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We have previously presented an associated lattice fluid equation of state (ALF EOS) and shown that the equation is able to predict the solubility of CO2 in polymers and, simultaneously, the extent of swelling of the polymer due to CO2 using a single parameter obtained from one solubility isotherm. In the present study, we show that cloud point curves in CO2 + polymer systems (at higher pressures) may also be predicted using the same value of the parameter. In addition, we show that the single parameter does not depend on temperature, pressure, or polymer molecular weight.

We have previously presented an associated lattice fluid equation of state (ALF EOS) and shown that the equation is able to predict the solubility of CO 2 in polymers and, simultaneously, the extent of swelling of the polymer due to CO 2 using a single parameter obtained from one solubility isotherm. In the present study, we show that cloud point curves in CO 2 + polymer systems (at higher pressures) may also be predicted using the same value of the parameter. In addition, we show that the single parameter does not depend on temperature, pressure, or polymer molecular weight.

We present a new model for the viscosity of molten salts based on the modified Rough-Hard-Sphere (RHS) scheme of DiGuilio and Teja. The model employs the properties of argon to obtain smooth-hard-sphere (SHS) viscosity, and the melting points of the molten salts as characteristic parameters. The performance of the model to correlate/predict the viscosities of 38 molten salts is examined in this work. Our results show that the viscosities of these molten salts can be correlated with an AAD (average absolute deviation between calculated and experimental values) of 1.50% using one adjustable parameter for each salt. In addition, values of the adjustable parameter exhibit regular trends with the melting point of the salt for a series of salts with a common anion.

The density, viscosity, and thermal conductivity of eight carboxylic acids (pentanoic, hexanoic, heptanoic, octanoic, nonanoic, decanoic, dodecanoic, and tetradecanoic acid) were measured at ambient pressure and temperatures ranging from (290.3 to 473.4) K. The expanded uncertainties (k = 2) of the measurements were estimated to be 0.2 kg·m–3 for the density, 0.04 mPa·s for the viscosity, and 0.003 W·m–1·K–1 for the thermal conductivity (at the 95% level of confidence). The data were correlated using the Rackett equation (in the case of the density) and a modified rough hard-sphere (RHS) model (in the case of the viscosity and thermal conductivity). Generalized forms of the RHS model parameters are presented as functions of the carbon number and temperature.

This work reviews thermodynamic models for the correlation and prediction of the phase behavior of CO2 + polymer systems. Advantages and shortcomings of cubic equation of state, the SAFT equation, and Lattice fluid models are discussed. Perspectives and future directions in the development of thermodynamic models for CO2 + polymer systems are presented.

Thermal conductivity data are reported for nanofluids consisting of 1–4 volume % bentonite particles dispersed in n-pentadecane, potentially for oil-based drilling fluids. The measurements were conducted at temperatures between 298 K and 393 K. The thermal conductivity increases with increasing nano particle concentration, attaining a maximum enhancement of 16.6% in nanofluids containing 4 volume % bentonite. The temperature behavior of the thermal conductivity in nanofluid follows closely that of the base fluid, i.e. n-pentadecane. The effect of temperature on the viscosity of nanofluids was also investigated. The viscosity decreases with increasing temperature at a constant nano particle volume fraction. As expected, the viscosity also increases with increasing nano particle concentration. Cloud point temperatures of nanofluids were measured as a function of particle volume fraction. Cloud point temperatures increases with increasing particle concentration, attaining a maximum increase of 3.10% in nanofluids containing 4 volume % bentonite. Correlations for the thermal conductivity and viscosity are presented for bentonite/n-pentadecane nanofluids with acceptable accuracy.

Although the existence of Lewis acid–base interactions between CO 2 and electron donating functional groups in polymers can be determined from the vibrational spectra of the polymers in question, only a few quantitative estimates of the strength of such interactions have been reported. We have previously reported values of the enthalpy of association between CO 2 and the carbonyl group in polymers from the bending vibrations of CO 2 . In the present work, we extend these measurements to other functional groups and relate the strength of these interactions to the structure of the polymer.

The thermal conductivity of NH 3 + LiNO 3 and NH 3 + LiNO 3 + H 2 O mixtures with an ammonia mass fraction between 0.3 and 0.6 was measured at temperatures from 303.15 K to 353.15 K at 1.5 MPa, using a relative transient hot wire apparatus. The apparatus and method were validated by comparing the measured values of the thermal conductivity of pure water, toluene, dimethyl phthalate, ethylene glycol and water + lithium nitrate with published values. Uncertainty in the measurements was estimated to be less than 0.025 W m −1 K −1 . The measured NH 3 + LiNO 3 thermal conductivity was compared with the literature, showing significant differences. Finally, the experimental data was fitted with a comprehensive model based on the local composition concept.

Anewmodelbasedonroughhard-spheretheoryisproposedforthethermal conductivity of molten salts. The model incorporates a smooth hard-sphere contribu- tion using the properties of argon, as well as characteristic parameters based on the melting point of the molten salt. It is demonstrated that it is possible to correlate the thermal conductivity of monovalent and multivalent molten salts within experimen- tal error using this approach. Furthermore, in salts with a common anion, the single adjustable parameter in the model exhibits regular behavior with the molecular weight ofthesalt.Itisalsoshownthatthethermalconductivityofseveralmolten-saltmixtures can be predicted without any mixture parameters.

We describe an extension of the Associated Lattice–Fluid (ALF) Equation of State (EOS) for correlating/predicting the volumetric and phase behavior of CO2 + imidazolium-based ionic liquid (IL) systems over a wide range of temperatures and pressures. The EOS is based on the Guggenheim-Huggins-Miller lattice fluid partition function and includes a contribution for specific interactions between CO2 and CO2-philic functional groups in the IL. Although two adjustable parameters are incorporated in the model, these parameters do not depend on temperature or pressure. Furthermore, one of the parameters can be obtained via enthalpy of absorption measurements. The remaining parameter in the ALF EOS requires only one solubility isotherm for correlating/predicting both phase equilibrium and volumetric properties of CO2 + IL systems over a wide range of conditions.

A new associated lattice-fluid equation of state is derived for CO2 + polymer mixtures by incorporating complex formation in the Guggenheim–Huggins–Miller lattice-fluid partition function. The equation contains mixture parameters that must be obtained from experimental data but are independent of the temperature and pressure. Moreover, one of the parameters may be obtained via in situ attenuated total reflection Fourier transform infrared measurements. The solubilities of CO2 in several polymers were correlated over a wide range of temperatures and pressures using only one adjustable parameter. The extent of swelling of the polymers due to the addition of CO2 could then be predicted without any additional parameters.

Three eutectic salts from a system of halide salts NaCl–KCl–ZnCl2 were chosen for detailed study of thermal and transport properties with the objective of developing a next generation high-temperature heat-transfer fluid (HTF) for concentrated solar thermal power (CSP) technology. The acceptable range of the working temperatures for the HTF is from below 250 °C to at least 800 °C. The tested properties are presented here for the three candidate eutectic salts, including melting point, heat of fusion, heat capacity, vapor pressure, viscosity, density, and thermal conductivity. Data-fitted equations are provided for all the measured properties for convenience in engineering application. It is concluded that the three eutectic salts can satisfy the needs for a high-temperature HTF and thus are recommended as a new generation high-temperature HTF.

The solubilities of solid benzoic acid in mixtures of CO2 + hexane have been measured at temperatures ranging from (308 to 338) K, pressures ranging from (10 to 35) MPa, and cosolvent concentration...

We have identified new organosilicon coolants for direct immersion phase change cooling of electronic systems using a computer-aided molecular design (CAMD) approach combined with a figure of merit (FOM) analysis (hereafter termed the CAMD-FOM approach). Seven candidates with predicted thermophysical properties in the range suitable for direct immersion cooling of electronics were identified, and the thermophysical properties of two candidates, dimethoxydimethylsilane and ethyldimethylsilane, were measured in order to validate the CAMD-FOM procedure. In addition, the pool boiling characteristics of a mixture of dimethoxydimethylsilane and HFE 7200 (10:90 w/w) on a grooved silicon surface were investigated and compared with those of pure HFE 7200. The addition of dimethoxydimethylsilane was shown to lead to an approximately 20% enhancement in the critical heat flux, confirming that the CAMD-FOM approach can be employed for designing new heat transfer fluids.

We describe the use of computer-aided molecular design (CAMD) and figure of merit (FOM) analysis to identify new heat transfer fluids for direct immersion cooling of electronic systems. Thirty-five new fluids, with thermophysical properties in the range 320 K 0.09 W m−1 K−1 and Hvap > 35 kJ mol−1, were identified via a CAMD approach. Further analysis of these 35 fluids led to the selection of 1,1,1-trifluoro-3-methylpentane (C6H11F3) for experimental evaluation. C6H11F3 was synthesized from commercially available precursors, and its thermophysical properties were measured to verify its FOM. Next, the pool boiling performance of a mixture of 7 wt.% C6H11F3 + 93 wt.% HFE 7200 was determined using a 10 mm × 10 mm grooved Si thermal test chip coated with copper. An improvement of 7% in the critical heat flux (CHF) was obtained, suggesting that C6H11F3 is worth further examination as a candidate for direct immersion phase change cooling applications.

The density, viscosity, and thermal conductivity of 1-ethoxy-1,1,2,2,3,3,4,4,4-nonafluorobutane (HFE 7200) + methanol and HFE 7200 + 1-ethoxybutane were measured at ambient conditions and correlated using a modified rough hard-sphere model. Rough hard-sphere parameters of pure HFE 7200 and pure 1-ethoxybutane were obtained by fitting measured values of their thermal conductivities at several temperatures. The rough hard-sphere model was able to reproduce the thermal conductivity and viscosity behavior of the HFE 7200 + 1-ethoxybutane system very well (average absolute deviations of about 2 %), but average deviations between calculated and experimental values were about 10 % in the case of the thermal conductivity and viscosity of HFE 7200 + methanol mixtures.

Computer-aided molecular design and figure of merit analysis were used to screen mixture formulations that enhance the pool boiling heat transfer performance of Novec fluid HFE 7200. Mixtures of HFE 7200 with methanol and ethoxybutane were identified as promising candidates for further study, and their thermophysical and dielectric properties were measured. The pool boiling performance of the two mixtures was investigated on a 1 cm × 1 cm silicon substrate with copper nanowire arrays. The addition of both methanol and ethoxybutane to HFE 7200 resulted in a substantial increase in the critical heat flux. However, the addition of methanol had a detrimental effect on incipience superheat and heat transfer coefficient, whereas these properties only changed marginally upon the addition of ethoxybutane to HFE 7200. This suggests that HFE 7200 + ethoxybutane mixtures show promise as candidates for direct immersion cooling of electronics.

We have studied the precipitation and growth of magnesium hydroxide Mg(OH) 2 nanopetals on zeolite 4A particles dispersed in aqueous magnesium chloride solutions at 298 K. We show that the precipitation of these petal-like nanostructures can be achieved by the addition of ammonium hydroxide to aqueous magnesium chloride, and their growth can be controlled by concentration and pH. We propose a mechanism for nanocomposite formation driven by acid–base interactions between the bridging hydroxyl groups on the zeolite surface and weakly basic Mg(OH) 2 .

We have used in situ ATR-FTIR measurements to provide estimates of the strength of specific interactions between carbon dioxide (CO2) and carbonyl groups in polymers such as poly(methyl methacrylate) (PMMA), poly(vinyl acetate) (PVAc), poly(lactide) (PLA) and poly(lactide-co-glycolide) (PLGA). Polymer films were exposed to high pressure CO2 and the carbonyl stretching vibration at 1700 cm−1 and the CO2 bending mode at 660 cm−1 were studied. The observed shift in the carbonyl stretching band to higher wavenumber was attributed to dielectric effects according to the Kirkwood–Bauer–Magat (KBM) equation. On the other hand, the splitting of the CO2 bending mode provided direct evidence of specific interactions between the polymer and CO2. These interactions were quantified via an equilibrium constant for the association reaction between CO2 and the carbonyl group.

The precipitation and self-assembly of magnesium hydroxide Mg(OH)2 nanopetals on dispersed zeolite 4A particles was investigated. Mg(OH)2/zeolite nanocomposites were produced from magnesium chloride solutions and characterized via X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR), and solid state NMR. It was determined that Mg(OH)2 interacted with bridging hydroxyl protons (SiOHAl) on the zeolite surface, but not with silanol or aluminol groups. NMR analysis showed that 13% of the tetrahedral Al sites on the zeolite were converted to octahedral Al. The zeolite structure and crystallinity remained intact after treatment, and no dealumination reactions were detected. This suggests that the deposition–precipitation process at ambient conditions is a facile method for controlling Mg(OH)2 nanostructures on zeolites.

This work reviews experimental data and models for the thermal conductivity of nanoparticle suspensions and examines the effect of the properties of the two phases on the effective thermal conductivity of the heterogeneous system. A model is presented for the effective thermal conductivity of nanofluids that takes into account the temperature dependence of the thermal conductivities of the individual phases, as well as the size dependence of the thermal conductivity of the dispersed phase. We demonstrate that this model can be used to calculate the thermal conductivity of nanofluids over a wide range of particle sizes, particle volume fractions, and temperatures. The model can also be used to validate experimental thermal conductivity data for nanofluids containing semiconductor or insulator particles and confirm the size dependence of the thermal conductivity of nanoparticles. © 2010 American Institute of Chemical Engineers AIChE J, 2010

We have recently proposed a compressible lattice model for CO 2 + polymer systems in which CO 2 forms complexes with one or more functional groups in the polymer. Furthermore, we have shown that this model is able to simultaneously correlate phase equilibria, sorption behavior, and glass transition temperatures in such systems. In the present work, we extend the model to ternary CO 2 + cosolvent + polymer systems and demonstrate that cloud point behavior in CO 2 + dimethyl ether + poly ( ɛ -caprolactone), CO 2 + dimethyl ether + poly (isopropyl acrylate), and CO 2 + dimethyl ether + poly (isodecyl acrylate) systems can be predicted using parameters obtained from binary data. Our results also suggest that dimethyl ether may form weak complexes with poly ( ɛ -caprolactone), poly (isopropyl acrylate), and poly (isodecyl acrylate).

We demonstrate the application of a compressible lattice model to the correlation of cloud point behavior in CO2 + fluorinated polymer systems. The model uses two adjustable parameters that are temperature, pressure, and molecular weight independent and is able to correlate cloud point behavior within experimental uncertainty (AAD of ∼2 %). We infer from the values of the parameters obtained that weak complexes exist in these systems, and these complexes have an appreciable effect on cloud point behavior. However, the model cannot separate the effects of complex formation from free volume effects since the enthalpy of association apparently follows the same trends as the free volume of the polymer in these systems.

We extend a previously published compressible lattice model to the prediction of glass-transition temperatures in CO2 + polymer systems. We have applied the model to published data as well as to new measurements of glass-transition temperatures in CO2 + poly(methyl methacrylate) (PMMA) and CO2 + poly(lactic acid) (PLA) systems. We demonstrate that the model is able to predict glass-transition temperatures in CO2 + polymer systems using a parameter that is obtained from sorption data and a second parameter that is obtained from FTIR measurements. The parameters are not dependent on temperature, pressure, or polymer molecular weight.

We present new data on the thermal conductivity of nanofluids consisting of alumina nanoparticles dispersed in water, ethylene glycol, and ethylene glycol + water mixtures. We also demonstrate that our previously published model is able to describe the temperature, particle size, and particle volume fraction dependence of these nanofluids without any adjustable parameters, irrespective of the base fluid used (water, ethylene glycol, or water + ethylene glycol mixtures). Furthermore, we demonstrate how the model may be used to check the consistency of literature data on all alumina nanofluids.

A method based on the rough-hard-sphere theory has been extended to the calculation of the viscosity and thermal conductivity of a wide range of compounds including alkanes, 1-alkanols, alkanediols, benzene, toluene, and 11 refrigerants. The method is simple to use and is capable of fitting data within experimental error. Generalized forms of the parameters for homologous series of alkanes, 1-alkanols, alkanediols, and halogentated methanes are presented. The extrapolation capability of the method was evaluated by predicting the viscosities of the higher alkanes and alkanols using parameters obtained from the properties of lower members of the homologous series.

Magnetic nanoparticles exhibit many interesting properties that can be exploited in a variety of applications such as catalysis and in biomedicine. This review discusses the properties, applications, and syntheses of three magnetic iron oxides – hematite, magnetite, and maghemite – and outlines methods of preparation that allow control over the size, morphology, surface treatment and magnetic properties of their nanoparticles. Some challenges to further development of these materials and methods are also presented.

The properties of nanocomposites obtained by depositing iron oxide nanoparticles in the pores of two types of commercial activated carbon pellets using supercritical water were studied as a function of process variables. The loading of iron oxide nanoparticles in the nanocomposites increased with precursor concentration and immersion time, but was apparently unaffected by the temperature. The specific surface area and pore volume of the nanocomposites decreased with increased loading of the nanoparticles, possibly due to pore blockage and/or pore destruction resulting from acid attack during processing. The results suggest that an optimum loading of nanoparticles in the nanocomposites can be achieved by manipulating pellet dimensions, precursor concentration, and immersion time.

Henry’s constants of 2-propanone, 2-butanone, 2-pentanone, 2-hexanone, and 2-heptanone in aqueous solutions containing inorganic salts or quaternary ammonium salts were determined at temperatures between 313 and 343 K, and salt ionic strengths below 5.0. Our data show that inorganic salts generally salt-out the 2-ketones, whereas quaternary ammonium salts generally salt-in the 2-ketones. However, 2-propanone is salted-out by both types of salts. We have also extended a published model based on dilute solution theory to solutions containing two inorganic salts, as well as to solutions containing quaternary ammonium salts. We show that it is possible to correlate all data for salting-out behavior using a single salt-effect parameter for each system. Salting-in behavior can also be correlated with a single parameter, although agreement with experiment is not as good as in the case of salting-out behavior. This is because the model does not explicitly account for the role of dispersion forces in these systems...

Factors that affect the size, size distribution, and morphology of α-Fe 2 O 3 nanoparticles obtained via continuous hydrothermal synthesis have been investigated in this work. The presence of polyvinyl alcohol (PVA) during synthesis is shown to limit the aggregation of particles and to produce narrow particle size distributions than in the case when PVA is absent. Narrow particle size distributions are also obtained with an increase in PVA concentration, beyond a minimum concentration required to cover all particles with a polymer layer. The average particle size is shown to increase with temperature and residence time, and is accompanied by morphology changes in some cases. Both modeling and experimental studies indicate that equilibrium species distributions do not affect the particle morphology, so that changes in morphology in this work are probably due to kinetic phenomena.

We have investigated the continuous hydrothermal synthesis of lithium iron phosphate (LiFePO4) nanoparticles by reacting iron sulfate, phosphoric acid, and lithium hydroxide in a flow system. The effects of temperature, flowrate of water, and reactant concentration on the size and morphology of particles were investigated. In general, particle size increased with temperature and with increasing reactant concentration. Particle morphology, on the other hand, became more regular at high flowrates of water. Possible reasons for this behavior are given, and differences with batch hydrothermal synthesis of LiFePO4 are highlighted. The different mechanisms in the two methods results in much smaller and more uniform particles being obtained in continuous hydrothermal synthesis than via batch hydrothermal synthesis.

We present a compressible lattice model for representation of both low-pressure and high-pressure phase equilibria in CO2 + polymer systems. The model explicitly accounts for weak complex formation in these systems, using two parameters that are obtained by fitting experimental cloud point pressures or sorption equilibria. In addition, one of these parameters may be obtained from Fourier transform infrared (FTIR) spectroscopy measurements. We demonstrate the application of this model to the prediction of low-pressure sorption behavior in the CO2 + poly(vinyl acetate) (PVAc) system, using parameters obtained from high-pressure cloud point data. In addition, we show that we are able to predict the sorption behavior of CO2 + PLGA copolymer systems using a single parameter obtained from CO2 + poly(lactic acid) (PLA) cloud point data, together with enthalpies of association obtained from FTIR measurements.

A modified version of the rough hard sphere (RHS) scheme of Gacino et al. has been used to correlate the viscosity and thermal conductivity of ILs. A total of 661 viscosity data at 0.1 MPa for 48 ILs, and 159 thermal conductivity data at 0.1 MPa for 26 ILs were correlated, with average absolute deviations between calculated and experimental values (AAD) of 1.15 % in the case of the viscosity and 2.32 % in the case of the thermal conductivity. In addition, a total of 453 viscosity data for 10 ILs and 95 thermal conductivity data for 9 ILs over a pressure range of 0.1 MPa to 35.6 MPa were correlated with AADs of 3.46 % in the case of the viscosity and 2.89 % in the case of the thermal conductivity. More importantly, the three parameters of the modified RHS scheme were found to exhibit regular trends with the molecular weight of ILs with a common anion. Finally, IL mixture viscosities were predicted within their experimental uncertainties using a simple mixing rule. Mixtures of water and ILs could also be accommodated within the RHS scheme, although errors were higher in this case.

We have measured the Henry’s constants of several components of gasoline, including methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), toluene, ethylbenzene, and o-xylene in pure water and in 0.5 and 1.0 m solutions of sodium chloride. The data were obtained at four temperatures between 313 and 343 K using differential headspace gas chromatography. We have also correlated our data using a previously derived expression based on dilute solution theory. The expression contains one salt-effect parameter that is obtained by regressing data at one salt concentration, thus allowing extrapolation to other salt concentrations. We show that the salt-effect parameter can be replaced by published values of the Setchenov constant for the system of interest. It has been suggested that the salt effect should increase with the size of the volatile organic compound, at least within a homologous series of compounds. However, our data do not validate this hypothesis.

Henry's constants of volatile organic compounds (VOCs) in 58 systems containing water and one or more salts have been correlated using a thermodynamic model based on dilute solution theory. Several classes of VOCs were studied, including the 2-ketones, 1-alkanols, tert-butyl ethers, organic sulfides, aromatic hydrocarbons, and chlorinated organics. Henry's constants in 39 of these systems were measured in our laboratory using a single experimental technique that provided internally consistent data for the development of models. Both salting-out and salting-in behavior were observed in the systems studied, and we were able to correlate all data within experimental error using the dilute solution model and one ternary salt-effect parameter. This parameter was found to increase linearly with the size of the VOC within a homologous series when the VOC was salted-out by the addition of salt, and to decrease linearly with size when the VOC was salted-in. Henry's constants of light gases (methane and nitrogen) were also correlated over a wide range of temperatures, pressures, and salt concentrations using a Krichevsky–Kasarnovsky type extension of the dilute solution theory. When the extended model was used to estimate methane losses from produced water tanks, our estimates were significantly different from published calculations, emphasizing the need for experimental data when salts are present.

CO 2 + polymer phase behavior is of interest in a number of applications, including the precipitation of polymer particles for drug delivery and the deposition of fluoropolymer films. There is experimental evidence to suggest that CO 2 forms weak complexes with carbonyl groups in these polymers, and it has also been suggested that specific interactions between CO 2 and the lone pair of electrons on fluorine in a C–F bond contribute to the high solubility of CO 2 in these fluropolymers. In the present work, therefore, we have quantified the strength of weak complexes in CO 2 + poly(lactide- co -glycolide) (PLGA) systems using in situ FTIR spectroscopy; and calculated cloud points in these systems using the measured FTIR spectra combined with a modified lattice model. We demonstrate that this model is able to predict the phase behavior of CO 2 + PLGA copolymer systems using only one parameter obtained from a reference system (CO 2 + low molecular weight PLA in our case). Finally, we have extended the model to the calculation of phase behavior in CO 2 + poly(fluroalkyl acrylate) systems, and show that the results may be used to infer the existence of weak CO 2 –C–F complexes in these systems.

The thermal conductivities of several nanofluids (dispersions of alumina nanoparticles in ethylene glycol) were measured at temperatures ranging from 298 to 411 K using a liquid metal transient hot wire apparatus. Our measurements span the widest range of temperatures that have been investigated to date for any nanofluid. A maximum in the thermal conductivity versus temperature behavior was observed at all mass fractions of nanoparticles, closely following the behavior of the base fluid (ethylene glycol). Our results confirm that additional temperature contributions inherent in Brownian motion models are not necessary to describe the temperature dependence of the thermal conductivity of nanofluids. Our results also show that the effect of mass or volume fraction of nanoparticles on the thermal conductivity of nanofluids can be correlated using the Hamilton and Crosser or Yu and Choi models with one adjustable parameter (the shape factor in the Hamilton and Crosser model, or the ordered liquid layer thickness in the Yu and Choi model).

Iron oxide (α-Fe 2 O 3 ) nanoparticles were deposited on the surface and in the pores of activated carbon pellets using supercritical water to synthesize the particles from a precursor solution of ferric nitrate. The dispersion of the particles in the activated carbon was found to depend mainly on the immersion time in the precursor solution at room temperature. Two types of dispersions were obtained: egg-shell dispersions at low immersion times and uniform dispersions at high immersion times. The particle size and size distribution, on the other hand, were influenced mostly by precursor concentration. Although the catalytic properties of the α-Fe 2 O 3 in AC composites were not evaluated, the procedure of employing supercritical water to deposit metal oxide particles on hydrophobic surfaces inside support structures offers promise for carbon-supported catalyst preparation without the use of toxic or noxious solvents.

Henry's constants of the homologous series of 2-ketones from 2-propanone to 2-heptanone were measured in aqueous solutions containing sodium chloride from (0.2 to 1.2) m (molal) over a range of temperatures from (313 to 363) K. In addition, Henry's constants of the n-alkanols from ethanol to 1-hexanol in aqueous solutions with sodium sulfate from (0.2 to 1.2) m were also measured over the same temperature range. The data were correlated using a model based on dilute solution theory that contains one temperature-independent salt effect parameter. A linear relationship between this parameter and the critical volume of the volatile organic compound (VOC) was found for each homologous series studied in this work.

Two synthesis routes for the production of LiFePO4 particles were investigated in water at subcritical and supercritical conditions. Micron and nano-sized particles of LiFePO4 were obtained via both routes, with nano-sized particles predominating when temperature was above the critical temperature of water. Our results suggest that synthesis in supercritical water is attractive for obtaining nanometer-sized crystalline particles of LiFePO4 with a low degree of agglomeration. Electrochemical tests showed that this material exhibited improved capacity compared with LiFePO4 prepared via other methods.

Conducting composites (∼3 mm in thickness) of polypyrrole (PPy) and porous crosslinked polystyrene (PCPS) were prepared by first impregnating PCPS with iodine (I 2 ), and then contacting it with pyrrole (Py). Both these steps were carried out with and without supercritical carbon dioxide. The use of supercritical CO 2 as a solvent for I 2 and Py facilitated the transport and deposition of these substances in the pores of the permanently porous host and produced composites with conductivities as high as 10 −3 S cm −1 . Moreover, the deposition of I 2 in the pores could be controlled via the CO 2 pressure. The bulk and surface conductivities of the composite exhibited percolation behavior with respect to the amount of the I 2 deposited, whereas the volume conductivity exhibited a stepwise transition at approximately 100 wt% PPy+I 2 complex formed (with respect to the original mass of PCPS). Optical micrographs suggest that non-uniform distributions of PPy are obtained in the pores below this transition. The percolation threshold was as low as 10 wt% so that the stability and mechanical strength of the composites were approximately the same as those of the host PCPS. This was verified by TGA and compressive strength measurements. The temperature dependence of the conductivity conformed with Mott's variable-range hopping (VRH) model for three-dimensional electronic transport. However, the data could be correlated equally well with the CELT model.

A model based on dilute solution theory is extended to Henry's constants of gases and volatile organic compounds in aqueous solutions, with and without added salts. The model is applicable to salt solutions over significant ranges of temperature, pressure, and salt concentration, up to the solubility limit of the salts considered in this work. Extrapolation over a range of salt concentrations requires one salt-dependent parameter, which can be approximated by the Setchenov constant at 298 K. As a result, literature or predicted values of Setchenov constants at a single temperature can be used to obtain Henry's constants over a range of temperatures and salt concentrations. Extrapolation in pressure was achieved using an expression that is similar to the Krichevsky–Kasarnovsky equation, with the partial molar volume of the gas or VOC at infinite dilution in water treated as an adjustable parameter. Regressed values of this parameter were found to be in good agreement with experimental partial molar volumes for methane + water and methane + water + salt systems at pressures up to 1000 bar. Therefore, it appears feasible to extrapolate Henry's constant data for gases or VOCs in water to aqueous salt solutions over significant ranges of pressures, temperatures, and salt concentrations, provided data on the Setchenov constant at 298 K and the partial molar volume of the VOC at infinite dilution in water are available.

Composites of polypyrrole (PPy) and porous cross-linked polystyrene (PCPS) were prepared using a two-step batch method proposed by Ruckenstein and Park. However, the solvent employed by Ruckenstein and Park (methanol) in the polymerization step of their method was replaced with supercritical CO2. For comparison purposes, PPy/PCPS composites were also prepared using no solvent in the polymerization step. Conductivities as high as 10−2 S cm−1 were obtained, with or without the use of supercritical CO2. Uniformity of conductivity was determined via surface and bulk conductivity measurements, as well as by a new volume conductivity measurement that provides a measure of spatial (three-dimensional) distribution of the conducting component in the composite. The conductivity of composites prepared with or without the use of supercritical CO2 conformed to the same percolation behavior with respect to the amount of PPy formed. The percolation threshold in all cases was as low as 4 wt.%. The mechanical strength of the composites was found to be about the same as that of the host PCPS, as was the thermal stability. Therefore, the conductive component did not appear to adversely affect these properties of the host. Finally, the temperature behavior of the conductivity could be correlated with Mott's variable-range hopping (VRH) model for three-dimensional electronic transport.

The effect of temperature, pH, time, and reactant concentrations on the size and morphology of lithium iron phosphate (LiFePO4) particles synthesized in a batch hydrothermal reactor was investigated in this work. It was found that LiFePO4 could only be synthesized at neutral or slightly basic pH in both subcritical and supercritical water. Synthesis in subcritical water resulted in micron-sized particles of high crystallinity, whereas synthesis in supercritical water produced submicron particles. A more uniform particle size distribution was obtained at low reactant concentrations, irrespective of the synthesis temperature. Qualitative explanations for these observations are provided in terms of nucleation, growth, and agglomeration phenomena at subcritical and supercritical conditions.

A relative headspace gas chromatographic method is described for the measurement of Henry's constants of volatile organic compounds (VOCs) in aqueous salt solutions. The method requires the Henry's constant of the VOC in pure water, and employs larger liquid samples than conventional headspace techniques in order to minimize errors arising from solute mass loss from the liquid phase. Henry's constants of five methyl ketones (2-propanone, 2-butanone, 2-pentanone, 2-hexanone, and 2-heptanone) in 0.2 M (molal) to 1.0 M sodium sulfate solutions were measured using the relative method at temperatures between 50 and 80 °C. Reference values of Henry's constants of the five methyl ketones in pure water were measured using a differential headspace technique. The entire data set was correlated using an equation containing three parameters (obtained from VOC + water data) and a single salt parameter. The equation was able to successfully extrapolate Henry's constant data over the entire range of salt concentrations.

Solid-liquid equilibrium data are reported for L-isoleucine (L-ILE) + L-valine (L-VAL) + water at 298 K and ambient pressure, using experimental techniques that involve (a) cooling of an aqueous solution of the two amino acids until crystals are formed, or (b) the addition of one amino acid to an undersaturated aqueous solution of the other amino acid until any added crystals remain undissolved. The compositions of the phases in the two types of experiments were obtained by HPLC analysis. Solid phases were also analyzed by powder X-ray diffraction (XRD). The results show that, in the L-ILE + L-VAL + water system, homogeneous solid solutions are obtained in cooling crystallization experiments (method a), whereas isothermal experiments (method b) generally yield inhomogeneous solids. This suggests that literature data from isothermal experiments may not always represent true equilibrium values, especially when the solutes being crystallized are isomorphous or near-isomorphous, as in the case of the amino acids studied in this work.

A lattice-based model for solutions with solute–solvent association is extended to the calculation of phase equilibria in polymer–CO2 systems in this work. The model is simple to use and requires a maximum of two adjustable parameters to correlate both cloud point and sorption data. Moreover, we show that one of these parameters can be obtained from spectroscopic data. Application of the modified model is demonstrated for the calculation of cloud point curves of seven polymer–CO2 systems. Good agreement with experiment was obtained, with average deviations between calculated and experimental data of 1.3%. The predictive capabilities of the model are demonstrated by calculating the sorption behavior of CO2 in polymers using parameters from cloud point data.

Solid–liquid equilibria in the system l -leucine + l -valine + water have been measured at 298 K and ambient pressure. The system was shown to form solid solutions at equilibrium. The data also showed that the equilibrium composition of l -leucine in the liquid phase was only slightly affected by the presence of l -valine; whereas, the equilibrium composition of l -valine increased significantly with the addition of l -leucine. A simple thermodynamic model was used to correlate binary l -leucine + water and l -valine + water solubility data, and then to estimate nonidealities in the solid phase in the ternary system. Surprisingly, the solid solution exhibited significant nonidealities, emphasizing the need for analysis of the solid phase when ternary solubilities are measured.