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Investigation of nanocrystalline structure in selected carbonaceous materials /
International Journal of Minerals, Metallurgy and Materials, Vol.21, Issue 9, pp.322-328, ISSN No: 1674-4799. -
Chemical Demineralization of High Volatile Indian Bituminous Coal by Carboxylic Acid and Characterization of the Products by SEM/EDS
Journal of Environmental Research and Development, Vol-6 (3A), pp. 653-659. ISSN-0973-6921 -
Synthesis of porous graphene sheets from agricultural waste by chemical methods
A facile technique to synthesise wrinkled graphene like nano carbon (GNC) agricultural waste like wood and coconut charcoal is reported in the current study. The charcoal is produced by thermal decomposition of wood and coconut shell and is intercalated by Hummer's method. It is separated by centrifugation and sonication to get few layer graphene sheets. The structural and chemical changes of the nanostructure are elucidated by Raman spectroscopy, TEM, SEMEDS and XPS. Raman spectra revealed the existence of highly graphitized amorphous carbon, which is confirmed by the appearance of five peaks in the deconvoluted first order Raman spectra. The SEM analysis reveals the formation of large area graphene sheets with nanoporous structure in it. The TEM/SAED analysis exhibits the presence of short range few layers graphene. 2018 World Research Association. All rights reserved. -
A comprehensive analysis of various structural parameters of Indian coals with the aid of advanced analytical tools
An exhaustive structural analysis was carried out on three Indian coals (ranging from sub-bituminous to high volatile bituminous coal) using a range of advanced characterization tools. Detailed investigations were carried out using UVVisible spectroscopy, X-ray diffraction, scanning electron microscopy coupled energy dispersive spectroscopy, Raman spectroscopy and Fourier transform infrared spectroscopy. The X-ray and Raman peaks were deconvoluted and analyzed in details. Coal crystallites possess turbostratic structure, whose crystallite diameter and height increase with rank. The H/C ratio plotted against aromaticity exhibited a decreasing trend, confirming the graphitization of coal upon leaching. It is also found that, with the increase of coal rank, the dependency of I20/I26 on La is saturated, due to the increase in average size of sp2 nanoclusters. In Raman spectra, the observed G peak (1585cm?1) and the D2 band arises from graphitic lattices. In IR spectrum, two distinct peaks at 2850 and 2920cm?1 are attributed to the symmetric and asymmetric CH2 stretching vibrations. The intense peak at ~1620cm?1, is either attributed to the aromatic ring stretching of C=C nucleus. 2016, The Author(s). -
Synthesis and characterization of porous, mixed phase, wrinkled, few layer graphene like nanocarbon from charcoal
A technique to synthesis wrinkled graphene like nano carbon (GNC) from charcoal is reported in the current study. The charcoal produced by thermal decomposition and is intercalated by Hummers method. It is separated by centrifugation and sonication to get few layer graphene sheets. The structural and chemical changes of the nanostructure is elucidated by Raman spectroscopy, TEM, SEM-EDS and XPS. Raman spectra revealed the existence of highly graphitized amorphous carbon, which is confirmed by the appearance of five peaks in the deconvoluted first order Raman spectra. The SEM analysis reveals the formation of large area graphene sheets with nano-porous structure in it. The TEM/SAED analysis exhibits the presence of short range few layer graphene. 2015 Pleiades Publishing, Ltd. -
Investigation of nanocrystalline structure in selected carbonaceous materials
The structural parameters of nine Indian coals were determined by X-ray diffraction (XRD) and Raman spectroscopy. The study revealed that the coals contain crystalline carbon of turbostratic structure with amorphous carbon. The stacking height (Lc) and interlayer spacing (d002) of the crystallite structure of the coals ranged from 1.986 to 2.373 nm and from 0.334 to 0.340 nm, respectively. The degree of graphitization was calculated to range from 42% to 99%, thereby confirming the ordering of the carbon layers with the increase in coal rank. An exponential correlation was observed among the aromaticity (fa), the lateral size (Lc), and the rank (I20/I26), suggesting that the coal crystallites are nanocrystalline in nature. A very strong correlation was observed between the structural parameters (fa, d002, Lc, the H/C ratio, and I20/I26), the volatile matter content, and the elemental carbon content, indicating the structures of coals are controlled by the degree of contact metamorphism. The Raman spectra exhibited two prominent bands: the graphitic band (G) and the first-order characteristic defect band (D). The deconvolution resulted in five peaks: G, D1, D2, D3, and D4. The intense D1 band, which appeared at ~1350 cm-1, corresponds to a lattice vibration mode with A1g symmetry. The D2 mode, which appeared at ~1610 cm-1, arises from the structural disorder as a shoulder on the G band. University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2014. -
Characterization of nano-crystalline carbon from camphor and diesel by x-ray diffraction technique
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 and camphor have been used as precursors for nanomaterials. Carbonaceous soot produced from combustion of diesel in engine shows the presence of significant amount of carbon nanomaterials. The ? band at about 19.28 has been attributed to the presence of amorphous carbon and surface defects in carbon nanotubes. The ? band at about 25.81 corresponds to e2g mode of graphite which is related to vibration of sp2bonded carbon atoms and the presence of ordered carbon nanotubes in diesel soot. The SEM micrographs provide a clear indication that nanoparticle formed in diesel soot are clusters of carbon nanospheres. Energy dispersive spectrum analysis of diesel soot confirms that the soot particles to be composed of primarily carbon and oxygen along with hydrogen. The camphor soot shows ? and ? bands which reveals the presence of crystalline graphitic carbon. The SEM micrographs of camphor show the presence of carbon nanostructures. It is found nanomaterials formed in the diesel soot consists more of disordered carbon, whereas in camphor it is more of ordered graphite like carbon. -
Chemical leaching of an indian bituminous coal and characterization of the products by spectroscopic techniques
Fourier transform infrared (FTIR) spectra of high volatile bituminous coal as well as their insoluble organic matter, obtained by chemical leaching with HF, EDTA and acid mixture (HF + HCl and HF + HNO3) were recorded between 500 and 4000 cm-1. UV-Visible-NIR spectroscopy was used to study the sample and its leached products in the 200-800 nm wavelength region. Oxygen containing structures were observed in the 1800-1000 cm-1 zone, aliphatic hydrogen in the 2920-2800 cm-1 zone, aromatic outof- plane structure in the 900-670 cm-1 zone. A great abundance of C=C structure was noticed at 1600 cm-1 region, while clay and silicate minerals were identified in the 540 cm-1 and 1030 cm-1 region. With chemical leaching silicate bands showed a decrease in intensity and were least for EDTA and HF leached samples. The UV-Visible -NIR spectrum showed absorption maximum at 235-270 nm and was shown a red shift with leaching. The II-II* electronic transitions of the poly-nuclear aromatic hydrocarbons was responsible for the absorption at 680 nm. The weak bands observed in the visible region (400-500 nm) were due to the presence of SO2 in the sample and decreased with chemical leaching. It was evident from the results that amongst the leachants used, hydrofluoric acid and acid mixture had significant effect in removing the mineral matter and oxygenated functional groups. -
Bio-demineralization of Indian bituminous coal by Aspergillus niger and characterization of the products
The effect of demineralization on an Indian bituminous coal has been investigated by filamentous fungus Aspergillus niger. X-ray diffraction profile reveals the presence of inorganic components in the sample. Bio-Solubilization using Aspergillus niger significantly reduced the ash content in the coal sample (10.23wt% to 5.21wt %). Leaching process removed silicate and pyrite minerals where as aluminates were decreased considerably. The carbon content showed an increase of 19.94% where as the oxygen content decreased by 52.3%. During biosolubilization the fungus produced acids like gluconic acid, oxalic acid and citric acid along with oxalates which are responsible for the demineralization in coal by the formation of mineral salts. The broad diffraction peak at 2?~25.5 is due to the crystalline carbon in the sample which is mainly due to the typical (002) plane reflection of graphite. -
Synthesis of nanocarbon-polyaniline composite and investigation of its optical and electrical properties
The polyaniline-nanocarbon (PANI-NC) composite was synthesized by in situ polymerization of the aniline monomer (PBC-A&B) with reduced carbon from bituminous coal (RBC). The X-ray analysis confirmed the formation of the polyaniline-graphene oxide composite. The XRD result shows that the stacking height of the PBC-A increased due to the attachment of nitrogen group to the carbon lattice. The result of CHNS confirmed the increase in composition of nitrogen in PBC-A due to the treatment of RBC with aniline to form the polymer-nanocarbon composite. Optical analysis by UV absorption spectra revealed that the band gap is in the range of 3.29-4.27 eV. The AC conductivity, dielectric permittivity, and dielectric loss of the composite are measured within a frequency response of 10 Hz to 1 MHz. It is observed that one can tailor the band gap of the PANI-GO composite by varying the concentration of reduced carbon from coal. 2019 Elsevier Ltd. All rights reserved. -
Enhancement of coal nanostructure and investigation of its novel properties
Coal is a mineral and is extensively used as a solid fuel in developing nations and has a sizeable share in the global fossil fuel reserve. Utilization of this resource generates excess spoil and large volume of low grade waste to the environment. In recent years there have been serious research on enhancing its value and exploring the utility of this carbonaceous material to novel carbon materials. The Minerals, Metals & Materials Society 2018. -
Demineralization of sub-bituminous coal by fungal leaching: A structural characterization by X-ray and FTIR analysis
The filamentous fungi, A. niger, A. flavus and Penicillium spp were studied for their ability to demineralise the low rank Indian coals. The FTIR spectra of coals showed the presence of stretching vibrations of -OH bond, aliphatic -CH, -CH2 and - CH3 absorptions, C=C and -CH of aromatic structure and mineral groups. X-ray analyses revealed that coal consists of crystalline carbon of turbostratic structure. The average lateral sizes (La), stacking height (Lc) and the interlayer spacing (d002) of the crystallite structure were calculated which ranged from 343.64 to 1.5, 223.20 to 22.54 and 3.35 to 3.60respectively. The structure of coal was modified to a product similar to that of pure graphite after leaching with Penicillium spp. Scanning electron microscopy (SEM) analysis of coal revealed a layer like structure on the surface. -
Biological elimination of minerals from high ash coal by Aspergillus-like fungi
Efficiency of filamentous fungi such as Aspergillus niger on the bio-liquefaction of low rank Indian coals, its chemical composition, surface characteristics of the products and the microbial mechanisms of coal conversion were studied. Virgin and bio-liquefied/solubilized coal samples were characterized using FT-IR, Scanning electron microscopy and CHNS and proximate analysis. The micrographs were bright field and reveal several features correspond to the mineral grains comprising of aluminium, silicates and calcites. The absence of some morphological features corresponds to inorganic elements in residual samples which confirm demineralisation with the possible formation of respective Aluminum and Silicate complexes. The change in absorption of mineral matter functional group of these coal samples were studied using Fourier transform infra red spectroscopy (FT-IR). From the proximate analysis it was found that the ash content decreased by 76% when treated with fungal culture. Global Science Publications. -
Raman spectrum of graphite layers in Indian coal
Two Indian coals of different rank (bituminous and subbituminous coal) have been demineralized by chemical method. Fourier transform Raman spectroscopy studies have been performed to study the changes in functional groups. Well resolved G peak is observed at 1605 cm-1 and 1590 cm-1 both in bituminous coal and subbituminous coal. With HF leaching, this doublet is reduced to a singlet along with reduction of frequency to 1585 cm -1 in subbituminous coal, where as in bituminous coal the absorption become very distinct. Bituminous coal is showing more intense absorption with HF leaching in this region where as subbituminous coal is shown a reduction in intensity. G' band is observed at ? 2700 cm-1 with almost the same intensity as that of G band. This confirms the presence of multilayer formation of graphite layer. The defect band at 1355 cm-1 is due to benzene or condensed benzene rings present in amorphous carbon. This band is weak in the present study. This is mainly due to immature nature of subbituminous coal than the higher rank bituminous coal. Graphite structure is remained behind after chemical leaching liberated oxygenated functional groups and mineral groups. The decrease of ID/IG ratio indicates that graphitization is increased in bituminous coal. 2011 American Institute of Physics. -
Systematic investigations of graphene layers in sub-bituminous coal
Coal is the plentiful and widely and universally used fuel. However, its structural characteristic makes a perception that it is only worthwhile for generating energy via combustion. Herein we report a simple method to synthesize nanometre-sized graphene sheets with amorphous carbon addends on the edges from sub-bituminous coal. The X-ray analysis reveals the presence of crystalline carbon in the amorphous background. The average number of carbon atoms and aromatic layers was estimated as ?21 and 8. The interlayer spacing d 002 for the aromatic lamellae of samples leached using HF and acetic acid, are found to be 0.352 and 0.376 nm, respectively. The oxidation of coal structure resulted in nanometre sized graphene having lateral size of 4.19 nm and stacking height of 2.3 nm. The Raman spectrum analysis confirmed the formation of finite sized, less defective graphene nanolayers with leaching. The crystalline carbon within the coal matrix displaced with chemical leaching, resulting nano-meter sized graphene sheets. The results also established that with HF leaching, carbon in coal becomes more stacked and ordered compared to organic acid leached coal. 2014 Pleiades Publishing, Ltd. -
Leaching of minerals in subbituminous Indian coal and characterisation of the products by SEM
Coal is chemically and physically a complex and heterogeneous material, consisting of organic and inorganic mineral constituents. Presence of minerals in excess will pollute water, air and soil. Concerted efforts are needed to reduce 'ash forming' inorganic elements and to develop clean methods of using coal. This paper reports the demineralization of sub bituminous coal with EDTA, HCl, HF, chloroform and acid mixture. The residual coal from each treatment was analyzed using Scanning Electron Microscopy (SEM) and Ultimate analysis. All the micrographs were bright field and revealed several features corresponding to the mineral grains. It comprised of lithophiles like aluminium, silicates and calcium. The absences of some morphological features correspond to inorganic elements in residual coal samples confirming 'demineralization'. This result was further confirmed with the CHNS analysis. It was evident from the results that amongst the leachants used, Hydrofluoric acid and acid mixture had significant effect in removing the mineral matter, sulphur and oxygenated functional groups. Global Science Publications. -
Study of stacking structure of amorphous carbon by X-ray diffraction technique
Random layered (graphene) structural parameters of the coals such as aromaticity fa, coal rank, number of carbon atoms per aromatic lamellae (n), lateral size La and stacking height Lc are determined using X-ray diffraction technique (XRD). It is found that the structural parameters like fa & Lc increases, where as interlayer spacing d002 decreases with increase in carbon content, aromaticity and coal rank. The number of layers and average number of carbon atoms per aromatic graphene are found to be varying from 7 to 8 and 16-21 for the coal samples with carbon content of 72- 77.4%. A good linear relationship exists between number of layers and stacking height of the aromatic lamellae in coal. 2012 by ESG. -
Chemical leaching of an Indian bituminous coal and characterization of the products by vibrational spectroscopic techniques
High volatile bituminous coal was demineralized by a chemical method. The vibrations of the "aromatics" structure of graphite, crystalline or non-crystalline, were observed in the spectra at the 1600 cm -1 region. The band at 1477 cm -1 is assigned as VR band, the band at 1392 cm -1 as VL band and the band at 1540 cm -1 as GR band. Graphite structure remains after chemical leaching liberates oxygenated functional groups and mineral groups. The silicate bands between 1010 and 1100 cm -1 are active in the infrared (IR) spectrum but inactive in the Raman spectrum. Absorption arising from C-H stretching in alkenes occurs in the region of 3000 to 2840 cm -1. Raman bands because of symmetric stretch of water molecules were also observed in the spectrum at 3250 cm -1 and 3450 cm -1. Scanning electron microscopy analysis revealed the presence of a graphite layer on the surface. Leaching of the sample with hydrofluoric acid decreases the mineral phase and increases the carbon content. The ash content is reduced by 84.5wt% with leaching from its initial value by mainly removing aluminum and silicate containing minerals. University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg 2012. -
Structural characterization of graphene layers in various Indian coals by X-Ray Diffraction technique
The results of the structural investigation of three Indian coals showed that, the structural parameters like fa & Lc increased where as interlayer spacing d002 decreased with increase in carbon content, aromaticity and coal rank. These structural parameters change just opposite with increase in volatile matter content. Considering the 'turbostratic' structure for coals, the minimum separation between aromatic lamellae was found to vary between 3.34 to 3.61 A for these coals. As the aromaticity increased, the interlayer spacing decreased an indication of more graphitization of the sample. Volatile matter and carbon content had a strong influence on the aromaticity, interlayer spacing and stacking height on the sample. The average number of carbon atoms per aromatic lamellae and number of layers in the lamellae was found to be 16-21 and 7-8 for all the samples. Published under licence by IOP Publishing Ltd. -
Facile synthesis of preformed mixed nano-carbon structure from low rank coal
Coal is a natural energy resource which is mainly used for energy production via combustion. Coal has nanocrystals embedded in it, formed during the coalification process, and is an ideal precursor for nano-carbon dots and diamonds. Herein, we report a facile top-down method to synthesise nanodots and diamonds of the size of 5 nm to 10 nm from three different types of coal by simple chemical leaching. TEM analysis revealed the formation of a mixture of carbon dots, graphene layers, and quantum dots in bituminous coal and sub-bituminous coal. Raman analysis confirmed the existence of synthesized nano-diamond and nano-carbon mixed phase with defects associated with it. It is concluded that graphene quantum dots, nano-diamonds, graphene sheets and carbon dots present in coal can be extracted by simple chemical treatment. These structures can be tuned to photoluminescent material for various optoelectronic applications or energy harvesting devices like super capacitors. 2018. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.