Fundamental interactions between carbon nanotubes

<p><strong>Fundamental interactions between carbon nanotubes</strong></p> <p>Junjie Chen</p> <p>Department of Energy and Power Engineering, School of Mechanical and Power Engineering, Henan Polytechnic University, 2000 Century Avenue, Jiaozuo, Henan, 454000, P.R. China</p> <p>Contributor: Junjie Chen, ORCID: 0000-0002-5022-6863, E-mail address: koncjj@gmail.com</p> <p>&nbsp;</p> <p>Elemental carbon exists in several forms, each of which has its own physical characteristics. Two of its well-defined forms, diamond and graphite, are crystalline in structure, but they differ in physical properties because the arrangements of the atoms in their structures are dissimilar. A third form, called fullerene, consists of a variety of molecules composed entirely of carbon. Spheroidal, closed-cage fullerenes are called buckerminsterfullerenes, or buckyballs, and cylindrical fullerenes are called nanotubes. A fourth form, called Q-carbon, is crystalline and magnetic. Yet another form, called amorphous carbon, has no crystalline structure. Other forms, such as carbon black, charcoal, lampblack, coal, and coke, are sometimes called amorphous, but X-ray examination has revealed that these substances do possess a low degree of crystallinity. Diamond and graphite occur naturally on Earth, and they also can be produced synthetically; they are chemically inert but do combine with oxygen at high temperatures, just as amorphous carbon does. Fullerene was serendipitously discovered in 1985 as a synthetic product in the course of laboratory experiments to simulate the chemistry in the atmosphere of giant stars. It was later found to occur naturally in tiny amounts on Earth and in meteorites. Q-carbon is also synthetic, but scientists have speculated that it could form within the hot environments of some planetary cores. Pure diamond is the hardest naturally occurring substance known and is a poor conductor of electricity. Graphite, on the other hand, is a soft slippery solid that is a good conductor of both heat and electricity. Carbon as diamond is the most expensive and brilliant of all the natural gemstones and the hardest of the naturally occurring abrasives. Molecules of fullerene show promise in a range of applications, including high-tensile-strength materials, unique electronic and energy-storage devices, and safe encapsulation of flammable gases, such as hydrogen. Q-carbon, which is created by rapidly cooling a sample of elemental carbon whose temperature has been raised to 4,000 degrees kelvin, is harder than diamond, and it can be used to manufacture diamond structures (such as diamond films and microneedles) within its matrix. Elemental carbon is nontoxic. Each of the amorphous forms of carbon has its own specific character, and, hence, each has its own particular applications. All are products of oxidation and other forms of decomposition of organic compounds. Carbon, either elemental or combined, is usually determined quantitatively by conversion to carbon dioxide gas, which can then be absorbed by other chemicals to give either a weighable product or a solution with acidic properties that can be titrated. When an element exists in more than one crystalline form, those forms are called allotropes; the two most common allotropes of carbon are diamond and graphite. The crystal structure of diamond is an infinite three-dimensional array of carbon atoms, each of which forms a structure in which each of the bonds makes equal angles with its neighbors. If the ends of the bonds are connected, the structure is that of a tetrahedron, a three-sided pyramid of four faces. Every carbon atom is covalently bonded at the four corners of the tetrahedron to four other carbon atoms. The space lattice of the diamond can be visualized as carbon atoms in puckered hexagonal rings that lie roughly in one plane, the natural cleavage plane of the crystal; and these sheets of hexagonal, puckered rings are stacked in such a way that the atoms in every fourth layer lie in the same position as those in the first layer. The extreme hardness, the high sublimation temperature, the presumed extremely high melting point, and the reduced chemical reactivity and insulating properties are all reasonable consequences of the crystal structure.</p>