Morphological Characterization of Selected Aliphatic and Aromatic Hydrocarbons.

Title

Morphological Characterization of Selected Aliphatic and Aromatic Hydrocarbons.

Creator

Sreeharan Sreelakshmi

Description

In the last few years considerable interest has been aroused in the study of amorphous carbon. Amorphous carbon has a wide range of properties that are primarily controlled by the different bond hybridizations possible in such materials. This gives different properties like high strength, flexibility etc. Due to these properties, they are used in thin film technology and in nanoscale electronic devices. Films can range from those with high transparency and are hard and diamond-like, through to those which are opaque, soft and graphitic-like. Application areas include field emission cathodes, electronic devices, medical and optical coatings. Hence study of different carbon structures has been of great interest for many researchers. Several techniques have been used to study various sources of carbon. Hydrocarbons are the most abundant sources of carbon. The majority of hydrocarbons found, naturally occur in crude oil and the decomposition of these give hydrogen and carbon. Incomplete combustion of hydrocarbons leads to the production of polycyclic aromatic hydrocarbons. Hydrocarbon combustion therefore mainly have aromatic and aliphatic chains of carbon. Hydrocarbons are by far the most widespread precursors among carbon sources employed in the production of carbon nanotubes and carbon nanosphers. In the present study diesel soot, camphor soot and coal has been used as precursors for nanomaterials. Impurities in the samples can reduce efficiency of production. Mineral matter encompasses dissolved salts in the pore water and inorganic elements associated with the organic compounds, as well as crystalline and non-crystalline mineral particles. Quantitative analysis of minerals and other inorganics contributes to defining coal quality. Therefore a study on effects of bio and base leaching on coal samples are also done. XRD is one of the majorly used techniques to deduct the various structural parameters like interlayer spacing of crystalline (d002) structure, crystallites size (La, Lc), aromaticity (fa), number of layers of carbon atoms per aromatic lamellae(n). According to Scherrer, crystallite size varies inversely with peak width. Therefore it is a known fact that a broad hump in the spectrum indicates the presence of nano layers. These parameters are determined from the intensity profiles of the sample hydrocarbons. Also the structure of the hydrocarbon can be characterized using NMR and SEM EDS. 1H NMR spectra can yield structural information that allows classification of complex mixtures containing hundreds of aromatic, naphthenic, paraffinic, olefinic, and isoparaffinic compounds. SEM/EDS techniques allow both inorganic analysis of bulk materials and determination of chemistry and abundance of microscopic constituents. SEM analysis also gives us the size of nano particles formed in the sample. EDS allows one to identify what those particular elements are and their relative proportions. CHNS analysis gives the elemental composition of the samples. The study shows that the carbonaceous soot produced from combustion of diesel in engine show the presence of significant amount of carbon nanomaterials. The SEM micrographs indicate that nanoparticle present in diesel soot is clusters of carbon nanospheres. EDS analysis reveals the soot particles to be composed of primarily carbon and oxygen along with hydrogen. NMR spectrum of the soot reveals significant aliphatic component with predominance of methyl and methylene groups on ?and ?? positions to aromatic rings. Camphor soot XRD analysis shows presence of ordered layers of nanolayers and laso the presence of CNTs. The SEM micrographs of camphor show the presence of carbon nanostructures. The EDS analysis shows more of carbon and oxygen along with aluminium, silicon and potassium. Study of coal samples treated with biological leaching agents reveals that Penicillium spp (PE) treated sample is having more of a graphitic or ordered structure and the d002 spacing of this sample is 3.37 ?? which is close to graphite. XRD data of coal sample treated with base leaching agents confirms the turbostratic structure of coal. The SEM micrographs of the samples show that KN has more graphite like sheet structures.

Source

Physics

Date

2012