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Glass fertilizers in the phosphate systems were melted at 900-950 °C with a soaking period of 1 h. Leaching study of these glasses with a maximum time period of 300 h was conducted under Soxhlet distillation condition with distilled water. Weight loss and the leach rates of the glass fertilizer samples were calculated from BET surface area measurements. They were in the range of 6.3x10-3 to 2.3x10-3 g.m-2.h-1 at 90 °C. The effect of different modifier ions like Na+, Fe3+, Mg2+, Ca2+, and K+ in the basic phosphate networks on melting and time of melting has been found to be evident. The pH determination ranging from 4.80 up to 7.50 of the leachate solution at ambient temperature under varying time intervals showed interesting and regular variations. The leaching study of such glasses under Soxhlet condition showed Ca2+, Mg2+, and K+ to be good candidates as modifier towards faster leaching. The findings have been corroborated in terms of ionic size, ionic radius, and hence the ionic potential of the modifier ions incorporated into the glass structure. The application of glass fertilizers was made on kharif paddy. Resumo Fertilizantes de vidro nos sistemas de fosfato foram fundidos a 900-950 °C por 1 h. Foi realizado estudo de lixiviação desses vidros com um período máximo de 300 h, em condição de destilação Soxhlet com água destilada. A perda de massa e as taxas de lixiviação das amostras de fertilizantes de vidro foram calculadas a partir de medições da área superficial de BET, que foram na faixa de 6,3.10-3 a 2,3.10-3 g.m-2.h-1 a 90 °C. O efeito de diferentes íons modificadores, como Na+, Fe3+, Mg2+, Ca2+ e K+, nas redes de fosfato na fusão e no tempo de fusão foi evidente. A determinação do pH variando de 4,80 a 7,50 da solução de lixiviado à temperatura ambiente, em diferentes intervalos de tempo, mostrou variações interessantes e regulares. O estudo de lixiviação desses vidros na condição de Soxhlet mostrou que Ca2+, Mg2+ e K+ são bons candidatos como modificadores para uma lixiviação mais rápida. Os resultados foram corroborados em termos de tamanho iônico, raio iônico e, portanto, potencial iônico dos íons modificadores incorporados na estrutura do vidro. A aplicação de fertilizantes vítreos foi realizada na planta de arroz.

This study recommends Carbopol/zinc oxide (ZnO) hybrid nanoparticles gel as an efficient antibacterial agent against different bacterial species. To this end, ZnO nanoparticles were synthesized using chemical precipitation derived from a zinc acetate solution with ammonium hydroxide as its precipitating agent under the effect of ultrasonic radiation. The synthesized ZnO nanoparticles were stabilized simultaneously in a freshly prepared Carbopol gel at a pH of 7. The chemical composition, phase identification, particle size and shape, surface charge, pore size distribution, and the BET surface area of the ZnO nanoparticles, as well as the Carbopol/ZnO hybrid Nanoparticles gel, were by XRD, SEM, TEM, AFM, DLS, Zeta potential and BET instruments. The results revealed that the synthesized ZnO nanoparticles were well-dispersed in the Carbopol gel network, and have a wurtzite-crystalline phase of spherical shape. Moreover, the Carbopol/ZnO hybrid nanoparticles gel exhibited a particle size distribution between ~9 and ~93 nm, and a surface area of 54.26 m2/g. The synthesized Carbopol/ZnO hybrid nanoparticles gel underwent an antibacterial sensitivity test against gram-negative K. pneumonia (ATCC 13883), Bacillus subtilis (ATCC 6633), and gram-positive Staphylococcus aureus (ATCC 6538) bacterial strains, and were compared with ampicillin as a reference antibiotic agent. The obtained results demonstrated that the synthesized Carbopol/ZnO hybrid nanoparticles gel exhibited a compatible bioactivity against the different strains of bacteria.

High-specific-surface-area MgF2 was prepared by microwave-assisted solvothermal synthesis. The influences of the solvent and the magnesium precursors, and the calcination atmospheres, on the nanoparticle sizes and specific surface areas, estimated by X-Ray Powder Diffraction, N2 sorption and TEM analyses, were investigated. Nanocrystallized (~7 nm) magnesium partially hydroxylated fluorides (MgF2&minus, x(OH)x) with significant specific surface areas between 290 and 330 m2∙g&minus, 1 were obtained. After activation under gaseous HF, MgF2&minus, x(OH)x catalysts underwent a large decrease of both their surface area and their hydroxide, rates as shown by their 19F and 1H solid-state NMR spectra. Expect for MgF2 prepared from the acetate precursor, an activity of 30&ndash, 32 mmol/h∙g was obtained which was about 40% higher compared with that of MgF2 prepared using Trifluoroacetate method (21.6 mmol/h∙g).

Active absorbent for flue gas desulfurization was prepared from coal fly ash, calcium oxide (CaO) and calcium sulfate (CaSO4 ) by hydro-thermal process; steam and water hydration. The absorbents were examined and compared for its micro-structural properties. The experiments were conducted based on Design of Experiments (DOE) according to 24 factorial design. The effect of various absorbent preparation variables such as hydration period (Factor A), ratio of CaO to fly ash (Factor B), amount of calcium sulfate used (Factor C) and drying temperature (Factor D) towards the BET surface area of the absorbent were studied. The BET surface area of the absorbent was in the range of 12.9-169.3 m2/g. Fisher’s test showed that there is a strong influence of factor A, B and D towards the absorbent surface area, while its dependence on factor C is negligible. Comparison between absorbents prepared from water and steam hydration showed that the BET surface area of absorbents prepared from water hydration gives a higher surface area, but at a lower rate. The optimum BET surface area for the prepared absorbent 169.3 m 2 /g, was obtained at the following absorbent preparation variables using water hydration; hydration period of 24 hours, ratio of CaO to fly ash of 1:2, CaSO4 amount of 3 g and drying temperature of 200°C.

Electrodes has been prepared for application in an electric double layer capacitor (EDLC) based on polyethylene glycol lignin (PEGL) and soda lignin (SL) derived from cedar wood. Fibers with a diameter of 23 μm were prepared by direct melt electrospinning of PEGL. Much finer fibers of 3.6 μm diameter were obtained by dry electrospinning of 70% PEGL in a dimethyl formamide (DMF) solution at 145°C. The dry electrospinning of SL alone in an alkaline aqueous solution was not achievable, but this was possible of a mixture of SL and polyethylene glycol (Mw=500 000) at a ratio of 99/1, which resulted in thin SL fibers with a diameter of 0.85 μm. These fibers were converted into activated carbon fibers (ACFs) by thermostabilization, carbonization, and steam activation. The specific Brunauer, Emmett and Teller (BET) surface areas of the resulting PEGL-ACFs and SL-ACFs were 1880 m2 g-1 and 1411 m2 g-1, respectively. PEGL-ACFs electrodes with an organic electrolyte exhibited an impedance of 1.6 Ω and a specific capacitance of 92.6 F g-1 at a scan rate of 1 A g-1, and the SL-ACFs electrodes had an impedance and specific capacitance of 4.5 Ω and 55.6 F g-1, respectively.

This work represents the influence of various sol–gel parameters on the physico‐chemical properties of sulfuric acid chelated zirconia aerogels dried at ambient pressure. The sol–gel parameters such as concentrations of precursor, chelating agent and catalyst are found to be the dominant factors which influence the physical, chemical and textural properties of the aerogels. Therefore, the influence of concentration of Zr precursor, ZrPr:H2SO4 molar ratio and ZrPr:H2O molar ratio on these properties of zirconia aerogels is studied. Zirconia lacogels are formed by the hydrolysis and condensation of zirconium n‐propoxide in n‐propanol chelated with sulfuric acid (18.4 M) and catalyzed with deionized water. Aerogels are obtained by subsequent solvent exchange, silylation, washing and ambient pressure drying. The physico‐chemical properties of as synthesized zirconia aerogels are carried out using FESEM, EDS, BET analysis and FTIR spectroscopy. The good quality zirconia aerogels are obtained using the molar ratio of ZrPr:PrOH:H2SO4:H2O:HMDZ::1:2.93:1.18:1.77:0.59. They possess the density of 0.54 g cm‐3, BET surface area of 328 m2 g‐1 and micropore volume of 0.028 cm3 g‐1. These aerogels can be applied as heterogeneous catalysts in many fields.

Polyhedron structured sphere-like lithium manganese oxide (LiMninf2/infOinf4/inf) is successfully synthesized from β-MnOinf2/inf nanorod precursor via a solid state reaction at a temperature of 800 °C. For comparison, LiMninf2/infOinf4/inf materials with nanorod and octahedron structures are also obtained from β-MnOinf2/inf nanorod precursor at temperatures of 700 °C and 900 °C, respectively. The galvanostatic charge-discharge result shows that the polyhedron sphere-like LiMninf2/infOinf4/inf sample exhibits the best electrochemical performance at high rate and high temperature. After 100 cycles at 5 C, this electrode is able to maintain 94% of its capacity at 25 °C and 81% at 55 °C. This is attributed to that the polyhedron sphere-like spinel LiMninf2/infOinf4/inf can suppress the dissolution of manganese ions. Based on Brunauer Emmett Teller (BET), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), the polyhedron sphere-like LiMninf2/infOinf4/inf sample has the lowest BET surface area, largest diffusion coefficient of Lisup+/sup and least charge transfer resistance. This study provides an insight into the capacity fading of LiMninf2/infOinf4/inf electrodes and the polyhedron structured sphere-like LiMninf2/infOinf4/inf can be a promising material for lithium ion batteries.

Adsorption is a surface process. By evolution, nature has created design principles such as scaffolds that allow to carrying surface bound agents at high density. We used a nanofibrous pullulan/poly(vinyl alcohol)/poly(acrylic acid) (Pul/PVA/PAA) support to carry surface active PAMAM dendrimer similar to spores attached to mushroom gills. A monolayer of ceria (CeO2) nanoparticles served as the linker between PAMAM and the nanofiber. The nanocomposite was a highly effective Cr(VI) adsorbent and the maximum adsorption capacity qmax = 847 mg g−1 is the highest reported value for the same kind of materials so far. The materials was characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FTIR), zeta potential and multipoint BET method to measure the specific surface area. Removal of Cr(VI) from aqueous media was tested under different batch and fixed bed column operation conditions such as pH, temperature and competing ions. Thermodynamic properties were determined based on a modified Langmuir adsorption isotherm and the adsorption kinetic was investigated. Positive entropy of adsorption and an endothermic adsorption process was found, while the rate-limiting step was pseudo second order which is associated with a chemisorption process. The nanocomposite was reusable and up to 95% of the adsorbed Cr(IV) ions were recovered by alkyne washing.

Waste clay recovered from palm oil mill effluent (POME) was characterized and used as an enzyme-supporting material for the cassava saccharification process. The clay was treated by the Soxhlet extraction method to remove the residual oil and then characterized using a BET surface area analyser, XRF, XRD, FTIR, TGA, and FESEM. The chemical analysis showed that the sample had a high amount of CaO (93%) with a minor content of SiO2 (1.378%) and Al2O3 (0.707%), with a surface area of 1.15 m2/g. The XRD analysis revealed the major mineral presence to be calcite, as confirmed by FESEM analysis. The FTIR results also attested to the presence of a calcite phase and carbonate groups. To study the performance of the waste clay for enzyme immobilization application, the recovered waste clay was further used as an enzyme supporting material for enzyme immobilization in the cassava saccharification process. Results showed that the enzymes were successfully encapsulated and gave the highest immobilization yield of 70% with 2% clay concentration. In addition, the encapsulated enzymes also enhanced the reusability, where the enzyme retained 32% of its activity after seven cycles of saccharification processing.

To obtain a better understanding of the deactivation of SCR catalysts that may be encountered due to the presence of P-containing impurities in diesel exhausts, the effects induced by P over Cu/BEA NH3-SCR catalysts were studied as functions of the temperature of poisoning and P concentration in the feed. Cu/BEA catalysts with different Cu loadings (4 and 1.3wt% Cu) were exposed to P by controlled evaporation of H3PO4 in the presence of 8% O2 and 5% H2O at 573 and 773K. The reaction studies were performed by NH3-storage/TPD, NH3/NO oxidation and standard NH3-SCR. In addition, a combination of several characterisation techniques (ICP-AES, BET surface area, pore size distribution, H2-TPR and XPS) was applied to provide useful information regarding the mechanism of P deactivation. Pore condensation of H3PO4 in combination with pore blocking was observed. However, the measured overall deactivation was found to occur mostly by chemical deactivation reducing the number of the active Cu species and hence deteriorating the redox properties of the Cu/BEA catalysts. The process of P accumulation on the surface preferentially occurs on the "over exchanged" Cu active sites with the formation of phosphate species. This is likely the reason for the more severe deactivation of the 4% Cu/BEA compared to 1.3% Cu/BEA. Further, the higher NOx reduction performance at 773K of the P-poisoned Cu/BEA catalysts was found to originate from the lower selectivity towards NH3 oxidation, which occurs predominately on the "over-exchanged" sites. © 2013 Elsevier B.V.

The inimical effects associated with heavy metals are serious concerns, particularly with respect to global health-related issues, because of their non-ecological characteristics and high toxicity. Current research in this area is focused on the synthesis of poly(acrylamide) grafted Cell@Fe3O4 nanocomposites via oxidative free radical copolymerization of the acrylamide monomer and its application for the removal of Pb(II). The hybrid material was analyzed using different analytical techniques, including thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer&ndash, Emmett&ndash, Teller (BET) analysis. The efficacious impact of variable parameters, including contact time, pH, material dose, initial Pb(II) concentration, and the temperature, was investigated and optimized using both batch and artificial neural networks (ANN). Surface digestion of metal ions is exceedingly pH-dependent, and higher adsorption efficiencies and adsorption capacities of Pb(II) were acquired at a pH value of 5. The acquired equilibrium data were analyzed using different isotherm models, including Langmuir, Freundlich, Temkin, and Redlich&ndash, Peterson models. In this investigation, the best performance was obtained using the Langmuir model. The maximum adsorption capacity of the material investigated via monolayer formation was determined to be 314.47 mg g&minus, 1 at 323 K, 239.74 mg g&minus, 1 at 313 K, and 100.79 mg g&minus, 1 at 303 K.

Biochars were prepared by conducting slow pyrolysis of rubber wood sawdust (RWSD) derived from sawn timber. Eventhough researches on preparation of biochar from biomass have been reported by many researchers, limited work has been reported for investigation of biochar RWSD for its surface porosities and functional groups. Surface porosity of biochars provides a suitable dimension for cluster of microorganism to grow and higher porosity for better water holding capacity. Surface functional groups contain oxygen may help to improve the soil fertility by increasing the cation and anion exchange capacities to reduce the nutrient leaching in soil. The pyrolysis process was carried out at temperatures ranging between 300°C to 700°C at the heating rate of 5°C/min for 3hours with continuous nitrogen purging. The influence of pyrolysis temperatures on the biochars pores were investigated by using X-Ray Diffraction (XRD), Brunauer-Emmett-Teller (BET) surface analysis and Scanning Electron Microscopy (SEM). The surface functional groups were examined by Fourier Transform Infrared (FT-IR). SEM analysis clearly showed the development of well-defined pores distributed on biochars surface. It was found that the maximum BET surface area and total pore volume were 5.493 m2/g and 0.0097cm3/g respectively for biochar pyrolysis at 700°C. The FT-IR spectrum analysis showed the functional groups decreased with the increasing of pyrolysis temperature. The results highlighted the effect of pyrolysis temperature on biochar pores accumulative that associated with soil fertility and nutrient retention in soil which could be beneficial to the agricultural industries.

ZrOCl 28H 2O supported on montmorillonite K10 (ZrOCl 2/mont K10) catalyzed Biginelli reaction under solvent-free conditions is reported. The catalysts were characterized by XRD, FTIR, BET surface area analysis, and thermogravimetric analysis. The activity of montmorillonite K10, montmorillonite KSF, ZrOCl 28H 2O, SO 4 2-/ZrO 2, and ZrOCl2/mont K10s was investigated by Biginelli reaction of benzaldehyde, ethylacetoacetate and urea. The reactions were carried out by addition of ZrOCl 2/mont K10 to a mixture of aldehyde, ethylacetoacetate and urea/thiourea with thorough stirring in the absence of solvent under conventional heating or microwave irradiation to prepare 3,4- dihydropyrimidin-2(1H)-one/thione derivatives at 80 �C in good yields. � Springer Science+Business Media, LLC 2011.

Regeneration of the activity of three-way catalytic converters (TWCs) was tested for the first time using a biodegradable metal chelating agent (S, S-ethylenediamine disuccinic acid (S, S-EDDS). The efficiency of this novel environmentally friendly solvent in removing various contaminants such as P, Zn, Pb, Cu and S from commercial aged three-way catalysts, and improving their catalytic performance towards CO and NO pollutants removal has been investigated. Four samples of catalysts from the front and rear inlets of two different TWCs with different mileages and aged under completely different driving conditions were investigated. The catalysts were characterized using various techniques, such as X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area measurements (N2 adsorption at 77K). Quantitative ICP-MS analyses and SEM-EDS studies show the removal of Zn, P and Pb. SEM-EDS images obtained at low magnification (50μm) showed considerable differences in the surface morphology and composition after washing with S, S-EDDS. However, XRD studies indicated neither little to no removal of major contaminant compound phases nor major structural changes due to washing. Correspondingly, little or no enhancement in BET surface area was observed between the used and washed samples. Light-off curves show that the regeneration procedure employed can effectively improve the catalytic performance towards NO pollutant. © 2010 Elsevier B.V. 186 2-3 999 1006 Cited By :25

In an attempt to control the surface dispersion and the mobility of BaO domains on NOx storage materials, TiO2/TiOx anchoring sites were introduced on/inside the conventional γ-Al 2O3 support matrix. BaO/TiO2/Al 2O3 ternary oxide materials were synthesized via two different sol-gel preparation techniques, with varying surface compositions and morphologies. The synthesized NOx storage materials were studied via XRD, Raman spectroscopy, BET surface area analysis, TPD, XPS, SEM, EDX-mapping, and in situ FTIR spectroscopy of adsorbed NO2. NOx uptake properties of the BaO/TiO2/Al2O3 materials were found to be strongly influenced by the morphology and the surface structure of the TiO2/TiOx domains. An improved Ba surface dispersion was observed for the BaO/TiO2/Al2O3 materials synthesized via the coprecipitation of alkoxide precursors, which was found to originate mostly from the increased fraction of accessible TiO 2/TiOx sites on the surface. These TiO2/ TiOx sites function as strong anchoring sites for surface BaO domains and can be tailored to enhance surface dispersion of BaO. TPD experiments suggested the presence of at least two different types of NOx species adsorbed on the TiO2/TiOx sites, with distinctively different thermal stabilities. The relative stability of the NOx species adsorbed on the BaO/TiO2/Al2O3 system was found to increase in the following order: NO+/N2O 3 on alumina ≪ nitrates on alumina < surface nitrates on BaO < bridged/bidentate nitrates on large/isolated TiO2 clusters < bulk nitrates on BaO on alumina surface and bridged/bidentate nitrates on TiO2 crystallites homogenously distributed on the surface < bulk nitrates on the BaO sites located on the TiO2 domains. © 2010 American Chemical Society.

The sorption of molecules of different size and polarity (water, n-hexane isooctane, benzene, toluene, cyclohexane, carbon tetrachloride, isopropanol isobutanol, methanol, ethanol) by sepiolite from Goles, i.e. from the biggest to-date known Yugoslav deposit, was studied in this work. The BET surface area observed with different sorbates varied from 227 to 314m2/g due to only partial migration of sorbate molecules into the pores or to imperfect packing of the sorbate molecules. The value of the outer surface area suggested that the average thickness of the fibers of Goles sepiolite was approximately 15 nm.

RF hydrogels were synthesized by the sol-gel polycondensation of resorcinol with formaldehyde and RF cryogels were prepared by freeze drying of the hydrogels with t-butanol. The cryogels were characterized by nitrogen adsorption, density measurements, and scanning electron microscope. Their porous properties were compared with those of the aerogels prepared by supercritical drying with carbon dioxide. RF cryogels were mesoporous materials with large mesopore volumes >5.8× 10−4m3/kg. Although surface areas and mesopore volumes of the cryogels were smaller than those of the aerogels, the cryogels were useful precursors of mesoporous carbons. Aerogel-like carbons (carbon cryogels) were obtained by pyrolyzing RF cryogels in an inert atmosphere. The carbon cryogels were mesoporous materials with high surface areas >8.0× 105m2/kg and large mesopore volumes >5.5× 10−4m3/kg. When pyrolyzed, micropores were formed inside the cryogels more easily than inside the aerogels.

Zinc ferrite belongs to the class of normal spinels where it is assumed to have a cation distribution of Zn2+(Fe3+)2(O2-)4, and it is purported to be showing zero net magnetisation. However, there have been recent reports suggesting that zinc ferrite exhibits anomaly in its magnetisation. Zinc ferrite samples have been prepared by two different routes and have been analysed using low energy ion scattering, Mössbauer spectroscopy and magnetic measurements. The results indicate that zinc occupies octahedral sites, contrary to the earlier belief that zinc occupies only the tetrahedral sites in a normal spinel. The amount of zinc on the B site increases with decrease in particle size. The LEIS results together with the Mössbauer results and the magnetic measurements lead to the conclusion that zinc occupies the B site and the magnetisation exhibited by ultrafine particles of zinc is due to short range ordering.

WOS: 000301320500021, PubMed ID: 22197058, Mesoporous silica SBA-15 has been synthesized and functionalized by one-step synthesis method to widen their various application possibilities. In this study, phenyltrimethoxysilane (PTMS), 3-mercapto-propyltrimethoxysilane (MPTMS) and trimethoxypropylsilane (TMPS) were used as silane precursors for the functionalization, and after treated with HCl solution, their catalytic activities were evaluated in the lactic acid-methanol esterification. The presence of anchoring of functional groups on SBA-15 was proved by XRD, FT-IR, BET surface area and pore size distributions. Good catalytic activity was observed especially for SBA-15-SO3H-MPTMS, and the catalytic activity order was determined as follows: SBA-15SO(3)H-MPTMS > SBA-15-TMPS > SBA-15-PTMS, which is directly associated with the surface area, pore size and pore volume. As compared with homogeneous catalyst, SBA-15-SO3H-MPTMS heterogeneous catalyst shows remarkable performance, such as separation, recovery and reusability

A facile and novel strategy for preparing mesoporous crystalline copper-polyaniline composite is reported wherein the reaction is carried out at room temperature using copper nitrate as the oxidizing agent and methanol as the solvent. The composite obtained as a precipitate has been characterized using UV-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption method, Barrett-Joyner-Halenda (BJH) method, Brunauer-Emmett-Teller method (BET) and thermogravimetric analysis (TGA). The XRD studies in conjunction with the BJH method reveals that the composite has crystalline nature with a mesoporous structure and has a diameter of 3.5 nm. The specific surface area of copper-polyaniline composite is estimated to be as high as 63.2 m 2 g -1 using the BET surface area plot. The characterization of the filtrate indicates the presence of pernigraniline with a very small weight percent of copper. � 2011 Elsevier Ltd. All rights reserved.

We tried to improve the H2-sorption properties of Mg by mechanical grinding under H2 (reactive mechanical grinding) with Fe2O3 under various milling conditions. The sample Mg–10 wt.%Fe2O3 prepared by milling at a revolution speed of 250 rpm for 24 h has the best hydrogen-storage properties. It absorbs 5.05 wt.% hydrogen at 593 K under 12 bar H2 for 60 min at the first cycle. Its activation is accomplished after three hydriding–dehydriding cycles. The activated sample absorbs 4.22 wt.% hydrogen at 593 K, 12 bar H2 for 10 min. The reactive grinding of Mg with Fe2O3 increases the H2-sorption rates by facilitating nucleation (by creating defects on the surface of the Mg particles and by the additive), by making cracks on the surface of Mg particles and reducing the particle size of Mg and thus by shortening the diffusion distances of hydrogen atoms. Hydriding–dehydriding cycling also increases the H2-sorption rates by creating defects on the surface of the Mg particles, and by making cracks on the surface of Mg particles and reducing the particle size of Mg.

Resorcinol-formaldehyde (RF) cryogels were synthesized by sol-gel polycondensation of resorcinol with formaldehyde and freeze-drying carried out with t-butanol. Carbon cryogels were obtained by pyrolyzing RF cryogels in an inert atmosphere. Characterization by nitrogen adsorption showed that carbon cryogels were micro- and mesoporous materials with high surface areas (500 m(2)/g LT S-BET LT 700 m(2)/g). Cyclic voltammetry experiments at various scan rates (2 to 200 mV s(-1)) were carried out to study the electrical double-layer charging of carbon cryogel electrodes in 0.5 mol dm(-3) HClO4 solution. It has been demonstrated that the total specific capacitance can further be divided into mesoporous and microporous specific capacitance by analyzing the linear dependence of the specific capacitance (C) on the reciprocal of the square root of the potential scan rate (nu(-1/2)), as well as linear dependence of the reciprocal specific charge (1/C) on the square root of the potential scan rate (nu(1/2)). Current Research in Advanced Materials and Processes, 6th Conference of the Yugoslav-Materials-Research-Society, Sep 13-17, 2004, Herceg Novi, Montenegro

International audience; The theoretical external specific surface area of single- and multi-walled carbon nanotubes and of carbon nanotube bundles is calculated as a function of their characteristics (diameter, number of walls, number of nanotubes in a bundle). The results are reported in diagrams and tables useful to correlate the microscopic characteristics and the specific surface area of samples. The calculated values are in good agreement with the microscopic characteristics and the specific surface area measurements which have been previously reported in the literature. The specific surface area is a macroscopic parameter which can be helpful to adjust the synthesis conditions of carbon nanotubes.

The influence of the temperature and reaction time on the sulfation process of a dolomite is investigated in this paper. The sulfation effectiveness was evaluated and correlated with changes in the physical characteristics of a Brazilian dolomite during the reactive process. Calcination and sulfation experiments were performed under isothermal conditions for dolomite samples with average particle sizes of 545 ?m at temperatures of 750 °C, 850 °C and 950 °C at different times of sulfation. Thermogravimetric tests were applied to establish the reactivity variation of the dolomite in function of the time in the sulfation reaction and evaluate the methodology of the samples preparation. Porosimetry tests were performed to study the pore blockage of dolomite during the sulfation reaction. The highest values of BET surface area were 25.55 m2/g, 29.55 m2/g and 12.62 m2/g for calcined samples and after their sulfation processes, conversions of 51.5%, 61.9% and 42.8% were obtained at 750 °C, 850 °C and 950 °C, respectively. Considering the process as a whole, the best fit was provided by a first-order exponential decay equation. Moreover, the results have shown that it is possible to quantify the decreasing in the dolomite reactivity for sulfur dioxide sorption and understand the changes in the behavior of the sulfation process of limestones when applied to technologies, as fluidized bed combustor, in which sulfur dioxide is present