Characterizing water sorption in 100% solids epoxy coatings

In the present work, water sorption kinetics and equilibrium in 100% solids epoxy coatings are investigated by immersion into distilled water baths from 20 to 85 °C (absorption tests) and drying in a furnace between 60 and 85 °C (desorption tests). The gravimetric liquid sorption measurements reveal a non-Fickian two-stage diffusion behaviour during both absorption and desorption. The effect of hydrothermal history was also investigated. Cycling the immersion bath temperature increases the saturation values. Alternating sorption–desorption cycles increases the speed of water movement. The hydrothermal-induced coating degradation and the sorption modes are discussed.     

Standard pH values for potassium hydrogenphthalate reference buffer solutions in acetonitrile—water mixtures up to 70 wt% at various temperatures

Reference value standards, pHs, for 0.05 mol kg⁻¹ potassium hydrogenphthalate (KHPh) reference buffer solutions in 30, 50 and 70 wt% acetonitrile—water mixed solvents at temperatures from 288.15 to 308.15 K have been determined from emf measurements of the reversible cell Pt|Ag|AgCl|KHPh + KCl|Quinhydrone|Pt, in which the H⁺-reversible quinhydrone electrode replaces the ill-behaving hydrogen electrode. Values of the first ionization constant of the o-phthalic acid (H₂Ph; benzene-1,2 dicarboxylic acid) in these mixed solvents have also been determined from analogous measurements. The consistency of the present results with the previously determined pHs values in 5, 15 and 30 wt% acetonitrile—water mixtures is analysed by multilinear regression of pHs as a function of both solution composition and temperature. These smoothed standard pHs values are used to optimize the parameters of an equation predicting pHs values in different aqueous organic solvents.     

Applications of hydrothermal electrolysis for conversion of 1-butanol in wastewater treatment

Hydrothermal electrolysis of organic compound in the presence of electrolyte was conducted for a woody biomass model compound. The reaction behavior of 1-butanol as a woody biomass model compound was studied in subcritical conditions at 200-250 °C and 8-12 MPa with a batch autoclave. The autoclave volume was 500 mL and equipped system with agitation stirrer, electric current control, electric heating and temperature control and a pressure gauge. The chemical species in aqueous products were identified by gas chromatography mass spectrometry (GC-MS) and quantified using gas chromatography flame ionization detector (GC-FID). The gaseous products were analyzed by gas chromatography with a thermal conductivity detector (GC-TCD). The effects of reaction temperature, pressure and applied constant current on the conversion process of 1-butanol were presented. The main products from the conversion of 1-butanol were butanal, butyric acid, hydrogen and carbon dioxide. Additionally, the values of reaction rate constant for butanal and butyric acid formation were calculated at 200 and 250 °C by kinetic study.     

The effects of fuel washing techniques on alkali release from biomass

The influence of different washing techniques on the alkali release during pyrolysis of biomass is studied. After washing and drying, samples of wheat straw, wood waste and cellulose are subjected to a constant heating rate in a N₂ atmosphere, and the release rate of alkali compounds from the sample is measured continuously by a surface ionization technique. Alkali is released from the untreated biomass in two temperature intervals: (1) in connection with the pyrolysis process taking place at 200-500°C, and (2) from the material remaining after pyrolysis at temperatures above 600°C. Separate vacuum pyrolysis experiments show that the alkali release is dominated by potassium-containing compounds, with minor contributions from sodium-containing compounds. The effect of water washing of the biomass is compared with a more thorough acid leaching technique. In the temperature range 200-500°C, washing with water reduces the alkali emission from wood waste and wheat straw by 5-30%, while acid leaching is more effective and reduces the emission by around 70%. Above 600°C where the vaporization of alkali compounds from untreated wheat straws increases sharply, the washing procedures are sufficient for a reduction in the measured alkali release by more than 90%. Experiments with pure cellulose (ash content 0.07%) indicate that the washing methods are ineffective in removing alkali bound to the organic structure of the biomass. The results support the conclusion from earlier studies that relatively simple washing techniques can improve the combustion properties of biomass fuels with a high ash content. For fuels with a lower ash content like woody biomass, the concentration of alkali bound to the organic structure limits the effect of the washing techniques.     

Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (< 200 °C) and constant oil shale grade, both the relative dielectric constant (ε′) and imaginary permittivity (ε″) decrease with increased frequency and remain constant at higher frequencies. At low temperature and constant frequency, ε′ decreases or remains constant with oil shale grade, while ε″ increases or shows no trend with oil shale grade. At higher temperatures (> 200 °C) and constant frequency, ε′ generally increases with temperature regardless of grade while ε″ fluctuates. At these temperatures, maximum values for both ε′ and ε″ differ based upon oil shale grade. Formation fluids, mineral-bound water, and oil shale varve geometry also affect measured dielectric properties. This review presents and synthesizes prior work on the influence of applied frequency, oil shale grade, water, and temperature on the dielectric properties of oil shales that can aid in the future development of frequency- and temperature-specific in situ retorting technologies and oil shale grade assay tools.     

Effect of heat treating gel films on the formation of superhydrophobic boehmite flaky structures on austenitic stainless steel

The effect of heat treating gel films at different temperatures on the formation of the boehmite flaky structures on AISI 316 type austenitic stainless steel is investigated. After heating at different temperatures, the reactivity of the gel films with boiling water to form boehmite flakes was different, which resulted in different morphologies and different contact angle values after coating with hydrolyzed (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trimethoxysilane (FAS). When the gel film was heat treated from 200 to 600 °C, the resulting contact angle was above 150°, indicating superhydrophobic behavior. However, when the gel film was heat treated below 200 °C as well as at 700 and 800 °C, only some boehmite flakes were formed; when the gel film was heat treated at 900 °C, no boehmite flakes were observed. In these cases the surface roughness is insufficient for the superhydrophobicity. The formation condition of the boehmite flakes by reaction of the gel film with boiling water is also tentatively discussed.     

Influence of π-complexing agents on the anionic polymerization of styrene with lithium as counterion in cyclohexane. 3. Effect of tetraphenylethylene

The propagation reaction in anionic polymerization of styrene with lithium as counterion in cyclohexane has been investigated for four different concentrations of tetraphenylethylene (TPhE) in the range of living end concentrations between 10⁻⁵ and 10⁻³ M at 20 °C. The values of the apparent dissociation constant of PStLi dimer and the weighted rate constants of all unassociated species were obtained for all four investigated concentrations of TPhE. The mechanism, already used in the case of durene, was also applied in this system and the values of the relevant absolute propagation rate constants of the two reactive monomeric species have been derived from the kinetic results. The absolute propagation rate constant of PStLi·TPhE is much lower than that of PStLi. The complexation constant of PStLi with one molecule of TPhE is more than 100 times larger than that of PStLi with one molecule of durene.     

The lubricity of graphite flake inclusions in sintered polyimides affected by chemical reactions at high temperatures

The internal lubrication of 15 vol% graphite flakes added to polyimide was investigated during sliding at 50-200 N normal loads, 0.3 m/s and 23-260 °C, showing that chemical reactions in the polyimide bulk have an important effect on the sliding efficiency of the graphite. The latter are illustrated by Raman spectroscopy, thermo-analytical measurements and mass spectroscopy. At low temperatures (23-100 °C), transfer consists of pure graphite and mechanical shear prevails. At intermediate temperatures (120-180 °C), transfer consists of coexistent polyimide and graphite. A regime with decreasing friction is related to hydrolysis reactions in the bulk polyimide, lowering the effective water content in the sliding interface. At higher temperatures (180-260 °C), transfer consists of mixed polyimide-graphite. A low friction regime is related to imidisation of the bulk polymer and interfacial water supply, favouring the graphite lubricating properties. The graphite debris morphology occurs as flakes (low temperature) or powders (intermediate temperatures), likely resulting from cleavage between the basal planes or embrittlement across the basal planes.     

Effect of regime and construction parameters on the drying kinetics of polyamide yarn

Conclusions For more thorough mechanical dewatering, before squeeze-out it is necessary to heat the yarn preliminarily to 80°C.The drying time for continuous yarn does not change at various spinning speeds and a constant drying temperature.To intensify the yarn drying process at low temperatures (100–120°C), it is necessary also to heat the directing cylinder; on increasing the temperature to 200–220°C, heating of the second cylinder is ineffective.Translated from Khimicheskie Volokna, No. 1, pp. 26–27, January–February, 1990.     

The oxygen production step of a copper-chlorine thermochemical water decomposition cycle for hydrogen production: Energy and exergy analyses

In the copper-chlorine (Cu-Cl) thermochemical cycle water is decomposed into its constituents (oxygen and hydrogen) by a series of chemical reactions. The cycle involves five steps in which three thermally driven chemical reactions and one electrochemical reaction take place. Oxygen is produced during one of the main chemical reactions. In the present study, the O₂ production step is described with its operational and environmental conditions, and energy and exergy analyses are performed. The cycle is assumed driven using nuclear energy. Various parametric studies are carried out on energetic and exergetic aspects of the step, considering variable reaction and reference-environment temperatures. At a constant reference-environment temperature of 25 °C, the exergy destruction of the O₂ production step varies between 4500 and 23,000 kJ/kmol H₂ when the reaction temperature increases from 450 to 1000 °C. At a 500 °C reaction temperature and a 25 °C reference-environment temperature, the exergy destruction for this step is found to be 5300 kJ/kmol H₂. At a reaction temperature of 500 °C and a reference-environment temperature of 25 °C, the exergy efficiency of the step is determined to be 96% and to decrease with increasing reaction temperature and/or reference-environment temperature.     

Influence of composition on the linear viscoelastic behavior and morphology of PP/HDPE blends

In this paper the influence of temperature and composition on the dynamic behavior and morphology of polypropylene (PP)/high-density polyethylene (HDPE) blends were studied. The blend composition ranged from 5 to 30 wt% of dispersed phase (HDPE) and the temperatures ranged from 180 to 220 °C. The interfacial tension between PP and HDPE at temperatures of 180, 200 and 220 °C was obtained from fitting Palierne's emulsion model [1] to the experimental data of PP/HDPE blends with different compositions and from the weighted relaxation spectra of PP/HDPE blends with different compositions, following Gramespacher and Meissner [2] analysis. The interfacial tension between PP and HDPE as inferred from the rheological measurements was shown to depend on PP/HDPE blend composition. However, the results indicated that there is a range of PP/HDPE blend composition for which interfacial tension between PP and HDPE is constant. Considering these values, it was shown that interfacial tension between PP and HDPE decreases linearly with increasing temperature.     

Experiments and modeling on the deacidification of agglomerates of nanoparticles in a fluidized bed

The deacidification of the fumed silica AEROSIL® 200 was studied experimentally in a batch fluidized bed in the temperature range from 250 °C to 400 °C. For a well fluidized bed, the temperature and the steam concentration in the fluidizing gas are the determining parameters for the overall rate of deacidification. If the bed is not well fluidized, e.g. because it is too shallow, or it is fluidized near the point of minimum fluidization velocity, the rate of deacidification drops because channeling and bypassing occur. The adsorption equilibrium of steam and HCl on AEROSIL® 200 was measured for a wide temperature range and the temperature dependency of the Henry coefficient for steam is given. A mathematical reactor model was developed for the adsorption and for the surface reaction on highly agglomerated nanoparticles in a fluidized bed. In applying this model to the experimental data for the deacidification, a simple kinetic rate expression could be derived for the deacidification reaction, which is otherwise not obtainable. The temperature dependency of the rate constant was also determined. All other parameters for the model can either be found through independent measurements (e.g. adsorption equilibrium or fluidizing characteristics) or in literature. The model can be used for sizing and optimizing of fluidized bed reactors in the production of fumed oxides.     

Thermal conductivity of insulating refractories measured by the standard method and by the cylinder method

Conclusions The coefficients of thermal conductivity of insulating refractories measured by the method prescribed in GOST 12170-66, using the recommended thermometers with a scale division of 0.1°C and thermal insulation made from firebrick with an apparent density of 1.0 g/cm³, are appreciably higher than data obtained by the cylinder method. At average temperatures of 200–500°C (400–1000°C on the hot face) the discrepancy comes within the range 50–200%; when T_mean=600–700°C (1200–1300°C on the hot face) the discrepancies diminish to 0–30%.The maximum apparatus error in determining the thermal conductivity according to GOST 12170-66 with the use of Beckmann thermometers and low thermal-conducting linings is 10–30% for – 0.2–1.0 kcal/(m·h·deg), which greatly exceeds that indicated in the standard, ±10%. The maximum proportion in the error comes from the measurement of the drop in water temperature as it passes through the calorimeter. Consequently, the use of the standard recommended thermometers with scale divisions of 0.1°C is unacceptable for measurements on materials with a low thermal conductivity, since it may lead to errors of about 100%.Detailed comparison of the results of measuring this factor on standard equipment using the Beckmann thermometers, and on the improved instrument designed by the Ukrainian Institute (the cylinder method), showed that the mean square deviation of the experimental values for thermal conductivity for identical specimens with respect to the interpolation curves in the case of standard determinations is 2–3 times greater than the corresponding deviation for the cylinder method.In most experiments the interpolation curves =f(T) for the standard method is different by ±15–25% from the curves obtained with the cylinder method. This displacement apparently is due to certain constant errors connected with the unaccounted-for sources of error in the standard methods.The proposed method of determining the coefficient of thermal conductivity is of interest for scientific-research work. The use of the cylinder method is industry is associated with difficulties in preparing the specimens — Editors.Translated from Ogneupory, No. 8, pp. 45–52, August, 1971.     

The solubility and solubility modelling of budesonide in pure and modified subcritical water solutions

In this article, the solubility behaviour of budesonide in pure and alcohol-modified subcritical water (SBCW) solutions between 25 °C and 200 °C is reported. Methanol and ethanol were selected as modifiers. In the presence of ethanol, the solubility of budesonide in SBCW increased up to 10 times. In all reported cases, the solubility of budesonide was directly dependant on the dielectric constant of the solvent mixture. A correlation between the budesonide solubility data and the dielectric constant of SBCW was developed. The correlation parameters were altered to improve the accuracy of the outputs of the solubility model for 9-anthracenemethanol in SBCW. The model was able to predict budesonide solubility in SBCW and SBCW-alcohol solutions with an average error of 3%. The model is applicable to all the budesonide-SBCW-alcohol systems investigated in this work and is valid for a broad range of SBCW ternary systems.The solubility of budesonide was also modelled using the Modified Universal Functional Activity Coefficient (M-UNIFAC) model. Corrections were made to the interaction parameters so that the M-UNIFAC model was able to reproduce the solubility of budesonide in SBCW within 5% of experimental values. In order to check the validity of the parameter correction, the solubility of 9-anthracenemethanol in SBCW was established and modelled.     

High-temperature electrical properties of lanthanum beta-alumina solid electrolytes

Impedance spectroscopy measurements were carried out in the 10 Hz to 10 MHz frequency range from 500 to 1200 °C in LaAl₁₁O₁₈ pellets sintered at 1600 °C. The powders were obtained by the polymeric precursor technique. The sintered pellets were nearly single phase LaAl₁₁O₁₈. The bulk electrical resistivity was evaluated from the [−Z″(ω) × Z′(ω)] impedance diagrams. The value of the activation energy for the ionic conduction, 0.89 eV, was determined from the Arrhenius plot of the bulk conductivity. An yttria-stabilized zirconia (YSZ) oxygen pump and an YSZ oxygen sensor were used for providing 10–1500 ppm of partial pressure of oxygen (pO₂) at 1000 °C for determining the electromotive force (emf) in a Pt/LaAl₁₁O₁₈/Cr₂O₃ + Cr electrochemical cell. The results follow the Nernst law. The high signal-to-noise ratio of the emf at low pO₂ values shows that the LaAl₁₁O₁₈ specimens may be used in sensors for detection of oxygen at high temperatures.     

Electrophoretic mobility of magnetite particles in high temperature water

Magnetite (Fe₃O₄) is one of the most common oxides forming deposits and particulate phases in industrial high temperature water circuits. Its colloidal characteristics play a principal role in the mechanism of deposit formation and can be used as controlling factors to prevent or minimize deposit formation and damage of industrial pipelines due to under-deposit corrosion. In this study, a high temperature particle electrophoresis technique was employed to measure the zeta potential at the magnetite/water interface—the parameter that controls colloidal stability of particles, their aggregation, and deposition. The measurements were made at temperatures up to 200 °C over a wide range of pH. The isoelectric points of magnetite, at which the deposition of particles is increased, were determined at pH 6.35, 6.00, 5.25, and 5.05 for temperatures 25, 100, 150, and 200 °C, respectively. The observed temperature dependence of zeta potential and the isoelectric pH point of magnetite can help to explain the extent of interactions between the colloidal particles and the steel wall surfaces under hydrothermal conditions, and indicate methods for controlling and mitigating oxide deposition in high temperature water cycles.     

Experimental study on a mortar. Temperature effects on porosity and permeability. Residual properties or direct measurements under temperature

This study is a part of a large experimental program intended to characterize the effects of increasing temperature upon the hydraulic properties of cement based materials. Initial gas permeability and porosity values of the used material, a normalized mortar with a water / cement ratio of 0.5, clearly show the material homogeneity after a drying phase at 60 °C. The initial permeability is moreover insensitive to confining pressure variation which is evidence of the absence of significant initial micro-cracking in which the flow could occur. Residual properties (at room temperature) were measured after thermal treatments at 150 or 250 °C. These heating phases lead to a clear increase in porosity and permeability being sevenfold its initial value after a 250 °C treatment. This increase in permeability comes from two distinct effects that can be experimentally highlighted: a pore widening observed with the Klinkenberg effect being lower and a micro-crack closure occurring with the increase in confining pressure. Permeability was also measured with gas injection in samples submitted to thermal loading and slightly confined (at 4 MPa). Three levels of temperatures were used: 25, 105 and 200 °C; in a first stage the permeability remained almost constant to finally significantly increased at 200 °C. At 105 °C there is a widening of pores observed with the Klinkenberg effect but not sufficient to vary the permeability. At 200 °C micro-cracks have occurred but their influence upon permeability is lower than for treated material. This is an effect of the confining pressure applied on the material during heating.     

Flow adsorption calorimetry of coals before and after heat and oxidation treatment

Flow microcalorimetry has been used to determine the heats of preferential adsorption of n-butanol and ammonium hydroxide on a number of coals immersed in n-heptane and water respectively. The determinations have also been carried out on the coals subjected to heating in air to temperatures ranging from 100 °C to 200 °C, to illustrate how the calorimetric technique can detect changes in the surface properties of the coals subjected to various treatments. The heats of adsorption have provided information on the relative surface acidities and hydrophobicities of the coals.     

Thermal treatment of C-S-H gel at 1 bar H2O pressure up to 200 °C

Homogeneous CaO-SiO₂-H₂O gels were prepared at Ca/Si molar ratios 0.83, 1.01, 1.21, 1.50, 1.83 and 2.02. These were aged for 12-24 months at 25 °C and subsequently treated in steam, 1 bar total pressure, at 130 or 200 °C; also in water at 55 and 85 °C. Gels with low Ca/Si ratios partially crystallised at 85 °C. At 130 °C in steam, crystalline products included 11 and 14 Å tobermorite, xonotlite, afwillite, portlandite and another incompletely characterised phase. At 200 °C, the gels retained much water but remained amorphous to X-ray powder diffraction (XRD). However, electron microscopy, coupled with diffraction and analysis, disclosed that the “amorphous” product obtained at 85-200 °C had undergone crystallisation with domains typically 10-1000 nm. At higher bulk Ca/Si ratios, 1.83 and 2.02, much nanoscale precipitation of Ca(OH)₂ occurs, probably by exsolution, such that the residual C-S-H product has a Ca/Si ratio in the range 1.4-1.5. The complex thermal history of the products is reflected in their pH conditioning ability, measured at 25 °C. The results are applied to predict the evolution of pH in a cement-conditioned nuclear waste repository which experiences a prolonged thermal excursion.     

Reaction kinetics of d-xylose in sub- and supercritical water

Reactions of d-xylose were investigated with a flow apparatus in water at high temperatures (350 and 400 °C) and high pressures (40-100 MPa) to elucidate the reaction pathway and reaction kinetics. The products obtained from the reaction of d-xylose were furfural, d-xylulose, glyceraldehyde, glycolaldehyde, dihydroxyacetone, pyruvaldehyde, lactic acid and formaldehyde. Experimental results showed evidence of a dehydration reaction pathway, a retro-aldol reaction pathway and a Lobry de Bruyn-Alberta van Ekenstein (LBET) pathway from d-xylulose. The proposed reaction pathway and kinetic model were in accord with the experimental results. The kinetic constants showed dependence with water density (pressure). At 400 °C and water density of 0.52 g/cm³ at 40 MPa, the reaction from d-xylose to d-xylulose occurred by the LBET pathway with the reverse reaction being negligible. At 400 °C, increasing the water density from 0.52 to 0.69 g/cm³ decreased the kinetic rate constant of the forward LBET pathway and increased that of the reverse LBET pathway. The kinetic rate constant of the dehydration of d-xylulose to furfural increased with increasing water density at constant temperature. The kinetic rate constant of the retro-aldol reaction of d-xylose increased, and the retro-aldol reaction of d-xylulose decreased with increasing water density at 400 °C.