Manish Pratap Singh

Studies on Imidazolium-Based Ionic Liquids Having a Large Anion Confined in a Nanoporous Silica Gel Matrix

The properties of large molecules confined in nanopores are expected to be different from those of the bulk. This study reports changes in the phase behavior and vibrational frequencies of an imidazolium-based ionic liquid (IL), namely, 1-butyl-3-methyl imidazolium octyl sulfate ([BMIM][OcSO(4)]) in a nanoporous silica gel matrix. Nanoporous silica gel matrixes have been synthesized by a one-step sol-gel technique using tetraethylorthosilicate (TEOS) as a starting precursor. The synthesized gel has been characterized by differential scanning calorimetry (DSC), BET, TEM and FTIR. The FTIR spectra show shifts in many vibrational bands; particularly, the vibrational bands related to the imidazolium ring, aliphatic chain, and SO(3) of the IL are found to shift significantly upon confinement. The DSC results show significant changes in the melting point (ΔT(m) ≈ 52 °C), crystallization temperature (ΔT(C) ≈ 14 °C), and glass transition temperature (ΔT(g) ≈ 2 °C). The IL used in the present study has a large anion ([OcSO(4)]), and ΔT(m) for this is much larger than those reported earlier for many other ILs with relatively smaller anions. A new approach, based on the liquid-drop model, has been suggested to explain this.

Properties of Ionic Liquid Confined in Porous Silica Matrix

Porous silica matrices of different pore sizes with confined ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) [BMIM] [PF(6)] were prepared by sol-gel technique using a tetraethyl orthosilicate (TEOS) precursor with an aim to study the changes in physico-chemical properties of ionic liquid on confinement. It is found that on confinement 1) melting point decreases, 2) fluorescence spectra shows a red shift and 3) the vibrational bands are affected particularly those of imadazolium ring, which interacts more with the walls of the silica matrix. Preliminary theoretical calculations suggest that SiO(2) matrix interact more with the heterocyclic group of [BMIM] cation than the tail alkyl chain end group resulting in significant changes in the aromatic vibrations.

A new energy conversion technology joining electrochemical and physical principles

We report a new energy conversion technology joining electrochemical and physical principles. This technology can realize the fuel cell function but built on a different scientific principle. The d ...

Direct biofuel low-temperature solid oxide fuel cells

A low-temperature solid oxide fuel cell system was developed to use bioethanol and glycerol as fuels directly. This system achieved a maximum power density of 215 mW cm−2 by using glycerol at 580 °C and produced a great impact on sustainable energy and the environment.

Flowerlike CeO2 microspheres coated with Sr2Fe1.5Mo0.5Ox nanoparticles for an advanced fuel cell

Flowerlike CeO2 coated with Sr2Fe1.5Mo0.5Ox (Sr-Fe-Mo-oxide) nanoparticles exhibits enhanced conductivity at low temperatures (300–600 oC), e.g. 0.12 S cm−1 at 600 oC, this is comparable to pure ceria (0.1 S cm−1 at 800 oC). Advanced single layer fuel cell was constructed using the flowerlike CeO2/Sr-Fe-Mo-oxide layer attached to a Ni-foam layer coated with the conducting transition metal oxide. Such fuel cell has yielded a peak power density of 802 mWcm−2 at 550 oC. The mechanism of enhanced conductivity and cell performance were analyzed. These results provide a promising strategy for developing advanced low-temperature SOFCs.

Changes in dynamical behavior of ionic liquid in silica nano-pores

Dielectric relaxation measurement has been carried out on an ionic liquid (1-butyl-3-methyl imidazolium hexafluorophosphate, [BMIM][PF6]) confined in nano-porous silica matrix. Two dielectric relaxation peaks have been observed in the confined ionic liquid (IL) while there is only one relaxation peak for bulk IL. Confinement results in layering of some IL molecules near the pore wall while other molecules, less affected by pore wall interaction, remain in the central core. The two relaxation peaks are assigned to the different dynamical behaviors of the central core and layered IL molecules.

Effect of ultrasonic irradiation on preparation and properties of ionogels

Silica-gel matrices containing ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate viz. ionogels have been synthesized using one-pot nonhydrolytic sol-gel method and taking tetraethyl orthosilicate (TEOS) as starting precursor. Effect of ultrasonic irradiation on pore parameters of ionogels and vibrational properties of the IL upon confinement in the porous matrix has been investigated. The synthesized gels have been characterized by BET, DSC, TGA, and FTIR. BET analysis shows some changes in the pore parameters due to ultrasonic irradiation. DSC results indicate shift in glass transition temperature upon confinement of the IL. The FTIR spectra show changes in vibrational bands on confinement, particularly, the bands related to the imidazolium ring, aliphatic chain and anion PF6 - of the IL are found to shift upon confinement in porous silica matrix obtained due to ultrasonic irradiation. Ultrasonic irradiation has been found to affect the gelation dynamics and kinetics and pore parameters.

Ultrasonic attenuation due to phonon–phonon interaction, thermoelastic loss and dislocation damping in transition metal carbides

Temperature dependent ultrasonic attenuation due to phonon–phonon (p–p) interaction, thermoelastic loss and dislocation damping due to screw and edge dislocations have been investigated in fcc (NaCl B1 type) structured group IVb and Vb monocarbides (transition metal carbides, namely TiC, ZrC, HfC, VC, NbC and TaC) in the temperature range 50–500 K, along the three crystallographic directions of propagation, namely [100], [110] and [111] for longitudinal and shear modes of propagation. The second- and third-order elastic moduli (SOEM and TOEM) obtained at different temperatures using the electrostatic and Born repulsive potentials and taking interactions up to next-nearest neighbours, have been used to obtain Gruneisen numbers, acoustic coupling constants and their ratios along different directions of propagation and polarization for longitudinal and shear modes of wave propagation. Temperature variation of the phonon relaxation time shows exponential decay. The results have been discussed and compared with available data.

A new technique for determination of melting temperature of poly(ethylene glycol) by ultrasonic velocimetry

Ultrasonic velocity and density of poly(ethylene glycol) (PEG) (mol. wt. 2000 and 8000) solutions in water and benzene have been studied as a function of temperature from which respective isentropic compressibility has also been calculated. The velocity (as well as isentropic compressibility) undergoes a sudden change near melting temperature, T m, of the solute polymer. Normally, we expect only one peak in viscoelastic properties at the T m of PEG. However, we see two peaks (T m1 and T m2) in the case of the aqueous solution of PEG while there is only one peak for the case of benzene solution. This has been interpreted on the basis that one of the peaks (T m1) is for unsolvated PEG and the other peak (T m2) is that of PEG with water solvation shell. Such solvation shell is not formed with the aprotic solvent (benzene).

Acoustical Dissipation Due to Phonon-Phonon Interaction, Thermoelastic Loss and Dislocation Damping in MnO and CoO

Temperature dependent ultrasonic attenuation due to phonon-phonon interaction, thermo-elastic mechanism and dislocation damping due to screw and edge dislocations have been evaluated in MnO and CoO in fcc (B1- type) phase, in a wide temperature range 50 {less than or equal to} T {less than or equal to} 500 K for longitudinal and shear modes of propagation along three crystallographic directions viz. , and . Electrostatic and Born-Mayer potentials were used to obtain second and third order elastic moduli at different temperatures taking interactions up to next nearest neighbours. Second and third order elastic moduli obtained at different temperatures have been used to obtain gruneisen parameters and non-linearity parameters which in turn were used to evaluate attenuation coefficient over frequency square viz. (α/f2) for longitudinal and shear waves. Specific heat (as function of Debye temperature), hardness parameter and lattice parameter have been used as input data. Results have been dis...