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- 저자 : Shekar N.V. Chandra (검색결과 3 건)
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Reddy Surakanti Srinivas,Shukla Balmukund,Srihari V.,Bhalerao G. M.,Shekar N. V. Chandra 한국탄소학회 2022 Carbon Letters Vol.32 No.4
Individual multi-walled carbon nanotubes (MWCNTs) were exposed to the electron beam of 200 kV energy and high resolution transmission electron micrographs were recorded at several time intervals. Interestingly, the nucleation of diamond nanoparticles with in the highly disordered MWCNT matrix upon electron-irradiation is observed. This happens without any assistance of high pressures and temperatures. High pressure X-ray diffraction experiments were performed on core/shell structures which suggest that even the closed structures of carbon resist any inward pressure, thereby ruling out the possibility of a hypothetical internal pressure under the electron irradiation conditions. Our experiments suggest that the transformation of graphitic carbon into diamond in the size window of a few nanometers is possible due to the stability of the diamond and a selective dissolution effect of 200 kV electrons on graphite. A mechanism for the same is proposed.
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Nath Deena,Chakravarty Sujay,Deshpade U.P.,Arasu A.V. Thanikai,Baskaran R.,Shekar N.V. Chandra 한국물리학회 2022 Current Applied Physics Vol.34 No.-
In this work for the first time, we are reporting the unusual observation of the Kondo effect with the coexistence of room temperature ferromagnetism in AlN/Al/AlN trilayer thin film. The grown film shows resistivity minimum at a temperature of ~48K, which shifts to the lower temperature on the application of magnetic fields. After considering various possibilities for an upturn in resistivity, we found that the Kondo scattering is responsible for upturn at low temperature. The simultaneous presence of ferromagnetism and Kondo scattering is explained by spatial variation of nitrogen vacancy defects from the film surface to the Al sandwich layer. Furthermore, magneto-transport properties of the film measured at different temperature exhibits both negative and positive components described by localized magnetic moment model for the spin scattering of carriers and two-band model, respectively. This work provides insight into the novel co-existence of ferromagnetism and Kondo effect in crystalline AlN.
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Study on high-pressure behaviour of spherical carbon black nanoparticles with core–shell structure
Reddy Surakanti Srinivas,Shukla Balmukund,Chakraborty Soumee,Srihari V.,Bhalerao G. M.,Shekar N. V. Chandra 한국탄소학회 2022 Carbon Letters Vol.32 No.5
We report the behaviour of carbon black (CB) nanoparticles (spherical carbon shells), subjected to external pressure, using diamond anvil cell at synchrotron facility. CB nanoparticles have been synthesized by lamp black method using olive oil as combustion precursor and ferrocene as an organometallic additive. The catalyst-assisted CB has an iron oxide (γ-Fe2O3) core and amorphous carbon shell (i.e. core–shell structure). Our present study suggests that the carbon shells are partially transparent to the applied high pressure, and result in the reduction of effective pressure that gets transferred to the iron oxide core. High-pressure Raman spectroscopy results indicate that the surrounding carbon shells get compressed with pressure and this change is reversible. However, no structural transformation was observed till the highest applied pressure (25 GPa). The Raman spectroscopy results also suggests that the carbon shells are less pressure sensitive as their pressure coefficients (dω/dP) of G-peak were calculated (3.79 cm−1/GPa) to be less than that for other carbon allotropes.
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