Ceramic Problem Set
In a hypothetical ceramic AX, the radius and atomic weight of atom X is 0.167 nm and 133 g/mole while that of atom A is 0.181 nm and 35.0 g/mole.
a) Draw the unit cell of this AX crystal. Label the atoms A and X in your figure.)
b) Calculate the density of the AX ceramic. (NAvogadro = 6.022x1023, 1nm = 1x10-9m
a) CsCl type structure (BCC)
b) V = 6.4x10^-23 cm^3
therefore density = 4.36g/cm^3
Whats the definition of a Ceramic?
A ceramic is an ordered compound consisting of metallic and nonmetallic atoms.
What is a Polymer?
A material made of long molecules: each molecule consists of a small molecular unit that is repeated many, hundreds or thousands of, times
A blended polymer differs from a copolymer because:
Blends combine separate polymers physically
The table below lists the measured distribution of molecular weight for a certain polyvinyl chloride (PVC) polymer.
a) Calculate the average molecular weight of this polymer.
b) Calculate the average degree of polymerization
M = 33,040 g/mole
DOP = 529
In a hypothetical ceramic AB, the radius and atomic weight of atom A is 0.19 nm and 40.0
g/mole while that of atom B is 0.10 nm and 25.0 g/mole.
a) Draw the unit cell of the AB crystal. Label the atoms A and B in your figure.
b) Calculate the density of the AB ceramic
a) NaCl structure
b) density = 2.21g/cm^3
What structure does SiO2 have? (Quartz)
Complex Structure (NOT AX, β΄ #Si =/= #O2)
What is the Degree of Polymerization and it's Formula?
number of monomers within a polymer
= mol. weight of monomer/mol. weight of polymer
The strength of a thermoplastic polymer increases primarily when:
Molecular weight increases
Sketch portions of a linear polypropylene molecule for different configurations.
a) Syndiotactic polypropylene
b) Atactic polypropylene
c) Isotactic polypropylene
Pull it up in a diff tab
The TTT diagram for borosilicate glass is shown below in Fig.1 and the viscosity of this material is plotted versus temperature in Fig. 2. Describe, with reference to these diagrams, the process by which one could transform a solid piece of borosilicate glass into a bottle that is 100% crystalline without heating the material above Tm = 1000 C.
Since we are starting from a solid Borosilicate Glass, we know it is in the noncrystalline state. Since the softening point of
Borosilicate glass is about 850oC (Fig. 2), we can make this material into the shape of a bottle by simply heating it to above
850oC, say 900oC, and blow molding it into a mold of the shape of the desired bottle. Since blow molding is a rapid
fabrication process, we simply need to hold the newly made bottle in the mold at 900oC for about 100 minutes to cause it to
crystallize (see Fig. 1). Upon cooling we will then have a 100% crystalline borosilicate bottle!
How does adding soda prevent crystalline structure in Quartz, and what is made when soda is added to SiO2
Na+ ions prevent the formation of SiO2 crystals, and it makes window glass
What are the three general types of polymers, and what are they?
Thermoplastic : The long polymer molecules are not attached to each other by strong covalent bonds
Thermosetting : The long polymer molecules are attached to each other by strong covalent bonds (heavily cross-linked).
Elastomer : The long polymer molecules are attached to each other by covalent bonds but only in a few locations (lightly cross-linked)
Carbon fibers are produced from PAN fibers using which critical step?
Oxidation to cross-link the polymer
Draw the shape of the tensile stress-strain curve of a typical thermoplastic polymer and explain what is happening to the configuration of the molecules during plastic deformation to result in the shape of the curve
The typical stress-strain response for a thermoplastic polymer is
shown on the right. The way thermoplastic polymers deform plastically is
by the untangling and stretching of the long polymer molecules. This
process results in the molecules becoming more closely aligned. The
closer alignment of the molecules results in the deformed material
becoming stronger than the undeformed material. As a result, after one
section of the test sample deforms it becomes considerably harder than
the surrounding material and this causes the surrounding material to
deform. The end result is that the sample doesnβt break in the first region
where a neck develops but rather continues to stretch until all the test
sample undergoes large strain before fracture finally occurs. It is for this
reason that Thermoplastic polymers can undergo much higher strains
before fracturing than crystalline metals
PULL UP PICTUREEEE
Components made from traditional ceramic materials, such as porcelain, are often made by the slip casting technique. Describe how the slip-casting process is performed. In your description be sure to explain the role of water and the porous mold in the process. A labelled diagram may help in your description.
Porcelain is a composite consisting of crystalline ceramic reinforcing particles (SiO2 and Al2O3)
encased in a noncrystalline (feldspar) ceramic matrix. The first step in making a porcelain
component by slip-casting is to mix the crystalline and the noncrystalline particles together in a
water slurry suspension (the slip). The purpose of the water is to carry the particles into the mold
and to fill the mold. The mold has the shape of the component that is to be made and is
constructed from a porous material such as plaster. When the slip is poured into the mold, water
begins to diffuse into the porous mold leaving behind a thin layer of crystalline and noncrystalline
ceramic powders over the entire surface of the mold cavity. The mold is then turned upside down
and the remaining liquid slip is poured out. The remaining thin ceramic powder layer is then
carefully removed from the mold and heated to first evaporate any remaining water and then melt- (it cuts off lmao)
What are the two mechanical properties window glass and quartz have in common?
- transparent
- brittle
What are the requirements for crystalline, or semi-crystalline, polymers?
1. Must have short molecules
- Short molecules are easier to fold back upon themselves uniformly.
2. Must have small isotactic side-groups
- Large, complex, and randomly oriented side groups prevent close packing of the molecules
3. Must be linear molecules
- Branched molecules cannot be closely folded back upon themselves
Calculate the molecular weight of the Polymethylmethacrylate (PMMA (Plexiglass)) isomer. The atomic weight of Hydrogen is 1.008 g/mole, Carbon is 12.01 g/mole, and Oxygen is 16.00g/mole.
= 100.114π/ππππ
Ok this whole thing is a picture im just gonna pull this up on owl
ANSWER YAAAYYY
A plot of viscosity versus 1/Temperature and a TTT diagram of a hypothetical ceramic are shown below. You wish to make a 50% crystalline bottle of this material using a process involving blow-molding followed by isothermal annealing. Plot on the empty T versus Time graph shown below the Temperature profile that could be used to produce this part. Be sure to label how each region of your plot affects the microstructure of the ceramic part
PULL IT UP ON ANOTHER TAB
What's the problem with sintering 100% crystalline ceramics? How do you solve it in both Traditional Ceramics and Cermets ?
1) It takes a long time to completely sinter the powders. You can't get rid of all the porosity.
2) Requires 3 ingredients (clay, water, and sintering powder (Al2O3/SiO2))
The low melting temp. non-crystalline ceramic glass melts and covers the non-melted crystalline ceramic powders thus binding them together.
The advantage of this liquid-phase sintering process is that it results in nearly zero porosity.
3)Cermets are composites consisting of crystalline ceramic powders (carbides) imbedded in a crystalline metal binder.
β’ The carbide powders, WC or TiC or Cr3C2, comprise 80% to 95% of the volume.
β’ Carbide powders must be sintered with a metal binder to provide a strong and pore-free part
- Cobalt works best with WC
- Nickel is better with TiC and Cr3C2
Whats the problem with branched polymers, and how do we solve it?
- Branching increases polymer strength but also decreases packing density
- The decreased density outweighs the strengthening effect.
- Therefore, molecular branching is avoided when fabricating thermoplastic polymers
we can not solve this problem
A polyethylene rope weighs 2.5 kg/m. If each polyethylene
molecule contains 8000 repeat units (isomers).
a) Calculate the number of polyethylene chains (molecules) in a 4 m length of rope.
b) Calculate the total length of chains in the rope assuming that the length of one repeat unit is 0.24495 nm
The atomic weight of Hydrogen is 1.008 g/mole, Carbon is 12.01 g/mole, and Oxygen is 16.00 g/mole.
a) 2.69x10^22ππππππ’πππ
b)5.27=10^13ππ
The repeat unit of polystyrene is shown below.
a) Is this polystyrene a thermosetting polymer? Why?
b) Draw a syndiotactic polystyrene molecule having a degree of polymerization of n = 4