Enhanced ionic conductivity in nano-composite solid polymer electrolyte: (PEG)x LiBr: y(SiO2)

In this paper, we report an enhancement in ionic conductivity in a new nano-composite solid polymer electrolyte namely, (PEG)x LiBr: y(SiO2). 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. 7Li 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

1H and 19F NMR relaxation time studies in (NH4)2ZrF6 superionic conductor

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

Internal Field Nuclear Magnetic Resonance: A Versatile Tool to Study the Structural and Magnetic Properties of Ferromagnetic Materials

59Co-Internal Field Nuclear Magnetic Resonance (IFNMR), 57Fe-IFNMR measurements are carried for the different materials like bulk cobalt, carbon coated cobalt (Co@C), bulk iron, carbon coated iron nanoparticles (Fe@C). The comparison of obtained results for bulk cobalt and Co@C shows that the bulk cobalt exists in the both the phases i.e., fcc and hcp phases, while the other exist only in the fcc phase. Further, the comparison of the NMR results of bulk iron and Fe@C confirms the presence of the single domain particles in the Fe@C samples. Thus, we propose IFNMR as a powerful tool to identify the structural and magnetic properties of ferro/ferrimagnetic materials

Fabrication of low cost and versatile internal field pulsed nuclear magnetic resonance spectrometer to study the magnetic materials

We have built a low cost and versatile pulsed internal field nuclear magnetic resonance (IFNMR) spectrometer and used it to study ferromagnetic materials. Initially optimization of the instrument has been tested with nuclear quadrupole resonance (NQR) active nuclei. Ferromagnetic materials like bulk iron, bulk cobalt and carbon coated cobalt nanopowder have been used as the testing materials for our spectrometer. Preliminary results obtained from the present spectrometer have been compared with the earlier reports and are in good agreement. The specifications and performance standard of the instrument match quite well with standard instruments elsewhere in the world which is testified with the observation of NMR echo signals in the above mentioned materials confirming the quality of the spectrometer. Additionally NMR signals from the grain boundaries are observed in Co@C nanomaterials which prove the sensitivity of the spectrometer

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

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

Determination of Phase Composition of Cobalt Nanoparticles Using 59Co Internal Field Nuclear Magnetic Resonance

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

Enhancement in ionic conductivity on solid polymer electrolytes containing large conducting species

Solid Polymer Electrolytes (SPEs) lack better conducting properties at ambient temperatures. Various methods to enhance their ionic conductivity like irradiation with swift heavy ions, γ-rays, swift electrons and quenching at low temperature etc., have been explored in the literature. Among these, one of the oldest methods is incorporation of different conducting species into the polymer matrix and/or addition of nano-sized inert particles into SPEs. Various new salts like LiBr, Mg(ClO4)2, NH4I etc., have already been tried in the past with some success. Also various nanoparticles like Al2O3, TiO2 etc., have been tried in the past. In this article, we have investigated an SPE containing Rubidium as a conducting species. Rubidium has a larger ionic size compared to lithium and sodium ions which have been investigated in the recent past. In the present article, we have investigated the conductivity of large sized conducting species and shown the enhancement in the ionic conductivity by addition of nano-sized inert particles

Internal Field Nuclear Magnetic Resonance: A Versatile Tool to Study the Structural and Magnetic Properties of Ferromagnetic Materials

59Co-Internal Field Nuclear Magnetic Resonance (IFNMR); 57Fe-IFNMR measurements are carried for the different materials like bulk cobalt; carbon coated cobalt (Co@C); bulk iron; carbon coated iron nanoparticles (Fe@C). The comparison of obtained results for bulk cobalt and Co@C shows that the bulk cobalt exists in the both the phases i.e.; fcc and hcp phases; while the other exist only in the fcc phase. Further; the comparison of the NMR results of bulk iron and Fe@C confirms the presence of the single domain particles in the Fe@C samples. Thus; we propose IFNMR as a powerful tool to identify the structural and magnetic properties of ferro/ferrimagnetic materials

Hydrogen NMR study of molecular dynamics in dihydrazinium sulfate

The proton spin-lattice relaxation time $T_1$ and second moment $M_2$ have been measured in dihydrazinium sulfate $(N_2H_5)_2SO_4$ in the temp. range 77-300 K to understand the nature of mol. motions. Two $T_1$ min. and an $M_2$ transition have been obsd. The obsd. $T_1$ min. are explained in terms of the reorientation of two inequiv. $NH_3$ groups. The second moment behavior has been interpreted in terms of NH3/NH2 motions. The activation energies of the inequiv. $NH_3$ groups are 28.0 and $28.5 kJ mol^{-1}.