Once the most promising of all nanomaterials, carbon nanotubes (CNTs) are in danger of being usurped in conductive applications by graphene and in composites by nanocellulose. However, CNTs are likely to remain competitive against these materials, and potentially complementary. Transparent conductors, battery additives and transistors represent the most promising markets for CNTs. They are widely viewed as viable candidates as alternatives to ITO in transparent conductors and the main candidate to replace silicon in transistors.
CNTs and graphene are the strongest, lightest and most conductive fibers known to man, with a performance-per-weight greater than any other material.
• Steel: two hundred times stronger and five times the elasticity
• Copper: fives time the electrical conductivity, fifteen times the thermal conductivity and one thousand times the current capacity of cop
• Aluminium: half the density of aluminum.
Bulk CNT powders have already been incorporated in diverse commercial products ranging from rechargeable batteries, automotive parts, and sporting goods to boat hulls and water filters.
They have been used as fillers in supercapacitors and battery electrodes, electronics and lightweight high-strength composites at a scale of hundreds of tons. Limited-volume applications are as scanning probe tips, drug delivery research, thermal management and biosensors (mainly for R& D purposes).
Advances in CNT synthesis, purification and chemical modification are also enabling integration of CNTs in thin-film electronics and large-area coatings. CNT yarns and sheets have demonstrated promising performance improvements for applications such as supercapacitors, actuators, and lightweight electromagnetic shields.
Over the next few years CNTs will find wider application in conducting films, lithium-ion batteries (LIB), supercapacitor electrodes, fire-retardant materials, field emission devices, chemical sensors and biosensors, hydrogen storage, adhesives and printing inks, to varying degrees of market penetration.
An interesting development is nanotube-graphene hybrid materials that could have important implications for composites and conductive additives. Long-term applications may be witnessed in power transmission, photovoltaics and drug delivery. Main demand for CNTs by 2020, by market, and in order of size is as follows:
1. Electrically conductive polymer composites and films
2. Li-ion battery electrode additives
3. Polymer reinforcement
4. Fire-retardant composites and coatings
5. Metal matrix composites.
Production capacities for CNTs have been scaled up considerably over the last few years and currently exceed several thousand tons per year, although this current significantly exceeds demand. Companies can now produce hundreds of tons of nanotubes per year. Capacity in 2011 was approximately 10, 000 tons.
Prices of Multi-walled Nanotubes (MWNT) now range from $45-100 per kg, depending on quality, with Chinese manufacturers offering MWNTs at lower prices. Showa Denko K.K., Nanocyl, CNano Technology Ltd., Arkema Inc. and Hyperion Catalysis are the leading producers. Bayer ended CNT production in 2013.
Single-walled Nanotubes (SWNT) are currently too expensive for widespread application but are expected to make a significant impact in electronics applications by 2020, and price has decreased as production capabilities have improved. SWNTs are also promising candidates in anti-bacterial and medical applications. The current capacity for the production of MWNTs far exceeds that of SWNTs. SWNTs are much more difficult to manufacture than MWNTs, and there is not yet a distinct large-scale market for SWNTs, which is needed to drive down the production cost although this is likely to change in the consumer electronics sector within the next 5-10 years.
Their utilization as replacement materials for indium tin oxide (ITO) and silicon in electronics applications are driving increased production of SWNTs. Applications in transistors require precise control over CNT diameter and conductivity, and are much further from commercial realization than for ITO replacement in displays, although IBM has forecast that they will start to make a market impact from 2020 .
Annual production volume of SWNTs to 2014 was approximately 500kg-1 ton per annum. However, this will increase significantly after the announcement in May 2014 by OCSiAl that they have developed a technology for commercial-scale production of SWNTs, with a capacity of 10 tons per annum. Price is $2000 per kg, a significant reduction on widely available prices.
Electronics and displays
CNT are already used for electromagnetic shielding (EMI) coatings and composites in electronics and aerospace applications. The EMI/RFI technology market has been estimated to be worth more than $5 billion annually, with the conductive coatings market accounting for $1.5 billion-$2 billion, representing a significant market opportunity for CNTs. The rise in market demand for touchscreens, displays and photovoltaics is increasing the need for non-indium based transparent conductors. Furthermore, next generation flexible touchscreens such as those demonstrated by Samsung and Nokia, require a non-brittle material. Indium tin oxide (ITO) replacement is a key theme among product development. CNTs and graphene may allow for the replacement of ITO, which is in short supply, expensive and limited in its use with flexible substrates. The addressable ITO replacement market has been estimated to be worth $1.5-$2 billion annually.
Companies are mainly targetting the small/medium size flat panel display market. This is estimated to be worth $130 billion per annum and will reach $150 billion per annum in the next few years, driven by the increasing consumer demand for portable display-based electronics such as smartphones, cameras, iPads, netbooks, and similar devices. For such applications, low-cost, high image quality, low-power consumption display screens are in high demand.
IBM views CNTs as an excellent candidate for replacement of CMOS silicon as they are “three to ten times better than silicon tech on a [process]node-to-node basis”. With regards to graphene, the company does not believe manufacturing large amounts is a problem. However, the company do not currently view graphene as a viable candidate for replacing silicon and CMOS. The company believe its application is more likely in areas such as wireless communications. During the past few years, development of SWNTs for electronics applications has progressed from proof-of-concept prototyping in academia to technology development in industry with emphasis on manufacturability and integration issues.
Electric vehicles and lithium-ion batteries
Electric vehicles, and enabling lithium-battery (LIB) technology, will become a larger and larger market-with estimates of CAGR of over 20% through to 2025. CNTs and graphene are prime candidates for improving the energy density of current lithium-ion technology, potentially paving the way to a widespread adoption of electric vehicles. Transportation and communication will increasingly rely on LIBs and SWNTs are under commercial development in this space. Price is still a significant obstacle but the increase in their usage in these sectors over the next few years will drive down costs and allow for widespread adoption.
Competition from silicon in semiconductors and sensors as well as carbon fiber (composites) is significant. Other competing technologies in transparent conductive films include ITO, silver nanowires, graphene, PEDOT, micro fine wire, and metal mesh, as well as other 2D materials such as boron nitride, molybdenum disulfide, tungsten disulfide and germanane.
Due to graphene’s comparable or better properties and lower production cost, CNTs are likely to be replaced in applications which do not significantly benefit from nanotubes’ 1-D nature. It remains to be seen how graphene powders will compete with incumbent carbon blacks in rubbers and other composites, and where the markets place the trade-offs between price and performance. Yet there can be no question that graphene materials will creep into the carbon black markets, especially for higher performance materials.
Recent industry developments
In April 2014, CurTran LLC announced that it had signed its first contract for LiteWire products with Weatherford International Ltd. Per the agreement, Weatherford will use, sell, and distribute LiteWire, the first commercial scale production of a CNT technology in wire and cable form. According to the CurTran CEO, it is a long-term contract with a forecasted average value of more than $350 million per year. In May 2014, there were a number of announcements regarding new production facilities.
OCSiAl unveiled a breakthrough technology for the production of SWNTs, which enables large scale, commercial production. Estimated production of the SWNTs is 1 ton for the first year, which doubles current global production levels according to different estimates. Potential annual capacity of OCSiAl production is currently 10 tons. This method is easily scalable and capable of producing an unlimited quantity of SWCNTs at a very low cost. Free samples of TUBALL ® can be ordered now and shipped from OCSiAl stockhouses in Europe, Asia and the US. The commercial price for TUBALL ® starts from $2000 per kg.
FGV Cambridge Nanosystems also announced it is planning to produce the world’s first high-grade carbon nanotubes and graphene from by-products of oil palm plantations in Malaysia this year. Capacity will be between 50 and 100 tonnes per annum. Later that month, Fulcrum SP Materials Ltd. announced that its 750 square meter pilot production facility was fully operational.
Applying its technology via standard textile dyeing machines, Fulcrum can now coat 100-metre fabric rolls with its SP1/Carbon nanotube (CNT) technology combining individually dispersed, single molecular layer of carbon nanotubes. The fabrics include woven and unwoven standard carbon fiber, glass-fiber, aramid and high-density polypropylene fiber rolls, as well as yarn and tow.
Further information on the market for Carbon Nanotubes is available in the report “The Global Market for Carbon Nanotubes to 2024”, published by Future Markets, Inc., July 2014 (http://www.futuremarketsinc.com/index.php/nanoreports-63/nanotubes).