This document discusses ceramics, including their classification, applications, and processing methods. It addresses how ceramics are classified into categories like glasses, clay products, refractories, and advanced ceramics. It also summarizes the main ceramic fabrication techniques of glass forming, particulate forming, and cementation. Key steps like drying, firing, and sintering are also outlined.

1. Chapter 13: Applications and
Chapter 13 - 1
Processing of Ceramics
ISSUES TO ADDRESS...
• How do we classify ceramics?
• What are some applications of ceramics?
• How is processing of ceramics different than for metals?

2. Classification of Ceramics
Chapter 13 - 2
Glasses Clay
products
Ceramic Materials
Refractories Abrasives Cements Advanced
ceramics
-optical
-composite
reinforce
-containers/
household
-whiteware
-structural
-bricks for
high T
(furnaces)
-sandpaper
-cutting
-polishing
-composites
-structural
-engine
rotors
valves
bearings
-sensors
Adapted from Fig. 13.1 and discussion in
Section 13.2-8, Callister & Rethwisch 8e.

3. Ceramics Application: Die Blanks
tensile
force
Chapter 13 - 3
Ao
die Ad
die
• Die blanks:
-- Need wear resistant properties!
• Die surface:
-- 4 mm polycrystalline diamond
particles that are sintered onto a
cemented tungsten carbide
substrate.
-- polycrystalline diamond gives uniform
hardness in all directions to reduce
wear.
Adapted from Fig. 11.8(d),
Callister & Rethwisch 8e.
Courtesy Martin Deakins, GE
Superabrasives, Worthington,
OH. Used with permission.

4. Chapter 13 - 4
Ceramics Application:
Cutting Tools
• Tools:
-- for grinding glass, tungsten,
carbide, ceramics
-- for cutting Si wafers
-- for oil drilling
oil drill bits blades
Single crystal
diamonds
polycrystalline
diamonds in a resin
matrix.
Photos courtesy Martin Deakins,
GE Superabrasives, Worthington,
OH. Used with permission.
• Materials:
-- manufactured single crystal
or polycrystalline diamonds
in a metal or resin matrix.
-- polycrystalline diamonds
resharpen by microfracturing
along cleavage planes.

5. Ceramics Application: Sensors
sensor
Chapter 13 - 5
• Example: ZrO2 as an oxygen sensor
• Principle: Increase diffusion rate of oxygen
to produce rapid response of sensor signal to
change in oxygen concentration
A substituting Ca2+ ion
removes a Zr4+ ion and
an O2- ion.
Ca2+
• Approach:
Add Ca impurity to ZrO2:
-- increases O2- vacancies
-- increases O2- diffusion rate
reference
gas at fixed
oxygen content
O2-
diffusion
gas with an
unknown, higher
oxygen content
+ -
voltage difference produced!
• Operation:
-- voltage difference produced when
O2- ions diffuse from the external
surface through the sensor to the
reference gas surface.
-- magnitude of voltage difference
 partial pressure of oxygen at the
external surface

6. • Materials to be used at high temperatures (e.g., in
Chapter 13 - 6
high temperature furnaces).
• Consider the Silica (SiO2) - Alumina (Al2O3) system.
• Silica refractories - silica rich - small additions of alumina
depress melting temperature (phase diagram):
Fig. 12.27, Callister &
Rethwisch 8e. (Fig. 12.27
adapted from F.J. Klug and
R.H. Doremus, J. Am. Cer.
Soc. 70(10), p. 758, 1987.)
Refractories
alumina
+
mullite
mullite
mullite
+ L
Liquid
(L)
mullite
+ crystobalite
Composition (wt% alumina)
2200
T(ºC)
2000
1800
1600
1400
0 20 40 60 80 100
crystobalite
+ L
alumina + L
3Al2O3-2SiO2

7. Chapter 13 - 7
Advanced Ceramics:
Materials for Automobile Engines
• Advantages:
– Operate at high
temperatures – high
efficiencies
– Low frictional losses
– Operate without a cooling
system
– Lower weights than
current engines
• Disadvantages:
– Ceramic materials are
brittle
– Difficult to remove internal
voids (that weaken
structures)
– Ceramic parts are difficult
to form and machine
• Potential candidate materials: Si3N4, SiC, & ZrO2
• Possible engine parts: engine block & piston coatings

8. Chapter 13 - 8
Advanced Ceramics:
Materials for Ceramic Armor
Components:
-- Outer facing plates
-- Backing sheet
Properties/Materials:
-- Facing plates -- hard and brittle
— fracture high-velocity projectile
— Al2O3, B4C, SiC, TiB2
-- Backing sheets -- soft and ductile
— deform and absorb remaining energy
— aluminum, synthetic fiber laminates

9. Ceramic Fabrication Methods (i)
• Pressing: plates, cheap glasses
• Fiber drawing:
Chapter 13 - 9
GLASS
FORMING
• Blowing of Glass Bottles:
Gob
Parison
mold
Pressing
operation
Suspended
parison
Finishing
mold
Compressed
air
Adapted from Fig. 13.8, Callister & Rethwisch 8e. (Fig. 13.8 is adapted from C.J.
Phillips, Glass: The Miracle Maker, Pittman Publishing Ltd., London.)
wind up
PARTICULATE
FORMING
CEMENTATION
-- glass formed by application of
pressure
-- mold is steel with graphite
lining

10. Chapter 13 -10
Sheet Glass Forming
• Sheet forming – continuous casting
– sheets are formed by floating the molten glass on a pool of
molten tin
Adapted from Fig. 13.9,
Callister & Rethwisch 8e.

11. • Basic Unit: Glass is noncrystalline (amorphous)
Na+
Chapter 13 - 11
4-
• Quartz is crystalline
SiO2:
• Fused silica is SiO2 to which no
impurities have been added
• Other common glasses contain
impurity ions such as Na+, Ca2+,
Al3+, and B3+
(soda glass)
Adapted from Fig. 12.11,
Callister & Rethwisch 8e.
Glass Structure
Si04 tetrahedron
Si4+
O2-
Si4+
O2-

12. Glass Properties
-- crystallize at melting temp, Tm
-- have abrupt change in spec.
Chapter 13 -12
• Specific volume (1/r) vs Temperature (T):
• Crystalline materials:
vol. at Tm
• Glasses:
-- do not crystallize
-- change in slope in spec. vol. curve at
glass transition temperature, Tg
-- transparent - no grain boundaries to
scatter light
Adapted from Fig. 13.6,
Callister & Rethwisch 8e.
T
Specific volume
Supercooled
Liquid
solid
Tm
Liquid
(disordered)
Crystalline
(i.e., ordered)
Tg
Glass
(amorphous solid)

13. Chapter 13 -13
Glass Properties: Viscosity
• Viscosity, h:
-- relates shear stress () and velocity gradient (dv/dy):

dv / dy
h 
h has units of (Pa-s)
dv
dy

velocity gradient

glass dv
dy

14. Log Glass Viscosity vs. Temperature
• soda-lime glass: 70% SiO2
balance Na2O (soda) & CaO (lime)
• borosilicate (Pyrex):
13% B2O3, 3.5% Na2O, 2.5% Al2O3
• Vycor: 96% SiO2, 4% B2O3
• fused silica: > 99.5 wt% SiO2
Chapter 13 -14
• Viscosity decreases with T
Viscosity [Pa-s]
1014
1010
106
102
1
strain point
annealing point
Working range:
glass-forming carried out
Tmelt
200 600 1000 1400 1800 T(ºC)
Adapted from Fig. 13.7, Callister & Rethwisch
8e. (Fig. 13.7 is from E.B. Shand,
Engineering Glass, Modern Materials, Vol. 6,
Academic Press, New York, 1968, p. 262.)

15. compression
Chapter 13 -15
Heat Treating Glass
• Annealing:
-- removes internal stresses caused by uneven cooling.
• Tempering:
-- puts surface of glass part into compression
-- suppresses growth of cracks from surface scratches.
-- sequence:
at room temp.
tension
compression
before cooling
hot
initial cooling
cooler
hot
cooler
-- Result: surface crack growth is suppressed.

16. Chapter 13 -16
• Ceramic Fabrication
techniques:
-- glass forming (pressing,
blowing, fiber drawing).
-- particulate forming
(hydroplastic forming, slip
casting, powder pressing, tape
casting)
-- cementation

17. Ceramic Fabrication Methods (iia)
• Mill (grind) and screen constituents: desired particle size
• Extrude this mass (e.g., into a brick)
Chapter 13 -17
container
ram billet
container
force
• Dry and fire the formed piece
die holder
die
Ao
extrusion Ad
Adapted from
Fig. 12.8(c),
Callister &
Rethwisch 8e.
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
Hydroplastic forming:

18. Ceramic Fabrication Methods (iia)
• Mill (grind) and screen constituents: desired particle size
Chapter 13 -18
• Slip casting operation
solid component
pour slip
into mold
• Dry and fire the cast piece
Adapted from Fig.
13.12, Callister &
Rethwisch 8e. (Fig.
13.12 is from W.D.
Kingery, Introduction
to Ceramics, John
Wiley and Sons,
Inc., 1960.)
drain
mold
hollow component
“green
ceramic”
pour slip
into mold
absorb water
into mold “green
ceramic”
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
Slip casting:
• Mix with water and other constituents to form slip

19. Typical Porcelain Composition
Chapter 13 -19
(50%) 1. Clay
(25%) 2. Filler – e.g. quartz (finely ground)
(25%) 3. Fluxing agent (Feldspar)
-- aluminosilicates plus K+, Na+, Ca+
-- upon firing - forms low-melting-temp. glass

20. charge
neutral
Chapter 13 -20
Hydroplasticity of Clay
• Clay is inexpensive
• When water is added to clay
-- water molecules fit in between
layered sheets
-- reduces degree of van der Waals
bonding
-- when external forces applied – clay
particles free to move past one
another – becomes hydroplastic
• Structure of
Kaolinite Clay:
Adapted from Fig. 12.14, Callister &
Rethwisch 8e. (Fig. 12.14 is adapted from
W.E. Hauth, "Crystal Chemistry of
Ceramics", American Ceramic Society
Bulletin, Vol. 30 (4), 1951, p. 140.)
Shear
weak van
der Waals
bonding
charge
neutral
Si
4+
Al
3+
-
OH
O
2-
Shear

21. • Drying: as water is removed - interparticle spacings decrease
Chapter 13 -21
– shrinkage .
Adapted from Fig.
13.13, Callister &
Rethwisch 8e. (Fig.
13.13 is from W.D.
Kingery, Introduction
to Ceramics, John
Wiley and Sons,
Inc., 1960.)
Drying and Firing
wet body partially dry completely dry
Drying too fast causes sample to warp or crack due to non-uniform shrinkage
• Firing:
-- heat treatment between
900-1400ºC
-- vitrification: liquid glass forms
from clay and flux – flows
between SiO2 particles. (Flux
lowers melting temperature). Adapted from Fig. 13.14, Callister & Rethwisch 8e.
(Fig. 13.14 is courtesy H.G. Brinkies, Swinburne
University of Technology, Hawthorn Campus,
Hawthorn, Victoria, Australia.)
Si02 particle
(quartz)
glass formed
around
the particle
micrograph of porcelain
70mm

22. Ceramic Fabrication Methods (iib)
GLASS
FORMING
PARTICULATE
FORMING
Powder Pressing: used for both clay and non-clay compositions.
• Powder (plus binder) compacted by pressure in a mold
-- Uniaxial compression - compacted in single direction
-- Isostatic (hydrostatic) compression - pressure applied by
Chapter 13 -22
fluid - powder in rubber envelope
-- Hot pressing - pressure + heat (
CEMENTATION

23. Chapter 13 -23
Sintering
Sintering occurs during firing of a piece that has
been powder pressed
-- powder particles coalesce and reduction of pore size
Adapted from Fig. 13.16,
Callister & Rethwisch 8e.
Aluminum oxide powder:
-- sintered at 1700ºC
for 6 minutes.
Adapted from Fig. 13.17, Callister
& Rethwisch 8e. (Fig. 13.17 is from
W.D. Kingery, H.K. Bowen, and
D.R. Uhlmann, Introduction to
Ceramics, 2nd ed., John Wiley and
Sons, Inc., 1976, p. 483.)
15mm

24. Chapter 13 -24
Tape Casting
• Thin sheets of green ceramic cast as flexible tape
• Used for integrated circuits and capacitors
• Slip = suspended ceramic particles + organic liquid
(contains binders, plasticizers)
Fig. 13.18, Callister &
Rethwisch 8e.

25. Ceramic Fabrication Methods (iii)
GLASS
FORMING
PARTICULATE
FORMING
CEMENTATION
• Hardening of a paste – paste formed by mixing cement
Chapter 13 -25
material with water
• Formation of rigid structures having varied and complex
shapes
• Hardening process – hydration (complex chemical
reactions involving water and cement particles)
• Portland cement – production of:
-- mix clay and lime-bearing minerals
-- calcine (heat to 1400ºC)
-- grind into fine powder

26. Chapter 13 -26
Summary
• Categories of ceramics:
-- glasses -- clay products
-- refractories -- cements
-- advanced ceramics
• Ceramic Fabrication techniques:
-- glass forming (pressing, blowing, fiber drawing).
-- particulate forming (hydroplastic forming, slip casting,
powder pressing, tape casting)
-- cementation
• Heat treating procedures
-- glasses—annealing, tempering
-- particulate formed pieces—drying, firing (sintering)

27. Chapter 13 -27
ANNOUNCEMENTS
Reading:
Core Problems:
Self-help Problems: