Homework 1

Question 1

For a ceramic compound, what are the two characteristics of the component ions that determine the crystal structure

Answer 1

1) the magnitude of the electrical charge on each ion, and

2) the relative sizes of the cations and anions.

Question 2

Compute the atomic packing factor for the rock salt crystal structure in which rC/rA = 0.414

Answer 2

Apf=Vs/Vc
Vs=Volume of sphere add 4 per sphere volume FCC
Solve for one Radius
Vc= 2(Ra+Rc)^3

Question 3

Calculate the density of FeO, given that it has the rock salt crystal structure

Answer 3

n’=4 for crystal structure
Vc= (ionic radii*radius of each one add them)^3
Na= avogrados
A=g/mol

Question 4

Suppose that Li2O is added as an impurity to CaO. If the Li+ substitutes for Ca2+, what kind of vacancies would you expect to form? How many of these vacancies are created for every Li+ added?

Answer 4

Negative charges are eliminated by creating oxygen vacancies, and for every two Li+ ions added, a single oxygen (O2-) vacancy is formed

Question 5

Suppose that CaCl2 is added as an impurity to CaO. If the Cl- substitutes for O2-, what kind of vacancies would you expect to form? How many of the vacancies are created for every Cl- added?

Answer 5

For Cl- substituting for O2- in CaO, calcium vacancies would be created. For each Cl- substituting for an O2-, one negative charge is removed; in order to maintain charge neutrality, two Cl- ions will lead to the formation of one calcium (Ca2+) vacancy

Question 6

Cite one reason why ceramic materials are, in general, harder yet more brittle than metals

Answer 6

because they (ceramics) have fewer slip systems, and, therefore, dislocation motion is highly restricted

Question 7

What is crystallization in glasses?

Cite two properties that may be improved by crystallization in glasses

Answer 7

Crystallization is the process whereby a glass material is caused to transform to a crystalline solid.
Two properties that may be improved by crystallization are (1) a lower coefficient of thermal expansion, and (2) higher strength

Question 8

What is the distinction between glass transition temperature and melting temperature

Answer 8

Glass Temperature at which there is a change of slope for the specific volume vesus temp curve.
melting temp, is the temp at which there is a sudden and discontinous decrease in the specific volume vs temp curve

Question 9

Cite the two desirable characteristics of clay minerals relative to fabrication processes

Answer 9

1. they become hydroplastic (and therefore formable) when mixed with water
2. during firing, clays melt over a range of temperatures, which allows some fusion and bonding of the ware without complete melting and a loss of mechanical integrity and shape.

Question 10

What are the three main components of a whiteware ceramic such as porcelain

Answer 10

clay, quartz, and a flux

Question 11

What role does each component play in the forming and firing procedures

Answer 11

Quartz acts as a filler material.
Clay facilitates the forming operation since, when mixed with water, the mass may be made to become either hydroplastic or form a slip. shape of the piece being fired will be maintained.
The flux facilitates the formation of a glass having a relatively low melting temperature

Question 12

Convert nm to cm

Answer 12

divide by 10 million