MatSci 201 Extra Ceramics and Polymer Questions

MatSci 201 Extra Ceramics and Polymer Questions -...

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Unformatted text preview: MatSci
201:
Intro
to
Materials
 Selected
questions
on
ceramics
and
polymers
 
 1. Refer
to
the
phase
diagram
of
zirconia‐calcia
in
your
notes.

Can
one
rely
on
 transformation
toughening
for
zirconia
that
has
3wt%
calcia
added
at
1100
 °C?

at
100
°C?

Why
or
why
not?
 
 At
1100°C,
the
material
is
in
the
tetragonal+cube
phase
field.

Therefore,
 there
is
no
driving
force
for
the
transformation
of
tetragonal
material
to
 monoclinic.

If
there
is
no
transformation,
there
is
no
toughening.

At
100°C,
 tetragonal
particles
which
were
unable
to
transform
on
cooling
due
to
 constraint
from
the
cubic
matrix
will
transform
in
the
presence
of
a
crack.

 When
they
transform
there
is
a
volume
expansion
which
acts
to
close
the
 cracks
and
leads
to
increased
toughness.
 
 2.

 For
each
of
the
monomers
shown
below
identify
whether
they
will
 polymerize
via
addition
or
condensation
polymerization.
 
 Solution
 A
–
condensation
 B
–
addition
 C
–
condensation
 D
–
addition
 
 
 3. Callister,
Question
14.9
 
 
 
 4.
(a)
Explain
why
thermosets
and
traditional
cross‐linked
rubbers
are
unable
to
 be
recycled.
 
 (b)
Explain
why
thermoplastics
and
thermoplastic
elastomers
are
recyclable.
 
 Solution
 (a)
Because
thermosets
are
formed
from
multifunctional
monomers,
they
form
a
 network
structure.
When
the
structure
is
heated,
the
material
will
burn
before
it
will
 melt.
The
same
is
true
of
cross‐linked
rubbers.
 (b)
Thermoplastics
are
linear
molecules
held
together
by
weak
secondary
bonds
 (van
der
Waals
forces).
When
heated,
thermoplastics
melt
and
then
can
be
 reshaped.
 
 
 ...
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This note was uploaded on 11/21/2011 for the course MAT SCI 201 taught by Professor Matsci during the Spring '10 term at Northwestern.

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