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The titanium revolution is here, and
it's going to change everything from cutlery to cars, says
Steve Hill. Are you ready for a stronger, lighter, shinier
world?
TITANIUM
is fantastic stuff-it's lighter than steel yet strong and
tough enough to survive the extremes of space or the corrosive
salts and pressures of the deep ocean with hardly a blemish.
In fact, just about the only drawback with the material is its
price tag. Titanium is
currently six times as expensive as stainless steel. But this
looks set to change, with the discovery of a new way to
extract titanium metal that
requires little more than black sand and electricity. It's a
far cry from the usual method, which is slow, expensive and
consumes tonnes of corrosive chemicals. Best of all, the
process promises to slash the price of the metal by up to
three-quarters.
Put this new technology to work and titanium
could infiltrate our lives in all kinds of ways. Manufacturers
could replace steel, aluminium and even some plastics,
creating a new generation of lightweight, high-speed ships and
fuel-efficient engines. With titanium
beams, cables and tie rods, engineers could stretch
skyscrapers and bridges to new extremes. Cars built with titanium
parts and bodies would never rust.
The new process also promises exotic titanium
alloys and shape-memory metals, and we may even see entirely
new materials that can't be made by conventional techniques.
"This is the century of titanium,"
says Rod Beddows, director of British Titanium,
a company set up to exploit this new technology.
Like many of the best discoveries, this one
was made entirely by accident. Derek Fray, head of the
department of materials science and metallurgy at Cambridge,
wasn't even trying to extract titanium.
Together with a couple of colleagues, he was simply attempting
to purify it.
Titanium
usually contains a small amount of dissolved oxygen near its
surface which can weaken the material. So Fray, Tom Farthing
and George Chen decided to try to remove this impurity using
electrolysis. They hoped that current flowing through the titanium
would drag the oxygen ions to the surface of the material
where they could be removed. But the researchers noticed an
unexpected side effect.
The titanium
they were using had a thin layer of oxide on its
surface-something which always forms when the metal is exposed
to air. They noticed that during the electrolysis this oxide
coating was converted back to the pure metal. The discovery
seemed too good to be true, so they tried the trick on
particles of solid titanium
dioxide-the same stuff used to whiten paper and paint.
Unbelievably, the electrolysis converted the oxide to titanium
metal.
The researchers realised they had stumbled
across a completely new way to extract titanium.
The following year Fray sent a confidential report to
Britain's Defence Evaluation and Research Agency, DERA, and
visited DERA metallurgist Malcolm Ward-Close to discuss the
Cambridge results. "I could hardly believe it,"
Ward-Close says. "I got very excited and offered to
develop the technology and scale it up."
Funding for such a speculative idea was
hard to come by. The project remained on hold until James
Hamilton, the chairman of Bushveld Alloys, a South African titanium
exploration company, visited DERA. He offered to fund a pilot
plant in exchange for an exclusive licence, and the team set
up British Titanium. Work
on the pilot plant began soon afterwards.
A few years later and the first production
trials at DERA have finished. The small plant has proved
extremely successful. "It worked like a dream," says
Ward-Close.
The process takes place in an electrolytic
cell. The cathode is connected to a pellet of titanium
dioxide powder, while the anode is made of an inert material
such as carbon. The two electrodes are immersed in a bath of
molten calcium chloride, which acts as the electrolyte. When
the power is switched on, electrons at the cathode decompose
the titanium dioxide into titanium
metal and oxygen ions. The ions flow through the electrolyte
to the anode, where oxygen is released as a gas.
Now British Titanium
plans to build a much larger pilot plant and to move towards
full commercial exploitation of the technology-now named the
FFC Cambridge process after its discoverers.
Light work
Compared to the Kroll process-the method
used at the moment to extract titanium
from its ore-FFC is revolutionary, says Hamilton. The Kroll
process converts titanium
ore into titanium
tetrachloride and then reacts it with liquid magnesium to
produce titanium metal and
magnesium chloride. It is a batch process that is expensive,
labour intensive and relatively slow. "The process takes
several days and produces only a few tonnes of titanium
per reactor vessel," says Harvey Flower, a metallurgist
at Imperial College, London. What's more, mass production is
difficult with the Kroll process. All in all it has some
pretty serious limitations.
On the other hand, Ward-Close estimates
that the FFC process would take less than 24 hours to produce
the same amount of titanium
a Kroll reactor vessel produces in a week. Crucially for
mass-production purposes, FFC could be a continuous process,
churning out slabs of titanium
from one end while the oxide is fed in at the other. It's also
far less polluting than the Kroll process and incredibly
reliable, says Hamilton. DERA is successfully producing
kilogram batches of titanium
metal time and time again.
If the process scales up to an industrial
level as expected, the price of titanium
should fall substantially-perhaps by as much as 75 per cent.
"It will create a new demand for titanium
metal," says Hamilton. In about a decade, he predicts, we
could have a full-scale titanium
revolution.
British Titanium
believes it could eventually increase titanium
usage from its current level of 60,000 tonnes up to 1 million
tonnes per year. There's certainly no shortage of raw
materials. Titanium is the
ninth commonest ore in the Earth's crust.
So where will we see the benefits of the
revolution? Well, there are all its current applications, of
course-titanium is already
used in the aircraft industry and for prosthetic implants such
as hip replacements. Cheaper titanium
would certainly expand the repertoire of materials used in
these areas. Architects, too, like the stuff. Pretty soon,
shimmering titanium
cladding like that on the Guggenheim Museum in Bilbao could be
springing up all over the place. And why not use it
structurally, says Simon Cardwell, a metallurgist at
London-based engineering consultants Arup. Titanium
may not be as stiff as steel, but with its strength and
corrosion resistance, it could help engineers design bigger
and longer-lasting bridges and skyscrapers.
And then there's the motor industry. Car
manufacturers have long had their eyes on titanium
as a substitute for steel, but it has always been too
expensive. "The car industry would like to use titanium
as it is light, strong and highly corrosion resistant,"
says Fray. An engine containing titanium
parts, for example, would be much lighter so you could expect
significantly better fuel consumption than today's engines
offer.
Unfortunately, it's going to be quite some
time before your car's body panels are cast from titanium.
The price of the material would have to fall even further if
it is to replace the kinds of cheap steel currently used in
car bodies. Ward-Close has a solution, however, and he found
it on the beach. "We are looking at using rutile sand,
which is basically black sand," he says. "The better
stuff is about 96 per cent titanium
dioxide." He thinks that the FFC process could turn
rutile sand into a cheap and cheerful titanium
alloy suitable for car body panels.
But it's in alloy production that FFC
really seems to excel. It can produce alloys directly,
including the most widely used one, which contains 6 per cent
aluminium and 4 per cent vanadium. "The Kroll process
cannot do this," Flower says.
This is a major breakthrough. Alloys are
generally much more useful than pure metals because the
proportions can be adjusted to give the mixture much better
properties than the individual metals. And with the FFC
process, alloy production is simplicity itself. "It's
just like making a cake," says Ward-Close. You simply
blend in the alloying additions as oxides, stick them together
and bake the mixture in a kiln. This high-tech cake then forms
the cathode in the FFC process, and the oxides are all
converted into metal. Et voila! The perfect alloy almost every
time.
Better still, the process isn't restricted
to titanium. Fray has
produced zirconium, niobium, iron and chromium from their
oxides, and turned out many of their alloys too. He believes
the process will enable them to make exotic alloys and
compounds that are usually difficult-or impossible-to make.
Things like shape-memory alloys, for example. These are alloys
that change shape when heated or cooled in the right way. Most
can be bent into any shape you want at low temperatures, but
return to their original shape when heated.
Nickel-titanium
is a common shape-memory alloy, but it is hard to produce
because nickel and titanium
have different densities. With the FFC process, says Fray,
nickel-titanium would be
far cheaper. They are also looking at making superconducting
alloys-such as niobium-titanium-and
magnetic materials, which should cost about one-tenth as much
as the same materials made using conventional techniques.
With this array of exotic alloys in the
pipeline, we may even see a new generation of cheap supersonic
aircraft or lightweight, personal mini-helicopters. And thanks
to its corrosion resistance, titanium
is a natural for naval applications-Japan already has a number
of small craft and racing yachts made using titanium.
In a decade or so, you may find yourself at
the quayside, ready to set sail in a gleaming, lightweight titanium
cruise liner. Because the metal is so light, the ship would
sit high in the water as it whisks you across the ocean. If
its titanium-alloy engines
are efficient enough, the ship may even be able to skim over
the water's surface, cutting the journey time to a fraction of
what traditional steel liners can manage.
By the time all these grand designs for titanium
come about, you'll probably be used to it cluttering up your
house as well. "If titanium
overlaps with stainless steel in price, it could take a big
slice of the market," says Ward-Close. This high-tech
metal could end up in lightweight saucepans, washing machines
and cookers-even the kitchen sink. "How about a canteen
of titanium cutlery?"
Flower suggests.
Titanium
may have proved itself in the aerospace industry and on
missions to the ends of the Solar System, but when it finally
makes it into the home, it will face its ultimate test. Could titanium
toys ever be tough enough to survive the temper tantrums of a
three-year-old?
Steve
Hill is Editor of Materials World
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CANADIAN MINING NEWS