Synthesis,characterization and evaluation of resin-based carbon spheres modified by oxygen functional groups for gaseous elemental mercury capture

A novel resin-based spherical carbon material was successfully prepared by suspension polymerization of alkyl phenol and formaldehyde and steam activation in combination with surface modification by heat treatment with dry air for enhancing Hg⁰ adsorption. The analysis results demonstrate that the oxidation-modified activated carbon spheres possess better mercury removal performance than untreated sorbents, and the ACS-O300 obtained by oxidation modified at 300 °C is the optimal sorbent at the adsorption temperature range from 25 to 150 °C. The main reason is assigned to the increase of the oxygen functional groups of C=O and C(O)–O–C that play an important role as effective active sites for binding the Hg⁰, even though the C(O)–O–C predominates in mercury removal performance under higher adsorption temperature. The optimum O₂ concentration is 4 vol% at the O₂ concentration range from 0 to 8 vol%. SO₂ and NO are favorable to the mercury adsorption under 4 vol% O₂, while H₂O leads to the inhibition of the mercury adsorption. The TPD results suggest that a strong desorption peak at temperature around 235 °C and a weak peak at 324 °C should generate from mercury desorption of C?=?O and C(O)–O–C, correspondingly. Moreover, the XPS analysis results of the fresh and used sorbent indicates that the C=O and C(O)–O–C serve as strong oxidizer and facilitate electron transfer for converting Hg⁰ to Hg²⁺ in the chemisorption process. These results suggest that the obtained resin-based spherical porous carbon (ACS-O300) is promising for Hg⁰ capture.     

Distillation recovery of AsCl<Subscript>3</Subscript> from AsCl<Subscript>3</Subscript>-HCl-H<Subscript>2</Subscript>O solutions

The distillation recovery of arsenic trichloride from saturated solutions in concentrated hydrochloric acid has been studied experimentally at a pressure of 1.013 × 10⁵ Pa and temperatures from 60 to 75°C, and the optimal process temperature has been determined.     

Estimation of the Enhancement Factor for Mercury in Air

A combination of classical thermodynamics and molecular theory was used to calculate the enhancement factor (ratio of vapor-phase partial pressure to saturated vapor pressure) for liquid mercury in equilibrium with air at standard atmospheric pressure at temperatures from 0 °C to 40 °C. The enhancement factors range from 1.0025 at 0 °C to 1.0016 at 40 °C. This enhancement is too small in magnitude, and in the wrong direction, to explain a difference that has been noted between equilibrium vapor concentrations implied by the vapor pressure of pure mercury and those assumed in some calibration procedures.     

Mechanical properties of photocatalytic white concrete subjected to high temperatures

The paper describes the consequences of progressive damage in architectural high performance concrete when exposed to different heating treatments. Specimens were tested for uniaxial compressive, direct, and indirect tensile strengths at ambient conditions approximately one day after the exposure to the high temperature. Modifications in the microstructure, porosity, and pore size distribution of the fire deteriorated specimens were identified using scanning electron microscopy and mercury intrusion porosimetry techniques. Test results revealed no significant variations in the mechanical strengths for specimens exposed to temperatures up to 250 °C. Per contra, significant damage was observed for higher temperature, 500 °C and 750 °C, treatments, similar to that of ordinary concrete made with similar aggregates. Based on X-ray diffraction analysis, photocatalytic properties of the concrete were lost at 750 °C.     

Surface changes during pyrolytic conversion of hybrid materials to oxycarbide glasses

Hybrid materials from TEOS–TBOT–PDMS have been prepared and pyrolyzed between 400 and 1,000 °C. The surface characteristics of this type of materials have been studied by nitrogen adsorption, mercury intrusion porosimetry, and inverse gas chromatography at infinite dilution (IGC). IGC has been used for obtaining the dispersive and acid–base surface energies of the different materials. The specific surface areas and pore volumes of the studied samples have resulted to increase the pyrolysis temperatures ranging between 400 and 600 °C and decrease for higher temperatures. On the other hand, surface energies increase when the materials are pyrolyzed between 400 and 800 °C and then decrease after pyrolysis at 1,000 °C. When the material is pyrolyzed at the highest temperature, the surface energies are close to that of typical glasses. It has been observed that pyrolyzing at 800 °C the material has the highest values of both components of the surface free energy (dispersive and specific). The surface energy–pyrolysis temperature variation does not correspond to the formation of micropores in the material during the pyrolysis process. Therefore, it has been assumed that high energy active sites must be formed on the surface when the materials are pyrolyzed at 800 °C.     

PVDF hollow fiber and nanofiber membranes for fresh water reclamation using membrane distillation

Polyvinylidene fluoride hollow fiber and nanofibrous membranes are engineered and successfully fabricated using dry-jet wet spinning and electrospinning techniques, respectively. Fabricated membranes are characterized for their morphology, average pore size, pore size distribution, nanofiber diameter distribution, thickness, and water contact angle. Direct contact membrane distillation (DCMD) performances of the fabricated membranes have been investigated using a locally designed and fabricated, fully automated MD bench scale unit and DCMD module. Electrospun nanofibrous membranes showed a water flux as high as 36 L m^?2 h^?1 whereas hollow fiber membranes showed a water flux of 31.6 L m^?2 h^?1, at a feed inlet temperature of 80 °C and at a permeate inlet temperature of 20 °C.     

Influence of substrate temperature and film thickness on the structure of reactively evaporated In2O3 films

Indium oxide films 25–550 Å thick were reactively evaporated at an oxygen pressure of about 0.27 Pa and at a substrate temperature between room temperature and 400°C. The dependence of the structure of the films on the substrate temperature and on the film thickness was studied using transmission electron microscopy and electron diffraction. It was found that thick films (about 550 Å) were amorphous at room temperature, partially crystallized at 50–125°C and crystalline at 150–400°C. The crystallinity of the films deposited at 150–250°C also depended markedly on the film thickness. Very thin films about 25 Å thick were quasi-amorphous, but with increasing film thickness the amorphous phase transformed into a crystalline phase.The thermal transformation of the amorphous films after deposition was also studied. Amorphous films about 550 Å thick deposited at room temperature and 100°C crystallized at 230°C and 210°C respectively.     

Assembly and Study of Different Mercury Cells with Known Impurity Content and Isotopic Composition

The “Centro Español de Metrología” is carrying out a project to improve the knowledge of the influence of impurities and isotopic composition on the temperature of the mercury triple point. High-purity mercury from the Almaden mine (stated purity of 99.9998%) was further purified by vacuum distillation. Three mercury fractions, the original mercury from Almaden and two distilled fractions, were characterized in terms of both impurities and isotopic composition and used to measure the mercury triple point. The original mercury sample contained silver at 560 ng · g^?1 as the main impurity while the impurity levels were much lower (silver < 1 ng · g^?1) in the two distilled fractions. The isotopic composition of the distilled fractions showed delta values, expressed as $1,000\times(^{198/202}{\rm Hg}_{\rm sample}-^{198/202}\,{\rm Hg}_{\rm reference})/^{198/202}{\rm Hg}_{\rm reference}The “Centro Espa?ol de Metrología” is carrying out a project to improve the knowledge of the influence of impurities and isotopic composition on the temperature of the mercury triple point. High-purity mercury from the Almaden mine (stated purity of 99.9998%) was further purified by vacuum distillation. Three mercury fractions, the original mercury from Almaden and two distilled fractions, were characterized in terms of both impurities and isotopic composition and used to measure the mercury triple point. The original mercury sample contained silver at 560 ng · g⁻¹ as the main impurity while the impurity levels were much lower (silver < 1 ng · g⁻¹) in the two distilled fractions. The isotopic composition of the distilled fractions showed delta values, expressed as , of 1.37±0.07 (1σ) for the first distilled sample and −1.55±0.03 (1σ) for the second distilled sample with reference to the original Almaden mercury. For the measurement of the mercury triple point, an alcohol stirred bath was used that allowed two cells to be compared nearly simultaneously. It was observed that the presence of the silver impurities in the high-purity mercury modified slightly the mercury triple point while the effect of variations in the isotopic composition can be considered negligible.     

Lag in the temperature measurement system in performing fractional distillation of petroleum products

We carried out mathematical simulation of the temperature measurement system in performing fractional distillation of petroleum products (FDPP). To evaluate the actual lag in measuring the temperature in the process of FDPP, a special experiment was run on the basis of the mathematical model developed. It is shown that under unsteady-state conditions the error of a glass thermometer due to the phenomenon of thermal response may attain 15–25°C or more.     

Adsorption of oxygen in an activated europium ion-exchanged mordenite

The adsorption of oxygen in an activated europium ion-exchanged mordenite(Eu-M) was studied over the temperature range 25–600°C by the measurement of fluorescence of Eu₂₊ ion and a temperature programmed desorption (TPD) spectra of oxygen. When oxygen was exposed to a activated Eu-M, the intensity of emission band for Eu²⁺ ion extremely decreased. After the adsorption of oxygen at room temperature, the emission intensity was increased with a rise of degassing temperature and restored to the original emission intensity above 300°C. While, in Eu-M, at least four different states of adsorbed oxygen were indicated by the appearance of four TPD peaks with peak maxima located at about 70°C(α), 220°C(β), 300°C(γ) and >500°C(δ). The intensity of TPD peaks was dependent on the adsorption temperature. In the case of adsorption at 300°C or 600°C, the total amount of desorbed oxygen corresponded to one oxygen molecule adsorbing per Eu²⁺ ion.     

Dependence on temperature of tensile properties of the single-crystal superalloy DD11

Tensile tests within a temperature range from room temperature (RT) to 1100°C were performed on a novel second-generation single-crystal superalloy DD11. The experimental results indicated that the yield strength (YS) remained constant up to 760°C, while a maximum was reached at 850°C. The elongation and area reduction decreased gradually from RT to 760°C and then they increased rapidly at temperatures above 760°C. As for the deformation mechanism, when the temperature was below 850°C, the γ′ precipitates were sheared by isolated faults, faulted loops and dislocation pairs. The formation of dislocation networks and dislocation climb mechanism were confirmed at temperatures above 980°C. Finally, the relationship between the YS of the DD11 alloy and the operative deformation mechanism was discussed.     

HRTEM and Raman characterisation of the onion-like carbon synthesised by annealing detonation nanodiamond at lower temperature and vacuum

Onion-like carbon (OLC) was synthesised by annealing detonation nanodiamond for 1.5?h at temperatures from 500 to 1400°C and at a vacuum of 1?Pa. The results showed that the nanodiamond was transformed into the amorphous carbon (a-C) at first and then the a-C was transformed into the OLC gradually with the increase in annealing temperature. Moreover, at the annealing temperature of 600°C, the nanodiamond started transforming into a-C from the edge of the nanodiamond particle (1?1?1) crystal plane. At the annealing temperature of 750°C, the nanodiamond was transformed into the a-C completely. At the annealing temperature of 850°C, the a-C began transforming into the OLC at the edge area. At the annealing temperature of 1000°C, the OLC particle with a size smaller than 5?nm was synthesised. However, in the centre of the OLC particle, untransformed a-C coexisted. At the annealing temperature of 1100°C, the microstructure of the OLC particle with a size smaller than 5?nm became optimised. At the annealing temperature of 1200°C, the OLC particle with a size larger than 5?nm was fabricated. There was also untransformed a-C coexisting in the centre of the OLC particle. At the annealing temperature of 1350°C, all the a-C was transformed into the OLC. The average size of the OLC was approximately 5?nm, which was the same as that of the nanodiamond. The layers of the OLC were varied from several to 12.     

Temperature dependence of the effective permeability of heat treated Sendust alloys

The temperature dependence (-10°C-70°C) of the effective permeability (μeff) of Sendust alloys (Fe-9-10 wt% Si-5-7 wt% Al) quenched at a room temperature from the various temperatures (400°C-700°C) was investigated at every 2°C in the temperature range of -10°C to 70°C. Most of the studied alloys gave a peak of μeffin the studied temperature range. The peak temperature (Tp) giving the peak μeffvaried with different alloy composition. The alloys of Tp = 20°C are supposed to correspond to the alloys of the zero magnetocrystalline anisotropy constant (K1= 0) at 20°C. The deduced K1= 0 lines at various temperatures (-10°C-50°C) were obtained for an Fe-Si-Al ternary system. The values of peak μeffat the same Tp were different, depending on alloy composition, This difference is due to the difference in the polycrystalline magnetostriction constant (λ s) of the alloys. The peak temperatures of the studied alloys vary with the different heat treatments. This variation is due to the variation of K1, induced by the change in microstructures of the alloys. The variation of the values of peak μeffwith heat treatments was small compared to the difference of those in the alloys of different composition. It seems that the variation of the λ s with heat treatments would be small. Both the compositional dependence of μeffat 20°C and the temperature sensitivity (Δμeff/ΔT) were obtained for both the alloys cooled continuously to room temperature and those quenched at room temperature from 400°C.     

High-temperature mechanical behavior of cordierite-based porous ceramics prepared by modified cassava starch thermogelation

In this study, the high-temperature mechanical response of a cordierite-based porous material prepared by direct starch consolidation was evaluated. Disks were prepared by the thermogelation (85 °C, 4 h) of an aqueous suspension (29.6 vol. %) of a cordierite precursor mixture (talc, kaolin, and alumina) with the addition of a commercial modified cassava starch (11.7 vol.%), drying (50 °C, 24 h), firing (650 °C, 2 h), and reaction sintering (1330 °C, 4 h). The porous microstructures were characterized by Archimedes method (bulk density and apparent porosity measurements), SEM with image analysis (pore cavity sizes), and mercury porosimetry (pore throat sizes). Mechanical behavior was evaluated in diametral compression using a servohydraulic testing machine at room temperature, 800, 1000, and 1100 °C. Apparent stress–strain relationships were obtained from load–displacement curves, and mechanical parameters, such as fracture strength (σ_F), fracture strain (ε_F), and apparent Young modulus (E _a) were determined. Moreover, crack patterns and fracture surface were also evaluated. The obtained results were analyzed as a function of the developed microstructures, considering the presence of a silicate glassy phase and a complex porosity, and the testing temperature. From these results, the operative fracture mechanism was proposed. Finally, the obtained results were compared with those reported by the authors for cordierite porous materials prepared using other types of native starches, determining that the best mechanical response, in particular at high temperature, was obtained using modified cassava starch.     

Durability of cementitious binder derived from industrial wastes

The durability of cementitious binder hydrated at 27°C and 50°C under high humidity was examined by alternate wetting and drying, as well as heating and cooling, cycles at temperatures ranging from 27°C to 60°C and by performance in water. The results show that cementitious binder hardened at 50°C possesses higher water resistance and lower porosity than the binder hardened at 27°C. A decrease in the strength of the cementitious binder was observed with an increase in temperature and in the wetting and drying and heating and cooling cycles. The maximum decrease in strength occurred at 60°C. The cementitious binder cured at 27°C showed a much smaller decrease in strength with a rise in temperature and in weathering cycles. The changes in strength of the cementitious binder were monitored by differential thermal analysis and microscopy.     

High-Speed Infrared Radiation Thermometry for Microscale Thermophysical Property Measurements

A new infrared radiation thermometer having a high temporal response and a high spatial resolution is being developed at NMIJ to meet the existing demand for measurements of thermophysical properties of thin films, coatings, and solids in microscale. The thermometer consists of a photovoltaic (pv)-type of mercury cadmium telluride (MCT) detector and a compact Cassegrain type of mirror optics without a mechanical chopper. The performance of the thermometer has been well characterized experimentally. Sensing infrared radiation around 10 μm of wavelength, the thermometer covers the temperature range from −50 to 150°C and has a temperature resolution better than 0.3°C at −50°C for blackbody radiators. The spatial resolution has also been checked by using a test pattern (USAF 1951) for rating the resolution of optical systems. Temperature changes of specimen surfaces in periodic heating with a laser beam modulated above 100 kHz have been observed successfully with the thermometer. The results shows that the thermometer has great potential for measuring the thermal diffusivity, thermal conductivity, and specific heat capacity of microscale substances at low temperatures based on the periodic heating and pulsed laser heating methods. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder, Colorado, U.S.A.     

Mathematical Model for high temperature properties of cast nickel superalloys with high content of gamma prime phase

This investigation relates to structural cast superalloys with improved oxidation resistance in the temperature range of 1100–1200°C. It was tried to clarify the role of heavy metal elements on mechanical properties of an alloy in the system Ni-17at% Al-3at% Cr-Mo-Ta-W. Solidus temperature, yield strength at 20°C, ultimate tensile strength at 1200°C of polycrystal alloys and creep-rupture life at 1000°C and 1200°C of single crystals <001> were investigated by means of experimental design and regression analysis techniques, It was determined that solidus temperature do not depend from W content, yield strength at 20°C and ultimate tensile strength at 1200°C strongly depend on Ta and W contents. The properties sharply increase with simultaneous adding of Ta+W. At 1200°C Mo content is a critical factor. The influence of alloying with Ta and W on the creep resistance of single crystals was examined. With increase of test temperature dependence of creep resistance from refractory additives appears to increase, but interval of an optimum alloying narrows.     

Performance characterisation of a small milk cooling system with ice storage for PV applications

The presented work proposes a calculation method to estimate the transient performance of a small on-farm milk cooling system for PV applications. The system employs 3 kg ice for fast cooling of 17 L milk in conventional 20-L-milk-cans. Two units of a commercial DC refrigerator operate at −10 °C and at 4 °C for ice production and milk preservation respectively. The development of milk temperature and energy consumption during a cooling event was studied experimentally at different ambient temperatures of 20 °C, 30 °C and 40 °C. A computational model was developed and validated where thermal resistances and COP were adjusted with experimental data. The results between 20 °C and 40 °C ambient temperature show a COP reduction of around 30% and a total daily energy consumption increase of around 100%. The specific total energy consumption of the system per litre milk was between 30 Wh/L and 58 Wh/L for the studied ambient temperature range. The suggested model can be used for the optimisation of photovoltaic stand-alone systems at specific locations.     

Low-temperature sintered pollucite ceramic from geopolymer precursor using synthetic metakaolin

In this article, pollucite ceramic with high relative density and low coefficient of thermal expansion (CTE) was prepared from Cs-based geopolymer using synthetic metakaolin. Crystallization and sintering behavior of the Cs-based geopolymer together with thermal expansion behavior of the resulted pollucite ceramic were investigated. On heating at 1200 °C for 2 h, the amorphous Cs-based geopolymer completely crystallized into pollucite based on crystal nucleation and growth mechanism. Selected area diffraction analysis and XRD results confirmed the resulted pollucite ceramic at room temperature was pseudo-cubic phase with superlattice structure. Compared with Cs-based geopolymer using natural metakaolin, geopolymer using synthetic metakaolin in this article showed a much lower viscous sintering temperature range, which started at 800 °C, reached a maximum value of ?7.47 × 10^?4/°C at 1121.9 °C, and ended at 1200 °C. Cesium volatilization appeared only when temperature was above 1250 °C. Therefore, densified pollucite ceramic can be prepared from Cs-based geopolymer using synthetic metakaolin without cesium volatilization. Abnormal thermal shrinkage of pollucite ceramic was observed at temperature range from 25.3 to 54.6 °C because of pseudo-cubic to cubic phase transition, and its average CTE was 2.8 × 10^?6/°C from 25 to 1200 °C.     

Influence of solutionising and aging temperatures on microstructure and mechanical properties of cast Al–Si–Cu alloy

Abstract

This paper presents the influence of solution and aging temperatures on the microstructure and mechanical properties of 319 secondary cast aluminium alloy. Experimental alloy was subjected to different heat treatment cycles. Heat treatments were designed with two solutionising temperatures (504 and 545°C) at two solutionising times (4 and 8 h), followed by quenching in water at 60°C and artificial aging. The artificial aging was carried out at two temperatures (200 and 154°C) for 6 h. The improvement in mechanical properties was obtained with low solution temperature (504°C) for 8 h followed by quenching in water to 60°C and aging at low temperature (154°C). The increase in the solutionising temperature from 504 to 545°C was recommendable only for short solutionising time (4 h). Increase in the aging temperature from 154 to 200°C has led to the increase in hardness with the corresponding decrease in ductility. Aging under unfavourable conditions (prolonged aging at high temperature) caused coarsening of spheroidised eutectic silicon crystals and precipitated particles resulted in deleterious effect on the tensile strength.