Results and Discussion
3.1 Hydrogen adsorption in single Al atom decorated (8,0) CNT
Single walled carbon nanotube (CNT) with a chirality of (8,0) has been considered for the study. A large supercell with two units along c-axis has been used and this is essential to minimize the adatom-adatom interaction. The size of the triclinic supercell used is 28.83Å×28.83Å×8.52Å with α=β=90° and γ= 120°. The average C-C bond lengths in the CNT supercell vary from 1.41 to 1.44 Å. The optimized structure of (8,0) CNT has a diameter of 6.20 Å [49].
Initially the (8,0) CNT decorated with single Al atom has been investigated to understand the mechanism of hydrogen adsorption. Among the three possible sites for the decoration in (8,0) CNT – top site (T), bridge site (B) and hollow or hexagon site (H), the Al is found to be stable at H site as reported in the previous studies [41,49]. The Al-Al distance is 8.52 Å. The binding energy of Al on (8,0) CNT is 1.98 eV at H site. Durgun et al obtained a value of 1.6 eV for Al binding energy [49]. The difference in binding energy is due to the use of different approximations to the exchange and correlation functional. Al binding energy on (5,5) CNT has also been calculated for the comparison purpose. The binding energy of Al in (5,5) CNT is 1.24 eV which is lower compared to the (8,0) CNT. This is due to the difference in the curvature [50]. Thus H2 adsorption studies were done in Al-decorated (8,0) CNT. In graphene, the binding energy of Al obtained with the same level of the theory is only 0.824 eV [41]. The enhanced binding energy in the case of CNTs is due to the increased curvature.
In Al-decorated (8,0) CNT, a H2 molecule was placed at a distance of ~1.48 Å from the Al atom and the structure was ...
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...gy has proposed a revised system gravimetric and volumetric target of 5.5 wt% and 40 g/L respectively. In the present system, (8,0) CNT with uniform Al-decoration has a maximum gravimetric storage capacity of 6.15 without clustering. This is higher than the revised 2015 target for onboard automobile applications. If the stability of the Al atoms is increased further, the system can absorb more number of H2 molecules and it is possible to surpass the revised ultimate target of 7.5 wt%. However, these targets are system targets and the actual capacities depend on the possibility of arranging these carbon nanostructures in 3-D networks. The H2 adsorption binding energy is 0.214 eV/H2 which is suitable for ambient condition applications [18,19]. According to the results of present and previous theoretical studies, Al-modified CNT can act as good hydrogen storage media.
11C or more commonly known as Carbon 11 is a radioisotope of Carbon (tracer) which gives off gamma rays. This radioisotope decays to Boron 11 due to beta plus decay or positron emission. Conversely this change can be a result of electron capture but the chance of this happening is minuscule (0.19-0.23% of the time). Carbon 11 has a half-life of 20.34 minutes [1]. The equation of the transformation between 11C and 11B is shown below:
The goal of this lab is to exemplify a standard method for making alkyne groups in two main steps: adding bromine to alkene groups, and followed by heating the product with a strong base to eliminate H and Br from C. Then, in order to purify the product obtained, recrystallization method is used with ethanol and water. Lastly, the melting point and IR spectrum are used to determine the purity of diphenylacetylene.
Physical Chemistry Laboratory Manual, Physical Chemistry Laboratory, Department of Chemistry, University of Kentucky, Spring 2006.
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People have often pondered the reasons for the greatness of Edith Wharton's novel, Ethan Frome. What is it that causes this story to be considered an all-time American classic? One journalist quotes a humanities professor at MIT who states that, "We turn to Wharton because the truths she tells are a bracing tonic in a culture steeped in saccharine sentimentality." The journalist goes on to describe the typical, "popular" story and how they often have endings where "romantic ideals are magically fulfilled..." There is much more to Ethan Frome than simply an unhappy ending to contrast with the many other stories that have sugar-coated and sanguine endings. At first glance, the ending of Ethan Frome may appear to be only depressing. In truth, Wharton offers the reader a complex ending through the careful incorporation of poetic justice and irony.
...Coauthor, ChemBioChem 2006, 7, 1-10; b) A. Author, B. Coauthor, Angew. Chem. 2006, 118, 1-5; Angew. Chem. Int. Ed. 2006, 45, 1-5.))
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Carbon Carbon is one of the basic elements of matter (Bush 1230-1231). The name carbon comes from the Latin word "carbo" meaning charcoal. Carbon is the sixth most abundant element (Gangson). More than 1,000,000 compounds are made from carbon (Carbon (C)). "The Element Carbon is defined as a naturally abundant non-metallic element that occurs in many inorganic and in all organic compounds, exists freely as graphite and diamond and as a constituent of coal, limestone, and petroleum, and is capable of chemical self-bonding to form an enormous number of chemically, biologically, and commercially important molecules.
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Ionic compounds, when in the solid state, can be described as ionic lattices whose shapes are dictated by the need to place oppositely charged ions close to each other and similarly charged ions as far apart as possible. Though there is some structural diversity in ionic compounds, covalent compounds present us with a world of structural possibilities. From simple linear molecules like H2 to complex chains of atoms like butane (CH3CH2CH2CH3), covalent molecules can take on many shapes. To help decide which shape a polyatomic molecule might prefer we will use Valence Shell Electron Pair Repulsion theory (VSEPR). VSEPR states that electrons like to stay as far away from one another as possible to provide the lowest energy (i.e. most stable) structure for any bonding arrangement. In this way, VSEPR is a powerful tool for predicting the geometries of covalent molecules.
In an age where our dependence on fossil fuels and other expendable resources is dramatically increasing as our supply is decreasing, it is imperative that new forms of energy arise. Although it is still in very early stages, it is fundamentally plausible that hydrogen could become a major fuel source in cars. For example, Honda has already released five hydrogen fuel cell cars.