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S. K. Sharma T. K. Mandal C. Sharma Jagdish Chandra Kuniyal Ranjan Joshi Pitamber Prasad Dhyani Rohtash A. Sen H. Ghayas N. C. Gupta Priyanka Sharma M. Saxena A. Sharma B. C. Arya Arun Kumar 《Mapan》2014,29(4):243-253
Ambient trace gases (NH3, NO, NO2 and SO2) and black carbon (BC) were measured along with particulate matter (PM2.5) over the northwestern Himalayan region (Palampur, Kullu, Shimla, Solan and Nahan) of Himachal Pradesh (HP), India in a campaign mode during 12–22 March 2013 to evaluate the ambient air quality of the region. The average mixing ratio of ambient NH3, NO, NO2 and SO2 were recorded as 7.1 ± 2.6, 3.1 ± 1.3, 3.9 ± 1.4 and 1.7 ± 0.7 ppb respectively over the northwestern Himalayan region. The average concentration of BC was estimated as 2.2 ± 0.5 µg m?3 over the region whereas average concentration of PM2.5 mass was estimated as 41.8 ± 7.9 µg m?3. The spatial variation of ambient trace gases (NH3, NO, NO2 and SO2), BC and PM2.5 over the northwestern Himalayan region, India reveals that the region is mainly influenced by local activities, i.e., tourism activities, agricultural activities, biomass burning and vehicular emission. A significant positive linear correlation of NH3 and NH4 + with SO4 2?, NO3 ? and Cl? (NH4 + vs. SO4 2? , r 2 = 0.652; NH4 + vs. NO3 ?, r 2 = 0.701; and NH4 + vs. Cl?, r 2 = 0.627) of the PM2.5 indicates the possible formation of (NH4)2SO4, NH4NO3 and NH4Cl aerosols over the region. 相似文献
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A simple effective pyrolysis technique has been developed to synthesize aligned arrays of multi-walled carbon nanotubes (MWCNTs) without using any carrier gas in a single-stage furnace at 700?°C. This technique eliminates nearly the entire complex and expensive machinery associated with other extensively used methods for preparation of CNTs such as chemical vapour deposition (CVD) and pyrolysis. Carbon source materials such as xylene, cyclohexane, camphor, hexane, toluene, pyridine and benzene have been pyrolyzed separately with the catalyst source material ferrocene to obtain aligned arrays of MWCNTs. The synthesized CNTs have been characterized by scanning electron microscopy (SEM), x-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Raman spectroscopy. In this technique, the need for the tedious and time-consuming preparation of metal catalysts and continuously fed carbon source material containing carrier gas can be avoided. This method is a single-step process where not many parameters are required to be monitored in order to prepare aligned MWCNTs. For the production of CNTs, the technique has great advantages such as low cost and easy operation. 相似文献
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Pitamber Mahanandia P. N. Viswakarma Prasad Vishnu Bhotla S. V. Subramanyam Karuna Kar Nanda 《Bulletin of Materials Science》2010,33(3):215-220
The influence of concentration and size of sp
2 cluster on the transport properties and electron field emissions of amorphous carbon films have been investigated. The observed
insulating to metallic behaviour from reduced activation energy derived from transport measurement and threshold field for
electron emission of a-C films can be explained in terms of improvements in the connectivity between sp
2 clusters. The connectivity is resulted by the cluster concentration and size. The concentration and size of sp
2 content cluster is regulated by the coalescence of carbon globules into clusters, which evolves with deposition conditions. 相似文献
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A. Sen Y. Nazeer Ahammed B. C. Arya Tirthankar Banerjee G. Reshma Begam B. P. Baruah A. Chatterjee Anil K. Choudhuri Amit Dhir Trupti Das Pitamber Prasad Dhyani N. C. Deb Ranu Gadi Mangesh Gauns Sanjay Kumar Ghosh Abhishek Gupta K. C. Sharma A. H. Khan K. Maharaj Kumari Manish Kumar Arun Kumar Jagdish Chandra Kuniyal Anita Lakhani R. K. Meena P. S. Mahapatra S. W. A. Naqvi Dharam Pal Singh S. Pal Sipra Panda Rohtash J. Saikia P. Saikia A. Sharma Priyanka Sharma M. Saxena D. M. Shenoy C. Viswanatha Vachaspati S. K. Sharma T. K. Mandal 《Mapan》2014,29(4):273-284
In this paper, we present mass concentrations of particulate matter [PM2.5, PM10 size fractions and total suspended particulates (TSP)] measured simultaneously over land stations (Kullu, Patiala, Delhi, Ajmer, Agra, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Jorhat, Itanagar, Imphal, Bhubaneswar, and Kadapa), mostly distributed across the Indo-Gangetic plain (IGP) of India as well as in the marine atmosphere over Bay of Bengal (BoB) in the period from 20 January to 3 February, 2014. The main objective of this study was to quantify the continental outflow of particulates (PM2.5, PM10 and TSP) from IGP and associated regions into the BoB along with low level north-east wind flow during winter monsoon period. The present study provides a glimpse of the aerosol loading over the IGP region. During this campaign, the highest average PM2.5 (187.8 ± 36.5 µg m?3, range 125.6–256.2 µg m?3), PM10 (272.6 ± 102.9 µg m?3, range 147.6–520.1 µg m?3) and TSP (325.0 ± 71.5 µg m?3, range 220.4–536.6 µg m?3) mass concentrations were recorded at Varanasi, Kolkata and Lucknow over middle and lower IGP regions. The PM2.5 (average 41.3 ± 11.9 µg m?3; range 15.0–54.4 µg m?3), PM10 (average 53.9 ± 18.9 µg m?3; range 30.1–82.1 µg m?3) and TSP (average 78.8 ± 29.7 µg m?3; range 49.1–184.5 µg m?3) loading over BoB were found to be comparable to land stations and suggests possible continental outflow. Over the continental region, the highest PM2.5/PM10 ratio was recorded at Delhi (0.87). The PM2.5/PM10 ratio over BoB (0.77) was found to be quite high and comparable to Varanasi (0.80) and Agra (0.79). 相似文献
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Pitamber Mahanandia Ved Prakash Arya Karuna Kar Nanda Prasad V. Bhotla Somanhali V. Subramanyam 《Materials Science and Engineering: B》2009,164(3):140-150
Various carbon nanostructures (CNs) have been prepared by a simple deposition technique based on the pyrolysis of a new carbon source material tetrahydrofuran (THF) mixed with ferrocene using quartz tube reactor in the temperature range 700–1100 °C. A detailed study of how the synthesis parameter such as growth temperature affects the morphology of the carbon nanostructures is presented. The obtained CNs are investigated by scanning electron microscope (SEM), X-ray diffraction (XRD), electron dispersive scattering (EDS), thermogravimetry analysis (TGA), Raman and transmission electron microscope (TEM). It is observed that at 700 °C, normal CNTs are formed. Iron filled multi-walled carbon nanotubes (MWCNTs) and carbon nanoribbons (CNRs) are formed at 950 °C. Magnetic characterization of iron filled MWCNTs and CNRs studied at 300 K by superconducting quantum interference device (SQUID) reveals that these nanostructures have an enhanced coercivity (Hc = 1049 Oe) higher than that of bulk Fe. The large shape anisotropy of MWCNTs, which act on the encapsulated material (Fe), is attributed for the contribution of the higher coercivity. Coiled carbon nanotubes (CCNTs) were obtained as main products in large quantities at temperature 1100 °C. 相似文献
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Kadambinee Sa Prakash Chandra Mahakul Sunirmal Saha Prakash Nath Vishwakarma Karuna Kar Nanda Pitamber Mahanandia 《Polymer Engineering and Science》2019,59(5):1075-1083
Electrical, mechanical, and thermal properties of the poly(methyl methacrylate) (PMMA) composites containing functionalized multiwalled carbon nanotubes (f‐MWCNTs) and reduced graphene oxide (rGO) hybrid nanofillers have been investigated. The observed electrical percolation threshold of FHC is 0.8 wt% with maximum conductivity of 1.21 × 10?3 S/cm at 4 wt% of f‐MWCNTs. The electrical transport mechanism and magneto resistance studied of hybrid composites have also been investigated. Progressive addition of f‐MWCNTs in rGO/PMMA composite results increase in mechanical (tensile strength and Young's modulus) and thermal (thermal stability) properties of f‐MWCNTs‐rGO/PMMA hybrid nanocomposites (FHC). The increased mechanical properties are due to the efficient load transfer from PMMA matrix to f‐MWCNTs and rGO through better chemical interaction. The strong interaction between PMMA and f‐MWCNTs‐rGO in FHC is the main cause for improved thermal stability. POLYM. ENG. SCI., 59:1075–1083, 2019. © 2019 Society of Plastics Engineers 相似文献
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We report on the R-T measurement of carbon nanotube bundles from room temperature down to 1 K. The resistance at a particular temperature depends on the diameter of the bundle. The larger the bundle diameter is, the lower the value of the resistance. The resistance increases with the decrease in temperature as in the case of carbon, carbon glass resistance thermometer, and carbon nanotubes reported in the literature. The rate of the variation of resistance depends on the resistance of the bundle at room temperature which can be explored for the low temperature thermometry. Overall, the resistance and the sensitivity of the bundle depend on the bundle diameter which can be monitored easily. 相似文献
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Synthesis and characterization of carbon nanoribbons and single crystal iron filled carbon nanotubes
Carbon nanoribbons and single crystal iron filled multiwall carbon nanotubes (MWCNTs) have been synthesized by simple pyrolysis technique. SEM investigation shows that the material consist mainly carbon nanoribbons and carbon nanotubes (CNTs). X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), electron energy dispersive X-ray (EDX), transmission electron miscroscopy (TEM) and highresolution transmission electron miscroscopy (HRTEM) studies reveal carbon nanotubes are filled with α-Fe. Closer inspection of HRTEM images indicated that the bcc structure α-Fe nanowires are monocrystalline and Fe (1 1 0) plane is indeed perpendicular to the G (0 0 2) plane, whereas orientation of (0 0 2) lattice planes of carbon nanoribbon is perpendicular to the axis of growth. Magnetic properties studied by superconducting quantum interference device (SQUID) at 300 K and 10 K exhibited coercivity of 1037 Oe and 2023 Oe. The large coercitivity is strongly attributed to the small size monocrystalline single phase α-Fe, single domain nature of the encapsulated Fe crystal, magnetocrystalline shape anisotropy and ferromagnetic behaviour of localized states at the edges of the carbon nanoribbons. 相似文献
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