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It is well known that cobalt exhibits polymorphism, i.e., the co-existence of both the hcp and fcc phases. In particular, the method of synthesis and other thermodynamic conditions is known to play a crucial role in determining the particular phase of cobalt. In this work, we have compared the phase composition of the cobalt nanoparticles synthesized using two different solvents (water) and ethanol (Co@C). XRD measurements confirm the existence of fcc phase in commercial cobalt nanoparticles (Co@A), co-existence of fcc and hcp phases in Co@B, while the existence of the hcp phase in Co@C. We have studied these cobalt nanoparticles using 59Co internal field nuclear magnetic resonance (IFNMR) for verification of phase composition. Our studies reveal that the Co@A has fcc as a major phase with minor quantity hcp phase. Co@B exhibits approximately equal amount of fcc and hcp phase while Co@C exhibits hcp as a major phase with minor fcc phase. Our SEM micrograph studies confirm that the cobalt particles have spherical shape in the fcc phase. The cobalt particles exhibit both spherical and dendrite morphology confirming the co-existence of fcc and hcp phases, while the sample with pure hcp phase exhibits the dendrite morphology. Our studies also throw light on understanding the effect of solvent in the phase formation of the cobalt nanoparticles. [ABSTRACT FROM AUTHOR]

The 85 MeV ^12\C^6+ and 35 MeV ^12\C^3+ ion induced forward current gain degradation on 2N 6052 transistor is investigated by $I$– V$ measurements before and after irradiation. The decrease in gain for 85 MeV C-ion irradiated transistor is drastic, indicating the device is vulnerable for higher energy irradiation. An increase in the base current leading to degradation of the current gain may be due to displacement damage dose. C$– V versus base-emitter voltage shows that the doping concentration increases marginally upon irradiation. DLTS measurements indicate the cluster defects are produced after irradiation to a fluence of \1\times \10^12\ \ions/cm^2. [ABSTRACT FROM PUBLISHER]

In this paper, we report an enhancement in ionic conductivity in a new nano-composite solid polymer electrolyte namely, (PEG) LiBr: y(SiO). The samples were prepared, characterized, and investigated by XRD, IR, NMR, and impedance spectroscopy. Conductivity as a function of salt concentration shows a double peak. Five weight percent addition of silica nanoparticles increases the ionic conductivity by two orders of magnitude. Conductivity exhibits an Arrhenius type dependence on temperature. IR study has shown that the existence of nanoparticles in the vicinity of terminal O-H group results in a shift in IR absorption frequency and increase in amplitude of vibration of the terminal O-H group. This might lead to an enhancement in conductivity due to increased segmental motion of the polymer. Li NMR spectroscopic studies also seem to support this. Thus addition of nanoparticle inert fillers still seems to be a promising technique to enhance the ionic conductivity in solid polymer electrolytes. [ABSTRACT FROM AUTHOR]

1H and 19F spin-lattice relaxation times in polycrystalline diammonium hexafluorozirconate have been measured in the temperature range of 10–400 K to elucidate the molecular motion of both cation and anion. Interesting features such as translational diffusion at higher temperatures, molecular reorientational motion of both cation and anion groups at intermediate temperatures and quantum rotational tunneling of the ammonium group at lower temperatures have been observed. Nuclear magnetic resonance (NMR) relaxation time results correlate well with the NMR second moment and conductivity studies reported earlier. [ABSTRACT FROM AUTHOR]