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Fixed-bed tubular reactors are used widely in chemical process industries, for example, selective hydrogenation of acetylene to ethylene in a naphtha cracking plant. A dynamic model is required when the effect of large fluctuations with time in influent stream (temperature, pressure, flow rate, and/or composition) on the reactor performance is to be investigated or automatically controlled. To predict approximate dynamic behavior of adiabatic selective acetylene hydrogenation reactors, we proposed a simple 1-dimensional model based on residence time distribution (RTD) effect to represent the cases of plug flow without/with axial dispersion. By modeling the nonideal flow regimes as a number of CSTRs (completely stirred tank reactors) in series to give not only equivalent RTD effect but also theoretically the same dynamic behavior in the case of isothermal first-order reactions, the obtained simple dynamic model consists of a set of nonlinear ODEs (ordinary differential equations), which can simultaneously be integrated using Excel VBA (Visual BASIC Applications) and 4th-order Runge-Kutta algorithm. The effects of reactor inlet temperature, axial dispersion, and flow rate deviation on the dynamic behavior of the system were investigated. In addition, comparison of the simulated effects of flow rate deviation was made between two industrial-size reactors. [ABSTRACT FROM AUTHOR]

Highlights: [•] We analyze and compare journal statistics of selected ASEAN countries and Japan. [•] Japan comes first in GDP and the total number of papers. [•] Singapore comes 1st in papers per million population and papers per billion GDP. [•] We cover research on nanomaterials, including nanoparticle technology, in Thailand. [•] We introduce applications of nanomaterials/nanoparticles in Thailand. [ABSTRACT FROM AUTHOR]

Abstract: For controlling fugitive dust emitted from stone quarrying plant, the dust collection efficiency of a simple wetted screen with mesh size of 250μm under various conditions of air velocity and inlet dust concentration was experimentally examined. It has been found that without the water supply the collection efficiency of dried screen ranged only from 4% to 12%. However, the wetted screen with a water flow rate of 810(cm3/sec)/m2 could provide the collection efficiency which was increased up to 82% depending on the inlet dust concentration. With the shuttering action of water film on the wetted screen, a maximum collection efficiency of 95% could be achieved as long as the water film could be maintained. [Copyright &y& Elsevier]

Abstract: A deterministic model to predict the inertia-interceptional dust removal efficiency of open-space water spraying is developed based on momentum and mass balances of water droplets and dust particles. The effect of polydisperse dust particles and water droplets generated by different nozzles on the total removal efficiency (η total ) is examined. The small water droplets with narrower distribution could provide the acceptable removal of dust particles while the relatively large dust particles also provide the large η total value. The η total predicted by the developed model is in the range of 19.6–23.8% with a relative error of 2% when compared with the measuring data. The η total with the use of polydispersity of water droplets and dust particles is more accurate than that with the use of average size of water droplets and dust particles. [Copyright &y& Elsevier]

Abstract: Hydroxyapatite (HAp) has been synthesized by various methods, such as co-precipitation, sol–gel, and microemulsion. However, particle size, particle size distribution and cost were drawbacks of those techniques. In this study, HAp nanoparticles were prepared by means of emulsion liquid membrane system (ELM) or water-in-oil-in-water system (W/O/W). The aim of the work was to evaluate the preparation of HAp nanoparticles using ELM consisting of Span 20 and Tween 80 as a mixture of biodegradable surfactant and caproic acid as an extractant. The effect of Ca/P ratio, reaction temperature, and calcination temperature on the characteristics of synthesized particles was investigated. The synthesized HAp particles were amorphous calcium deficient apatites. Ca/P molar ratio of the synthesized particle (Ca/Pp) increased with increasing initial Ca/P molar ratio (Ca/Pi) and reach maximum at Ca/Pp of 1.65. We found significant amount of β-TCP in the particles prepared with high initial Ca/Pi molar ratio of 2.00 at which the undesired reactions at high Ca2+ concentration occurred. Increasing of reaction and calcinations temperature resulted in the reduction of surface area. After thermal treatment at temperatures ranged from 450 to 750°C, the specific surface area reduced from 227 to 58m2/g. At temperature of 750°C, we found that the morphology of microsized particles instead of nanosized ones. [Copyright &y& Elsevier]

Abstract: Unlike ordinary filters, the initial high collection efficiency of the electret filter (E) might briefly fall as dust load increases. Here, the electrical enhancement factor of the electret fiber under dust-loaded conditions for uncharged and charged particles is obtained from published experimental results. It is found that the collection efficiency of the electret fiber can be approximated as the sum of the electrical and mechanical collection efficiency. The predicted values of E are shown to agree well with reported experimental observations for both uncharged and charged particles. [Copyright &y& Elsevier]

The aerodynamics of particles and heat transfer of gas-to-particles in a two-dimensional spouted bed (2DSB) with draft plates are investigated by the discrete element method (DEM). The physical properties of the particles are similar to those of shelled corn. The calculated minimum spouting velocity and pressure drop agree well with the empirical correlations proposed by Kudra et al. The particle circulation rate increases when the friction coefficient decreases or the separation height increases. The draft plates can reduce the minimum spouting velocity and pressure drop. They also increase the maximum spoutable bed height. The effect of taking out the draft plates on the spouting phenomenon is investigated. The mixing of a 2DSB without draft plates of 10000 particles is better than that of 26000 particles. In our simulation, the gas-to-particle heat transfer is investigated. The Ranz–Marshall correlation and the correlation of Sartori et al. are applicable in the spout region and the downcomer region, respectively. The gas-to-particle heat transfer occurs mainly in the central or spout region, as reported by Freitas and Freire. [ABSTRACT FROM AUTHOR]

Abstract: The electrostatic precipitator (ESP) is the most prevalent application for corona as ion source. ESP is widely used in industrial dust collection and home ventilation systems for cleaning gas streams. However, ESP has not been used to remove gas pollutants from a gas stream. Electron attachment is one of the promising techniques for gas purification. Electron attachment reactions occur when low-energy electrons generated in a corona-discharge reactor are captured by electronegative impurities such as acetaldehyde and fine particles to produce negative ions and charged particles. The negative ions and charged particles drift in the electric field to the anode (reactor wall) and are removed by deposition there. Moreover, O−, O radical, ozone, and OH− are also generated when the carrier gas is humid air. These anions and radicals also contribute to the removal efficiency. Though acetaldehyde (CH3CHO) and ammonia (NH3) are emitted at high temperature from a crematory furnace, there is insufficient report on the effect of high temperature and simultaneous removal. The present research experimentally investigates the technical feasibility of using corona discharge reactions to treat high-temperature exhaust gas containing acetaldehyde and ammonia. The simultaneous removal efficiency of these gases from nitrogen and air is obtained experimentally. The experimental results reveal that the presence of oxygen does significantly enhance the overall removal efficiency. Similarly, it is found that the presence of water vapor also enhances the removal efficiency of the target gases from the nitrogen–oxygen mixture. The generation of undesirable byproducts such as NO x is also investigated. The present technique should be applicable to the simultaneous removal of different nanoparticles at high efficiency. [Copyright &y& Elsevier]

Abstract: The electret filter is composed of permanently charged electret fibers highly capable of collecting charged and uncharged nanosize particles. Compared to the ordinary non-electret fiber, the aerosol collection efficiency η of the electret fiber can initially be significantly higher. In our previous study, η of the electret fiber under dust loading is found to be approximated as the sum of the electrical and mechanical collection efficiencies. It is also shown that the former efficiency can be approximated as a logarithmic function of the dust load. Since the expensive electret filter cannot practically be cleaned and re-used, it is crucial to lengthen its service life without compromising its collection efficiency. In the present study, the time-dependent dust-loaded collection efficiencies of four electret filters with the same average packing density of 0.04 but different linear spatial distributions of the packing density along the filter thickness (0.04 throughout, front 0.03–back 0.05, front 0.02–back 0.06, front 0.01–back 0.07) are simulated and compared. The maximum penetrations and clogging points of the four filters are different. At the maximum 4% penetration through filter D (front 0.01–back 0.07) is two times higher than filter A (0.04 throughout), but the dust load at clogging point of filter D is about 4 times higher than filter A. The results show a significant difference in the distributions of the mass deposited particles along the filter thickness as time passes. As a result, it is possible to quadruple the filter service life by packing the filter loosely on the inlet side and progressively more densely towards the outlet side, while maintaining a sufficiently high aerosol collection efficiency at all times. [Copyright &y& Elsevier]

The present work experimentally investigates the individual and combined effect of O2 and H2O vapor on the separate and simultaneous removal of styrene and NH3 from N2 at elevated temperatures via corona-discharge reactions. Styrene and NH3 are chosen to represent the trace components in crematory emission because they are chemically dissimilar. Since the crematory emission always contains some O2 and H2O at elevated temperatures, their effects and the effect of elevated temperature are of practical interest. It is found that the presence of O2 in N2 always enhances the removal of styrene and/or NH3 from N2. The presence of H2O in N2 generally enhances the removal of styrene and/or NH3 but its presence retards that of NH3 when H2O concentration is too high or the temperature is 300 °C. The combined effect of O2 and H2O is found to substantially retard the removal of styrene and/or NH3 compared to the sole effect of coexisting O2. The general effect of elevated temperature is to decrease the removal efficiency of styrene and/or NH3 compared to the case of room temperature. [Copyright &y& Elsevier]

In a previous study to investigate how the morphology of particles accumulating on an electret fiber evolves and affects the collection efficiency of the filter at dust-loaded condition, a three-dimensional stochastic model is utilized to simulate the deposition and agglomeration of particles on a cylindrical electret fiber via two different electrical effects, namely, induced force (for uncharged particles) and Coulombic force (for charged particles). In the present study, the additional effect of Brownian diffusion is incorporated in the model and the morphology of particle agglomerates obtained in the simulated results is found to agree well with experimental observations obtained by Hiragi and Kanaoka et al. for both uncharged and charged particles. In addition, the ratio of dust-loaded collection efficiency, η, to the clean-fiber collection efficiency, η0, can still be approximated as linear function in the case of weak electrical effects. However, when the electrical parameters are large, the normalized collection efficiency has to be represented by two linear relations, i.e., at low dust load and high dust load. Estimates of the initial collection efficiency and efficiency enhancement factor are given graphically and tabulated as function of Peclet number, the interception parameter and the two electrical parameters. [Copyright &y& Elsevier]

This paper presents analytical partial derivative equations required for multicomponent critical point calculation. These partial derivative equations follow the computational scheme developed by Heideman and Khalil, but extended to excess free energy mixing rules. The mixing rules implemented in this paper are the Wong–Sandler (WS), the modified Huron–Vidal first and second orders mixing rules. The Peng–Robinson equation of state and the NRTL activity model are used in all calculations. However, the calculation based on the derivative is not limited to the mixing rules referred in this paper. It can also be applied to any other mixing rules. It is found that the calculations using these analytical partial derivative equations are superior, in computation time and reliability, that using the numerical partial derivative equations. [Copyright &y& Elsevier]

A simplified mathematical model consisting of ordinary differential equations has been proposed and found to accurately predict the dynamic performance of a honeycomb rotary absorption-type dehumidifier in a beverage factory. The model was validated experimentally using the transient measurement data on the air properties at the outlets of both the dehumidification and regeneration sections. Good agreement between the predicted and recorded data at each time has been observed. The model is numerically stable and easy to simulate. [Copyright &y& Elsevier]

Focuses on the 2000 Asian Particle Technology Symposium which was held from December 13 to 15, 200 in Bangkok, Thailand and its impact on particle technology in the country. Reason for the selection of Bangkok as venue of the symposium; Contributions of the Thai Powder Technology Center of Chulalongkorn University to particle science and technology.

Three kinds of quantitative indices, i.e. the degree of mixedness, an area-based criterion and the box-counting fractal dimension, have been investigated to find out their suitability for evaluating the degree of dispersion of single additives in compounded material. The Monte-Carlo technique is used to simulate various ideal and non-ideal cases of dispersion in single-additive systems. It has been found that the value of both the area-based criterion and box-counting fractal dimension are essentially independent of the particle size of the additive, so they are suitable quantitative indices for evaluating the degree of dispersion of single-additive systems. The investigation also shows how the fractal dimension can be used to characterize and interpret the degree of dispersion of a pigment in a polymer matrix obtained experimentally. [ABSTRACT FROM AUTHOR]

A novel gliding arc discharge method using zinc particle as a solid precursor was used to coat poly methyl methacrylate (PMMA) particles to provide an adjustable electrical conductivity. An AC voltage of 4.5 kV was applied to the electrodes and 2 L min −1 of argon gas was injected to generate the gliding arc discharge. By using a combination of spouted bed condition and gliding arc discharge, a rapid coating performance was achieved. After 5 min of coating process, PMMA particles were observed to be covered by a fine zinc layer. The amount of coating increased at the beginning of the process and became relatively constant after 20 min. The amount of zinc coating was found to be approximately 10 mg/1 g of PMMA particle at a coating time of 10 min and 0.10 zinc/PMMA mass ratio in the bed. The percentage of zinc surface coverage was calculated to be 60% with a thickness of 140 nm. The coated samples exhibited electrical conductivity, approximately 3.7 × 10 −1 S m −1 at zinc/PMMA mass ratio of 0.15 with a thickness of 195 nm and a surface coverage of 75%. The amount of zinc coating showed a proportional relationship with both coating duration and zinc/PMMA mass ratio in the bed. The increase in the amount of zinc coating resulted in an increase of coating thickness, which further resulted in an increasing electrical conductivity of the coated polymer. The proposed method shows a promising potential for particle coating process. [ABSTRACT FROM AUTHOR]

Proposed synergistic use of a combined medium of molten salt and Ni/Al 2 O 3 ( MS-Ni ) was investigated for its enhancement of cellulose pyrolysis for high-quality syngas production. Clean renewable solar energy is to be stored at a high temperature in molten salt ( MS ) and provides the heat of pyrolysis. The MS-Ni medium could increase H 2 yield by 3-folds while CO yield slightly increased by 15%, compared to the case of only MS medium. The peak rate of H 2 production nearly quadrupled while the peak rate of CO production increased 2.5 times at about 150 and 80 K lower temperatures, respectively. The ratio of selectivity of syngas to undesired CH 4 was nearly doubled. Arrhenius rate expressions for pseudo-first-order pyrolytic reaction are derived from the experimental data to give activation energies of 206 and 128 kJ mol −1 for the MS and the MS-Ni mediums, respectively. The experimental results clearly validated the role of MS-Ni as a synergistic medium for high-quality syngas production from cellulosic biomass pyrolysis. [ABSTRACT FROM AUTHOR]

Catalytic enhancement of syngas production rate and yield by combined ternary eutectic carbonate salt–Ni/Al 2 O 3 ( MS-Ni ) medium was investigated by CO 2 gasification of cellulose, biomass wastes (chopstick, newspaper, sawdust), and sawdust char in a lab-scale reactor. Compared to the case of only molten salt ( MS ), MS-Ni medium could increase syngas production yields of the above-listed 5 feedstock by 28, 23, 18, 17, and 12%, respectively, at 1173 K. In fact, H 2 production yield increased by up to 300% while the CO production yield slightly increased by 10–15% with the temperature at peak rate shifted lower by approximately 100 K. Arrhenius rate expressions for char gasification were derived to give activation energies of 125 and 105 kJ mol −1 for the MS and MS-Ni mediums, respectively. The Ni/Al 2 O 3 catalyst in MS-Ni medium was not only active for H 2 production but also could enhance CO production. The reaction mechanism of CO 2 gasification of cellulose in MS-Ni medium was schematically proposed. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogel based oil encapsulation was attempted with a ternary system of colloidal chitosan, κ-carrageenan, and carboxymethylcellulose sodium salt (NaCMC). Favourable formulations of this ternary system that caused irreversible sol–gel transition by freezing (cryogelation) were found in this study, and the oil phase that contained a selected model food ingredient (curcumin) was successfully encapsulated in this prepared cryogel matrix. The encapsulation yields were found to vary from ca 89–99%, and the values were influenced by the cooling protocol used during freezing, thereby indicating that the gel formation kinetics was intimately related to the degree of encapsulation. The release behaviours of the ingredient were investigated in aqueous systems. The release curves showed that both a burst release and a first order release were achieved simply by changing the freezing condition. Freezing could modify the gel formation of the present cryogel, and the resulting structural modification evidently controlled the oil encapsulation manner. Prepared cryogels were found to be sensitive to the ambient pH. It was suggested that the ternary system of chitosan, κ-carrageenan, and NaCMC is an interesting matrix for designing controlled release system. [Copyright &y& Elsevier]

Abstract: Cryogel based encapsulation of curcumin, an herbal extract, was successfully carried out with a ternary system of colloidal chitosan, κ-carrageenan, and carboxymethylcellulose sodium salt. The effects of chitosan concentration, κ-carrageenan/CMC ratio of the polymer suspension and molecular weight of chitosan on the sol–gel formation were investigated. The effects of cooling rate during freeze-drying and oil phase composition on the encapsulation yield and the release behavior of curcumin from the hydrogel were determined. And so were the effects of pH of the phosphate-buffered media and oil phase composition on the swelling of the specimens. The microstructure of the resulting specimens revealed core-shell nanoparticles (i.e. oil droplet for core and cryogel membrane for shell) entrapped in the cryogel matrix. The encapsulation yield for two types of suspensions was in a range of 83.9 to 99.6% when a high-MW chitosan was used. Controlled release of the encapsulated curcumin in an aqueous system could be maintained for 4days, and the releasable amount of curcumin was in a range of 41.1 to 59.9%. The encapsulation yield as well as the released pattern and releasable amount of curcumin were significantly influenced by the cooling protocol used during freezing. Irrespective of the introduced oil phase composition, controlled release of curcumin was achievable when the cooling rate was sufficiently high at −2.0°C/min and, interestingly, either a burst release or a first order release could simply be achieved by changing the freezing condition. [Copyright &y& Elsevier]

Abstract: In the present study, a thermodynamic analysis of the autothermal reforming of dimethyl ether (DME) for the production of hydrogen was carried out. The results clearly indicated that the carbon formation behavior, the boundary conditions between coke-free and coking regions, and the equilibrium composition of the reformate were dependent on the steam/DME ratio, O2/DME ratio, temperature, and pressure of the system. For instance, carbon formation was effectively suppressed as the steam/DME ratio increased from 0 to 5, the O2/DME ratio increased from 0 to 3, or the temperature rose from 100 to 1000°C. In contrast, carbon formation was enhanced as the pressure was increased from 0.5 to 10atm. The boundary temperature of coke-free operation decreased with an increase in the steam/DME and O2/DME ratios. More specifically, at a steam/DME ratio of 3–5 and an O2/DME ratio of 0–3, the boundary temperature ranged from 50 to 280°C (when CH4 formation was promoted) and 380 to 670°C (when CH4 formation was suppressed), respectively. Furthermore, at elevated temperatures, H2 and CO formations were enhanced, and CH4 formation was inhibited. The addition of steam enhanced H2 production while reducing CO formation. On the contrary, an increase in the O2/DME ratio reduced H2 production while enhancing CO formation. Interestingly, the desired temperature for thermo-neutral condition, in which energy consumption was zero, can be achieved by correctly controlling the O2/DME and steam/DME ratios. [Copyright &y& Elsevier]

A three-phase fluidized bed equipped with a turbine agitator was utilized as a simple device for disrupting bakers’ yeast cells (Saccharomyces cerevisiae). The degree of yeast cell disruption was evaluated based on the number of broken cells and its validity was confirmed by the total amount of crude soluble proteins released and by microscopic observation. It was found that the equipment could yield 90% of yeast cell disruption. With the presence of glass beads, the degree of cell disruption became higher as agitating speed is increased. The disruption enhancement would be attributed to the grinding effect resulting from the interaction between yeast cells and glass beads. One-thousand micrometers of glass beads yielded a higher degree of disruption than larger ones. An increase in liquid flow rate hindered the degree of disruption because of shorter contact time although the shear rates in the yeast suspension would become more rigorous. [Copyright &y& Elsevier]

Abstract: The pyrolysis behaviors of rice straw, rice husk, and corncob have been investigated with the TG-MS technique, while paying close attention to the gas formation during the pyrolysis. The weight decreasing profiles and the gas formation rates were significantly different among the samples although their elemental compositions were almost the same. It was found that H2O is the main product formed for all the samples. The differences in the gas formation rates were found to be due to their differences in the composition of hemicellulose, cellulose, and lignin. There were significant interactions between cellulose and lignin during the pyrolysis. The interactions between cellulose and lignin during the pyrolysis contributed to a decrease in tar yields but an increase in char yields. From the gas formation data and FTIR analyses of the chars, it may be concluded that the suppression of tar formation during the pyrolysis of biomass was brought about by the cross-linking reactions between lignin and cellulose to form H2O and ester groups during the pyrolysis. [Copyright &y& Elsevier]

Abstract: A mathematical model was developed to describe the effects of temperature on the kinetic parameters of ethanol fermentation by the flocculating yeast, Saccharomyces cerevisiae M30, using cane molasses as the substrate. Three state variables, biomass, ethanol and the substrate and 12 kinetics parameters were used to describe the phenomenon. The kinetic parameters of the model were determined by using the least-square method. The influence of temperature and initial sugar concentration on cell activities was investigated and quantified. Arrhenius relationships between operating temperature and the maximum specific growth rate, specific production rate, specific death rate were then established. The activation energy for growth, ethanol production and death rate were 3.461×104, 3.496×104 and 1.777×105 kJ/kmol, respectively. Polynomial equations were established for the effects of temperature on the other kinetic parameters. A high temperature led to a decrease in the ethanol and cell yields but an increase in the inhibition effect of ethanol and sugar on cell growth and ethanol production. In addition, an inhibition effect of the initial sugar concentration on cell growth was clearly observed. The adopted mathematical model could describe very well the dynamics of ethanol fermentation from the beginning up to the stationary phase. [Copyright &y& Elsevier]

Six types of activated carbons were prepared from coffee residues by varying activating agents of zinc chloride, nitrogen, carbon dioxide and steam. Characterization of these samples was performed by using nitrogen adsorption isotherms, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) in order to understand the coffee residue activated carbon and its adsorptive capacity. All of activated carbons and one commercial activated carbon (CH-I1000) were subjected to the adsorption of formaldehyde vapor. The coffee activated carbon prepared with ZnCl2 impregnation and nitrogen activation (CZn一N2) demonstrates its highest capacity of formaldehyde adsorption owing to the hydrophilic functional groups of O一H, C＝O, C一O on the surface. The coffee activated carbon prepared with ZnCl2 impregnation coupled with carbon dioxide activation (CZn一N2一CO2) yields the highest total surface area (914 ± 21 m2/g) and total pore volume (1.010 ± 0.003 cc/g) with the hydrophobic groups on the surface adsorbed formaldehyde less than CZn一N2. Therefore, we conclude that the formaldehyde adsorption by activated carbons in this work is affected by surface chemistry more than texture characteristics of surface area and pore volume. [Copyright &y& Elsevier]

In this work, we investigated the preparation and utilization of coffee residues binding with clay as adsorbent (hereafter called CC-adsorbent) for removal of heavy metal ions in solution. Factors affecting the adsorption such as pyrolysis temperature, weight ratio of coffee-residue to clay and particle size were investigated in the present preliminary study on the adsorption of metal ions. The pyrolysis temperature of 500 °C, weight ratio of coffee residue to clay of 80:20, and particle size diameter of 4 mm were found to be the suitable conditions in our work. At this condition, the adsorption capacities of the CC-adsorbent for Cd2+, Cu2+, Pb2+, Zn2+ and Ni2+ were determined by the Langmuir isotherm model. The adsorption increased in the order of Cd2+>Cu2+>Pb2+>Zn2+>Ni2+. The effects of solution pH (8–10) and temperature (30–80 °C) on the adsorption of Cd2+ were investigated. The Cd2+ adsorption increased with increasing pH and temperature, and remained constant at high pH. The heat of adsorption (ΔH=−1.11 kcal/g) implied that the adsorption was physical exothermic adsorption. Desorption was easily achieved by leaching with distilled water which gave the recovery yield 88–92%. The functional groups studied by FTIR indicated that hydroxyl, carboxyl and amine groups were the main functional groups. Electrical potential study showed that the CC-adsorbent exhibited negative charge that was favorable to attract metal ion. The surface and pore study implied that the high fraction mesopores in the granular CC-adsorbent contributed to the adsorption capacity. [Copyright &y& Elsevier]

Forced convective jet applied onto carbon arc plasma has significant effects on the formation of carbon nanoparticles (CNPs) containing multiwalled carbon nanotubes mixed with multishelled nanoparticles produced by the “arc in water” method. There is an optimized flow rate of the convective jet that leads to the highest production yield, largest hydrodynamic diameter of the products, and the reduced crystalline defects. With the convective flow rate of 1.36 dm3/min, the highest yield and production rate of CNPs could be obtained at 48.5% and 9.32 g/h, respectively. These effects of the forced convective jet originate from the enhanced quenching of carbon clusters vaporized from graphite anode. Analysis of convective flow field subjected to the arc plasma zone is conducted to indicate that synthesis of CNPs by the arc in water method can be elaborately controlled. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Nanostructured ferrite spinels AFe2O4 (A = Co, Ni, Zn) were successfully synthesized via a co-precipitation method using oxalate salt as a precursor in an anionic surfactant system in combination with a simple calcination process. High crystallinity samples of nanoparticle spinels in a grain size range of 15–100 nm were obtained by varying the calcination temperature (300–700 °C) and time (1–5 h). Their pore sizes were controlled in a range of 3 nm up to a hundred nm by tailoring the calcination conditions. Raising the calcination temperature was found to decrease the Brunauer–Emmett–Teller (BET) surface area, and broaden the pore structure due to enhanced crystal growth and agglomeration of interparticles of spinels. Transmission electron microscopy (TEM) images of ferrite spinels calcined at 300 °C showed mesoporous structures with narrow pore size distribution, and the maximum BET surface area of CoFe2O4, NiFe2O4 and ZnFe2O4 were found at 201 (Co), 315 (Ni), and 273 (Zn) m2 g−1, respectively. The magnetic hysteresis loops of the ferrite spinels at room temperature demonstrated ferromagnetism in CoFe2O4, superparamagnetism–ferromagnetism in NiFe2O4, and paramagnetism in ZnFe2O4. The highest saturation magnetization (M s), remanent magnetization (M r), and coercivity (H c) were obtained from high crystallinity spinels calcined at 700 °C. Nanostructured AFe2O4 with high surface area and mesoporosity promises potentials as novel magnetic catalysts. [ABSTRACT FROM AUTHOR]

EVOH/clay nanocomposite films were prepared by using four types of surfactants to treat surface of clay because the surfactants were expected to affect the degree of clay dispersion in the EVOH matrix, which would in turn affect the properties of film. The nanocomposite films that contained the single alkyl tail with two repeating units of oxyethylene surfactants or single alkyl tail surfactant showed higher tensile strength, tensile modulus and elongation at break than those with 15 repeating units of oxyethylene surfactants or those with double alkyl tail surfactant. [ABSTRACT FROM AUTHOR]

Abstract: Hierarchical micro-/macroporous carbon monoliths are prepared as enzyme carriers for flow-through process. The immobilization of Candida rugosa lipase on micro-/macroporous carbon monoliths is studied. Lipase is immobilized by physical adsorption which lipase solution is circulated through the micro-/macroporous carbon monolith. An accessibility of lipase to the surface inside the micro-/macroporous carbon monolith is enhanced by flow-through method which promotes enzyme–surface interaction and finally leads to rapid enzyme immobilization. After immobilization is conducted for 10min, the maximum protein binding can be measured. In terms of substrate-immobilized lipase reactions, flowing of substrate through lipase immobilized micro-/macroporous carbon monolith promotes high efficiency in both reaction and product withdrawal. Moreover, at high flow rates of lipase solution in immobilization step, the lipase activity increases. Oxygenated surface of micro-/macroporous carbon monoliths support also demonstrates an interesting effect on lipase immobilization and biocatalyst activity. The initial reaction rate of lipase immobilized on oxygenated surface carbon monolith support has higher activity compared with normal surface. [Copyright &y& Elsevier]

Abstract: Freeze-dried porous solid foams were prepared from carbon nanotube (CNT) suspensions via either contact freezing with a heat exchanger or immersion freezing into a cryo-bath. Microstructures in the freeze-dried foam cast by ice crystals formed during the freezing step. It was found that domains of the carbon nanotubes in the freeze-dried solid foams were fairly well interconnected, and the microstructures were largely influenced by the freezing condition and freezing method. A mathematical model was proposed to simulate the observed thermal history during the freezing step; then theoretical predictions of the microstructural features were attempted. The simulated thermal history was in good agreement with experimental result. The resulting mean ice crystal sizes L* could be estimated from the calculated freezing front velocity (R) and the temperature gradient in the frozen zone (G). Interestingly, it was found that a correlation based on the power law (L*∝R −0.2 G −0.2) was applicable to the present system for both the contact and immersion freezing methods. Though the fundamental ice crystallization phenomena were essentially the same for both freezing methods, actual temperature distribution and movement of the freezing front through the whole freezing bulk could control the morphology of ice crystal in the frozen matrix. In other words, good control of thermal flow in the freezing system would greatly contribute to rational design of microstructures of the CNT foam. [Copyright &y& Elsevier]

Abstract: Carbon-coated silica gel beads could be prepared by immersing porous silica gel beads in a resorcinol–formaldehyde (RF) aqueous solution and then following by drying and pyrolysis in nitrogen atmosphere. With the proposed method, deposition of colloidal nanoparticles formed during the sol–gel polycondensation of the RF solution was successfully prepared on the mesopores of the silica gel beads. Both size and concentration of the colloidal particles could be controlled by the gelation time and the mixing ratio (V EtOH /V RF ) of the RF solution to ethanol. The porous characteristics of the prepared carbon-coated silica gel beads and the amounts of deposited carbon could be controlled by changing V EtOH /V RF. Without any significant decrease in mesoporosity, the maximal carbon contents of carbon-coated silica gel beads could be increased up to 18wt% in the inner part and 53wt% on the outer surface, respectively. [Copyright &y& Elsevier]

Abstract: The hydrothermal process coupled with sonication pretreatment has been employed to synthesize titanate nanostructures, including nanotubes and nanowires. By varying size of raw TiO2 powder (400nm and 1μm), reaction temperature (90–180°C), and sonication power (0–38W), morphology of titanate nanostructures, length of titanate nanotube, and phase of titanate nanowire could be adjusted. Transmission electron microscope (TEM), nitrogen adsorption, and X-ray diffraction (XRD) were employed to analyze structure, specific surface area, and crystalline phase of the synthesized products. The titanate nanostructures transformed from the smaller TiO2 particles provided higher specific surface area and shorter tube-length than those transformed from the larger ones. Morphology of titanate product transformed from TiO2 spherical particle to titanate nanosheet, nanotube and nanowire with the gradual increase in the reaction temperature. The surface area of the samples corresponded well with the amount of titanate nanotube (hollow) and nanowire (non-hollow), whilst the length of titanate nanotube became longer with the applying sonication pretreatment. Interestingly, the formation of brookite phase was observed for the titanate nanowire synthesized at 180°C with sonication pretreatment. [Copyright &y& Elsevier]

Abstract: The utilization of naphthalene as an alternative carbon source for synthesis of carbon nanoparticles by pyrolyzing with ferrocene in a quartz tube reactor was experimentally investigated. Carbon nanoparticles including carbon nanotubes (CNTs) and carbon nanocapsules (CNCs), which contained Fe particles in their carbon shells, were simultaneously fabricated. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses revealed that morphology and size of the carbon nanostructure strongly depended on the pyrolysis temperature. At a higher temperature, formation of CNCs would become more enhanced. Particle size distribution and yield of the synthesized products were also significantly influenced by the pyrolysis temperature. [Copyright &y& Elsevier]

Abstract: A new strategy for single-step synthesis of copper and carbon nanoparticle composite by arc discharge in liquid nitrogen was proposed. The synthesized products consist of carbon nanoparticles (CNPs) which include multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanohorns (SWCNHs) and multi-shelled carbon nanocapsules (MSCNCs) containing Cu clusters inside. Evidence of transmission electron microscopic analyses reveal that under with arc current of 180A arc discharge between copper and graphite electrodes in liquid nitrogen could provide MSCNCs with narrow size distribution in a range of 70–150nm. Meanwhile, MWCNTs with diameter of 20–40nm and length of 150–350nm became selectively synthesized under the condition of discharge in liquid nitrogen with arc current of 100A. Spectroscopic analyses confirm that copper nanoparticles are cuprite while BET analyses also reveal that the synthesized nanocomposite possess acceptably high specific surface area. [Copyright &y& Elsevier]

Abstract: Effect of monoolein surfactant which promotes n-hexane to dissolve in water was investigated to enhance the carbon nanoparticle (CNP) synthesis by arc discharge in liquid. The production rate of CNPs consisting of multi-shelled fullerenes and multi-walled carbon nanotubes was increased by the addition of the n-hexane to water with support of monoolein surfactant. An optimal amount of monoolein led to the maximal production rate of CNPs which was ca. two-fold higher than that obtained from a pure water system. This effect is ascribed to the role of n-hexane and monoolein to provide carbon clusters to the arc reactive zone. The hydrodynamic particle sizes of CNPs and their crystallinity were also enhanced by the addition of these organic compounds. As the vapor pressure of the organic component is significantly suppressed, the proposed method is much safer than that using pure organic liquid. [Copyright &y& Elsevier]

Abstract: A two-step direct and simple method for the preparation of a hierarchical porous carbon monolith with micropores, mesopores and macropores is described. The two stages give more flexibility in the preparation of a porous carbon monolith. In step I a macroporous interconnected carbon monolith is prepared by ultrasonic irradiation during sol–gel polycondensation. The effects of sol–gel temperature, catalyst concentration and ultrasonic power on the structure of the monolith are investigated. In step II, mesopores are induced in the monolith by Ca(NO3)2 impregnation followed by CO2 activation. The effect of activation temperature is also studied. A hierarchical interconnected carbon monolith with mean pore size diameter of 1.2μm, BET surface area of 624m2/g, mesopore volume of 0.38cm3/g and micropore volume of 0.22cm3/g has been obtained from Ca(NO3)2 impregnation of the macroporous carbon monolith followed by CO2 activation at 850°C. [Copyright &y& Elsevier]

Abstract: The ‘arc in water’ reaction system which can produce carbon nanotubes and related materials was investigated using a unique condition with microgravity environment. From such condition, we can gain some information about gas emersion from the gas–liquid interface and expansion rate of gas bubble at the arc zone without condensation of water vapor. Based on the results obtained from microgravity condition together with normal gravity condition and the use of carbon-contained liquid to host the arc plasma, we modified the previous model of the relevant reaction field. Conclusively, we found that gas film is generated in the gas phase at the gas–liquid interface, and this film may block the carbon vapor to arrive the liquid phase. From this phenomenon, the products expected from direct reaction of carbon vapor with liquid components may be hardly produced. [Copyright &y& Elsevier]

Abstract: In this work, ultrasonic irradiation (with suitable reactant ratios) during gelation of RF solution is a promising technique for maintaining porous properties of carbon gels prepared by microwave drying. [Copyright &y& Elsevier]

This paper reports a study of the phase evolution induced by mechanical milling of a mixture of industrial grade La2O3, SrCO3 and Mn3O4 powders under a humid atmosphere. In this milling, no media balls were employed and the mechanical activation was applied through friction among particles in the powder mixture. Under humid atmosphere (relative humidity 70% at 25°C), X-ray diffraction peak intensities of La2O3, SrCO3 and Mn3O4 decreased, and the specific surface area of the powder mixture increased at the early stage of the milling (less than 10 min). In further milling, the perovskite strontium-doped lanthanum manganite (LSM) started to appear. Differential thermal analysis suggests that the present mechanical activation brought about the decomposition of SrCO3. Single-phase LSM was obtained by annealing of the milled powder mixture at a relatively lower temperature of 900°C and its particle size was about 100 nm. The present mechanical milling resulted in considerably lower contamination release from milling media. [ABSTRACT FROM AUTHOR]

Abstract: A mathematical model has been developed to investigate the mixing behaviors of solid particles within an inclined fluidized bed, which is a system of particular interest for applications of downcomers in circulating fluidized beds. Incorporating Newton''s second law of motion for calculating particle motion, the interaction among particles is successfully simulated using the discrete element method (DEM), in which the motion of fluid is modeled in a two-dimensional scheme and the motion of spherical particles is considered in a three-dimensional domain. Based on simulations, as angles of inclination are increased from 0°, 10°, 20° to 30° with respect to the vertical axis, the simulations demonstrate particle mixing phenomena with respect to fluidizing characteristics. The simulations provide a unique microscopic viewpoint of particle motion inside the bed, which cannot be observed experimentally easily. Fractional fluidization arising from distribution of gas flow along the cross-section of the bed has been found to be affected by the angle of inclination. Moreover, knowledge of microscopic mixing of solid particles, caused by circulating flow, has been explored. [Copyright &y& Elsevier]

Abstract: A special electrical hydro-cyclone is developed and tested. In the underflow collection box of the hydro-cyclone, it has a central metal rod electrode and a cylindrical metal wall between which the desired DC electrical potential or no potential is applied. Effect of central rod diameter and length on separation cut size was examined. The aqueous suspensions of silica particles with a median diameter of 754nm were tested using a 20mm-diameter hydro-cyclone without underflow. It was found that the zeta potential of particles increased proportionally with the value of pH. The electrical potential exhibits a stronger effect when the suspension indicates high pH value. The cut size decreases with the increase of initial pH values. This result is due to the increased negative zeta potential under high pH condition and negatively charged particles are easily collected by electrostatic force. The cut size decreases with the increase of electrode diameter. The cut size becomes smallest under high pH, large electrode diameter and long electrode length conditions. For the negatively charged particles, the center electrode should be negative polarity and outer cylindrical wall should be positive. By use of the electrostatic force, the cut size decreases about 9.2% smaller compared to the standard case without electrostatic force. [Copyright &y& Elsevier]

Abstract: Mesoporous silica materials were synthesized by sol–gel method using tetraethoxysilane (TEOS) as precursors and surfactants i.e., cetyltrimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and polyoxyethylene cetyl ether (Brij 56) as templates. Surfactant templates were completely removed by calcination to form mesoporous structure. The effects of type and amount of surfactants on the characteristics of samples were studied. The textural characteristics such as surface area, pore volume, pore size, and pore size distribution were determined by nitrogen sorption isotherms. Fourier transform infrared (FTIR) spectroscopy was employed to qualitatively identify the chemical functionality and to confirm the removal of surfactant template. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to directly observe surface morphology and mesoporous structure, respectively. The adsorption capacity of the synthesized adsorbent for toluene vapor was examined. We found that the pore volume and pore size of mesoporous materials affected the adsorption capacity. The sample prepared with high content of CTAB under basic condition (pH ) yielded large pore volumes and pore sizes and subsequently possessed the high adsorption capacity for toluene vapor. [Copyright &y& Elsevier]

Abstract: To measure the temperature of individual droplets or the average temperature in a section of a spray, the analysis of the light scattered around the rainbow angle provides an attractive approach. Up to now, the analysis of recorded rainbow signals has been carried out in the framework of the full Lorenz–Mie theory or of the Airy theory. In this paper, we consider four approaches (Lorenz–Mie, Debye, Airy and Nussenzveig approaches) to compute the light scattered around the rainbow angle, and we compare them in terms of accuracy and time-consumption. It is shown that the Complex Angular Momentum (CAM) theory proposed by Nussenzveig, modified by using empirical coefficients, allows one to accurately compute the light scattered around the rainbow angle in a large angular domain for particles with diameters as small as 10μm. [Copyright &y& Elsevier]

Acetaldehyde-laden air and phenol-contaminated water were experimentally treated using corona discharge reactions and gas absorption in a single water-film column. Mathematical modeling of the combined treatment was developed in this work. Efficient removal of the gaseous acetaldehyde was achieved while the corona discharge reactions produced short-lived species such as O and O- as well as ozone. Direct contact of the radicals and ions with water was known to produce aqueous OH radical, which contributes to the decomposition of organic contaminants: phenol, absorbed acetaldehyde, and intermediate byproducts in the water. The influence of initial phenol concentration ranging from 15 to 50 mg L-1 and that of influent acetaldehyde ranging from 0 to 200 ppm were experimentally investigated and used to build the math model, The maximum energetic efficiency of TOC, phenol, and acetaldehyde were obtained at 25.6 × 10-9 mol carbon J-1, 25.0 × 10-9 mol phenol J-1, and 2.0 × 10-9 mol acetaldehyde J-1, respectively. The predictions for the decomposition of acetaldehyde, phenol, and their intermediates were found to be in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: A new method in preparation of 3D interconnected macroporous carbon monolith has been introduced. Ultrasonic irradiation (ultrasonic intensity 78W/cm2) and low catalyst concentration (C/W=10mol/m3) of RF solution are used as an interesting and unique preparation method for 3D interconnected macroporous sonogel (gel irradiated by ultrasound at gelation stage) and/or 3D interconnected macroporous carbon monolith without using templates. [Copyright &y& Elsevier]

Abstract: Although hydrogen has a great potential as clean energy, safe practical storage of hydrogen for applications such as fuel cells has been a major challenge. NaAlH4 is one of the metal hydrides, which are candidates for hydrogen storage in vehicles. However, the rather slow absorption/desorption kinetics is still a significant drawback. To alleviate this problem, purified NaAlH4 was ground with TiCl3, ZrCl4, or HfCl4. Desorption kinetics and capacities were observed under TPD-like operation. Absorption efficiency was determined by raising the temperature up to 125°C. Of the three doped metals investigated for the positive effect on facilitating NaAlH4 decomposition, TiCl3 assists the best on the first reaction while ZrCl4 and HfCl4 do for the second one. Despite the kinetics enhancement directly involves with the ZrCl4 amount, there is a threshold of ZrCl4-content which affects. 6% ZrCl4 is considered as an appropriate amount to improve the hydrogen release because it simultaneously decreases the desorption temperature and gives the outstanding rate. In hydrogen desorption, ZrCl4 provides the most amount of released hydrogen, but for hydrogen absorption TiCl3-doped NaAlH4 possesses the highest capacity. It is believed that the metal size is one of the key factors resulting in such the behavior. [Copyright &y& Elsevier]

Abstract: ZnS nanoparticles with different morphology; spherical, ellipsoidal particles'' nanotubes and nanorods, could be successfully synthesized from quaternary W/O microemulsion system. The morphology of the final products could be clearly confirmed by the scanning electron microscopy (SEM) and the transmission electron microscopy (TEM). The effect of cosurfactant on size and morphology of the obtained products have been explored in this work. The key controlling parameters such as the molar ratio of water to surfactant (w o) and the reactant concentration, which affect the product characteristics, have also been investigated. [Copyright &y& Elsevier]