Goldilocks Mission | Carbon Nanotubes: Notable Developments of 2009

Carbon Nanotubes: Notable Developments of 2009

January 10, 2010 Space Age Technology by Goldilocks Mission Blog

Ever since scientists discovered the incredulous tensile strength of carbon nanotubes and its unique properties, the wonder material has found numerous applications in various technologies but has yet to fulfill its part in what made it famous the first time, the space elevator. Much research has been done in the last two decades and still continuing, for carbon nanotubes (CNT) do hold a lot of promise in its home niche, nanoscience and nanotechnology. It may seem a bit ironic then for it to be the main component to what may be the world's gigantic superstructure, one that pierces through the stratosphere and even go beyond where most satellites orbit the earth. For all its worth, carbon nanotubes are still the best uncontested theoretical candidates for constructing the space elevator cable.

It's been called a lot of things like the “ribbon” and “tether” but the basic design lies on the simple fact that the cable must be strong enough to support its own weight and withstand tensile forces that would break and shatter even the strongest steel. To illustrate that fact, a carbon nanotube “ribbon” which weighs a sixth that of steel of the same dimension is significantly stronger one hundred times over. This property is in itself a perfect testament to the material's incredible attributes which make it a fitting component in the space elevator cable.

Year 2009 marks the 18th year since carbon nanotubes were first disovered. Let's review some of the most notable research done in the field of carbon nanotubes science in the past year.

In January last year, researchers in the University of Nebraska were able to develop a method that could accurately control the production of carbon nanotube lengths and even dictate the positions where the tubes would form. This is especially true for the laser-assisted chemical vapor deposition, a common process in the production of CNT which initially allowed free but uncontrolled formation on the substrates and electrodes used. Using optical field effects resulting from the interaction among the laser and the choice electrodes, the researchers were able to gain control of the CNT formation.

In April, Stanford University researchers were able to create “graphene nanoribbons” by tearing multi-walled CNTs, multi-layered concentric nanotube. This is yet another way of getting fine control in CNT formation. Carbon nanotubes are usually produced in lumps or films deposited on a substrate. But if we are to construct long ribbons of carbon nanotubes with uniform diameter, a method must soon be developed to allow accurate control in CNT formation. These promising methods of CNT production control would allow us to do just that.

Most carbon nanotube formations are held together by Van der Waals forces, which are considerably weaker than metallic or ionic bonding or even covalent bonding forces. This is the primary reason why scientists could not produce continuous “ribbons” of CNT but instead create bundles or chains of CNT attached by Van der Waals forces lowering its overall effective tensile strength. To resolve this disadvantage, scientists attempt to bond CNT with other polymers. Rice University researchers in April successfully made use of functional covalent bonding with polyethylene and other polymers. However, the process only serves to strengthen the polymer and not the CNT. Still, the technique promises future applications in the construction of other lightweight but strong parts of the space elevator.

Yet another breakthrough in controlling the formation of CNTs in substrates came in the form of flexible electronics. Boston Northeastern University researchers in July were able to use fluidic assembly of CNTs on flexible polymeric substrates to be applied in electronic circuits. This may be used in parts of the space elevator where electronics are needed in places that must endure extreme stress. The flexibility of these electronic circuits assure us that they will function even when the structure is subjected to intense strain as in the case of a moving mobile platform at sea.

One of the most notable breakthroughs in 2009 came in August when MIT researchers found out that carbon nanotubes could be produced without using popular metallic catalysts and instead use zirconium oxides. Initially, CNT formation in metals prevented scientists from further studying the actual processes involved CNT growth since the tool used is infrared spectroscopy and the metals greatly interfere with their observations. The discovery itself opens up a new way of producing CNTs in an easier process that would promise bulk quantities.

In September, further research conducted at Deakin University used electrospinning methods to strengthen polymer nanofibers. The process allows the polymers to form around CNTs which strengthens the nanofibers. This may be used to create continuous CNT “ropes” or “tethers”. However, the overall strength of the fiber will still depend on the polymers that wrap around the CNTs.

November marked the end of a long nine-year research program conducted by Rice University scientists that aimed to create a breakthrough in large scale production of CNT fiber. The process uses acidic solution that dissolves carbon nanotubes without modifying them and allow realignment of the nanotubes which can then be spun into continuous filaments as thin as the human hair. CNTs produced in most processes that involved mere suspension result to different sizes, diameters and length. The method allows easy manipulation of the CNT solution and allows extraction of carbon nanotubes that have uniform size and length and is an essential requirement for building the space elevator cable.

A remarkable discovery which may change the way carbon nanotubes are created took place in December when Argonne National Laboratory researchers were able to convert plastic sacks into CNTs! It was simple and cheap method that involved “cooking” the plastics at 700 degrees Celsius to break it down while using cobalt acetate as a catalyst in the formation of carbon nanotubes on the cobalt particles. It also serves to answer for one of the environment's greatest problems, non-biodegradable plastic.

This wonder material possesses a lot of potential in many fields such as medicine, nanocircuitry, and particularly nanomaterial science. The past year alone has seen a lot of developments in the synthesis of carbon nanotubes. It may not be a long wait until the technology arrives to allow the construction of CNT tethers that may be used to build the space elevator cable. When that day comes the space elevator will no longer be a sci-fi fan's fictional terminology, but an engineering marvel which will be the first time in the history of humanity that will allow unlimited access to space.

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Tags: space elevator, carbon nanotubes, Updates, space technology

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Carbon Nanotubes: Notable Developments of 2009