The HKUST Edge
6
HKUST Alumni News 2014
The development of a new aluminium composite by a team from the Department of Civil
and Environmental Engineering is set to change the face – in some cases, literally – of the
building industry and herald a greener future.
Building Towards
a Better Future
C
heaper, lighter and stronger… these are the irresistible
properties of a new aluminium composite developed by a
team led by Professor Ben YB Chan, Associate Director, Center for
Engineering Education Innovation in the Department of Civil and
Environmental Engineering (CIVL). The new material, called Fiber
Reinforced Aluminium (FRA), has been developed with support
from UC RUSAL, a leading global aluminium producer from Russia.
“FRA is a mixture of carbon fiber and aluminium. It is stronger
than existing aluminium, cheaper and lighter than steel, and can be
used with insulation panels to produce a Smart-building envelope
system that effectively reduces indoor temperature fluctuation, as
well as halving labor costs and construction times compared with
steel and concrete systems,” says Professor Chan, who is himself
an alumnus of HKUST.
Carbon fiber is extremely light and strong, hence its extensive
use in the automobile and aviation industries; while aluminium is
also light but is not strong. Professor Chan explains that layers
of the two materials can be stuck together, but the results can
be disappointing because the carbon fiber is too smooth to stick
securely, while the glue deteriorates.
His team sought out a different approach. “We have changed
the composition of the carbon fiber using nano technology,” he
says. “We created a ‘fishbone-shaped’ carbon fiber using chemical
vapor deposition (CVD) technique; metal particles can be bonded to
the sharp ends. The result is a chain of metal particles that can stick
to other metal particles.” This is mixed with aluminium particles and
heated up to 700°C, increased to 1,000°C, then cooled quickly so
the substance melts. The result is FRA, which has a strength of at
least 100GPa, but generally 130GPa, compared with 65-75GPa for
traditional aluminium alloy.
FRA is made using recycled industrial waste, which helps
reduce the cost of manufacture, as does the “fishbone chain”
shape. “This is not as precise a shape as the traditional carbon
nanotube,” says Professor Chan. FRA costs US$50/kg compared
with US$2000/kg for carbon nanotube.
Thanks to its relative lightness, strength, corrosion resistance
and cost, the applications for FRA are numerous, and include
electronic products, automobiles and aircraft, as well as
construction materials. Professor Chan says, “We are happy with
the product but we want to look at long-term issues, such as
fatigue and corrosive environments, and want to perform a full set
of tests.”
As a part of the project, the CIVL team is using the FRA to
produce a greener building envelope system. Professor Chan
explains that current façade systems, designed to reduce heat
loss, control moisture, prevent leakage and protect the people
inside, encounter many problems, and the energy efficiency
achieved is only 20% of that anticipated.
A lot of work has gone into improving building
envelope systems, he notes. Some of it has
focused on “phase-change material”,
which is a substance that, when
it melts and solidifies at certain
temperatures, stores or releases
energy. “Can we design a
building that saves energy by
absorbing energy when the ambient
temperature is high and releases energy when the
temperature is low? Ten years ago, there was a lot
of research into this, but it was not very successful,
because scientists could not find an efficient material
that would melt at 20°C,” says Professor Chan.
“However, our team is looking at this from a different
perspective. We investigated the time lag that occurs
when water changes to ice and vice versa at 0°C. By
extending that period of time, by using phase-change to
reduce the maximum temperature, we can achieve 60%
energy saving.”
Their research has resulted in the development of light-
weight panels consisting of layers of FRA, PCM, gypsum
board and polyisocyanurate foam that exceed the basic
requirements of building codes in Hong Kong, Shanghai,
Beijing and Moscow. “We have developed the prototype
and are testing the mechanical properties and energy
