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08/21/2003

Patriotic Ceramics

We must have paid our dues. Our 39 hours without power a few
weeks ago apparently excused us from the Big Blackout of 2003
last week. We didn’t even have a power dip sufficient to put any
of our clocks in the flashing 8s mode. With high humidity and
temperatures in the 90s, I must join in commending New Yorkers
for the manner in which they handled the crisis. To have come
through that experience with so few deaths and no significant
increase in criminal activity is downright remarkable.

Uncomfortable as it must have been for those jammed together
waiting for ferries, trapped in elevators or having to walk up 20
or 30 flights of stairs, think of our troops in Iraq. With 120
degree temperatures and the bulky uniforms and equipment they
carry, it must make our blackout seem like a lark. The batteries
they carry that power their radio and other communications
equipment also aren’t too happy in such heat and tend to die
earlier than at normal temperatures. Hopefully, my colleagues
and I at Rutgers have contributed a bit to the battery expertise in
the military with our consulting and courses on batteries
presented at various Army and Navy facilities.

But let’s concentrate here on the problems of protecting and
lightening the load for our soldiers. The comic strip character
Hagar the Horrible has effective protection with his shield and
metal helmet. Those who follow the strip must marvel at how he
survives the plethora of arrows that have penetrated through his
primary defense system. Knights of old certainly had effective,
if cumbersome protection with their full suits of armor. Tank
crews were protected by heavy metal armor but the modern
battlefield puts a premium on speed and flexibility. Heavy armor
doesn’t promote either of these. An article in the August 11
issue of Chemical and Engineering news (C&EN) titled “Science
Transforms the Battlefield” by Mitch Jacoby discusses the role
that ceramics are playing in this regard.

When most of us think of ceramics, it’s probably about our
coffee mugs or our Corning cookware that can stand up to baking
and microwaving. For many years, ceramics have been taking
the place of metallic items or components as research and
development of tougher ceramics proceeds. One big advantage
of ceramics is that they check in typically at about half the
weight of their steel counterparts. For comparison, water has a
density of 1 gram per cubic centimeter; the density of various
types of steel are in the 7 to 8 range, while the density of most
ceramics are around 4.

Ceramics have also been getting stronger. A key characteristic is
something called “flexural strength”, the ability to stand up to
pressure without rupturing. The ceramic in your coffee cup will
probably stand up to 5 to 10 thousand pounds per square inch
(psi). (Don’t try this on your cup, please – it’ll end up in
smithereens!) A sintered and specially reacted form of silicon
nitride, a compound of silicon and nitrogen, can handle 140
thousand psi. Replacing the steel armor of a tank with lighter
ceramic shielding can make the tank faster, lower the fuel costs
to run it and make it more maneuverable. Even more critical is
the use of lighter ceramic armor in armored helicopters, in which
the lighter armor can make it possible for the helicopter to take
off with a load.

Ceramics also play a role in protecting our troops against
incoming enemy missiles. Ceramics based on silicon nitride are
used in the nose cones of Patriot missiles. The ceramic nose
cones have to stand up to the intense heat generated at supersonic
speeds. They also have to be transparent to microwave signals
emitted and received in order to guide the Patriots to their
moving targets.

When it comes to more intimate defense, the old question of
body armor arises. Near the end of the Vietnam War, a joint
effort by Los Alamos, Lawrence Livermore and Coors came up
with body armor made from aluminum oxide. Thinking you
might be wondering why the manufacturer of Brian Trumbore’s
favorite beer was involved with ceramic body armor, I visited the
Web sites coorstek.com and coorsjobs.com. Adolph Coors
bought The Golden Brewery in 1880 and in 1910 decided to
invest in Herold China and Pottery Company. This proved to be
a crucial decision. In the 1920s, with Prohibition in effect, it was
the sale of ceramics and, of all things, malted milk that kept
Coors solvent!

Back to aluminum oxide, it’s an extremely important material.
Aluminum is a very reactive element and, without the tough, thin
film of aluminum oxide that forms on the surface of aluminum,
items such as aluminum foil and pots and pans wouldn’t exist.
Although aluminum oxide has a density of 4, the body armor
developed for ceramic breast and back plates still weighs some
30 pounds. This puts a severe limitation on a soldier’s mobility
and the C&EN article suggests it is only good for sentry duty.

Scientists have come up with a lighter alternative in the form of
the compound boron carbide. This compound of boron and
carbon has a density of only 2.5 and today’s soldier is likely to
have a jacket with the lighter boron carbide body armor. This
also will be better contoured to the wearer than the older rigid
aluminum oxide-based armor. Panels of boron carbide are also
used to fortify seats, walls and floors of attack helicopters and
other military aircraft.

Actually, a suit of body armor is not just a fitted chunk of
ceramic. The ceramic will shatter the incoming projectile into
bits and pieces but it won’t do a good job of absorbing the energy
of the impact. You need a backing of some sort. The backing
typically is a composite of some sort that employs fibers that
resist the impact. These fibers capture the shrapnel from the
encounter of the bullet with the ceramic. DuPont’s Kevlar is one
such material. The Kevlar is effective thanks to in part its
tendency to line up in orderly arrays of tough fibers bundles.

The ideal body armor would stop all incoming projectiles before
reaching the body of the warrior. Boron carbide does a good job
of standing up to low energy projectiles such as bullets from a
handgun. However, it’s not that good when it comes to higher-
energy incoming objects. This puzzled researchers because the
properties of boron carbide indicated that it should perform much
better. Workers at Johns Hopkins and the Army Research
Laboratory’s Aberdeen Proving Ground found the answer,
published in the March 7 issue of Science.

Mingwei Chen, lead author of the Science article, and his
colleagues looked at fragments of boron carbide recovered from
an Army test facility with a high-resolution electron microscope.
The boron carbide in the body armor is a crystalline material.
What they found was that the impact of the high-energy
projectile hitting the crystalline boron carbide, resulted in the
presence of some very narrow bands of a glassy form of boron
carbide. These bands were only a couple of nanometers wide.
They determined that the structure in these tiny bands was
disordered, in contrast to the ordered arrangement of atoms in the
original crystalline boron carbide. This transformation from
crystalline to glassy material has been seen in other materials but
apparently not in any material as hard as boron carbide.

The glassy boron carbide is weaker than the crystalline form. As
a result, the material in the body armor fractures along the
narrow bands of glassy material. The challenge now is for the
researchers to come up with some new approaches, perhaps
changing the chemistry or additives or grain structure of the
boron nitride to up the resistance of the material to higher energy
impacts without forming glassy boron carbide.

Wouldn’t it be great if all this work on protecting our soldiers
proved unnecessary because everyone decided to live in peace?
The way things are going in the world today, I fear it’s more
likely that all of us will need to wear body armor in the future.
In the meantime, we can savor moments like that memorable
closing shot of Shaun Micheel in the PGA.

Allen F. Bortrum



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-08/21/2003-      
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Dr. Bortrum

08/21/2003

Patriotic Ceramics

We must have paid our dues. Our 39 hours without power a few
weeks ago apparently excused us from the Big Blackout of 2003
last week. We didn’t even have a power dip sufficient to put any
of our clocks in the flashing 8s mode. With high humidity and
temperatures in the 90s, I must join in commending New Yorkers
for the manner in which they handled the crisis. To have come
through that experience with so few deaths and no significant
increase in criminal activity is downright remarkable.

Uncomfortable as it must have been for those jammed together
waiting for ferries, trapped in elevators or having to walk up 20
or 30 flights of stairs, think of our troops in Iraq. With 120
degree temperatures and the bulky uniforms and equipment they
carry, it must make our blackout seem like a lark. The batteries
they carry that power their radio and other communications
equipment also aren’t too happy in such heat and tend to die
earlier than at normal temperatures. Hopefully, my colleagues
and I at Rutgers have contributed a bit to the battery expertise in
the military with our consulting and courses on batteries
presented at various Army and Navy facilities.

But let’s concentrate here on the problems of protecting and
lightening the load for our soldiers. The comic strip character
Hagar the Horrible has effective protection with his shield and
metal helmet. Those who follow the strip must marvel at how he
survives the plethora of arrows that have penetrated through his
primary defense system. Knights of old certainly had effective,
if cumbersome protection with their full suits of armor. Tank
crews were protected by heavy metal armor but the modern
battlefield puts a premium on speed and flexibility. Heavy armor
doesn’t promote either of these. An article in the August 11
issue of Chemical and Engineering news (C&EN) titled “Science
Transforms the Battlefield” by Mitch Jacoby discusses the role
that ceramics are playing in this regard.

When most of us think of ceramics, it’s probably about our
coffee mugs or our Corning cookware that can stand up to baking
and microwaving. For many years, ceramics have been taking
the place of metallic items or components as research and
development of tougher ceramics proceeds. One big advantage
of ceramics is that they check in typically at about half the
weight of their steel counterparts. For comparison, water has a
density of 1 gram per cubic centimeter; the density of various
types of steel are in the 7 to 8 range, while the density of most
ceramics are around 4.

Ceramics have also been getting stronger. A key characteristic is
something called “flexural strength”, the ability to stand up to
pressure without rupturing. The ceramic in your coffee cup will
probably stand up to 5 to 10 thousand pounds per square inch
(psi). (Don’t try this on your cup, please – it’ll end up in
smithereens!) A sintered and specially reacted form of silicon
nitride, a compound of silicon and nitrogen, can handle 140
thousand psi. Replacing the steel armor of a tank with lighter
ceramic shielding can make the tank faster, lower the fuel costs
to run it and make it more maneuverable. Even more critical is
the use of lighter ceramic armor in armored helicopters, in which
the lighter armor can make it possible for the helicopter to take
off with a load.

Ceramics also play a role in protecting our troops against
incoming enemy missiles. Ceramics based on silicon nitride are
used in the nose cones of Patriot missiles. The ceramic nose
cones have to stand up to the intense heat generated at supersonic
speeds. They also have to be transparent to microwave signals
emitted and received in order to guide the Patriots to their
moving targets.

When it comes to more intimate defense, the old question of
body armor arises. Near the end of the Vietnam War, a joint
effort by Los Alamos, Lawrence Livermore and Coors came up
with body armor made from aluminum oxide. Thinking you
might be wondering why the manufacturer of Brian Trumbore’s
favorite beer was involved with ceramic body armor, I visited the
Web sites coorstek.com and coorsjobs.com. Adolph Coors
bought The Golden Brewery in 1880 and in 1910 decided to
invest in Herold China and Pottery Company. This proved to be
a crucial decision. In the 1920s, with Prohibition in effect, it was
the sale of ceramics and, of all things, malted milk that kept
Coors solvent!

Back to aluminum oxide, it’s an extremely important material.
Aluminum is a very reactive element and, without the tough, thin
film of aluminum oxide that forms on the surface of aluminum,
items such as aluminum foil and pots and pans wouldn’t exist.
Although aluminum oxide has a density of 4, the body armor
developed for ceramic breast and back plates still weighs some
30 pounds. This puts a severe limitation on a soldier’s mobility
and the C&EN article suggests it is only good for sentry duty.

Scientists have come up with a lighter alternative in the form of
the compound boron carbide. This compound of boron and
carbon has a density of only 2.5 and today’s soldier is likely to
have a jacket with the lighter boron carbide body armor. This
also will be better contoured to the wearer than the older rigid
aluminum oxide-based armor. Panels of boron carbide are also
used to fortify seats, walls and floors of attack helicopters and
other military aircraft.

Actually, a suit of body armor is not just a fitted chunk of
ceramic. The ceramic will shatter the incoming projectile into
bits and pieces but it won’t do a good job of absorbing the energy
of the impact. You need a backing of some sort. The backing
typically is a composite of some sort that employs fibers that
resist the impact. These fibers capture the shrapnel from the
encounter of the bullet with the ceramic. DuPont’s Kevlar is one
such material. The Kevlar is effective thanks to in part its
tendency to line up in orderly arrays of tough fibers bundles.

The ideal body armor would stop all incoming projectiles before
reaching the body of the warrior. Boron carbide does a good job
of standing up to low energy projectiles such as bullets from a
handgun. However, it’s not that good when it comes to higher-
energy incoming objects. This puzzled researchers because the
properties of boron carbide indicated that it should perform much
better. Workers at Johns Hopkins and the Army Research
Laboratory’s Aberdeen Proving Ground found the answer,
published in the March 7 issue of Science.

Mingwei Chen, lead author of the Science article, and his
colleagues looked at fragments of boron carbide recovered from
an Army test facility with a high-resolution electron microscope.
The boron carbide in the body armor is a crystalline material.
What they found was that the impact of the high-energy
projectile hitting the crystalline boron carbide, resulted in the
presence of some very narrow bands of a glassy form of boron
carbide. These bands were only a couple of nanometers wide.
They determined that the structure in these tiny bands was
disordered, in contrast to the ordered arrangement of atoms in the
original crystalline boron carbide. This transformation from
crystalline to glassy material has been seen in other materials but
apparently not in any material as hard as boron carbide.

The glassy boron carbide is weaker than the crystalline form. As
a result, the material in the body armor fractures along the
narrow bands of glassy material. The challenge now is for the
researchers to come up with some new approaches, perhaps
changing the chemistry or additives or grain structure of the
boron nitride to up the resistance of the material to higher energy
impacts without forming glassy boron carbide.

Wouldn’t it be great if all this work on protecting our soldiers
proved unnecessary because everyone decided to live in peace?
The way things are going in the world today, I fear it’s more
likely that all of us will need to wear body armor in the future.
In the meantime, we can savor moments like that memorable
closing shot of Shaun Micheel in the PGA.

Allen F. Bortrum