Detection of volatile organic compounds (VOC’s) in the environment is important for human health and wellness. Long term exposure of certain VOC’s like benzene, toluene, ethylbenzene and xylene (BTEX) has a severe effect on human health. There are techniques such as gas chromatography, photo ionization, and mass spectroscopy that are time consuming, require gas sampling and are ineffective in real time sensing in air. Acoustic wave devices such as surface acoustic wave (SAW) devices can be used for sensing BTEX compounds in both vapor and liquid phase. The quartz crystal microbalance (QCM) is a low-frequency acoustic wave device, which can be used to characterize polymer film sensing quickly and easily by studying the sorption properties of BTEX compounds in them. In this work, thin films (~ 0.5 microns) of polymer/plasticizer blends are spin-coated on a 5MHz QCM for the detection of VOC’s. A polymer/plasticizer combination of poly (ethyl methacrylate) (PEMA) and a copolymer of poly (ethyl methacrylate) and poly (methyl methacrylate) (PEMA/PMMA) with di n-butyl phthalate (DBP), di-n-butyl sebacate (DBS) and n-butyl stearate (BS) are used for the detection of benzene, toluene and ethylbenzene in vapor phase. The working apparatus consists of a stream of solvent vapor diluted with nitrogen to an arbitrary concentration passing over the QCM oscillated to its resonant frequency. The sorption data are reported at 298.15 K in terms of activity as a function of weight fraction curves and are interpreted with the Flory-Huggins ternary model. The addition of plasticizer modifies the free volume properties of the polymer, thereby increasing diffusion and sensitivity of BTEX vapors. The plasticizer composition is tailored to 17.5%, for maximum sorption with minimal viscoelastic effects. The sorption and sensitivity of BTEX are interpreted and studied in terms of plasticizer type and concentration.

Since the development of the correlation consistent composite approach (ccCA) in 2006, ccCA has been shown to be applicable across the periodic table, producing, on average, energetic properties (e.g., ionization potentials, electron affinities, enthalpies of formation, bond dissociation energies) within 1 kcal/mol for main group compounds. This dissertation utilizes ccCA in the investigation of several chemical systems including nitrogen-containing compounds, sulfur-containing compounds, and carbon dioxide complexes. The prediction and calculation of energetic properties (e.g., enthalpies of formation and interaction energies) of the chemical systems investigated within this dissertation has led to suggestions of novel insensitive highly energetic nitrogen-containing compounds, defined reaction mechanisms for sulfur compounds allowing for increased accuracy compared to experimental enthalpies of formation, and a quantitative structure activity relationship for altering the affinity of CO2 with substituted amine compounds. Additionally, a study is presented on the convergence of correlation energy and optimal domain criteria for local Møller–Plesset theory (LMP2).

A potentiometric method which is devised to be rapid and convenient for determining ionization constants for water, weak acids (or bases), and certain solids in mixed solvents is described. The method has been applied to the determination of ionization for water, acetic acid, benzoic acid, and phenol and the solubility product constant for silver chloride in mixtures of water with methanol, ethanol, acetone, tetrahydrofuran, and p-dioxane containing from 0 to 70 mass percent organic co-solvent at several temperatures between 10 and 40°C. Results are used to study the thermodynamics of ionization in each mixture which is discussed relative to various topics of ion-ion, ion-solvent, ion-molecule, molecule-solvent, and solvent-solvent interactions on the basis of theories of electrostatics, salvation, and solvent and solution structure. A calorimetric technique applied to the investigation of dimerization of benzoic acid, m-toluic acid, and o-toluic acid in benzene and toluene at 25°C as a preliminary study of the author is briefly mentioned in Appendix E.

Thermodynamic equilibrium constants were obtained potentiometrically using a Beckman pH meter for metal-serine and metal-thioglycolloc acid complexes to study the thermodynamic properties of the complexes and the effect of dπ - dπ bonding on the equilibrium constants. The following calculations were made: 1. The stepwise dissociation of protons from serine at 10, 20, 30, and 40°C and the stepwise dissociation of protons from thioglycollic acid at 20, 30, and 40°C. 2. The thermodynamic formation constants for Zn(II), Cd(II), Hg(II), and Ag(I) with serine at 10, 20, 30, and 40°C and at two ionic strengths. 3. The thermodynamic formation constants for Zn(II), Cd(II), Hg(II), and In(III) with thioglycollic acid at 20 and 30°C and at two ionic strengths. 4. The entropy, enthalpy, and free energy change for each of the metal-serine complexes. The order of increaseing stability of log K_1 for the metal-serine systems was as follows: Hg(II) > > Zn(II) > Cd(II) > Ag(I), and for log K_2 the order: Hg(II) > > Zn(II) > Cd(II) ≈ Ag(I). The stability of the Hg(II)-serine was high becasue of the high electronegativity of Hg(II) and an abundance of 4f and 5d electrons that can be polarized by the ligand donor atoms. Values for log K_1 of Zn(II), Cd(II), and Ag(I) with serine decreased in the order of decreasing electronegativity of the metal ions. All log K_2 values were smaller than log K_1 values and followed the same order of stability as log K_1 with the exception of the Ag(I)-serine complex. Linear bonding is more stable for Ag(I) than any other spatial configuration. The second formation constant is this higher than the first because the second ligand completes this stable linear complex. In(III) precipitated as a hydroxide, making it impossible to measure a formation constant for In(II) with serine. The order of increasing stability of log K_1 for the metal-thiogly-colloc acid system was as follows: Hg(II) In(III) Cd(II) Zn(II) and for log K_2 the order: Hg(II) Zn(II) In(III) Cd(II). Log K_1 values for Hg(II) In(III), and Cd(II) were above 10 indicating that these metal ions form an extremely stable bond with sulfur. This enhanced stability is due to the formation of a second bond or a d - d bond between the metal ion and the sulfur atom. The d bonding with Zn(II) is not as great as with the other metal ions. The order is somewhat reversed for log K_2 and follows the order of decreasing electronegativities of the metal ion. This would indicate that the d bonding is not as pronounced in the second formation constant. Hg(II) again has a high log K_2 value because of the electronegativity of Hg(II) and the 4f and 5d polarizable electrons. The Ag(I)-thioglyeollic acid complex could not be calculated because Ag(I) precipitated with thioglycollic acid.

Vapor pressure, heat of vaporization, and liquid heat capacity are linked through fundamental thermodynamic relationships. These related properties are essential for the safe design of many industrial processes, and measurement and prediction of these properties remains an essential part of modern thermodynamics research. DIPPR uses the fundamental relationships connecting these properties as a prediction method for all three, referred to as "the derivative method." DIPPR regards values predicted using the derivative method as highly accurate, even when compared to more traditional predictions. Despite the widespread interest in improving understanding of these properties, many questions remain regarding their prediction. Foremost among these is the treatment of associating chemicals, defined here as any species with strong hydrogen bonding. Associating species have large intermolecular attraction that is hard to compensate for in traditional equation of state modeling. For this reason, using thermodynamic relationships to predict properties of associating species is often grossly inaccurate. Improving the prediction of thermodynamic properties for this group of chemicals has been a goal of thermodynamicists and engineers for over 70 years. In this work, we set out to solve the problem of association for prediction of these properties. We began with high-level quantum calculations to determine the extent of association in several family groups and tested these against experimental measurements of dicarboxylic acids. Next, we collected experimental values for a wide array of potentially associating species and carefully examined literature practices in reporting values these properties. We tested the applicability to advanced QSPR methods to the association problem. We discovered a highly accurate limit to liquid heat capacity for organic species. Finally, we test the abilities of advanced equations of state on associating chemicals. Based on these findings, several new methods were developed, and an updated approach to the derivative method was recommended to DIPPR. We have taken significant steps forward in DIPPR's ability to predict these properties. However, this work does not fully solve the problem of association in thermodynamic properties. In addition to the above work, significant work was performed in the field of autoignition, biomechanical sensors, and design of materials for non-linear optics.

Bibliography: pages 191-202. / The surface heat balance of the Benguela upwelling area on the west coast of southern Africa is analysed. Measurements of the components of the heat balance were made in the St Helena Bay area from 14-21 October 1986. Additional long-term data was obtained from Alexander Bay and Cape Town. An average net heat gain of 227 W.m⁻² was received over the eight days of the field study. The presence of cold water determined that latent heat loss by the sea surface was small, while the sensible heat flux represented a small gain by the sea. These two turbulent heat fluxes are roughly equal and opposite and therefore approximately cancel each other. Use of a model, assuming idealised conditions, indicated that most turbulent heat exchange between the air and takes place in the nearshore region where air-sea contrasts are greatest. The net radiation was found to provide a good estimate of the total heat balance, thus the major contributing term to a high heat balance over the Benguela area is the input solar radiation. Minimal synoptic variation in the heat balance during the eight-day field programme was observed, but additional global radiation data analysed revealed that synoptic variations over the 3-6 day period are in fact more significant than the longer term seasonal variations. Both synoptic and seasonal variations in the heat balance are greater in the south than in the north. The high heat flux into the sea surface is capable of increasing the temperature of the upwelled water at a fairly rapid rate. During summer the heat exchange is capable of increasing the temperature of the upper 10 m mixed layer by as much as 0.65°C over one day. This input heat is used to realise the high biological potential of the upwelled waters.

Modifications to the quasistatic Carnot cycle are developed in order to formulate improved theoretical bounds on the thermal efficiency of certain refrigeration cycles that produce finite cooling power. The modified refrigeration cycle is based on the idealized endoreversible finite time cycle. Two of the four cycle branches are reversible adiabats, and the other two are the high and low temperature branches along which finite heat fluxes couple the refrigeration cycle with external heat reservoirs. This finite time model has been used to obtain the following results: First, the performance of a finite time Carnot refrigeration cycle (FTCRC) is examined. In the special case of equal heat transfer coefficients along heat transfer branches, it is found that by optimizing the FTCRC to maximize thermal efficiency and then evaluating the efficiency at peak cooling power, a new bound on the thermal efficiency of certain refrigeration cycles is given by $\epsilon\sb{m} = (\tilde\tau\sp2\sb{m}\ (T\sb{H}/T\sb{L}) - 1)\sp{-1},$ where $T\sb{H}$ and $T\sb{L}$ are the absolute high and low temperatures of the heat reservoirs, respectively, and $\tilde\tau\sb{m}=\sqrt{2}$ + 1 $\simeq$ 2.41 is the dimensionless cycle period at maximum cooling power. Second, a finite time refrigeration cycle (FTRC) is optimized to obtain four distinct optimal cycling modes that maximize efficiency and cooling power, and minimize power consumption and irreversible entropy production. It is found that to first order in cycling frequency and in the special symmetric case, the maximum efficiency and minimum irreversible entropy production modes are equally efficient. Additionally, simple analytic expressions are obtained for efficiencies at maximum cooling power within each optimal mode. Under certain limiting conditions the bounding efficiency at maximum cooling power shown above is obtained. Third, the problem of imperfect heat switches linking the working fluid of an FTRC to external heat reservoirs is studied. The maximum efficiency cycling mode is obtained by numerically optimizing the FTRC. Two distinct optimum cycling conditions exist: (1) operation at the global maximum in efficiency, and (2) operation at the frequency of maximum cooling power. The efficiency evaluated at maximum cooling power, and the global maximum efficiency may provide improved bench-mark bounds on thermal efficiencies of certain real irreversible refrigeration cycles.

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Computational thermodynamics is a powerful tool for solving practically important problems including the design of new materials and the analysis of their internal and external stability. This thesis contributes to computational thermodynamics by proposing several practical solutions to eliminate the so-called thermodynamic artifacts rather frequently found in thermodynamic assessments. First, a method is developed to eliminate the artifacts such as inverted miscibility gaps in the liquid phase at high-temperatures and reappearance of the liquid phase at low-temperatures or reappearance of a solid phase at elevated temperatures. This method is based on introducing a sufficiently dense mesh of knots (not related to experimental points utilized in the optimization) and ensuring that specific inequality conditions (topological constraints) governing the appearance of the phase diagram are satisfied in these knots. A feasibility of the approach proposed is exemplified by carrying out a re-optimization of the Mg-Sb system. Generally re-optimization of a system would take months to get the optimized results. Hence, to minimize time needed to get rid of artifacts, two different quick correction methods are developed to eliminate the unrealistic inverted miscibility gap in the liquid phase at elevated temperatures. Both methods employ optimization under topological constraints via controlling the sign of the second derivative of the Gibbs energy. Their applicability is exemplified on the Sn-Zr system. Also, a theoretical study was done on undulate phase boundaries. Usually, an inflection point on a phase boundary is considered as an unambiguous indication that one of the phases participating in the equilibrium is internally unstable, i.e., that it is prone to phase separation. It has been generally assumed that an inflection point may occur only if the thermodynamic model of this phase contains an excess Gibbs energy term. It is shown that in contrast to this assumption, inflection points on a phase boundary may appear when a pure solid component or a stoichiometric binary phase is in equilibrium with the ideal binary solution, which is internally stable. Finally, in addition to the theoretical analysis on undulate phase boundaries, a thermodynamic optimization is done on an imaginary A-B binary system subjected to topological constraints. Since, Thermo-Calc does not have the necessary tools to implement such topological constraints as d^2T/dx^2 >0 or d^2T/dx^2 <0. A Fortran 90 program was developed to make use of these constraints. / Thesis / Doctor of Philosophy (PhD)