NISCAIR Online Periodicals Repository Collection: IJPAP Vol.50(01) [January 2012]

Dielectric properties of soils at X-band microwave frequency

Thu, 29 Dec 2011 22:58:59 GMT

Title: Dielectric properties of soils at X-band microwave frequency

Authors: Chaudhari, H C; Shinde, V J

Abstract: Measurements of real (ε¢) and imaginary (ε’’) parts of the complex dielectric constant (ε*) of soil with varied moisture content have been made at 9.44 GHz using infinite sample method. The electrical properties of dry soil samples are found to be in good agreement with the earlier work. The values of ε¢ and ε¢¢ first increase slowly and then increase rapidly with moisture content. From this data, the ac conductivity and relaxation time are also reported in the present paper. The result shows the change in electrical properties of soils before and after the addition of water. These results provide a basis for using ground-penetrating radar or other high-frequency electromagnetic sensors in the detection of soil moisture content.

Page(s): 64-66

Size dependent dielectric properties of Co and Fe doped SnO₂ nanoparticles and their nanorods by Ce co-doping

Thu, 29 Dec 2011 22:58:59 GMT

Title: Size dependent dielectric properties of Co and Fe doped SnO₂ nanoparticles and their nanorods by Ce co-doping

Authors: Kaur, Jasneet; Gupta, Vinay; Kotnala, R K; Verma, Kuldeep Chand

Abstract: Structural, microstructural and dielectric properties of transition metal doped, i.e., Co and Fe (0, 1, 3 and 5 mol% each) SnO₂ and the formation of their nanorods by Ce (4 mol%) co-doping have been studied. These nanoparticles and nanorods were fabricated by a chemical route using polyvinyl alcohol as surfactant. The X-ray diffraction patterns show that all the specimens have tetragonal rutile structure without any extra phase. The transmission electron microscopy analysis shows that the average particle size lies in the range 11-30 nm and the diameter of rods in the range 5-20 nm and length 50-200 nm. It is observed that by co-doping of Ce³⁺, the resulting nanoparticles assembled themselves into rod like structures. The nature and concentration of dopants are found to play crucial role in tuning the morphology and electrical properties of nanostructures. The dielectric behaviour of Co and Fe dopedand Ce co-doped SnO₂nanostructures has been analyzed and it is observed that the value of dielectric constant (ε_r) decreases rapidly in lower frequency regime, whereas it depicts a slight dispersion in the middle and higher frequency range and resonant behaviour in sufficiently higher frequency region. The frequency dependent ac conductivity shows higher resistivity of nanoparticles and explains the dispersion in dielectric behaviour.

Page(s): 57-63

Temperature dependent studies of electric and dielectric properties of polythiophene based nano composite

Thu, 29 Dec 2011 22:58:59 GMT

Title: Temperature dependent studies of electric and dielectric properties of polythiophene based nano composite

Authors: Tiwari, D C; Sen, Vikas; Sharma, Rishi

Abstract: The fabrication, characterization, electric, dielectric and ac conductivity measurement of polythiophene and carbon nanotube (CNT) composite are described. The polythiophene (PTh) and polythiophene/ multiwalled carbon nanotube (PTh/MWCNT) composite are prepared chemically by oxidative polymerization of thiophene(Th). The formation of PTh and incorporation of CNTs into PTh are confirmed by Fourier Transform – Infrared spectroscopy (FT-IR) and Energy Dispersive X-Ray analysis (EDAX) analysis. Scanning Electron Microscopic (SEM) analysis revealed the formation of polymer/CNT composite. SEM image of PTh shows a leaf like structure and image of PTh/MWCNT shows the incorporation of MWCNT into the PTh flakes. Atomic force microscopic (AFM) analysis shows the morphology of PTH and PTh/MWCNT. The structural features of Nanotube-Polymer association are observed by AFM studies. The electrical behaviour of prepared samples has been studied by measuring I-V characteristics at varying temperature. The dielectric properties of these samples have been studied at low frequencies (150-700 kHz) for varying temperature. The dielectric constant for PTh/MWCNT is found to be higher than PTh for all temperature ranges. Finally,theac electrical conductivity (σ_ac) and dielectric relaxation time calculations have been carried out by using the data available from dielectric measurements and by employing a simple relationship. Conductivity shows a linear dependence on temperature and is also higher for PTh/MWCNT.

Page(s): 49-56

Depth distribution of selected geogenic radionuclides (⁴⁰K, ²²⁶Ra, ²³²Th) and anthropogenic ¹³⁷Cs in an undisturbed forest soil in East Slovenia

Thu, 29 Dec 2011 22:58:59 GMT

Title: Depth distribution of selected geogenic radionuclides (⁴⁰K, ²²⁶Ra, ²³²Th) and anthropogenic ¹³⁷Cs in an undisturbed forest soil in East Slovenia

Authors: Mabit, Lionel; Dornhofer, Patcharin; Martin, Paul; Toloza, Arsenio; Zupanc, Vesna

Abstract: To reinforce Slovenian radioecological survey information, 20 soil profiles divided into four depth increments of 10cm were collected in an undisturbed forest in east Slovenia (46°44¢N, 16°7¢E) to establish the natural (⁴⁰K, ²²⁶Ra and ²³²Th) and anthropogenic (¹³⁷Cs) level of radioactivity. Using gamma spectrometry and depending on the depth increment, the average activity concentration of radionuclides ranged from 0.5 to 70 Bq kg^-1for¹³⁷Cs, from 535 to 703 Bq kg^-1for⁴⁰K, from 49 to 52 Bq kg^-1for²²⁶Ra and from 54 to 62 Bq kg^-1for²³²Th. Based on top soil data (0-10 cm), the radium equivalent activity (Ra_eq) is 167 ± 7 Bq kg^-1, while absorbed dose rate (D) due to external gamma radiation of 79 ± 3 nGy h^-1 is higher than the world population-weighted average, reported as 58 nGy h^-1 by UNSCEAR.

Page(s): 45-48

NISCAIR Online Periodicals Repository Collection: IJPAP Vol.50(01) [January 2012]

Dielectric properties of soils at X-band microwave frequency

Size dependent dielectric properties of Co and Fe doped SnO2 nanoparticles and their nanorods by Ce co-doping

Temperature dependent studies of electric and dielectric properties of polythiophene based nano composite

Depth distribution of selected geogenic radionuclides (40K, 226Ra, 232Th) and anthropogenic 137Cs in an undisturbed forest soil in East Slovenia

Size dependent dielectric properties of Co and Fe doped SnO₂ nanoparticles and their nanorods by Ce co-doping

Depth distribution of selected geogenic radionuclides (⁴⁰K, ²²⁶Ra, ²³²Th) and anthropogenic ¹³⁷Cs in an undisturbed forest soil in East Slovenia