In: Adsorption Science and Technology, 2001, vol. 19, no. 8, p. 645-653
Asturian apple pulp was carbonised under nitrogen at 400ºC and 750ºC and subsequently activated with CO2 at 750ºC. The resulting active carbon exhibited properties in line with those expected from precursors of vegetable origin, with the carbonisation stage appearing to have only a limited influence on the final porosity. In the case of carbonisation at 400ºC, the initial micropore...
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In: Carbon, 1994, vol. 32, no. 8, p. 1463-1467
An Asturian anthracite has been subjected to different pretreatments and subsequently activated by steam at 850°C to a total burn-off of 55 percent. The physical properties (micropore sizes and distributions, external surface areas, etc.) of the solids are compared with those of the carbon obtained by direct activation. Although the yield is generally low, it appears that better results are...
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In: Carbon, 1996, vol. 33, no. 5, p. 581-586
It is shown that the oxidation of an Asturian bituminous coal by air, at 150 ° and 270 °C, has a considerable influence on the microporous structure of the carbon obtained by subsequent carbonization and steam activation to 50% burn-off. The direct activation of the coal leads to an open micropore system of 0.2 cm3/g, with an average pore size near 0.8 nm. On the other hand, much larger systems...
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In: Carbon, 1996, vol. 34, no. 10, p. 1201-1206
Activated carbons were prepared from two polyarylamide fibres (Kevlar and Nomex) by carbonization and subsequent steam activation to 25 and 50% burn-off. The porous structure of the carbons has been investigated by physical adsorption of CH2Cl2 and N2O at 293 K and immersion calorimetry into liquids of different molecular dimensions. The activated fibres have...
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In: Carbon, 1997, vol. 35, no. 8, p. 1097-1100
Immersion calorimetry is a useful tool for the characterization of solid surfaces in general, but in the case of microporous solids it usually requires complementary information, obtained from an adsorption isotherm. This article demonstrates the possibilities and the limitations of this technique when used alone. It appears that the use of a standard value for the enthalpy immersion does not...
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In: Electrochimica Acta, 2008, vol. 53, no. 5, p. 2210-2216
The present paper shows that the performance of an inexpensive activated carbon used in electrochemical capacitors can be significantly enhanced by a simple treatment with KOH at 850 °C. The changes in the specific surface area, as well as in the surface chemistry, lead to high capacitance values, which provide a noticeable energy density. The KOH-treatment of a commercial activated carbon...
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In: Electrochimica Acta, 2008, vol. 53, no. 24, p. 7111-7116
This study shows that carbide-derived carbons (CDCs) with average pore size distributions around 0.9–1 nm and effective surface areas of 1300–1400 m2 g−1 provide electrochemical double-layer capacitors with high performances in both aqueous (2M H2SO4) and aprotic (1M (C2H5)4NBF4 in acetonitrile)...
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In: Materials Chemistry and Physics, 2009, vol. 114, no. 1, p. 223-227
It is shown that cherry stones-wastes can be recycled as activated carbons for electrode material in supercapacitors. KOH-activation of this precursor at 800–900 °C is an efficient process to obtain carbons with large specific surface areas (1100–1300 m2 g−1), average pore sizes around 0.9–1.3 nm, which makes them accessible to electrolyte ions, and conductivities...
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In: Carbon, 2008, vol. 46, no. 7, p. 1025-1030
Based on more than 80 carbons, the paper shows that immersion calorimetry into benzene, water and carbon tetrachloride can be used to assess with a good accuracy the limiting capacitance Co at low current densities in both acidic (2 M H2SO4) and aprotic (1M tetraethyl ammonium tetrafluoroborate in acetonitrile) electrolytic solutions. The enthalpies of immersion...
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In: Recent Advances in Adsorption Processes for Environmental Protection and Security, 2008, vol. 18, no. 2, p. 9-18
This study shows that immersion calorimetry is a useful technique which simplifies considerably the analysis of porosity and chemical nature of activated carbons. The characterization of activated carbons in the general theoretical framework of Dubinin's theory with its extensions to calorimetry and adsorption from solutions allows the identification of some key parameters for the performance of...
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