Application of Carbon Nanotubes

Application of Carbon Nanotubes I will be examining and discussing carbon nanotubes and the application within industry, I will look at the History and manufacture of carbon nanotubes. I will Examine and discuss their chemical and physical properties and how these properties make them useful in a wide range of applications. The history of carbon nanotubes is not entirely clear even for those in the science therefore giving proper credit to the person that invented the carbon nanotube has been the subject of several high tech debates among the scientific communities. The initial history of nanotubes started in the 1970s. A preparation of the planned carbon filaments was completed by Morinobu Endo who was earning his Ph.D. at the University of Orleans, France. The growth of these carbon filaments were initially thought to be the first carbon nanotubes. However, they failed to meet the measurement requirements for width and thus were deemed, eventually, barrelenes. This was still a highly important development in the history of carbon nanotubes, but it just wasnt the right time to be considered the first recognized invention. Giving the proper credit to who invented carbon nanotubes would not come along for another 20 years. In 1991 the true first invention of nanotube was finally made. It seems as though there was a race between Russian nanotechnologists and Sumio Iijima of IBM. The first observation of the multiwall carbon nanotubes was credited to Iijima. There are some that hold the belief that in the 1950s there was an initial discovery of what could have possibly been seen as the first carbon nanotubes had Roger Bacon had the high powered electron microscope that would have been necessary. He was credited with the first visual impression of the tubes of atoms that roll up and are capped with fullerene molecules by many scientists in the field. Some state that his discovery just wasnt taken very seriously at the time because science did not know how this discovery could impact scientific research. It would be in 1993 that Iijima and Donald Bethune found single walled nanotubes known as buckytubes. This helped the scientific community make more sense out of not only the potential for nanotube research, but the use and existence of fullerenes. With this information, the complete discovery of carbon nanotubes was realized and Iijima and Bethune were ultimately credited with their discovery in their entirety. Russian nanotechnologists were independently discovering the same visual affirmation. They were just a little bit later in their announcement and the potential effect of this discovery. While Roger Bacon might not have been completely aware of the impact his discovery had on the scientific world, he is technically the first scientist to discover these hollow tubes of carbon that are changing lives on a daily basis. Since the initial rediscovery of the nanotubes in 1991, who discovered carbon nanotubes is no longer as important as who can come up with the most practical applications. DefinitionCarbon nanotubes are large molecules of pure carbon that are long and thin and shaped like tubes, about 1-3 nanometres (1 nm = 1 billionth of a meter) in diameter, and hundreds to thousands of nanometres long. A carbon nanotube (CNT) is a miniature cylindrical carbon structure that has hexagonal graphite molecules attached at the edges. Nanotubes look like a powder or black soot, but theyre actually rolled-up sheets of graphene that form hollow strands with walls that are only one atom thick. Nanotubes, which are sometimes called buckytubes, were developed from the Fullerene, a structure that is similar to the geodesic domes. Nanotubes can be characterized by their number of concentric cylinders, cylinder radius and cylinder length. Some nanotubes have a property called chirality, an expression of longitudinal twisting. Multiple nanotubes can be assembled into microscopic mechanical systems called nanomachines. Shapes Although carbon nanotubes are strong, they are not brittle. They can be bent, and when released, they will spring back to their original shape. One type of carbon nanotube has a cylindrical shape with open ends. Another type of nanotube has closed ends, formed by some of the carbon atoms combining into pentagons on the end of the nanotube. Figure 3.2 A carbon nanotube with closed ends Carbon nanotubes can occur as multiple concentric cylinders of carbon atoms, called multi-walled carbon nanotubes (MWCTs). Logically enough, carbon nanotubes that have only one cylinder are called single-walled carbon nanotubes. Three orientations are possible: armchair, zigzag, and chiral. Figure 3.3 The three possible orientations of CNTs Chemical Properties Carbon nanotubes are polymers of pure carbon, and thus possess all of carbons versatility, including the ability to form countless combinations and derivatives. In addition, carbon nanotubes are direct beneficiaries of the rich history and vast body of knowledge associated with carbon chemistry. Consequently, carbon nanotubes can be functionalized in countless ways using a variety of well-understood chemical reactions. In addition, the geometry of a nanotube allows for the formation of novel synthetic structures not possible with other carbon structures. Carbon nanotubes can be derived both covalently, in which other molecules being bonded to the nanotube share an electron with the tube, and non-covalently, in which the other molecule simply adheres to the carbon nanotubes sidewall, providing a nano-scale coating of the carbon nanotube. Because the carbon nanotube sidewalls are electrically polarizable, polar molecules can easily adhere to their surfaces. When molecules adhere even n on-covalently to the carbon nanotube surface, they often cause subtle changes in the electronic structure of the tubes. Such changes can be easily detected, making carbon nanotubes exquisitely sensitive chemical sensors. An important aspect of non-covalent derivatization is the association of surfactants with the carbon nanotube surface, enabling them to be suspended in water. Physical Properties Electrical There has been considerable practical interest in the conductivity of CNTs. CNTs with particular combinations of N and M (structural parameters indicating how much the nanotube is twisted) can be highly conducting, and hence can be said to be metallic. Their conductivity has been shown to be a function of their chirality (degree of twist), as well as their diameter. CNTs can be either metallic or semi-conducting in their electrical behaviour. Conductivity in MWNTs is quite complex. Some types of armchair-structured CNTs appear to conduct better than other metallic CNTs. Furthermore, interwall reactions within MWNTs have been found to redistribute the current over individual tubes non-uniformly. However, there is no change in current across different parts of metallic single-walled CNTs. However, the behaviour of ropes of semi-conducting SWNTs is different, in that the transport current changes abruptly at various positions on the CNTs. The conductivity and resistivity of ropes of SWN Ts has been measured by placing electrodes at different parts of the CNTs. The resistivity of the SWNT ropes was in the order of 10-4 ohm-cm at 27ÂÂ °C. This means that SWNT ropes are the most conductive carbon fibres known. The current density that was possible to achieve was 107 A/cm2, however in theory the SWNT ropes should be able to sustain much higher stable current densities, as high as 1013 A/cm2. It has been reported that individual SWNTs may contain defects. Fortuitously, these defects allow the SWNTs to act as transistors. Likewise, joining CNTs together may form transistor-like devices. A nanotube with a natural junction (where a straight metallic section is joined to a chiral semiconducting section) behaves as a rectifying diode that is, a half-transistor in a single molecule. It has also recently been reported that SWNTs can route electrical signals at high speeds (up to 10 GHz) when used as interconnects on semi-conducting devices. Strength and elasticity The carbon atoms of a single (graphene) sheet of graphite form a planar honeycomb lattice, in which each atom is connected via a strong chemical bond to three neighbouring atoms. Because of these strong bonds, the basal-plane elastic modulus of graphite is one of the largest of any known material. For this reason, CNTs are expected to be the ultimate high-strength fibres. SWNTs are stiffer than steel, and are very resistant to damage from physical forces. Pressing on the tip of a nanotube will cause it to bend, but without damage to the tip. When the force is removed, the tip returns to its original state. This property makes CNTs very useful as probe tips for very high-resolution scanning probe microscopy. Quantifying these effects has been rather difficult, and an exact numerical value has not been agreed upon. Using an atomic force microscope (AFM), the unanchored ends of a freestanding nanotube can be pushed out of their equilibrium position and the force required to push the nan otube can be measured. The current Youngs modulus value of SWNTs is about 1 TeraPascal, but this value has been disputed, and a value as high as 1.8 Tpa has been reported. Other values significantly higher than that have also been reported. The differences probably arise through different experimental measurement techniques. Others have shown theoretically that the Youngs modulus depends on the size and chirality of the SWNTs, ranging from 1.22 Tpa to 1.26 Tpa. They have calculated a value of 1.09 Tpa for a generic nanotube. However, when working with different MWNTs, others have noted that the modulus measurements of MWNTs using AFM techniques do not strongly depend on the diameter. Instead, they argue that the modulus of the MWNTs correlates to the amount of disorder in the nanotube walls. Not surprisingly, when MWNTs break, the outermost layers break first. Thermal Conductivity New research from the University of Pennsylvania indicates that CNTs may be the best heat-conducting material man has ever known. Ultra-small SWNTs have even been shown to exhibit superconductivity below 20oK. Research suggests that these exotic strands, already heralded for their unparalleled strength and unique ability to adopt the electrical properties of either semiconductors or perfect metals, may someday also find applications as miniature heat conduits in a host of devices and materials. The strong in-plane graphitic C-C bonds make them exceptionally strong and stiff against axial strains. The almost zero in-plane thermal expansion but large inter-plane expansion of SWNTs implies strong in-plane coupling and high flexibility against non-axial strains. Many applications of CNTs, such as in nanoscale molecular electronics, sensing and actuating devices, or as reinforcing additive fibres in functional composite materials, have been proposed. Reports of several recent experiments on the preparation and mechanical characterization of CNT-polymer composites have also appeared. These measurements suggest modest enhancements in strength characteristics of CNT-embedded matrixes as compared to bare polymer matrixes. Preliminary experiments and simulation studies on the thermal properties of CNTs show very high thermal conductivity. It is expected, therefore, that nanotube reinforcements in polymeric materials may also significantly improve the thermal and thermo-mechanical properties of the composites.

A Bintel Brief :: essays research papers

A Bintel Brief   Ã‚  Ã‚  Ã‚  Ã‚  A Bintel Brief, the book of letters from the Jewish daily Forward brought to me the realism of life as a Jewish immigrant. The times were rough on them, they used the â€Å"Bintel Brief† to reveal there problems and to get answers. When I started to read the book I was looking for specific answers to some questions. What do the letters reveal about how immigration was a large part a culrutal process that lasted well after Jews and other immigrants arrived in the U.S.? What was the dominant definition of what it meant to be an American at the time that many Jews arrived arrived in the United States? How did the Jews in the book compare? What hopes did many Jewish immigrants have for life in America? Were the expectations met? What else do the letters reveal about the late 19th Century through the 1920s? These questions really give the purpose of the book itself.   Ã‚  Ã‚  Ã‚  Ã‚  The letters of the Bintel Brief reveal that immigration became a cultural process. When the Jewish immigrants came to the U.S. there culture had to be changed to adapt to the Americans. They shaved their beards and ate non-kosher foods, they slowly had to separate themselves from there homeland. They had to blend in with there surroundings to get a job or even to make friends. In one of the letters, a young Jewish woman would go to work each day knowing that she would be harassed when she arrived. One of her fellow co-workers said the all Galician Jews should be dead. With comments like that, I myself would try to hide the fact that I am of different culture. The Jewish people would have to slowly bring back there heritage after they become treated more equally. Another letter about a 18 year old boy, that is a machinist, would get beaten up as if he was a punching bag. He left the job only to receive the same treatment in the other jobs. â€Å"As soon as they fo und out that I was a Jew they began to torment me so that I had to leave the place,† said the boy (64). The letters do reveal that immigration was a cultural process.   Ã‚  Ã‚  Ã‚  Ã‚  What made you an American during the time of the Jewish arrivals? To be an American in those times, meant that you must be born on the American soil.

Animal Farm †Book Report Essay

Animal Farm talks not only about the corruption of rebellion and revolt by its leaders but also how wickedness, indifference, ignorance and greed influence it. It illustrates immoral leadership, a flaw of revolution. It also depicts how ignorance and indifference to problems within a rebellion allows terrible things to happen if a smooth transition to the people’s government is unsuccessful. Old Major, the old boar on the Manor Farm, summons all the animals on the farm to a meeting, where he compares the humans to parasites and teaches the animals a revolutionary song, ‘Beasts of England’. When Major dies three days later, two young pigs, Snowball and Napoleon, assume command and turn his dream into a philosophy. The animals revolt and drive the drunken and irresponsible farmer Mr. Jones from his farm, renaming it â€Å"Animal Farm†. Animal Farm symbolizes Russia under the Communist Party rule. But more generally, Animal Farm stands for any human society- capitalist, socialist, fascist, or communist. It possesses the structure of a nation with a government (the pigs), a police force (the dogs), a working class (all the other animals), along with state holidays and rituals. Its location in the middle of a number of hostile, neighboring farms supports its symbolism as a political system with diplomatic concerns. Overall, Animal Farm was an amazing book with an incredible sense of morality and had several important themes. The author, George Orwell, displayed his theme in an interesting and entertaining way. I learned that one person’s (or pig’s-in this situation) greed and ignorance can lead to disastrous consequences.

Discover the Worlds Smallest Tree

Some people claim that the title Worlds Smallest Tree should go to a tiny plant that grows in the coldest regions of the Northern Hemisphere. Salix herbacea, or dwarf willow, is described by some internet sources as the very smallest tree in the world. It is also known as the least willow or the snowbed willow. Others see the tree as a woody shrub that does not meet the definition of a tree accepted by botanists and foresters. Definition of a Tree The definition of a tree that most tree scholars recognize is a woody plant with a single erect perennial trunk that reaches at least 3 inches in diameter at breast height (DBH)  when mature. That certainly does not fit the dwarf willow, although the plant is a willow family member. Dwarf Willow Dwarf Willow or Salix herbacea is one of the smallest woody plants in the world. It typically grows to only 1 centimeter to 6 centimeters in height and has round, shiny green leaves 1 centimeters to 2 centimeters long and broad. Like all members of genus Salix, dwarf willow has both male and female catkins but on separate plants. The female catkins are red, while the male catkins are yellow. Bonsai If you dont buy into the dwarf willow being a tree, then perhaps the tiny bonsai crossed your mind. While bonsai do, indeed, meet the definition of trees, they are not a species, as they alterations of larger trees, and can be made from different species. A person will take a cutting from a larger tree to make the miniature bonsai, which then must be carefully maintained and watered to keep its structure. Real (Short) Trees So how about a list of actual plants that meet the definition of trees that can mature at less than 10 feet tall? Crape Myrtle: This small tree comes in a variety of sizes. It can be as short as 3 feet when fully grown, making it one of the shortest trees in the world, though some can reach 25 feet. It can grow quite fast, which is why it is vital to keep in mind its mature growth size when choosing a tree. They come in a variety of brilliant colors.   ‘Viridis’ Japanese maple: The Japanese maple grows only 4 feet to 6 feet tall, but spreads out like a bush. Its vivid green leaves turn to gold and crimson in the fall. Weeping redbud: The Weeping redbud usually grows only 4 feet to 6 feet. They have a small trunk but will weep a flowing canopy back to the ground if not pruned. Pygmy date palm: A dwarf palm tree, this species grows 6 feet to 12 feet tall, and can be kept in a container. Native to southeast Asia, it is relatively drought-tolerant, but cant stand temperatures below 26-degrees Fahrenheit. Henry Anise: With its particularly dense evergreen broadleaf, Henry anise usually grows to be between 5 to 8 feet in a pyramid shape. It is known for its brilliant pink flowers and anise-scented leaves. It makes an excellent hedge.  Ã‚  Ã‚   Japanese maple: Japanese maple can grow between 6 to 30 feet tall. It grows one to two feet per year. Native to Eastern Asia and southeast Russia, this plant comes in a variety of vibrant, eye-catching colors, such as red, pink, yellow and orange.     Ã¢â‚¬ËœTwisted Growth’ deodar cedar: This tree grows between 8 to 15 feet tall.  The named comes from the twists in the limbs. The trees also have a droopy appearance. Windmill palm: This tree typically grows 10 feet to 20 feet tall. The tree is native to portions of China, Japan, Myanmar, and India. It has no cold hardiness and is only cultivated in the United States in the extreme southern states and Hawaii or along the West Coast up to Washington and the most extreme southern tip of Alaska. Lollipop crabapple: These trees grow to 10 feet to 15 feet and produce bushy, white flowers. The name comes from the fact that the tree looks like a lollypop with a small trunk like a lollypop stick and a big round bush of branches like the lollypop itself. Blackhaw viburnum: This tree grows 10 feet to 15 feet tall, producing cream-colored flowers in spring and plum-colored leaves in fall. It is native to North America. It produces a fruit that can be made into preserves. Hibiscus syriacus: This tree grows from 8 feet to 10 feet tall, and produces lavender flowers in the spring. It is native to parts of China but has been distributed throughout the world where it has various common names. In the United States, it is known as Rose of Sharon.