The Experts below are selected from a list of 19152 Experts worldwide ranked by ideXlab platform
Jean-marie Tarascon - One of the best experts on this subject based on the ideXlab platform.
-
Erratum: Preparation of nanotextured VO2[B] from vanadium oxide aerogels (Chemistry of Materials (2006) 18 (4369-4374))
Chemistry of Materials, 2007Co-Authors: Emmanuel Baudrin, Guillaume Sudant, Bruce S. Dunn, Dominique Larcher, Jean-marie TarasconAbstract:Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0. Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0.
-
Preparation of nanotextured VO 2[B] from vanadium oxide aerogels
Chemistry of Materials, 2006Co-Authors: Emmanuel Baudrin, Guillaume Sudant, Bruce S. Dunn, Dominique Larcher, Jean-marie TarasconAbstract:Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0. Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0.
Maureen E Callow - One of the best experts on this subject based on the ideXlab platform.
-
the control of marine biofouling on Xerogel surfaces with nanometer scale topography
Biofouling, 2011Co-Authors: Nikhil Gunari, John A Finlay, Stephanie M Bennett, Lenora H Brewer, Anastasiya Sokolova, Anne E Meyer, Gilbert C Walker, Dean E Wendt, Nadine D Kraut, Maureen E CallowAbstract:Mixtures of n-octadecyltrimethoxysilane (C18, 1–5 mole-%), n-octyltriethoxysilane (C8) and tetraethoxysilane (TEOS) gave Xerogel surfaces of varying topography. The 1:49:50 C18/C8/TEOS Xerogel formed 100–400-nm-wide, 2–7-nm deep pores by AFM while coatings with ≥3% C18 were free of such features. Segregation of the coating into alkane-rich and alkane-deficient regions in the 1:49:50 C18/C8/TEOS Xerogel was observed by IR microscopy. Immersion in ASW for 48 h gave no statistical difference in surface energy for the 1:49:50 C18/C8/TEOS Xerogel and a significant increase for the 50:50 C8/TEOS Xerogel. Settlement of barnacle cyprids and removal of juvenile barnacles, settlement of zoospores of the alga Ulva linza, and strength of attachment of 7-day sporelings were compared amongst the Xerogel formulations. Settlement of barnacle cyprids was significantly lower in comparison to glass and polystyrene standards. The 1:49:50 and 3:47:50 C18/C8/TEOS Xerogels were comparable to PDMSE with respect to removal of juv...
-
barnacle settlement and the adhesion of protein and diatom microfouling to Xerogel films with varying surface energy and water wettability
Biofouling, 2010Co-Authors: John A Finlay, Stephanie M Bennett, Lenora H Brewer, Anastasiya Sokolova, Gemma Clay, Nikhil Gunari, Anne E Meyer, Gilbert C Walker, Dean E Wendt, Maureen E CallowAbstract:Previous work has shown that organosilica-based Xerogels have the potential to control biofouling. In this study, modifications of chemistry were investigated with respect to their resistance to marine slimes and to settlement of barnacle cyprids. Adhesion force measurements of bovine serum albumin (BSA)-coated atomic force microscopy (AFM) tips to Xerogel surfaces prepared from aminopropylsilyl-, fluorocarbonsilyl-, and hydrocarbonsilyl-containing precursors, indicated that adhesion was significantly less on the Xerogel surfaces in comparison to a poly(dimethylsiloxane) elastomer (PDMSE) standard. The strength of adhesion of BSA on the Xerogels was highest on surfaces with the highest and the lowest critical surface tensions, γC and surface energies, γS, and duplicated the ‘Baier curve’. The attachment to and removal of cells of the diatom Navicula perminuta from a similar series of Xerogel surfaces were examined. Initial attachment of cells was comparable on all of the Xerogel surfaces, but the percenta...
-
the role of surface energy and water wettability in aminoalkyl fluorocarbon hydrocarbon modified Xerogel surfaces in the control of marine biofouling
Biofouling, 2009Co-Authors: Stephanie M Bennett, Frank V Bright, John A Finlay, Nikhil Gunari, Anne E Meyer, Gilbert C Walker, Maureen E Callow, David D Wells, James A Callow, Michael R DettyAbstract:Xerogel films with uniform surface topogrophy, as determined by scanning electron microscopy, atomic force microscopy (AFM), and time-of-flight secondary ion mass spectrometry, were prepared from aminopropylsilyl-, fluorocarbonsilyl-, and hydrocarbonsilyl- containing precursors. Young's modulus was determined from AFM indentation measurements. The Xerogel coatings gave reduced settlement of zoospores of the marine fouling alga Ulva compared to a poly(dimethylsiloxane) elastomer (PDMSE) standard. Increased settlement correlated with decreased water wettability as measured by the static water contact angle, θWs, or with decreased polar contribution (γP) to the surface free energy (γS) as measured by comprehensive contact angle analysis. The strength of attachment of 7-day sporelings (young plants) of Ulva on several of the Xerogels was similar to that on PDMSE although no overall correlation was observed with either θWs or γS. For sporelings attached to the fluorocarbon/hydrocarbon-modified Xerogels, the st...
Jeanpaul Pirard - One of the best experts on this subject based on the ideXlab platform.
-
unpredictable photocatalytic ability of h2 reduced rutile tio2 Xerogel in the degradation of dye pollutants under uv and visible light irradiation
Applied Catalysis B-environmental, 2010Co-Authors: Carlos A Paez, Dirk Poelman, Jeanpaul Pirard, Benoit HeinrichsAbstract:Abstract A series of H2-reduced TiO2 Xerogels of low specific surface area was prepared by the sol–gel process. The gels were dried, calcined in air at various temperatures (400, 500, 700 °C) and then reduced at 400 °C under hydrogen flow (H2-HTR treatment). The materials were characterized by X-ray diffraction, transmission electron microscopy (TEM) and UV/Visible diffuse reflectance spectroscopy, and their texture was determined by nitrogen adsorption–desorption. IR spectroscopy was used to study to what extent samples were reduced. The effects of the calcination/H2-HTR treatments on the adsorption of methylene blue (MB) in aqueous solution and on the photocatalytic degradation of MB and crystal violet (CV) under UV and visible light irradiation were also evaluated. Results showed predictable modifications in the physicochemical properties caused by the annealing of TiO2 Xerogel at high temperature (700 °C), such as a total anatase-to-rutile phase transition and a considerable loss of specific surface area from 260 to 2 m2 g−1. However, the higher degree of reduction exhibited by the rutile-TiO2 lattice led to unpredictable photocatalytic activity for the dye conversion under UV and visible light irradiation. The loss of specific surface area of the rutile-TiO2 sample was compensated by the increase in the affinity of this sample for the dye. Under UV light, the rutile-TiO2 Xerogel obtained at 700 °C showed a similar level of photoactivity as the one obtained with anatase-TiO2 Xerogels obtained by calcination at 400 and 500 °C. On the other hand, under visible light, unlike anatase-TiO2 Xerogels, the rutile-TiO2 Xerogel showed a dye photoconversion rate per external surface area that was up to 40 times higher than the one obtained with commercial Degussa P25 TiO2.
-
Preparation and characterization of Xerogel catalyst microspheres
Journal of Non-crystalline Solids, 2004Co-Authors: Christelle Alié, Fabrice Ferauche, Benoıˆt Heinrichs, René Pirard, Neil Winterton, Jeanpaul PirardAbstract:Abstract For easier handling and use in fixed bed reactors, Pd–Ag/SiO2 aerogel–like Xerogel catalysts were shaped into microspheres using the microencapsulation process developed by Brace GmbH. Before the bead production process, the Xerogel catalyst was ground in water and mixed with ethylene glycol and sodium alginate, the latter of which is the gelation agent. The beads were formed at a vibrating nozzle and solidified during their fall in a water tank containing calcium ions, which induce cross-linking of the alginate and consequent bead hardening. Preliminary work was done using a syringe instead of the material-consuming Brace unit. The beads were made from a suspension of dried only, dried and calcined, or dried, calcined, and reduced catalyst. The textural properties of the beads were analyzed by nitrogen adsorption–desorption isotherms and mercury porosimetry; and bead catalytic activity was tested for selective hydrodechlorination of 1,2-dichloroethane. The beads made from a suspension of dried catalyst appear to have properties the closest to that of the Xerogel reference catalyst. Porosity and surface area are maintained at their level before bead formation. However conversion of 1,2-dichloroethane decreases after the production process, possibly due to poisoning by calcium ions.
-
Synthesis of SiO2 Xerogels and Pd/SiO2 cogelled Xerogel catalysts from silylated acetylacetonate ligand
Journal of Non-crystalline Solids, 2004Co-Authors: Stéphanie Lambert, Benoit Heinrichs, Luigi Sacco, Fabrice Ferauche, Alfred F. Noels, Jeanpaul PirardAbstract:Abstract SiO 2 Xerogels and Pd/SiO 2 cogelled Xerogel catalysts have been prepared in a mixture of tetrahydrofurane (THF) and ethanol containing tetraethoxysilane (TEOS), and an aqueous ammonia solution of 0.18 mol/l, from synthesized new silylated acetylacetonate ligands, respectively, 3-[3-(trimethoxysilyl)propyl]-2,4-pentanedione (MS-acac-H), 2,2,6,6-tetramethyl-4-[3-(trimethoxysilyl)propyl]-3,5-heptanedione (MS-dPvM), and 1,3-diphenyl-2-[3-(trimethoxysilyl)propyl]-1,3-propanedione (MS-dBzM), able to form a chelate with a metal ion such as Pd 2+ . All samples form homogeneous colored gels. The resulting catalysts are composed of palladium crystallites with a diameter of about 3.5 nm, located inside primary silica particles exhibiting a monodisperse microporous distribution as well as large palladium particles from 20 to 50 nm, situated outside the silica aggregates. The silylated organic ligand has a strong influence on the textural properties of Xerogels and catalysts, both before and after calcination and reduction steps. Changing the nature of the silylated ligand permits tailoring textural properties such as pore volume, pore size and surface area. Although small palladium crystallites are located inside the silica particles, their complete accessibility, via the micropore network, has been shown. 1,2-Dichloroethane hydrodechlorination over Pd/SiO 2 catalysts mainly produces ethane and the reaction rate increases linearly with palladium dispersion. Hydrodechlorination over Pd/SiO 2 cogelled Xerogel catalysts is a structure insensitive reaction compared to the ensemble size concept.
-
pd sio2 cogelled aerogel catalysts and impregnated aerogel and Xerogel catalysts synthesis and characterization
Journal of Catalysis, 1997Co-Authors: Benoit Heinrichs, Francis Noville, Jeanpaul PirardAbstract:Pd/SiO 2 aerogel catalysts have been synthesized by cogelation of tetraethoxysilane with complex Pd 2+ [NH 2 -CH 2 -CH 2 -NH-(CH 2 ) 3 -Si(OCH 3 ) 3 ] 2 containing a hydrolysable silyl group. Pd catalysts have also been prepared by impregnation of silica aerogels and Xerogels with solutions of this complex or Pd 2+ (NH 3 ) 4 followed by drying under hypercritical conditions or under vacuum. It appears that, in cogelled samples, the Pd 2+ complex acts as a nucleation agent in the formation of silica particles. The resulting catalysts are then composed of completely accessible palladium crystallites with a diameter of about 2.3 nm located inside silica particles with a monodisperse microporous distribution centered on a hydraulic radius of 0.43 nm. The continuous meso- and macropore distribution is located in voids between particles and between aggregates constituted of those particles. In impregnated samples, it appears that Pd particles are located outside SiO 2 particles. The relation between the texture of cogelled and impregnated catalysts and their behavior toward sintering has been studied in detail. In cogelled samples, it has been shown that Pd crystallites cannot migrate because they are trapped in the pores of SiO 2 particles. These catalysts are sinterproof during hypercritical drying. When Pd crystallites are not trapped inside SiO 2 particles, hypercritical drying leads to an extensive sintering of metal particles. During calcination of impregnated catalysts dried under vacuum, sintering occurs to a various extent depending on the support texture. The Pd crystallites size decreases when the pore size distribution is shifted toward the small sizes.
Emmanuel Baudrin - One of the best experts on this subject based on the ideXlab platform.
-
Erratum: Preparation of nanotextured VO2[B] from vanadium oxide aerogels (Chemistry of Materials (2006) 18 (4369-4374))
Chemistry of Materials, 2007Co-Authors: Emmanuel Baudrin, Guillaume Sudant, Bruce S. Dunn, Dominique Larcher, Jean-marie TarasconAbstract:Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0. Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0.
-
Preparation of nanotextured VO 2[B] from vanadium oxide aerogels
Chemistry of Materials, 2006Co-Authors: Emmanuel Baudrin, Guillaume Sudant, Bruce S. Dunn, Dominique Larcher, Jean-marie TarasconAbstract:Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0. Vanadium oxide aerogels were used as a precursor for preparing nanotextured VO2[B] by low-temperature heat treatment under vacuum. The VO2[B] material retains the fibrous morphology and high surface area of the aerogel. Evolution of the VO2[B] phase, as studied by FTIR and X-ray diffraction, indicates that the local structure of the vanadium oxide aerogel is close to that of VO2[B], in agreement with the bilayer-type structure previously proposed for vanadium oxide aerogels/Xerogels. The electrochemical behavior of VO2[B] also bears similarity to that of vanadium oxide aerogels. Specific capacities for lithium as high as 500 mA·h/g are obtained for nanocrystalline VO2[B], and stable electrochemical response is obtained when cycled between 4 and 2.4 V vs Li+/Li0.
Lichun Li - One of the best experts on this subject based on the ideXlab platform.
-
flexible nanofiber reinforced aerogel Xerogel synthesis manufacture and characterization
ACS Applied Materials & Interfaces, 2009Co-Authors: Lichun Li, Baris Yalcin, Baochau N Nguyen, Mary Ann B Meador, Mukerrem CakmakAbstract:Silica aerogels are sol−gel-derived materials consisting of interconnected nanoparticle building blocks that form an open and highly porous three-dimensional silica network. Flexible aerogel films could have wide applications in various thermal insulation systems. However, aerogel thin films produced with a pure sol−gel process have inherent disadvantages, such as high fragility and moisture sensitivity, that hinder wider applications of these materials. We have developed synthesis and manufacturing methods to incorporate electrospun polyurethane nanofibers into the cast sol film prior to gelation of the silica-based gel in order to reinforce the structure and overcome disadvantages such as high fragility and poor mechanical strength. In this method, a two-stage sol−gel process was employed: (1) acid-catalyzed tetraethyl orthosilicate hydrolysis and (2) base-catalyzed gelation. By precisely controlling the sol gelation kinetics with the amount of base present in the formulation, nanofibers were electrospu...
-
Flexible nanofiber-reinforced aerogel (Xerogel) synthesis, manufacture, and characterization
ACS Applied Materials and Interfaces, 2009Co-Authors: Lichun Li, Baris Yalcin, Baochau N Nguyen, Mary Ann B Meador, Miko CakmakAbstract:Silica aerogels are sol-gel-derived materials consisting of interconnected nanoparticle building blocks that form an open and highly porous three-dimensional silica network. Flexible aerogel films could have wide applications in various thermal insulation systems. However, aerogel thin films produced with a pure sol-gel process have inherent disadvantages, such as high fragility and moisture sensitivity, that hinder wider applications of these materials. We have developed synthesis and manufacturing methods to incorporate electrospun polyurethane nanofibers into the cast sol film prior to gelation of the silica-based gel in order to reinforce the structure and overcome disadvantages such as high fragility and poor mechanical strength. In this method, a two-stage sol-gel process was employed: (1) acid-catalyzed tetraethyl orthosilicate hydrolysis and (2) base-catalyzed gelation. By precisely controlling the sol gelation kinetics with the amount of base present in the formulation, nanofibers were electrospun into the sol before the onset of the gelation process and uniformly embedded in the silica network. Nanofiber reinforcement did not alter the thermal conductivity and rendered the final composite film bendable and flexible.
