Electrodeposition of copper in the presence of an acoustically excited gas bubble

Copper has been electrodeposited in the presence of an acoustically excited gas bubble (Ar bubbles with radii ∼1.5 mm held below a copper plate). Under the conditions employed, an acoustic pressure amplitude of 69.5 Pa is sufficient to excite multiple surface wave modes on the bubble wall. This is observed using high-speed imaging. This oscillation generates significant micromixing, which brings fresh electrolyte to the electrode surface leading to an enhanced deposition current. Scanning electron microscopy reveals radial streaming patterns in the resulting copper deposit. Experiments carried out using a lower acoustic pressure amplitude of 50.5 Pa (such that only the Faraday wave is excited) exhibit a lesser degree of streaming and mass transfer enhancement. No significant spatially averaged current enhancement is seen if the bubble is only undergoing breathing mode oscillation.     

Recovery of a multicomponent,single phase aerosol with a difference in vapor pressures entrained in a large air flow

Effective heat transfer coefficients and mass transfer rates were determined at varying compositions of steam with 1.5% by weight volatile oils entrained in an air flow. The mixture of volatile oils is comprised of 50% menthol, 25% menthone, and other fractions of essential oils. The rate of transient mass transfer, relative partial pressures and the liquid phase resistances were used to evaluate recovery mechanisms for the volatile oils in the entrained aerosol. The size of the aerosol was (600 ± 50) μm. A stainless steel tube and shell condenser and a direct contact condenser were constructed in order to evaluate unsteady state models for mass transfer of the volatile oils, the unsteady state heat transfer, and the percent recovery of the aerosol. These data will be invaluable in the development of a collection and condensation system for the continuous microwave processing of mint hay. The Solvent Free Microwave System? vaporizes water and essential oils directly from cut hay. The coupled ionized interior of the microwave applicator seeds ions in the gas phase which provide a ready platform for aerosol nucleation of the steam in the air mixture. This aerosol must be recovered at an efficiency which rivals steam distillation.     

The effect of temperature and pressure on acoustic and thermodynamic properties of 1,4-butanediol. The comparison with 1,2-, and 1,3-butanediols

The speeds of sound in 1,4-butanediol have been measured in the temperature range from (298 to 318) K at pressures up to 101 MPa by the pulse-echo-overlap method. The densities have been measured in the temperature range from (293.15 to 353.15) K under atmospheric pressure with a vibrating tube densimeter. Based on the experimental results, the densities, isobaric heat capacities, isobaric coefficients of thermal expansion, isentropic and isothermal compressibilities, as well as the internal pressure as function of temperature and pressure have been calculated. The effects of pressure and temperature are discussed and compared with the previous results for 1,2- and 1,3-butanediols.     

Isobaric specific heat capacity of typical lithium chloride liquid desiccants using scanning calorimetry

Three kinds of lithium chloride desiccants were selected, which are considered to be potential and interesting working fluids for a desiccant/dehumidification or absorption refrigeration system, and their isobaric specific heat capacities were determined in this context. Experiments were conducted at a high accuracy twin-cell scanning calorimeter. The temperature accuracy and heat flux resolution of the calorimeter are ±0.05 K and 0.1 μW respectively. The data of lithium chloride + water and lithium chloride + triethylene glycol (TEG)/propylene glycol (PG) + water systems were achieved at temperatures from 308.15 K to 343.15 K and atmospheric pressure. The mass fraction of LiCl ranged from 15% to 45% in the LiCl + H₂O system, and the mass fraction of LiCl and glycol ranged from 10% to 23.3% and 20% to 46.7% in the ternary systems respectively. Based on the experimental heat capacity data, a universal empirical formula was correlated as a function of temperature and solute mass fraction. In the experimental mass fractions and temperatures range, the average absolute deviation (AAD) between experiment results and calculated values is no more than 0.15%, and maximum absolute deviation (MAD) is within 0.38%. These thermodynamic data of lithium chloride solutions can be effectively used for analysis and design of desiccant/dehumidification systems and absorption refrigeration systems in both refrigeration and chemical industry.     

Thermodynamic characterization of the mixture (1-butanol + iso-octane): Densities,viscosities, and isobaric heat capacities at high pressures

The densities at high pressures of 1-butanol and iso-octane were measured in the range (0.1 to 140) MPa at seven different temperatures, from (273.15 to 333.15) K, and their mixtures were measured in the range (0.1 to 50) MPa at four different temperatures, from (273.15 to 333.15) K. The measurements were performed in a high-pressure vibrating tube densimeter. The pressure–volume–temperature behavior of these compounds and their mixtures was evaluated accurately over a wide range of temperatures and pressures. The data were successfully correlated with the empirical Tamman–Tait equation. The experimental data and the correlations were used to study the behavior and the influence of temperature and pressure on the isothermal compressibility and the isobaric thermal expansivity.Also, the isobaric heat capacities were measured over the range (0.1 to 25) MPa at two different temperatures (293.15 and 313.15) K for the pure compounds and their mixtures. The measurements were performed in a high-pressure automated flow calorimeter. The excess molar heat capacities were assessed for the mixture and a positive deviation from the ideality was obtained.     

Heat capacity of hafnia at low temperature

The low temperature (2 to 300) K heat capacity of monoclinic hafnia (HfO₂) was measured using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS). The thermodynamic functions in this temperature range were derived by curve fitting. The standard entropy and enthalpy of hafnia at T = 298.15 K was calculated to be 56.15 ± 0.57 J · mol^?1 · K^?1 and 9.34 ± 0.09 kJ · mol^?1, respectively. The results are in fairly good agreement with old data, which only covered temperatures from (50 to 298) K. Hafnia has a higher heat capacity than zirconia at all temperatures from (2 to 300) K.     

Model of hydrogen permeation behavior in palladium membranes

A model has been constructed for H₂ permeation through Pd which accounts for external mass transfer, surface adsorption and desorption, transitions to and from the bulk metal, and diffusion within the metal. Reasonable values for all rate parameters have been estimated based on surface science and membrane literature. In the absence of external mass transfer resistance, nearly diffusion-limited permeation is expected for clean Pd for temperatures above approximately 573 K and membrane thicknesses down to 1 μm. Low-temperature permeation is limited by desorption while adsorption is only expected to impact permeation at very low upstream H₂ partial pressures, or under conditions of substantially reduced sticking due to surface contamination. The efficiency of external gas-phase mass transfer is a critical element in permeation flux and apparent Sievert's law behavior for Pd membranes approaching 10 μm and thinner, especially at low H₂ partial pressures or when a porous support is present. Comparison of the calculations with literature results for Pd membranes less than 10 μm thick reveals that permeation rates well below those expected are often observed, indicating the importance of factors related to fabrication methods, such as film microstructure, grain size, and surface or grain boundary contamination.     

Comparison between filtrations at fixed transmembrane pressure and fixed permeate flux: application to a membrane bioreactor used for wastewater treatment

Membrane bioreactors for wastewater treatment must operate for long periods without chemical cleaning. This paper investigates the critical flux concept introduced by Field et al. as a means for achieving this goal. Experiments were conducted on a membrane bioreactor containing 600 l of activated sludge, equipped with a 0.25 m² ceramic membrane and located in Compiegne wastewater treatment plant. Hydraulic retention time was set at 24 h and sludge retention time at 60 days, so that suspended solids concentration stabilises at 10 g/l. We conducted two series of tests: at fixed transmembrane pressure (TMP) and at fixed permeate flux, set by a volumetric pump on the permeate. In both cases, velocity was varied from 1 to 5 m/s. In fixed flux tests, the flux was increased by 10 l/h m² increments and the TMP was observed to rise moderately first and then stabilise in about 15 min until a critical value of the flux is reached. Above this critical flux, the TMP rises rapidly and does not stabilise, as in dead-end filtration. The critical flux was found to increase approximately linearly with velocity, reaching about 115 l/h m² at 4 m/s. These data were reproducible at various dates between 30 and 120 days of continuous operation of the bioreactor and permit to know at which flux a membrane bioreactor must be operated. Comparison of constant pressure and constant flux tests under same conditions showed that the critical flux is almost identical to the limiting or pressure independent flux obtained in constant pressure. More generally, constant flux procedure below the critical flux avoids overfouling of the membrane in the initial stage and is more advantageous for membrane bioreactor operation.     

Density,speed of sound,heat capacity,and related properties of 1-hexanol and 2-ethyl-1-butanol as function of temperature and pressure

The speeds of sound in 1-hexanol and 2-ethyl-1-butanol have been measured over the temperature range from (293.15 to 318.15) K and at pressures up to 101 MPa. The densities have been measured within the temperature range from (283.15 to 343.15 or 353.15) K under atmospheric pressure. For the measurements, a pulse-echo-overlap method and a vibrating tube densimeter have been used. Additionally, in the case of 2-ethyl-1-butanol, the isobaric heat capacities from T = (293.15 to 323.15) K at atmospheric pressure have been measured by means of a DSC calorimeter. The experimental results are then used to calculate the densities and isobaric heat capacities as a function of temperature and pressure by means of a numerical integration technique. The effects of pressure and temperature on these and the related properties are discussed. Densities are correlated by means of the Tait equation.     

Application of thin film composite membranes to the membrane aromatic recovery system

The membrane aromatic recovery system (MARS) is a new membrane technology which recovers aromatic acids and bases. The first industrial installation has been operating at a Degussa site in the UK recovering cresols since 2002. The state of the art MARS technology employs a tubular silicone rubber membrane. However, this places some limitations on the process due to relatively low mass transfer rates and limited chemical resistance.In this paper, flat sheet composite membranes were investigated for application to the MARS process. In particular for recovery of compounds, such as 1,2-benzisothiazolin-3-one (BIT) which show low mass transfer rates through the current membrane. These composite membranes are comprised of a thin nonporous PDMS selective layer coated on a microporous support layer cast from polyacrylonitrile, polyvinylidene fluoride, polyetherimide or polyphenylenesulphone. The membranes have been characterised using SEM and gas permeation. The mass transfer of BIT through the composite membranes with no chemical reaction enhancement was an order of magnitude higher than through tubular silicone rubber membranes (10⁻⁷ m s⁻¹ versus 10⁻⁸ m s⁻¹). With chemical reaction enhancement, the mass transfer increased by another order of magnitude to 1.6 × 10⁻⁶ m s⁻¹ for BIT through a PVDF supported composite membrane. Mass transfer through the composite membrane was described well using analysis based on the resistance in series theory with chemical reaction. However, when a high osmotic pressure was applied across the membrane (molarity ∼ 3 M), significant water transport occurred across the membrane.     

Study of near infra red femtosecond laser induced particles using transmission electron microscopy and low pressure impaction: Implications for laser ablation–inductively coupled plasma-mass spectrometry analysis of natural monazite

The characteristics of infra red femtosecond laser-induced aerosols are studied for monazite (LREE, Th(PO₄)) ablation and correlations are established with inductively coupled plasma-mass spectrometry (ICP-MS) signals. Critical parameters are tested within wide ranges of values in order to cover the usual laser ablation -ICP-MS analysis conditions: pulse energy (0.15 < E₀ < 1 mJ/pulse), pulse width (60 < τ < 3000 fs), ablation time (t ≤ 10 min) and transport length (l ≤ 6.3 m). Transmission electron microscopy reveals that aerosols are made of agglomerates of ~ 10 nm particles and 20–300 nm phosphorus depleted condensed spherical particles. These structures are not affected by any laser ablation parameter. Particle counting is performed using electronic low pressure impaction. Small changes on particle size distribution are noticed. They may be induced either by a peak of ablation rate in the first 15 s at high fluence (larger particles) or the loss of small particles during transport. We found a positive correlation between I (ICP-MS mean signal intensity in cps) and N (particle density in cm^? 3) when varying E₀ and t, suggesting that N is controlled by the irradiance (P₀ in W·cm^? 2). Elemental ratio measurements show a steady state signal after the initial high ablation rate (mass load effect in the plasma torch) and before a late chemical fractionation, induced by poor extraction of bigger, early condensed spherical particles from the deepening crater. Such chemical fractionation effects remain within uncertainties, however. These effects can be limited by monitoring E₀ to shorten the initial transient state and delay the attainment of an unfavorable crater aspect ratio. Most adopted settings are for the first time deduced from aerosol characteristics, for infra red femtosecond laser ablation. A short transport (l < 4.0 m) limits the agglomeration of particles by collision process along the tube. Short τ is preferred because of higher P₀, yet no benefit is found on ICP-MS signal intensity under 200 fs. Under such pulse widths the increased particle production induces more agglomeration during transport, thereby resulting in higher mass load effects that reduce the ionization efficiency of the plasma torch. Thus, pulse energy must be set to get an optimal balance between the need for a high signal/background ratio and limitation of mass load effects in the plasma torch.     

Speed of sound,ideal-gas heat capacity at constant pressure,and second virial coefficients of HFC-227ea

The speed of sound of the gaseous 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea) was measured for temperatures from 273 to 333 K and pressures from 26 to 315 kPa with a cylindrical, variable-path acoustic interferometer operating at 156.252 kHz. The uncertainty of the speed of sound was less than ±0.05%. The ideal-gas heat capacity at constant pressure and the second acoustic virial coefficients were determined over the temperature range from the speed of sound measurements. The uncertainty of the ideal-gas heat capacity at constant pressure was estimated to be less than ±0.5%. The ideal-gas heat capacity at constant pressure results and second virial coefficients calculated from the present speed of sound measurements were compared with the available data.     

Calorimetric analysis of NaF and NaLaF4

Heat flux calorimetry was used to measure the heat capacity of NaF between 630 K and 1100 K. The results agreed well with previous measurements known from the literature. Similar experiments were performed on NaLaF₄. This compound was synthesized from NaF and LaF₃ and analyzed by X-ray diffraction. The heat capacity of NaLaF₄ was determined for two temperature ranges: from 4 K to 400 K, for which adiabatic calorimetry, and from 623 K to 1213 K for which differential scanning heat flux calorimetry was used. The two heat capacity series fit smoothly; the resulting C_p,m function was used in a reassessment of the binary system (NaF + LaF₃).     

Isopropanol dehydration via extractive distillation using low transition temperature mixtures as entrainers

Low transition temperature mixtures (LTTMs), also known as deep eutectic solvents, show properties that make them suitable as entrainers for extractive distillation. Two different low transition temperature mixtures were considered as potential entrainers for the extractive distillation of the azeotropic mixture (isopropanol + water). (Lactic acid + choline chloride) (2:1) and (glycolic acid + choline chloride) (3:1) were selected for this work. (Vapor + liquid) equilibrium measurements of the pseudo-binary systems (isopropanol + LTTM) and (water + LTTM) were measured at different concentrations of LTTM in a pressure range of 10 to 100 kPa. (Vapor + liquid) equilibrium data of the pseudo-ternary system (isopropanol + water + LTTM) were also measured at constant pressure (100 kPa) and constant LTTM molar fraction of 0.05 and 0.1. It was found that these LTTMs cannot break the azeotrope at those concentrations. However, the azeotrope was displaced to a much higher isopropanol concentration. The NRTL model was successfully applied to fit the experimental data.     

Volumetric properties of itaconic acid aqueous solutions

Densities of itaconic acid aqueous solutions were measured at 5 K intervals from T = (278.15 to 343.15) K. From the determined densities, the apparent molar volumes, the cubic expansion coefficients and the second derivatives of volume with respect to temperature which are interrelated with the derivatives of isobaric heat capacities with respect to pressure were evaluated. These derivatives were qualitatively correlated with the changes in the structure of water when itaconic acid is dissolved in it.     

Preparation of sulfonated poly(phthalazinone ether sulfone ketone) composite nanofiltration membrane

Thin film composite (TFC) membranes were prepared from sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) as a top layer coated onto poly(phthalazinone ether sulfone ketone) (PPESK) ultrafiltration (UF) support membranes. The effects of different preparation conditions such as the SPPESK concentration, organic additives, solvent, degree of substitution (DS) of SPPEK and curing treatment temperature and time on the membrane performance were studied. The SPPESK concentration in the coating solution was the dominant factor for the rejection and permeation flux. The TFC membranes prepared from glycerol as an organic additive show better performance then those prepared from other additives. The rejection increased and the flux decreased with increasing curing treatment temperatures. The salt rejections of the TFC nanofiltration (NF) membranes increased in the order MgCl₂ < MgSO₄ < NaCl < Na₂SO₄. TFC membranes showed high water flux at low pressure. SPPESK composite membranes rejections for a 1000 mg L⁻¹ Na₂SO₄ feed solution was 82%, and solution flux was 68 L m⁻² h⁻¹ at 0.25 MPa pressure.     

Vapour pressures,densities, and viscosities of the (water + lithium bromide + potassium acetate) system and (water + lithium bromide + sodium lactate) system

Measurements of thermophysical properties (vapour pressure, density, and viscosity) of the (water + lithium bromide + potassium acetate) system LiBr:CH₃COOK = 2:1 by mass ratio and the (water + lithium bromide + sodium lactate) system LiBr:CH₃CH(OH)COONa = 2:1 by mass ratio were measured. The system, a possible new working fluid for absorption heat pump, consists of absorbent (LiBr + CH₃COOK) or (LiBr + CH₃CH(OH)COONa) and refrigerant H₂O. The vapour pressures were measured in the ranges of temperature and absorbent concentration from T = (293.15 to 333.15) K and from mass fraction 0.20 to 0.50, densities and viscosities were measured from T = (293.15 to 323.15) K and from mass fraction 0.20 to 0.40. The experimental data were correlated with an Antoine-type equation. Densities and viscosities were measured in the same range of temperature and absorbent concentration as that of the vapour pressure. Regression equations for densities and viscosities were obtained with a minimum mean square error criterion.     

Solubility of proline–leucine dipeptide in water and in aqueous sodium chloride solutions from T = (288.15 to 313.15) K

Solubility of proline–leucine dipeptide, in water and in aqueous sodium chloride solutions, was measured at T = (288.15, 298.15, 308.15 and 313.15) K as a function of electrolyte concentration m = (0.1, 0.25, 0.5, 0.75 and 1) mol · kg⁻¹ of water. Solubility data has been evaluated from density measurements using a vibrating tube densimeter. It has been observed that sodium chloride renders the dipeptide proline–leucine more soluble in water. Salting-in coefficients and standard free energies of transfer of proline–leucine, from water to aqueous sodium chloride solutions, have been calculated from the solubility data. Standard enthalpies and entropies of transfer have also been estimated and interpreted in terms of electrostatic and hydrophobic perturbed domains in the hydration shells of the dipeptide and of the cation and anion of the salt, as a function of temperature and salt concentration.     

Volumes,heat capacities,and compressibilities of the mixtures of acetonitrile and 2-methoxyethanol

Heat capacities and speed of sound of (acetonitrile + 2-methoxyethanol) mixtures at 298.15 K and the densities of the same mixtures at T = (308.15 and 318.15) K were determined over the whole composition range. The excess of molar volume and isobaric heat capacity of the mixture, the partial molar volumes and heat capacities of both components of the mixture as well as the adiabatic and isothermal coefficients of compressibility and their excess were calculated from the obtained experimental data. The internal pressure of the examined system was also calculated. The results of investigations were analyzed and discussed. The behavior of the analyzed functions is similar to that observed in the case of the mixtures of acetonitrile with some aprotic solvents examined earlier.     

Cr cluster deposition by plasma—gas-condensation method

Transmission electron microscopy observation was carried out for nanometric Cr clusters deposited on microgrids at room temperature using plasma–gas-condensation (PGC) method. In order to obtain optimum conditions for monodisperse cluster formation we have studied effects of an Ar gas pressure, an Ar gas flow rate, and a mixing rate of He gas with Ar gas on the size distribution of formed clusters. It has been found that monodisperse clusters with the size rage of 9–13 nm in diameter are producible at a low Ar gas pressure (≤1.3 Torr) and a low Ar gas flow rate (≤600 sccm). The mean cluster size decreases with decreasing Ar gas pressure, while it is not sensitive to the Ar gas flow rate. When He gas is mixed with Ar gas, the mean cluster size further decreases to 6 nm and the cluster beam intensity becomes stronger probably because He gas with the high thermal conductivity enhances supersaturation for cluster nucleation.