movement the same (by adjusting the relative humidity to slow down the evaporation) and heated at about 100 degrees Celsius to remove the H2). e. Firing/Sintering: Heat of about 300 degrees Celcius to 900 degrees Celsius is applied to remove decimally bound water (Temperatures on the higher end of that scale are not used for clay).
what is thermal conductivity and why is it important
ability of a material to transfer heat via the motion of electrons, phonons, photons, etc important for applications where heat has to be transferred from one stream to another
Which of the following is/are normally associated with refractory materials?
ability to withstand high temperatures
transmitted color is due to
absorbtion
What is the most important modern ceramic
alumina
n example of a hard ceramic used in implants is?
alumina
Plasticity is achieved by the addition of what type of clay to ceramic formulations:
ball clay
how could you generate H2 to run a SOFC
biomass can be degraded in the prescence of steam and oxygen under high pressure to release h2 gas and the other molecules can be filtered out of the gas
Hardness is measure of a materials resistance to
bond movement
Another material that is being used in place of silicon (Si) for solar cells is: a) NiAl, b) GaO2, c) GaAs
c
What is the name for the porous inner surface of bone that protect the marrow and is also sometimes called "spongy" bone?
cancellous bone
Describe the ceramic materials that are used to produce the nose cone and wing leading edges for the Space Shuttles?
carbon-carbon composites are used because they can withstand high temperatures The C/C composite is coated with with a layer of silicon carbide and then coated with a later of silicon dioxide so that it does not burn when it comes into contact with the oxygen air at high temps
what makes up and SOFC
cathode and anode with electrode between the two
What are the four main component materials used to formulate concrete
cemente, water, sand, and aggregate
How tough Transformation Toughened Zirconia work to provide high toughness
changes shape at the tip of the crack, which causes the crack to stop forming
What is primary clay?
clay found exactly where it was formed
What is secondary clay?
clay that has been carried and worn down by water, not large masses of clay, more plasticity (organic materials increase plasticity )
Tm is a material property tied to: ___ and _____
composition and bond strength
4 types of mechanical stress
compression, shear, tension, flexure
Difference between compressive and tensil stress which is more likely to cause failure in ceramic materials and why
compressive closes flaws, tensile adds stress at the flaws (pulls them apart) tensile stress is more likely to cause failure
Where does silicon nitride come from
created when engineers heated Si with N at 2200C
What is the lightest ceramic
diamond
the most important property for the capacitator is the
dielectric constant
one of the reasons zirconia is used as a suitable substitute for diamonds is because it converts white light into a rainbow of colors with an effect called
dispersion
what is a pyroelectric and what are they made from and an example
electrics that detenct heat and will output an electrical signal ex motion detectors senses IR waves and turns on lights made from polar crystals
what is a piezoelectric? application?
electrics that give an electrical output when a mechanical input is applied fire starting mechanism of a grill
The majority of the world's magnesium oxide comes from where?
extracted from seawater
t or f Crystalline ceramics are lessstable under aqueous conditions compared toamorphous materials
f
t or f clay comes from the weathering of mica in granite
f
t or f the iron age occurred before the bronze age
f
t or f when trying to spear a fish underwater you should aim above the fish
f
Which component of a triaxial porcelain acts as a flux promote glass formation:
feldspar
application where ceramic fibers are being used as park of a ceramic matrix composite
fiberglass when strips of fibers are put in a mold to create the hull of a boat
What type of cells produce collagen fibers?
fibroblasts
Why is silicon nitride a useful ceramic for many applications
has a high melting temp, high strength, and high thermal shock resistance
Do you want light or heavy mass ceramics to be insulators and why?
heavy mass bc particles have less vibrations=more heat is needed for movement
List three reasons why ceramic materials typically appear opaque?
impurities pores grain boundaries
In many cases metals form a stable oxide layer on their surface that protects the metal beneath from further oxidation. A notable exception is ______ which forms an unstable oxide layer that allows further oxidation?
iron
Acidic oxides have an anion to cation ration that
is greater than 3 to 2
Is the energy gap large or small in insulators
large
What is the role of a flux in glass formation
lower the melting temp for glass
Advantages of monolithic refractory over shaped lining?
monolithic comes in a bag and acts similar to cement because water can be added and it can be poured into a mold and take on any shape. Monolithic have less joins an are less costly to produce
What two different ceramic materials are sued for the nose cone ad for the white tiles for the space shuttle
nose cone: C/C composites coated with cilicon carbide and silicon dioxide White tiles: silica put in water and heat dried to get a material with lots of open space and strength
The formation of a direct interface between an implant and a bone without the need for soft tissue is called?
osseointegration
Which type of cells are bone forming cells found in the body?
osteoblasts
Which type of cells found in the body break down bone tissue?
osteoclasts
The ability to encourage the growth of bone onto the surface of an implant is called?
osteoconduction
application of zirconia in automobil
oxygen sensor
Photons and Phonons are both conductors of heat. Which is responsible for heat conduction at high temps and which at low temps
phonons: low temps Photons: high temps
Hydroxyapatite has three principle components calcium, a hydroxyl and _____?
phosphates
photovoltaic meaning and origin
photo--> greek work phos meaning light voltaic--> alesandro Volta means: ability to produce a current from light energy
property w optical input and electrical output
photoelectric converts light energy to electric energy
Mechanical deformation of a material produces a current and induces a voltage: This effect is called
piezoelectric effect
5 Examples of Modern Ceramics
piezoelectric, boron nitride, ceramic magnet, fluorescent lights containing a ceramic phosphor, fiberglass insulation
Which polymer is commonly used as a part of a hip replacement?
poly(ethylene) (PE)
Which of the polymers below is commonly used in bone cements?
poly(methyl methacrylate) (PMMA),
Motion detectors contain what wort of material to sense moving warm objects
pyroelectric
What is the raw material for silica?
quartz
Thermal protection tiles on the top surface of the space shuttle have a white coating that:
reflects heat away from the shuttle
Which of the following constituents of many bioglasses is not a macroelement found in large quantities in the body?
silicon
is the energy gap large or small in semiconductors
small
3 common fluxes for silica
sodium carbonate, potassium carbonate, calcium carbonate
what does NZP stand for and what capability do these materials have
sodium zirconium phosphate very low thermal expansion coefficients therefor a high Delta T max and can be heated to a very high temp and quickly cooled without breaking
What is the name for the glass forming method that uses liquid alkoxide precursors?
sol-gel
SOFC stands for
solid oxide fuel cell
application of alumina in automobil
spark plug sensor
The amount of stressnecessary to starta crack propagating in a material is a measure of the materials:
strength
UV light has a shorter wavelength than infared t or f
t
a thin layer of metal can transmit visible light but block IR t or f
t
t or f Cobalt chromium molybdenum alloys are valuable as biomaterials largely because of their high modulus?
t
t or f flourenscent lights convert UV light to visible light
t
t or f light is polarized when reflected off a surface
t
the peak of the suds spectral irradiance falls within the visible range t or f
t
What is fracture toughness
the amount of stress necessary to drive a crack through a material
What is an oxide ceramic?
the cation and anion are very different in size
why can ceramics and plastics be transparent
the electrons are localized and light can pass through the energy gaps between electrons
The property of a ceramic which is a direct measurement of its ability to transfer heat due to the motions of atoms or molecules is:
thermal conductivity
The safety device that prevents a hair dryer from overheating is called a:
thermistor
Ceramic can be made transparent because
they have covalent and/or ionic bonds
Metals can not be transparent because
they have free electrons that absorb the light
Why are ceramic fibers stronger than bulk ceramics
they're much smaller=can have smaller flaws
What is a thermal barrier coating (TBC)
thin ceramics in gas engines used to protect underlying metal from the high temp inside the engine
5 Examples of Traditional Ceramics
tile, glass, bricks, concrete, porcelain
Describe the process for making white and black silica fiber based Space Shuttle Tiles
tiny fibers of silica are suspended in water and pies into a porous mold. Water is sucked out through the pores of the mold, the fibers intertwine to form its shape but hold a structure that is over 80% open space. This structure is dried and fired at a high temp and the fibers bond together where they contact each other to give the material strength as the open space remains and the pores are filled w air the material must be cut to the right size and a heave glassy surface coating deposited onto it to protect against erosion and to keep water from soaking into the pores the black coating also radiates heat into the atmosphere almost as fast as friction produces heat
mechanical input optical output
triboluminescence
mechanical input to a material that produces emission of light is called
triboluminescence
What does "ULE' gas stand for and what country developed it
ultralow expansion glass, invented by corning glass works
