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An effective medium ratio obeying meta-atom for multiband applications

Hossain M. J., Faruque M. R. I., Islam M. T., Islam S. S.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2017

Vol. 65, nr 2

139--147

In this paper, an effective medium ratio obeying, negative refractive index, compact meta-atom was designed, manufactured and tested for operation in a multiband microwave regime. The proposed meta-atom structure obeyed better effective medium ratio. The results of the measurement were verified by the commercially available Computer Simulation Technology (CST) Studio Suite 2014 simulator. The effective medium ratio obeying meta-atom displayed multiband response, in conjunction with negative refractive index property over a certain frequency band in the microwave frequency span. Furthermore, a few parametric analyses were completed with the meta-atom, and the effective medium parameters were investigated. The sizes and complex scattering constitutive parameters of the proposed negative refractive index, compact meta-atom are applicable for multiband applications in microwave regime.

Investigation of effects produced by chemical functionalization in single-walled and multi-walled carbon nanotubes using Raman spectroscopy

Hussain S, Shah K A, Islam S S

Materials Science Poland

2013

Vol. 31, No. 2

276--280

Single-wall carbon nanotubes (SWNTs) as well as multi-wall carbon nanotubes (MWNTs) were characterized by Raman spectroscopy to observe the changes in their physical and structural properties on functionalization. When SWNTs or MWNTs are chemically treated, the defects are created. The analysis of radial breathing mode (RBM) showed that the diameter of the single wall carbon nanotubes changed after functionalization. In the carboxylated sample, the intensity of the disordered band (D-mode) increased more than in the pristine samples. The increase in the D-band intensity in SWNTs after functionalization can be attributed to carbon atoms excited from sp2 to sp3 hybridization. A higher intensity ratio in D-and G-mode (ID/IG) was observed after functionalization with carboxylic group (COOH). The intensity ratio ID/IG increased on acid treatment which was evident from the Raman spectra and their analysis. In case of MWNTs, the intensity of D band became equal to the intensity of G band, which was due to the huge number of defects that had been introduced in the sidewalls. Moreover, it was found in this study that the MWNTs can be much easier chemically functionalized than SWNTs under the same physical conditions.