We correlate in the first part of this study the specific heat and thermal expansivity to the temperature-and pressure-dependent frequency shifts, respectively, in ammonia solid I, solid II, hexagonal ice and ice close to their melting points. This is carried out for some fixed pressures for the two translational and one librational modes in ammonia solid I. By obtaining linear plots of specific heat and thermal expansivity against temperature-and pressure-dependent frequency shifts, the values of slope were deduced and compared with experimental values. The correlation between the thermal expansivity and frequency shifts was constructed in the ammonia solid II by calculating the Raman frequencies of the translational and the librational modes for some fixed pressures. Calculated values of slope were compared with experimental values. Temperature and pressure dependent frequency shifts of the translational modes in hexagonal and ice are correlated to the specific heat and the thermal expansivity, respectively. When the mode Gr&uuml / neisen parameter depends on temperature and pressure, correlations among the specific heat, thermal expansivity and, temperature-and pressure-dependent frequency shifts, respectively, are reexamined in hexagonal ice. When the mode Gr&uuml / neisen parameter depends on temperature, correlation between the specific heat and the frequency shifts is reexamined using translational modes in NH4Cl. In the second part of this study, we predict the damping constant for ammonium halides (NH4Cl and NH4Br) for zero pressure, and for the tricritical and second order phase transitions for a lattice mode of NH4Cl. Also, the observed Raman intensities of this mode are analyzed at those two pressures.

In this work, ionic liquids (ILs) were investigated for use as battery electrolytes. The ILs were synthesized from quaternary ammonium and phosphonium salts and TFSI-. A dendrite free lithium metal anode was demonstrated by deposition of a lithium-potassium alloy. Several phosphonium ILs were synthesized using the TFSI- and PF6- anions until a room temperature IL was obtained. The smaller size, highly symmetric PF6- anion yielded high melting point salts, while TFSI- yielded much lower melting point ILs. When a room temperature IL, Bu3HexP+TFSI-, was obtained the analogous ammonium IL, Bu3HexP+TFSI-, was synthesized and compared. The phosphonium-based ionic liquid showed improved stability and physical properties compared to the analogous ammonium-based IL. The phosphonium-based IL had higher conductivity, 0.43 mS/cm, than the ammonium-based IL, 0.28 mS/cm. The addition of LiTFSI to both ILs led to a decrease in conductivity and increase in viscosity. The lower viscosity and higher stability of the phosphonium-based IL led to higher current density and stability for electrodeposited lithium metal. IL reduction interfered with lithium deposition reflecting lower coulombic efficiencies and giving the appearance of an unstable lithium couple. An optimum deposition potential was found which was bounded by the electrochemical stability of each IL. The stability of lithium in the ILs increased at lower temperature due to slower reactivity with the IL. Addition of higher quantities of lithium ions caused a higher fraction of the cathodic current going to lithium deposition that was reoxidized. The stability of lithium in the ILs increased at lower temperature due to slower reactivity with the IL. The electrodeposition and reoxidation of potassium was also demonstrated. Deposition of a lithium-potassium alloy caused slight increases in the cathodic and anodic currents along with higher coulombic efficiencies. Also, it was found that a lithium-potassium alloy could be deposited at high current for long times without the occurrence of dendrites.

The heat flux demands for electronics cooling applications are quickly approaching the limits of conventional thermal management systems. To meet the demand of next generation electronics, a means for rejecting high heat fluxes at low temperatures in a compact system is an urgent need. To answer this challenge, in this work a gasketed chevron plate heat exchanger in conjunction with a slurry consisting of highly endothermic solid ammonium carbamate and a heat transfer fluid. A reduced-order 1-dimensional model was developed and used to solve the coupled equations for heat, mass, and momentum transfer. The feasibility of this chosen design for satisfying the heat rejection load of 2kW was also explored in this study. Also, a decomposition reaction using acetic acid and sodium bicarbonate was conducted in a plate heat exchanger (to simulate a configuration similar to the ammonium carbamate reactions). This enabled the experimental validation of the numerical predictions for the momentum transfer correlations used in this study (which in turn, are closely tied to both the heat transfer correlations and chemical kinetics models). These experiments also reveal important parameters of interest that are required for the reactor design. A numerical model was developed in this study and applied for estimating the reactor size required for achieving a power rating of 2 kW. It was found that this goal could be achieved with a plate heat exchanger weighing less than 70 kg (~100 lbs) and occupying a volume of 29 L (which is roughly the size of a typical desktop printer). Investigation of the hydrodynamic phenomena using flow visualization studies showed that the flow patterns were similar to those described in previous studies. This justified the adaptation of empirical correlations involving two-phase multipliers that were developed for air-water two-phase flows. High-speed video confirmed the absence of heterogeneous flow patterns and the prevalence of bubbly flow with bubble sizes typically less than 0.5 mm, which justifies the use of homogenous flow based correlations for vigorous gas-producing reactions inside a plate heat exchanger. Absolute pressure measurements - performed for experimental validation studies - indicate a significant rise in back pressure that are observed to be several times greater than the theoretically estimated values of frictional and gravitational pressure losses. The predictions from the numerical model were found to be consistent with the experimental measurements, with an average absolute error of ~26%

The Vanadium bromide (V/Br) flow cell employs the Br3-/Br- couple in the positive and the V(II)/V(III) couple in the negative half cell. One major issue of this flow cell is bromine gas formation in the positive half cell during charging which results from the low solubility of bromine in aqueous solutions. Bromine complexing agents previously used in the zinc-bromine fuel cell were evaluated for their applicability in V/Br flow cell electrolytes. Three quaternary ammonium bromides: N-ethyl-N-methyl-morpholinium bromide (MEM), N-ethyl-N-methyl-pyrrolidinium bromide (MEP) and Tetra-butyl ammonium bromide (TBA) were studied. It is known that aqueous bromine reacts with quaternary ammonium bromides to form an immiscible organic phase. Depending on the number of quaternary ammonium bromides used and the environmental temperature, the second phase formed will either be solid or liquid. As any solid formation would interrupt the flow cell operation, potential formation of such kind has to be eliminated. Stability tests of simulated V/Br electrolyte with added quaternary ammonium bromides were carried out at 11, 25 and 40 oC. In the absence of bromine, the addition of MEM, MEP and TBA were found to be stable in V/Br electrolytes. However, in the presence of bromine, solid formation was observed in the bromine rich organic phase when the V/Br electrolyte contained a single quaternary ammonium bromide (QBr) compound. For V/Br electrolytes with binary or ternary QBr mixtures containing TBA, the presence of bromine caused a viscous polybromide phase to form at room temperature and the release of bromine gas at higher temperature. Only a binary mixture of MEM and MEP formed a stable liquid organic phase between 11 ?? 40 oC. In this study it was found that V/Br electrolytes containing a binary QBr mixture (0.75M) of MEM and MEP gave the best combination that formed an orange oily layer in the presence of bromine without solidification between 11 ?? 40oC. Furthermore, it was found that samples of V/Br electrolytes containing a ternary QBr mixture, are less effective in bromine capturing if the total QBr concentration was less than 1 M at 40oC, where bromine gas evolution was observed. From electrochemical studies of V3+/V2+, it was found that the addition of MEM and MEP had a minimal effect on the formal potential of the V3+/V2+ couple, the V2+/V3+ transfer coefficient and the diffusion coefficient of V3+. Therefore, MEM and MEP can be added to the negative half-cell of a V/Br flow cell without major interference From linear sweep voltammetry, the kinetics of the Br-/Br3- redox couple was found to be mass transfer controlled. After the addition of MEM and MEP mixture, the exchange current density was found to decrease from 0.013 Acm-2 to 0.01 Acm-2. On the other hand the transfer coefficient before and after MEM and MEP addition was found to be 0.5 and 0.44 respectively. Since the kinetic parameters were not significantly affected by the addition of MEM and MEP mixture, they can be added to the positive half-cell of the V/Br flow cell as bromine complexing agents. The electrochemical studies of both V3+/V2+ and Br-/Br3- showed the addition of MEM and MEP has minimal interference with the redox reactions of the vanadium bromide flow cell. This thesis also investigated the effect of MEM and MEP addition on the cell performance of a lab scale V/Br flow cell using two different membranes (ChiNaf and VF11). Flow cell performance for 2 M V3.7+ + 0.19 M MEM + 0.56 M MEP electrolytes utilising ChiNaf membrane at 10 mAcm-2 produced an energy efficiency of 59%, and this decreased to 43% after 15 cycles. For the static cell utilising VF11 membrane, the addition of MEM and MEP reduced the energy efficiency from 59.7% to 43.4%. It is believed that this is caused by the mass transfer controlled Br-/Br3- couple in the complexed positive half-cell solution. Therefore, uniformity between the organic and aqueous phase is important for flow cells utilising electrolytes with MEM and MEP. Finally, the polarization resistance of a lab scale V/Br flow cell utilising ChiNaf membrane and 2 M V3.7+ electrolytes was found to be slightly higher during cell charging (3.9 cm2) than during the discharge process (3.6 cm2), which is opposed to that in the all-vanadium redox cell.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2000. / Härtill 4 uppsatser.

Thesis (M.S.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 15, 2008) Vita. Includes bibliographical references.

Thesis (Ph. D., Chemical Engineering)--University of Idaho, May 2006. / Major professor: Vivek Utgikar. Includes bibliographical references (leaves 99-107). Also available online (PDF file) by subscription or by purchasing the individual file.

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.

Thesis (M.S.) -- Mississippi State University. Dave C. Swalm School of Chemical Engineering. / Title from title screen. Includes bibliographical references.