Abstract Carbon xerogels were prepared by soft templating of tannin-formaldehyde resin as the precursor and F-127 Pluronic® used as both surfactant and templating agent. The influence of preparation pH and amount of Pluronic was systematically investigated, and the resultant porous structures were analysed by mercury porosimetry, helium and envelope pycnometry, and nitrogen adsorption. We show how highly controlled structures can be obtained, presenting bimodal character – either macro-microporous or meso-microporous – and mostly having very narrow pore-size distributions. The corresponding carbon gels have disordered but quite well calibrated and available porosity, with pore volumes and surface areas typical of far more expensive carbon aerogels. They might be used in any application requiring an excellent availability of microporosity and/or mesoporosity.
Last. Alain Celzard(University of Lorraine)H-Index: 64
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The tortuosity of cellular vitreous carbon (CVC) foams having different bulk densities and different pore sizes has been investigated by a diffusion technique. The corresponding values were compared to tortuosities determined by two other different methods: acoustic on one hand, and tomographic on the other hand. Whereas acoustic tortuosities were slightly higher than diffusional ones but followed the same linear increase with CVC density, geometrical ones were much lower and presented the oppos...
Last. Nathalie Job(University of Liège)H-Index: 28
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Abstract Ordered mesoporous carbons (OMC) were synthesized via a direct templating pathway by a synthesis route that features short duration, moderate temperature and aqueous media. Resorcinol was used as carbon precursor and hexamethylenetetramine as a source of formaldehyde and ammonia to respectively cross-link the framework and regulate the pH. The temperature of the heat treatment leading to the formation of the solid polymer was shown to have a strong influence on the structural and textur...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract Tannin-based, carbonised, polymerised High Internal Phase Emulsions (polyHIPEs) are described in detail for the first time. Such highly porous materials were prepared by emulsion-templating, using an aqueous phase made of tannin and a low amount of hexamine dissolved in water, sunflower oil, and ethoxylated castor oil. After hardening of the tannin-based resin, the oil was leached out and the resultant monoliths were pyrolysed. The porous structure of carbon polyHIPEs prepared with an i...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract Aqueous solutions of condensed tannins were submitted to hydrothermal carbonization (HTC) in a stainless steel autoclave, and the kinetics of hydrothermal carbon formation was investigated by changing several parameters: amount of tannin (0.5; 1.0; 1.5; 2.0 g in 16 mL of water), HTC temperature (130, 160, 180 and 200 °C) and reaction times (from 1 to 720 h). The morphology and the structure of the tannin-based hydrothermal carbons were studied by TEM, krypton adsorption at −196 °C and h...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract New macro-cellular carbons, called carbon meringues, have been prepared by whipping until stiff an aqueous solution of tannin until liquid foam was obtained, which was next stabilized in an oven and pyrolysed, hence their name. With such cheap, fast and very easy process, flawless, homogeneous carbon foams were obtained in a wider range of density than that of more conventional cellular vitreous carbon (CVC) foams derived from similar formulations but made by physical foaming. The poros...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract Highly porous organic materials have been obtained from the gelation of a tannin-based resin at different pHs in the presence of F-127 Pluronic ® surfactant. After subcritical drying in ambient conditions, and without the need of any solvent exchange step, the resultant xerogels had bulk densities typical of most organic aerogels. Their porous structures revealed unique features, depending on the initial pH, such as the possibility of getting either purely macroporous materials with nar...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract Aqueous solutions containing tannin, crosslinker and surfactant were used for transferring techniques used to produce foods such as mayonnaise, whipped cream and meringue, to the preparation of new kinds of cellular carbons. Emulsion-templating, i.e. leaching a hardened “mayonnaise” for removing the oil followed by pyrolysis led to carbon polyHIPEs (polymerised High Internal Phase Emulsions). The second kind of materials, obtained by whipping the emulsions, presented hierarchical porous...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract The present work deals with acoustic properties of highly porous rigid foams derived from flavonoid tannins. Such cellular solids derived from renewable resources were investigated before and after pyrolysis, the latter leading to cellular, vitreous, carbon foams. It is demonstrated here that these lightweight materials have a high air flow resistivity, which depends on the density of the foam. Vitreous carbon foams, especially, have rather low performances for sound absorption. Using a...
In this review, we discuss the phenomenon of complementary macropore incorporation into mesoporous and/or microporous solids in order to enhance their catalytic performance in fuels and chemicals synthesis.
#2Vanessa Fierro(CNRS: Centre national de la recherche scientifique)H-Index: 60
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract This manuscript presents a simple one-pot synthesis for producing nitrogen-doped carbon materials (NCMs) with nitrogen content up to 6.3 wt.%. Carbon gels were produced by direct pyrolysis without the expensive step of supercritical drying in CO2. NCMs were synthesized by hydrothermal carbonization (HTC) of aminated tannin. Amination of tannin was carried out in aqueous ammonia solution according to two different methods: (1) amination at room temperature followed by evaporation and HTC...
The electromagnetic properties of Carbon-Graphene Xerogel (CGX), Flaky graphite (GR) and Nickel-Zinc ferrite (FeNiZn) composites in polystyrene (PS) matrix were studied in the X-Band range (8.2 – 12.4 GHz). In this work the Expanded Polystyrene (EPS) waste material was processed into polystyrene through the recycling of EPS. The polystyrene obtained was utilized as dielectric matrix, mainly because PS is a wellknown organic polymer that presents low dielectric loss and light weight, which contri...
This contribution reports the use of an organic gel, xerogel, as catalyst support for Cu. The xerogel was synthesized from the system tannin-formaldehyde at pH 3, using F-127 Pluronic as surfactant. The surface area values were higher than 900 m2/g even after the Cu (10%, wt) impregnation. The morphological analysis by SEM-FEG revealed the presence of spheres arranged in a tridimensional structure. XRD diffractograms showed the presence of CuO and Cu2O crystalline phases combined with the amorph...
Last. Hani E. Naguib(U of T: University of Toronto)H-Index: 35
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Abstract Due to their high porosity and nanoporous morphology, aerogels have presented unique properties and thus offered a very high potential capability to be used in leading applications such as super thermal insulation and nanoparticle filtering. However, controlling the aerogels’ morphology and as a result, tailoring their properties is still a challenge. In this study, polyimide aerogels are developed through imidization of highly reactive pyromellitic dianhydride (PMDA) and p-phenylene di...
Abstract Tannins are polyphenolic molecules of great industrial interest, not only for themselves but also as bio-based precursors for multiple carbonaceous materials with extremely diverse structures, textures and potential applications. In recent years, extensive work has been devoted to these new, predominantly porous carbons, and to their properties. It was therefore time to collect the main results in this invited review, whose objective is to show how a single, inexpensive, non-toxic and c...
With the extensive use of nitrogen-based fertilizer in agriculture, ammonia emissions, especially from cattle manure, are a serious environmental threat for soil and air. The European community committed to reduce the ammonia emissions by 30% by the year 2030 compared to 2005. After a moderate initial reduction, the last report showed no further improvements in the last four years, keeping the 30% reduction a very challenging target for the next decade. In this study, the mitigation effect of di...
Last. Antonio Pizzi(University of Lorraine)H-Index: 79
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Tannins are one of the most natural, non-toxic, and highly reactive aromatic biomolecules classified as polyphenols. The reactive phenolic compounds present in their chemical structure can be an alternative precursor for the preparation of several polymeric materials for applications in distinct industries: adhesives and coatings, leather tanning, wood protection, wine manufacture, animal feed industries, and recently also in the production of new porous materials (i.e., foams and gels). Among t...
#1Ana Arenillas(CSIC: Spanish National Research Council)H-Index: 57
#2J. Angel Menéndez(CSIC: Spanish National Research Council)H-Index: 19
Last. Nathalie Job(University of Liège)H-Index: 28
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This chapter presents the most recent updates about sol-gel chemistry of phenolic molecules and the corresponding materials: xerogels, cryogels, and aerogels. The structure and properties of the latter, whether in the organic or carbon forms, are detailed and actual and potential applications are reported.
Last. Alain Celzard(University of Lorraine)H-Index: 64
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Abstract The first carbon aerogels prepared by autocondensation of condensed (flavonoid) tannin, a cheap renewable resource extracted from Mimosa barks, are presented. Mixing aqueous solutions of tannin and sodium silicate indeed produced the very fast gelation of tannins, thus leading to organic hydrogels which were first converted into organic aerogels by supercritical drying, and then into carbon aerogels after pyrolysis at 900 °C. Subsequent dissolution of the silica nanoparticles thus forme...
Last. Alain Celzard(University of Lorraine)H-Index: 64
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The first tannin-based carbon xerogel microspheres were prepared and characterised. The materials were synthesised by inverse emulsion polymerisation in sunflower oil, based on the same formulation but using two main independent variables: stirring speed and surfactant amount. The resultant sol–gel spheres were then washed, dried in air, and pyrolysed. The effect of stirring speed and surfactant amount on carbon microsphere size distribution and porous texture was investigated in detail. Dependi...
Last. Ana Arenillas(CSIC: Spanish National Research Council)H-Index: 57
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Abstract Usually, carbon xerogels are obtained from resorcinol–formaldehyde organic gels. However, more cost-effective and eco-friendly carbon xerogels can be synthesised by using tannins instead of resorcinol, provided that a suitable surfactant is added to prevent the collapse of the structure. The use of tannin, a natural phenolic compound derived from wood, allows obtaining carbon xerogels with controlled porosity, as the porous properties of these materials can be tailored by an appropriate...
