Introduction

The field of nanotechnology centers on analyzing and manipulating particles less than 100 nanometers in size in an effort to use their unique physical and/or chemical properties to develop new products or solve problems. A nanometer is one-billionth of a meter, approximately the size of a single molecule. Due to their size, nanomaterials hold the potential to be safely introduced into sensitive environments such as the human body or electrical circuits (Cook, 2005).

Carbon nanotubes came into focus about 20 years ago and the uncommon properties they exhibit could one day be harnessed to create a wide range of heat-stable and nearly indestructible materials that would be invaluable to various fields of study, particularly computer and electronic engineering. They have been found to mimic the role of silicon in electrical circuits, but on a much smaller scale and in environments where silicon or other semiconductors would fail. Evidence shows that carbon nanotubes could be used to create faster, energy-saving circuits as well as touch-screen displays. Electronic engineers are constantly seeking to make their products smaller yet more robust, and mastering the use of carbon nanotubes could certainly be the key to success, but because of their structure and the consequent limitations on their manipulation, novel research methods are required to make handling of these particles easier as well as cost-efficient. (Collins & Avouri, 2000). This paper will highlight a brief history of carbon nanotubes, how they are made, what they can be used for, and the restrictions on their production.

Background

Carbon nanotubes are networks of pure carbon atoms arranged in hexagons connected to each other in repeating patterns to form a long hollow tube, similar in appearance to a seamless roll of chicken wire (Collins & Avouri, 2000). In 1991 at the NEC Fundamental Research Laboratory in Tsukuba, Japan, Sumio IIjima stumbled across the presence carbon nanotubes while peering through an electron microscope and wrote a report which drew much attention to these microscopic entities, though they had been quietly discovered decades earlier (Anissimov, 2010). The observed incredibly thin threads were composed chiefly of carbon atoms arranged in perfectly symmetrical crystals. The threads were later named multi-walled tubes, as it was found that each tube was actually constructed of several tubes layered one within another. In 1993, Iijuma and Donald Bethune of IBM synthesized single-layered carbon nanotubes which were about one nanometer in diameter and thousands of nanometers in length. At such dimensions it would seem as if these structures would be fragile, however carbon-carbon bonds are strong enough to make nanotubes stable; such bonds contribute to the strength and rigidity of diamonds (Collins & Avouri, 2000).

Potential Benefits

It has been found that carbon nanotubes are among the world’s strongest fibers, being ounce-for-ounce 117 times stronger than steel and 30 times stronger than Kevlar. Conversely, these tubes have a high elasticity and can bend much like toffee before breaking (American Chemical Society, 2010). Such strength and resilience is remarkable and could be exploited to synthesize a wide variety of new materials, but adding to those properties is the electrical conductivity of these tubes; single-walled nanotubes are exceptional conductors. These characteristics combined make nanotubes ideal building materials for LCDs and other flexible displays among other things (Anissimov, 2010; Opatkiewicz, LeMieux, & Bao, 2010), and nanotubes could one day replace the silicon transistors on computers. Though silicon is a cost-effective material, carbon nanotubes could be used to make smaller and faster components that would use less energy; in an age where Green technology is a major focus in our society, this would be advantageous. Continuous circuits of nanotubes would need to be created in order to make them of greater use in computers and other applications, and this issue has yet to be resolved by scientists (University of Gothenburg, 2010).

Potential Limitations

Though generating a working circuit of single-walled nanotubes would revolutionize electronics, it has proven difficult to isolate a single type of nanotube from a synthesized network (Opatkiewicz, LeMieux, & Bao, 2010). Carbon nanotubes tend to grow randomly in no particular direction or position, and the molecular orientation of carbon atoms in a tube has a significant impact on the way it functions; the molecular orientation indirectly determines the properties of the nanotube, whether it will be metallic in character or a semiconductor. Scientist Johannes Svensson from the University of Gothenburg has found that applying an electrical field can guide the tubes as they grow, but ultimately it is difficult to control the type of tube that is grown (University of Gothenburg, 2010).

Nanotubes are generally grown in bulk with the aid of a metal catalyst, and the type of tube that arises also depends on the metal catalyst used to grow it. For example, a nickel catalyst used to generate nanotubes for use as semiconductors would create a mix of semiconducting and metallic tubes; two-thirds of the product would be the desired semiconducting material, but one-third of the tubes would be metallic in character. The metallic tubes could be used to conduct electricity much like any metal wire, while the semiconducting tubes could be used as transistors, but separating the mixture of nanotubes would be costly and could damage them. Using a mixed-metal catalyst (such as iron and nickel) could generate purer products, but the identity of the catalyst affects the diameter of the tube (University of Gothenburg, 2010; Case Western Reserve University, 2009) and it remains virtually impossible to manufacture a high yield of unmixed products (Opatkiewicz, LeMieux, & Bao, 2010).

Future Research

In order to use nanotubes in new materials, a reproducible method must be created to generate high quantities of 100% pure nanotubes or functional mixed networks. Several reasonable purification techniques have been utilized by researchers, but the challenge of mass production remains. One group of researchers has found that in a network of mixed nanotubes, the range of metallic and semiconducting properties could balance out to create a functional circuit. A network would result in decreased conductivity of individual nanotubes, but collectively it would carry a greater load due to the increased density of tubes. In addition, it is more feasible to mass produce networks that could be used in electronic displays or for other applications (Opatkiewicz, LeMieux, & Bao, 2010). Still, researchers must work to develop standardized production methods before the widespread use of nanotubes can occur.

Manufacturing the catalysts that are used to create nanotubes often poses a health risk to the researchers who synthesize them, and the catalysts are not very selective in the type of nanotube that is made, so further studies are required to overcome this problem. The cost of creating nanotubes is expected to decline in coming years as production increases, but current progress is slowed by financial hurdles (Khanal, Surampalli, Zhang, Kao, Tyagi, & Lamsal, 2010).

Conclusion

Once researchers can create standardized production methods tailored to the type of nanotube and its purpose, their use in computers and other devices can become widespread.

References

American Chemical Society. (2010, September 15). Carbon nanotubes twice as strong as once thought. Retrieved October 2010, from Physorg.com: http://www.physorg.com/news203774138.html

This article was originally published on the American Chemical Society's website, so although phsyorg.com may not be considered a reputable source in itself, as it is maintained by users, the article in question can be a trusted source of information. It parallels the article Faster Computers with Nanotechnology in that it discusses the strength of nanotubes, but this article is much shorter. Its brevity and use of commonplace language makes it comprehensible to anyone with a basic knowledge of carbon nanotubes.

Anissimov, M. (2010, September 8). What are Some Uses for Carbon Nanotubes? Retrieved October 2010, from WiseGeek: http://www.wisegeek.com/what-are-some-uses-for-carbon-nanotubes.htm

Though this article was obtained from a website that seems credible due to its name, this website would not typically be considered a reputable source. It is run by users, not information about the author is given, and it does not contain bibliographical information for the claims that are made, but this particular article may be considered accurate in its discussion of the uses of carbon nanotubes; it provides the same background information on nanotubes that can be found in other articles on this list, verifying the accuracy of the webpage, but it more clearly states the uses for nanotubes. The article translates information found in scholarly articles into layman’s terms, making it comprehensible for most individuals.

Case Western Reserve University. (2009, September 21). A Recipe For Controlling Carbon Nanotubes. Retrieved October 2010, from ScienceDaily: http://www.sciencedaily.com/releases/2009/09/090920204453.htm

ScienceDaily does not appear to be a trustworthy source judging by the amount of advertisements littering their web pages, but they claim to review all articles before they are published to ensure their accuracy. The information derived from the article in question can be found in other articles, giving credibility to this source. This article was derived from Case Western Reserve University, further confirming that it can be trusted. The article comments on the effect of catalyst identity in determining the type of nanotube that results, a fact that is noted in other articles on this list. There is no author or editor given, but bibliographical information regarding the source of the article is provided.

Collins, P. G., & Avouri, P. (2000). Nanotubes for Electronics. Scientific American , 62-70.

This article comes directly from a credible source and provides information about the authors and where to go for further information on the topic of nanotubes. The authors have degrees from accredited universities and are scientists who work for IBM, giving them credibility. The article is written in a way that could be understood by individuals knowledgeable in chemistry and physics, making it difficult for many people who know nothing of quantum mechanics or chemistry. Many figures and tables are found throughout the article that adequately summarize and support the text and clarify the information given. Almost anyone who would have a subscription to Scientific American could probably understand the article, but the tables make it comprehensible for most of the general population.

Cook, K. A. (2005). Societal Impact of Nanotechnology. Retrieved October 2010, from Discover Nano: http://www.discovernano.northwestern.edu/affect/societalimpact

This website provides an overview of nanoscience, its applications, and impacts on society. Overall the website is not entirely relevant to the topic of carbon nanotubes, but it contains enough information on nanomaterials and their uses to be significant in some aspects. It gives a good definition for carbon nanotubes that is a condensed version of definitions that are found in many other sources on this list. The website's author can be considered a reputable source for information as she is a university professor. Though no bibliographical information is provided, much of the information found on the website can be found in other sources.

Khanal, S. K., Surampalli, R. Y., Zhang, T. C., Kao, C., Tyagi, R., & Lamsal, B. P. (2010). In Bioenergy and Biofuel from Biowastes and Biomass (p. 490). Reston: American Society of Civil Engineers.

This book has little to do with actual carbon nanotubes in electronics, but a small amount of the information provided was relevant to this paper for the purpose of analyzing the limitations on nanotube production. The limitations noted in this book are alluded to in other articles, but this book gives a clearer definition of the limitations. The authors all have degrees and awards, so their credibility is evidenced.

Nanotech Quote Collection. (n.d.). Retrieved October 2010, from Newbridge Institutional Research: http://www.newbridgereports.com/quotes.html

NewbridgeReports.com is a website that tracks nanotechnology companies in the Stock Market. The site is difficult to navigate and not all links work, but because the site is mainly intended to inform investors and it provides no actual scientific information its credibility is not an issue. The person the quote is derived from does exist, so the site does suit its purpose in this paper.

Opatkiewicz, J., LeMieux, M. C., & Bao, Z. (2010). Nanotubes on Display: How Carbon Nanotubes Can be Integrated into Electronic Displays. ACS Nano , 2975-2978.

This article is unquestionably credible, as it was published by the American Chemical Society. The authors can therefore be trusted, so long as they did not fabricate their findings. It supports information found in the WiseGeek.com and ScienceDaily articles, adding to their credibility. The WiseGeek and ScienceDaily articles clarified what was reported in this article, as this article seems to be written for individuals studying nanochemistry.

University of Gothenburg. (2010, June 1). Faster Computers With Nanotechnology. Retrieved October 4, 2010, from ScienceDaily: http://www.sciencedaily.com/releases/2010/05/100531082857.htm

This article contains appropriate quotations and bibliographical information, so despite the lack of professionalism of the website, the article can be considered credible even though the website is owned by Reuters.

Course: IT103

Tuesday, November 9, 2010

This Nanotube Video is easier to access

Tuesday, October 5, 2010

CarbonNanotubeVideo

CarbonNanotubes

References

Tuesday, September 28, 2010

Nanochemistry