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Sample records for activated carbon aerogels

  1. A comparison of the electrochemical behavior of carbon aerogels and activated carbon fiber cloths

    SciTech Connect

    Tran, T.D.; Alviso, C.T.; Hulsey, S.S.; Nielsen, J.K.; Pekala, R.W.

    1996-05-10

    Electrochemical capacitative behavior of carbon aerogels and commercial carbon fiber cloths was studied in 5M KOH, 3M sulfuric acid, and 0.5M tetrethylammonium tetrafluoroborate/propylene carbonate electrolytes. The resorcinol-formaldehyde based carbon aerogels with a range of denisty (0.2-0.85 g/cc) have open-cell structures with ultrafine pore sizes (5-50 nm), high surface area (400-700 m{sup 2}/g), and a solid matrix composed of interconnected particles or fibers with characteristic diameters of 10 nm. The commercial fiber cloths in the density range 0.2-04g/cc have high surface areas (1000-2500 m{sup 2}/g). The volumetric capacitances of high-density aerogels are shown to be comparable to or exceeding those from activated carbon fibers. Electrochemical behavior of these materials in various electrolytes is compared and related to their physical properties.

  2. High surface area silicon carbide-coated carbon aerogel

    DOEpatents

    Worsley, Marcus A; Kuntz, Joshua D; Baumann, Theodore F; Satcher, Jr, Joe H

    2014-01-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust. Carbon aerogels can be coated with sol-gel silica and the silica can be converted to silicone carbide, improved the thermal stability of the carbon aerogel.

  3. Nano-sized Mn-doped activated carbon aerogel as electrode material for electrochemical capacitor: effect of activation conditions.

    PubMed

    Lee, Yoon Jae; Park, Hai Woong; Park, Sunyoung; Song, In Kyu

    2012-07-01

    Carbon aerogel (CA) was prepared by a sol-gel polymerization of resorcinol and formaldehyde, and a series of activated carbon aerogels (ACA-KOH-X, X = 0, 0.3, 0.7, 1, and 2) were then prepared by a chemical activation using different amount of potassium hydroxide (X represented weight ratio of KOH with respect to CA). Specific capacitances of activated carbon aerogels were measured by cyclic voltammetry and galvanostatic charge/discharge methods in 6 M KOH electrolyte. Among the samples prepared, ACA-KOH-0.7 showed the highest specific capacitance (149 F/g). In order to combine excellent electrochemical performance of activated carbon aerogel with pseudocapacitive property of manganese oxide, 7 wt% Mn was doped on activated carbon aerogel (Mn/ACA-KOH-0.7) by an incipient wetness impregnation method. For comparison, 7 wt% Mn was also impregnated on carbon aerogel (Mn/ACA-KOH-0) by the same method. It was revealed that 7 wt% Mn-doped activated carbon aerogel (Mn/ACA-KOH-0.7) showed higher specific capacitance than 7 wt% Mn-doped carbon aerogel (Mn/ACA-KOH-0) (178 F/g vs. 98 F/g). The enhanced capacitance of Mn/ACA-KOH-0.7 was attributed to the outstanding electric properties of activated carbon aerogel as well as the faradaic redox reactions of manganese oxide. PMID:22966708

  4. KOH catalysed preparation of activated carbon aerogels for dye adsorption.

    PubMed

    Ling, Sie King; Tian, H Y; Wang, Shaobin; Rufford, Thomas; Zhu, Z H; Buckley, C E

    2011-05-01

    Organic carbon aerogels (CAs) were prepared by a sol-gel method from polymerisation of resorcinol, furfural, and hexamethylenetetramine catalysed by KOH at around pH 9 using ambient pressure drying. The effect of KOH in the sol-gel on CA synthesis was studied. It was found that addition of KOH prior to the sol-gel polymerisation process improved thermal stability of the gel, prevented the crystallinity of the gel to graphite, increased the microporosity of CA and promoted activation of CA. The CAs prepared using the KOH catalyst exhibited higher porosity than uncatalysed prepared samples. Activation in CO(2) at higher temperature also enhanced the porosity of CAs. Adsorption tests indicated that the CAs were effective for both basic and acid dye adsorption and the adsorption increased with increasing surface area and pore volume. The kinetic adsorption of dyes was diffusion control and could be described by the second-order kinetic model. The equilibrium adsorption of dyes was higher than activated carbon. PMID:21345448

  5. CO2 Activated Carbon Aerogel with Enhanced Electrochemical Performance as a Supercapacitor Electrode Material.

    PubMed

    Lee, Eo Jin; Lee, Yoon Jae; Kim, Jeong Kwon; Hong, Ung Gi; Yi, Jongheop; Yoon, Jung Rag; Song, In Kyu

    2015-11-01

    Carbon aerogel (CA) was prepared by a sol-gel polymerization of resorcinol and formaldehyde in ambient conditions. A series of activated carbon aerogels (ACA-X, X = 1, 2, 3, 4, 5, and 6 h) were then prepared by CO2 activation of CA with a variation of activation time (X) for use as an electrode material for supercapacitor. Specific capacitances of CA and ACA-X electrodes were measured by cyclic voltammetry and galvanostatic charge/discharge methods in 6 M KOH electrolyte. Among the samples, ACA-5 h showed the highest BET surface area (2574 m2/g) and the highest specific capacitance (100 F/g). It was found that CO2 activation was a very efficient method for enhancing physicochemical property and supercapacitive electrochemical performance of activated carbon aerogel.

  6. CO2 Activated Carbon Aerogel with Enhanced Electrochemical Performance as a Supercapacitor Electrode Material.

    PubMed

    Lee, Eo Jin; Lee, Yoon Jae; Kim, Jeong Kwon; Hong, Ung Gi; Yi, Jongheop; Yoon, Jung Rag; Song, In Kyu

    2015-11-01

    Carbon aerogel (CA) was prepared by a sol-gel polymerization of resorcinol and formaldehyde in ambient conditions. A series of activated carbon aerogels (ACA-X, X = 1, 2, 3, 4, 5, and 6 h) were then prepared by CO2 activation of CA with a variation of activation time (X) for use as an electrode material for supercapacitor. Specific capacitances of CA and ACA-X electrodes were measured by cyclic voltammetry and galvanostatic charge/discharge methods in 6 M KOH electrolyte. Among the samples, ACA-5 h showed the highest BET surface area (2574 m2/g) and the highest specific capacitance (100 F/g). It was found that CO2 activation was a very efficient method for enhancing physicochemical property and supercapacitive electrochemical performance of activated carbon aerogel. PMID:26726618

  7. Preparation of Nano-Porous Activated Carbon Aerogel Using a Single-Step Activation Method for Use as High-Power EDLC Electrode in Organic Electrolyte.

    PubMed

    Kwon, Soon Hyung; Kim, Bum-Soo; Kim, Sang-Gil; Lee, Byung-Jun; Kim, Myung-Soo; Jung, Ji Chul

    2016-05-01

    Carbon aerogel was chemically activated with KOH using two different activation methods (conventional activation method and single-step activation method) to yield the nano-porous activated carbon aerogel. Both nano-porous activated carbon aerogels exhibited a better capacitive behavior than carbon aerogel in organic electrolyte. However, a drastic decrease in the specific capacitance with increasing current density was observed in the ACA_C (activated carbon aerogel prepared by a conventional activation method), which is a general tendency of carbon electrode for EDLC in organic electrolyte. Interestingly, the specific capacitance of ACA_S electrode (activated carbon aerogel prepared by a single-step activation method) decreased slowly with increasing current density and its CV curve maintained a rectangular shape well even at a high scan rate of 500 mV/s. The enhanced electrochemical performance of ACA_S at a high current density was attributed to its low ionic resistance caused by the well-developed pore structure with appropriate pore size for easy moving of organic electrolyte ion. Therefore, it can be concluded that single-step activation method could be one of the efficient methods for preparation of nano-porous activated carbon aerogel electrode for high-power EDLC in organic electrolyte. PMID:27483797

  8. Preparation of Nano-Porous Activated Carbon Aerogel Using a Single-Step Activation Method for Use as High-Power EDLC Electrode in Organic Electrolyte.

    PubMed

    Kwon, Soon Hyung; Kim, Bum-Soo; Kim, Sang-Gil; Lee, Byung-Jun; Kim, Myung-Soo; Jung, Ji Chul

    2016-05-01

    Carbon aerogel was chemically activated with KOH using two different activation methods (conventional activation method and single-step activation method) to yield the nano-porous activated carbon aerogel. Both nano-porous activated carbon aerogels exhibited a better capacitive behavior than carbon aerogel in organic electrolyte. However, a drastic decrease in the specific capacitance with increasing current density was observed in the ACA_C (activated carbon aerogel prepared by a conventional activation method), which is a general tendency of carbon electrode for EDLC in organic electrolyte. Interestingly, the specific capacitance of ACA_S electrode (activated carbon aerogel prepared by a single-step activation method) decreased slowly with increasing current density and its CV curve maintained a rectangular shape well even at a high scan rate of 500 mV/s. The enhanced electrochemical performance of ACA_S at a high current density was attributed to its low ionic resistance caused by the well-developed pore structure with appropriate pore size for easy moving of organic electrolyte ion. Therefore, it can be concluded that single-step activation method could be one of the efficient methods for preparation of nano-porous activated carbon aerogel electrode for high-power EDLC in organic electrolyte.

  9. Structure-property relationships of carbon aerogels

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Kong, F.M.

    1993-12-01

    Of the organic reactions in sol-gel polymerizations, the most studied reaction is the aqueous polycondensation of resorcinol with formaldehyde; the resulting crosslinked gels are supercritically dried from CO{sub 2} to give resorcinol-formaldehyde (RF) aerogels. These aerogels can be pyrolyzed to form vitreous carbon monoliths with black color, high porosity, ultrafine cell/pore size, high surface area, and interconnected particles of the organic precursor. The structure and properties of the carbon aerogels depend on R/C (resorcinol/catalyst) ratio of starting solution, pyrolysis temperature, and chemical activation. Each variable is discussed. Carbon aerogels provide an almost ideal electrode material (in double-layer capacitors) owing to low electrical resistivity (<40 mohm-cm), controllable pore size distribution (5--500 {angstrom}), and high volumetric surface areas ({approximately}500 m{sup 2}/cm{sup 3}).

  10. Ultralight multiwalled carbon nanotube aerogel.

    PubMed

    Zou, Jianhua; Liu, Jianhua; Karakoti, Ajay Singh; Kumar, Amit; Joung, Daeha; Li, Qiang; Khondaker, Saiful I; Seal, Sudipta; Zhai, Lei

    2010-12-28

    Ultralight multiwalled carbon nanotube (MWCNT) aerogel is fabricated from a wet gel of well-dispersed pristine MWCNTs. On the basis of a theoretical prediction that increasing interaction potential between CNTs lowers their critical concentration to form an infinite percolation network, poly(3-(trimethoxysilyl) propyl methacrylate) (PTMSPMA) is used to disperse and functionalize MWCNTs where the subsequent hydrolysis and condensation of PTMSPMA introduces strong and permanent chemical bonding between MWCNTs. The interaction is both experimentally and theoretically proven to facilitate the formation of a MWCNT percolation network, which leads to the gelation of MWCNT dispersion at ultralow MWCNT concentration. After removing the liquid component from the MWCNT wet gel, the lightest ever free-standing MWCNT aerogel monolith with a density of 4 mg/cm(3) is obtained. The MWCNT aerogel has an ordered macroporous honeycomb structure with straight and parallel voids in 50-150 μm separated by less than 100 nm thick walls. The entangled MWCNTs generate mesoporous structures on the honeycomb walls, creating aerogels with a surface area of 580 m(2)/g which is much higher than that of pristine MWCNTs (241 m(2)/g). Despite the ultralow density, the MWCNT aerogels have an excellent compression recoverable property as demonstrated by the compression test. The aerogels have an electrical conductivity of 3.2 × 10(-2) S·cm(-1) that can be further increased to 0.67 S·cm(-1) by a high-current pulse method without degrading their structures. The excellent compression recoverable property, hierarchically porous structure with large surface area, and high conductivity grant the MWCNT aerogels exceptional pressure and chemical vapor sensing capabilities. PMID:21090673

  11. Desalination with carbon aerogel electrodes

    SciTech Connect

    Farmer, J.C.; Richardson, J.H.; Fix, D.V.

    1996-10-21

    An electrically regenerated electrosorption process known as carbon aerogel CDI was developed for continuously removing ionic impurities from aqueous streams. A salt solution flows in a channel formed by pairs of parallel carbon aerogel electrodes. Each electrode has a very high BET surface area and very low resistivity. After polarization, anions and cations are removed from electrolyte by the electric field and electrosorbed onto the carbon aerogel. The solution is thus separated into two streams, brine and water. Based on this, carbon aerogel CDI appears to be an energy-efficient alternative to evaporation, electrodialysis, and reverse osmosis. The energy required by this process is about QV/2, plus losses. Estimated energy requirement for sea water desalination is 18-27 Wh gal{sup -1}, depending on cell voltage and flow rate. The requirement for brackish water desalination is less, 1.2-2.5 Wh gal{sup -1} at 1600 ppM. This is assuming that stored electrical energy is reclaimed during regeneration.

  12. Carbon aerogel electrodes for direct energy conversion

    DOEpatents

    Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

    1997-01-01

    A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome.

  13. Carbon aerogel electrodes for direct energy conversion

    DOEpatents

    Mayer, S.T.; Kaschmitter, J.L.; Pekala, R.W.

    1997-02-11

    A direct energy conversion device, such as a fuel cell, using carbon aerogel electrodes is described, wherein the carbon aerogel is loaded with a noble catalyst, such as platinum or rhodium and soaked with phosphoric acid, for example. A separator is located between the electrodes, which are placed in a cylinder having plate current collectors positioned adjacent the electrodes and connected to a power supply, and a pair of gas manifolds, containing hydrogen and oxygen positioned adjacent the current collectors. Due to the high surface area and excellent electrical conductivity of carbon aerogels, the problems relative to high polarization resistance of carbon composite electrodes conventionally used in fuel cells are overcome. 1 fig.

  14. The aerocapacitor: A carbon aerogel based supercapacitor

    SciTech Connect

    Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

    1992-12-01

    During the 1980's, a wide variety of carbon foams, formed by the pyrolysis of polymeric foams, were developed at several Department of Energy Laboratories. These foams are known for their monolithic structure and the ability to tailor their critical parameters (e.g. porosity, density). Lawrence Livermore National Laboratory (LLNL) exclusively developed a unique type of carbon foam, known as carbon aerogels. Carbon aerogels are a special class of open-cell foams with (1) homogeneous ultrafine particle and pore size, (2) very large useful surface area per unit volume, and (3) monolithic structure, that yields (4) excellent electrical conductivity due to the intimate connection of the particles. We have applied carbon aerogels to make an Aerocapacitor''; a high power- and energy-density electrochemical double layer capacitor (EDLC) that uses carbon aerogels as electrodes. Carbon aerogel surface areas range from about 100 to 700 m[sup 2]/cc (as measured by BET analysis), with bulk densities of 0.05 to 1.0 g/cm[sup 3] and their morphology allows stored energy to be released rapidly, resulting in high power-densities.

  15. The aerocapacitor: A carbon aerogel based supercapacitor

    SciTech Connect

    Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

    1992-12-01

    During the 1980`s, a wide variety of carbon foams, formed by the pyrolysis of polymeric foams, were developed at several Department of Energy Laboratories. These foams are known for their monolithic structure and the ability to tailor their critical parameters (e.g. porosity, density). Lawrence Livermore National Laboratory (LLNL) exclusively developed a unique type of carbon foam, known as carbon aerogels. Carbon aerogels are a special class of open-cell foams with (1) homogeneous ultrafine particle and pore size, (2) very large useful surface area per unit volume, and (3) monolithic structure, that yields (4) excellent electrical conductivity due to the intimate connection of the particles. We have applied carbon aerogels to make an ``Aerocapacitor``; a high power- and energy-density electrochemical double layer capacitor (EDLC) that uses carbon aerogels as electrodes. Carbon aerogel surface areas range from about 100 to 700 m{sup 2}/cc (as measured by BET analysis), with bulk densities of 0.05 to 1.0 g/cm{sup 3} and their morphology allows stored energy to be released rapidly, resulting in high power-densities.

  16. Carbon Aerogels for Hydrogen Storage

    SciTech Connect

    Baumann, T F; Worsley, M; Satcher, J H

    2008-08-11

    This effort is focused on the design of new nanostructured carbon-based materials that meet the DOE 2010 targets for on-board vehicle hydrogen storage. Carbon aerogels (CAs) are a unique class of porous materials that possess a number of desirable structural features for the storage of hydrogen, including high surface areas (over 3000 m{sup 2}/g), continuous and tunable porosities, and variable densities. In addition, the flexibility associated with CA synthesis allows for the incorporation of modifiers or catalysts into the carbon matrix in order to alter hydrogen sorption enthalpies in these materials. Since the properties of the doped CAs can be systematically modified (i.e. amount/type of dopant, surface area, porosity), novel materials can be fabricated that exhibit enhanced hydrogen storage properties. We are using this approach to design new H{sub 2} sorbent materials that can storage appreciable amounts of hydrogen at room temperature through a process known as hydrogen spillover. The spillover process involves the dissociative chemisorption of molecular hydrogen on a supported metal catalyst surface (e.g. platinum or nickel), followed by the diffusion of atomic hydrogen onto the surface of the support material. Due to the enhanced interaction between atomic hydrogen and the carbon support, hydrogen can be stored in the support material at more reasonable operating temperatures. While the spillover process has been shown to increase the reversible hydrogen storage capacities at room temperature in metal-loaded carbon nanostructures, a number of issues still exist with this approach, including slow kinetics of H{sub 2} uptake and capacities ({approx} 1.2 wt% on carbon) below the DOE targets. The ability to tailor different structural aspects of the spillover system (i.e. the size/shape of the catalyst particle, the catalyst-support interface and the support morphology) should provide valuable mechanistic information regarding the critical aspects of the

  17. Carbon aerogels: An update on structure, properties, and applications

    SciTech Connect

    Pekala, R.W.; Mayer, S.T.; Kaschmitter, J.L.; Kong, F.M.

    1993-07-01

    Aerogels are unique porous materials whose composition, structure, and properties can be controlled at the nanometer scale. This paper examines the synthesis of organic aerogels and their carbonized derivatives. Carbon aerogels have low electrical resistivity, high surface area, and a tunable pore size. These materials are finding applications as electrodes in double layer capacitors.

  18. Carbon nanomaterials in silica aerogel matrices

    SciTech Connect

    Hamilton, Christopher E; Chavez, Manuel E; Duque, Juan G; Gupta, Gautam; Doorn, Stephen K; Dattelbaum, Andrew M; Obrey, Kimberly A D

    2010-01-01

    Silica aerogels are ultra low-density, high surface area materials that are extremely good thermal insulators and have numerous technical applications. However, their mechanical properties are not ideal, as they are brittle and prone to shattering. Conversely, single-walled carbon nanotubes (SWCNTs) and graphene-based materials, such as graphene oxide, have extremely high tensile strength and possess novel electronic properties. By introducing SWCNTs or graphene-based materials into aerogel matrices, it is possible to produce composites with the desirable properties of both constituents. We have successfully dispersed SWCNTs and graphene-based materials into silica gels. Subsequent supercritical drying results in monolithic low-density composites having improved mechanical properties. These nanocomposite aerogels have great potential for use in a wide range of applications.

  19. Desalination with carbon aerogel electrodes. Revision 1

    SciTech Connect

    Farmer, J.C.; Richardson, J.H.; Fix, D.V.; Thomson, S.L.; May, S.C.

    1996-12-04

    Electrically regenerated electrosorption process (carbon aerogel CDI) was developed by LLNL for continuously removing ionic impurities from aqueous streams. A salt solution flows in a channel formed by numerous pairs of parallel carbon aerogel electrodes. Each electrode has a very high BET surface area (2-5.4x10{sup 6}ft{sup 2}lb{sup -1} or 400-1100 m{sup 2}g{sup -1}) and very low electrical resistivity ({le}40 m{Omega}). Ions are removed from the electrolyte by the electric field and electrosorbed onto the carbon aerogel. It is concluded that carbon aerogel CDI may be an energy-efficient alternative to electrodialysis and reverse osmosis for desalination of brackish water ({le}5000 ppM). The intrinsic energy required by this process is about QV/2, where Q is the stored electrical charge and V is the voltage between the electrodes, plus losses. Estimated requirement for desalination of a 2000 ppM feed is -0.53-2.5 Wh/gal{sup -1} (0.5-2.4 kJ L{sup -1}), depending on voltage, flow rate, cell dimensions, aerogel density, recovery ratio, etc. This assumes that 50-70% of the stored electrical energy is reclaimed during regeneration (electrical discharge). Though the energy requirement for desalination of sea water is also low, this application will be much more difficult. Additional work will be required for desalination of streams that contain more than 5000 ppM total dissolved solids (2000 ppM will require electrochemical cells with extremely tight, demanding tolerances). At this present time, the process is best suited for streams with dilute impurities, as recently demonstrated during a field test at LLNL Treatment Facility C.

  20. Carbonates Found in Stardust Aerogel Tracks

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Leroux, H.; Tomeoka, K.; Zolensky, M.; Flynn, T.; Tyliszczak, T.; Butterworth, A.; Tomioka, N.; Ohnishi, I.; Messenger, K. Nakamura; Sandford, S.; Keller, L.; Jacobsen, C.

    2007-01-01

    Preliminary examination of particles collected from Comet Wild 2 suggest that this comet is chondritic and formed under multiple processes. The lack of any hydrated minerals strongly suggests that most, if not all of these processes were anhydrous [1,2,3]. However, carbonates were found in particles extracted from 4 different tracks in the aerogel. It is our belief that these carbonates have a terrestrial origin and are a contaminant in these samples.

  1. Granulated activated carbon modified with hydrophobic silica aerogel-potential composite materials for the removal of uranium from aqueous solutions.

    PubMed

    Coleman, Sabre J; Coronado, Paul R; Maxwell, Robert S; Reynolds, John G

    2003-05-15

    Aqueous solutions of 100 parts per billion (ppb) uranium at pH 7 were treated with granulated activated carbon (GAC) that had been modified with various formulations of hydrophobic aerogels. The composite materials were found to be superior in removing uranium from a stock solution compared to GAC alone evaluated by a modified ASTM D 3860-98 method for batch testing. The testing results were evaluated using a Freundlich adsorption model. The best performing material has parameters of n = 287 and Kf = 1169 compared to n = 1.00, and Kf = 20 for GAC alone. The composite materials were formed by mixing (CH3O)4Si with the hydrophobic sol-gel precursor, (CH3O)3SiCH2CH2CF3 and with specified modifiers, such as H3PO4, Ca(NO3)2, and (C2H5O)3SiCH2CH2P(O)(OC2H5)2, elation catalysts, and GAC in a supercritical reactor system. After gelation, supercritical extraction, and sieving, the composites were tested. Characterization by FTIR and 31P NMR indicate the formation of phosphate in the case of the H3PO4 and Ca(NO3)2 composites and phosphonic acid related compounds in the phosphonate composite. These composite materials have potential application in the clean up of groundwater at DOE and other facilities.

  2. Catalytic graphitization of carbon aerogels by transition metals

    SciTech Connect

    Maldonado-Hodar, F.J.; Moreno-Castilla, C.; Rivera-Utrilla, J.; Hanzawa, Y.; Yamada, Y.

    2000-05-02

    Carbon aerogels and Cr-, Fe-, Co-, and Ni-containing carbon aerogels were obtained by pyrolysis, at temperatures between 500 and 1,800 C, of the corresponding aerogels prepared by the sol-gel method from polymerization of resorcinol with formaldehyde. All samples were characterized by mercury porosimetry, nitrogen adsorption, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. Results obtained show that carbon aerogels are, essentially, macroporous materials that maintain large pore volumes even after pyrolysis at 1,800 C. For pyrolysis at temperatures higher than 1,000 C, the presence of the transition metals produced graphitized areas with three-dimensional stacking order, as shown by HRTEM, XRD, and Raman spectroscopy. HRTEM also showed that the metal-carbon containing aerogels were formed by polyhedral structures. Cr and Fe seem to be the best catalysts for graphitization of carbon aerogels.

  3. Effect on mass transference phenomena by textural change inside monolithic carbon aerogels

    NASA Astrophysics Data System (ADS)

    Chejne, F.; Camargo-Trillos, D.; Pabón, E.; Carrasco-Marin, F.

    2015-08-01

    The effects on mass transference phenomena due textural changes of monolithic carbon aerogels were studied by hexane adsorption. The monolithic carbon aerogels were prepared after carbonization of the organic aerogels obtained by resorcinol-formaldehyde polymerization, using p-toluenesulfonic acid (acid-catalyst) and sodium carbonate catalysts (basic-catalyst). Internal texture was modified by CO2 activation. The characterization by gas adsorption showed that the monolithic carbon aerogels presents a bi-modal pore size distribution with presence of both microporous and mesoporous. It was shown that the activation process of monolithic carbon aerogels increases their micropore volume bigger than the other one acid-catalyst aerogel. The mesopores volume in the carbon aerogels plays an important role on mass transport mechanism. The samples with presence of significant mesopore volume present a lower height of mass transfer zone than others less mesopore volume; therefore better efficiency of adsorption in mass transfer zone in dynamic adsorption. The breakthrough curve methodology proposed in this work has allowed finding a relationship between the structural parameters and dynamic adsorption variables, which opens new approaches for measuring textural parameters of material.

  4. Structure and performance of carbon aerogel electrodes

    SciTech Connect

    Pekala, R.W.; Mayer, S.T.; Poco, J.F.; Kaschmitter, J.L.

    1994-03-01

    The chemistry and physics of small clusters of atoms (1--100 nm) has received considerable attention in recent years because these assemblies often have properties between the molecular and bulk solid-state limits. The different properties can be explained in terms of the large fraction of atoms that are at the surface of a cluster as compared to the interior. Although the synthesis and properties of metal and. semiconductor clusters, metallocarbohedrenes, fullerenes, and nanotubes are the subject of extensive investigations, little attention has been paid to cluster-assembled porous materials. This oversight is of particular interest to us since we believe that aerogels are one of the few monolithic materials presently available where the benefits of cluster assembly can be demonstrated. In particular, the unique optical, thermal, acoustic, mechanical, and electrical properties of aerogels are directly related to their nanostructure, which is composed of interconnected particles (3--30 nm) with small interstitial pores (< 50 nm). This structure leads to extremely high surface areas (400--1100 m{sup 2}/g) with a large fraction of the atoms covering the surface of the interconnected particles. As a result of these structural features, carbon aerogels are finding applications as electrodes in supercapacitors with high energy and power densities.

  5. AEM and HREM evaluation of carbon nanostructures in silica aerogels

    SciTech Connect

    Song, X.Y.; Cao, W.; Hunt, A.J.

    1994-04-01

    Nanostructured carbon has been deposited in silica aerogels by chemical vapor infiltration using acetylene or ferrocene at moderate temperatures. Using analytical electron microscopy and high-resolution electron microscopy, we have observed various carbon rings and nanotubes in the silica aerogel-based carbon composite. Both X-ray microanalysis and nano-probe diffraction techniques have been used to confirm the presence of those carbon nanostructures. Morphologies and structural properties of the carbon nanotubes and rings have also been examined in detail.

  6. Aerogel and xerogel composites for use as carbon anodes

    DOEpatents

    Cooper, John F.; Tillotson, Thomas M.; Hrubesh, Lawrence W.

    2008-08-12

    Disclosed herein are aerogel and xerogel composite materials suitable for use as anodes in fuel cells and batteries. Precursors to the aerogel and xerogel compounds are infused with inorganic polymeric materials or carbon particles and then gelled. The gels are then pyrolyzed to form composites with internal structural support.

  7. Multiscale Modeling of Heat Conduction in Carbon Nanotube Aerogels

    NASA Astrophysics Data System (ADS)

    Gong, Feng; Papavassiliou, Dimitrios; Duong, Hai

    Carbon nanotube (CNT) aerogels have attracted a lot of interest due to their ultrahigh strength/weight and surface area/weight ratios. They are promising advanced materials used in energy storage systems, hydrogen storage media and weight-conscious devices such as satellites, because of their ultralight and highly porous quality. CNT aerogels can have excellent electrical conductivity and mechanical strength. However, the thermal conductivity of CNT aerogels are as low as 0.01-0.1 W/mK, which is five orders of magnitude lower than that of CNT (2000-5000 W/mK). To investigate the mechanisms for the low thermal conductivity of CNT aerogels, multiscale models are built in this study. Molecular dynamic (MD) simulations are first carried out to investigate the heat transfer between CNT and different gases (e.g. nitrogen and hydrogen), and the thermal conductance at CNT-CNT interface. The interfacial thermal resistances of CNT-gas and CNT-CNT are estimated from the MD simulations. Mesoscopic modeling of CNT aerogels are then built using an off-lattice Monte Carlo (MC) simulations to replicate the realistic CNT aerogels. The interfacial thermal resistances estimated from MD simulations are used as inputs in the MC models to predict the thermal conductivity of CNT aerogels. The volume fractions and the complex morphologies of CNTs are also quantified to study their effects on the thermal conductivity of CNT aerogels. The quantitative findings may help researchers to obtain the CNT aerogels with expected thermal conductivity.

  8. Contact-active antibacterial aerogels from cellulose nanofibrils.

    PubMed

    Henschen, Jonatan; Illergård, Josefin; Larsson, Per A; Ek, Monica; Wågberg, Lars

    2016-10-01

    The use of cellulose aerogels as antibacterial materials has been investigated by applying a contact-active layer-by-layer modification to the aerogel surface. Studying the adsorption of multilayers of polyvinylamine (PVAm) and polyacrylic acid to aerogels comprising crosslinked cellulose nanofibrils and monitoring the subsequent bacterial adhesion revealed that up to 26mgPVAmgaerogel(-1) was adsorbed without noticeably affecting the aerogel structure. The antibacterial effect was tested by measuring the reduction of viable bacteria in solution when the aerogels were present. The results show that >99.9% of the bacteria adhered to the surface of the aerogels. Microscopy further showed adherence of bacteria to the surfaces of the modified aerogels. These results indicate that it is possible to create materials with three-dimensional cellulose structures that adsorb bacteria with very high efficiency utilizing the high specific surface area of the aerogels in combination with their open structure. PMID:27391038

  9. Contact-active antibacterial aerogels from cellulose nanofibrils.

    PubMed

    Henschen, Jonatan; Illergård, Josefin; Larsson, Per A; Ek, Monica; Wågberg, Lars

    2016-10-01

    The use of cellulose aerogels as antibacterial materials has been investigated by applying a contact-active layer-by-layer modification to the aerogel surface. Studying the adsorption of multilayers of polyvinylamine (PVAm) and polyacrylic acid to aerogels comprising crosslinked cellulose nanofibrils and monitoring the subsequent bacterial adhesion revealed that up to 26mgPVAmgaerogel(-1) was adsorbed without noticeably affecting the aerogel structure. The antibacterial effect was tested by measuring the reduction of viable bacteria in solution when the aerogels were present. The results show that >99.9% of the bacteria adhered to the surface of the aerogels. Microscopy further showed adherence of bacteria to the surfaces of the modified aerogels. These results indicate that it is possible to create materials with three-dimensional cellulose structures that adsorb bacteria with very high efficiency utilizing the high specific surface area of the aerogels in combination with their open structure.

  10. Fabrication of hydrophobic, electrically conductive and flame-resistant carbon aerogels by pyrolysis of regenerated cellulose aerogels.

    PubMed

    Wan, Caichao; Lu, Yun; Jiao, Yue; Jin, Chunde; Sun, Qingfeng; Li, Jian

    2015-03-15

    In this paper, we reported miscellaneous carbon aerogels prepared by pyrolysis of regenerated cellulose aerogels that were fabricated by dissolution in a mild NaOH/PEG solution, freeze-thaw treatment, regeneration, and freeze drying. The as-prepared carbon aerogels were subsequently characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), nitrogen adsorption measurements, X-ray diffraction (XRD), Raman spectroscopy, and water contact angle (WCA) tests. The results showed that the carbon aerogels with pore diameters of 1-60 nm maintained interconnected three-dimensional (3D) network after the pyrolysis, and showed type-IV adsorption isotherm. The pyrolysis process leaded to the decomposition of oxygen-containing functional groups, the destruction of cellulose crystalline structure, and the formation of highly disordered amorphous graphite. Moreover, the carbon aerogels also had strong hydrophobicity, electrical conductivity and flame retardance, which held great potential in the fields of waterproof, electronic devices and fireproofing.

  11. Fabrication of hydrophobic, electrically conductive and flame-resistant carbon aerogels by pyrolysis of regenerated cellulose aerogels.

    PubMed

    Wan, Caichao; Lu, Yun; Jiao, Yue; Jin, Chunde; Sun, Qingfeng; Li, Jian

    2015-03-15

    In this paper, we reported miscellaneous carbon aerogels prepared by pyrolysis of regenerated cellulose aerogels that were fabricated by dissolution in a mild NaOH/PEG solution, freeze-thaw treatment, regeneration, and freeze drying. The as-prepared carbon aerogels were subsequently characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), nitrogen adsorption measurements, X-ray diffraction (XRD), Raman spectroscopy, and water contact angle (WCA) tests. The results showed that the carbon aerogels with pore diameters of 1-60 nm maintained interconnected three-dimensional (3D) network after the pyrolysis, and showed type-IV adsorption isotherm. The pyrolysis process leaded to the decomposition of oxygen-containing functional groups, the destruction of cellulose crystalline structure, and the formation of highly disordered amorphous graphite. Moreover, the carbon aerogels also had strong hydrophobicity, electrical conductivity and flame retardance, which held great potential in the fields of waterproof, electronic devices and fireproofing. PMID:25542115

  12. The application of carbon aerogel electrodes to desalination {ampersand} waste treatment

    SciTech Connect

    Farmer, J.C., Tran, T.D., Richardson, J.H., Fix, D.V., May, S.C., Thomson, S.L.

    1997-08-01

    An electrically-regenerated electrosorption process known as carbon aerogel capacitive deionization (CDI) has been developed by Lawrence Livermore National Laboratory (LLNL) for continuously removing ionic impurities from aqueous streams. A salt solution flows through an unobstructed channel formed by numerous pairs of parallel carbon aerogel electrodes. Each electrode has a very high Brunauer-Emmet-Teller (BET) surface area (2.0-5.4 x 1O{sup 6} ft{sup 2} lb{sup -1} or 400-1100) and very low electrical resistivity (< 40 m{omega} cm). Surface areas of 1.3 x 10{sup 7} ft{sup 2} lb{sup -1} (2600 m{sup 2} g{sup -1}) have been achieved activation. After polarization, anions and cations are removed from the electrolyte by the imposed electric field and electrosorbed onto the carbon aerogel. The solution is thus separated into two streams, concentrate and purified water. Based upon this analysis, it is concluded that carbon aerogel CDI may be an energy-efficient alternative to electrodialysis and reverse osmosis for the desalination of brackish water (< 5000 ppm), provided that cell geometries and aerogel properties are carefully tailored for such applications.

  13. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    DOEpatents

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr., Joe H.

    2016-10-04

    Disclosed here is a device comprising a porous carbon aerogel or composite thereof as an energy storage material, catalyst support, sensor or adsorbent, wherein the porous carbon aerogel comprises a network of interconnected struts comprising carbon nanotube bundles covalently crosslinked by graphitic carbon nanoparticles, wherein the carbon nanotubes account for 5 to 95 wt. % of the aerogel and the graphitic carbon nanoparticles account for 5 to 95 wt. % of the aerogel, and wherein the aerogel has an electrical conductivity of at least 10 S/m and is capable of withstanding strains of more than 10% before fracture.

  14. Preparation, microstructure and hydrogen sorption properties of nanoporous carbon aerogels under ambient drying

    NASA Astrophysics Data System (ADS)

    Tian, H. Y.; Buckley, C. E.; Mulè, S.; Paskevicius, M.; Dhal, B. B.

    2008-11-01

    Organic aerogels are prepared by the sol-gel method from polymerization of resorcinol with furfural. These aerogels are further carbonized in nitrogen in order to obtain their corresponding carbon aerogels (CA); a sample which was carbonized at 900 °C was also activated in a carbon dioxide atmosphere at 900 °C. The chemical reaction mechanism and optimum synthesis conditions are investigated by means of Fourier transform infrared spectroscopy and thermoanalyses (thermogravimetric/differential thermal analyses) with a focus on the sol-gel process. The carbon aerogels were investigated with respect to their microstructures, using small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and nitrogen adsorption measurements at 77 K. SAXS studies showed that micropores with a radius of gyration of <0.35 ± 0.07 to 0.55 ± 0.05 nm were present, and TEM measurements and nitrogen adsorption showed that larger mesopores were also present. Hydrogen storage properties of the CA were also investigated. An activated sample with a Brunauer-Emmett-Teller surface area of 1539 ± 20 m2 g-1 displayed a reasonably high hydrogen uptake at 77 K with a maximum hydrogen sorption of 3.6 wt% at 2.5 MPa. These results suggest that CA are promising candidate hydrogen storage materials.

  15. Carbon nanotube networks in epoxy composites and aerogels

    NASA Astrophysics Data System (ADS)

    Bryning, Mateusz B.

    This thesis describes the properties of carbon nanotube networks in epoxy composites and in novel carbon nanotube aerogels. SWNT Epoxy composites were created using a new procedure that enabled us to control SWNT concentration and dispersion quality in the composite. The composites exhibited percolation-like electrical conductivity with threshold volume fractions in the semi-dilute nanotube concentration regime. The observed electrical conductivites are described in terms of nanotube length, degree of aggregation, and sample homogeneity. By modifying the procedure to allow for nanotube chaining, conductive composites were created at SWNT volume fractions as low as 5.2 (+1.9/-0.5) x 10-5, the lowest reported to date. The thermal conductivity of SWNT-epoxy composites is also investigated. Composites were prepared using suspensions of SWNTs in N-N-Dimethylformamide (DMF) or surfactant stabilized aqueous SWNT suspensions. Thermal conductivity enhancement was observed in both types of composites, but DMF-processed composites showed an advantage at SWNT volume fractions between φ ˜ 0.001 to 0.005. Surfactant processed samples, however, allowed greater SWNT loading at which a larger overall enhancement (64 +/- 9) % at φ ˜ 0.1 was observed. The enhancement differences are attributed to a tenfold higher SWNT/solid-composite interfacial thermal resistance in the surfactant-processed composites over DMF-processed composites. The interfacial resistance was extracted from the data using effective medium theory. Carbon nanotube aerogels were created by freeze drying and critical point drying aqueous carbon nanotube gels. The resulting aerogels have densities of approximately 0.01 to 0.06 g/cm3 and maintain the dimensions of the wet gel. Critical point dried aerogels also preserve the microscopic three-dimensional network of debundled carbon nanotubes of the original gel. Pure SWNT aerogels are self-supporting. Reinforcement with small amounts of added polyvinyl alcohol (PVA

  16. Electrochemical behavior of carbon aerogels derived from different precursors

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Nielson, J.K.; Tran, T.D.; Reynolds, G.M.; Dresshaus, M.S.

    1995-04-01

    The ability to tailor the structure and properties of porous carbons has led to their increased use as electrodes in energy storage devices. Our research focuses on the synthesis and characterization of carbon aerogels for use in electrochemical double layer capacitors. Carbon aerogels are formed from the sol-gel polymerization of (1) resorcinol-formaldehyde or (2) phenolic-furfural, followed by supercritical drying from carbon dioxide, and subsequent pyrolysis in an inert atmosphere. These materials can be produced as monoliths, composites, thin films, powders, or microspheres. In all cases, the areogels have an open-cell structure with an ultrafine pore size (<100 nm), high surface area (400-1 100 m{sup 2}/g), and a solid matrix composed of interconnected particles, fibers, or platelets with characteristic dimensions of 10 nm. This paper examines the effects of the carbon precursor and processing conditions on electrochemical performance in aqueous and organic electrolytes.

  17. Synthesis, characterization, and modeling of hydrogen storage in carbon aerogels

    SciTech Connect

    Pekala, R.W.; Coronado, P.R.; Calef, D.F.

    1995-04-01

    Carbon aerogels are a special class of open-cell foams with an ultrafine cell/pore size (<50 nm), high surface area (600-800 m{sup 2}/g), and a solid matrix composed of interconnected colloidal-like particles or fibers with characteristic diameters of 10 nm. These materials are usually synthesized from the sol-gel polymerization of resorcinol-formaldehyde or phenolic-furfural, followed by supercritical extraction of the solvent and pyrolysis in an inert atmosphere. The resultant aerogel has a nanocrystalline structure with micropores (<2 nm diameter) located within the solid matrix. Carbon aerogel monoliths can be prepared at densities ranging from 0.05-1.0 g/cm{sup 3}, leading to volumetric surface areas (> 500 m{sup 2}/cm{sup 3}) that are much larger than commercially available materials. This research program is directed at optimization of the aerogel structure for maximum hydrogen adsorption over a wide range of temperatures and pressures. Computer modeling of hydrogen adsorption at carbon surfaces was also examined.

  18. Monte Carlo Study on Carbon-Gradient-Doped Silica Aerogel Insulation.

    PubMed

    Zhao, Y; Tang, G H

    2015-04-01

    Silica aerogel is almost transparent for wavelengths below 8 µm where significant energy is transferred by thermal radiation. The radiative heat transfer can be restricted at high temperature if doped with carbon powder in silica aerogel. However, different particle sizes of carbon powder doping have different spectral extinction coefficients and the doped carbon powder will increase the solid conduction of silica aerogel. This paper presents a theoretical method for determining the optimal carbon doping in silica aerogel to minimize the energy transfer. Firstly we determine the optimal particle size by combining the spectral extinction coefficient with blackbody radiation and then evaluate the optimal doping amount between heat conduction and radiation. Secondly we develop the Monte Carlo numerical method to study radiative properties of carbon-gradient-doped silica aerogel to decrease the radiative heat transfer further. The results indicate that the carbon powder is able to block infrared radiation and thus improve the thermal insulating performance of silica aerogel effectively.

  19. Characterization and electrochemical performance of graphene-containing carbon aerogel for supercapacitor.

    PubMed

    Lee, Yoon Jae; Park, Hai Woong; Hong, Ung Gi; Song, In Kyu

    2013-12-01

    Graphene-containing carbon aerogel was prepared by a polycondensation of resorcinol with formaldehyde using chemically exfoliated graphene oxide in ambient conditions, and its electrochemical performance as an electrode for supercapacitor was examined. The effect of pH in the preparation of RFGO (resorcinol-formaldehyde and graphene oxide) solution on the physical and electrochemical properties of graphene-containing carbon aerogel was investigated. For comparison, graphene-free carbon aerogel was also prepared. Among the samples, graphene-containing carbon aerogel prepared at pH 6.5 showed the highest BET surface area (733 m2/g) and the largest pore volume (1.39 cm3/g) with well-developed porous structure. Electrochemical properties of graphene-containing carbon aerogel and graphene-free carbon aerogel electrodes were measured by cyclic voltammetry at a scan rate of 10 mV/sec and by charge/discharge test at constant current of 1 A/g in 6 M KOH electrolyte. From cyclic voltammetry measurements, it was found that graphene-containing carbon aerogel prepared at pH 6.5 showed higher specific capacitance than graphene-free carbon aerogel (63 F/g vs. 54 F/g). Specific capacitance calculated by charge/discharge test also revealed that graphene-containing carbon aerogel prepared at pH 6.5 showed higher specific capacitance than graphene-free carbon aerogel (85 F/g vs. 79 F/g). Thus, electrochemical performance of graphene-containing carbon aerogel prepared at pH 6.5 could be enhanced by adding graphene into carbon aerogel.

  20. Effects of processing conditions on the physical and electrochemical properties of carbon aerogel composites

    SciTech Connect

    Tran, T D; Lenz, D; Kinoshita, K; Droege, M

    2000-10-26

    The carbon aerogel/carbon paper composites have physical properties similar to those of monolithic carbon aerogels but do not require supercritical extraction during fabrication. The resorcinol-formaldehyde based carbon aerogel phase is intertwined between the fibers of a commercial carbon paper. The resulting composites have variable densities (0.4-0.6 g/cc), high surface areas (300-600 m{sup 2}/g), and controllable pore sizes and pore distribution. The effects of the resorcinol-formaldehyde concentrations (50-70% w/v) and the pyrolysis temperature (600-1050 C) were studied in an attempt to tailor the aerogel microstructure and properties. The composite physical properties and structure were analyzed by transmission electron microscopy and multipoint-BET analyses and related to electrochemical capacitive data in 5M KOH. These thin carbon aerogel/carbon paper composite electrodes are used in experiments with electrochemical double-layer capacitors and capacitive deionization.

  1. Capacitive, deionization with carbon aerogel electrodes: Carbonate, sulfate, and phosphate

    SciTech Connect

    Farmer, J.C.; Fix, D.V.; Mack, G.V.; Pekala, R.W.; Poco, J.F.

    1995-07-24

    A process for the capacitive deionization (CDI) of water with a stack of carbon aerogel electrodes has been developed by Lawrence Livermore National Laboratory. Unlike ion exchange, one of the more conventional deionization processes, no chemicals are required for regeneration of the system. Electricity is used instead. Water with various anions and cations is pumped through the electrochemical cell. After polarization, ions are electrostatically removed from the water and held in the electric double layers formed at the surfaces of electrodes. The water leaving the cell is purified, as desired. The effects of cell voltage on the electrosorption capacities for Na{sub 2}SO{sub 4}, Na{sub 3}PO{sub 4}, and Na{sub 2}CO{sub 3} have been investigated and are reported here. Results for NaCl and NaNO{sub 3} have been reported previously. Possible applications for CDI are as a replacement for ion exchange processes which remove heavy metals and radioisotopes from process and waste water in various industries, as well as to remove inorganic ions from feedwater for fossil and nuclear power plants.

  2. Aerogel and xerogel composites for use as carbon anodes

    DOEpatents

    Cooper, John F.; Tillotson, Thomas M.; Hrubesh, Lawrence W.

    2010-10-12

    A method for forming a reinforced rigid anode monolith and fuel and product of such method. The method includes providing a solution of organic aerogel or xerogel precursors including at least one of a phenolic resin, phenol (hydroxybenzene), resorcinol(1,3-dihydroxybenzene), or catechol(1,2-dihydroxybenzene); at least one aldehyde compound selected from the group consisting of formaldehyde, acetaldehyde, and furfuraldehyde; and an alkali carbonate or phosphoric acid catalyst; adding internal reinforcement materials comprising carbon to said precursor solution to form a precursor mixture; gelling said precursor mixture to form a composite gel; drying said composite gel; and pyrolyzing said composite gel to form a wettable aerogel/carbon composite or a wettable xerogel/carbon composite, wherein said composites comprise chars and said internal reinforcement materials, and wherein said composite is suitable for use as an anode with the chars being fuel capable of being combusted in a molten salt electrochemical fuel cell in the range from 500 C to 800 C to produce electrical energy. Additional methods and systems/compositions are also provided.

  3. Formation of Carbon Nanostructures in Cobalt- and Nickel-Doped Carbon Aerogels

    SciTech Connect

    Fu, R; Baumann, T F; Cronin, S; Dresselhaus, G; Dresselhaus, M; Satcher, Jr., J H

    2004-11-09

    We have prepared carbon aerogels (CAs) doped with cobalt or nickel through sol-gel polymerization of formaldehyde with the potassium salt of 2,4-dihydroxybenzoic acid, followed by ion-exchange with M(NO{sub 3}){sub 2} (where M = Co{sup 2+} or Ni{sup 2+}), supercritical drying with liquid CO{sub 2} and carbonization at temperatures between 400 C and 1050 C under an N{sub 2} atmosphere. The nanostructures of these metal-doped carbon aerogels were characterized by elemental analysis, nitrogen adsorption, high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Metallic nickel and cobalt nanoparticles are generated during the carbonization process at about 400 C and 450 C, respectively, forming nanoparticles that are {approx}4 nm in diameter. The sizes and size dispersion of the metal particles increase with increasing carbonization temperatures for both materials. The carbon frameworks of the Ni- and Co-doped aerogels carbonized below 600 C mainly consist of interconnected carbon particles with a size of 15 to 30 nm. When the samples are pyrolyzed at 1050 C, the growth of graphitic nanoribbons with different curvatures is observed in the Ni and Co-doped carbon aerogel materials. The distance of graphite layers in the nanoribbons is about 0.38 nm. These metal-doped CAs retain the overall open cell structure of metal-free CAs, exhibiting high surface areas and pore diameters in the micro and mesoporic region.

  4. Hierarchical Nafion enhanced carbon aerogels for sensing applications

    NASA Astrophysics Data System (ADS)

    Weng, Bo; Ding, Ailing; Liu, Yuqing; Diao, Jianglin; Razal, Joselito; Lau, King Tong; Shepherd, Roderick; Li, Changming; Chen, Jun

    2016-02-01

    This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m-1, and a specific capacity of 136.8 F g-1 after reduction. Therefore, NECAG monoliths performed well as a gas sensor and as a biosensor with high sensitivity and selectivity. The remarkable sensitivity of 8.52 × 103 μA mM-1 cm-2 was obtained in dopamine (DA) detection, which is two orders of magnitude better than the literature reported values using graphene aerogel electrodes made from a porous Ni template. These outstanding properties make the NECAG a promising electrode candidate for a wide range of applications. Further in-depth investigations are being undertaken to probe the structure-property relationship of NECAG monoliths prepared under various conditions.This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m-1, and a specific capacity of 136.8 F g-1 after reduction. Therefore, NECAG

  5. Polybenzoxazine aerogels: Synthesis, characterization, conversion to porous carbons, and energetic composites

    NASA Astrophysics Data System (ADS)

    Mahadik-Khanolkar, Shruti

    Aerogels are nanoporous, low-density bulk objects, consisting of three-dimensional assemblies of nanoparticle. Structured similarly, polymeric aerogels are emerging as a mechanically strong alternative to traditional silica aerogels, which are fragile. Amongst polymeric aerogels, those based on polybenzoxazine (PBO - a type of phenolic resin), are extremely robust and comprise an economic alternative to resorcinol-formaldehyde aerogels, also a class of phenolic resins, as the main source of carbon aerogels. The drawback of the PBO chemistry has been the long (days) processing time at high-temperatures (>130 °C). Herewith, we have developed an energy- and time-efficient process to PBO aerogels by inducing acid-catalyzed gelation at room-temperature completed in a few hours. The new aerogels are compared directly with their conventional counterparts and are found equivalent or better in terms of mechanical strength, thermal insulation value, surface area and carbonization yield. Hexahydrated iron chloride (FeCl3.6H2O) is a fairly strong Bronsted acid, which, based on the above, catalyzes formation interpenetrating networks of PBO and iron oxide nanoparticles (PBO-FeOx). Pyrolysis of that intimate mixture of a carbon source (PBO) and iron oxide undergoes smelting to highly porous (>90% v/v) monolithic metallic iron aerogels. The porous network was loaded with oxidizers (e.g., LiClO4) into a new class of energetic materials (thermites, explosives, pyrotechnics). The PBO aerogels developed here comprise a wide-base platform for use as thermal insulators in civil and transportation applications (PBO aerogels themselves), electrodes for fuel cells, lithium ion batteries (nanoporous carbons), catalysts and energetic materials (PBO-FeOx).

  6. Carbon aerogel composites prepared by ambient drying and using oxidized polyacrylonitrile fibers as reinforcements.

    PubMed

    Feng, Junzong; Zhang, Changrui; Feng, Jian; Jiang, Yonggang; Zhao, Nan

    2011-12-01

    Carbon fiber-reinforced carbon aerogel composites (C/CAs) for thermal insulators were prepared by copyrolysis of resorcinol-formaldehyde (RF) aerogels reinforced by oxidized polyacrylonitrile (PAN) fiber felts. The RF aerogel composites were obtained by impregnating PAN fiber felts with RF sols, then aging, ethanol exchanging, and drying at ambient pressure. Upon carbonization, the PAN fibers shrink with the RF aerogels, thus reducing the difference of shrinkage rates between the fiber reinforcements and the aerogel matrices, and resulting in C/CAs without any obvious cracks. The three point bend strength of the C/CAs is 7.1 ± 1.7 MPa, and the thermal conductivity is 0.328 W m(-1) K(-1) at 300 °C in air. These composites can be used as high-temperature thermal insulators (in inert atmospheres or vacuum) or supports for phase change materials in thermal protection system.

  7. Thermal Insulation Composite Prepared from Carbon Foam and Silica Aerogel Under Ambient Pressure

    NASA Astrophysics Data System (ADS)

    Liu, Heguang; Li, Tiehu; Shi, Yachun; Zhao, Xing

    2015-10-01

    Carbon foam/silica aerogel composite as a promising thermal insulation material was prepared under ambient pressure successfully in the present work. Carbon foam was prepared by pretreatment, foaming, and carbonization process, while silica aerogel was synthesized by sol-gel method. The microstructure, morphology characteristics, compression strength, and thermal properties of composite were characterized by infrared spectroscopy, x-ray diffraction, scanning electron microscope, universal testing machine, and laser flash thermal detector, respectively. Results showed that silica aerogel was successfully synthesized in the surface foam cells of carbon foam due to the closed cell structure of carbon foam. Moreover, the compressive strength of the carbon foam was not affected by the silica aerogel in the cell structure of carbon foam, while its thermal insulation property at room temperature was improved.

  8. Hierarchical Nafion enhanced carbon aerogels for sensing applications.

    PubMed

    Weng, Bo; Ding, Ailing; Liu, Yuqing; Diao, Jianglin; Razal, Joselito; Lau, King Tong; Shepherd, Roderick; Li, Changming; Chen, Jun

    2016-02-14

    This work describes the fabrication of hierarchical 3D Nafion enhanced carbon aerogels (NECAGs) for sensing applications via a fast freeze drying method. Graphene oxide, multiwalled carbon nanotubes and Nafion were mixed and extruded into liquid nitrogen followed by the removal of ice crystals by freeze drying. The addition of Nafion enhanced the mechanical strength of NECAGs and effective control of the cellular morphology and pore size was achieved. The resultant NECAGs demonstrated high strength, low density, and high specific surface area and can achieve a modulus of 20 kPa, an electrical conductivity of 140 S m(-1), and a specific capacity of 136.8 F g(-1) after reduction. Therefore, NECAG monoliths performed well as a gas sensor and as a biosensor with high sensitivity and selectivity. The remarkable sensitivity of 8.52 × 10(3)μA mM(-1) cm(-2) was obtained in dopamine (DA) detection, which is two orders of magnitude better than the literature reported values using graphene aerogel electrodes made from a porous Ni template. These outstanding properties make the NECAG a promising electrode candidate for a wide range of applications. Further in-depth investigations are being undertaken to probe the structure-property relationship of NECAG monoliths prepared under various conditions. PMID:26791962

  9. Catalytic decomposition of 4-phenoxyphenol to aromatics over Pd/Cs(x)H3.0-x PW12O40/activated carbon aerogel (X = 2.0-3.0).

    PubMed

    Park, Hai Woong; Hong, Ung Gi; Lee, Yoon Jae; Choi, Jung Ho; Song, In Kyu

    2013-12-01

    Cesium-exchanged heteropolyacid (Cs(x)H3.0-xPW12O40) was impregnated onto activated carbon aerogel (ACA) with a variation of cesium content (X = 2.0, 2.3, 2.5, 2.7, and 3.0) in order to provide acid sites to ACA. Palladium catalysts were then supported on Cs(x)H3.0-xPW12O40-impregnated activated carbon aerogel (Pd/Cs(x)H3.0-xPW12O40/ACA, X = 2.0-3.0) by an incipient wetness impregnation method for use in the decomposition of lignin model compound to aromatics. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 linkage of lignin. In the catalytic decomposition of 4-phenoxyphenol over Pd/Cs(X)H3.0-xPW12O40/ACA, cyclohexanol, benzene, and phenol were mainly produced. Conversion of 4-phenoxyphenol and total yield for main products (cyclohexanol, benzene, and phenol) were closely related to the acidity of Pd/Cs(x)H3.0-xPW12O40/ACA. Conversion of 4-phenoxyphenol and total yield for main products increased with increasing acidity of Pd/Cs(x)H3.0-xPW12O40/ACA. Among the catalysts tested, Pd/Cs2.5H0.5PW12O40/ACA catalyst with the largest acidity showed the highest conversion of 4-phenoxyphenol and total yield for main products. Therefore, it is concluded that acidity of catalysts would be an important factor determining the catalytic performance in the decomposition of 4-phenoxyphenol. PMID:24266173

  10. Carbon XANES Data from Six Aerogel Picokeystones Cut from the Top and Bottom Sides of the Stardust Comet Sample Tray

    NASA Technical Reports Server (NTRS)

    Wirick, S.; Flynn, G. J.; Frank, D.; Sandford, S. A.; Zolensky, M. E.; Tsou, P.; Peltzer, C.; Jacobsen, C.

    2009-01-01

    Great care and a large effort was made to minimize the amount of organic matter contained within the flight aerogel used to collect Comet 81P/Wild 2 samples. Even so, by the very nature of the production process and silica aerogel s affinity for volatile organics keeping silica aerogel free from organics is a monumental task. Silica aerogel from three production batches was flown on the Stardust sample return mission. All 3 types had layered densities varying from 5mg/ml to 50 mg/ml where the densest aerogel was farthest away from the collection area. A 2 step gelation process was used to make the flight aerogel and organics used in this process were tetraethylorthosilicate, ethanol and acetonitrile. Both ammonium hydroxide and nitric acid were also used in the aerogel production process. The flight aerogel was baked at JPL at 300 C for 72 hours, most of the baking was done at atmosphere but twice a day the oven was pumped to 10 torr for hour [1]. After the aerogel was baked it was stored in a nitrogen purged cabinet until flight time. One aerogel cell was located in the SRC away from any sample collection area as a witness to possible contamination from out gassing of the space craft, re-entry gases and any other organic encounter. This aerogel was aerogel used in the interstellar collection sample tray and is the least dense of the 3 batches of aerogel flown. Organics found in the witness tile include organics containing Si-CH3 bonds, amines and PAHS. Besides organic contamination, hot spots of calcium were reported in the flight aerogel. Carbonates have been detected in comet 81P/Wild2 samples . During preflight analyses, no technique was used to analyze for carbonates in aerogel. To determine if the carbonates found in 81P/Wild2 samples were from the comet, it is necessary to analyze the flight aerogel for carbonate as well as for organics.

  11. Carbon nanotube spaced graphene aerogels with enhanced capacitance in aqueous and ionic liquid electrolytes

    NASA Astrophysics Data System (ADS)

    Shao, Qingguo; Tang, Jie; Lin, Yuexian; Li, Jing; Qin, Faxiang; Yuan, Jinshi; Qin, Lu-Chang

    2015-03-01

    Carbon nanotube spaced graphene aerogels have been prepared by a hydrothermal method and used for supercapacitor applications. The specific surface area and specific capacitance can be controlled by tuning the amount of added carbon nanotubes. The as-prepared composite aerogels retain the advantage of aerogel structure in providing macropores to ensure electrodes fast wetted by the electrolyte ions and also possess additional mesopores created by the carbon nanotube spacers for more ion adsorption. Benefited from that, the composite aerogels exhibit significantly enhanced supercapacitor properties in both aqueous and ionic liquid electrolyte. Compared with graphene aerogels, the composite aerogels show a 37% larger specific capacitance of 245.5 F g-1 at a current density of 2.5 A g-1 and high rate capability of 197.0 F g-1 at a high current density of 80 A g-1 in aqueous electrolyte. Moreover, the composite aerogels deliver a 33% larger specific capacitance of 183.3 F g-1 at 0.5 A g-1 and a high energy density of 80 Wh kg-1 when using an ionic liquid (EMIMBF4) as the electrolyte.

  12. Octahedral Tin Dioxide Nanocrystals Anchored on Vertically Aligned Carbon Aerogels as High Capacity Anode Materials for Lithium-Ion Batteries

    NASA Astrophysics Data System (ADS)

    Liu, Mingkai; Liu, Yuqing; Zhang, Yuting; Li, Yiliao; Zhang, Peng; Yan, Yan; Liu, Tianxi

    2016-08-01

    A novel binder-free graphene - carbon nanotubes - SnO2 (GCNT-SnO2) aerogel with vertically aligned pores was prepared via a simple and efficient directional freezing method. SnO2 octahedrons exposed of {221} high energy facets were uniformly distributed and tightly anchored on multidimensional graphene/carbon nanotube (GCNT) composites. Vertically aligned pores can effectively prevent the emersion of “closed” pores which cannot load the active SnO2 nanoparticles, further ensure quick immersion of electrolyte throughout the aerogel, and can largely shorten the transport distance between lithium ions and active sites of SnO2. Especially, excellent electrical conductivity of GCNT-SnO2 aerogel was achieved as a result of good interconnected networks of graphene and CNTs. Furthermore, meso- and macroporous structures with large surface area created by the vertically aligned pores can provide great benefit to the favorable transport kinetics for both lithium ion and electrons and afford sufficient space for volume expansion of SnO2. Due to the well-designed architecture of GCNT-SnO2 aerogel, a high specific capacity of 1190 mAh/g with good long-term cycling stability up to 1000 times was achieved. This work provides a promising strategy for preparing free-standing and binder-free active electrode materials with high performance for lithium ion batteries and other energy storage devices.

  13. Octahedral Tin Dioxide Nanocrystals Anchored on Vertically Aligned Carbon Aerogels as High Capacity Anode Materials for Lithium-Ion Batteries

    PubMed Central

    Liu, Mingkai; Liu, Yuqing; Zhang, Yuting; Li, Yiliao; Zhang, Peng; Yan, Yan; Liu, Tianxi

    2016-01-01

    A novel binder-free graphene - carbon nanotubes - SnO2 (GCNT-SnO2) aerogel with vertically aligned pores was prepared via a simple and efficient directional freezing method. SnO2 octahedrons exposed of {221} high energy facets were uniformly distributed and tightly anchored on multidimensional graphene/carbon nanotube (GCNT) composites. Vertically aligned pores can effectively prevent the emersion of “closed” pores which cannot load the active SnO2 nanoparticles, further ensure quick immersion of electrolyte throughout the aerogel, and can largely shorten the transport distance between lithium ions and active sites of SnO2. Especially, excellent electrical conductivity of GCNT-SnO2 aerogel was achieved as a result of good interconnected networks of graphene and CNTs. Furthermore, meso- and macroporous structures with large surface area created by the vertically aligned pores can provide great benefit to the favorable transport kinetics for both lithium ion and electrons and afford sufficient space for volume expansion of SnO2. Due to the well-designed architecture of GCNT-SnO2 aerogel, a high specific capacity of 1190 mAh/g with good long-term cycling stability up to 1000 times was achieved. This work provides a promising strategy for preparing free-standing and binder-free active electrode materials with high performance for lithium ion batteries and other energy storage devices. PMID:27510357

  14. Octahedral Tin Dioxide Nanocrystals Anchored on Vertically Aligned Carbon Aerogels as High Capacity Anode Materials for Lithium-Ion Batteries.

    PubMed

    Liu, Mingkai; Liu, Yuqing; Zhang, Yuting; Li, Yiliao; Zhang, Peng; Yan, Yan; Liu, Tianxi

    2016-01-01

    A novel binder-free graphene - carbon nanotubes - SnO2 (GCNT-SnO2) aerogel with vertically aligned pores was prepared via a simple and efficient directional freezing method. SnO2 octahedrons exposed of {221} high energy facets were uniformly distributed and tightly anchored on multidimensional graphene/carbon nanotube (GCNT) composites. Vertically aligned pores can effectively prevent the emersion of "closed" pores which cannot load the active SnO2 nanoparticles, further ensure quick immersion of electrolyte throughout the aerogel, and can largely shorten the transport distance between lithium ions and active sites of SnO2. Especially, excellent electrical conductivity of GCNT-SnO2 aerogel was achieved as a result of good interconnected networks of graphene and CNTs. Furthermore, meso- and macroporous structures with large surface area created by the vertically aligned pores can provide great benefit to the favorable transport kinetics for both lithium ion and electrons and afford sufficient space for volume expansion of SnO2. Due to the well-designed architecture of GCNT-SnO2 aerogel, a high specific capacity of 1190 mAh/g with good long-term cycling stability up to 1000 times was achieved. This work provides a promising strategy for preparing free-standing and binder-free active electrode materials with high performance for lithium ion batteries and other energy storage devices. PMID:27510357

  15. Carbon nanotube-bonded graphene hybrid aerogels and their application to water purification

    NASA Astrophysics Data System (ADS)

    Lee, Byeongho; Lee, Sangil; Lee, Minwoo; Jeong, Dae Hong; Baek, Youngbin; Yoon, Jeyong; Kim, Yong Hyup

    2015-04-01

    We present carbon nanotube (CNT)-bonded graphene hybrid aerogels that are prepared by growing CNTs on a graphene aerogel surface with nickel catalyst. The presence of bonded CNTs in the graphene aerogel results in vastly improved mechanical and electrical properties. A significant increase in specific surface area is also realized. The presence of the CNTs transforms the hybrid aerogels into a mesoporous material. The viscoelasticity of the hybrid aerogels is found to be invariant with respect to temperature over a range of between -150 °C and 450 °C. These characteristics along with the improved properties make the hybrid aerogels an entirely different class of material with applications in the fields of biotechnology and electrochemistry. The mesoporous nature of the material along with its high specific surface area also makes the hybrid aerogel attractive for application in water treatment. Both anionic and cationic dyes can be effectively removed from water by the hybrid aerogel. A number of organics and oils can be selectively separated from water by the hybrid aerogel. The hybrid aerogel is easy to handle and separate from water due to its magnetic nature, and can readily be recycled and reused.We present carbon nanotube (CNT)-bonded graphene hybrid aerogels that are prepared by growing CNTs on a graphene aerogel surface with nickel catalyst. The presence of bonded CNTs in the graphene aerogel results in vastly improved mechanical and electrical properties. A significant increase in specific surface area is also realized. The presence of the CNTs transforms the hybrid aerogels into a mesoporous material. The viscoelasticity of the hybrid aerogels is found to be invariant with respect to temperature over a range of between -150 °C and 450 °C. These characteristics along with the improved properties make the hybrid aerogels an entirely different class of material with applications in the fields of biotechnology and electrochemistry. The mesoporous nature

  16. Iron-Doped Carbon Aerogels: Novel Porous Substrates for Direct Growth of Carbon Nanotubes

    SciTech Connect

    Steiner, S A; Baumann, T F; Kong, J; Satcher, J H; Dresselhaus, M S

    2007-02-15

    We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K{sup +}-doped gels that can then be converted to Fe{sup 2+}- or Fe{sup 3+}-doped gels through an ion exchange process, dried with supercritical CO{sub 2} and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH{sub 4} (1000 sccm), H{sub 2} (500 sccm), and C{sub 2}H{sub 4} (20 sccm) at temperatures ranging from 600 to 800 C for 10 minutes, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled ({approx}25 nm in diameter and up to 4 mm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs were grown on Fe-doped CAs pyrolyzed at 800 C treated at CVD temperatures of 700 C.

  17. Iron-Doped Carbon Aerogels: Novel Porous Substrates for Direct Growth of Carbon Nanotubes

    DOE R&D Accomplishments Database

    Steiner, S. A.; Baumann, T. F.; Kong, J.; Satcher, J. H.; Dresselhaus, M. S.

    2007-02-20

    We present the synthesis and characterization of Fe-doped carbon aerogels (CAs) and demonstrate the ability to grow carbon nanotubes directly on monoliths of these materials to afford novel carbon aerogel-carbon nanotube composites. Preparation of the Fe-doped CAs begins with the sol-gel polymerization of the potassium salt of 2,4-dihydroxybenzoic acid with formaldehyde, affording K{sup +}-doped gels that can then be converted to Fe{sup 2+}- or Fe{sup 3+}-doped gels through an ion exchange process, dried with supercritical CO{sub 2} and subsequently carbonized under an inert atmosphere. Analysis of the Fe-doped CAs by TEM, XRD and XPS revealed that the doped iron species are reduced during carbonization to form metallic iron and iron carbide nanoparticles. The sizes and chemical composition of the reduced Fe species were related to pyrolysis temperature as well as the type of iron salt used in the ion exchange process. Raman spectroscopy and XRD analysis further reveal that, despite the presence of the Fe species, the CA framework is not significantly graphitized during pyrolysis. The Fe-doped CAs were subsequently placed in a thermal CVD reactor and exposed to a mixture of CH{sub 4} (1000 sccm), H{sub 2} (500 sccm), and C{sub 2}H{sub 4} (20 sccm) at temperatures ranging from 600 to 800 C for 10 minutes, resulting in direct growth of carbon nanotubes on the aerogel monoliths. Carbon nanotubes grown by this method appear to be multiwalled ({approx}25 nm in diameter and up to 4 mm long) and grow through a tip-growth mechanism that pushes catalytic iron particles out of the aerogel framework. The highest yield of CNTs were grown on Fe-doped CAs pyrolyzed at 800 C treated at CVD temperatures of 700 C.

  18. The hybrid nanostructure of MnCo2O4.5 nanoneedle/carbon aerogel for symmetric supercapacitors with high energy density.

    PubMed

    Hao, Pin; Zhao, Zhenhuan; Li, Liyi; Tuan, Chia-Chi; Li, Haidong; Sang, Yuanhua; Jiang, Huaidong; Wong, C P; Liu, Hong

    2015-09-14

    Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by calcination. The carbon aerogel exhibits a high electrical conductivity, high specific surface area and porous structure, ensuring high electrochemical performance of the hybrid nanostructure when coupled with the porous MnCo2O4.5 nanoneedles. The symmetric supercapacitor using the MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure as the active electrode material exhibits a high energy density of about 84.3 Wh kg(-1) at a power density of 600 W kg(-1). The voltage window is as high as 1.5 V in neutral aqueous electrolytes. Due to the unique nanostructure of the electrodes, the capacitance retention reaches 86% over 5000 cycles.

  19. Hierarchical porous carbon aerogel derived from bagasse for high performance supercapacitor electrode

    NASA Astrophysics Data System (ADS)

    Hao, Pin; Zhao, Zhenhuan; Tian, Jian; Li, Haidong; Sang, Yuanhua; Yu, Guangwei; Cai, Huaqiang; Liu, Hong; Wong, C. P.; Umar, Ahmad

    2014-09-01

    Renewable, cost-effective and eco-friendly electrode materials have attracted much attention in the energy conversion and storage fields. Bagasse, the waste product from sugarcane that mainly contains cellulose derivatives, can be a promising candidate to manufacture supercapacitor electrode materials. This study demonstrates the fabrication and characterization of highly porous carbon aerogels by using bagasse as a raw material. Macro and mesoporous carbon was first prepared by carbonizing the freeze-dried bagasse aerogel; consequently, microporous structure was created on the walls of the mesoporous carbon by chemical activation. Interestingly, it was observed that the specific surface area, the pore size and distribution of the hierarchical porous carbon were affected by the activation temperature. In order to evaluate the ability of the hierarchical porous carbon towards the supercapacitor electrode performance, solid state symmetric supercapacitors were assembled, and a comparable high specific capacitance of 142.1 F g-1 at a discharge current density of 0.5 A g-1 was demonstrated. The fabricated solid state supercapacitor displayed excellent capacitance retention of 93.9% over 5000 cycles. The high energy storage ability of the hierarchical porous carbon was attributed to the specially designed pore structures, i.e., co-existence of the micropores and mesopores. This research has demonstrated that utilization of sustainable biopolymers as the raw materials for high performance supercapacitor electrode materials is an effective way to fabricate low-cost energy storage devices.Renewable, cost-effective and eco-friendly electrode materials have attracted much attention in the energy conversion and storage fields. Bagasse, the waste product from sugarcane that mainly contains cellulose derivatives, can be a promising candidate to manufacture supercapacitor electrode materials. This study demonstrates the fabrication and characterization of highly porous carbon

  20. On the correlation between the porous structure and the electrochemical response of powdered and monolithic carbon aerogels as electrodes for capacitive deionization

    NASA Astrophysics Data System (ADS)

    Macías, C.; Lavela, P.; Rasines, G.; Zafra, M. C.; Tirado, J. L.; Ania, C. O.

    2016-10-01

    The combined effect of resorcinol/catalyst (100≤R/C≤800) and resorcinol/water (0.04≤R/W≤0.13) molar ratio on the textural and capacitive properties of carbon aerogels with potential application for capacitive deionization has been evaluated. Activated and pyrolyzed aerogels were synthesized by the sol-gel polymerization of resorcinol-formaldehyde mixtures and dried in supercritical conditions. Data show that high R/C and R/W molar ratios lead to materials with large pores in the mesopore range, whereas the surface area and micropore volumes remain somewhat the same. The activation of the aerogels increased the differences in the specific surface and micropore volumes due to the development of microporosity. This effect was more remarkable for the samples with low R/C whatever the R/W ratio, indicating that the carbon aerogel obtained using high amounts of catalyst are more prone to be activated. Regarding the electrochemical features of the aerogels, low capacitance values were measured in aerogels combining low R/W and high R/C and reciprocally low R/C and high R/W molar ratios, due to their higher resistance. Polarization resistances were found to be slightly higher for the pyrolyzed than for activated aerogels, and followed a decreasing trend with the mesoporosity, indicating the outstanding contribution of the mesoporous network to provide a good kinetic response. The desalting capacity of monolithic aerogels showed a simultaneous dependence with the surface area and the resistivity of the electrodes, pointing out the importance of performing electrochemical measurements in adequate cell configurations (i.e., desalting units) upon the intended application.

  1. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W.

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000 .ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  2. Organic carbon aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1998-04-28

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1000 {angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  3. SYNTHESIS AND CHARACTERIZATION OF CARBON AEROGEL NANOCOMPOSITES CONTAINING DOUBLE-WALLED CARBON NANOTUBES

    SciTech Connect

    Worsley, M A; Satcher, J H; Baumann, T F

    2008-03-11

    Carbon aerogels (CAs) are novel mesoporous materials with applications such as electrode materials for super capacitors and rechargeable batteries, adsorbents and advanced catalyst supports. To expand the potential application for these unique materials, recent efforts have focused on the design of CA composites with the goal of modifying the structure, conductivity or catalytic activity of the aerogel. Carbon nanotubes (CNTs) possess a number of intrinsic properties that make them promising materials in the design of composite materials. In addition, the large aspect ratios (100-1000) of CNTs means that small additions (less than 1 vol%) of CNTs can produce a composite with novel properties. Therefore, the homogeneous incorporation of CNTs into a CA matrix provides a viable route to new carbon-based composites with enhanced thermal, electrical and mechanical properties. One of the main challenges in preparing CNT composites is achieving a good uniform dispersion of nanotubes throughout the matrix. CAs are typically prepared through the sol-gel polymerization of resorcinol with formaldehyde in aqueous solution to produce organic gels that are supercritically dried and subsequently pyrolyzed in an inert atmosphere. Therefore, a significant issue in fabricating CA-CNT composites is dispersing the CNTs in the aqueous reaction media. Previous work in the design of CACNT composites have addressed this issue by using organic solvents in the sol-gel reaction to facilitate dispersion of the CNTs. To our knowledge, no data has been published involving the preparation of CA composites containing CNTs dispersed in aqueous media. In this report, we describe a new method for the synthesis of monolithic CA-CNT composites that involves the sol-gel polymerization of resorcinol and formaldehyde in an aqueous solution containing a surfactant-stabilized dispersion of double-walled carbon nanotubes (DWNT). One of the advantages of this approach is that it allows one to uniformly

  4. Carboxyl multiwalled carbon nanotubes modified polypyrrole (PPy) aerogel for enhanced electromagnetic absorption

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Xie, Aming; Wu, Fan; Jiang, Wanchun; Wang, Mingyang; Dong, Wei

    2016-05-01

    Polypyrrole (PPy) aerogel is a low-cost and lightweight material with high-performance electromagnetic absorption (EA). However, it does not always meet the requirements of practical applications. In this study, we used trace amounts of carboxyl multiwalled carbon nanotubes to regulate the dielectric property of PPy aerogel, thus enhancing the EA performance. Furthermore, the reason for enhanced EA performance can be elaborated by an electron blocking mechanism.

  5. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    DOEpatents

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H

    2014-04-01

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  6. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    DOEpatents

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr, Joe H.

    2016-07-05

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  7. Monolithic co-aerogels of carbon/titanium dioxide as three dimensional nanostructured electrodes for energy storage

    NASA Astrophysics Data System (ADS)

    Yang, Sungwoo; Cai, Yue; Cheng, Yingwen; Varanasi, C. V.; Liu, Jie

    2012-11-01

    Conductive fillers, such as amorphous carbon, carbon nanotube and graphene etc., are generally mixed with nanostructured metal oxide materials to improve the performance of electrode materials in energy storage devices. However, the conductive framework that provides path for electric conduction does not normally form a well-connected and robust 3-D network to ensure optimized ions transport. Here, we report a convenient, inexpensive and scalable method for synthesizing hybrid carbon and titanium dioxide co-gels and co-aerogels to improve the electrochemical capacity by combining both the lithium insertion and the surface storage mechanisms in Li ion batteries (LIBs) anodes. A monolithic piece of a hybrid C/TiO2 co-aerogel can be directly used as an active electrode without the addition of binders, such as polyvinylidene fluoride (PVDF). As a result, the performance of LIB anodes using the hybrid co-aerogel is significantly improved over current LIBs based on carbon/titanium oxide composites. The reversible discharge capacity was stabilized at ˜400 mAh g-1 at a 168 mA g-1 scan rate and an operating voltage between 3.0 and 0.05 V vs. Li+/Li with excellent cyclic capacity retention. This approach, however, is not limited to only C/TiO2 system but can be extended to other metal oxides to form co-gels with carbon to improve their potential use in numerous electrochemical, photocatalytic, and photoelectronic devices.

  8. Versatile fabrication of magnetic carbon fiber aerogel applied for bidirectional oil-water separation

    NASA Astrophysics Data System (ADS)

    Li, Yong; Zhu, Xiaotao; Ge, Bo; Men, Xuehu; Li, Peilong; Zhang, Zhaozhu

    2015-09-01

    Fabricating functional materials that can solve environmental problems resulting from oil or organic solvent pollution is highly desired. However, expensive materials or complicated procedures and unidirectional oil-water separation hamper their applications. Herein, a magnetic superhydrophobic carbon fiber aerogel with high absorption capacity was developed by one-step pyrolysis of Fe(NO3)3-coated cotton in an argon atmosphere. The obtained aerogel can selectively collect oils from oil-polluted region by a magnet bar owing to its magnetic properties and achieves fast oil-water separation for its superhydrophobicity and superoleophilicity. Furthermore, the aerogel performs recyclable oil absorption capacity even after ten cycles of oil-water separation and bears organic solvent immersion. Importantly, the obtained aerogel turns to superhydrophilic and underwater superoleophobic after thermal treatment, allowing it as a promising and efficient material for bidirectional oil-water separation and organic contaminants removal.

  9. Eutectic bonding of a Ti sputter coated, carbon aerogel wafer to a Ni foil

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; Kanna, R.L.

    1994-06-01

    The formation of high energy density, storage devices is achievable using composite material systems. Alternate layering of carbon aerogel wafers and Ni foils with rnicroporous separators is a prospective composite for capacitor applications. An inherent problem exists to form a physical bond between Ni and the porous carbon wafer. The bonding process must be limited to temperatures less than 1000{degrees}C, at which point the aerogel begins to degrade. The advantage of a low temperature eutectic in the Ni-Ti alloy system solves this problem. Ti, a carbide former, is readily adherent as a sputter deposited thin film onto the carbon wafer. A vacuum bonding process is then used to join the Ni foil and Ti coating through eutectic phase formation. The parameters required for successfld bonding are described along with a structural characterization of the Ni foil-carbon aerogel wafer interface.

  10. Surface modified aerogel monoliths

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas (Inventor); Johnston, James C. (Inventor); Kuczmarski, Maria A. (Inventor); Meador, Mary Ann B. (Inventor)

    2013-01-01

    This invention comprises reinforced aerogel monoliths such as silica aerogels having a polymer coating on its outer geometric surface boundary, and to the method of preparing said aerogel monoliths. The polymer coatings on the aerogel monoliths are derived from polymer precursors selected from the group consisting of isocyanates as a precursor, precursors of epoxies, and precursors of polyimides. The coated aerogel monoliths can be modified further by encapsulating the aerogel with the polymer precursor reinforced with fibers such as carbon or glass fibers to obtain mechanically reinforced composite encapsulated aerogel monoliths.

  11. Highly porous PEM fuel cell cathodes based on low density carbon aerogels as Pt-support: Experimental study of the mass-transport losses

    NASA Astrophysics Data System (ADS)

    Marie, Julien; Chenitz, Regis; Chatenet, Marian; Berthon-Fabry, Sandrine; Cornet, Nathalie; Achard, Patrick

    Carbon aerogels exhibiting high porous volumes and high surface areas, differentiated by their pore-size distributions were used as Pt-supports in the cathode catalytic layer of H 2/air-fed PEM fuel cell. The cathodes were tested as 50 cm 2 membrane electrode assemblies (MEAs). The porous structure of the synthesized catalytic layers was impacted by the nanostructure of the Pt-doped carbon aerogels (Pt/CAs). In this paper thus we present an experimental study aiming at establishing links between the porous structure of the cathode catalytic layers and the MEAs performances. For that purpose, the polarization curves of the MEAs were decomposed in 3 contributions: the kinetic loss, the ohmic loss and the mass-transport loss. We showed that the MEAs made with the different carbon aerogels had similar kinetic activities (low current density performance) but very different mass-transport voltage losses. It was found that the higher the pore-size of the initial carbon aerogel, the higher the mass-transport voltage losses. Supported by our porosimetry (N 2-adsorption and Hg-porosimetry) measurement, we interpret this apparent contradiction as the consequence of the more important Nafion penetration into the carbon aeorogel with larger pore-size. Indeed, the catalytic layers made from the larger pore-size carbon aerogel had lower porosities. We thus show in this work that carbon aerogels are materials with tailored nanostructured structure which can be used as model materials for experimentally testing the optimization of the PEM fuel cell catalytic layers.

  12. Carbon microbelt aerogel prepared by waste paper: an efficient and recyclable sorbent for oils and organic solvents.

    PubMed

    Bi, Hengchang; Huang, Xiao; Wu, Xing; Cao, Xiehong; Tan, Chaoliang; Yin, Zongyou; Lu, Xuehong; Sun, Litao; Zhang, Hua

    2014-09-10

    A carbon microbelt (CMB) aerogel with good selective sorption can be produced in large scale by using waste paper as a precursor. The CMB aerogel shows highly efficient sorption of organic liquids (pump oil: up to 188 times its own weight; chloroform: up to 151 times its own weight). Moreover, the CMB aerogel can be regenerated many times without decrease of sorption capacity by distillation, or squeezing depending on the type of pollutants.

  13. Desalting in wastewater reclamation using capacitive deionization with carbon aerogel electrodes

    SciTech Connect

    Richardson, J.H.; Farmer, J.C.; Fix, D.V.; de Pruneda, J.A.H.; Mack, G.V.; Poco, J.F.; Nielsen, J.K.; Pekala, R.W.

    1996-07-01

    Capacitive deionization with carbon aerogel electrodes is an efficient and economical new process for removing salt and impurities from water. Carbon aerogel is a material that enables the successful purification of water because of its high surface area, optimum pore size, and low electrical resistivity. The electrodes are maintained at a potential difference of about one volt; ions are removed from the water by the imposed electrostatic field and retained on the electrode surface until the polarity is reversed. The capacitive deionization of water with a stack of carbon aerogel electrodes has been successfully demonstrated. The overall process offers advantages when compared to conventional water-purification methods, requiring neither pumps, membranes, distillation columns, nor thermal heaters. Consequently, the overall process is both robust and energy efficient. The current state of technology development commercialization, and potential applications of this process are reviewed. Particular attention and comparison with alternate technologies will be done for seawater, brackish water, and desalting in wastewater reclamation.

  14. Always look on the "light" side of life: sustainable carbon aerogels.

    PubMed

    White, Robin J; Brun, Nicolas; Budarin, Vitaly L; Clark, James H; Titirici, Maria-Magdalena

    2014-03-01

    The production of carbon aerogels based on the conversion of inexpensive and abundant precursors using environmentally friendly processes is a highly attractive subject in materials chemistry today. This article reviews the latest developments regarding the rapidly developing field of carbonaceous aerogels prepared from biomass and biomass-derived precursors, highlighting exciting and innovative approaches to green, sustainable nanomaterial synthesis. A review of the state-of-the-art technologies will be provided with a specific focus on two complimentary synthetic approaches developed upon the principles of green chemistry. These carbonaceous aerogel synthesis strategies, namely the Starbon and carbogel approaches, can be regarded as "top-down" and "bottom-up" strategies, respectively. The structural properties can be easily tailored by controlling synthetic parameters such as the precursor selection and concentration, the drying technique employed and post-synthesis temperature annealing. In addition to these parameters, the behavior of these sustainable carbon aerogel platforms in a variety of environmental and energy-related applications will also be discussed, including water remediation and fuel cell chemistry (i.e., the oxygen reduction reaction). This Review reveals the fascinating variety of highly porous, versatile, nanostructured, and functional carbon-based aerogels accessible through the highlighted sustainable synthetic platforms.

  15. Treatment of brackish produced water using carbon aerogel-based capacitive deionization technology.

    PubMed

    Xu, Pei; Drewes, Jörg E; Heil, Dean; Wang, Gary

    2008-05-01

    Capacitive deionization (CDI) with carbon-aerogel electrodes represents a novel process in desalination of brackish water and has merit due to its low fouling/scaling potential, ambient operational conditions, electrostatic regeneration, and low voltage requirements. The objective of this study was to investigate the viability of CDI in treating brackish produced water and recovering iodide from the water. Laboratory- and pilot-scale experiments were conducted to identify ion selectivity, key operational parameters, evaluate desalination performance, and assess the challenges for its practical applications. The performance of the CDI technology (CDT) system tested was consistent throughout the laboratory- and field-scale experiments. Deterioration of the carbon-aerogel electrodes was not observed during testing. The degree of ions adsorbed to the carbon aerogel (in mol/g aerogel) during treatment of brackish water was dependent upon initial ion concentrations in the feed water with the following selectivity I>Br>Ca>alkalinity>Mg>Na>Cl. The preferential sorption of iodide revealed merit to efficiently recover iodide from brackish water even in the presence of dominant co-ions. The research findings derived from this study identified parameters that merit further improvements regarding design and operation, including modification of pore-size distribution of aerogel, development of high capacitance and low-cost electrode materials, reducing the dead volume after regeneration and rinsing, minimizing energy consumption, and maximizing system recovery.

  16. Ultralight carbon aerogel from nanocellulose as a highly selective oil absorption material

    DOE PAGES

    Meng, Yujie; Yang, Timothy M.; Liu, Peizhi; Contescu, Cristian I.; Huang, Biao; Wang, Siqun

    2014-12-04

    The synthesis of a sponge-like carbon aerogel from microfibril cellulose (MFC), with high porosity (99%), ultra-low density (0.01 g/cm3), hydrophobic properties (149° static contact angle) and reusability is reported in this paper. The physical properties, internal morphology, thermal properties, and chemical properties of carbon aerogels heat-treated at 700 and 900 °C (Samples C-700 and C-900) were examined. Stabilization and carbonization parameters were optimized in terms of residual carbon yield. The BET surface area of Sample C-700 (521 m2 /g) was significantly higher than of Sample C-950 (149 m2 /g). Graphitic-like domains were observed in C-950. The highest normalized sorption capacitymore » (86 g/g) for paraffin oil was observed in sample C-700. The removal of hydrophilic function groups during carbonization causes carbon aerogel to present highly hydrophobic properties. Lastly, carbon aerogel's ability to absorb oil is enhanced by its highly porous 3D network structure with interconnected cellulose nanofibrils.« less

  17. Ultralight carbon aerogel from nanocellulose as a highly selective oil absorption material

    SciTech Connect

    Meng, Yujie; Yang, Timothy M.; Liu, Peizhi; Contescu, Cristian I.; Huang, Biao; Wang, Siqun

    2014-12-04

    The synthesis of a sponge-like carbon aerogel from microfibril cellulose (MFC), with high porosity (99%), ultra-low density (0.01 g/cm3), hydrophobic properties (149° static contact angle) and reusability is reported in this paper. The physical properties, internal morphology, thermal properties, and chemical properties of carbon aerogels heat-treated at 700 and 900 °C (Samples C-700 and C-900) were examined. Stabilization and carbonization parameters were optimized in terms of residual carbon yield. The BET surface area of Sample C-700 (521 m2 /g) was significantly higher than of Sample C-950 (149 m2 /g). Graphitic-like domains were observed in C-950. The highest normalized sorption capacity (86 g/g) for paraffin oil was observed in sample C-700. The removal of hydrophilic function groups during carbonization causes carbon aerogel to present highly hydrophobic properties. Lastly, carbon aerogel's ability to absorb oil is enhanced by its highly porous 3D network structure with interconnected cellulose nanofibrils.

  18. Preparation, characterization, and activity of peptide-cellulosic aerogel protease sensor from cotton

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nanocellulosic aerogels (NA) provide a lightweight biocompatible material with structural properties of both high porosity and specific surface area for biosensor design. We report here the preparation, characterization, and activity of a peptide-nanocellulose aerogel (PA) made from unprocessed cot...

  19. Graphene coating makes carbon nanotube aerogels superelastic and resistant to fatigue.

    PubMed

    Kim, Kyu Hun; Oh, Youngseok; Islam, M F

    2012-09-01

    Lightweight materials that are both highly compressible and resilient under large cyclic strains can be used in a variety of applications. Carbon nanotubes offer a combination of elasticity, mechanical resilience and low density, and these properties have been exploited in nanotube-based foams and aerogels. However, all nanotube-based foams and aerogels developed so far undergo structural collapse or significant plastic deformation with a reduction in compressive strength when they are subjected to cyclic strain. Here, we show that an inelastic aerogel made of single-walled carbon nanotubes can be transformed into a superelastic material by coating it with between one and five layers of graphene nanoplates. The graphene-coated aerogel exhibits no change in mechanical properties after more than 1 × 10(6) compressive cycles, and its original shape can be recovered quickly after compression release. Moreover, the coating does not affect the structural integrity of the nanotubes or the compressibility and porosity of the nanotube network. The coating also increases Young's modulus and energy storage modulus by a factor of ∼6, and the loss modulus by a factor of ∼3. We attribute the superelasticity and complete fatigue resistance to the graphene coating strengthening the existing crosslinking points or 'nodes' in the aerogel. PMID:22820743

  20. Ultralow loading Pt nanocatalysts prepared by atomic layer deposition on carbon aerogels.

    PubMed

    King, Jeffrey S; Wittstock, Arne; Biener, Juergen; Kucheyev, Sergei O; Wang, Yinmin M; Baumann, Theodore F; Giri, Sandeep K; Hamza, Alex V; Baeumer, Marcus; Bent, Stacey F

    2008-08-01

    Using atomic layer deposition (ALD), we show that Pt nanoparticles can be deposited on the inner surfaces of carbon aerogels (CA). The resultant Pt-loaded materials exhibit high catalytic activity for the oxidation of CO even at loading levels as low as approximately 0.05 mg Pt/cm2. We observe a conversion efficiency of nearly 100% in the 150-250 degrees C temperatures range, and the total conversion rate seems to be limited only by the thermal stability of the CA support in ambient oxygen. The ALD approach described here is universal in nature, and can be applied to the design of new catalytic materials for a variety of applications, including fuel cells, hydrogen storage, pollution control, green chemistry, and liquid fuel production.

  1. Enhanced photocatalytic activity of TiO2-C hybrid aerogels for methylene blue degradation

    PubMed Central

    Shao, Xia; Lu, Wencong; Zhang, Rui; Pan, Feng

    2013-01-01

    Carbon-based TiO2 composites have many advantages as photocatalysts. However, they suffer from low light efficiency due to the low contrast of TiO2 with carbon. We synthesized a novel type of anatase-type TiO2-C hybrid aerogel by a one-pot sol-gel method, which shows a photocatalytic activity for methylene degradation up to 4.23 times that of P25, a commercial photocatalyst from Degussa Inc. The hybrid aerogels are prepared from TiCl4 and resorcinol–furfural, and have a tunable macropore size from 167 to 996 nm. They are formed of submicrometer particles that consist of interwoven anatase and carbon nanoparticles. The anatase nanoparticles have a size of 8–9 nm and a tunable oxygen vacancy from 7.2 to 18.0%. The extremely high activity is ascribed to the large light absorption caused by macropore scattering and oxygen vacancies in the anatase. These findings may open up a new avenue and stimulate further research to improve photocatalytic performance. PMID:24145581

  2. Enhanced photocatalytic activity of TiO2-C hybrid aerogels for methylene blue degradation

    NASA Astrophysics Data System (ADS)

    Shao, Xia; Lu, Wencong; Zhang, Rui; Pan, Feng

    2013-10-01

    Carbon-based TiO2 composites have many advantages as photocatalysts. However, they suffer from low light efficiency due to the low contrast of TiO2 with carbon. We synthesized a novel type of anatase-type TiO2-C hybrid aerogel by a one-pot sol-gel method, which shows a photocatalytic activity for methylene degradation up to 4.23 times that of P25, a commercial photocatalyst from Degussa Inc. The hybrid aerogels are prepared from TiCl4 and resorcinol-furfural, and have a tunable macropore size from 167 to 996 nm. They are formed of submicrometer particles that consist of interwoven anatase and carbon nanoparticles. The anatase nanoparticles have a size of 8-9 nm and a tunable oxygen vacancy from 7.2 to 18.0%. The extremely high activity is ascribed to the large light absorption caused by macropore scattering and oxygen vacancies in the anatase. These findings may open up a new avenue and stimulate further research to improve photocatalytic performance.

  3. The use of carbon aerogel electrodes for deionizing water and treating aqueous process wastes

    SciTech Connect

    Farmer, J.C.; Mack, G.V.; Fix, D.V.

    1996-07-01

    A wide variety of ionic contaminants can be removed from aqueous solutions by electrosorption on carbon aerogel electrodes. Carbon aerogel is an ideal electrode material because of its low electrical resistivity (< 40 m{Omega}-cm), high specific surface area (400 to 1100 m{sup 2}/g), and controllable pore size distribution (< 50 nm). This approach may avoid the generation of a substantial amount of secondary waste associated with ion exchange processing. Ion exchange resins require concentrated solutions of acid, base, or salt for regeneration, whereas carbon aerogel electrodes require only electrical discharge or reverse polarization. Aqueous solutions of NaCl, NaNO{sub 3}, NH{sub 4}ClO{sub 4}, Na{sub 2}CO{sub 3}, Na{sub 2}SO{sub 4} and Na{sub 3}PO{sub 4} have been separated into concentrate and high-purity product streams. The deionization of a 100 {mu}S/cm NaCl solution with two parallel stacks of carbon aerogel electrodes in a potential-swing mode is discussed in detail. The selective removal of Cu, Zn, Cd, Pb, Cr, Mn, Co and U from a variety of process solutions and natural waters has also been demonstrated. Feasibility tests indicate that the remediation of Cr(VI)-contaminated ground water may be possible.

  4. Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide

    PubMed Central

    Longo, Simona; Mauro, Marco; Daniel, Christophe; Galimberti, Maurizio; Guerra, Gaetano

    2013-01-01

    Supercritical carbon dioxide (scCO2) treatments of a montmorillonite (MMT) intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT) led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline δ form of syndiotactic polystyrene (s-PS), have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersion of the clay layers, higher elastic modulus and larger surface area than aerogels with the intercalated OMMT. Extremely light materials with relevant transport properties could be prepared. Moreover, s-PS-based aerogels with exfoliated OMMT could be helpful for the handling of exfoliated clay minerals. PMID:24790956

  5. The hybrid nanostructure of MnCo2O4.5 nanoneedle/carbon aerogel for symmetric supercapacitors with high energy density

    NASA Astrophysics Data System (ADS)

    Hao, Pin; Zhao, Zhenhuan; Li, Liyi; Tuan, Chia-Chi; Li, Haidong; Sang, Yuanhua; Jiang, Huaidong; Wong, C. P.; Liu, Hong

    2015-08-01

    Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by calcination. The carbon aerogel exhibits a high electrical conductivity, high specific surface area and porous structure, ensuring high electrochemical performance of the hybrid nanostructure when coupled with the porous MnCo2O4.5 nanoneedles. The symmetric supercapacitor using the MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure as the active electrode material exhibits a high energy density of about 84.3 Wh kg-1 at a power density of 600 W kg-1. The voltage window is as high as 1.5 V in neutral aqueous electrolytes. Due to the unique nanostructure of the electrodes, the capacitance retention reaches 86% over 5000 cycles.Current applications of carbon-based supercapacitors are limited by their low energy density. One promising strategy to enhance the energy density is to couple metal oxides with carbon materials. In this study, a porous MnCo2O4.5 nanoneedle/carbon aerogel hybrid nanostructure was synthesized by assembling MnCo2O4.5 nanoneedle arrays on the surface of channel walls of hierarchical porous carbon aerogels derived from chitosan for the supercapacitor application. The synthetic process of the hybrid nanostructure involves two steps, i.e. the growth of Mn-Co precursors on carbon aerogel by a hydrothermal process and the conversion of the precursor into MnCo2O4.5 nanoneedles by

  6. Carbon nanofiber aerogels for emergent cleanup of oil spillage and chemical leakage under harsh conditions

    PubMed Central

    Wu, Zhen-Yu; Li, Chao; Liang, Hai-Wei; Zhang, Yu-Ning; Wang, Xin; Chen, Jia-Fu; Yu, Shu-Hong

    2014-01-01

    To address oil spillage and chemical leakage accidents, the development of efficient sorbent materials is of global importance for environment and water source protection. Here we report on a new type of carbon nanofiber (CNF) aerogels as efficient sorbents for oil uptake with high sorption capacity and excellent recyclability. Importantly, the oil uptake ability of the CNF aerogels can be maintained over a wide temperature range, from liquid nitrogen temperature up to ca. 400°C, making them suitable for oil cleanup under harsh conditions. The outstanding sorption performance of CNF aerogels is associated with their unique physical properties, such as low density, high porosity, excellent mechanical stability, high hydrophobicity and superoleophilicity. PMID:24518262

  7. Effect of carbon dioxide and nitrogen on the diffusivity of methane confined in nano-porous carbon aerogel

    SciTech Connect

    Mavila Chathoth, Suresh; He, Lilin; Mamontov, Eugene; Melnichenko, Yuri B

    2012-01-01

    The microscopic diffusivity of methane (CH{sub 4}) confined in nano-porous carbon aerogel was investigated as a function of added carbon dioxide (CO{sub 2}) and nitrogen (N{sub 2}) pressure using quasi-elastic neutron scattering (QENS). In the range of the external pressure of 1-2.5 MPa, the self-diffusivity of methane was found to increase with CO{sub 2} pressure and remain practically unchanged in the N{sub 2} environment. Increasing mobility of methane with CO{sub 2} pressure suggests that the adsorbed CH4 molecules become gradually replaced by CO{sub 2} on the surface of carbon aerogel pores, whereas the presence of N{sub 2} does not induce the replacement. The molecular mobility of the methane, with or without added carbon dioxide and nitrogen, is described by the unrestricted diffusion model, which is characteristic of methane compressed in small pores. On the other hand, both nitrogen and carbon dioxide molecules in carbon aerogel, when studied alone, with no methane present, follow a jump diffusion process, characteristic of the molecular mobility in the densified adsorbed layers on the surface of the aerogel pores.

  8. Advanced Multifunctional Properties of Aligned Carbon Nanotube-Epoxy Composites from Carbon Nanotube Aerogel Method

    NASA Astrophysics Data System (ADS)

    Tran, Thang; Liu, Peng; Fan, Zeng; Ngern, Nigel; Duong, Hai

    2015-03-01

    Unlike previous methods of making carbon nanotube (CNT) thin films, aligned CNT thin films in this work are synthesized directly from CNT aerogels in a CVD process. CH4/H2/He gases and ferrocene/thiophene catalysts are mixed and reacted in the reactor at 1200 °C to form CNT aerogel socks. By pulling out the socks with a metal rod, CNT thin films with 15-nm diameter MWNTs are aligned and produced continuously at a speed of a few meters per minute. The number of the aligned CNT thin film layers/ thickness can also be controlled well. The as-synthesized aligned CNT films are further condensed by acetone spray and post-treated by UV light. The aligned CNT films without any above post-treatment have a high electrical conductivity of 400S/cm. We also develop aligned CNT-epoxy composites by infiltrating epoxy into the above aligned CNT thin films using Vacuum Assisted Resin Transfer Molding (VARTM) method. Our cost-effective fabrication method of the aligned CNT films is more advanced for developing the composites having CNT orientation control. The mechanical, electrical and optical properties of the aligned CNT epoxy composites are measured. About 2% of the aligned CNTs can enhance significantly the electrical conductivity and hardness of aligned CNT-epoxy composite films. Effects of morphologies, volume fraction, and alignment of the CNTs on the advanced multifunctional properties of the aligned CNT-epoxy composites are also quantified.

  9. Textural and mechanical characteristics of carbon aerogels synthesized by polymerization of resorcinol and formaldehyde using alkali carbonates as basification agents.

    PubMed

    Morales-Torres, Sergio; Maldonado-Hódar, Francisco José; Pérez-Cadenas, Agustín Francisco; Carrasco-Marín, Francisco

    2010-09-21

    Five organic aerogels were prepared simultaneously by polycondensation of resorcinol and formaldehyde using different alkali carbonates (M(2)CO(3), M = Li, Na, K, Rb and Cs) as basification agents. The gelation time depended on the carbonate used, increasing from Li(2)CO(3) to Cs(2)CO(3). The porosity of the samples is defined during this process, when the three-dimensional packing of primary particles is formed. The slower the gelation, the greater the overlapping of primary particles and the formation of clusters, leading to a mechanical reinforcement of the samples and the progressive displacement of their pore size distribution (PSD) towards larger pores. Carbonization produces certain shrinkage of the structure and increases the microporosity and the Young modulus of the samples. Carbon aerogels change from mesoporous to macroporous materials as the counter-ion size of the carbonate increases.

  10. Aerogel sorbents

    DOEpatents

    Begag, Redouane; Rhine, Wendell E; Dong, Wenting

    2016-04-05

    The current invention describes methods and compositions of various sorbents based on aerogels of various silanes and their use as sorbent for carbon dioxide. Methods further provide for optimizing the compositions to increase the stability of the sorbents for prolonged use as carbon dioxide capture matrices.

  11. Method for producing hydrophobic aerogels

    DOEpatents

    Hrubesh, Lawrence W.; Poco, John F.; Coronado, Paul R.

    1999-01-01

    A method for treating a dried monolithic aerogel containing non-dispersed particles, with an organometallic surface modifying agent to produce hydrophobic aerogels. The dried, porous hydrophobic aerogels contain a protective layer of alkyl groups, such as methyl groups, on the modified surfaces of the pores of the aerogel. The alkyl groups at the aerogel surface typically contain at least one carbon-metal bond per group.

  12. Three-Dimensional Macroassembly of Sandwich-Like, Hierarchical, Porous Carbon/Graphene Nanosheets towards Ultralight, Superhigh Surface Area, Multifunctional Aerogels.

    PubMed

    Zhu, Jiayi; Yang, Xi; Fu, Zhibing; He, Junhui; Wang, Chaoyang; Wu, Weidong; Zhang, Lin

    2016-02-12

    A new, ultralight, superhigh surface area, multifunctional aerogel, which is macroassembled from sandwich-like, hierarchical, porous carbon/graphene nanosheets, is described. The multifunctional aerogel was characterized by means of XRD, SEM, TEM, Raman spectroscopy, and UV/Vis absorption spectroscopy. The multifunctional aerogel had an ultralow density of 8 mg cm(-3) and a superhigh surface area of 2650 m(2)  g(-1) . The multifunctional aerogel was thermal stability and compressible. Meanwhile, the multifunctional aerogel exhibited high capacity for the adsorption of oils and organic solvents, unexpectedly high hydrogen adsorption and good electrochemical performance. PMID:26752085

  13. Biomolecular adsorption behavior on spherical carbon aerogels with various mesopore sizes.

    PubMed

    Long, Donghui; Zhang, Rui; Qiao, Wenming; Zhang, Liang; Liang, Xiaoyi; Ling, Licheng

    2009-03-01

    Spherical carbon aerogels (SCAs) with controlled particle size and mesopore size were synthesized by an emulsified sol-gel polymerization of phenol, melamine and formaldehyde. The adsorption rate and capacity of biomolecules with different molecular dimensions, including L-phenylalanine (Phe), vitamin B(12) (VB), alpha-chymotrypsin (Chy) and bovine serum albumin (BSA) onto SCAs were investigated. The mesopore size can be easily tuned in the range from 5 to 10 nm by simply adjusting catalyst concentration in the initial solution and the spherical particle size can be controlled in 50-500 microm by changing stirring speed. The as-prepared SCAs have high specific surface area (>600 m(2)/g) and large pore volume (>1 cm(3)/g). The hardness of SCAs is ca. 10 times as large as that of commercial spherical activated carbon particles. The adsorption rate of VB is strongly depended on the mesopore size and particle size, and show an increasing tread with the increase of mesopore size and the decrease of particle size. For small molecule Phe, the specific surface area is key factor to determine the adsorption capacity, but the adsorption capacity of large molecules (VB, Chy and BSA) is dependent on the pore size of SCAs, which should be suitably larger than the molecule size of biomolecules.

  14. Superhydrophobic functionalized graphene aerogels.

    PubMed

    Lin, Yirong; Ehlert, Gregory J; Bukowsky, Colton; Sodano, Henry A

    2011-07-01

    Carbon-based nanomaterials such as carbon nanotubes and graphene are excellent candidates for superhydrophobic surfaces because of their intrinsically high surface area and nonpolar carbon structure. This paper demonstrates that graphene aerogels with a silane surface modification can provide superhydrophobicity. Graphene aerogels of various concentrations were synthesized and the receding contact angle of a water droplet was measured. It is shown that graphene aerogels are hydrophobic and become superhydrophobic following the application of a fluorinated surfactant. The aerogels produced for this experiment outperform previous carbon nanomaterials in creating superhydrophobic surfaces and offer a more scalable synthetic procedure for production.

  15. Novel antimony doped tin oxide/carbon aerogel as efficient electrocatalytic filtration membrane

    NASA Astrophysics Data System (ADS)

    Liu, Zhimeng; Zhu, Mengfu; Wang, Zheng; Wang, Hong; Deng, Cheng; Li, Kui

    2016-05-01

    A facile method was developed to prepare antimony doped tin oxide (Sb-SnO2)/carbon aerogel (CA) for use as an electrocatalytic filtration membrane. The preparation process included synthesis of a precursor sol, impregnation, and thermal decomposition. The Sb-SnO2, which was tetragonal in phase with an average crystallite size of 10.8 nm, was uniformly distributed on the CA surface and firmly attached via carbon-oxygen-tin chemical bonds. Preliminary filtration tests indicated that the Sb-SnO2/CA membrane had a high rate of total organic carbon removal for aqueous tetracycline owing to its high current efficiency and electrode stability.

  16. Multifunctional structural supercapacitor composites based on carbon aerogel modified high performance carbon fiber fabric.

    PubMed

    Qian, Hui; Kucernak, Anthony R; Greenhalgh, Emile S; Bismarck, Alexander; Shaffer, Milo S P

    2013-07-10

    A novel multifunctional material has been designed to provide excellent mechanical properties while possessing a high electrochemical surface area suitable for electrochemical energy storage: structural carbon fiber fabrics are embedded in a continuous network of carbon aerogel (CAG) to form a coherent but porous monolith. The CAG-modification process was found to be scalable and to be compatible with a range of carbon fiber fabrics with different surface properties. The incorporation of CAG significantly increased the surface area of carbon fiber fabrics, and hence the electrochemical performance, by around 100-fold, resulting in a CAG-normalized specific electrode capacitance of around 62 F g(-1), determined by cyclic voltammetry in an aqueous electrolyte. Using an ionic liquid (IL) electrolyte, the estimated energy density increased from 0.003 to 1 Wh kg(-1), after introducing the CAG into the carbon fiber fabric. 'Proof-of-concept' multifunctional structural supercapacitor devices were fabricated using an IL-modified solid-state polymer electrolyte as a multifunctional matrix to provide both ionic transport and physical support for the primary fibers. Two CAG-impregnated carbon fabrics were sandwiched around an insulating separator to form a functioning structural electrochemical double layer capacitor composite. The CAG-modification not only improved the electrochemical surface area, but also reinforced the polymer matrix surrounding the primary fibers, leading to dramatic improvements in the matrix-dominated composite properties. Increases in in-plane shear strength and modulus, of up to 4.5-fold, were observed, demonstrating that CAG-modified structural carbon fiber fabrics have promise in both pure structural and multifunctional energy storage applications.

  17. High rate capacitive performance of single-walled carbon nanotube aerogels

    DOE PAGES

    Van Aken, Katherine L.; Pérez, Carlos R.; Oh, Youngseok; Beidaghi, Majid; Joo Jeong, Yeon; Islam, Mohammad F.; Gogotsi, Yury

    2015-05-30

    Single-walled carbon nanotube (SWCNT) aerogels produced by critical-point-drying of wet-gel precursors exhibit unique properties, such as high surface-area-to-volume and strength-to-weight ratios. They are free-standing, are binder-free, and can be scaled to thicknesses of more than 1 mm. In this paper, we examine the electric double layer capacitive behavior of these materials using a common room temperature ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI). Electrochemical performance is assessed through galvanostatic cycling, cyclic voltammetry and impedance spectroscopy. Results indicate stable capacitive performance over 10,000 cycles as well as an impressive performance at high charge and discharge rates, due to accessible pore networks andmore » enhanced electronic and ionic conductivities of SWCNT aerogels. Finally, these materials can find applications in mechanically compressible and flexible supercapacitor devices with high power requirements.« less

  18. High rate capacitive performance of single-walled carbon nanotube aerogels

    SciTech Connect

    Van Aken, Katherine L.; Pérez, Carlos R.; Oh, Youngseok; Beidaghi, Majid; Joo Jeong, Yeon; Islam, Mohammad F.; Gogotsi, Yury

    2015-05-30

    Single-walled carbon nanotube (SWCNT) aerogels produced by critical-point-drying of wet-gel precursors exhibit unique properties, such as high surface-area-to-volume and strength-to-weight ratios. They are free-standing, are binder-free, and can be scaled to thicknesses of more than 1 mm. In this paper, we examine the electric double layer capacitive behavior of these materials using a common room temperature ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMI-TFSI). Electrochemical performance is assessed through galvanostatic cycling, cyclic voltammetry and impedance spectroscopy. Results indicate stable capacitive performance over 10,000 cycles as well as an impressive performance at high charge and discharge rates, due to accessible pore networks and enhanced electronic and ionic conductivities of SWCNT aerogels. Finally, these materials can find applications in mechanically compressible and flexible supercapacitor devices with high power requirements.

  19. The use of capacitive deionization with carbon aerogel electrodes to remove inorganic contaminants from water

    SciTech Connect

    Farmer, J.C.; Fix, D.V.; Mack, G.V.; Pekala, R.W.; Poco, J.F.

    1995-02-17

    The capacitive deionization of water with a stack of carbon aerogel electrodes has been successfully demonstrated for the first time. Unlike ion exchange, one of the more conventional deionization processes, no chemicals were required for regeneration of the system. Electricity was used instead. Water with various anions and cations was pumped through the electrochemical cell. After polarization, ions were electrostatically removed from the water and held in the electric double layers formed at electrode surfaces. The water leaving the cell was purified, as desired.

  20. A dual pore carbon aerogel based air cathode for a highly rechargeable lithium-air battery

    NASA Astrophysics Data System (ADS)

    Wang, Fang; Xu, Yang-Hai; Luo, Zhong-Kuan; Pang, Yan; Wu, Qi-Xing; Liang, Chun-Sheng; Chen, Jing; Liu, Dong; Zhang, Xiang-hua

    2014-12-01

    Cathode structure plays a vital role in lithium-air battery for that it can provide space for discharged products accommodation and free path for oxygen, e- and Li+ transport. However, pore blockage, cathode passivation and degradation all result in low discharge rates and poor cycling capability. To get rid of these predicaments, a novel highly conductive dual pore carbon aerogel based air cathode is fabricated to construct a lithium-air battery, which exhibits 18 to 525 cycles in the LiTFSI/sulfolane electrolyte at a current density varying from 1.00 mA cm-2 to 0.05 mA cm-2, accompanied by a high energy efficiency of 78.32%. We postulate that the essence lies in that the as-prepared air cathode inventively create a suitable tri-phase boundary reaction zone, facilitating oxygen and Li+ diffusion in two independant pore channels, thus realizing a relative higher discharge rate capability, lower pore blockage and cathode passivation. Further, pore structure, carbon loading, rate capability, discharge depth and the air's effect are exploited and coordinated, targeting for a high power and reversible lithium-air battery. Such nano-porous carbon aerogel air cathode of novel dual pore structure and material design is expected to be an attractive alternative for lithium-air batteries and other lithium based batteries.

  1. Preparation, structural properties, and hydrogenation activity of highly porous palladium-titania aerogels

    SciTech Connect

    Schneider, M.; Wildberger, M.; Maciejewski, M.; Duff, D.G.; Mallat, T.; Baiker, A. )

    1994-08-01

    Mesoporous to macroporous palladium-titania aerogels with high surface area have been synthesized by the sol-gel-aerogel route. A titania gel was prepared by the addition of an acidic hydrolysant to tetrabutoxytitanium(IV) in methanol. The palladium precursor solutions, added after the redispersion of the titania gel, were either Na[sub 2]PdCl[sub 4], (NH[sub 4])[sub 2]PdCl[sub 4], Pd(acac)[sub 2], or Pd(OAc)[sub 2] dissolved in protic or aprotic solvents. The palladium-titania aerogels have a BET surface area of 170-190 m[sup 2]g[sup [minus]1] after a thermal treatment up to 673 K and contain well-developed anatase crystallites of about 7-8 nm mean size. Depending on the palladium precursor used, the volume-weighted-mean particle size, determined by TEM, varies significantly in the range 21-224 nm, this being independently consistent with XRD line-broadening results. All aerogel samples showed pronounced structural stability of both the titania matrix and the palladium particles towards the pretreatment media used (air or hydrogen) at temperatures up to 773 K. Thermal analysis, combined with mass spectrometry, revealed that the untreated catalysts contain a considerable amount of entrapped organic impurities after high-temperature supercritical drying. Liquid-phase hydrogenations of tras-stilbene and benzophenone were used as test reactions for characterizing the activity and accessibility of the palladium particles. A comparison of the best dispersed Pd(OAc)[sub 2]-derived aerogel catalysts with conventionally impregnated titania-supported palladium catalysts in the liquid-phase hydrogenation of 4-methylbenzaldehyde reveals superior activity and selectivity for the aerogel catalysts. 32 refs., 10 figs., 4 tabs.

  2. Elastic nonlinearity of aerogels

    NASA Astrophysics Data System (ADS)

    Gross, J.; Fricke, J.; Pekala, R. W.; Hrubesh, L. W.

    1992-06-01

    We have investigated the sound propagation in SiO2 aerogels and three types of organic aerogels: resorcinol formaldehyde, melamine formaldehyde, and vitreous carbon. The main parameter determining the sound velocity is the aerogel density; however, the bond strength and cross linking also influence the stiffness of these materials. Furthermore, we show that at least two types of low-density aerogels become less stiff and consequently the sound velocity is lowered when the specimens are uniaxially compressed. We explain this in terms of a model for the internal structure.

  3. Graphene-containing carbon aerogel prepared using polyethyleneimine (PEl)-modified graphene oxide (GO) for supercapacitor: effect of polyethyleneimine-modified GO content.

    PubMed

    Lee, Yoon Jae; Lee, Joongwon; Kim, Gil-Pyo; Lee, Eo Jin; Yi, Jongheop; Song, In Kyu

    2014-11-01

    Graphene-containing carbon aerogel was prepared by a sol-gel polymerization of resorcinol-formaldehyde (RF) method using polyethyleneimine (PEL)-modified chemically exfoliated graphene oxide (GO), and its electrochemical performance as an electrode for supercapacitor was examined. The effect of PEI-modified GO content on the physicochemical and electrochemical properties of graphene-containing carbon aerogel was investigated. For comparison, graphene-free carbon aerogel was also prepared. Among the samples, graphene-containing carbon aerogel prepared using 45 wt% PEI-modified GO solution (CA(45PG)) showed the highest BET surface area (784 m2/g) and the largest pore volume (1.71 cm3/g) with well-developed porous structure. Electrochemical properties of graphene-containing carbon aerogel and graphene-free carbon aerogel electrodes were measured by cyclic voltammetry, charge/discharge test, and electrochemical impedance spectroscopy in 6 M KOH electrolyte. Various electrochemical measurements revealed that CA(45PG) showed the highest specific capacitance (261 F/g), the lowest equivalent series resistance (0.16 Ω), and superior capacitive behavior. It is concluded that PEI-modified GO content served as an important factor determining the physicochemical properties and supercapacitive electrochemical performance of graphene-containing carbon aerogel.

  4. Polyolefin-Based Aerogels

    NASA Technical Reports Server (NTRS)

    Lee, Je Kyun; Gould, George

    2012-01-01

    An organic polybutadiene (PB) rubberbased aerogel insulation material was developed that will provide superior thermal insulation and inherent radiation protection, exhibiting the flexibility, resiliency, toughness, and durability typical of the parent polymer, yet with the low density and superior insulation properties associated with the aerogels. The rubbery behaviors of the PB rubber-based aerogels are able to overcome the weak and brittle nature of conventional inorganic and organic aerogel insulation materials. Additionally, with higher content of hydrogen in their structure, the PB rubber aerogels will also provide inherently better radiation protection than those of inorganic and carbon aerogels. Since PB rubber aerogels also exhibit good hydrophobicity due to their hydrocarbon molecular structure, they will provide better performance reliability and durability as well as simpler, more economic, and environmentally friendly production over the conventional silica or other inorganic-based aerogels, which require chemical treatment to make them hydrophobic. Inorganic aerogels such as silica aerogels demonstrate many unusual and useful properties. There are several strategies to overcoming the drawbacks associated with the weakness and brittleness of silica aerogels. Development of the flexible fiber-reinforced silica aerogel composite blanket has proven one promising approach, providing a conveniently fielded form factor that is relatively robust toward handling in industrial environments compared to silica aerogel monoliths. However, the flexible silica aerogel composites still have a brittle, dusty character that may be undesirable, or even intolerable, in certain applications. Although the cross-linked organic aerogels such as resorcinol-formaldehyde (RF), polyisocyanurate, and cellulose aerogels show very high impact strength, they are also very brittle with little elongation (i.e., less rubbery). Also, silica and carbon aerogels are less efficient

  5. Aerogel nanocomposite materials

    SciTech Connect

    Hunt, A.J.; Ayers, M.; Cao, W.

    1995-05-01

    Aerogels are porous, low density, nanostructured solids with many unusual properties including very low thermal conductivity, good transparency, high surface area, catalytic activity, and low sound velocity. This research is directed toward developing new nanocomposite aerogel materials for improved thermal insulation and several other applications. A major focus of the research has been to further increase the thermal resistance of silica aerogel by introducing infrared opacification agents into the aerogel to produce a superinsulating composite material. Opacified superinsulating aerogel permit a number of industrial applications for aerogel-based insulation. The primary benefits from this recently developed superinsulating composite aerogel insulation are: to extend the range of applications to higher temperatures, to provide a more compact insulation for space sensitive-applications, and to lower costs of aerogel by as much as 30%. Superinsulating aerogels can replace existing CFC-containing polyurethane in low temperature applications to reduce heat losses in piping, improve the thermal efficiency of refrigeration systems, and reduce energy losses in a variety of industrial applications. Enhanced aerogel insulation can also replace steam and process pipe insulation in higher temperature applications to substantially reduce energy losses and provide much more compact insulation.

  6. Nitrogen-rich and fire-resistant carbon aerogels for the removal of oil contaminants from water.

    PubMed

    Yang, Yu; Tong, Zhen; Ngai, To; Wang, Chaoyang

    2014-05-14

    Effective removal of crude oils, petroleum products, organic solvents, and dyes from water is of significance in oceanography, environmental protection, and industrial production. Various techniques including physical and chemical absorption have been developed, but they suffer from problems such as low separation selectivity, a complicated and lengthy process, as well as high costs for reagents and devices. We present here a new material, termed nitrogen-rich carbon aerogels (NRC aerogels,) with highly porous structure and nitrogen-rich surfaces, exhibiting highly efficient separation of specific substances such as oils and organic pollutants. More importantly, we demonstrate that the fabricated NRC aerogels can also collect micrometer-sized oil droplets from an oil-water mixture with high efficiency that is well beyond what can be achieved by most existing separation methods, but is extremely important in practical marine oil-spill recovery because a certain amount of oils often shears into many micrometer-sized oil droplets by the sea wave, resulting in enormous potential destruction to marine ecosystem if not properly collected. Furthermore, our fabricated material can be used like a recyclable container for oils and chemicals cleanup because the oil/chemical-absorbed NRC aerogels can be readily cleaned for reuse by direct combustion in air because of their excellent hydrophobicity and fire-resistant property. We demonstrate that they keep 61.2% absorption capacity even after 100 absorption/combustion cycles, which thus has the highest recyclability of the reported carbon aerogels. All these features make these fabricated NRC aerogels suitable for a wide range of applications in water purification and treatment.

  7. Benzimidazole Based Aerogel Materials

    NASA Technical Reports Server (NTRS)

    Rhine, Wendell E. (Inventor); Mihalcik, David (Inventor)

    2016-01-01

    The present invention provides aerogel materials based on imidazoles and polyimidazoles. The polyimidazole based aerogel materials can be thermally stable up to 500 C or more, and can be carbonized to produce a carbon aerogel having a char yield of 60% or more, specifically 70% or more. The present invention also provides methods of producing polyimidazole based aerogel materials by reacting at least one monomer in a suitable solvent to form a polybenzimidazole gel precursor solution, casting the polybenzimidazole gel precursor solution into a fiber reinforcement phase, allowing the at least one gel precursor in the precursor solution to transition into a gel material, and drying the gel materials to remove at least a portion of the solvent, to obtain an polybenzimidazole-based aerogel material.

  8. Cellulose aerogels functionalized with polypyrrole and silver nanoparticles: In-situ synthesis, characterization and antibacterial activity.

    PubMed

    Wan, Caichao; Li, Jian

    2016-08-01

    Green porous and lightweight cellulose aerogels have been considered as promising candidates to substitute some petrochemical host materials to support various nanomaterials. In this work, waste wheat straw was collected as feedstock to fabricate cellulose hydrogels, and a green inexpensive NaOH/polyethylene glycol solution was used as cellulose solvent. Prior to freeze-drying treatment, the cellulose hydrogels were integrated with polypyrrole and silver nanoparticles by easily-operated in-situ oxidative polymerization of pyrrole using silver ions as oxidizing agent. The tri-component hybrid aerogels were characterized by scanning electron microscope, transmission electron microscope, energy dispersive X-ray spectroscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, and X-ray diffraction. Moreover, the antibacterial activity of the hybrid aerogels against Escherichia coli (Gram-negative), Staphylococcus aureus (Gram-positive) and Listeria monocytogenes (intracellular bacteria) was qualitatively and quantitatively investigated by parallel streak method and determination of minimal inhibitory concentration, respectively. This work provides an example of combining cellulose aerogels with nanomaterials, and helps to develop novel forms of cellulose-based functional materials. PMID:27112885

  9. High-efficiency electrochemical thermal energy harvester using carbon nanotube aerogel sheet electrodes

    PubMed Central

    Im, Hyeongwook; Kim, Taewoo; Song, Hyelynn; Choi, Jongho; Park, Jae Sung; Ovalle-Robles, Raquel; Yang, Hee Doo; Kihm, Kenneth D.; Baughman, Ray H.; Lee, Hong H.; Kang, Tae June; Kim, Yong Hyup

    2016-01-01

    Conversion of low-grade waste heat into electricity is an important energy harvesting strategy. However, abundant heat from these low-grade thermal streams cannot be harvested readily because of the absence of efficient, inexpensive devices that can convert the waste heat into electricity. Here we fabricate carbon nanotube aerogel-based thermo-electrochemical cells, which are potentially low-cost and relatively high-efficiency materials for this application. When normalized to the cell cross-sectional area, a maximum power output of 6.6 W m−2 is obtained for a 51 °C inter-electrode temperature difference, with a Carnot-relative efficiency of 3.95%. The importance of electrode purity, engineered porosity and catalytic surfaces in enhancing the thermocell performance is demonstrated. PMID:26837457

  10. High-efficiency electrochemical thermal energy harvester using carbon nanotube aerogel sheet electrodes.

    PubMed

    Im, Hyeongwook; Kim, Taewoo; Song, Hyelynn; Choi, Jongho; Park, Jae Sung; Ovalle-Robles, Raquel; Yang, Hee Doo; Kihm, Kenneth D; Baughman, Ray H; Lee, Hong H; Kang, Tae June; Kim, Yong Hyup

    2016-01-01

    Conversion of low-grade waste heat into electricity is an important energy harvesting strategy. However, abundant heat from these low-grade thermal streams cannot be harvested readily because of the absence of efficient, inexpensive devices that can convert the waste heat into electricity. Here we fabricate carbon nanotube aerogel-based thermo-electrochemical cells, which are potentially low-cost and relatively high-efficiency materials for this application. When normalized to the cell cross-sectional area, a maximum power output of 6.6 W m(-2) is obtained for a 51 °C inter-electrode temperature difference, with a Carnot-relative efficiency of 3.95%. The importance of electrode purity, engineered porosity and catalytic surfaces in enhancing the thermocell performance is demonstrated. PMID:26837457

  11. High-efficiency electrochemical thermal energy harvester using carbon nanotube aerogel sheet electrodes

    NASA Astrophysics Data System (ADS)

    Im, Hyeongwook; Kim, Taewoo; Song, Hyelynn; Choi, Jongho; Park, Jae Sung; Ovalle-Robles, Raquel; Yang, Hee Doo; Kihm, Kenneth D.; Baughman, Ray H.; Lee, Hong H.; Kang, Tae June; Kim, Yong Hyup

    2016-02-01

    Conversion of low-grade waste heat into electricity is an important energy harvesting strategy. However, abundant heat from these low-grade thermal streams cannot be harvested readily because of the absence of efficient, inexpensive devices that can convert the waste heat into electricity. Here we fabricate carbon nanotube aerogel-based thermo-electrochemical cells, which are potentially low-cost and relatively high-efficiency materials for this application. When normalized to the cell cross-sectional area, a maximum power output of 6.6 W m-2 is obtained for a 51 °C inter-electrode temperature difference, with a Carnot-relative efficiency of 3.95%. The importance of electrode purity, engineered porosity and catalytic surfaces in enhancing the thermocell performance is demonstrated.

  12. High-efficiency electrochemical thermal energy harvester using carbon nanotube aerogel sheet electrodes.

    PubMed

    Im, Hyeongwook; Kim, Taewoo; Song, Hyelynn; Choi, Jongho; Park, Jae Sung; Ovalle-Robles, Raquel; Yang, Hee Doo; Kihm, Kenneth D; Baughman, Ray H; Lee, Hong H; Kang, Tae June; Kim, Yong Hyup

    2016-02-03

    Conversion of low-grade waste heat into electricity is an important energy harvesting strategy. However, abundant heat from these low-grade thermal streams cannot be harvested readily because of the absence of efficient, inexpensive devices that can convert the waste heat into electricity. Here we fabricate carbon nanotube aerogel-based thermo-electrochemical cells, which are potentially low-cost and relatively high-efficiency materials for this application. When normalized to the cell cross-sectional area, a maximum power output of 6.6 W m(-2) is obtained for a 51 °C inter-electrode temperature difference, with a Carnot-relative efficiency of 3.95%. The importance of electrode purity, engineered porosity and catalytic surfaces in enhancing the thermocell performance is demonstrated.

  13. Self-Assembly Synthesis of N-Doped Carbon Aerogels for Supercapacitor and Electrocatalytic Oxygen Reduction.

    PubMed

    Zhang, Junli; Chen, Gaoli; Zhang, Qian; Kang, Fei; You, Bo

    2015-06-17

    The rational design of high-performance and cheap nanomaterials for multiple sustainable energy storage applications is extremely urgent but remains challenging. Herein, a facile commercial melamine-sponge-directed multicomponent surface self-assembly strategy has been reported to synthesize N-doped carbon aerogels (NCAs) with low density (0.01 g cm(-3)), large open pores, and high surface area (1626 m2 g(-1)). The commercial melamine sponge simultaneously serves as a green N source for N-doping and a 3D scaffold to buffer electrolytes for reducing ion transport resistance and minimizing ion diffusion distance. With their tailored architecture characteristics, the NCAs-based supercapacitor and oxygen reduction electrocatalyst show excellent performance.

  14. High surface area platinum-titania aerogels: Preparation, structural properties, and hydrogenation activity

    SciTech Connect

    Schneider, M.; Duff, D.G.; Mallat, T.; Wildberger, M.; Baiker, A. )

    1994-06-01

    High surface area platinum-titania aerogels with marked meso-to macroporosity have been synthesized via the sol-gel-aerogel route. An acid-catalyzed titania gel was prepared from tetrabutoxy-titanium(IV) with methanol as solvent. The platinum precursor solutions added after the redispersion of the titania gel were either PtCl[sub 4], (NH[sub 4])[sub 2]PtCl[sub 6] or Pt(acac)[sub 2] dissolved in protic solvents. Platinum metal particles formed upon high-temperature supercritical drying. The platinum-titania aerogels have a BET surface area of 150 to 190 m[sup 2] g[sup [minus]1] after thermal pretreatments up to 673 K and the titania matrix consists of well-developed anatase crystallites of about 8-9 nm mean size. Depending on the platinum precursor used, the volume-weighted-mean particle size, determined by TEM, varies in the range 3.6 to 68 nm, consistent with XRD results for the platinum component. All aerogel samples showed a pronounced stability of both the titania matrix and the platinum particles towards air or hydrogen at temperatures up to 673 K. Thermal analysis, combined with mass spectroscopy, revealed that the untreated catalysts contain a considerable amount of entrapped organic impurities after the high-temperature supercritical drying. For the characterization of the activity and the accessibility of platinum particles the liquid phase hydrogenations of trans-stilbene and benzophenone were used as test reactions. Compared to a commercial alumina-supported platinum catalyst, the untreated 2-5 wt% platinum-titania catalysts derived from (NH[sub 4])[sub 2]PtCl[sub 6]- and especially PtCl[sub 4]-precursor solutions exhibit a markedly higher catalytic activity. In general, air pretreatments at 573 K or above had either no or promoting influence on activity. In contrast, pretreatments in hydrogen produced either no or detrimental activity change. 50 refs., 9 figs., 3 tabs.

  15. Green and facile fabrication of carbon aerogels from cellulose-based waste newspaper for solving organic pollution.

    PubMed

    Han, Shenjie; Sun, Qingfeng; Zheng, Huanhuan; Li, Jingpeng; Jin, Chunde

    2016-01-20

    Carbon-based aerogel fabricated from waste biomass is a potential absorbent material for solving organic pollution. Herein, the lightweight, hydrophobic and porous carbon aerogels (CAs) have been synthesized through freezing-drying and post-pyrolysis by using waste newspaper as the only raw materials. The as-prepared CAs exhibited a low density of 18.5 mg cm(-3) and excellent hydrophobicity with a water contact angle of 132° and selective absorption for organic reagents. The absorption capacity of CA for organic compounds can be 29-51 times its own weight. Moreover, three methods (e.g., squeezing, combustion, and distillation) can be employed to recycle CA and harvest organic pollutants. Combined with waste biomass as raw materials, green and facile fabrication process, excellent hydrophobicity and oleophilicity, CA used as an absorbent material has great potential in application of organic pollutant solvents absorption and environmental protection. PMID:26572333

  16. Green and facile fabrication of carbon aerogels from cellulose-based waste newspaper for solving organic pollution.

    PubMed

    Han, Shenjie; Sun, Qingfeng; Zheng, Huanhuan; Li, Jingpeng; Jin, Chunde

    2016-01-20

    Carbon-based aerogel fabricated from waste biomass is a potential absorbent material for solving organic pollution. Herein, the lightweight, hydrophobic and porous carbon aerogels (CAs) have been synthesized through freezing-drying and post-pyrolysis by using waste newspaper as the only raw materials. The as-prepared CAs exhibited a low density of 18.5 mg cm(-3) and excellent hydrophobicity with a water contact angle of 132° and selective absorption for organic reagents. The absorption capacity of CA for organic compounds can be 29-51 times its own weight. Moreover, three methods (e.g., squeezing, combustion, and distillation) can be employed to recycle CA and harvest organic pollutants. Combined with waste biomass as raw materials, green and facile fabrication process, excellent hydrophobicity and oleophilicity, CA used as an absorbent material has great potential in application of organic pollutant solvents absorption and environmental protection.

  17. Cobalt carbonate/ and cobalt oxide/graphene aerogel composite anodes for high performance Li-ion batteries.

    PubMed

    Garakani, Mohammad Akbari; Abouali, Sara; Zhang, Biao; Takagi, Curtis Alton; Xu, Zheng-Long; Huang, Jian-qiu; Huang, Jiaqiang; Kim, Jang-Kyo

    2014-11-12

    Nanocomposites consisting of ultrafine, cobalt carbonate nanoneedles and 3D porous graphene aerogel (CoCO3/GA) are in situ synthesized based on a one-step hydrothermal route followed by freeze-drying. A further heat treatment produces cobalt oxide nanoparticles embedded in the conductive GA matrix (Co(3)O(4)/GA). Both the composite anodes deliver excellent specific capacities depending on current density employed: the CoCO(3)/GA anode outperforms the Co(3)O(4)/GA anode at low current densities, and vice versa at current densities higher than 500 mA g(-1). Their electrochemical performances are considered among the best of similar composite anodes consisting of CoCO(3) or Co(3)O(4) active particles embedded in a graphene substrate. The stable multistep electrochemical reactions of the carbonate compound with a unique nanoneedle structure contribute to the excellent cyclic stability of the CoCO(3)/GA electrode, whereas the highly conductive networks along with low charge transfer resistance are responsible for the high rate performance of the Co(3)O(4)/GA electrode.

  18. Carbon Nanofiber Incorporated Silica Based Aerogels with Di-Isocyanate Cross-Linking

    NASA Technical Reports Server (NTRS)

    Vivod, Stephanie L.; Meador, Mary Ann B.; Capadona, Lynn A.; Sullivan, Roy M.; Ghosn, Louis J.; Clark, Nicholas; McCorkle, Linda

    2008-01-01

    Lightweight materials with excellent thermal insulating properties are highly sought after for a variety of aerospace and aeronautic applications. (1) Silica based aerogels with their high surface area and low relative densities are ideal for applications in extreme environments such as insulators for the Mars Rover battery. (2) However, the fragile nature of aerogel monoliths prevents their widespread use in more down to earth applications. We have shown that the fragile aerogel network can be cross-linked with a di-isocyanate via amine decorated surfaces to form a conformal coating. (3) This coating reinforces the neck regions between secondary silica particles and significantly strengthens the aerogels with only a small effect on density or porosity. Scheme 1 depicts the cross-linking reaction with the di-isocyanate and exhibits the stages that result in polymer cross-linked aerogel monoliths.

  19. Strain-driven and ultrasensitive resistive sensor/switch based on conductive alginate/nitrogen-doped carbon-nanotube-supported Ag hybrid aerogels with pyramid design.

    PubMed

    Zhao, Songfang; Zhang, Guoping; Gao, Yongju; Deng, Libo; Li, Jinhui; Sun, Rong; Wong, Ching-Ping

    2014-12-24

    Flexible strain-driven sensor is an essential component in the flexible electronics. Especially, high durability and sensitivity to strain are required. Here, we present an efficient and low-cost fabrication strategy to construct a highly sensitive and flexible pressure sensor based on a conductive, elastic aerogel with pyramid design. When pressure is loaded, the contact area between the interfaces of the conductive aerogel and the copper electrode as well as among the building blocks of the nitrogen-doped carbon-nanotube-supported Ag (N-CNTs/Ag) aerogel monoliths, changes in reversible and directional manners. This contact resistance mechanism enables the hybrid aerogels to act as strain-driven sensors with high sensitivity and excellent on/off swithching behavior, and the gauge factor (GF) is ∼15 under strain of 3%, which is superior to those reported for other aerogels. In addition, robust, elastomeric and conductive nanocomposites can be fabricated by injecting polydimethylsiloxane (PDMS) into alginate/N-CNTs/Ag aerogels. Importantly, the building blocks forming the aerogels retain their initial contact and percolation after undergoing large-strain deformation, PDMS infiltration, and cross-linking of PDMS, suggesting their potential applications as strain sensors.

  20. Strain-driven and ultrasensitive resistive sensor/switch based on conductive alginate/nitrogen-doped carbon-nanotube-supported Ag hybrid aerogels with pyramid design.

    PubMed

    Zhao, Songfang; Zhang, Guoping; Gao, Yongju; Deng, Libo; Li, Jinhui; Sun, Rong; Wong, Ching-Ping

    2014-12-24

    Flexible strain-driven sensor is an essential component in the flexible electronics. Especially, high durability and sensitivity to strain are required. Here, we present an efficient and low-cost fabrication strategy to construct a highly sensitive and flexible pressure sensor based on a conductive, elastic aerogel with pyramid design. When pressure is loaded, the contact area between the interfaces of the conductive aerogel and the copper electrode as well as among the building blocks of the nitrogen-doped carbon-nanotube-supported Ag (N-CNTs/Ag) aerogel monoliths, changes in reversible and directional manners. This contact resistance mechanism enables the hybrid aerogels to act as strain-driven sensors with high sensitivity and excellent on/off swithching behavior, and the gauge factor (GF) is ∼15 under strain of 3%, which is superior to those reported for other aerogels. In addition, robust, elastomeric and conductive nanocomposites can be fabricated by injecting polydimethylsiloxane (PDMS) into alginate/N-CNTs/Ag aerogels. Importantly, the building blocks forming the aerogels retain their initial contact and percolation after undergoing large-strain deformation, PDMS infiltration, and cross-linking of PDMS, suggesting their potential applications as strain sensors. PMID:25423613

  1. Aerogel Projects Ongoing in MSFC's Engineering Directorate

    NASA Technical Reports Server (NTRS)

    Shular, D. A.; Smithers, G. A.; Plawsky, J. L.

    2001-01-01

    When we speak of an aerogel material, we are referring more to process and structure than to a specific substance. Aerogel, considered the lightest solid material, has been made from silica for seventy years. Resorcinol-formaldehyde, organic aerogels have been developed more recently. However, aerogel can be made from almost any type of substance, even lead. Because an aerogel is mostly air (about 99%), the solid substance used will affect the weight very little. The problem with aerogels is their low tensile strength and lack of elasticity. Therefore, the challenge is to find ways to make the stronger or ways to circumvent the strength issue. Organic aerogels have slightly higher strength than base silica aerogels, while the carbonized version has three to five times the break strength of the base aerogel.

  2. Nanoporous Cu-C composites based on carbon-nanotube aerogels

    SciTech Connect

    Charnvanichborikarn, S.; Shin, S. J.; Worsley, M. A.; Tran, I. C.; Willey, T. M.; van Buuren, T.; Felter, T. E.; Colvin, J. D.; Kucheyev, S. O.

    2013-11-22

    Current synthesis methods of nanoporous Cu–C composites offer limited control of the material composition, structure, and properties, particularly for large Cu loadings of ≳20 wt%. Here, we describe two related approaches to realize novel nanoporous Cu–C composites based on the templating of recently developed carbon-nanotube aerogels (CNT-CAs). Our first approach involves the trapping of Cu nanoparticles while CNT-CAs undergo gelation. This method yields nanofoams with relatively high densities of ≳65 mg cm-3 for Cu loadings of ≳10 wt%. Our second approach overcomes this limitation by filling the pores of undoped CNT-CA monoliths with an aqueous solution of CuSO4 followed by (i) freeze-drying to remove water and (ii) thermal decomposition of CuSO4. With this approach, we demonstrate Cu–C composites with a C matrix density of -25 mg cm-3 and Cu loadings of up to 70 wt%. These versatile methods could be extended to fabricate other nanoporous metal–carbon composite materials geared for specific applications.

  3. Thermal management of thermoacoustic sound projectors using a free-standing carbon nanotube aerogel sheet as a heat source

    NASA Astrophysics Data System (ADS)

    Aliev, Ali E.; Mayo, Nathanael K.; Baughman, Ray H.; Avirovik, Dragan; Priya, Shashank; Zarnetske, Michael R.; Blottman, John B.

    2014-10-01

    Carbon nanotube (CNT) aerogel sheets produce smooth-spectra sound over a wide frequency range (1-105 Hz) by means of thermoacoustic (TA) sound generation. Protective encapsulation of CNT sheets in inert gases between rigid vibrating plates provides resonant features for the TA sound projector and attractive performance at needed low frequencies. Energy conversion efficiencies in air of 2% and 10% underwater, which can be enhanced by further increasing the modulation temperature. Using a developed method for accurate temperature measurements for the thin aerogel CNT sheets, heat dissipation processes, failure mechanisms, and associated power densities are investigated for encapsulated multilayered CNT TA heaters and related to the thermal diffusivity distance when sheet layers are separated. Resulting thermal management methods for high applied power are discussed and deployed to construct efficient and tunable underwater sound projector for operation at relatively low frequencies, 10 Hz-10 kHz. The optimal design of these TA projectors for high-power SONAR arrays is discussed.

  4. Elastic Carbon Aerogels Reconstructed from Electrospun Nanofibers and Graphene as Three-Dimensional Networked Matrix for Efficient Energy Storage/Conversion.

    PubMed

    Huang, Yunpeng; Lai, Feili; Zhang, Longsheng; Lu, Hengyi; Miao, Yue-E; Liu, Tianxi

    2016-01-01

    Three-dimensional (3D) all-carbon nanofibrous aerogels with good structural stability and elasticity are highly desirable in flexible energy storage/conversion devices. Hence, an efficient surface-induced co-assembly strategy is reported for the novel design and reconstruction of electrospun nanofibers into graphene/carbon nanofiber (CNF) composite aerogels (GCA) with hierarchical structures utilizing graphene flakes as cross-linkers. The as-obtained GCA monoliths possess interconnected macropores and integrated conductive networks, which exhibit high elasticity and great structural robustness. Benefitting from the largely increased surface area and charge-transfer efficiency derived from the multi-form firm interconnections (including pillaring, bridging and jointing) between graphene flakes and CNF ribs, GCA not only reveals prominent capacitive performance as supercapacitor electrode, but also shows excellent hydrogen evolution reaction activity in both acidic and alkaline solutions as a 3D template for decoration of few-layered MoSe2 nanosheets, holding great potentials for energy-related applications. PMID:27511271

  5. Elastic Carbon Aerogels Reconstructed from Electrospun Nanofibers and Graphene as Three-Dimensional Networked Matrix for Efficient Energy Storage/Conversion

    PubMed Central

    Huang, Yunpeng; Lai, Feili; Zhang, Longsheng; Lu, Hengyi; Miao, Yue-E; Liu, Tianxi

    2016-01-01

    Three-dimensional (3D) all-carbon nanofibrous aerogels with good structural stability and elasticity are highly desirable in flexible energy storage/conversion devices. Hence, an efficient surface-induced co-assembly strategy is reported for the novel design and reconstruction of electrospun nanofibers into graphene/carbon nanofiber (CNF) composite aerogels (GCA) with hierarchical structures utilizing graphene flakes as cross-linkers. The as-obtained GCA monoliths possess interconnected macropores and integrated conductive networks, which exhibit high elasticity and great structural robustness. Benefitting from the largely increased surface area and charge-transfer efficiency derived from the multi-form firm interconnections (including pillaring, bridging and jointing) between graphene flakes and CNF ribs, GCA not only reveals prominent capacitive performance as supercapacitor electrode, but also shows excellent hydrogen evolution reaction activity in both acidic and alkaline solutions as a 3D template for decoration of few-layered MoSe2 nanosheets, holding great potentials for energy-related applications. PMID:27511271

  6. Elastic Carbon Aerogels Reconstructed from Electrospun Nanofibers and Graphene as Three-Dimensional Networked Matrix for Efficient Energy Storage/Conversion

    NASA Astrophysics Data System (ADS)

    Huang, Yunpeng; Lai, Feili; Zhang, Longsheng; Lu, Hengyi; Miao, Yue-E.; Liu, Tianxi

    2016-08-01

    Three-dimensional (3D) all-carbon nanofibrous aerogels with good structural stability and elasticity are highly desirable in flexible energy storage/conversion devices. Hence, an efficient surface-induced co-assembly strategy is reported for the novel design and reconstruction of electrospun nanofibers into graphene/carbon nanofiber (CNF) composite aerogels (GCA) with hierarchical structures utilizing graphene flakes as cross-linkers. The as-obtained GCA monoliths possess interconnected macropores and integrated conductive networks, which exhibit high elasticity and great structural robustness. Benefitting from the largely increased surface area and charge-transfer efficiency derived from the multi-form firm interconnections (including pillaring, bridging and jointing) between graphene flakes and CNF ribs, GCA not only reveals prominent capacitive performance as supercapacitor electrode, but also shows excellent hydrogen evolution reaction activity in both acidic and alkaline solutions as a 3D template for decoration of few-layered MoSe2 nanosheets, holding great potentials for energy-related applications.

  7. High specific surface area aerogel cryoadsorber for vacuum pumping applications

    DOEpatents

    Hill, Randal M.; Fought, Eric R.; Biltoft, Peter J.

    2000-01-01

    A cryogenic pumping system is provided, comprising a vacuum environment, an aerogel sorbent formed from a carbon aerogel disposed within the vacuum environment, and cooling means for cooling the aerogel sorbent sufficiently to adsorb molecules from the vacuum environment onto the aerogel sorbent. Embodiments of the invention include a liquid refrigerant cryosorption pump, a compressed helium cryogenic pump, a cryopanel and a Meissner coil, each of which uses carbon aerogel as a sorbent material.

  8. High Specific Surface area Aerogel Cryoadsorber for Vacuum Pumping Applications

    SciTech Connect

    Hill, Randal M.; Fought, Eric R.; Biltoft, Peter J.

    1998-12-22

    A cryogenic pumping system is provided, comprising a vacuum environment, an aerogel sorbent formed from a carbon aerogel disposed within the vacuum environment, and cooling means for cooling the aerogel sorbent sufficiently to adsorb molecules from the vacuum environment onto the aerogel sorbent. Embodiments of the invention include a liquid refrigerant cryosorption pump, a compressed helium cryogenic pump, a cryopanel and a Meissner coil, each of which uses carbon aerogel as a sorbent material.

  9. Improvements to the Synthesis of Polyimide Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Nguyen, Baochau N.; Guo, Haiquan; Vivod, Stephanie; He, Zuhui; Malow, Ericka; Silva, Rebecca

    2011-01-01

    Cross-linked polyimide aerogels are viable approach to higher temperature, flexible insulation for inflatable decelerators. Results indicate that the all-polyimide aerogels are as strong or stronger than polymer reinforced silica aerogels at the same density. Currently, examining use of carbon nanofiber and clay nanoparticles to improve performance. Flexible, polyimide aerogels have potential utility in other applications such as space suits, habitats, shelter applications, etc. where low dusting is desired

  10. Electrosorption on carbon aerogel electrodes as a means of treating low-level radioactive wastes and remediating contaminated ground water

    SciTech Connect

    Tran, Tri Duc; Farmer, Joseph C.; DePruneda, Jean H.; Richardson, Jeffery H.

    1997-07-01

    A novel separation process based upon carbon aerogel electrodes has been recently developed for the efficient removal of ionic impurities from aqueous streams. This process can be used as an electrical y- regenerated alternative to ion exchange, thereby reducing-the need for large quantities of chemical regenerants. Once spent (contaminated), these regenerants contribute to the waste that must be disposed of in landfills. The elimination of such wastes is especially beneficial in situations involving radioactive contaminants, and pump and treat processing of massive volumes of ground water. A review and analysis of potential applications will be presented.

  11. Versatile Cellulose-Based Carbon Aerogel for the Removal of Both Cationic and Anionic Metal Contaminants from Water.

    PubMed

    Alatalo, Sara-Maaria; Pileidis, Filoklis; Mäkilä, Ermei; Sevilla, Marta; Repo, Eveliina; Salonen, Jarno; Sillanpää, Mika; Titirici, Maria-Magdalena

    2015-11-25

    Hydrothermal carbonization of cellulose in the presence of the globular protein ovalbumin leads to the formation of nitrogen-doped carbon aerogel with a fibrillar continuous carbon network. The protein plays here a double role: (i) a natural source of nitrogen functionalities (2.1 wt %) and (ii) structural directing agent (S(BET) = 38 m(2)/g). The applicability in wastewater treatment, namely, for heavy metal removal, was examined through adsorption of Cr(VI) and Pb(II) ion solely and in a mixed bicomponent aqueous solutions. This cellulose-based carbogel shows an enhanced ability to remove both Cr(VI) (∼68 mg/g) and Pb(II) (∼240 mg/g) from the targeted solutions in comparison to other carbon materials reported in the literature. The presence of competing ions showed little effect on the adsorption efficiency toward Cr(VI) and Pb(II).

  12. Co3O4/carbon aerogel hybrids as anode materials for lithium-ion batteries with enhanced electrochemical properties.

    PubMed

    Hao, Fengbin; Zhang, Zhiwei; Yin, Longwei

    2013-09-11

    A facile hydrothermal and sol-gel polymerization route was developed for large-scale fabrication of well-designed Co3O4 nanoparticles anchored carbon aerogel (CA) architecture hybrids as anode materials for lithium-ion batteries with improved electrochemical properties. The three-dimensional (3D) mesoporous Co3O4/CA hierarchical hybrids display an improved lithium storage performance and cycling stability, because of the intimate integration and strong synergistic effects between the Co3O4 nanoparticles and CA matrices. Such an interconnected Co3O4/CA hierarchical hybrid can effectively utilize the good conductivity, large surface area, 3D interconnected mesoporous structure, mechanical flexibility, chemical stability, and the short length of Li-ion transport of the CA matrix. The incorporation of Co3O4 nanoparticles into the interconnected CA matrix effectively reduces the number of active sites of Co3O4/CA hybrids, thus greatly increasing the reversible specific capacity and the initial Coulombic efficiency of the hybrids. The Co3O4/CA hybrid material displays the best lithium storage performance and good cycling stability as the Co3O4 loading content is up to 25 wt %, retains a Coulombic efficiency of 99.5% and a specific discharge capacity of 779 mAh g(-1) after 50 cycles, 10.1 and 1.6 times larger than the specific discharge capacity of 73 mAh g(-1) and 478 mAh g(-1) for Co3O4 and CA samples, respectively. The hierarchical hybrid nanostructures with enhanced electrochemical activities using a CA matrix framework can find potential applications in the related conversion reaction electrodes.

  13. Environmentally Friendly Method: Development and Application to Carbon Aerogel as Sorbent for Solid-Phase Extraction.

    PubMed

    Dong, Sheying; Huang, Guiqi; Su, Meiling; Huang, Tinglin

    2015-10-14

    We developed two simple, fast, and environmentally friendly methods using carbon aerogel (CA) and magnetic CA (mCA) materials as sorbents for micro-solid-phase extraction (μ-SPE) and magnetic solid-phase extraction (MSPE) techniques. The material performances such as adsorption isotherm, adsorption kinetics, and specific surface area were discussed by N2 adsorption-desorption isotherm measurements, ultraviolet and visible (UV-vis) spectrophotometry, scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HR-TEM). The experimental results proved that the heterogeneities of CA and mCA were well modeled with the Freundlich isotherm model, and the sorption process well followed the pseudo-second-order rate equation. Moreover, plant growth regulators (PGRs) such as kinetin (6-KT), 6-benzylaminopurine (6-BA), 2,4-dichlorophenoxyacetic acid (2,4-D), and uniconazole (UN) in a reservoir raw water sample were selected as the evaluation of applicability for the proposed μ-SPE and MSPE techniques using high performance liquid chromatography (HPLC). The experimental conditions of two methods such as the amount of sorbent, extraction time, pH, salt concentration, and desorption conditions were studied. Under the optimized conditions, two extraction methods provided high recoveries (89-103%), low the limits of detection (LODs) (0.01-0.2 μg L(-1)), and satisfactory analytical features in terms of precision (relative standard deviation, RSD, 1.7-5.1%, n=3). This work demonstrates the feasibility and the potential of CA and mCA materials as sorbents for μ-SPE and MSPE techniques. Besides, it also could serve as a basis for future development of other functional CAs in pretreatment technology and make them valuable for analysis of pollutants in environmental applications.

  14. Flexible, Transparent and Conductive Carbon Nanotube Aerogels /PEDOT:PSS Electrodes created by Top-bottom Fabrication

    NASA Astrophysics Data System (ADS)

    Martinez, Patricia M.; Cerdan Pasaran, Andrea; Zakhidov, Anvar; University of Guanajuato, Mexico Collaboration

    The sheets of Carbon Nanotubes (CNT) have proven to be a good substitute for ITO. To improve their conductivity and increase optical transparency we have created composites which incorporate silver nanowires or other evaporated metals. Coating CNT/metals with PEDOT:PSS is important for creating hole transport/electron barrier layer functionality, but it is not easy to achieve using PEDOT:PSS solutions due to the hydrophobicity of CNT. We report a new top-to-bottom approach for the fabrication of highly flexible, transparent and conductive carbon nanotube-based electrodes using PDMS as a substrate. A uniform and smooth layer of approximately 50 nm of PEDOT:PSS was spin coated on top of a PDMS stamp followed by the deposition of vapor densified freestanding Multiwall Carbon Nanotube (MWNT) aerogels. An incorporation of silver nanowires, silver or Aluminum thin layer can be sprayed or evaporated on top of the freestanding MWNT aerogels in order to lower the sheet resistance even further. The PDMS substrate is drop cast on top of the configuration then the PDMS stamp is lifted-up. The PEDOT:PSS layer is selectively deposited on top of the MWNT only. The composite electrodes can be laminated on photovoltaic devices and on LEDs.

  15. Graphene aerogels

    DOEpatents

    Pauzauskie, Peter J; Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H; Biener, Juergen

    2015-03-31

    Graphene aerogels with high conductivity and surface areas including a method for making a graphene aerogel, including the following steps: (1) preparing a reaction mixture comprising a graphene oxide suspension and at least one catalyst; (2) curing the reaction mixture to produce a wet gel; (3) drying the wet gel to produce a dry gel; and (4) pyrolyzing the dry gel to produce a graphene aerogel. Applications include electrical energy storage including batteries and supercapacitors.

  16. Aerogel Development

    NASA Technical Reports Server (NTRS)

    Sahai, Rashmi K.

    2005-01-01

    Aerogel is one of the most promising materials of the future. It's unique properties, including high porosity, transparency, very high thermal tolerance, and environmental friendliness give it the potential of replacing many different products used in society today. However, the market for aerogel is still very limited because of the cost of producing the material and its fragility. The principle objective of my project has been to find new ways to apply aerogel in order to increase its practicality and appeal to different aspects of society. More specifically, I have focused on finding different chemicals that will coat aerogel and increase its durability. Because aerogel is so fragile and will crumble under the pressure of most coatings this has been no easy task. However, by experimenting with many different coatings and combinations of aerogel properties, I have made several significant discoveries. Aerogel (ideally, high density and hydrophobic) can be coated with several acrylic polymers, including artist's gel and nail polish. These materials provide a protective layering around the aerogel and keep it from breaking as easily. Because fragility is one of the main reasons applications of aerogel are limited, these discoveries will hopefully aid in finding future applications for this extraordinary material.

  17. Polyurea-Based Aerogel Monoliths and Composites

    NASA Technical Reports Server (NTRS)

    Lee, Je Kyun

    2012-01-01

    aerogel insulation material was developed that will provide superior thermal insulation and inherent radiation protection for government and commercial applications. The rubbery polyureabased aerogel exhibits little dustiness, good flexibility and toughness, and durability typical of the parent polyurea polymer, yet with the low density and superior insulation properties associated with aerogels. The thermal conductivity values of polyurea-based aerogels at lower temperature under vacuum pressures are very low and better than that of silica aerogels. Flexible, rubbery polyurea-based aerogels are able to overcome the weak and brittle nature of conventional inorganic and organic aerogels, including polyisocyanurate aerogels, which are generally prepared with the one similar component to polyurethane rubber aerogels. Additionally, with higher content of hydrogen in their structures, the polyurea rubber-based aerogels will also provide inherently better radiation protection than those of inorganic and carbon aerogels. The aerogel materials also demonstrate good hydrophobicity due to their hydrocarbon molecular structure. There are several strategies to overcoming the drawbacks associated with the weakness and brittleness of silica aerogels. Development of the flexible fiber-reinforced silica aerogel composite blanket has proven to be one promising approach, providing a conveniently fielded form factor that is relatively robust in industrial environments compared to silica aerogel monoliths. However, the flexible, silica aerogel composites still have a brittle, dusty character that may be undesirable, or even intolerable, in certain application environments. Although the cross - linked organic aerogels, such as resorcinol- formaldehyde (RF), polyisocyanurate, and cellulose aerogels, show very high impact strength, they are also very brittle with little elongation (i.e., less rubbery). Also, silica and carbon aerogels are less efficient radiation shielding materials due

  18. Tailoring aerogel electrodes for electrochemical applications

    NASA Astrophysics Data System (ADS)

    Sakamoto, Jeffrey Steven

    2001-07-01

    The principal theme of the dissertation research was determining the relation between aerogel electrode morphology and electrochemical performance. Issues such as electrical wiring and mass transport in transition metal oxide, aerogel electrodes were addressed and designs were tailored for electrochemical applications. Single-wall carbon nanotubes were used to form the electronically conducting network in lithium intercalation electrodes that incorporated vanadium oxide aerogel as the active material. The similarities in morphology and dimensional scale for the nanotubes and V2O5 ribbons enabled excellent electrical contact to be made between the two phases without seriously affecting the aerogel nanostructure. The electrodes exhibited specific capacities in excess of 400 mAh/g at high discharge rates and retained this level of capacity on cycling. A second research goal was to improve mass transport within the aerogel electrode by minimizing tortuosity. In this research, hierarchically ordered vanadium oxide aerogel electrodes were designed and fabricated. The electrodes have two discrete and independent levels or porosity. At one level, ordered, interconnected macropores were fabricated using the templating process. At another level, interconnected mesopores were created using sol-gel synthesis and ambient drying. Electrochemical activity towards lithium was demonstrated using cyclic voltammetry and chronopotentiometry. These data are believed to be the first to demonstrate electrochemical activity for the class of materials based on the inverse opal structure. Several Group I cations and multivalent cations were reversibly, and electrochemically reacted with vanadium oxide aerogel. The molar capacities of the Group I elements (Na+ = 3.0 moles and K+ = 2.0) were high and comparable to Li+ (3.6 moles). Interestingly, the electron equivalent capacity for Mg2+ (4.0) was higher than Li+ and agrees well with the chemical titration capacity. Galvanostatic rate

  19. Nitrogen-Doped Carbon Nanotube Aerogels for High-Performance ORR Catalysts.

    PubMed

    Du, Ran; Zhang, Na; Zhu, Jinghan; Wang, Ying; Xu, Chenyu; Hu, Yue; Mao, Nannan; Xu, Hua; Duan, Wenjie; Zhuang, Lin; Qu, Liangti; Hou, Yanglong; Zhang, Jin

    2015-08-26

    By utilizing the dual roles of the erasable promoter (pyrrole), "clean", highly conductive, and nitrogen-doped CNT aerogels are derived from a promoter-assisted hydrothermal reaction (HTR) coupling with pyrolysis. The resulting materials show an excellent performance towards oxygen reduction reaction (ORR).

  20. One-Pot Synthesis of Pomegranate-Structured Fe3 O4 /Carbon Nanospheres-Doped Graphene Aerogel for High-Rate Lithium Ion Batteries.

    PubMed

    He, Dafang; Li, Lixian; Bai, Fengjuan; Zha, Chenyang; Shen, Liming; Kung, Harold H; Bao, Ningzhong

    2016-03-18

    A unique hierarchically nanostructured composite of iron oxide/carbon (Fe3O4/C) nanospheres-doped three-dimensional (3D) graphene aerogel has been fabricated by a one-pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe3O4 nanocrystals (5-10 nm) are individually embedded in carbon nanospheres (ca. 50 nm) forming a pomegranate-like structure. The carbon matrix suppresses the aggregation of Fe3O4 nanocrystals, avoids direct exposure of the encapsulated Fe3O4 to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe3O4/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe3O4 nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long-term stability of 634 mA h g(-1) over 1000 cycles at a high current density of 6 A g(-1) (7 C), and an excellent rate capability of 413 mA h g(-1) at 10 A g(-1) (11 C), thus exhibiting great potential as an anode composite structure for durable high-rate lithium-ion batteries. PMID:26879124

  1. One-Pot Synthesis of Pomegranate-Structured Fe3 O4 /Carbon Nanospheres-Doped Graphene Aerogel for High-Rate Lithium Ion Batteries.

    PubMed

    He, Dafang; Li, Lixian; Bai, Fengjuan; Zha, Chenyang; Shen, Liming; Kung, Harold H; Bao, Ningzhong

    2016-03-18

    A unique hierarchically nanostructured composite of iron oxide/carbon (Fe3O4/C) nanospheres-doped three-dimensional (3D) graphene aerogel has been fabricated by a one-pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe3O4 nanocrystals (5-10 nm) are individually embedded in carbon nanospheres (ca. 50 nm) forming a pomegranate-like structure. The carbon matrix suppresses the aggregation of Fe3O4 nanocrystals, avoids direct exposure of the encapsulated Fe3O4 to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe3O4/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe3O4 nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long-term stability of 634 mA h g(-1) over 1000 cycles at a high current density of 6 A g(-1) (7 C), and an excellent rate capability of 413 mA h g(-1) at 10 A g(-1) (11 C), thus exhibiting great potential as an anode composite structure for durable high-rate lithium-ion batteries.

  2. Structural studies of carbon aerogels and their metal-loaded derivatives

    NASA Astrophysics Data System (ADS)

    Kang, Dafei

    Carbon aerogels (CAs) are a class of mesoporous materials derived from the sol-gel polymerization of resorcinol (R) and formaldehyde (F) under base catalyse (C) in an aqueous solution, followed by supercritical drying and pyrolysis. CAs are characterized by highly-uniform pore sizes that can be tailored according to the reaction conditions, high surface areas, low densities, and high electrical conductivities. Due to the combination of these properties, CAs receive wide attention for such applications as the electrodes in fuel cells and supercapacitors, and supports for catalytic noble metals, to name but a few. Their high infrared optical absorption coefficients also make them promising materials for high-temperature thermal insulation and black broad-band absorption. This dissertation is a comprehensive study of the structural aspects of naked CAs and their metal-loaded derivatives. As-prepared CAs were also subjected to a series of post-pyrolysis treatments, such as high-temperature heat-treatment and in-situ electron irradiation in TEM. In the first part of this study, it is shown using nitrogen physisorption and transmission electron microscopy (TEM) that the pore characters of CAs can be engineered by systematically adjusting the key parameters of the initial R-F reaction. These parameters include the ratio of resorcinol to catalyst (R/C) and the ratio of resorcinol to water (R/W). Such adjustments resulted in the preparation of a series of CAs with average pore diameter ranging from 4 to 22nm. In a parallel study, it is shown that the use of acidic catalyst caused a drastic change in the pore type of the resulting materials. In this case, macropores are dominant. A selected group of noble metals (ruthenium and platinum) were incorporated into CA substrates via a novel supercritical carbon dioxide deposition, followed by a thermal reduction of the metal precursor. TEM results show that the metal nanoparticles thus prepared exhibit surprisingly uniform size

  3. Formation of nanoporous aerogels from wheat starch.

    PubMed

    Ubeyitogullari, Ali; Ciftci, Ozan N

    2016-08-20

    Biodegradable nanoporous aerogels were obtained from wheat starch using a simple and green method based on supercritical carbon dioxide (SC-CO2) drying. Effects of processing parameters (temperature, wheat starch concentration and mixing rate during gelatinization; temperature, pressure, and flow rate of CO2, during SC-CO2 drying) on the aerogel formation were investigated, and optimized for the highest surface area and smallest pore size of the aerogels. At the optimized conditions, wheat starch aerogels had surface areas between 52.6-59.7m(2)/g and densities ranging between 0.05-0.29g/cm(3). The average pore size of the starch aerogels was 20nm. Starch aerogels were stable up to 280°C. Due to high surface area and nanoporous structure, wheat starch aerogels are promising carrier systems for bioactives and drugs in food and pharmaceutical industries. PMID:27178916

  4. Thermal management of thermoacoustic sound projectors using a free-standing carbon nanotube aerogel sheet as a heat source.

    PubMed

    Aliev, Ali E; Mayo, Nathanael K; Baughman, Ray H; Avirovik, Dragan; Priya, Shashank; Zarnetske, Michael R; Blottman, John B

    2014-10-10

    Carbon nanotube (CNT) aerogel sheets produce smooth-spectra sound over a wide frequency range (1-10(5) Hz) by means of thermoacoustic (TA) sound generation. Protective encapsulation of CNT sheets in inert gases between rigid vibrating plates provides resonant features for the TA sound projector and attractive performance at needed low frequencies. Energy conversion efficiencies in air of 2% and 10% underwater, which can be enhanced by further increasing the modulation temperature. Using a developed method for accurate temperature measurements for the thin aerogel CNT sheets, heat dissipation processes, failure mechanisms, and associated power densities are investigated for encapsulated multilayered CNT TA heaters and related to the thermal diffusivity distance when sheet layers are separated. Resulting thermal management methods for high applied power are discussed and deployed to construct efficient and tunable underwater sound projector for operation at relatively low frequencies, 10 Hz-10 kHz. The optimal design of these TA projectors for high-power SONAR arrays is discussed.

  5. Efficiently dense hierarchical graphene based aerogel electrode for supercapacitors

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Lu, Chengxing; Peng, Huifen; Zhang, Xin; Wang, Zhenkun; Wang, Gongkai

    2016-08-01

    Boosting gravimetric and volumetric capacitances simultaneously at a high rate is still a discrepancy in development of graphene based supercapacitors. We report the preparation of dense hierarchical graphene/activated carbon composite aerogels via a reduction induced self-assembly process coupled with a drying post treatment. The compact and porous structures of composite aerogels could be maintained. The drying post treatment has significant effects on increasing the packing density of aerogels. The introduced activated carbons play the key roles of spacers and bridges, mitigating the restacking of adjacent graphene nanosheets and connecting lateral and vertical graphene nanosheets, respectively. The optimized aerogel with a packing density of 0.67 g cm-3 could deliver maximum gravimetric and volumetric capacitances of 128.2 F g-1 and 85.9 F cm-3, respectively, at a current density of 1 A g-1 in aqueous electrolyte, showing no apparent degradation to the specific capacitance at a current density of 10 A g-1 after 20000 cycles. The corresponding gravimetric and volumetric capacitances of 116.6 F g-1 and 78.1 cm-3 with an acceptable cyclic stability are also achieved in ionic liquid electrolyte. The results show a feasible strategy of designing dense hierarchical graphene based aerogels for supercapacitors.

  6. Efficiently dense hierarchical graphene based aerogel electrode for supercapacitors

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Lu, Chengxing; Peng, Huifen; Zhang, Xin; Wang, Zhenkun; Wang, Gongkai

    2016-08-01

    Boosting gravimetric and volumetric capacitances simultaneously at a high rate is still a discrepancy in development of graphene based supercapacitors. We report the preparation of dense hierarchical graphene/activated carbon composite aerogels via a reduction induced self-assembly process coupled with a drying post treatment. The compact and porous structures of composite aerogels could be maintained. The drying post treatment has significant effects on increasing the packing density of aerogels. The introduced activated carbons play the key roles of spacers and bridges, mitigating the restacking of adjacent graphene nanosheets and connecting lateral and vertical graphene nanosheets, respectively. The optimized aerogel with a packing density of 0.67 g cm-3 could deliver maximum gravimetric and volumetric capacitances of 128.2 F g-1 and 85.9 F cm-3, respectively, at a current density of 1 A g-1 in aqueous electrolyte, showing no apparent degradation to the specific capacitance at a current density of 10 A g-1 after 20000 cycles. The corresponding gravimetric and volumetric capacitances of 116.6 F g-1 and 78.1 cm-3 with an acceptable cyclic stability are also achieved in ionic liquid electrolyte. The results show a feasible strategy of designing dense hierarchical graphene based aerogels for supercapacitors.

  7. Effects of complexing ligand in sol-gel process on the photocatalytic activity of TiO2-C hybrid aerogels

    NASA Astrophysics Data System (ADS)

    Shao, Xia; Zhu, Linlin; Pan, Feng; Zhang, Shimin; Zhang, Rui; Chen, Donghui

    2015-06-01

    The effect of the acetylacetonate content, a complexing ligand during the one-step sol-gel preparation of TiO2-C hybrid aerogels on their photocatalytic performance for degradation of methylene blue (MB), was investigated. N2 adsorption, XRD, SEM, TEM, Raman and UV-vis spectroscopy were used to characterize the physics-chemical properties of the TiO2-C hybrid aerogels. Results show that complexing ligand can inhibit growth of TiO2 nanoparticles in sol-gel process. Thereby, the porous properties, adsorption equilibrium and kinetics for MB, crystalline size and band gap of the TiO2 in the hybrid aerogels are changed accordingly. The photocatalytic activity of the hybrid aerogels is dominantly determined by adsorption equilibrium and kinetics. Band-gap narrowing, reduced e--h+ recombination rate and light availability are also responsible for the high photocatalytic activity.

  8. Cotton Wool Derived Carbon Fiber Aerogel Supported Few-Layered MoSe2 Nanosheets As Efficient Electrocatalysts for Hydrogen Evolution.

    PubMed

    Zhang, Youfang; Zuo, Lizeng; Zhang, Longsheng; Huang, Yunpeng; Lu, Hengyi; Fan, Wei; Liu, Tianxi

    2016-03-23

    Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2 nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2 nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of -0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER. PMID:26927526

  9. Cotton Wool Derived Carbon Fiber Aerogel Supported Few-Layered MoSe2 Nanosheets As Efficient Electrocatalysts for Hydrogen Evolution.

    PubMed

    Zhang, Youfang; Zuo, Lizeng; Zhang, Longsheng; Huang, Yunpeng; Lu, Hengyi; Fan, Wei; Liu, Tianxi

    2016-03-23

    Recent studies have proven that newly emerging two-dimensional molybdenum diselenide (MoSe2) is a promising noble-metal-free electrocatalyst for hydrogen evolution reaction (HER). Increasing the exposures of the active edges of MoSe2 nanostructures is a key issue to fully realize the excellent electrochemical properties of MoSe2. In this work, a few-layered MoSe2/carbon fiber aerogel (CFA) hybrids have been facilely obtained through the combination of high-temperature carbonization and one-pot solvothermal reaction. CFA derived from cotton wool is used as a three-dimensional conductive network for construction of hierarchical MoSe2/CFA hybrids, where few-layered MoSe2 nanosheets are uniformly and perpendicularly decorated on the surfaces of CFA. In the designed and prepared hybrids, CFA effectively increases the exposures of the active edges of MoSe2 nanosheets as well as provides reduced lengths for both electron transportation and ion diffusion. Therefore, the obtained optimal MoSe2/CFA hybrid exhibits excellent electrochemical activity as HER electrocatalyst with a small onset potential of -0.104 V vs reversible hydrogen electrode and a small Tafel slope of 62 mV per decade, showing its great potential as a next-generation Pt-free electrocatalyst for HER.

  10. Capacitive deionization of NH{sub 4}CIO{sub 4} solutions with carbon aerogel electrodes. Revision 1

    SciTech Connect

    Farmer, J.C.; Fix, D.V.; Mack, G.V.; Pekala, R.W.; Poco, J.F.

    1996-01-01

    A process for capacitive deionization of water with a stack of carbon aerogel electrodes was developed. Unlike ion exchange, one of the more conventional deionization processes, no chemicals are required for regeneration of the system; electricity is used instead. An aqueous solution of NH{sub 4}ClO{sub 4} is pumped through the electrochemical cell. After polarization, NH{sub 4}{sup +} and ClO{sub 4}{sup -} ions are removed from the water by the imposed electric field and trapped in the extensive cathodic and anodic double layers. Thsi process produces one stream of purified water and a second stream of concentrate. Effects of cell voltage, salt concentration, and cycling on electrosorption capacity were studied and results reported.

  11. Aerogels derived from multifunctional organic monomers

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Kong, F.M.; Hulsey, S.S.

    1991-09-01

    Traditional inorganic aerogels are mad via the hydrolysis and condensation of metal alkoxides. Recently, we reported the synthesis of organic aerogels based upon the aqueous polycondensation of (1) resorcinol with formaldehyde and (2) melamine with formaldehyde. The former materials can also be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. In both the inorganic and organic systems, the structure and properties of the dried aerogel are dictated by polymerization conditions. Factors such as pH, reactant ratio, and temperature influence the crosslinking chemistry and growth processes taking place prior to gelation. The ability to tailor the structure and properties of aerogels at the nanometer scale opens up exciting possibilities for these novel materials. This paper addresses the chemistry-structure-property relationships of organic aerogels. 22 refs., 7 figs.

  12. Novel electrochemical dual-aptamer-based sandwich biosensor using molybdenum disulfide/carbon aerogel composites and Au nanoparticles for signal amplification.

    PubMed

    Fang, Lin-Xia; Huang, Ke-Jing; Liu, Yang

    2015-09-15

    A new electrochemical aptamer biosensor for the platelet-derived growth factor BB (PDGF-BB) detection has been developed based on the signal amplification of MoS2/carbon aerogel composites (MoS2/CA) and sandwich assay. A facile hydrothermal route assisted by L-cysteine was applied to synthesize CA incorporated flower-like MoS2 with the large surface active sites and good conductivity. The electrochemical aptasensor was constructed by sandwiching the PDGF-BB between a glassy carbon electrode modified with thiol-terminated PDGF-BB aptamer-1 (Apt1)/gold nanoparticles (AuNPs)/MoS2/CA and the AuNPs with thiol-terminated PDGF-BB aptamer-2 (Apt2) and 6-ferrocenyl hexanethiol (Fc). Fc-AuNPs-Apt2 acted as tracer and AuNPs/MoS2/CA were utilized as the biosensor platform to immobilize a large amount of capture aptamers, owing to their layered structure and high surface-to-volume ratio. Based on the sandwich format, a dual signal amplification strategy had been successfully developed with a wide linear response in the range of 0.001-10nM and a limit of detection of 0.3 pM. The developed assay demonstrated good selectivity and high sensitivity, indicating potential applications in bioanalysis and biomedicine.

  13. Polyolefin-based aerogels

    NASA Technical Reports Server (NTRS)

    Lee, Je Kyun (Inventor); Gould, Gerogle L. (Inventor)

    2010-01-01

    The present invention relates to cross-linked polyolefin aerogels in simple and fiber-reinforced composite form. Of particular interest are polybutadiene aerogels. Especially aerogels derived from polybutadienes functionalized with anhydrides, amines, hydroxyls, thiols, epoxies, isocyanates or combinations thereof.

  14. Synthesis and characterization of a nanocrystalline diamond aerogel

    SciTech Connect

    Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.; Laurence, Ted A.; Kilcoyne, A. L. David; Wang, Yinmin; Willey, Trevor M.; Visbeck, Kenneth S.; Fakra, Sirine C.; Evans, William J.; Zaug, Joseph M.; Satcher, Jr., Joe H.

    2011-07-06

    Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel's void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material reveal the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel.

  15. Aerogel: From Aerospace to Apparel

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Aspen Systems Inc. developed an aerogel-manufacturing process solved the handling problems associated with aerogel-based insulation products. Their aerogels can now be manufactured into blankets, thin sheets, beads, and molded parts; and may be transparent, translucent, or opaque. Aspen made the material effective for window and skylight insulation, non-flammable building insulation, and inexpensive firewall insulation that will withstand fires in homes and buildings, and also assist in the prevention of forest fires. Another Aspen product is Spaceloft(TM); an inexpensive, flexible blanket that incorporates a thin layer of aerogel embedded directly into the fabric. Spaceloft, is incorporated into jackets intended for wear in extremely harsh conditions and activities, such as Antarctic expeditions.

  16. Organic aerogel microspheres

    DOEpatents

    Mayer, S.T.; Kong, F.M.; Pekala, R.W.; Kaschmitter, J.L.

    1999-06-01

    Organic aerogel microspheres are disclosed which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonstick gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

  17. Organic aerogel microspheres

    DOEpatents

    Mayer, Steven T.; Kong, Fung-Ming; Pekala, Richard W.; Kaschmitter, James L.

    1999-01-01

    Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

  18. High-performance all-solid state asymmetric supercapacitor based on Co3O4 nanowires and carbon aerogel

    NASA Astrophysics Data System (ADS)

    Liu, Weiwei; Li, Xin; Zhu, Menghua; He, Xiong

    2015-05-01

    An all-solid state asymmetric supercapacitor has been fabricated using carbon aerogel (CA) microspheres as the negative electrode and Co3O4 nanowires on nickel foam (Co3O4-NF) as the positive electrode separated by PVA-KOH membrane as the electrolyte. For the desirable porous structure, high specific capacitance and rate capability of CA and Co3O4-NF, broader potential window of the two electrodes, no binder and conductive agent added, the asymmetric supercapacitor can be cycled reversibly in a wide potential window of 0-1.5 V with an energy density of 17.9 Wh kg-1 at a power density of 750 W kg-1. The energy density of the asymmetric supercapacitor is significantly improved in comparison with those of the symmetric supercapacitors based on CA (6.28 Wh kg-1) and Co3O4-NF (2.42 Wh kg-1). The asymmetric supercapacitor can also deliver a high energy density of 10.44 Wh kg-1, even at a high power density of 7.5 kW kg-1. In addition, the asymmetric device shows good stability with approximately 85% of its initial capacitance after 1000 cycles.

  19. Low density, resorcinol-formaldehyde aerogels

    DOEpatents

    Pekala, R.W.

    1988-05-26

    The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer ''clusters''. The covalent crosslinking of these ''clusters'' produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density less than or equal to100 mg/cc; cell size less than or equal to0.1 microns). The aerogels are transparent,dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 A/degree/. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron. 1 fig., 1 tab.

  20. Low density, resorcinol-formaldehyde aerogels

    DOEpatents

    Pekala, Richard W.

    1989-01-01

    The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density .ltoreq.100 mg/cc; cell size .ltoreq.0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 .ANG.. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.

  1. Low density, resorcinol-formaldehyde aerogels

    DOEpatents

    Pekala, R.W.

    1989-10-10

    The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer clusters. The covalent crosslinking of these clusters produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density [<=]100 mg/cc; cell size [<=]0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 [angstrom]. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.

  2. Low density, resorcinol-formaldehyde aerogels

    DOEpatents

    Pekala, Richard W.

    1991-01-01

    The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "Clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density.ltoreq.100 mg/cc; cell size .ltoreq.0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100.circle.. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.

  3. Particle Tracks in Aerogel

    NASA Technical Reports Server (NTRS)

    2005-01-01

    In an experiment using a special air gun, particles are shot into aerogel at high velocities. Closeup of particles that have been captured in aerogel are shown here. The particles leave a carrot-shaped trail in the aerogel. Aerogel was used on the Stardust spacecraft to capture comet particles from Comet Wild 2.

  4. Activated carbon from biomass

    NASA Astrophysics Data System (ADS)

    Manocha, S.; Manocha, L. M.; Joshi, Parth; Patel, Bhavesh; Dangi, Gaurav; Verma, Narendra

    2013-06-01

    Activated carbon are unique and versatile adsorbents having extended surface area, micro porous structure, universal adsorption effect, high adsorption capacity and high degree of surface reactivity. Activated carbons are synthesized from variety of materials. Most commonly used on a commercial scale are cellulosic based precursors such as peat, coal, lignite wood and coconut shell. Variation occurs in precursors in terms of structure and carbon content. Coir having very low bulk density and porous structure is found to be one of the valuable raw materials for the production of highly porous activated carbon and other important factor is its high carbon content. Exploration of good low cost and non conventional adsorbent may contribute to the sustainability of the environment and offer promising benefits for the commercial purpose in future. Carbonization of biomass was carried out in a horizontal muffle furnace. Both carbonization and activation were performed in inert nitrogen atmosphere in one step to enhance the surface area and to develop interconnecting porosity. The types of biomass as well as the activation conditions determine the properties and the yield of activated carbon. Activated carbon produced from biomass is cost effective as it is easily available as a waste biomass. Activated carbon produced by combination of chemical and physical activation has higher surface area of 2442 m2/gm compared to that produced by physical activation (1365 m2/gm).

  5. Preparation of Biopolymer Aerogels Using Green Solvents

    PubMed Central

    Subrahmanyam, Raman; Gurikov, Pavel; Meissner, Imke; Smirnova, Irina

    2016-01-01

    Although the first reports on aerogels made by Kistler1 in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m2/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm3), high specific surface area (350 - 500 m2/g) and pore volume (3 - 7 cm3/g for pore sizes less than 150 nm). PMID:27403649

  6. Preparation of Biopolymer Aerogels Using Green Solvents.

    PubMed

    Subrahmanyam, Raman; Gurikov, Pavel; Meissner, Imke; Smirnova, Irina

    2016-01-01

    Although the first reports on aerogels made by Kistler(1) in the 1930s dealt with aerogels from both inorganic oxides (silica and others) and biopolymers (gelatin, agar, cellulose), only recently have biomasses been recognized as an abundant source of chemically diverse macromolecules for functional aerogel materials. Biopolymer aerogels (pectin, alginate, chitosan, cellulose, etc.) exhibit both specific inheritable functions of starting biopolymers and distinctive features of aerogels (80-99% porosity and specific surface up to 800 m(2)/g). This synergy of properties makes biopolymer aerogels promising candidates for a wide gamut of applications such as thermal insulation, tissue engineering and regenerative medicine, drug delivery systems, functional foods, catalysts, adsorbents and sensors. This work demonstrates the use of pressurized carbon dioxide (5 MPa) for the ionic cross linking of amidated pectin into hydrogels. Initially a biopolymer/salt dispersion is prepared in water. Under pressurized CO2 conditions, the pH of the biopolymer solution is lowered to 3 which releases the crosslinking cations from the salt to bind with the biopolymer yielding hydrogels. Solvent exchange to ethanol and further supercritical CO2 drying (10 - 12 MPa) yield aerogels. Obtained aerogels are ultra-porous with low density (as low as 0.02 g/cm(3)), high specific surface area (350 - 500 m(2)/g) and pore volume (3 - 7 cm(3)/g for pore sizes less than 150 nm). PMID:27403649

  7. Composite ceria-coated aerogels and methods of making the same

    DOEpatents

    Eyring, Edward M; Ernst, Richard D; Turpin, Gregory C; Dunn, Brian C

    2013-05-07

    Ceria-coated aerogels can include an aerogel support material having a stabilized ceria coating thereon. The ceria coating can be formed by solution or vapor deposition of alcogels or aerogels. Additional catalytic metal species can also be incorporated into the coating to form multi-metallic compounds having improved catalytic activity. Further, the ceria coated aerogels retain high surface areas at elevated temperatures. Thus, improvements in catalytic activity and thermal stability can be achieved using these ceria-coated composite aerogels.

  8. Synthesis and characterization of a nanocrystalline diamond aerogel

    PubMed Central

    Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.; Laurence, Ted A.; Kilcoyne, A. L. David; Wang, Yinmin; Willey, Trevor M.; Visbeck, Kenneth S.; Fakra, Sirine C.; Evans, William J.; Zaug, Joseph M.; Satcher, Joe H.

    2011-01-01

    Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel’s void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material reveal the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel. PMID:21555550

  9. Biomass-Derived Heteroatom-Doped Carbon Aerogels from a Salt Melt Sol-Gel Synthesis and their Performance in Li-S Batteries.

    PubMed

    Schipper, Florian; Vizintin, Alen; Ren, Jiawen; Dominko, Robert; Fellinger, Tim-Patrick

    2015-09-21

    An ionothermal sol-gel strategy to synthesize hierarchically porous carbon aerogels doped with different heteroatoms is presented by using biomass precursors in a scalable process. Morphologically similar but chemically different materials are used to study the influence of heteroatoms in Li-S batteries. The materials show capacities as high as 1290 mAh g(-1) in the first cycle using 50 wt % S loading. Heteroatom doping reduces the capacity fading and the polarization throughout cycling. Zeta potential measurements reveal positive surface charges for heteroatom-doped carbons and indicate attractive interactions with polysulfides causing reduced fading. A polysulfide-selective sorption study reveals strongly different adsorption behavior depending on the carbon's chemical composition. Interestingly, the polysulfide fraction is also crucial. The results indicate that improved adsorption of long-chain polysulfides to doped carbons is related to improved capacity retention. PMID:26373362

  10. Removal of carbonaceous contaminants from silica aerogel

    NASA Technical Reports Server (NTRS)

    Huang, Hui-Ping; Gilmour, I.; Pillinger, C. T.; Zolensky, M. E.

    1993-01-01

    Capture of micrometeorite material from low Earth orbit or dust grains around active comets for return to terrestrial laboratories, capable of practicing the most up to date techniques of chemical isotopic and mineralogical analysis, will greatly enhance our knowledge of primitive material in the solar system. The next generation of space launched cosmic dust collectors will undoubtedly include extremely low density target materials such as silica aerogel as the decelerating and arresting medium. This material has been found to be clean from the point of view of inorganic elements and is thus acceptable for the purpose of harvesting grains to be studied by, for example PIXE, INAA, or SXRF. However, the process used in making aerogel leaves substantial carbon and hydrogen containing residues which would negate their suitability for collection and subsequent investigation of the very important CHON particles. Attempts to precondition aerogel by solvent extraction or heating at 500 C and 750 C in air for 24 hours or under a vacuum of 2(7)(exp -7) torr at 260 C were largely ineffective except that pyrolysis did reduce volatile species. In this investigation we have examined the use of supercritical fluids for the purpose of extracting organic residues. The logic of the new approach is that beyond the supercritical point a substance has the solvating properties of a liquid but the viscosity characteristics of a gas. For example carbon dioxide becomes supercritical at a pressure of 73 atmospheres and a temperature of 31 C; in consequence it can transform to a very powerful and ultraclean solvent. It can dissolve organic matter from low molecular weight up to molecules containing 90 carbon atoms. On release of pressure the fluid reverts to a gas which can easily be pumped away and removed from the substrate being extracted.

  11. Ruthenium / aerogel nanocomposits via Atomic Layer Deposition

    SciTech Connect

    Biener, J; Baumann, T F; Wang, Y; Nelson, E J; Kucheyev, S O; Hamza, A V; Kemell, M; Ritala, M; Leskela, M

    2006-08-28

    We present a general approach to prepare metal/aerogel nanocomposites via template directed atomic layer deposition (ALD). In particular, we used a Ru ALD process consisting of alternating exposures to bis(cyclopentadienyl)ruthenium (RuCp{sub 2}) and air at 350 C to deposit metallic Ru nanoparticles on the internal surfaces of carbon and silica aerogels. The process does not affect the morphology of the aerogel template and offers excellent control over metal loading by simply adjusting the number of ALD cycles. We also discuss the limitations of our ALD approach, and suggest ways to overcome these.

  12. Waterproofing Nanostructured Aerogel-Ceramic Fiber Composites

    NASA Technical Reports Server (NTRS)

    White, Susan; Hsu, Ming Ta; Arnold, Jim (Technical Monitor)

    2001-01-01

    Aerogels are nanoporous materials which can be used to enhance the transport properties of ceramic fiber materials, to exploit their unique properties such as high porosity, large surface area, low density and low thermal conductivity. Numerous applications have been investigated. major obstacle to commercialization is that the structure of aerogels collapses due to the adsorption of water. simple and relatively cheap process has been developed to waterproof silica, alumina and alumina-silica and carbon aerogels and composites incorporating them. Previous waterproofing methods are short lived or expensive and time consuming.

  13. Melamine-formaldehyde aerogels

    SciTech Connect

    Alviso, C.T.; Pekala, R.W.

    1991-04-01

    The ability to tailor the structure and properties of aerogels at the nanometer scale opens up exciting possibilities for these unique, low density materials. Traditional inorganic aerogels have been formed from the hydrolysis and condensation of metal alkoxides (e.g. tetramethoxy silane). Previously, we reported the synthesis of organic aerogels based upon the aqueous, polycondensation of resorcinol with formaldehyde. Although these aerogels exhibit minimal light scattering, their dark red color limits their use in certain optical applications. In this paper, we discuss the synthesis and characterization of melamine-formaldehyde aerogels -- a new type of organic aerogel that is both colorless and transparent. 16 refs., 3 figs., 1 tab.

  14. Flexible aerogel composite for mechanical stability and process of fabrication

    DOEpatents

    Coronado, Paul R.; Poco, John F.

    1999-01-01

    A flexible aerogel and process of fabrication. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4-5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  15. Flexible aerogel composite for mechanical stability and process of fabrication

    DOEpatents

    Coronado, Paul R.; Poco, John F.

    2000-01-01

    A flexible aerogel and process of fabrication. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4-5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  16. Flexible aerogel composite for mechanical stability and process of fabrication

    SciTech Connect

    Coronado, P.R.; Poco, J.F.

    1999-10-26

    A flexible aerogel and process of fabrication are disclosed. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4--5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  17. Flexible aerogel composite for mechanical stability and process of fabrication

    SciTech Connect

    Coronado, P.R.; Poco, J.F.

    2000-07-11

    A flexible aerogel and process of fabrication are disclosed. An aerogel solution is mixed with fibers in a mold and allowed to gel. The gel is then processed by supercritical extraction, or by air drying, to produce a flexible aerogel formed to the shape of the mold. The flexible aerogel has excellent thermal and acoustic properties, and can be utilized in numerous applications, such as for energy absorption, insulation (temperature and acoustic), to meet the contours of aircraft shapes, and where space is limited since an inch of aerogel is a 4--5 times better insulator than an inch of fiberglass. The flexible aerogel may be of an inorganic (silica) type or an organic (carbon) type, but containing fibers, such as glass or carbon fibers.

  18. Activated carbon material

    DOEpatents

    Evans, A. Gary

    1978-01-01

    Activated carbon particles for use as iodine trapping material are impregnated with a mixture of selected iodine and potassium compounds to improve the iodine retention properties of the carbon. The I/K ratio is maintained at less than about 1 and the pH is maintained at above about 8.0. The iodine retention of activated carbon previously treated with or coimpregnated with triethylenediamine can also be improved by this technique. Suitable flame retardants can be added to raise the ignition temperature of the carbon to acceptable standards.

  19. Aerogels for Thermal Insulation of Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeffrey; Fleurial, Jean-Pierre; Snyder, Jeffrey; Jones, Steven; Caillat, Thierry

    2006-01-01

    carbon black, which absorbs infrared radiation. Another example of an opacifier is micron- sized metal flakes, which reflect infrared radiation. Encapsulation in cast aerogel insulation also can help prolong the operational lifetimes of thermoelectric devices that must operate in vacuum and that contain SiGe or such advanced skutterudite thermoelectric materials as CoSb3 and CeFe3.5Co0.5Sb12. The primary cause of deterioration of most thermoelectric materials is thermal decomposition or sublimation (e.g., sublimation of Sb from CoSb3) at typical high operating temperatures. Aerogel present near the surface of CoSb3 can impede the outward transport of Sb vapor by establishing a highly localized, equilibrium Sb vapor atmosphere at the surface of the CoSb3.

  20. Aerogel Projects Ongoing in MSFC's Engineering Directorate

    NASA Technical Reports Server (NTRS)

    Shular, David A.; Smithers, Gweneth A.; Plawsky, Joel L.; Whitaker, Ann F. (Technical Monitor)

    2000-01-01

    When we speak of an aerogel material, we are referring more to process and structure am to a specific substance. Aerogel, considered the lightest solid material, has been made from silica for seventy years. Resorcinol-formaldehyde, organic aerogels have been developed more recently. However, aerogel can be made from almost any type of substance, even lead. Because an aerogel is mostly air (about 99 %), the solid substance used will affect the weight very little. The term "aerogel" connotes the sol-gel process used to manufacture the material. The aerogel begins as a liquid "sol," becomes a solid "alcogel," and is then dried to become an "aerogel." The final product has a unique structure, useful for exploitation. It is an "open pore" system with nano-sized particles and pores, has very high surface area, and is highly interconnected. Besides low weight, aerogels have ultimate (lowest) values in other properties: thermal conductivity, refractive index, sound speed, and dielectric constant. Aerogels were first prepared in 1931 by Steven Kistler, who used a supercritical drying step to replace the liquid in a gel with air, preserving the structure (1). Kistler's procedure involved a water-to-alcohol exchange step; in the 1970's, this step was eliminated when a French investigator introduced the use of tetramethylorthosilicate. Still, alcohol drying involved dangerously high temperatures and pressures. In the 1980's, the Microstructured Materials Group at Berkeley Laboratory found that the alcohol in the gel could be replaced with liquid carbon dioxide before supercritical drying, which greatly improved safety (2). 'Me most recent major contribution has been that of Deshpande, Smith and Brinker in New Mexico, who are working to eliminate the supercritical drying step (3). When aerogels were first being developed, they were evaporatively dried. However, the wet gel, when dried, underwent severe shrinkage and cracking; this product was termed "xerogel." When the

  1. Aerogel in Hand

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Though ghostly in appearance like an hologram, aerogel is very solid. It feels like hard styrofoam to the touch. Aerogel was used on the Stardust spacecraft to capture comet particles from Comet Wild 2.

  2. Melamine-formaldehyde aerogels

    SciTech Connect

    Pekala, R.W.

    1992-02-04

    This patent describes a composition of matter. It comprises: a low density, melamineformaldehyde (MF) aerogel which is transparent and essentially colorless, wherein the cell/pore sizes of the aerogel are less than or equal to 500 angstroms (A) and the density of the aerogel is from about 0.1 to 0.8 g/cc.

  3. Carbon black-derived graphene quantum dots composited with carbon aerogel as a highly efficient and stable reduction catalyst for the iodide/tri-iodide couple

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Chieh; Lu, Shih-Yuan

    2014-12-01

    A microwave-assisted oxidative cleavage process is developed to prepare graphene quantum dots (GQDs) from carbon black. The size evolution of the resulting carbonaceous products is studied. In one hour, GQDs of a size less than 10 nm and thickness less than 2 nm are obtained. These GQDs are further composited with mesoporous carbon aerogels (CA) by a filtration process to form GQD-decorated CA composites (GQD/CA). The GQD/CA composite is applied as a catalyst electrode for the reduction of I3- to I-, a critical electrolyte regeneration reaction in dye-sensitized solar cells (DSSCs). Also investigated are Pt electrodes, the expensive traditional counter electrode material for DSSCs, and plain CA electrodes for comparison. Based on data derived from cyclic voltammograms and Tafel plots, the GQD/CA composite exhibits catalytic efficiencies comparable to that of Pt electrodes and better than that of plain CA electrodes. The GQD/CA electrodes, however, surpass the Pt electrodes in terms of long-term stability. The cathodic current drops significantly after 500 cycles for the Pt and plain CA electrodes, whereas the cathodic current is slightly increased for the GQD/CA electrodes. The GQD/CA composite thus proves to be an inexpensive, efficient, and stable alternative to Pt as the counter electrode material for DSSCs.A microwave-assisted oxidative cleavage process is developed to prepare graphene quantum dots (GQDs) from carbon black. The size evolution of the resulting carbonaceous products is studied. In one hour, GQDs of a size less than 10 nm and thickness less than 2 nm are obtained. These GQDs are further composited with mesoporous carbon aerogels (CA) by a filtration process to form GQD-decorated CA composites (GQD/CA). The GQD/CA composite is applied as a catalyst electrode for the reduction of I3- to I-, a critical electrolyte regeneration reaction in dye-sensitized solar cells (DSSCs). Also investigated are Pt electrodes, the expensive traditional counter

  4. Mesoporous and biocompatible surface active silica aerogel synthesis using choline formate ionic liquid.

    PubMed

    Meera, Kamal Mohamed Seeni; Sankar, Rajavelu Murali; Jaisankar, Sellamuthu N; Mandal, Asit Baran

    2011-09-01

    In this paper, we report the preparation and characterization of mesoporous and biocompatible transparent silica aerogel by the sol-gel polymerization of tetraethyl orthosilicate using ionic liquid. Choline cation based ionic liquid allows the silica framework to form in a non collapsing environment and controls the pore size of the gel. FT-IR spectra reveal the interaction of ionic liquid with surface -OH of the gel. DSC thermogram giving the evidence of confinement of ionic liquid within the silica matrix, which helps to avoid the shrinkage of the gel during the aging process. Nitrogen sorption measurements of gel prepared with ionic liquid exhibit a low surface area of 100.53 m2/g and high average pore size of 3.74 nm. MTT assay proves the biocompatibility and cell viability of the prepared gels. This new nanoporous silica material can be applied to immobilize biological molecules, which may retain their stability over a longer period.

  5. Fracture, failure and compression behaviour of a 3D interconnected carbon aerogel (Aerographite) epoxy composite

    SciTech Connect

    Chandrasekaran, S.; Liebig, W. V.; Mecklenberg, M.; Fiedler, B.; Smazna, D.; Adelung, R.; Schulte, K.

    2015-11-04

    Aerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7–15 mg/cm3 was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. Our present study investigates the fracture and failure of AG/epoxy composites and its energy absorption capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ~133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on fracture toughness showed an enhancement of ~19% in KIC for AG/epoxy composites with 0.45 wt% of AG. Furthermore, our observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.

  6. Fracture, failure and compression behaviour of a 3D interconnected carbon aerogel (Aerographite) epoxy composite

    DOE PAGES

    Chandrasekaran, S.; Liebig, W. V.; Mecklenberg, M.; Fiedler, B.; Smazna, D.; Adelung, R.; Schulte, K.

    2015-11-04

    Aerographite (AG) is a mechanically robust, lightweight synthetic cellular material, which consists of a 3D interconnected network of tubular carbon [1]. The presence of open channels in AG aids to infiltrate them with polymer matrices, thereby yielding an electrical conducting and lightweight composite. Aerographite produced with densities in the range of 7–15 mg/cm3 was infiltrated with a low viscous epoxy resin by means of vacuum infiltration technique. Detailed morphological and structural investigations on synthesized AG and AG/epoxy composite were performed by scanning electron microscopic techniques. Our present study investigates the fracture and failure of AG/epoxy composites and its energy absorptionmore » capacity under compression. The composites displayed an extended plateau region when uni-axially compressed, which led to an increase in energy absorption of ~133% per unit volume for 1.5 wt% of AG, when compared to pure epoxy. Preliminary results on fracture toughness showed an enhancement of ~19% in KIC for AG/epoxy composites with 0.45 wt% of AG. Furthermore, our observations of fractured surfaces under scanning electron microscope gives evidence of pull-out of arms of AG tetrapod, interface and inter-graphite failure as the dominating mechanism for the toughness improvement in these composites. These observations were consistent with the results obtained from photoelasticity experiments on a thin film AG/epoxy model composite.« less

  7. Efficient Fabrication of Hierarchically Porous Graphene-Derived Aerogel and Its Application in Lithium Sulfur Battery.

    PubMed

    Zhang, Kai; Qin, Furong; Lai, Yanqing; Li, Jie; Lei, Xiaoke; Wang, Mengran; Lu, Hai; Fang, Jing

    2016-03-01

    Hierarchically porous carbon/graphene aerogel (CGA) with relatively high surface area and pore volume is synthesized through an efficient fabrication strategy, which involves forming hydrothermal carbon layer on the pore wall as upholder and directly carbonizing the wet hydrogel from hydrothermal reaction, without using any special drying techniques. Cassava powder is used as carbon precursor which enables sustainable synthesis. Carbonizing the wet hydrothermal product is found to be a self-activation process, through which abundant pores are generated. The aerogel is used as host to encapsulate sulfur for lithium sulfur battery. Graphene, served as highly conductive scaffold, accelerates the transport of the electrons. The hierarchically porous structure is in favor of improving the electrochemical performance of lithium sulfur battery. Therefore, the cathode with high sulfur loading and high sulfur content can deliver very good performance. PMID:26885723

  8. Efficient Fabrication of Hierarchically Porous Graphene-Derived Aerogel and Its Application in Lithium Sulfur Battery.

    PubMed

    Zhang, Kai; Qin, Furong; Lai, Yanqing; Li, Jie; Lei, Xiaoke; Wang, Mengran; Lu, Hai; Fang, Jing

    2016-03-01

    Hierarchically porous carbon/graphene aerogel (CGA) with relatively high surface area and pore volume is synthesized through an efficient fabrication strategy, which involves forming hydrothermal carbon layer on the pore wall as upholder and directly carbonizing the wet hydrogel from hydrothermal reaction, without using any special drying techniques. Cassava powder is used as carbon precursor which enables sustainable synthesis. Carbonizing the wet hydrothermal product is found to be a self-activation process, through which abundant pores are generated. The aerogel is used as host to encapsulate sulfur for lithium sulfur battery. Graphene, served as highly conductive scaffold, accelerates the transport of the electrons. The hierarchically porous structure is in favor of improving the electrochemical performance of lithium sulfur battery. Therefore, the cathode with high sulfur loading and high sulfur content can deliver very good performance.

  9. Diffusion and adsorption of methane confined in nanoporous carbon aerogel: a combined quasi-elastic and small-angle neutron scattering study

    SciTech Connect

    Mavila Chathoth, Suresh; Mamontov, Eugene; Melnichenko, Yuri B; Zamponi, Michaela M

    2010-01-01

    The diffusion of methane confined in nano-porous carbon aerogel with the average pore size 48 {angstrom} and porosity 60% was investigated as a function of pressure at T = 298 K using quasi-elastic neutron scattering (QENS). The diffusivity of methane shows a clear effect of confinement: it is about two orders of magnitude lower than in bulk at the same thermodynamic conditions and is close to the diffusivity of liquid methane at 100 K (i.e. {approx} 90 K below the liquid-gas critical temperature T{sub C} {approx} 191 K). The diffusion coefficient (D) of methane initially increases with pressure by a factor of {approx}2.5 from 3.47 {+-} 0.41 x 10{sup -10} m{sup 2} s{sup -1} at 0.482 MPa to D = 8.55 {+-} 0.33 x 10{sup -10} m{sup 2} s{sup -1} at 2.75 MPa and starts to decrease at higher pressures. An explanation of the observed non-monotonic behavior of the diffusivity in the confined fluid is based on the results of small-angle neutron scattering experiments of the phase behavior of methane in a similar carbon aerogel sample. The initial increase of the diffusion coefficient with pressure is explained as due to progressive filling of bigger pores in which molecular mobility in the internal pore volume is less affected by the sluggish liquid-like molecular mobility in the adsorbed phase. Subsequent decrease of D, is associated with the effect of intermolecular collisions, which result in a lower total molecular mobility with pressure, as in the bulk state. The results are compared with the available QENS data on the methane diffusivity in zeolites, metal organic frameworks, and porous silica as well as with the molecular dynamics simulations of methane in nano-porous carbons and silica zeolites.

  10. Polyimide Aerogel Thin Films

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann; Guo, Haiquan

    2012-01-01

    Polyimide aerogels have been crosslinked through multifunctional amines. This invention builds on "Polyimide Aerogels With Three-Dimensional Cross-Linked Structure," and may be considered as a continuation of that invention, which results in a polyimide aerogel with a flexible, formable form. Gels formed from polyamic acid solutions, end-capped with anhydrides, and cross-linked with the multifunctional amines, are chemically imidized and dried using supercritical CO2 extraction to give aerogels having density around 0.1 to 0.3 g/cubic cm. The aerogels are 80 to 95% porous, and have high surface areas (200 to 600 sq m/g) and low thermal conductivity (as low as 14 mW/m-K at room temperature). Notably, the cross-linked polyimide aerogels have higher modulus than polymer-reinforced silica aerogels of similar density, and can be fabricated as both monoliths and thin films.

  11. Ambient Dried Aerogels

    NASA Technical Reports Server (NTRS)

    Jones, Steven M.; Paik, Jong-Ah

    2013-01-01

    A method has been developed for creating aerogel using normal pressure and ambient temperatures. All spacecraft, satellites, and landers require the use of thermal insulation due to the extreme environments encountered in space and on extraterrestrial bodies. Ambient dried aerogels introduce the possibility of using aerogel as thermal insulation in a wide variety of instances where supercritically dried aerogels cannot be used. More specifically, thermoelectric devices can use ambient dried aerogel, where the advantages are in situ production using the cast-in ability of an aerogel. Previously, aerogels required supercritical conditions (high temperature and high pressure) to be dried. Ambient dried aerogels can be dried at room temperature and pressure. This allows many materials, such as plastics and certain metal alloys that cannot survive supercritical conditions, to be directly immersed in liquid aerogel precursor and then encapsulated in the final, dried aerogel. Additionally, the metalized Mylar films that could not survive the previous methods of making aerogels can survive the ambient drying technique, thus making multilayer insulation (MLI) materials possible. This results in lighter insulation material as well. Because this innovation does not require high-temperature or high-pressure drying, ambient dried aerogels are much less expensive to produce. The equipment needed to conduct supercritical drying costs many tens of thousands of dollars, and has associated running expenses for power, pressurized gasses, and maintenance. The ambient drying process also expands the size of the pieces of aerogel that can be made because a high-temperature, high-pressure system typically has internal dimensions of up to 30 cm in diameter and 60 cm in height. In the case of this innovation, the only limitation on the size of the aerogels produced would be in the ability of the solvent in the wet gel to escape from the gel network.

  12. High resolution transmission electron microscopy of melamine-formaldehyde aerogels and silica aerogels

    SciTech Connect

    Ruben, G.C. . Dept. of Biological Sciences)

    1991-09-01

    The goal of the high resolution transmission electron microscopy (HRTEM) was to image the structure of two tetramethyl orthosilicate (TMOS) and two melamine-formaldehyde (MF) aerogels at the single polymer chain level{sup 1,2}. With this level of structural resolution we hoped to interrelate each aerogel's structure with its physical properties and its method of synthesis. Conventional single-step base catalysed TMOS aerogels show strings of spheroidal particles linked together with minimal necking. The spheroidal particles range from 86--132 {Angstrom} and average 113{plus minus}10 {Angstrom} in diameter{sup 2}. In contrast the TMOS aerogels reported on here were made by a two step method. After extended silica chains are grown in solution under acidic conditions with a substoichiometric amount of water, the reaction is stopped and the methanol hydrolysed from TMOS is removed. Then base catalysis and additional water are added to cause gel formation is a nonalcoholic solvent. The MF aerogels were prepared for HRTEM by fracturing them on a stereo microscope stage with razor knife so that fractured pieces with smooth flat surfaces could be selected for platinum-carbon replication. The two silica (TMOS) aerogels were both transparent and difficult to see. These aerogels were fractured on a stereo microscope stage with tweezers. 6 refs., 4 figs.

  13. 3D dual-confined sulfur encapsulated in porous carbon nanosheets and wrapped with graphene aerogels as a cathode for advanced lithium sulfur batteries

    NASA Astrophysics Data System (ADS)

    Hou, Yang; Li, Jianyang; Gao, Xianfeng; Wen, Zhenhai; Yuan, Chris; Chen, Junhong

    2016-04-01

    Although lithium-sulfur (Li-S) batteries have attracted much attention due to their high theoretical specific energy and low cost, their practical applications have been severely hindered by poor cycle life, inadequate sulfur utilization, and the insulating nature of sulfur. Here, we report a rationally designed Li-S cathode with a dual-confined configuration formed by confining sulfur in 2D carbon nanosheets with an abundant porous structure followed by 3D graphene aerogel wrapping. The porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, providing pathways for rapid electron/ion transport and preventing polysulfide dissolution. As a result, the hybrid electrode exhibits superior electrochemical performance, including a large reversible capacity of 1328 mA h g-1 in the first cycle, excellent cycling stability (maintaining a reversible capacity of 647 mA h g-1 at 0.2 C after 300 cycles) with nearly 100% Coulombic efficiency, and a high rate capability of 512 mA h g-1 at 8 C for 30 cycles, which is among the best reported rate capabilities.Although lithium-sulfur (Li-S) batteries have attracted much attention due to their high theoretical specific energy and low cost, their practical applications have been severely hindered by poor cycle life, inadequate sulfur utilization, and the insulating nature of sulfur. Here, we report a rationally designed Li-S cathode with a dual-confined configuration formed by confining sulfur in 2D carbon nanosheets with an abundant porous structure followed by 3D graphene aerogel wrapping. The porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, providing pathways for rapid electron/ion transport and preventing polysulfide dissolution. As a result, the hybrid electrode exhibits superior

  14. Organic aerogels: A new type of ultrastructured polymer

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; LeMay, J.D.

    1991-02-01

    Organic aerogels with different ultrastructures can be successfully synthesized from the aqueous sol-gel polymerization of (1) resorcinol with formaldehyde or (2) melamine with formaldehyde. In addition, RF aerogels can be pyrolyzed in an inert atmosphere to give vitreous carbon aerogels. The (resorcinol)/(sodium carbonate) ratio is the major variable in the RF polymerization while pH and acid type regulate the MF polymerization. Mechanical property, TEM, and surface area data provide evidence that organic aerogels are similar to their silica counterparts. Based upon these data, we are continuing to explore commonalities between inorganic and organic aerogels so that a universal model might be developed for the structure and properties of these unique materials. Such a model would have a major impact upon the materials science community by opening up new routes for the nanodesign of microporous materials with novel compositions, ultrastructures, and properties. 33 refs., 8 figs.

  15. Hydrogen crystallization in low-density aerogels.

    PubMed

    Kucheyev, S O; Van Cleve, E; Johnston, L T; Gammon, S A; Worsley, M A

    2015-04-01

    Crystallization of liquids confined in disordered low-density nanoporous scaffolds is poorly understood. Here, we use relaxation calorimetry to study the liquid-solid phase transition of H2 in a series of silica and carbon (nanotube- and graphene-based) aerogels with porosities ≳94%. Results show that freezing temperatures of H2 inside all the aerogels studied are depressed but do not follow predictions of the Gibbs-Thomson theory based on average pore diameters measured by conventional gas sorption techniques. Instead, we find that, for each material family investigated, the depression of average freezing temperatures scales linearly with the ratio of the internal surface area (measured by gas sorption) and the total pore volume derived from the density of aerogel monoliths. The slope of such linear dependences is, however, different for silica and carbon aerogels, which we attribute to microporosity of carbons and the presence of macropores in silica aerogels. Our results have important implications for the analysis of pore size distributions of low-density nanoporous materials and for controlling crystallization of fuel layers in targets for thermonuclear fusion energy applications. PMID:25781182

  16. Technical applications of aerogels

    SciTech Connect

    Hrubesh, L.W.

    1997-08-18

    Aerogel materials posses such a wide variety of exceptional properties that a striking number of applications have developed for them. Many of the commercial applications of aerogels such as catalysts, thermal insulation, windows, and particle detectors are still under development and new application as have been publicized since the ISA4 Conference in 1994: e.g.; supercapacitors, insulation for heat storage in automobiles, electrodes for capacitive deionization, etc. More applications are evolving as the scientific and engineering community becomes familiar with the unusual and exceptional physical properties of aerogels, there are also scientific and technical application, as well. This paper discusses a variety of applications under development at Lawrence Livermore National Laboratory for which several types of aerogels are formed in custom sizes and shapes. Particular discussions will focus on the uses of aerogels for physics experiments which rely on the exceptional, sometimes unique, properties of aerogels.

  17. Ceramic Aerogel Composite Materials and Characterization

    NASA Technical Reports Server (NTRS)

    White, Susan; Hrubesh, Lawrence W.; Rasky, Daniel J. (Technical Monitor)

    1997-01-01

    Aerogels a.k.a "Solid Smoke" are gels with the liquid phase replaced by gas, leaving behind a highly porous material with a nanoscale framework. Due to the porous, nanoscale structure, aerogels have the lowest known density and conductivity of solids. Aerogels have the potential for being a breakthrough material because of their extremely light weight and unique properties. In this paper, we address overcoming their most profound weaknesses: mechanical fragility and very high surface activity, which leads to a lowered sintering temperature. A matrix of ceramic aerogel composite materials was produced to investigate their properties and functionality. Mechanical property measurements and Scanning Electron Micrographs are used to identify trends and structure of these ceramic composite materials. Thermal cycling was used to identify the sintering points of the materials.

  18. Method of casting aerogels

    SciTech Connect

    Poco, J.F.

    1993-09-07

    The invention describes a method for making monolithic castings of transparent silica aerogel with densities in the range from 0.001 g/cm[sup 3] to 0.6 g/cm[sup 3]. Various shapes of aerogels are cast in flexible polymer molds which facilitate removal and eliminate irregular surfaces. Mold dimensions are preselected to account for shrinkage of aerogel which occurs during the drying step of supercritical extraction of solvent. 2 figures.

  19. Aerogel-supported filament

    DOEpatents

    Wuest, C.R.; Tillotson, T.M.; Johnson, C.V. III

    1995-05-16

    The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces. 6 Figs.

  20. Aerogel-supported filament

    DOEpatents

    Wuest, Craig R.; Tillotson, Thomas M.; Johnson, III, Coleman V.

    1995-01-01

    The present invention is a thin filament embedded in a low density aerogel for use in radiation detection instruments and incandescent lamps. The aerogel provides a supportive matrix that is thermally and electrically nonconductive, mechanically strong, highly porous, gas-permeable, and transparent to ionizing radiation over short distances. A low density, open-cell aerogel is cast around a fine filament or wire, which allows the wire to be positioned with little or no tension and keeps the wire in place in the event of breakage. The aerogel support reduces the stresses on the wire caused by vibrational, gravitational, electrical, and mechanical forces.

  1. Aerogel derived catalysts

    SciTech Connect

    Reynolds, J. G., LLNL

    1996-12-11

    Aerogels area class of colloidal materials which have high surface areas and abundant mesoporous structure. SiO{sub 2} aerogels show unique physical, optical and structural properties. When catalytic metals are incorporated in the aerogel framework, the potential exists for new and very effective catalysts for industrial processes. Three applications of these metal-containing SiO{sub 2} aerogels as catalysts are briefly reviewed in this paper--NO{sub x} reduction, volatile organic compound destruction, and partial oxidation of methane.

  2. 3D dual-confined sulfur encapsulated in porous carbon nanosheets and wrapped with graphene aerogels as a cathode for advanced lithium sulfur batteries.

    PubMed

    Hou, Yang; Li, Jianyang; Gao, Xianfeng; Wen, Zhenhai; Yuan, Chris; Chen, Junhong

    2016-04-21

    Although lithium-sulfur (Li-S) batteries have attracted much attention due to their high theoretical specific energy and low cost, their practical applications have been severely hindered by poor cycle life, inadequate sulfur utilization, and the insulating nature of sulfur. Here, we report a rationally designed Li-S cathode with a dual-confined configuration formed by confining sulfur in 2D carbon nanosheets with an abundant porous structure followed by 3D graphene aerogel wrapping. The porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, providing pathways for rapid electron/ion transport and preventing polysulfide dissolution. As a result, the hybrid electrode exhibits superior electrochemical performance, including a large reversible capacity of 1328 mA h g(-1) in the first cycle, excellent cycling stability (maintaining a reversible capacity of 647 mA h g(-1) at 0.2 C after 300 cycles) with nearly 100% Coulombic efficiency, and a high rate capability of 512 mA h g(-1) at 8 C for 30 cycles, which is among the best reported rate capabilities. PMID:27029963

  3. Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity

    PubMed Central

    Harper-Leatherman, Amanda S.; Pacer, Elizabeth R.; Kosciuszek, Nina D.

    2016-01-01

    Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol–gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development. PMID:26967257

  4. Encapsulating Cytochrome c in Silica Aerogel Nanoarchitectures without Metal Nanoparticles while Retaining Gas-phase Bioactivity.

    PubMed

    Harper-Leatherman, Amanda S; Pacer, Elizabeth R; Kosciuszek, Nina D

    2016-01-01

    Applications such as sensors, batteries, and fuel cells have been improved through the use of highly porous aerogels when functional compounds are encapsulated within the aerogels. However, few reports on encapsulating proteins within sol-gels that are processed to form aerogels exist. A procedure for encapsulating cytochrome c (cyt. c) in silica (SiO2) sol-gels that are supercritically processed to form bioaerogels with gas-phase activity for nitric oxide (NO) is presented. Cyt. c is added to a mixed silica sol under controlled protein concentration and buffer strength conditions. The sol mixture is then gelled and the liquid filling the gel pores is replaced through a series of solvent exchanges with liquid carbon dioxide. The carbon dioxide is brought to its critical point and vented off to form dry aerogels with cyt. c encapsulated inside. These bioaerogels are characterized with UV-visible spectroscopy and circular dichroism spectroscopy and can be used to detect the presence of gas-phase nitric oxide. The success of this procedure depends on regulating the cyt. c concentration and the buffer concentration and does not require other components such as metal nanoparticles. It may be possible to encapsulate other proteins using a similar approach making this procedure important for potential future bioanalytical device development. PMID:26967257

  5. Determining activated carbon performance

    SciTech Connect

    Naylor, W.F.; Rester, D.O.

    1995-07-01

    This article discusses the key elements involved in evaluating a system`s performance. Empty bed contact time (EBCT) is a term used to describe the length of time a liquid stream being treated is in contact with a granular activated carbon bed. The EBCT is the time required for a fluid to pass through the volume equivalent of the media bed, without the media being present. In a bed of granular activated carbon, the void volume or space between particles is usually about 45 percent. Therefore, the EBCT is about twice the true or actual time of contact between the fluid being treated and the GAC particles. The EBCT plays an important role in determining the effectiveness and longevity of granular activated carbon (GAC) used to treat liquids in a fixed-bed adsorber. Factors that influence and are influenced by EBCT, and their relationship to GAC performance in a treatment scheme include: adsorption, mass transfer zone, impurity concentration, adsorption affinity, flow rate and system design considerations.

  6. Method of manufacturing aerogel composites

    DOEpatents

    Cao, W.; Hunt, A.J.

    1999-03-09

    Disclosed herewith is a process of forming an aerogel composite which comprises introducing a gaseous material into a formed aerogel monolith or powder, and causing decomposition of said gaseous material in said aerogel in amounts sufficient to cause deposition of the decomposition products of the gas on the surfaces of the pores of the said aerogel.

  7. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, Gregory A.; Hrubesh, Lawrence W.; Poco, John F.; Sandler, Pamela H.

    1997-01-01

    An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency.

  8. Aerogel-clad optical fiber

    DOEpatents

    Sprehn, G.A.; Hrubesh, L.W.; Poco, J.F.; Sandler, P.H.

    1997-11-04

    An optical fiber is surrounded by an aerogel cladding. For a low density aerogel, the index of refraction of the aerogel is close to that of air, which provides a high numerical aperture to the optical fiber. Due to the high numerical aperture, the aerogel clad optical fiber has improved light collection efficiency. 4 figs.

  9. Method of manufacturing aerogel composites

    DOEpatents

    Cao, Wanqing; Hunt, Arlon Jason

    1999-01-01

    Disclosed herewith is a process of forming an aerogel composite which comprises introducing a gaseous material into a formed aerogel monolith or powder, and causing decomposition of said gaseous material in said aerogel in amounts sufficient to cause deposition of the decomposition products of the gas on the surfaces of the pores of the said aerogel.

  10. Melamine-formaldehyde aerogels

    DOEpatents

    Pekala, Richard W.

    1992-01-01

    Organic aerogels that are transparent and essentially colorless are prepa from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porsity, ultrafine cell/pore sizes, and optical clarity.

  11. Comet Ejecta in Aerogel

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on image for annotated image

    This image shows a particle impact on the aluminum frame that holds the aerogel tiles. The debris from the impact shot into the adjacent aerogel tile producing the explosion pattern of ejecta framents captured in the material. A nice cratering experiment.

  12. Dielectric properties of aerogels

    SciTech Connect

    Hrubesh, L.W.; Keene, L.E.; Latorre, V.R. )

    1993-07-01

    We have measured the real (dielectric constant) and imaginary (loss factor) components of the complex relative permittivity at 298 [degree]K using microwave frequencies (2, 10, and 18--40 GHz), for bulk SiO[sub 2]-aerogels and for two types of organic aerogels, resorcinol-formaldehyde (RF) and melamine-formaldehyde (MF). Measured dielectric constants are found to vary linearly between values of 1.0 and 2.0 for aerogel densities from 10 to 500 kg/m[sup 3]. For the same range of densities, the measured loss tangents vary linearly between values of 2[times]10[sup [minus]4] and 7[times]10[sup [minus]2]. The observed linearity of the dielectric properties with density in aerogels at microwave frequencies shows that their dielectric behavior is more gas-like than solid-like. The dielectric properties of aerogels are shown to be significantly affected by the adsorbed water internal to the bulk material. For example, water accounts for 7% of the dielectric constant and 70% of the loss at microwave frequencies for silica aerogels. Because of their very high porosity, even with the water content, the aerogels are among the few materials exhibiting such low dielectric properties. Our measurements show that aerogels with greater than 99% porosity have dielectric constants less than 1.03; these are the lowest values ever reported for a bulk solid material.

  13. Melamine-formaldehyde aerogels

    SciTech Connect

    Pekala, R.W.

    1992-01-14

    Organic aerogels that are transparent and essentially colorless are prepared from the aqueous, sol-gel polymerization of melamine with formaldehyde. The melamine-formaldehyde (MF) aerogels have low densities, high surface areas, continuous porosity, ultrafine cell/pore sizes, and optical clarity. 3 figs.

  14. Aerogels for electronics

    SciTech Connect

    Hrubesh, L.W.

    1994-10-01

    In addition to their other exceptional properties, aerogels also exhibit unusual dielectric and electronic properties due to their nano-sized structures and high porosities. For example, aerogels have the lowest dielectric constants measured for a solid material (having values approaching 1.0); they have exceptionally high dielectric resistivities and strengths (i.e., ability to insulate very high voltages); they exhibit low dielectric loss at microwave frequencies; and some aerogels are electrically conductive and photoconductive. These properties are being exploited to provide the next generation of materials for energy storage, low power consumption, and ultra-fast electronics. We are working toward adapting these unusual materials for microelectronic applications, particularly, making thin aerogel films for dielectric substrates and for energy storage devices such as supercapacitors. Measurements are presented in this paper for the dielectric and electronic properties of aerogels, including the dielectric constant, loss factor, dielectric and electrical conductivity, volume resistivity, and dielectric strength. We also describe methods to form and characterize thin aerogel films which are being developed for numerous electronic applications. Finally, some of the electronic applications proposed for aerogels are presented. Commercialization of aerogels for electronics must await further feasibility, prototype development, and cost studies, but they are one of the key materials and are sure to have a major impact on future electronics.

  15. Epoxy Crosslinked Silica Aerogels (X-Aerogels)

    NASA Technical Reports Server (NTRS)

    fabrizio, Eve; Ilhan, Faysal; Meador, Mary Ann; Johnston, Chris; Leventis, Nicholas

    2004-01-01

    NASA is interested in the development of strong lightweight materials for the dual role of thermal insulator and structural component for space vehicles; freeing more weight for useful payloads. Aerogels are very-low density materials (0.010 to 0.5 g/cc) that, due to high porosity (meso- and microporosity), can be, depending on the chemical nature of the network, ideal thermal insulators (thermal conductivity approx. 15 mW/mK). However, aerogels are extremely fragile. For practical application of aerogels, one must increase strength without compromising the physical properties attributed to low density. This has been achieved by templated growth of an epoxy polymer layer that crosslinks the "pearl necklace" network of nanoparticles: the framework of a typical silica aerogel. The requirement for conformal accumulation of the epoxy crosslinker is reaction both with the surface of silica and with itself. After cross-linking, the strength of a typical aerogel monolith increases by a factor of 200, in the expense of only a 2-fold increase in density. Strength is increased further by coupling residual unreacted epoxides with diamine.

  16. Reducing Logistics Footprints and Replenishment Demands: Nano-engineered Silica Aerogels a Proven Method for Water Treatment

    SciTech Connect

    Daily, W; Coleman, S; Love, A; Reynolds, J; O'Brien, K; Gammon, S

    2004-09-22

    Rapid deployment and the use of objective force aggressively reduce logistic footprints and replenishment demands. Maneuver Sustainment requires that Future Combat Systems be equipped with water systems that are lightweight, have small footprints, and are highly adaptable to a variety of environments. Technologies employed in these settings must be able to meet these demands. Lawrence Livermore National Laboratory has designed and previously field tested nano-engineered materials for the treatment of water. These materials have been either based on silica aerogel materials or consist of composites of these aerogels with granular activated carbon (GAC). Recent tests have proven successful for the removal of contaminants including uranium, hexavalent chromium, and arsenic. Silica aerogels were evaluated for their ability to purify water that had been spiked with the nerve agent VX (O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate). These results demonstrated that silica aerogels were able to remove the VX from the supply water and were nearly 30 times more adsorbent than GAC. This performance could result in REDUCING CHANGEOUT FREQUENCY BY A FACTOR OF 30 or DECREASING the VOLUME of adsorbent BY A FACTOR OF 30; thereby significantly reducing logistic footprints and replenishment demands. The use of the nano-engineered Silica Aerogel/GAC composites would provide a water purification technology that meets the needs of Future Combat Systems.

  17. Incorporation of noble metals into aerogels

    DOEpatents

    Hair, Lucy M.; Sanner, Robert D.; Coronado, Paul R.

    1998-01-01

    Aerogels or xerogels containing atomically dispersed noble metals for applications such environmental remediation. New noble metal precursors, such as Pt--Si or Pd(Si--P).sub.2, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

  18. Incorporation of noble metals into aerogels

    DOEpatents

    Hair, L.M.; Sanner, R.D.; Coronado, P.R.

    1998-12-22

    Aerogels or xerogels containing atomically dispersed noble metals for applications such as environmental remediation are disclosed. New noble metal precursors, such as Pt--Si or Pd(Si--P){sub 2}, have been created to bridge the incompatibility between noble metals and oxygen, followed by their incorporation into the aerogel or xerogel through sol-gel chemistry and processing. Applications include oxidation of hydrocarbons and reduction of nitrogen oxide species, complete oxidation of volatile organic carbon species, oxidative membranes for photocatalysis and partial oxidation for synthetic applications.

  19. Mechanical Properties of Aerogels

    NASA Technical Reports Server (NTRS)

    Parmenter, Kelly E.; Milstein, Frederick

    1995-01-01

    Aerogels are extremely low density solids that are characterized by a high porosity and pore sizes on the order of nanometers. Their low thermal conductivity and sometimes transparent appearance make them desirable for applications such as insulation in cryogenic vessels and between double paned glass in solar architecture. An understanding of the mechanical properties of aerogels is necessary before aerogels can be used in load bearing applications. In the present study, the mechanical behavior of various types of fiber-reinforced silica aerogels was investigated with hardness, compression, tension and shear tests. Particular attention was paid to the effects of processing parameters, testing conditions, storage environment, and age on the aerogels' mechanical response. The results indicate that the addition of fibers to the aerogel matrix generally resulted in softer, weaker materials with smaller elastic moduli. Furthermore, the testing environment significantly affected compression results. Tests in ethanol show an appreciable amount of scatter, and are not consistent with results for tests in air. In fact, the compression specimens appeared to crack and begin to dissolve upon exposure to the ethanol solution. This is consistent with the inherent hydrophobic nature of these aerogels. In addition, the aging process affected the aerogels' mechanical behavior by increasing their compressive strength and elastic moduli while decreasing their strain at fracture. However, desiccation of the specimens did not appreciably affect the mechanical properties, even though it reduced the aerogel density by removing trapped moisture. Finally, tension and shear test results indicate that the shear strength of the aerogels exceeds the tensile strength. This is consistent with the response of brittle materials. Future work should concentrate on mechanical testing at cryogenic temperatures, and should involve more extensive tensile tests. Moreover, before the mechanical response

  20. Advanced Aerogel Technology

    NASA Technical Reports Server (NTRS)

    Jones, Steven

    2013-01-01

    The JPL Aerogel Laboratory has made aerogels for NASA flight missions, e.g., Stardust, 2003 Mars Exploration Rovers and the 2011 Mars Science Laboratory, as well as NASA research projects for the past 14 years. During that time it has produced aerogels of a range of shapes, sizes, densities and compositions. Research is ongoing in the development of aerogels for future sample capture and return missions and for thermal insulation for both spacecraft and scientific instruments. For the past several years, the JPL Aerogel Laboratory has been developing, producing and testing a new composite material for use as the high temperature thermal insulation in the Advanced Sterling Radioisotope Generator (ASRG) being developed by Lockheed Martin and NASA. The composite is made up of a glass fiber felt, silica aerogel, Titania powder, and silica powder. The oxide powders are included to reduce irradiative heat transport at elevated temperatures. These materials have thermal conductivity values that are the same as the best commercially produced high temperature insulation materials, and yet are 40% lighter. By greatly reducing the amount of oxide powder in the composite, the density, and therefore for the value of the thermal conductivity, would be reduced. The JPL Aerogel Laboratory has experimented with using glass fiber felt, expanded glass fiber felt and loose fibers to add structural integrity to silica aerogels. However, this work has been directed toward high temperature applications. By conducting a brief investigation of the optimal combination of fiber reinforcement and aerogel density, a durable, extremely efficient thermal insulation material for ambient temperature applications would be produced. If a transparent thermal insulation is desired, then aerogel is an excellent candidate material. At typical ambient temperatures, silica aerogel prevents the transport of heat via convection and conduction due to its highly porous nature. To prevent irradiative thermal

  1. Dewatering Peat With Activated Carbon

    NASA Technical Reports Server (NTRS)

    Rohatgi, N. K.

    1984-01-01

    Proposed process produces enough gas and carbon to sustain itself. In proposed process peat slurry is dewatered to approximately 40 percent moisture content by mixing slurry with activated carbon and filtering with solid/liquid separation techniques.

  2. Method of patterning an aerogel

    DOEpatents

    Reed, Scott T.

    2012-07-24

    A method for producing a pattern in an aerogel disposed as a coating on a substrate comprises exposing the aerogel coating to the vapors of a hydrophobic silane compound, masking the aerogel coating with a shadow photomask and irradiating the aerogel coating with ultraviolet (UV) irradiation. The exposure to UV through the shadow mask creates a pattern of hydrophobic and hydrophilic regions in the aerogel coating. Etching away the hydrophilic regions of the aerogel coating, preferably with a 1 molar solution of sodium hydroxide, leaves the unwetted and unetched hydrophobic regions of the aerogel layer on the substrate, replicating the pattern of the photomask. The hydrophobic aerogel pattern can be further exposed to UV irradiation if desired, to create a hydrophilic aerogel pattern.

  3. Design of a novel Cu₂O/TiO₂/carbon aerogel electrode and its efficient electrosorption-assisted visible light photocatalytic degradation of 2,4,6-trichlorophenol.

    PubMed

    Wang, Yabo; Zhang, Ya-Nan; Zhao, Guohua; Tian, Hongyi; Shi, Huijie; Zhou, Tianchen

    2012-08-01

    Cu(2)O/TiO(2) heterojunction photocatalyst is built on carbon aerogel (CA) substrate with good adsorption properties by sol impregnation and seed-mediated synthesis approach. The Cu(2)O/TiO(2)/CA electrode has excellent electrosorptive and high efficient photocatalytic properties. Its morphology and surface chemical composition are characterized with SEM, TEM, X-ray diffraction (XRD) and Raman spectra. The UV-vis diffuse reflectance spectra show that the optical absorption edge for Cu(2)O/TiO(2)/CA appears at 636 nm. Under visible-light (λ > 420 nm) irradiation, the photocurrent density increment on Cu(2)O/TiO(2)/CA is 60 times of that on Cu(2)O/TiO(2)/FTO. The electrochemical characteristic is investigated with electrochemical impedance spectrum (EIS). The Cu(2)O/TiO(2)/CA electrode is further applied in the electrosorptive photodegradation of the 2,4,6-trichlorophenol (2,4,6-TCP) wastewater. The result shows that the removal ratio of 2,4,6-TCP in 5.5 h on Cu(2)O/TiO(2)/CA is 96.3% and the TOC removal is 91.3%. The intermediates generated in the degradation process are analyzed by GC-MS and HPLC. The possible mechanism of visible light photocatalytic degradation of 2,4,6-TCP on Cu(2)O/TiO(2)/CA is also studied. PMID:22780307

  4. Synthesis of nitrogen-doped activated graphene aerogel/gold nanoparticles and its application for electrochemical detection of hydroquinone and o-dihydroxybenzene.

    PubMed

    Juanjuan, Zhang; Ruiyi, Li; Zaijun, Li; Junkang, Liu; Zhiguo, Gu; Guangli, Wang

    2014-05-21

    Graphene aerogel materials have attracted increasing attention owing to their large specific surface area, high conductivity and electronic interactions. Here, we report for the first time a novel strategy for the synthesis of nitrogen-doped activated graphene aerogel/gold nanoparticles (N-doped AGA/GNs). First, the mixture of graphite oxide, 2,4,6-trihydroxybenzaldehyde, urea and potassium hydroxide was dispersed in water and subsequently heated to form a graphene oxide hydrogel. Then, the hydrogel was dried by freeze-drying and reduced by thermal annealing in an Ar/H2 environment in sequence. Finally, GNs were adsorbed on the surface of the N-doped AGA. The resulting N-doped AGA/GNs offers excellent electronic conductivity (2.8 × 10(3) S m(-1)), specific surface area (1258 m(2) g(-1)), well-defined 3D hierarchical porous structure and apparent heterogeneous electron transfer rate constant (40.78 ± 0.15 cm s(-1)), which are notably better than that of previous graphene aerogel materials. Moreover, the N-doped AGA/GNs was used as a new sensing material for the electrochemical detection of hydroquinone (HQ) and o-dihydroxybenzene (DHB). Owing to the greatly enhanced electron transfer and mass transport, the sensor displays ultrasensitive electrochemical response to HQ and DHB. Its differential pulse voltammetric peak current linearly increases with the increase of HQ and DHB in the range of 5.0 × 10(-8) to 1.8 × 10(-4) M for HQ and 1 × 10(-8) to 2.0 × 10(-4) M for DHB. The detection limit is 1.5 × 10(-8) M for HQ and 3.3 × 10(-9) M for DHB (S/N = 3). This method provides the advantage of sensitivity, repeatability and stability compared with other HQ and DHB sensors. The sensor has been successfully applied to detection of HQ and DHB in real water samples with the spiked recovery in the range of 96.8-103.2%. The study also provides a promising approach for the fabrication of various graphene aerogel materials with improved electrochemical performances, which

  5. Ultralight boron nitride aerogels via template-assisted chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Song, Yangxi; Li, Bin; Yang, Siwei; Ding, Guqiao; Zhang, Changrui; Xie, Xiaoming

    2015-05-01

    Boron nitride (BN) aerogels are porous materials with a continuous three-dimensional network structure. They are attracting increasing attention for a wide range of applications. Here, we report the template-assisted synthesis of BN aerogels by catalyst-free, low-pressure chemical vapor deposition on graphene-carbon nanotube composite aerogels using borazine as the B and N sources with a relatively low temperature of 900 °C. The three-dimensional structure of the BN aerogels was achieved through the structural design of carbon aerogel templates. The BN aerogels have an ultrahigh specific surface area, ultralow density, excellent oil absorbing ability, and high temperature oxidation resistance. The specific surface area of BN aerogels can reach up to 1051 m2 g-1, 2-3 times larger than the reported BN aerogels. The mass density can be as low as 0.6 mg cm-3, much lower than that of air. The BN aerogels exhibit high hydrophobic properties and can absorb up to 160 times their weight in oil. This is much higher than porous BN nanosheets reported previously. The BN aerogels can be restored for reuse after oil absorption simply by burning them in air. This is because of their high temperature oxidation resistance and suggests broad utility as water treatment tools.

  6. Method of casting aerogels

    DOEpatents

    Poco, John F.

    1993-01-01

    The invention describes a method for making monolithic castings of transparent silica aerogel with densities in the range from 0.001 g/cm.sup.3 to 0.6 g/cm.sup.3. Various shapes of aerogels are cast in flexible polymer molds which facilitate removal and eliminate irregular surfaces. Mold dimensions are preselected to account for shrinkage of alcogel which occurs during the drying step of supercritical extraction of solvent.

  7. Process for forming transparent aerogel insulating arrays

    DOEpatents

    Tewari, Param H.; Hunt, Arlon J.

    1986-01-01

    An improved supercritical drying process for forming transparent silica aerogel arrays is described. The process is of the type utilizing the steps of hydrolyzing and condensing aloxides to form alcogels. A subsequent step removes the alcohol to form aerogels. The improvement includes the additional step, after alcogels are formed, of substituting a solvent, such as CO.sub.2, for the alcohol in the alcogels, the solvent having a critical temperature less than the critical temperature of the alcohol. The resulting gels are dried at a supercritical temperature for the selected solvent, such as CO.sub.2, to thereby provide a transparent aerogel array within a substantially reduced (days-to-hours) time period. The supercritical drying occurs at about 40.degree. C. instead of at about 270.degree. C. The improved process provides increased yields of large scale, structurally sound arrays. The transparent aerogel array, formed in sheets or slabs, as made in accordance with the improved process, can replace the air gap within a double glazed window, for example, to provide a substantial reduction in heat transfer. The thus formed transparent aerogel arrays may also be utilized, for example, in windows of refrigerators and ovens, or in the walls and doors thereof or as the active material in detectors for analyzing high energy elementry particles or cosmic rays.

  8. Process for forming transparent aerogel insulating arrays

    DOEpatents

    Tewari, P.H.; Hunt, A.J.

    1985-09-04

    An improved supercritical drying process for forming transparent silica aerogel arrays is described. The process is of the type utilizing the steps of hydrolyzing and condensing aloxides to form alcogels. A subsequent step removes the alcohol to form aerogels. The improvement includes the additional step, after alcogels are formed, of substituting a solvent, such as CO/sub 2/, for the alcohol in the alcogels, the solvent having a critical temperature less than the critical temperature of the alcohol. The resulting gels are dried at a supercritical temperature for the selected solvent, such as CO/sub 2/, to thereby provide a transparent aerogel array within a substantially reduced (days-to-hours) time period. The supercritical drying occurs at about 40/sup 0/C instead of at about 270/sup 0/C. The improved process provides increased yields of large scale, structurally sound arrays. The transparent aerogel array, formed in sheets or slabs, as made in accordance with the improved process, can replace the air gap within a double glazed window, for example, to provide a substantial reduction in heat transfer. The thus formed transparent aerogel arrays may also be utilized, for example, in windows of refrigerators and ovens, or in the walls and doors thereof or as the active material in detectors for analyzing high energy elementary particles or cosmic rays.

  9. Synthesis and characterization of highly crystalline graphene aerogels.

    PubMed

    Worsley, Marcus A; Pham, Thang T; Yan, Aiming; Shin, Swanee J; Lee, Jonathan R I; Bagge-Hansen, Michael; Mickelson, William; Zettl, Alex

    2014-10-28

    Aerogels are used in a broad range of scientific and industrial applications due to their large surface areas, ultrafine pore sizes, and extremely low densities. Recently, a large number of reports have described graphene aerogels based on the reduction of graphene oxide (GO). Though these GO-based aerogels represent a considerable advance relative to traditional carbon aerogels, they remain significantly inferior to individual graphene sheets due to their poor crystallinity. Here, we report a straightforward method to synthesize highly crystalline GO-based graphene aerogels via high-temperature processing common in commercial graphite production. The crystallization of the graphene aerogels versus annealing temperature is characterized using Raman and X-ray absorption spectroscopy, X-ray diffraction, and electron microscopy. Nitrogen porosimetry shows that the highly crystalline graphene macrostructure maintains a high surface area and ultrafine pore size. Because of their enhanced crystallinity, these graphene aerogels exhibit a ∼ 200 °C improvement in oxidation temperature and an order of magnitude increase in electrical conductivity. PMID:25283720

  10. Compression molding of aerogel microspheres

    DOEpatents

    Pekala, Richard W.; Hrubesh, Lawrence W.

    1998-03-24

    An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50-800 kg/m.sup.3 (0.05-0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization.

  11. Compression molding of aerogel microspheres

    DOEpatents

    Pekala, R.W.; Hrubesh, L.W.

    1998-03-24

    An aerogel composite material produced by compression molding of aerogel microspheres (powders) mixed together with a small percentage of polymer binder to form monolithic shapes in a cost-effective manner is disclosed. The aerogel composites are formed by mixing aerogel microspheres with a polymer binder, placing the mixture in a mold and heating under pressure, which results in a composite with a density of 50--800 kg/m{sup 3} (0.05--0.80 g/cc). The thermal conductivity of the thus formed aerogel composite is below that of air, but higher than the thermal conductivity of monolithic aerogels. The resulting aerogel composites are attractive for applications such as thermal insulation since fabrication thereof does not require large and expensive processing equipment. In addition to thermal insulation, the aerogel composites may be utilized for filtration, ICF target, double layer capacitors, and capacitive deionization. 4 figs.

  12. Monolithic aerogels with nanoporous crystalline phases

    NASA Astrophysics Data System (ADS)

    Daniel, Christophe; Guerra, Gaetano

    2015-05-01

    High porosity monolithic aerogels with nanoporous crystalline phases can be obtained from syndiotactic polystyrene and poly(2,6-dimethyl-1,4-phenylene)oxide thermoreversible gels by removing the solvent with supercritical CO2. The presence of crystalline nanopores in the aerogels based on these polymers allows a high uptake associated with a high selectivity of volatile organic compounds from vapor phase or aqueous solutions even at very low activities. The sorption and the fast kinetics make these materials particularly suitable as sorption medium to remove traces of pollutants from water and moist air.

  13. Continuous Bulk FeCuC Aerogel with Ultradispersed Metal Nanoparticles: An Efficient 3D Heterogeneous Electro-Fenton Cathode over a Wide Range of pH 3-9.

    PubMed

    Zhao, Hongying; Qian, Lin; Guan, Xiaohong; Wu, Deli; Zhao, Guohua

    2016-05-17

    Novel iron-copper-carbon (FeCuC) aerogel was fabricated through a one-step process from metal-resin precursors and then activated with CO2 and N2 in environmentally friendly way. The activated FeCuC aerogel was applied in a heterogeneous electro-Fenton (EF) process and exhibited higher mineralization efficiency than homogeneous EF technology. High total organic carbon (TOC) removal of organic pollutants with activated FeCuC aerogel was achieved at a wide range of pH values (3-9). The chemical oxygen demand (COD) of real dyeing wastewater was below China's discharge standard after 30 min of treatment, and the specific energy consumption was low (9.2 kW·h·kg(-1)COD(-1)), corresponding to a power consumption of only ∼0.34 kW·h per ton of wastewater. The enhanced mineralization efficiency of FeCuC aerogel was mostly attributable to ultradispersed metallic Fe-Cu nanoparticles embedded in 3D carbon matrix and the CO2-N2 treatment. The CO2 activation enhanced the accessibility of the aerogel's pores, and the secondary N2 activation enlarged the porosity and regenerated the ultradispersed zerovalent iron (Fe(0)) with reductive carbon. Cu(0) acted as a reduction promoter for interfacial electron transfer. Moreover, activated FeCuC aerogel presented low iron leaching (<0.1 ppm) in acidic solution and can be molded into different sizes with high flexibility. Thus, this material could be used as a low-cost cathode and efficient heterogeneous EF technology for actual wastewater treatment. PMID:27082750

  14. Continuous Bulk FeCuC Aerogel with Ultradispersed Metal Nanoparticles: An Efficient 3D Heterogeneous Electro-Fenton Cathode over a Wide Range of pH 3-9.

    PubMed

    Zhao, Hongying; Qian, Lin; Guan, Xiaohong; Wu, Deli; Zhao, Guohua

    2016-05-17

    Novel iron-copper-carbon (FeCuC) aerogel was fabricated through a one-step process from metal-resin precursors and then activated with CO2 and N2 in environmentally friendly way. The activated FeCuC aerogel was applied in a heterogeneous electro-Fenton (EF) process and exhibited higher mineralization efficiency than homogeneous EF technology. High total organic carbon (TOC) removal of organic pollutants with activated FeCuC aerogel was achieved at a wide range of pH values (3-9). The chemical oxygen demand (COD) of real dyeing wastewater was below China's discharge standard after 30 min of treatment, and the specific energy consumption was low (9.2 kW·h·kg(-1)COD(-1)), corresponding to a power consumption of only ∼0.34 kW·h per ton of wastewater. The enhanced mineralization efficiency of FeCuC aerogel was mostly attributable to ultradispersed metallic Fe-Cu nanoparticles embedded in 3D carbon matrix and the CO2-N2 treatment. The CO2 activation enhanced the accessibility of the aerogel's pores, and the secondary N2 activation enlarged the porosity and regenerated the ultradispersed zerovalent iron (Fe(0)) with reductive carbon. Cu(0) acted as a reduction promoter for interfacial electron transfer. Moreover, activated FeCuC aerogel presented low iron leaching (<0.1 ppm) in acidic solution and can be molded into different sizes with high flexibility. Thus, this material could be used as a low-cost cathode and efficient heterogeneous EF technology for actual wastewater treatment.

  15. Cellulose aerogels from aqueous alkali hydroxide-urea solution.

    PubMed

    Cai, Jie; Kimura, Satoshi; Wada, Masahisa; Kuga, Shigenori; Zhang, Lina

    2008-01-01

    Highly porous and strong cellulose aerogels were prepared by gelation of cellulose from aqueous alkali hydroxide/urea solution, followed by drying with supercritical CO2. Their morphology, pore structure, and physical properties were characterized by scanning and transmission electron microscopy, X-ray diffraction, nitrogen adsorption measurements, UV/Vis spectrometry, and tensile tests. The cellulose hydrogel was composed of interconnected about 20 nm wide. By using supercritical CO2 drying, the network structure in the hydrogel was well preserved in the aerogel. The results are preliminary but demonstrate the ability of this method to give cellulose aerogels of large surface areas (400-500 m2 g(-1)) which may be useful as adsorbents, heat/sound insulators, filters, catalyst supports, or carbon aerogel precursors. PMID:18605678

  16. Aerogel Microparticles from Oil-in-Oil Emulsion Systems.

    PubMed

    Gu, Senlong; Zhai, Chunhao; Jana, Sadhan C

    2016-06-01

    This paper reports preparation of polymer aerogel microparticles via sol-gel reactions inside micrometer size droplets created in an oil-in-oil emulsion system. The oil-in-oil emulsion system is obtained by dispersing in cyclohexane the droplets of the sols of polybenzoxazine (PBZ) or polyimide (PI) prepared in dimethylformamide. The sol droplets transform into harder gel microparticles due to sol-gel reactions. Finally, the aerogel microparticles are recovered using supercritical drying of the gel microparticles. The PBZ and PI aerogel microparticles prepared in this manner show mean diameter 32.7 and 40.0 μm, respectively, mesoporous internal structures, and surface area 55.4 and 512.0 m(2)/g, respectively. Carbonization of PBZ aerogel microparticles maintains the mesoporous internal structures but yields narrower pore size distribution. PMID:27183146

  17. Aerogel Microparticles from Oil-in-Oil Emulsion Systems.

    PubMed

    Gu, Senlong; Zhai, Chunhao; Jana, Sadhan C

    2016-06-01

    This paper reports preparation of polymer aerogel microparticles via sol-gel reactions inside micrometer size droplets created in an oil-in-oil emulsion system. The oil-in-oil emulsion system is obtained by dispersing in cyclohexane the droplets of the sols of polybenzoxazine (PBZ) or polyimide (PI) prepared in dimethylformamide. The sol droplets transform into harder gel microparticles due to sol-gel reactions. Finally, the aerogel microparticles are recovered using supercritical drying of the gel microparticles. The PBZ and PI aerogel microparticles prepared in this manner show mean diameter 32.7 and 40.0 μm, respectively, mesoporous internal structures, and surface area 55.4 and 512.0 m(2)/g, respectively. Carbonization of PBZ aerogel microparticles maintains the mesoporous internal structures but yields narrower pore size distribution.

  18. Separating proteins with activated carbon.

    PubMed

    Stone, Matthew T; Kozlov, Mikhail

    2014-07-15

    Activated carbon is applied to separate proteins based on differences in their size and effective charge. Three guidelines are suggested for the efficient separation of proteins with activated carbon. (1) Activated carbon can be used to efficiently remove smaller proteinaceous impurities from larger proteins. (2) Smaller proteinaceous impurities are most efficiently removed at a solution pH close to the impurity's isoelectric point, where they have a minimal effective charge. (3) The most efficient recovery of a small protein from activated carbon occurs at a solution pH further away from the protein's isoelectric point, where it is strongly charged. Studies measuring the binding capacities of individual polymers and proteins were used to develop these three guidelines, and they were then applied to the separation of several different protein mixtures. The ability of activated carbon to separate proteins was demonstrated to be broadly applicable with three different types of activated carbon by both static treatment and by flowing through a packed column of activated carbon. PMID:24898563

  19. Aerogels Insulate Against Extreme Temperatures

    NASA Technical Reports Server (NTRS)

    2010-01-01

    In 1992, NASA started to pursue the development of aerogel for cryogenic insulation. Kennedy Space Center awarded Small Business Innovation Research (SBIR) contracts to Aspen Systems Inc., of Marlborough, Massachusetts, that resulted in a new manufacturing process and a new flexible, durable, easy-to-use form of aerogel. Aspen Systems formed Aspen Aerogels Inc., in Northborough, Massachusetts, to market the product, and by 2009, the company had become the leading provider of aerogel in the United States, producing nearly 20 million square feet per year. With an array of commercial applications, the NASA-derived aerogel has most recently been applied to protect and insulate people s hands and feet.

  20. A tour-de-force in polymer crosslinked aerogels

    NASA Astrophysics Data System (ADS)

    Mulik, Sudhir M.

    In the quest of building mechanically strong materials with low density and high porosity, polymer crosslinked aerogels stand as the most promising nano-engineered examples. Covalent attachment of polymers and bridging of skeletal nanoparticles of typical aerogels is demonstrated by using surface initiated polymerization (SIP) with a bidentate free-radical initiator structurally related to azobisisobutyronitrile (AIBN) and confined on mesoporous silica surfaces. Different monomers were introduced in the mesopores and upon heating at 70 °C, all mesoporous surfaces throughout the entire skeletal framework were coated conformally with a 10-12 nm thick polymer layer indistinguishable spectroscopically from the respective commercial bulk materials. The new materials combine hydrophobicity with vastly improved mechanical properties. Resorcinol formaldehyde (RF) aerogels are pursued as precursors of carbon aerogels, which are electrically conducting. We have developed a HCl-catalyzed gelation process in CH3CN, which is completed in ˜ 2 h at room temperature as opposed to the week-long base-catalyzed literature process. The final aerogels are spectroscopically indistinguishable from typical base-catalyzed samples. Carbon (C-) aerogels are made by pyrolysis of RF aerogels, and combine electrical conductivity with a high open mesoporosity. Nevertheless, macropores facilitate mass-transfer and they could be beneficial for applications in separations or as fuel cell and battery electrodes. Here, we report a method where an open macroporosity is introduced by pyrolysing RF aerogels whose skeletal nanoparticles have been coated conformally and crosslinked chemically with an isocyanate-derived polymer. The new macroporous material was evaluated electrochemically for possible application as an electrode in batteries and fuel cells.

  1. Bonding aerogels with polyurethanes

    SciTech Connect

    Matthews, F.M.; Hoffman, D.M.

    1989-11-01

    Aerogels, porous silica glasses with ultra-fine cell size (30nm), are made by a solution gelation (sol-gel) process. The resulting gel is critical point dried to densities from 0.15--0.60 g/cc. This material is machinable, homogeneous, transparent, coatable and bondable. To bond aerogel an adhesive should have long cure time, no attack on the aerogel structure, and high strength. Several epoxies and urethanes were examined to determine if they satisfied these conditions. Bond strengths above 13 psi were found with double bubble and DP-110 epoxies and XI-208/ODA-1000 and Castall U-2630 urethanes. Hardman Kalex Tough Stuff'' A-85 hardness urethane gave 18 psi bond strength. Hardman A-85, Tuff-Stuff'' was selected for further evaluation because it produced bond strengths comparable to the adherend cohesive strength. 5 refs., 2 figs.

  2. Coated Aerogel Beads

    NASA Technical Reports Server (NTRS)

    Littman, Howard (Inventor); Plawsky, Joel L. (Inventor); Paccione, John D. (Inventor)

    2014-01-01

    Methods and apparatus for coating particulate material are provided. The apparatus includes a vessel having a top and a bottom, a vertically extending conduit having an inlet in the vessel and an outlet outside of the vessel, a first fluid inlet in the bottom of the vessel for introducing a transfer fluid, a second fluid inlet in the bottom of the vessel for introducing a coating fluid, and a fluid outlet from the vessel. The method includes steps of agitating a material, contacting the material with a coating material, and drying the coating material to produce a coated material. The invention may be adapted to coat aerogel beads, among other materials. A coated aerogel bead and an aerogel-based insulation material are also disclosed.

  3. Characterization of Aerogel's Optical Properties

    NASA Astrophysics Data System (ADS)

    Justen, Abigail; Young, Jonathan

    2013-10-01

    Aerogel is used in the kaon aerogel Cerenkov detector at Jefferson Lab. Kaons are identified by the number of photons created through Cerenkov radiation emitted as the kaon travels through the aerogel. Depending on the refractive index of the aerogel, kaons of different momenta can be detected and distinguished from protons. Therefore, a uniform refractive index in the detector is important to reduce uncertainty in the Cerenkov radiation. We found the refractive index of the aerogel by shining a red construction laser through it and measuring how far the beam refracted. The refractive index of aerogel is also directly related to the density of aerogel. The humidity in the air, if absorbed, could also affect the refractive index. To test the effect of humidity on aerogel we used a humidity controlled environment between 80 and 100 percent on aerogel from Matsushita Electric Works, Ltd, Japan Fine Ceramic Center, and Novosibirsk. Finally, we tested the transmittance of aerogel tiles with a UV/Vis photospectrometer to find the correlation between transmittance and the tile's properties. Tiles with the highest transmittance will allow for the most accurate count of the photons produced through Cerenkov radiation. The results from these experiments will be presented. Supported in Part by NSF Grant 1019521 and 1039446.

  4. Biological activation of carbon filters.

    PubMed

    Seredyńska-Sobecka, Bozena; Tomaszewska, Maria; Janus, Magdalena; Morawski, Antoni W

    2006-01-01

    To prepare biological activated carbon (BAC), raw surface water was circulated through granular activated carbon (GAC) beds. Biological activity of carbon filters was initiated after about 6 months of filter operation and was confirmed by two methods: measurement of the amount of biomass attached to the carbon and by the fluorescein diacetate (FDA) test. The effect of carbon pre-washing on WG-12 carbon properties was also studied. For this purpose, the nitrogen adsorption isotherms at 77K and Fourier transform-infrared (FT-IR) spectra analyses were performed. Moreover, iodine number, decolorizing power and adsorption properties of carbon in relation to phenol were studied. Analysis of the results revealed that after WG-12 carbon pre-washing its BET surface increased a little, the pH value of the carbon water extract decreased from 11.0 to 9.4, decolorizing power remained at the same level, and the iodine number and phenol adsorption rate increased. In preliminary studies of the ozonation-biofiltration process, a model phenol solution with concentration of approximately 10mg/l was applied. During the ozonation process a dose of 1.64 mg O(3)/mg TOC (total organic carbon) was employed and the contact time was 5 min. Four empty bed contact times (EBCTs) in the range of 2.4-24.0 min were used in the biofiltration experiment. The effectiveness of purification was measured by the following parameters: chemical oxygen demand (COD(Mn)), TOC, phenol concentration and UV(254)-absorbance. The parameters were found to decrease with EBCT. PMID:16376966

  5. Clay Nanocomposite/Aerogel Sandwich Structures for Cryotanks

    NASA Technical Reports Server (NTRS)

    Miller, Sandi; Leventis, Nicholas; Johnston, J. Chris; Meador, Michael

    2006-01-01

    GRC research has led to the development of epoxy-clay nanocomposites with 60-70% lower gas permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. More recent work has produced new composites with more than a 100-fold reduction in helium permeability. Use of these advanced, high barrier composites would eliminate the need for a liner in composite cryotanks, thereby simplifying construction and reducing propellant leakage. Aerogels are attractive materials for use as cryotank insulation because of their low density and low thermal conductivity. However, aerogels are fragile and have poor environmental stability, which have limited their use to certain applications in specialized environments (e.g., in certain types of nuclear reactors as Cerenkov radiation detectors, and as thermal insulators aboard space rovers on Mars). New GRC developed polymer crosslinked aerogels (X-Aerogels) retain the low density of conventional aerogels, but they demonstrate a 300-fold increase in their mechanical strength. Currently, our strongest materials combine a density of approx. 0.45 g/cc, a thermal conductivity of approx. 0.04 W/mK and a compressive strength of 185 MPa. Use of these novel aerogels as insulation materials/structural components in combination with the low permeability of epoxy-clay nanocomposites could significantly reduce cryotank weight and improve durability.

  6. Silylation of low-density silica and bridged polysilsesquioxane aerogels

    SciTech Connect

    DeFriend, K. A.; Loy, D. A.; Salazar, K. V.; Wilson, K. V.

    2004-01-01

    Silica and bridged polysilsesquioxane aerogels are low-density materials that are attractive for applications such as thermal insulation, porous separation media or catalyst supports, adsorbents, and cometary dust capture agents. However, aerogels are notoriously weak and brittle making it difficult to handle and machine monoliths into desired forms. This complication prevents the development of many applications that would otherwise benefit from the use of the low-density materials. Here, we will describe our efforts to chemically modify and mechanically enhance silica-based aerogels using chemical vapor techniques without sacrificing their characteristic low densities. Monolithic silica and organic-bridged polysilsesquioxane aerogels were prepared by sol-gel polymerization of the respective methoxysilane monomers followed by supercritical carbon dioxide drying of the gels. Then the gels were reactively modified with silylating agents to demonstrate the viability of CVD modification of aerogels, and to determine the effects of silylation of surface silanols on the morphology, surface area, and mechanical properties of the resulting aerogels.

  7. Aerogel Fingerprint Media

    SciTech Connect

    Miller, Fred S.; Andresen, Brian D.

    1999-09-21

    A fingerprint medium which is made of an aerogel having a predetermined density. The fingerprint medium may have a midrange density for forming plates or may be crushed forming a powder. The fingerprint medium may further include at least one of a metal and metal oxide to enhance characteristics desirable in a fingerprint medium.

  8. Mechanically Strong, Polymer Cross-linked Aerogels (X-Aerogels)

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2006-01-01

    Aerogels comprise a class of low-density, high porous solid objects consisting of dimensionally quasi-stable self-supported three-dimensional assemblies of nanoparticles. Aerogels are pursued because of properties above and beyond those of the individual nanoparticles, including low thermal conductivity, low dielectric constant and high acoustic impedance. Possible applications include thermal and vibration insulation, dielectrics for fast electronics, and hosting of functional guests for a wide variety of optical, chemical and electronic applications. Aerogels, however, are extremely fragile materials, hence they have found only limited application in some very specialized environments, for example as Cerenkov radiation detectors in certain types of nuclear reactors, aboard spacecraft as collectors of hypervelocity particles (refer to NASA's Stardust program) and as thermal insulators on planetary vehicles on Mars (refer to Sojourner Rover in 1997 and Spirit and Opportunity in 2004). Along these lines, the X-Aerogel is a new NASA-developed strong lightweight material that has resolved the fragility problem of traditional (native) aerogels. X-Aerogels are made by applying a conformal polymer coating on the surfaces of the skeletal nanoparticles of native aerogels (see Scanning Electron Micrographs). Since the relative amounts of the polymeric crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by the templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by remplated casting of polymer on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralighweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the the thermal conductivity of styrofoam. X-Aerogels

  9. Activated carbon to the rescue

    SciTech Connect

    Sen, S.

    1996-03-01

    This article describes the response to pipeline spill of ethylene dichloride (EDC) on the property of an oil company. Activated carbon cleanup proceedure was used. During delivery, changeout, transport, storage, thermal reactivation, and return delivery to the site, the carbon never came into direct contact with operating personnel or the atmosphere. More than 10,000 tones of dredge soil and 50 million gallons of surface water were processed during the emergency response.

  10. High surface area aerogels for energy storage and efficiency

    NASA Astrophysics Data System (ADS)

    Maloney, Ryan Patrick

    ADAI are demonstrated in a third-generation prototypical thermoelectric generator for automotive waste heat recovery. The second chapter then details two different aerogel-based materials for electrochemical energy storage. It begins with lithium titanate aerogel, which takes advantage of the high surface area of the aerogel morphology to display a batt-cap behavior. This should allow the lithium titanate aerogel to perform at higher rates than would normally be expected for the bulk oxide material. Additionally, the flexibility of the sol-gel process is demonstrated through the incorporation of electrically conductive high-surface area exfoliated graphite nanoplatelets in the oxide. The last section describes the characterization of a LiMn2O 4 spinel coated carbon nanofoam in a non-aqueous electrolyte. The short diffusion path, high surface area and intimately wired architecture of the nanofoam allows the oxide to retain its capacity at significantly higher rates when compared with literature values for the bulk oxide. Additionally, the nanometric length scale improves cycle life, and the high surface area dramatically increases the insertion capacity by providing a higher concentration of surface defects. Taken together, it is clear that aerogels are an extremely attractive class of material for applications pertaining to energy and efficiency, and further research in this area will provide valuable solutions for pressing societal needs. (Abstract shortened by UMI.).

  11. Silicon Oxycarbide Aerogels for High-Temperature Thermal Insulation

    NASA Technical Reports Server (NTRS)

    Evans, Owen; Rhine, Wendell; Coutinho, Decio

    2010-01-01

    This work has shown that the use of SOC-A35 leads to aerogel materials containing a significant concentration of carbidic species and limited amorphous free carbon. Substitution of the divalent oxide species in silica with tetravalent carbidic carbon has directly led to materials that exhibit increased network viscosity, reduced sintering, and limited densification. The SiOC aerogels produced in this work have the highest carbide content of any dense or porous SiOC glass reported in the literature at that time, and exhibit tremendous long-term thermal stability.

  12. A comparison of mechanical properties and scaling law relationships for silica aerogels and their organic counterparts

    SciTech Connect

    Pekala, R.W.; Hrubesh, L.W.; Tillotson, T.M.; Alviso, C.T.; Poco, J.F.; LeMay, J.D.

    1990-08-01

    Aerogels are a special class of open-cell foams derived from the supercritical extraction of highly crosslinked, inorganic or organic gels. The resultant materials have ultrafine cell/pore sizes (< 100 nm), high surface areas (350--1000m{sup 2}/g), and a microstructure composed of interconnected colloidal-like particles or polymeric chains with characteristic diameters of 10 nm. TEM and SAXS show that this microstructure is sensitive to variations in processing conditions that influence crosslinking chemistry and growth processes prior to gelation. Traditional silica aerogels are prepared via the hydrolysis and condensation of tetramethoxy silane (TMOS) or tetraethoxy silane (TEOS). Factors such as pH and the (H{sub 2}O)/(TMOS) ratio affect the microstructure of the dried aerogel. It is generally accepted that polymeric' silica aerogels result from acid catalysis while colloidal'silica aerogels result from base catalysis. Recently, Hrubesh and Tillotson developed a new condensed silica' procedure for obtaining silica aerogels with densities as low as 0.004g/cc, i.e. only 3{times} the density of air. Organic aerogels are formed from the aqueous, polycondensation of (1) resorcinol/formaldehyde or (2) melamine/formaldehyde. The microstructure of the resorcinol-formaldehyde (RF) aerogels is dictated by the amount of base catalyst used in the sol-gel polymerization. In addition, these materials can be pyrolyzed in an inert atmosphere to form vitreous carbon aerogels. Melamine- formaldehyde (MF) aerogels that are both colorless and transparent are only formed under acidic conditions (i.e. pH = 1--2). In this paper, the microstructural dependence and scaling law relationships for the compressive modulus of silica, carbon, RF, and MF aerogels will be discussed in detail. 17 refs., 1 fig.

  13. Mechanically Strong, Lightweight Porous Materials Developed (X-Aerogels)

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2005-01-01

    Aerogels are attractive materials for a variety of NASA missions because they are ultralightweight, have low thermal conductivity and low-dielectric constants, and can be readily doped with other materials. Potential NASA applications for these materials include lightweight insulation for spacecraft, habitats, and extravehicular activity (EVA) suits; catalyst supports for fuel cell and in situ resource utilization; and sensors for air- and water-quality monitoring for vehicles, habitats, and EVA suits. Conventional aerogels are extremely fragile and require processing via supercritical fluid extraction, which adds cost to the production of an aerogel and limits the sizes and geometries of samples that can be produced from these materials. These issues have severely hampered the application of aerogels in NASA missions.

  14. Metalloradical-catalyzed aliphatic carbon-carbon activation of cyclooctane.

    PubMed

    Chan, Yun Wai; Chan, Kin Shing

    2010-05-26

    The aliphatic carbon-carbon activation of c-octane was achieved via the addition of Rh(ttp)H to give Rh(ttp)(n-octyl) in good yield under mild reaction conditions. The aliphatic carbon-carbon activation was Rh(II)(ttp)-catalyzed and was very sensitive to porphyrin sterics.

  15. Organic aerogel microspheres and fabrication method therefor

    DOEpatents

    Mayer, S.T.; Kong, F.M.; Pekala, R.W.; Kaschmitter, J.L.

    1996-04-16

    Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

  16. Organic aerogel microspheres and fabrication method therefor

    DOEpatents

    Mayer, Steven T.; Kong, Fung-Ming; Pekala, Richard W.; Kaschmitter, James L.

    1996-01-01

    Organic aerogel microspheres which can be used in capacitors, batteries, thermal insulation, adsorption/filtration media, and chromatographic packings, having diameters ranging from about 1 micron to about 3 mm. The microspheres can be pyrolyzed to form carbon aerogel microspheres. This method involves stirring the aqueous organic phase in mineral oil at elevated temperature until the dispersed organic phase polymerizes and forms nonsticky gel spheres. The size of the microspheres depends on the collision rate of the liquid droplets and the reaction rate of the monomers from which the aqueous solution is formed. The collision rate is governed by the volume ratio of the aqueous solution to the mineral oil and the shear rate, while the reaction rate is governed by the chemical formulation and the curing temperature.

  17. Scandium functionalized carbon aerogel: Synthesis of nanoparticles and structure of a new ScOCl and properties of NaAlH4 as a function of pore size

    NASA Astrophysics Data System (ADS)

    Javadian, Payam; Nielsen, Thomas K.; Ravnsbæk, Dorthe B.; Jepsen, Lars H.; Polanski, Marek; Plocinski, Tomasz; Kunce, Izabela; Besenbacher, Flemming; Bystrzycki, Jerzy; Jensen, Torben R.

    2015-11-01

    A new method for scandium-functionalization of carbon aerogels forming nanoparticles of a new scandiumoxochloride, ScOCl is presented. Sodium aluminiumhydride, NaAlH4, is successfully melt infiltrated into the nano porous scaffolds with pore sizes of Dmax=7, 10, 13, 21, 26 and 39 nm, containing scandium based nano particles (<2.9 wt%) confirmed by elemental analysis and scanning electron microscopy. A systematic study of hydrogen storage properties of the nano composite materials is presented. An aqueous solution of ScCl3 was initially infiltrated and formed nanoconfined [Sc(OH)(H2O)5]2Cl4(H2O)2, which transforms to nanoparticles of a new scandium oxochloride, ScOCl at 192 °C and to Sc2O3 at 420 °C. ScOCl crystallizes in an orthorhombic unit cell a=3.4409(8), b=3.9613(6) and c=8.178(2) Å, space group Pmmn, and is built from layers of [ScO4Cl2] octahedra forming neutral ScOCl layers. Temperature programmed desorption mass spectroscopy shows slightly improved kinetics for release of hydrogen with decreasing pore size. Continuous cycling of hydrogen release and uptake measured by the Sieverts' method reveal a larger preserved hydrogen storage capacity for scandium-functionalized aerogel with the larger pores (39 nm).

  18. Infiltrated carbon foam composites

    NASA Technical Reports Server (NTRS)

    Lucas, Rick D. (Inventor); Danford, Harry E. (Inventor); Plucinski, Janusz W. (Inventor); Merriman, Douglas J. (Inventor); Blacker, Jesse M. (Inventor)

    2012-01-01

    An infiltrated carbon foam composite and method for making the composite is described. The infiltrated carbon foam composite may include a carbonized carbon aerogel in cells of a carbon foam body and a resin is infiltrated into the carbon foam body filling the cells of the carbon foam body and spaces around the carbonized carbon aerogel. The infiltrated carbon foam composites may be useful for mid-density ablative thermal protection systems.

  19. Amyloid Templated Gold Aerogels.

    PubMed

    Nyström, Gustav; Fernández-Ronco, María P; Bolisetty, Sreenath; Mazzotti, Marco; Mezzenga, Raffaele

    2016-01-20

    Amyloid fibril-based ultralow-density aerogels are designed by functionalization with gold nanoparticles and microcrystals, leading to hybrids of unprecedented lightness and functionality. By changing the colloidal gold shape, size, and concentration, the gold composition can be tuned to reach contents ≥20 kt equivalent, yet at densities ≈10(3) lighter than any equivalent gold alloys, and combining unique features such as porosity, catalytic properties, pressure sensing, and autofluorescence.

  20. Metal Nanoparticle Aerogel Composites

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Ignont, Erica; Snow, Lanee; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    We have fabricated sol-gels containing gold and silver nanoparticles. Formation of an aerogel produces a blue shift in the surface plasmon resonance as a result of the decrease in the dielectric constant of the matrix upon supercritical extraction of the solvent. However, as a result of chemical interface damping this blue shift does not obey effective medium theories. Annealing the samples in a reducing atmosphere at 400 C eliminates this discrepancy and results in narrowing and further blue shifting of the plasmon resonance. Metal particle aggregation also results in a deviation from the predictions of effective medium theories, but can be controlled through careful handling and by avoiding the use of alcohol. By applying effective medium theories to the heterogeneous interlayer surrounding each metal particle, we extend the technique of immersion spectroscopy to inhomogeneous materials characterized by spatially dependent dielectric constants, such as aerogels. We demonstrate that the shift in the surface plasmon wavelength provides the average fractional composition of each component (air and silica) in this inhomogeneous layer, i.e. the porosity of the aerogel or equivalently, for these materials, the catalytic dispersion. Additionally, the kinetics suggest that collective particle interactions in coagulated metal clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

  1. Aerogel/polymer composite materials

    NASA Technical Reports Server (NTRS)

    Williams, Martha K. (Inventor); Smith, Trent M. (Inventor); Fesmire, James E. (Inventor); Roberson, Luke B. (Inventor); Clayton, LaNetra M. (Inventor)

    2010-01-01

    The invention provides new composite materials containing aerogels blended with thermoplastic polymer materials at a weight ratio of aerogel to thermoplastic polymer of less than 20:100. The composite materials have improved thermal insulation ability. The composite materials also have better flexibility and less brittleness at low temperatures than the parent thermoplastic polymer materials.

  2. Production of hollow aerogel microspheres

    DOEpatents

    Upadhye, Ravindra S.; Henning, Sten A.

    1993-01-01

    A method is described for making hollow aerogel microspheres of 800-1200 .mu. diameter and 100-300 .mu. wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

  3. Production of hollow aerogel microspheres

    SciTech Connect

    Upadhye, R.S.; Henning, S.A.

    1990-12-31

    A method is described for making hollow aerogel microspheres of 800--1200{mu} diameter and 100--300{mu} wall thickness by forming hollow alcogel microspheres during the sol/gel process in a catalytic atmosphere and capturing them on a foam surface containing catalyst. Supercritical drying of the formed hollow alcogel microspheres yields hollow aerogel microspheres which are suitable for ICF targets.

  4. Protective Skins for Aerogel Monoliths

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas; Johnston, James C.; Kuczmarski, Maria A.; Meador, Ann B.

    2007-01-01

    A method of imparting relatively hard protective outer skins to aerogel monoliths has been developed. Even more than aerogel beads, aerogel monoliths are attractive as thermal-insulation materials, but the commercial utilization of aerogel monoliths in thermal-insulation panels has been inhibited by their fragility and the consequent difficulty of handling them. Therefore, there is a need to afford sufficient protection to aerogel monoliths to facilitate handling, without compromising the attractive bulk properties (low density, high porosity, low thermal conductivity, high surface area, and low permittivity) of aerogel materials. The present method was devised to satisfy this need. The essence of the present method is to coat an aerogel monolith with an outer polymeric skin, by painting or spraying. Apparently, the reason spraying and painting were not attempted until now is that it is well known in the aerogel industry that aerogels collapse in contact with liquids. In the present method, one prevents such collapse through the proper choice of coating liquid and process conditions: In particular, one uses a viscous polymer precursor liquid and (a) carefully controls the amount of liquid applied and/or (b) causes the liquid to become cured to the desired hard polymeric layer rapidly enough that there is not sufficient time for the liquid to percolate into the aerogel bulk. The method has been demonstrated by use of isocyanates, which, upon exposure to atmospheric moisture, become cured to polyurethane/polyurea-type coats. The method has also been demonstrated by use of commercial epoxy resins. The method could also be implemented by use of a variety of other resins, including polyimide precursors (for forming high-temperature-resistant protective skins) or perfluorinated monomers (for forming coats that impart hydrophobicity and some increase in strength).

  5. Photoconductivity of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    Kuriyama, K.; Dresselhaus, M. S.

    1990-08-01

    The photoconductivity is measured on a high-surface-area disordered carbon material, namely activated carbon fibers, to investigate their electronic properties. Measurements of decay time, recombination kinetics and temperature dependence of the photoconductivity generally reflect the electronic properties of a material. The material studied in this paper is a highly disordered carbon derived from a phenolic precursor, having a huge specific surface area of 1000--2000m{sup 2}/g. Our preliminary thermopower measurements suggest that this carbon material is a p-type semiconductor with an amorphous-like microstructure. The intrinsic electrical conductivity, on the order of 20S/cm at room temperature, increases with increasing temperature in the range 30--290K. In contrast with the intrinsic conductivity, the photoconductivity in vacuum decreases with increasing temperature. The recombination kinetics changes from a monomolecular process at room temperature to a biomolecular process at low temperatures. The observed decay time of the photoconductivity is {approx equal}0.3sec. The magnitude of the photoconductive signal was reduced by a factor of ten when the sample was exposed to air. The intrinsic carrier density and the activation energy for conduction are estimated to be {approx equal}10{sup 21}/cm{sup 3} and {approx equal}20meV, respectively. The majority of the induced photocarriers and of the intrinsic carriers are trapped, resulting in the long decay time of the photoconductivity and the positive temperature dependence of the conductivity.

  6. Nanoencapsulated aerogels produced by monomer vapor deposition and polymerization

    NASA Technical Reports Server (NTRS)

    Sullivan, Thomas A. (Inventor)

    2011-01-01

    Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating. In an embodiment, the polymer coated aerogel is comprised of a porosity and has a compressive modulus greater than the compressive modulus of the aerogel substrate.

  7. pH-controllable synthesis of unique nanostructured tungsten oxide aerogel and its sensitive glucose biosensor

    NASA Astrophysics Data System (ADS)

    Sun, Qiang-Qiang; Xu, Maowen; Bao, Shu-Juan; Li, Chang Ming

    2015-03-01

    This work presents a controllable synthesis of nanowire-networked tungsten oxide aerogels, which was performed by varying the pH in a polyethyleneimine (PEI)-assisted hydrothermal process. An enzyme-tungsten oxide aerogel co-modified electrode shows high activity and selectivity toward glucose oxidation, thus holding great promise for applications in bioelectronics.

  8. pH-controllable synthesis of unique nanostructured tungsten oxide aerogel and its sensitive glucose biosensor.

    PubMed

    Sun, Qiang-Qiang; Xu, Maowen; Bao, Shu-Juan; Li, Chang Ming

    2015-03-20

    This work presents a controllable synthesis of nanowire-networked tungsten oxide aerogels, which was performed by varying the pH in a polyethyleneimine (PEI)-assisted hydrothermal process. An enzyme-tungsten oxide aerogel co-modified electrode shows high activity and selectivity toward glucose oxidation, thus holding great promise for applications in bioelectronics.

  9. Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames

    SciTech Connect

    Chakrabarty, Rajan K.; Novosselov, Igor V.; Beres, Nicholas D.; Moosmüller, Hans; Sorensen, Christopher M.; Stipe, Christopher B.

    2014-06-16

    We report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (−g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in −g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in −g flames, which reduces the time to gel for nanoparticles by ≈10{sup 6} s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale.

  10. Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Rajan K.; Novosselov, Igor V.; Beres, Nicholas D.; Moosmüller, Hans; Sorensen, Christopher M.; Stipe, Christopher B.

    2014-06-01

    We report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (-g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in -g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in -g flames, which reduces the time to gel for nanoparticles by ≈106 s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale.

  11. Fabricating solid carbon porous electrodes from powders

    DOEpatents

    Kaschmitter, James L.; Tran, Tri D.; Feikert, John H.; Mayer, Steven T.

    1997-01-01

    Fabrication of conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive dionization, and waste treatment. Electrodes fabricated from low surface area (<50 m.sup.2 /gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon compositives with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to be high surface area carbons, fuel cell electrodes can be produced.

  12. Fabricating solid carbon porous electrodes from powders

    DOEpatents

    Kaschmitter, J.L.; Tran, T.D.; Feikert, J.H.; Mayer, S.T.

    1997-06-10

    Fabrication is described for conductive solid porous carbon electrodes for use in batteries, double layer capacitors, fuel cells, capacitive deionization, and waste treatment. Electrodes fabricated from low surface area (<50 m{sup 2}/gm) graphite and cokes exhibit excellent reversible lithium intercalation characteristics, making them ideal for use as anodes in high voltage lithium insertion (lithium-ion) batteries. Electrodes having a higher surface area, fabricated from powdered carbon blacks, such as carbon aerogel powder, carbon aerogel microspheres, activated carbons, etc. yield high conductivity carbon composites with excellent double layer capacity, and can be used in double layer capacitors, or for capacitive deionization and/or waste treatment of liquid streams. By adding metallic catalysts to high surface area carbons, fuel cell electrodes can be produced. 1 fig.

  13. Curcumin cross-linked collagen aerogels with controlled anti-proteolytic and pro-angiogenic efficacy.

    PubMed

    Dharunya, G; Duraipandy, N; Lakra, Rachita; Korapatti, Purna Sai; Jayavel, R; Kiran, Manikantan Syamala

    2016-01-01

    This paper elucidates the development of a curcumin cross-linked collagen aerogel system with controlled anti-proteolytic activity and pro-angiogenic efficacy. The results of this study showed that in situ cross-linking of curcumin with collagen leads to the development of aerogels with enhanced physical and mechanical properties. The integrity of collagen after cross-linking with curcumin was studied via FTIR spectroscopy. The results confirmed that the cross-linking with curcumin did not induce any structural changes in the collagen. The curcumin cross-linked collagen aerogels exhibited potent anti-proteolytic and anti-microbial activity. Scanning electron and atomic force microscopic analysis of curcumin cross-linked collagen aerogels showed a 3D microstructure that enhanced the adhesion and proliferation of cells. The highly organized geometry of collagen-curcumin aerogels enhanced the permeability and water-retaining ability required for the diffusion of nutrients that aid cellular growth. The pro-angiogenic properties of collagen-curcumin aerogels were ascribed to the cumulative effect of the nutraceutical and the collagen molecule, which augmented the restoration of damaged tissue. Further, these aerogels exhibited controlled anti-proteolytic activity, which makes them suitable 3D scaffolds for biomedical applications. This study provides scope for the development of biocompatible and bioresorbable collagen aerogel systems that use a nutraceutical as a cross-linker for biomedical applications. PMID:27509047

  14. Improved Aerogel Vacuum Thermal Insulation

    NASA Technical Reports Server (NTRS)

    Ruemmele, Warren P.; Bue, Grant C.

    2009-01-01

    An improved design concept for aerogel vacuum thermal-insulation panels calls for multiple layers of aerogel sandwiched between layers of aluminized Mylar (or equivalent) poly(ethylene terephthalate), as depicted in the figure. This concept is applicable to both the rigid (brick) form and the flexible (blanket) form of aerogel vacuum thermal-insulation panels. Heretofore, the fabrication of a typical aerogel vacuum insulating panel has involved encapsulation of a single layer of aerogel in poly(ethylene terephthalate) and pumping of gases out of the aerogel-filled volume. A multilayer panel according to the improved design concept is fabricated in basically the same way: Multiple alternating layers of aerogel and aluminized poly(ethylene terephthalate) are assembled, then encapsulated in an outer layer of poly(ethylene terephthalate), and then the volume containing the multilayer structure is evacuated as in the single-layer case. The multilayer concept makes it possible to reduce effective thermal conductivity of a panel below that of a comparable single-layer panel, without adding weight or incurring other performance penalties. Implementation of the multilayer concept is simple and relatively inexpensive, involving only a few additional fabrication steps to assemble the multiple layers prior to evacuation. For a panel of the blanket type, the multilayer concept, affords the additional advantage of reduced stiffness.

  15. Optothermal nonlinearity of silica aerogel

    NASA Astrophysics Data System (ADS)

    Braidotti, Maria Chiara; Gentilini, Silvia; Fleming, Adam; Samuels, Michiel C.; Di Falco, Andrea; Conti, Claudio

    2016-07-01

    We report on the characterization of silica aerogel thermal optical nonlinearity, obtained by z-scan technique. The results show that typical silica aerogels have nonlinear optical coefficient similar to that of glass (≃10-12 m2/W), with negligible optical nonlinear absorption. The nonlinear coefficient can be increased to values in the range of 10-10 m2/W by embedding an absorbing dye in the aerogel. This value is one order of magnitude higher than that observed in the pure dye and in typical highly nonlinear materials like liquid crystals.

  16. Noble metal aerogels-synthesis, characterization, and application as electrocatalysts.

    PubMed

    Liu, Wei; Herrmann, Anne-Kristin; Bigall, Nadja C; Rodriguez, Paramaconi; Wen, Dan; Oezaslan, Mehtap; Schmidt, Thomas J; Gaponik, Nikolai; Eychmüller, Alexander

    2015-02-17

    CONSPECTUS: Metallic and catalytically active materials with high surface area and large porosity are a long-desired goal in both industry and academia. In this Account, we summarize the strategies for making a variety of self-supported noble metal aerogels consisting of extended metal backbone nanonetworks. We discuss their outstanding physical and chemical properties, including their three-dimensional network structure, the simple control over their composition, their large specific surface area, and their hierarchical porosity. Additionally, we show some initial results on their excellent performance as electrocatalysts combining both high catalytic activity and high durability for fuel cell reactions such as ethanol oxidation and the oxygen reduction reaction (ORR). Finally, we give some hints on the future challenges in the research area of metal aerogels. We believe that metal aerogels are a new, promising class of electrocatalysts for polymer electrolyte fuel cells (PEFCs) and will also open great opportunities for other electrochemical energy systems, catalysis, and sensors. The commercialization of PEFCs encounters three critical obstacles, viz., high cost, insufficient activity, and inadequate long-term durability. Besides others, the sluggish kinetics of the ORR and alcohol oxidation and insufficient catalyst stability are important reasons for these obstacles. Various approaches have been taken to overcome these obstacles, e.g., by controlling the catalyst particle size in an optimized range, forming multimetallic catalysts, controlling the surface compositions, shaping the catalysts into nanocrystals, and designing supportless catalysts with extended surfaces such as nanostructured thin films, nanotubes, and porous nanostructures. These efforts have produced plenty of excellent electrocatalysts, but the development of multisynergetic functional catalysts exhibiting low cost, high activity, and high durability still faces great challenges. In this

  17. Alginate-based hybrid aerogel microparticles for mucosal drug delivery.

    PubMed

    Gonçalves, V S S; Gurikov, P; Poejo, J; Matias, A A; Heinrich, S; Duarte, C M M; Smirnova, I

    2016-10-01

    The application of biopolymer aerogels as drug delivery systems (DDS) has gained increased interest during the last decade since these structures have large surface area and accessible pores allowing for high drug loadings. Being biocompatible, biodegradable and presenting low toxicity, polysaccharide-based aerogels are an attractive carrier to be applied in pharmaceutical industry. Moreover, some polysaccharides (e.g. alginate and chitosan) present mucoadhesive properties, an important feature for mucosal drug delivery. This feature allows to extend the contact of DDS with biological membranes, thereby increasing the absorption of drugs through the mucosa. Alginate-based hybrid aerogels in the form of microparticles (<50μm) were investigated in this work as carriers for mucosal administration of drugs. Low methoxyl pectin and κ-carrageenan were co-gelled with alginate and further dried with supercritical CO2 (sc-CO2). Spherical mesoporous aerogel microparticles were obtained for alginate, hybrid alginate/pectin and alginate/κ-carrageenan aerogels, presenting high specific surface area (370-548m(2)g(-1)) and mucoadhesive properties. The microparticles were loaded with ketoprofen via adsorption from its solution in sc-CO2, and with quercetin via supercritical anti-solvent precipitation. Loading of ketoprofen was in the range between 17 and 22wt% whereas quercetin demonstrated loadings of 3.1-5.4wt%. Both the drugs were present in amorphous state. Loading procedure allowed the preservation of antioxidant activity of quercetin. Release of both drugs from alginate/κ-carrageenan aerogel was slightly faster compared to alginate/pectin. The results indicate that alginate-based aerogel microparticles can be viewed as promising matrices for mucosal drug delivery applications.

  18. Alginate-based hybrid aerogel microparticles for mucosal drug delivery.

    PubMed

    Gonçalves, V S S; Gurikov, P; Poejo, J; Matias, A A; Heinrich, S; Duarte, C M M; Smirnova, I

    2016-10-01

    The application of biopolymer aerogels as drug delivery systems (DDS) has gained increased interest during the last decade since these structures have large surface area and accessible pores allowing for high drug loadings. Being biocompatible, biodegradable and presenting low toxicity, polysaccharide-based aerogels are an attractive carrier to be applied in pharmaceutical industry. Moreover, some polysaccharides (e.g. alginate and chitosan) present mucoadhesive properties, an important feature for mucosal drug delivery. This feature allows to extend the contact of DDS with biological membranes, thereby increasing the absorption of drugs through the mucosa. Alginate-based hybrid aerogels in the form of microparticles (<50μm) were investigated in this work as carriers for mucosal administration of drugs. Low methoxyl pectin and κ-carrageenan were co-gelled with alginate and further dried with supercritical CO2 (sc-CO2). Spherical mesoporous aerogel microparticles were obtained for alginate, hybrid alginate/pectin and alginate/κ-carrageenan aerogels, presenting high specific surface area (370-548m(2)g(-1)) and mucoadhesive properties. The microparticles were loaded with ketoprofen via adsorption from its solution in sc-CO2, and with quercetin via supercritical anti-solvent precipitation. Loading of ketoprofen was in the range between 17 and 22wt% whereas quercetin demonstrated loadings of 3.1-5.4wt%. Both the drugs were present in amorphous state. Loading procedure allowed the preservation of antioxidant activity of quercetin. Release of both drugs from alginate/κ-carrageenan aerogel was slightly faster compared to alginate/pectin. The results indicate that alginate-based aerogel microparticles can be viewed as promising matrices for mucosal drug delivery applications. PMID:27393563

  19. Method of low pressure and/or evaporative drying of aerogel

    DOEpatents

    Mayer, S.T.; Kaschmitter, J.L.; Pekala, R.W.

    1995-05-30

    A process is described whereby Resorcinol/Formaldehyde (RF) aerogel having a density of about 0.4--1.2 g/cc can be manufactured using a simple air drying procedure. This process is inherently simpler, quicker, and less expensive than the more conventional supercritical or subcritical CO{sub 2} extraction procedures. RF aerogels can be used as produced, such as in insulation applications, or pyrolyzed to form carbon aerogels with a density of about 0.9 g/cc for use in applications such as batteries, supercapacitors, etc.

  20. Method of low pressure and/or evaporative drying of aerogel

    DOEpatents

    Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

    1995-01-01

    A process whereby Resorcinol/Formaldehyde (RF) aerogel having a density of about 0.4-1.2 g/cc can be manufactured using a simple air drying procedure. This process is inherently simpler, quicker, and less expensive than the more conventional supercritical or subcritical CO.sub.2 extraction procedures. RF aerogels can be used as produced, such as in insulation applications, or pyrolyzed to form carbon aerogels with a density of about 0.9 g/cc for use in applications such as batteries, supercapacitors, etc.

  1. Activated, coal-based carbon foam

    DOEpatents

    Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

    2004-12-21

    An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

  2. Activated, coal-based carbon foam

    SciTech Connect

    Rogers, Darren Kenneth; Plucinski, Janusz Wladyslaw

    2009-06-09

    An ablation resistant, monolithic, activated, carbon foam produced by the activation of a coal-based carbon foam through the action of carbon dioxide, ozone or some similar oxidative agent that pits and/or partially oxidizes the carbon foam skeleton, thereby significantly increasing its overall surface area and concurrently increasing its filtering ability. Such activated carbon foams are suitable for application in virtually all areas where particulate or gel form activated carbon materials have been used. Such an activated carbon foam can be fabricated, i.e. sawed, machined and otherwise shaped to fit virtually any required filtering location by simple insertion and without the need for handling the "dirty" and friable particulate activated carbon foam materials of the prior art.

  3. Super-hydrophobic fluorine containing aerogels

    DOEpatents

    Coronado, Paul R.; Poco, John F.; Hrubesh, Lawrence W.

    2007-05-01

    An aerogel material with surfaces containing fluorine atoms which exhibits exceptional hydrophobicity, or the ability to repel liquid water. Hydrophobic aerogels are efficient absorbers of solvents from water. Solvents miscible with water are separated from it because the solvents are more volatile than water and they enter the porous aerogel as a vapor across the liquid water/solid interface. Solvents that are immisicble with water are separated from it by selectively wetting the aerogel. The hydrophobic property is achieved by formulating the aerogel using fluorine containing molecules either directly by addition in the sol-gel process, or by treating a standard dried aerogel using the vapor of fluorine containing molecules.

  4. Monolayer coated aerogels and method of making

    DOEpatents

    Zemanian, Thomas Samuel; Fryxell, Glen; Ustyugov, Oleksiy A.

    2006-03-28

    Aerogels having a monolayer coating are described. The aerogel and a monolayer forming precursor are provided in a supercritical fluid, whereupon the aerogel and the monolayer forming precursor are reacted in said supercritical fluid to form a covalent bond between the aerogel and the monolayer forming precursor. Suitable aerogels are ceramic oxides such as silica, alumina, aluminosilicate, and combinations thereof. Suitable monolayer forming precursors include alkyl silanes, chlorosilanes, boranes, chloroboranes, germanes, and combinations thereof. The method may also include providing a surface preparation agent such as water, or hydroetching an aerogel to enhance the coating of the monolayer.

  5. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W.

    1996-01-01

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes .ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  6. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1995-12-19

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes{<=}1000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  7. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, R.W.

    1996-09-17

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes {<=}1,000{angstrom}, and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1,050 C to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors. 8 figs.

  8. Organic aerogels from the sol-gel polymerization of phenolic-furfural mixtures

    DOEpatents

    Pekala, Richard W.

    1995-01-01

    The sol-gel polymerization of a phenolic-furfural mixture in dilute solution leads to a highly cross-linked network that can be supercritically dried to form a high surface area foam. These porous materials have cell/pore sizes.ltoreq.1000.ANG., and although they are dark brown in color, they can be classified as a new type of aerogel. The phenolic-furfural aerogel can be pyrolyzed in an inert atmosphere at 1050.degree. C. to produce carbon aerogels. This new aerogel may be used for thermal insulation, chromatographic packing, water filtration, ion-exchange, and carbon electrodes for energy storage devices, such as batteries and double-layer capacitors.

  9. Hybrid Multifoil Aerogel Thermal Insulation

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeffrey; Paik, Jong-Ah; Jones, Steven; Nesmith, Bill

    2008-01-01

    This innovation blends the merits of multifoil insulation (MFI) with aerogel-based insulation to develop a highly versatile, ultra-low thermally conductive material called hybrid multifoil aerogel thermal insulation (HyMATI). The density of the opacified aerogel is 240 mg/cm3 and has thermal conductivity in the 20 mW/mK range in high vacuum and 25 mW/mK in 1 atmosphere of gas (such as argon) up to 800 C. It is stable up to 1,000 C. This is equal to commercially available high-temperature thermal insulation. The thermal conductivity of the aerogel is 36 percent lower compared to several commercially available insulations when tested in 1 atmosphere of argon gas up to 800 C.

  10. Nanostructural engineering of organic aerogels

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.; Lu, X.; Caps, R.; Frocle, J.

    1995-03-01

    Aerogels are a special class of open-cell foams with an ultrafine cell/pore size (<50 nm), high surface area (400-1100 M{sup 2}/g), and a solid matrix composed of interconnected colloidal-like particles or fibers with characteristic diameters of 10 nm. This paper examines the correlation between nanostructure and thermal conductivity in a series of resorcinol-formaldehyde (RF) aerogels prepared under different synthetic conditions.

  11. Aerogel Composites: Strong and Waterproof

    NASA Technical Reports Server (NTRS)

    White, Susan; Hsu, Ming-ta; Arnold, James O. (Technical Monitor)

    1999-01-01

    Aerogels are exotic materials having superior thermal and physical properties with great potential for both space and industrial uses. Although aerogels are excellent low-density insulators with unique acoustic and optical properties, their commercialization potential is currently limited by moisture absorption, fragility, and cost. This paper describes useful, easily scaled-up solutions to the first two of these three problems. The waterproofing and water-repellent method described here is a cheaper and simpler improvement over previous permanent methods.

  12. New organic aerogels based upon a phenolic-furfural reaction

    SciTech Connect

    Hrubesh, L.W.

    1994-09-01

    The aqueous polycondensation of (1) resorcinol with formaldehyde and (2) melamine with formaldehyde are two proven synthetic routes for the formation of organic aerogels. Recently, we have discovered a new type of organic aerogel based upon a phenolic-furfural (PF) reaction. This sol-gel polymerization has a major advantage over past approaches since it can be conducted in alcohol (e.g., 1-propanol), thereby eliminating the need for a solvent exchange step prior to supercritical drying from carbon dioxide. The resultant aerogels are dark brown in color and can be converted to a carbonized version upon pyrolysis in an inert atmosphere. BET surface areas of 350--600 m{sup 2}/g have been measured, and transmission electron microscopy reveals an interconnected structure of irregularly-shaped particles or platelets with {approximately}10 nm dimensions. Thermal conductivities as low as 0.015 W/m-K have been recorded for PF aerogels under ambient conditions. This paper describes the chemistry-structure-property relationships of these new materials in detail.

  13. Improved Silica Aerogel Composite Materials

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Sakamoto, Jeffrey; Jones, Steven

    2008-01-01

    A family of aerogel-matrix composite materials having thermal-stability and mechanical- integrity properties better than those of neat aerogels has been developed. Aerogels are known to be excellent thermal- and acoustic-insulation materials because of their molecular-scale porosity, but heretofore, the use of aerogels has been inhibited by two factors: (1) Their brittleness makes processing and handling difficult. (2) They shrink during production and shrink more when heated to high temperatures during use. The shrinkage and the consequent cracking make it difficult to use them to encapsulate objects in thermal-insulation materials. The underlying concept of aerogel-matrix composites is not new; the novelty of the present family of materials lies in formulations and processes that result in superior properties, which include (1) much less shrinkage during a supercritical-drying process employed in producing a typical aerogel, (2) much less shrinkage during exposure to high temperatures, and (3) as a result of the reduction in shrinkage, much less or even no cracking.

  14. Composition containing aerogel substrate loaded with tritium

    DOEpatents

    Ashley, Carol S.; Brinker, C. Jeffrey; Ellefson, Robert E.; Gill, John T.; Reed, Scott; Walko, Robert J.

    1992-01-01

    The invention provides a process for loading an aerogel substrate with tritium and the resultant compositions. According to the process, an aerogel substrate is hydrolyzed so that surface OH groups are formed. The hydrolyzed aerogel is then subjected to tritium exchange employing, for example, a tritium-containing gas, whereby tritium atoms replace H atoms of surface OH groups. OH and/or CH groups of residual alcohol present in the aerogel may also undergo tritium exchange.

  15. Aerogel composites and method of manufacture

    DOEpatents

    Cao, Wanqing; Hunt, Arlon Jason

    1999-01-01

    Disclosed herewith is a process of forming an aerogel composite which comprises introducing a gaseous material into a formed aerogel monolith or powder, and causing decomposition of said gaseous material in said aerogel in amounts sufficient to cause deposition of the decomposition products of the gas on the surfaces of the pores of the said aerogel. Also disclosed are the composites made by the process.

  16. Slotted Polyimide-Aerogel-Filled-Waveguide Arrays

    NASA Technical Reports Server (NTRS)

    Rodriguez-Solis, Rafael A.; Pacheco, Hector L.; Miranda, Felix A.; Meador, Mary Ann B.

    2013-01-01

    This presentation discussed the potential advantages of developing Slotted Waveguide Arrays using polyimide aerogels. Polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aerospace antenna systems. PI aerogels are highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties. For slotted waveguide array applications, there are significant advantages in mass that more than compensate for the slightly higher loss of the aerogel filled waveguide when compared to state of practice commercial waveguide.

  17. Adsorption of herbicides using activated carbons

    SciTech Connect

    Derbyshire, F.; Jagtoyan, M.; Lafferty, C.; Kimber, G.

    1996-10-01

    This work describes development of a series of novel activated carbon materials and their testing for possible water treatment applications by studying the adsorption of sodium pentachlorphenolate, PCP (a common herbicide/wood preservative). Although the application of activated carbons is an established technology for the treatment of public water supplies, there is a growing need for materials with higher selectivity and adsorptive capacities as well as high abrasion resistance. The materials that will be discussed include extruded wood-derived carbons with novel pore size distributions and high hardness, as well as activated carbon fiber composites. Comparisons will be made with commercial granular water treatment carbons.

  18. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  19. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  20. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  1. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  2. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  3. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  4. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 6 2011-04-01 2011-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  5. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silica aerogel. 182.1711 Section 182.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  6. 21 CFR 182.1711 - Silica aerogel.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Silica aerogel. 182.1711 Section 182.1711 Food and... GENERALLY RECOGNIZED AS SAFE Multiple Purpose GRAS Food Substances § 182.1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of...

  7. 21 CFR 582.1711 - Silica aerogel.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Silica aerogel. 582.1711 Section 582.1711 Food and....1711 Silica aerogel. (a) Product. Silica aerogel as a finely powdered microcellular silica foam having a minimum silica content of 89.5 percent. (b) (c) Limitations, restrictions, or explanation....

  8. A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams.

    PubMed

    Opachich, Y P; Koch, J A; Haugh, M J; Romano, E; Lee, J J; Huffman, E; Weber, F A; Bowers, J W; Benedetti, L R; Wilson, M; Prisbrey, S T; Wehrenberg, C E; Baumann, T F; Lenhardt, J M; Cook, A; Arsenlis, A; Park, H-S; Remington, B A

    2016-07-01

    A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX-6 (C20H30) aerogel are discussed in this manuscript. PMID:27475564

  9. A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams.

    PubMed

    Opachich, Y P; Koch, J A; Haugh, M J; Romano, E; Lee, J J; Huffman, E; Weber, F A; Bowers, J W; Benedetti, L R; Wilson, M; Prisbrey, S T; Wehrenberg, C E; Baumann, T F; Lenhardt, J M; Cook, A; Arsenlis, A; Park, H-S; Remington, B A

    2016-07-01

    A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ∼10.3% accuracy with ∼30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX-6 (C20H30) aerogel are discussed in this manuscript.

  10. A multi-wavelength, high-contrast contact radiography system for the study of low-density aerogel foams

    NASA Astrophysics Data System (ADS)

    Opachich, Y. P.; Koch, J. A.; Haugh, M. J.; Romano, E.; Lee, J. J.; Huffman, E.; Weber, F. A.; Bowers, J. W.; Benedetti, L. R.; Wilson, M.; Prisbrey, S. T.; Wehrenberg, C. E.; Baumann, T. F.; Lenhardt, J. M.; Cook, A.; Arsenlis, A.; Park, H.-S.; Remington, B. A.

    2016-07-01

    A multi-wavelength, high contrast contact radiography system has been developed to characterize density variations in ultra-low density aerogel foams. These foams are used to generate a ramped pressure drive in materials strength experiments at the National Ignition Facility and require precision characterization in order to reduce errors in measurements. The system was used to characterize density variations in carbon and silicon based aerogels to ˜10.3% accuracy with ˜30 μm spatial resolution. The system description, performance, and measurement results collected using a 17.8 mg/cc carbon based JX-6 (C20H30) aerogel are discussed in this manuscript.

  11. Aerogel Derived Nanostructured Thermoelectric Materials

    SciTech Connect

    Wendell E Rhine, PI; Dong, Wenting; Greg Caggiano, PM

    2010-10-08

    America’s dependence on foreign sources for fuel represents a economic and security threat for the country. These non renewable resources are depleting, and the effects of pollutants from fuels such as oil are reaching a problematic that affects the global community. Solar concentration power (SCP) production systems offer the opportunity to harness one of the United States’ most under utilized natural resources; sunlight. While commercialization of this technology is increasing, in order to become a significant source of electricity production in the United States the costs of deploying and operating SCP plants must be further reduced. Parabolic Trough SCP technologies are close to meeting energy production cost levels that would raise interest in the technology and help accelerate its adoption as a method to produce a significant portion of the Country’s electric power needs. During this program, Aspen Aerogels will develop a transparent aerogel insulation that can replace the costly vacuum insulation systems that are currently used in parabolic trough designs. During the Phase I program, Aspen Aerogels will optimize the optical and thermal properties of aerogel to meet the needs of this application. These properties will be tested, and the results will be used to model the performance of a parabolic trough HCE system which uses this novel material in place of vacuum. During the Phase II program, Aspen Aerogels will scale up this technology. Together with industry partners, Aspen Aerogels will build and test a prototype Heat Collection Element that is insulated with the novel transparent aerogel material. This new device will find use in parabolic trough SCP applications.

  12. Composite Aerogel Multifoil Protective Shielding

    NASA Technical Reports Server (NTRS)

    Jones, Steven M.

    2013-01-01

    New technologies are needed to survive the temperatures, radiation, and hypervelocity particles that exploration spacecraft encounter. Multilayer insulations (MLIs) have been used on many spacecraft as thermal insulation. Other materials and composites have been used as micrometeorite shielding or radiation shielding. However, no material composite has been developed and employed as a combined thermal insulation, micrometeorite, and radiation shielding. By replacing the scrims that have been used to separate the foil layers in MLIs with various aerogels, and by using a variety of different metal foils, the overall protective performance of MLIs can be greatly expanded to act as thermal insulation, radiation shielding, and hypervelocity particle shielding. Aerogels are highly porous, low-density solids that are produced by the gelation of metal alkoxides and supercritical drying. Aerogels have been flown in NASA missions as a hypervelocity particle capture medium (Stardust) and as thermal insulation (2003 MER). Composite aerogel multifoil protective shielding would be used to provide thermal insulation, while also shielding spacecraft or components from radiation and hypervelocity particle impacts. Multiple layers of foil separated by aerogel would act as a thermal barrier by preventing the transport of heat energy through the composite. The silica aerogel would act as a convective and conductive thermal barrier, while the titania powder and metal foils would absorb and reflect the radiative heat. It would also capture small hypervelocity particles, such as micrometeorites, since it would be a stuffed, multi-shock Whipple shield. The metal foil layers would slow and break up the impacting particles, while the aerogel layers would convert the kinetic energy of the particles to thermal and mechanical energy and stop the particles.

  13. SORPTION OF ELEMENTAL MERCURY BY ACTIVATED CARBONS

    EPA Science Inventory

    The mechanisms and rate of elemental mercury (HgO) capture by activated carbons have been studied using a bench-scale apparatus. Three types of activated carbons, two of which are thermally activated (PC-100 and FGD) and one with elemental sulfur (S) impregnated in it (HGR), were...

  14. Purity and cleanness of aerogel as a cosmic dust capture medium

    NASA Technical Reports Server (NTRS)

    Tsou, P.; Fleming, R. H.; Lindley, P. M.; Craig, A. Y.; Blake, D.

    1994-01-01

    The capability for capturing micrometeoroids intact through laboratory simulations and in space in passive underdense silica aerogel offers a valuable tool for cosmic dust research. The integrity of the sample handling medium can substantially modify the integrity of the sample. Intact capture is a violent hypervelocity event: the integrity of the capturing medium can cause even greater modification of the sample. Doubts of the suitability of silica aerogel as a capture medium were raised at the 20th LPSC, and questions were raised again at the recent workshop on Particle Capture, Recovery, and Velocity Trajectory Measurement Technologies. Assessment of aerogel's volatile components and carbon contents have been made. We report the results of laboratory measurements of the purity and cleanliness of silica aerogel used for several Sample Return Experiments flown on the Get Away Special program.

  15. Reinforcement of bacterial cellulose aerogels with biocompatible polymers.

    PubMed

    Pircher, N; Veigel, S; Aigner, N; Nedelec, J M; Rosenau, T; Liebner, F

    2014-10-13

    Bacterial cellulose (BC) aerogels, which are fragile, ultra-lightweight, open-porous and transversally isotropic materials, have been reinforced with the biocompatible polymers polylactic acid (PLA), polycaprolactone (PCL), cellulose acetate (CA), and poly(methyl methacrylate) (PMMA), respectively, at varying BC/polymer ratios. Supercritical carbon dioxide anti-solvent precipitation and simultaneous extraction of the anti-solvent using scCO2 have been used as core techniques for incorporating the secondary polymer into the BC matrix and to convert the formed composite organogels into aerogels. Uniaxial compression tests revealed a considerable enhancement of the mechanical properties as compared to BC aerogels. Nitrogen sorption experiments at 77K and scanning electron micrographs confirmed the preservation (or even enhancement) of the surface-area-to-volume ratio for most of the samples. The formation of an open-porous, interpenetrating network of the second polymer has been demonstrated by treatment of BC/PMMA hybrid aerogels with EMIM acetate, which exclusively extracted cellulose, leaving behind self-supporting organogels.

  16. Study on Thermal Conductivities of Aromatic Polyimide Aerogels.

    PubMed

    Feng, Junzong; Wang, Xin; Jiang, Yonggang; Du, Dongxuan; Feng, Jian

    2016-05-25

    Polyimide aerogels for low density thermal insulation materials were produced by 4,4'-diaminodiphenyl ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride, cross-linked with 1,3,5-triaminophenoxybenzene. The densities of obtained polyimide aerogels are between 0.081 and 0.141 g cm(-3), and the specific surface areas are between 288 and 322 m(2) g(-1). The thermal conductivities were measured by a Hot Disk thermal constant analyzer. The value of the measured thermal conductivity under carbon dioxide atmosphere is lower than that under nitrogen atmosphere. Under pressure of 5 Pa at -130 °C, the thermal conductivity is the lowest, which is 8.42 mW (m K)(-1). The polyimide aerogels have lower conductivity [30.80 mW (m K)(-1)], compared to the value for other organic foams (polyurethane foam, phenolic foam, and polystyrene foam) with similar apparent densities under ambient pressure at 25 °C. The results indicate that polyimide aerogel is an ideal insulation material for aerospace and other applications.

  17. Reinforcement of bacterial cellulose aerogels with biocompatible polymers

    PubMed Central

    Pircher, N.; Veigel, S.; Aigner, N.; Nedelec, J.M.; Rosenau, T.; Liebner, F.

    2014-01-01

    Bacterial cellulose (BC) aerogels, which are fragile, ultra-lightweight, open-porous and transversally isotropic materials, have been reinforced with the biocompatible polymers polylactic acid (PLA), polycaprolactone (PCL), cellulose acetate (CA), and poly(methyl methacrylate) (PMMA), respectively, at varying BC/polymer ratios. Supercritical carbon dioxide anti-solvent precipitation and simultaneous extraction of the anti-solvent using scCO2 have been used as core techniques for incorporating the secondary polymer into the BC matrix and to convert the formed composite organogels into aerogels. Uniaxial compression tests revealed a considerable enhancement of the mechanical properties as compared to BC aerogels. Nitrogen sorption experiments at 77 K and scanning electron micrographs confirmed the preservation (or even enhancement) of the surface-area-to-volume ratio for most of the samples. The formation of an open-porous, interpenetrating network of the second polymer has been demonstrated by treatment of BC/PMMA hybrid aerogels with EMIM acetate, which exclusively extracted cellulose, leaving behind self-supporting organogels. PMID:25037381

  18. Ultrafast Sol-Gel Synthesis of Graphene Aerogel Materials

    SciTech Connect

    Lim, Mathew; Hu, Matthew; Manandhar, Sandeep; Sakshaug, Avery; Strong, Adam; Riley, Leah; Pauzauskie, Peter J.

    2015-12-01

    Graphene aerogels derived from graphene-oxide (GO) starting materials recently have been shown to exhibit a combination of high electrical conductivity, chemical stability, and low cost that has enabled a range of electrochemical applications. Standard synthesis protocols for manufacturing graphene aerogels require the use of sol-gel chemical reactions that are maintained at high temperatures for long periods of time ranging from 12 hours to several days. Here we report an ultrafast, acid-catalyzed sol-gel formation process in acetonitrile in which wet GO-loaded gels are realized within 2 hours at temperatures below 45°C. Spectroscopic and electrochemical analysis following supercritical drying and pyrolysis confirms the reduction of the GO in the aerogels to sp2 carbon crystallites with no residual carbon–nitrogen bonds from the acetonitrile or its derivatives. This rapid synthesis enhances the prospects for large-scale manufacturing of graphene aerogels for use in numerous applications including sorbents for environmental toxins, support materials for electrocatalysis, and high-performance electrodes for electrochemical capacitors and solar cells.

  19. Study on Thermal Conductivities of Aromatic Polyimide Aerogels.

    PubMed

    Feng, Junzong; Wang, Xin; Jiang, Yonggang; Du, Dongxuan; Feng, Jian

    2016-05-25

    Polyimide aerogels for low density thermal insulation materials were produced by 4,4'-diaminodiphenyl ether and 3,3',4,4'-biphenyltetracarboxylic dianhydride, cross-linked with 1,3,5-triaminophenoxybenzene. The densities of obtained polyimide aerogels are between 0.081 and 0.141 g cm(-3), and the specific surface areas are between 288 and 322 m(2) g(-1). The thermal conductivities were measured by a Hot Disk thermal constant analyzer. The value of the measured thermal conductivity under carbon dioxide atmosphere is lower than that under nitrogen atmosphere. Under pressure of 5 Pa at -130 °C, the thermal conductivity is the lowest, which is 8.42 mW (m K)(-1). The polyimide aerogels have lower conductivity [30.80 mW (m K)(-1)], compared to the value for other organic foams (polyurethane foam, phenolic foam, and polystyrene foam) with similar apparent densities under ambient pressure at 25 °C. The results indicate that polyimide aerogel is an ideal insulation material for aerospace and other applications. PMID:27149155

  20. Hybrid aerogel preparations as drug delivery matrices for low water-solubility drugs.

    PubMed

    Veres, Peter; López-Periago, Ana M; Lázár, István; Saurina, Javier; Domingo, Concepción

    2015-12-30

    A comprehensive study of 14 hybrid aerogels of different composition with applications in drug delivery has been carried out. The overall objective was to modulate the release behavior of drug-impregnated aerogels, from an almost instantaneous release to a semi-retarded delivery prolonged during several hours, through internal surface functionalization. The designed hybrid aerogels were composed of silica and gelatin and functionalized with either phenyl, long (16) hydrocarbon chain or methyl moiety. As model systems, three class II active agents (pKa<5.5), ibuprofen, ketoprofen and triflusal, were chosen to impregnate the aerogels. The work relied on the use of supercritical fluid technology for both the synthesis and functionalization of the hybrid aerogels, as well as for the impregnation with an active agent using supercritical CO2 as a solvent. For the impregnated aerogels, in vitro release profiles were recorded under gastric and intestinal pH-conditions using HPLC techniques. The release behavior observed for the three studied drugs was explained considering the measured dissolution profiles of the crystalline drugs, the aerogel composition and its functionalization. Such features are considered of great interest to tailor the bioavailability of drugs with low water solubility.

  1. [Study on influence between activated carbon property and immobilized biological activated carbon purification effect].

    PubMed

    Wang, Guang-zhi; Li, Wei-guang; He, Wen-jie; Han, Hong-da; Ding, Chi; Ma, Xiao-na; Qu, Yan-ming

    2006-10-01

    By means of immobilizing five kinds of activated carbon, we studied the influence between the chief activated carbon property items and immobilized bioactivated carbon (IBAC) purification effect with the correlation analysis. The result shows that the activated carbon property items which the correlation coefficient is up 0.7 include molasses, abrasion number, hardness, tannin, uniform coefficient, mean particle diameter and effective particle diameter; the activated carbon property items which the correlation coefficient is up 0.5 include pH, iodine, butane and tetrachloride. In succession, the partial correlation analysis shows that activated carbon property items mostly influencing on IBAC purification effect include molasses, hardness, abrasion number, uniform coefficient, mean particle diameter and effective particle diameter. The causation of these property items bringing influence on IBAC purification is that the activated carbon holes distribution (representative activated carbon property item is molasses) provides inhabitable location and adjust food for the dominance bacteria; the mechanical resist-crash property of activated carbon (representative activated carbon property items: abrasion number and hardness) have influence on the stability of biofilm; and the particle diameter size and distribution of activated carbon (representative activated carbon property items: uniform coefficient, mean particle diameter and effective particle diameter) can directly affect the force of water in IBAC filter bed, which brings influence on the dominance bacteria immobilizing on activated carbon.

  2. Preparation of activated carbon by chemical activation under vacuum.

    PubMed

    Juan, Yang; Ke-Qiang, Qiu

    2009-05-01

    Activated carbons especially used for gaseous adsorption were prepared from Chinesefir sawdust by zinc chloride activation under vacuum condition. The micropore structure, adsorption properties, and surface morphology of activated carbons obtained under atmosphere and vacuum were investigated. The prepared activated carbons were characterized by SEM, FTIR, and nitrogen adsorption. It was found that the structure of the starting material is kept after activation. The activated carbon prepared under vacuum exhibited higher values of the BET surface area (up to 1079 m2 g(-1)) and total pore volume (up to 0.5665 cm3 g(-1)) than those of the activated carbon obtained under atmosphere. This was attributed to the effect of vacuum condition that reduces oxygen in the system and limits the secondary reaction of the organic vapor. The prepared activated carbon has well-developed microstructure and high microporosity. According to the data obtained, Chinese fir sawdust is a suitable precursor for activated carbon preparation. The obtained activated carbon could be used as a low-cost adsorbent with favorable surface properties. Compared with the traditional chemical activation, vacuum condition demands less energy consumption, simultaneity, and biomass-oil is collected in the procedure more conveniently. FTIR analysis showed that heat treatment would result in the aromatization of the carbon structure. PMID:19534162

  3. Biodegradable pectin/clay aerogels.

    PubMed

    Chen, Hong-Bing; Chiou, Bor-Sen; Wang, Yu-Zhong; Schiraldi, David A

    2013-03-13

    Biodegradable, foamlike materials based on renewable pectin and sodium montmorillonite clay were fabricated through a simple, environmentally friendly freeze-drying process. The addition of multivalent cations (Ca(2+) and Al(3+)) resulted in apparent cross-linking of the polymer and enhancement of aerogel properties. The compressive properties increased as the solid contents (both pectin and clay) increased; moduli in the range of 0.04-114 MPa were obtained for materials with bulk densities ranging from 0.03 g/cm(3) to 0.19 g/cm(3), accompanied by microstructural changes from a lamellar structure to a cellular structure. Biodegradability of the aerogels was investigated by detecting CO2 release for 4 weeks in compost media. The results revealed that pectin aerogels possess higher biodegradation rates than wheat starch, which is often used as a standard for effective biodegradation. The addition of clay and multivalent cations surprisingly increased the biodegradation rates. PMID:23406325

  4. Polyimide Cellulose Nanocrystal Composite Aerogels

    NASA Technical Reports Server (NTRS)

    Nguyen, Baochau N.; Meador, Mary Ann; Rowan, Stuart; Cudjoe, Elvis; Sandberg, Anna

    2014-01-01

    Polyimide (PI) aerogels are highly porous solids having low density, high porosity and low thermal conductivity with good mechanical properties. They are ideal for various applications including use in antenna and insulation such as inflatable decelerators used in entry, decent and landing operations. Recently, attention has been focused on stimuli responsive materials such as cellulose nano crystals (CNCs). CNCs are environmentally friendly, bio-renewable, commonly found in plants and the dermis of sea tunicates, and potentially low cost. This study is to examine the effects of CNC on the polyimide aerogels. The CNC used in this project are extracted from mantle of a sea creature called tunicates. A series of polyimide cellulose nanocrystal composite aerogels has been fabricated having 0-13 wt of CNC. Results will be discussed.

  5. Sorption of boron trifluoride by activated carbons

    SciTech Connect

    Polevoi, A.S.; Petrenko, A.E.

    1988-01-10

    The sorption of born trifluoride on AG-3, SKT, SKT-3, SKT-7, SKT-4A, SKT-6A, and SKT-2B carbons was investigated. The sorption isotherms for both vapors and gas were determined volumetrically. The coefficients of two equations described the sorption of BF/sub 3/ in the sorption of BF/sub 3/ on active carbons. Heats of sorption of BF/sub 3/ on the activated carbons are shown and the sorption isotherms and temperature dependences of the equilibrium pressure of BF/sub 3/ for activated carbons were presented. The values of the heats of sorption indicated the weak character of the reaction of BF/sub 3/ with the surface of the carbons. The equations can be used for calculating the phase equilibrium of BF/sub 3/ on carbons in a wider range of temperatures and pressures.

  6. Catalytic Growth of Macroscopic Carbon Nanofibers Bodies with Activated Carbon

    SciTech Connect

    Abdullah, N.; Muhammad, I. S.; Hamid, S. B. Abd.; Rinaldi, A.; Su, D. S.; Schlogl, R.

    2009-06-01

    Carbon-carbon composite of activated carbon and carbon nanofibers have been synthesized by growing Carbon nanofiber (CNF) on Palm shell-based Activated carbon (AC) with Ni catalyst. The composites are in an agglomerated shape due to the entanglement of the defective CNF between the AC particles forming a macroscopic body. The macroscopic size will allow the composite to be used as a stabile catalyst support and liquid adsorbent. The preparation of CNT/AC nanocarbon was initiated by pre-treating the activated carbon with nitric acid, followed by impregnation of 1 wt% loading of nickel (II) nitrate solutions in acetone. The catalyst precursor was calcined and reduced at 300 deg. C for an hour in each step. The catalytic growth of nanocarbon in C{sub 2}H{sub 4}/H{sub 2} was carried out at temperature of 550 deg. C for 2 hrs with different rotating angle in the fluidization system. SEM and N{sub 2} isotherms show the level of agglomeration which is a function of growth density and fluidization of the system. The effect of fluidization by rotating the reactor during growth with different speed give a significant impact on the agglomeration of the final CNF/AC composite and thus the amount of CNFs produced. The macrostructure body produced in this work of CNF/AC composite will have advantages in the adsorbent and catalyst support application, due to the mechanical and chemical properties of the material.

  7. Making Activated Carbon by Wet Pressurized Pyrolysis

    NASA Technical Reports Server (NTRS)

    Fisher, John W.; Pisharody, Suresh; Wignarajah, K.; Moran, Mark

    2006-01-01

    A wet pressurized pyrolysis (wet carbonization) process has been invented as a means of producing activated carbon from a wide variety of inedible biomass consisting principally of plant wastes. The principal intended use of this activated carbon is room-temperature adsorption of pollutant gases from cooled incinerator exhaust streams. Activated carbon is highly porous and has a large surface area. The surface area depends strongly on the raw material and the production process. Coconut shells and bituminous coal are the primary raw materials that, until now, were converted into activated carbon of commercially acceptable quality by use of traditional production processes that involve activation by use of steam or carbon dioxide. In the wet pressurized pyrolysis process, the plant material is subjected to high pressure and temperature in an aqueous medium in the absence of oxygen for a specified amount of time to break carbon-oxygen bonds in the organic material and modify the structure of the material to obtain large surface area. Plant materials that have been used in demonstrations of the process include inedible parts of wheat, rice, potato, soybean, and tomato plants. The raw plant material is ground and mixed with a specified proportion of water. The mixture is placed in a stirred autoclave, wherein it is pyrolized at a temperature between 450 and 590 F (approximately between 230 and 310 C) and a pressure between 1 and 1.4 kpsi (approximately between 7 and 10 MPa) for a time between 5 minutes and 1 hour. The solid fraction remaining after wet carbonization is dried, then activated at a temperature of 500 F (260 C) in nitrogen gas. The activated carbon thus produced is comparable to commercial activated carbon. It can be used to adsorb oxides of sulfur, oxides of nitrogen, and trace amounts of hydrocarbons, any or all of which can be present in flue gas. Alternatively, the dried solid fraction can be used, even without the activation treatment, to absorb

  8. Enhanced oxidation of air contaminants on an ultra-low density UV-accessible aerogel photocatalyst

    SciTech Connect

    Dreyer, M.; Newman, G.K.; Lobban, L.; Kersey, S.J.; Wang, R.; Harwell, J.H.

    1997-12-31

    This research developed new forms of photocatalysts that could potentially move photocatalytic degradation of air contaminants into the main stream of industrially used remediation technologies. Tests of the photocatalytic activity of the TiO{sub 2} aerogel catalysts have been carried out using both acetone and methane as the air contaminant. For comparison, the same tests were carried out on a standard (non-aerogel) anatase powder. Despite having very low crystallinity, the aerogel decontaminates the air far more effectively than an equal volume of the anatase powder which indicates that a much larger fraction of the aerogel is activated by the UV light. Experimental data were used to determine adsorption equilibrium constants for acetone, and to determine reaction rate constants assuming a Langmuir-Hinshelwood type rate expression.

  9. Biodegradable Pectin/clay Aerogels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodegradable, foamlike materials based on renewable pectin and sodium montmorillonite clay were fabricated through a simple, environmentally friendly freeze-drying process. Addition of multivalent cations (Ca2+ and Al3+) resulted in apparent crosslinking of the polymer, and enhancement of aerogel p...

  10. Iron Aerogel and Xerogel Catalysts for Fischer-Tropsch Synthesis of Diesel Fuel

    SciTech Connect

    Bali, S.; Huggins, F; Huffman, G; Ernst, R; Pugmire, R; Eyring, E

    2009-01-01

    Iron aerogels, potassium-doped iron aerogels, and potassium-doped iron xerogels have been synthesized and characterized and their catalytic activity in the Fischer-Tropsch (F-T) reaction has been studied. Iron aerogels and xerogels were synthesized by polycondensation of an ethanolic solution of iron(III) chloride hexahydrate with propylene oxide which acts as a proton scavenger for the initiation of hydrolysis and polycondensation. Potassium was incorporated in the iron aerogel and iron xerogel by adding aqueous K{sub 2}CO{sub 3} to the ethanolic solutions of the Fe(III) precursor prior to addition of propylene oxide. Fischer-Tropsch activities of the catalysts were tested in a fixed bed reactor at a pressure of 100 psi with a H{sub 2}:CO ratio of 2:1. Iron aerogels were found to be active for F-T synthesis, and their F-T activities increased on addition of a K containing promoter. Moessbauer spectroscopic data are consistent with an open, nonrigid iron(III) aerogel structure progressing to an iron carbide/metallic iron catalyst via agglomeration as the F-T synthesis proceeds in the course of a 35 h fixed bed reaction test.

  11. Synthesis and Properties of Cross-Linked Polyamide Aerogels

    NASA Technical Reports Server (NTRS)

    Williams, Jarrod C.; Meador, Mary Ann; McCorkle, Linda

    2015-01-01

    We report the first synthesis of cross-linked polyamide aerogels through step growth polymerization using a combination of diamines, diacid chloride and triacid chloride. Polyamide oligomers endcapped with amines are prepared as stable solutions in N-methylpyrrolidinone from several different diamine precursors and 1,3-benzenedicarbonyl dichloride. Addition of 1,3,5-benzenetricarbonyl trichloride yields gels which form in under five minutes according to the scheme shown. Solvent exchange of the gels into ethanol, followed by drying using supercritical CO2 extraction gives colorless aerogels with densities around 0.1 to 0.2 gcm3. Thicker monolithes of the polyamide aerogels are stiff and strong, while thin films of certain formulations are highly flexible, durable, and even translucent. These materials may have use as insulation for deployable space structures, rovers, habitats or extravehicular activity suits as well as in many terrestrial applications. Strucure property relationships of the aerogels, including surface area, mechanical properties, and thermal conductivity will be discussed.

  12. The transport properties of activated carbon fibers

    SciTech Connect

    di Vittorio, S.L. . Dept. of Materials Science and Engineering); Dresselhaus, M.S. . Dept. of Electrical Engineering and Computer Science Massachusetts Inst. of Tech., Cambridge, MA . Dept. of Physics); Endo, M. . Dept. of Electrical Engineering); Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons. 19 refs., 4 figs.

  13. The Transport Properties of Activated Carbon Fibers

    DOE R&D Accomplishments Database

    di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

    1990-07-01

    The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

  14. ACTIVATED CARBON FROM LIGNITE FOR WATER TREATMENT

    SciTech Connect

    Edwin S. Olson; Daniel J. Stepan

    2000-07-01

    High concentrations of humate in surface water result in the formation of excess amounts of chlorinated byproducts during disinfection treatment. These precursors can be removed in water treatment prior to disinfection using powdered activated carbon. In the interest of developing a more cost-effective method for removal of humates in surface water, a comparison of the activities of carbons prepared from North Dakota lignites with those of commercial carbons was conducted. Previous studies indicated that a commercial carbon prepared from Texas lignite (Darco HDB) was superior to those prepared from bituminous coals for water treatment. That the high alkali content of North Dakota lignites would result in favorable adsorptive properties for the very large humate molecules was hypothesized, owing to the formation of larger pores during activation. Since no standard humate test has been previously developed, initial adsorption testing was performed using smaller dye molecules with various types of ionic character. With the cationic dye, methylene blue, a carbon prepared from a high-sodium lignite (HSKRC) adsorbed more dye than the Darco HDB. The carbon from the low-sodium lignite was much inferior. With another cationic dye, malachite green, the Darco HDB was slightly better. With anionic dyes, methyl red and azocarmine-B, the results for the HSKRC and Darco HDB were comparable. A humate test was developed using Aldrich humic acid. The HSKRC and the Darco HDB gave equally high adsorption capacities for the humate (138 mg/g), consistent with the similarities observed in earlier tests. A carbon prepared from a high-sodium lignite from a different mine showed an outstanding improvement (201 mg/g). The carbons prepared from the low-sodium lignites from both mines showed poor adsorption capacities for humate. Adsorption isotherms were performed for the set of activated carbons in the humate system. These exhibited a complex behavior interpreted as resulting from two types

  15. Anisotropically structured magnetic aerogel monoliths

    NASA Astrophysics Data System (ADS)

    Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

    2014-10-01

    Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and

  16. Aerogel-Positronium Technology for the Detection of Small Quantities of Organic and/or Toxic Materials

    NASA Technical Reports Server (NTRS)

    Petkov, Mihail P.; Jones, Steven M.

    2010-01-01

    The Ps-aerogel system [Ps is positronium (an electron-positron-hydrogen-like atom)] has been evaluated and optimized as a potential tool for planetary exploration missions. Different configurations of use were assessed, and the results provide a quantitative measure of the expected performance. The aerogel density is first optimized to attain maximum production of Ps that reaches the pores of the aerogel. This has been accomplished, and the optimum aerogel density is .70 mg/cm3. The aerogel is used as a concentrator for target volatile moieties, which accumulate in its open porosity over an extended period of time. For the detection of the accumulated materials, the use of Ps as a probe for the environment at the pore surface, has been proposed. This concept is based on two steps: (1) using aerogel to produce Ps and (2) using the propensity of Ps to interact differently with organic and inorganic matter. The active area of such a detector will comprise aerogel with a certain density, specific surface area, and gas permeability optimized for Ps production and gas diffusion and adsorption. The aerogel is a natural adsorber of organic molecules, which adhere to its internal surface, where their presence is detected by the Ps probe. Initial estimates indicate that, e.g., trace organic molecules in the Martian atmosphere, can be detected at the ppm level, which rivals current methods having significantly higher complexity, volume, mass, and power consumption (e.g. Raman, IR).

  17. Dielectric properties and electronic applications of aerogels

    SciTech Connect

    Hrubesh, L.W.; Pekala, R.W.

    1993-07-01

    Among their other exceptional properties, aerogels also exhibits unusual dielectric properties due to their nano-sized structures and high porosities. For example, our measurements of the dielectric constants and loss tangents for several aerogel varieties at microwave frequencies show that they both vary linearly with the aerogel density, indicating that the dielectric behavior of aerogels is more gas-like than solid-like. We have also measured the dielectric strength of silica aerogels and find that they are better than ceramics for high voltage insulation. The low dielectric constants and loss tangents of aerogels, along with their controllable thermal expansion properties, make them desirable materials for use as thin films in high speed integrated digital and microwave circuitry.

  18. Aerogel Blanket Insulation Materials for Cryogenic Applications

    NASA Astrophysics Data System (ADS)

    Coffman, B. E.; Fesmire, J. E.; White, S.; Gould, G.; Augustynowicz, S.

    2010-04-01

    Aerogel blanket materials for use in thermal insulation systems are now commercially available and implemented by industry. Prototype aerogel blanket materials were presented at the Cryogenic Engineering Conference in 1997 and by 2004 had progressed to full commercial production by Aspen Aerogels. Today, this new technology material is providing superior energy efficiencies and enabling new design approaches for more cost-effective cryogenic systems. Aerogel processing technology and methods are continuing to improve, offering a tailorable array of product formulations for many different thermal and environmental requirements. Many different varieties and combinations of aerogel blankets have been characterized using insulation test cryostats at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Detailed thermal conductivity data for a select group of materials are presented for engineering use. Heat transfer evaluations for the entire vacuum pressure range, including ambient conditions, are given. Examples of current cryogenic applications of aerogel blanket insulation are also given.

  19. Method for producing metal oxide aerogels

    DOEpatents

    Tillotson, T.M.; Poco, J.F.; Hrubesh, L.W.; Thomas, I.M.

    1995-04-25

    A two-step hydrolysis-condensation method was developed to form metal oxide aerogels of any density, including densities of less than 0.003g/cm{sup 3} and greater than 0.27g/cm{sup 3}. High purity metal alkoxide is reacted with water, alcohol solvent, and an additive to form a partially condensed metal intermediate. All solvent and reaction-generated alcohol is removed, and the intermediate is diluted with a nonalcoholic solvent. The intermediate can be stored for future use to make aerogels of any density. The aerogels are formed by reacting the intermediate with water, nonalcoholic solvent, and a catalyst, and extracting the nonalcoholic solvent directly. The resulting monolithic aerogels are hydrophobic and stable under atmospheric conditions, and exhibit good optical transparency, high clarity, and homogeneity. The aerogels have high thermal insulation capacity, high porosity, mechanical strength and stability, and require shorter gelation times than aerogels formed by conventional methods. 8 figs.

  20. Method for producing metal oxide aerogels

    DOEpatents

    Tillotson, Thomas M.; Poco, John F.; Hrubesh, Lawrence W.; Thomas, Ian M.

    1995-01-01

    A two-step hydrolysis-condensation method was developed to form metal oxide aerogels of any density, including densities of less than 0.003g/cm.sup.3 and greater than 0.27g/cm.sup.3. High purity metal alkoxide is reacted with water, alcohol solvent, and an additive to form a partially condensed metal intermediate. All solvent and reaction-generated alcohol is removed, and the intermediate is diluted with a nonalcoholic solvent. The intermediate can be stored for future use to make aerogels of any density. The aerogels are formed by reacting the intermediate with water, nonalcoholic solvent, and a catalyst, and extracting the nonalcoholic solvent directly. The resulting monolithic aerogels are hydrophobic and stable under atmospheric conditions, and exhibit good optical transparency, high clarity, and homogeneity. The aerogels have high thermal insulation capacity, high porosity, mechanical strength and stability, and require shorter gelation times than aerogels formed by conventional methods.

  1. Ultralight and highly compressible graphene aerogels.

    PubMed

    Hu, Han; Zhao, Zongbin; Wan, Wubo; Gogotsi, Yury; Qiu, Jieshan

    2013-04-18

    Chemically converted graphene aerogels with ultralight density and high compressibility are prepared by diamine-mediated functionalization and assembly, followed by microwave irradiation. The resulting graphene aerogels with density as low as 3 mg cm(-3) show excellent resilience and can completely recover after more than 90% compression. The ultralight graphene aerogels possessing high elasticity are promising as compliant and energy-absorbing materials. PMID:23418081

  2. 3D Printing of Graphene Aerogels.

    PubMed

    Zhang, Qiangqiang; Zhang, Feng; Medarametla, Sai Pradeep; Li, Hui; Zhou, Chi; Lin, Dong

    2016-04-01

    3D printing of a graphene aerogel with true 3D overhang structures is highlighted. The aerogel is fabricated by combining drop-on-demand 3D printing and freeze casting. The water-based GO ink is ejected and freeze-cast into designed 3D structures. The lightweight (<10 mg cm(-3) ) 3D printed graphene aerogel presents superelastic and high electrical conduction.

  3. Sorption Properties of Aerogel in Liquid Nitrogen

    NASA Technical Reports Server (NTRS)

    Johnson, Wesley L.

    2006-01-01

    Aerogel products are now available as insulation materials of the future. The Cryogenics Test Laboratory at the NASA Kennedy Space Center is developing aerogel-based thermal insulation systems for space launch applications. Aerogel beads (Cabot Nanogel ) and aerogel blankets (Aspen Aerogels Spaceloft ) have outstanding ambient pressure thermal performance that makes them useful for applications where sealing is not possible. Aerogel beads are open-celled silicone dioxide and have tiny pores that run throughout the body of the bead. It has also recently been discovered that aerogel beads can be used as a filtering device for aqueous compounds at room temperature. With their hydrophobic covering, the beads absorb any non-polar substance and they can be chemically altered to absorb hot gases. The combination of the absorption and cryogenic insulating properties of aerogel beads have never been studied together. For future cryogenic insulation applications, it is crucial to know how the beads react while immersed in cryogenic liquids, most notably liquid nitrogen. Aerogel beads in loose-fill situation and aerogel blankets with composite fiber structure have been tested for absorption properties. Depending on the type of aerogel used and the preparation, preliminary results show the material can absorb up to seven times its own weight of liquid nitrogen, corresponding to a volumetric ratio of 0.70 (unit volume nitrogen per unit volume aerogel). These tests allow for an estimate on how much insulation is needed in certain situations. The theory behind the different processes of sorption is necessary for a better understanding of the preparation of the beads before they are used in an insulation system.

  4. Aerogels Insulate Missions and Consumer Products

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Aspen Aerogels, of Northborough, Massachusetts, worked with NASA through an SBIR contract with Kennedy Space Center to develop a robust, flexible form of aerogel for cryogenic insulation for space shuttle launch applications. The company has since used the same manufacturing process developed under the SBIR award to expand its product offerings into the more commercial realms, making the naturally fragile aerogel available for the first time as a standard insulation that can be handled and installed just like standard insulation.

  5. 3D Printing of Graphene Aerogels.

    PubMed

    Zhang, Qiangqiang; Zhang, Feng; Medarametla, Sai Pradeep; Li, Hui; Zhou, Chi; Lin, Dong

    2016-04-01

    3D printing of a graphene aerogel with true 3D overhang structures is highlighted. The aerogel is fabricated by combining drop-on-demand 3D printing and freeze casting. The water-based GO ink is ejected and freeze-cast into designed 3D structures. The lightweight (<10 mg cm(-3) ) 3D printed graphene aerogel presents superelastic and high electrical conduction. PMID:26861680

  6. Adsorption of herbicides using activated carbons

    SciTech Connect

    Derbyshire, F.; Jagtoyen, M.; Lafferty, C.; Kimber, G.

    1996-12-31

    This paper describes the results of research in which novel activated carbons have been examined for their efficacy in water treatment and, specifically, for the adsorption of a common herbicide and wood preservative, sodium pentachlorophenolate. To place this work in context, the introduction will discuss first some of the considerations of using activated carbons for water treatment, and then certain aspects of the authors research that has led to this particular topic.

  7. A new synthetic route to organic aerogels

    SciTech Connect

    Pekala, R.W.; Alviso, C.T.

    1990-04-11

    The aqueous, sol-gel polymerization of melamine with formaldehyde, followed by supercritical extraction, leads to the formation of a new type of organic aerogel. Synthetic conditions (e.g. reaction time, pH) affect the density, transparency, and microstructure of the resultant aerogels. Unlike previous organic aerogels based upon resorcinol-formaldehyde, the melamine-formaldehyde aerogels are both colorless and transparent. Low densities (0.1-0.8 g/cc), high surface areas ({approximately}1000 m{sup 2}/g), and optical clarity are only a few of the promising characteristics of this new material. 12 refs., 3 figs.

  8. How We 3D-Print Aerogel

    SciTech Connect

    2015-04-23

    A new type of graphene aerogel will make for better energy storage, sensors, nanoelectronics, catalysis and separations. Lawrence Livermore National Laboratory researchers have made graphene aerogel microlattices with an engineered architecture via a 3D printing technique known as direct ink writing. The research appears in the April 22 edition of the journal, Nature Communications. The 3D printed graphene aerogels have high surface area, excellent electrical conductivity, are lightweight, have mechanical stiffness and exhibit supercompressibility (up to 90 percent compressive strain). In addition, the 3D printed graphene aerogel microlattices show an order of magnitude improvement over bulk graphene materials and much better mass transport.

  9. Basic science of new aerogels. Final report

    SciTech Connect

    1996-08-01

    Feasibility of making monolithic composite aerogels containing silica and natural clay minerals, synthetic clay minerals or zeolites has been demonstrated, using two different processes; up to 30 wt% of the mineral phase has been successfully added. Addition of natural and synthetic clay minerals or zeolites to silica aerosols was shown to retard densification. Composite silica aerogels showed significant surface area still present after sintering at 800 or 1000 C. For most samples, 1 wt% of the second phase is equally effective in retarding densification as 10 wt%. Composite aerogels, in general, had lower hardness values than pure silica. Hardness values were inversely proportional to aerogel pore radius.

  10. Aerogel commercialization pilot project. Final program report

    SciTech Connect

    1996-02-13

    Aerogels are extremely light weight, high surface area, very insulative materials that offer many potential improvements to commercial products. Aerogels have been the subject of extensive research at Department of Energy Laboratories and have been considered one of the technology most ready for commercialization. However, commercialization of the technology had been difficult for the National Laboratories since end users were not interested in the high temperature and high pressure chemical processes involved in manufacturing the raw material. Whereas, Aerojet as a supplier of rocket fuels, specialty chemicals and materials had the manufacturing facilities and experience to commercially produce aerogel-type products. Hence the TRP provided a link between the technology source (National Laboratories), the manufacturing (Aerojet) and the potential end users (other TRP partners). The program successfully produced approximately 500 ft{sup 2} of organic aerogel but failed to make significant quantities of silica aerogel. It is significant that this production represents both the largest volume and biggest pieces of organic aerogel ever produced. Aerogels, available from this program, when tested in several prototype commercial products were expected to improve the products performance, but higher than expected projected production costs for large scale manufacture of aerogels has limited continued commercial interest from these partners. Aerogels do, however, offer potential as a specialty material for some high value technology and defense products.

  11. Aerogel: Tile Composites Toughen a Brittle Superinsulation

    NASA Technical Reports Server (NTRS)

    White, Susan; Rasky, Daniel; Arnold, James O. (Technical Monitor)

    1998-01-01

    Pure aerogels, though familiar in the laboratory for decades as exotic lightweight insulators with unusual physical properties, have had limited industrial applications due to their low strength and high brittleness. Composites formed of aerogels and the ceramic fiber matrices used as space shuttle tiles bypass the fragility of pure aerogels and can enhance the performance of space shuttle tiles in their harsh operating environment. Using a layer of aerogel embedded in a tile may open up a wide range of applications where thermal insulation, gas convection control and mechanical strength matter.

  12. Aerogel: Tile Composites Toughen a Brittle Superinsulation

    NASA Technical Reports Server (NTRS)

    White, Susan; Rasky, Daniel; Arnold, James O. (Technical Monitor)

    1998-01-01

    Pure aerogels, though familiar in the laboratory for decades as exotic lightweight insulators with unusual physical properties, have had limited industrial applications due to their low strength and high brittleness. Composites formed of aerogels and the ceramic fiber matrices like those used as space shuttle tiles bypass the fragility of pure aerogels and can enhance the performance of space shuttle tiles in their harsh operating environment. Using a layer of aerogel embedded in a tile may open up a wide range of applications where thermal insulation, gas convection control and mechanical strength matter.

  13. Silica-titania composite aerogel photocatalysts by chemical liquid deposition of titania onto nanoporous silica scaffolds.

    PubMed

    Zu, Guoqing; Shen, Jun; Wang, Wenqin; Zou, Liping; Lian, Ya; Zhang, Zhihua

    2015-03-11

    Silica-titania composite aerogels were synthesized by chemical liquid deposition of titania onto nanoporous silica scaffolds. This novel deposition process was based on chemisorption of partially hydrolyzed titanium alkoxides from solution onto silica nanoparticle surfaces and subsequent hydrolysis and condensation to afford titania nanoparticles on the silica surface. The titania is homogeneously distributed in the silica-titania composite aerogels, and the titania content can be effectively controlled by regulating the deposition cycles. The resultant composite aerogel with 15 deposition cycles possessed a high specific surface area (SSA) of 425 m(2)/g, a small particle size of 5-14 nm, and a large pore volume and pore size of 2.41 cm(3)/g and 18.1 nm, respectively, after heat treatment at 600 °C and showed high photocatalytic activity in the photodegradation of methylene blue under UV-light irradiation. Its photocatalytic activity highly depends on the deposition cycles and heat treatment. The combination of small particle size, high SSA, and enhanced crystallinity after heat treatment at 600 °C contributes to the excellent photocatalytic property of the silica-titania composite aerogel. The higher SSAs compared to those of the reported titania aerogels (<200 m(2)/g at 600 °C) at high temperatures combined with the simple method makes the silica-titania aerogels promising candidates as photocatalysts.

  14. Organic solvent regeneration of granular activated carbon

    NASA Astrophysics Data System (ADS)

    Cross, W. H.; Suidan, M. T.; Roller, M. A.; Kim, B. R.; Gould, J. P.

    1982-09-01

    The use of activated carbon for the treatment of industrial waste-streams was shown to be an effective treatment. The high costs associated with the replacement or thermal regeneration of the carbon have prohibited the economic feasibility of this process. The in situ solvent regeneration of activated carbon by means of organic solvent extraction was suggested as an economically alternative to thermal regeneration. The important aspects of the solvent regeneration process include: the physical and chemical characteristics of the adsorbent, the pore size distribution and energy of adsorption associated with the activated carbon; the degree of solubility of the adsorbate in the organic solvent; the miscibility of the organic solvent in water; and the temperature at which the generation is performed.

  15. Adsorption of methyl mercaptan on activated carbons.

    PubMed

    Bashkova, Svetlana; Bagreev, Andrey; Bandosz, Teresa J

    2002-06-15

    Activated carbons of different origins were studied as methyl mercaptan adsorbents in wet, dry, and oxidizing conditions. The materials were characterized using adsorption of nitrogen, Boehm titration, and thermal analysis. Investigation was focused on the feasibility of the removal of methyl mercaptan on activated carbons and on the role of surface chemistry and porosity in the adsorption/oxidation processes. The results showed relatively high capacities of carbons for removal of CH3SH. The amount adsorbed depends on the surface features. Methyl mercaptan, in general, is oxidized to disulfides, which, depending on the chemistry of the carbon surface, can be converted to sulfonic acid due to the presence of water and active radicals.

  16. Iron-ceria Aerogels Doped with Palladium as Water-gas Shift Catalysts for the Production of Hydrogen

    SciTech Connect

    Bali, S.; Huggins, F; Ernst, R; Pugmire, R; Huffman, G; Eyring, E

    2010-01-01

    Mixed 4.5% iron oxide-95.5% cerium oxide aerogels doped with 1% and 2% palladium (Pd) by weight have been synthesized, and their activities for the catalysis of water-gas shift (WGS) reaction have been determined. The aerogels were synthesized using propylene oxide as the proton scavenger for the initiation of hydrolysis and polycondensation of a homogeneous alcoholic solution of cerium(III) chloride heptahydrate and iron(III) chloride hexahydrate precursor. Palladium was doped onto some of these materials by gas-phase incorporation (GPI) using ({eta}{sup 3}-allyl)({eta}{sup 5}-cyclopentadienyl)palladium as the volatile Pd precursor. Water-gas shift catalytic activities were evaluated in a six-channel fixed-bed reactor at atmospheric pressure and reaction temperatures ranging from 150 to 350 C. Both 1% and 2% Pd-doped 4.5% iron oxide-95.5% cerium oxide aerogels showed WGS activities that increased significantly from 150 to 350 C. The activities of 1% Pd-doped 4.5% iron oxide-95.5% cerium oxide aerogels were also compared with that of the 1% Pd-doped ceria aerogel without iron. The WGS activity of 1% Pd on 4.5% iron oxide-95.5% cerium oxide aerogels is substantially higher (5 times) than the activity of 1% Pd-doped ceria aerogel without iron. The gas-phase incorporation results in a better Pd dispersion. Ceria aerogel provides a nonrigid structure wherein iron is not significantly incorporated inside the matrix, thereby resulting in better contact between the Fe and Pd and thus enhancing the WGS activity. Further, neither Fe nor Pd is reduced during the ceria-aerogel-catalyzed WGS reaction. This behavior contrasts with that noted for other Fe-based WGS catalysts, in which the original ferric oxide is typically reduced to a nonstoichiometric magnetite form.

  17. Use of Nanofibers to Strengthen Hydrogels of Silica, Other Oxides, and Aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Capadona, Lynn A.; Hurwitz, Frances; Vivod, Stephanie L.; Lake, Max

    2010-01-01

    Research has shown that including up to 5 percent w/w carbon nanofibers in a silica backbone of polymer crosslinked aerogels improves its strength, tripling compressive modulus and increasing tensile stress-at-break five-fold with no increase in density or decrease in porosity. In addition, the initial silica hydrogels, which are produced as a first step in manufacturing the aerogels, can be quite fragile and difficult to handle before cross-linking. The addition of the carbon nanofiber also improves the strength of the initial hydrogels before cross-linking, improving the manufacturing process. This can also be extended to other oxide aerogels, such as alumina or aluminosilicates, and other nanofiber types, such as silicon carbide.

  18. Antimicrobial Activity of Carbon-Based Nanoparticles

    PubMed Central

    Maleki Dizaj, Solmaz; Mennati, Afsaneh; Jafari, Samira; Khezri, Khadejeh; Adibkia, Khosro

    2015-01-01

    Due to the vast and inappropriate use of the antibiotics, microorganisms have begun to develop resistance to the commonly used antimicrobial agents. So therefore, development of the new and effective antimicrobial agents seems to be necessary. According to some recent reports, carbon-based nanomaterials such as fullerenes, carbon nanotubes (CNTs) (especially single-walled carbon nanotubes (SWCNTs)) and graphene oxide (GO) nanoparticles show potent antimicrobial properties. In present review, we have briefly summarized the antimicrobial activity of carbon-based nanoparticles together with their mechanism of action. Reviewed literature show that the size of carbon nanoparticles plays an important role in the inactivation of the microorganisms. As major mechanism, direct contact of microorganisms with carbon nanostructures seriously affects their cellular membrane integrity, metabolic processes and morphology. The antimicrobial activity of carbon-based nanostructures may interestingly be investigated in the near future owing to their high surface/volume ratio, large inner volume and other unique chemical and physical properties. In addition, application of functionalized carbon nanomaterials as carriers for the ordinary antibiotics possibly will decrease the associated resistance, enhance their bioavailability and provide their targeted delivery. PMID:25789215

  19. Microwave-assisted regeneration of activated carbon.

    PubMed

    Foo, K Y; Hameed, B H

    2012-09-01

    Microwave heating was used in the regeneration of methylene blue-loaded activated carbons produced from fibers (PFAC), empty fruit bunches (EFBAC) and shell (PSAC) of oil palm. The dye-loaded carbons were treated in a modified conventional microwave oven operated at 2450 MHz and irradiation time of 2, 3 and 5 min. The virgin properties of the origin and regenerated activated carbons were characterized by pore structural analysis and nitrogen adsorption isotherm. The surface chemistry was examined by zeta potential measurement and determination of surface acidity/basicity, while the adsorptive property was quantified using methylene blue (MB). Microwave irradiation preserved the pore structure, original active sites and adsorption capacity of the regenerated activated carbons. The carbon yield and the monolayer adsorption capacities for MB were maintained at 68.35-82.84% and 154.65-195.22 mg/g, even after five adsorption-regeneration cycles. The findings revealed the potential of microwave heating for regeneration of spent activated carbons.

  20. Activated coconut shell charcoal carbon using chemical-physical activation

    NASA Astrophysics Data System (ADS)

    Budi, Esmar; Umiatin, Nasbey, Hadi; Bintoro, Ridho Akbar; Wulandari, Futri; Erlina

    2016-02-01

    The use of activated carbon from natural material such as coconut shell charcoal as metal absorbance of the wastewater is a new trend. The activation of coconut shell charcoal carbon by using chemical-physical activation has been investigated. Coconut shell was pyrolized in kiln at temperature about 75 - 150 °C for about 6 hours in producing charcoal. The charcoal as the sample was shieved into milimeter sized granule particle and chemically activated by immersing in various concentration of HCl, H3PO4, KOH and NaOH solutions. The samples then was physically activated using horizontal furnace at 400°C for 1 hours in argon gas environment with flow rate of 200 kg/m3. The surface morphology and carbon content of activated carbon were characterized by using SEM/EDS. The result shows that the pores of activated carbon are openned wider as the chemical activator concentration is increased due to an excessive chemical attack. However, the pores tend to be closed as further increasing in chemical activator concentration due to carbon collapsing.

  1. Room-temperature embedment of anatase titania nanoparticles into porous cellulose aerogels

    NASA Astrophysics Data System (ADS)

    Jiao, Yue; Wan, Caichao; Li, Jian

    2015-07-01

    In this paper, a facile easy method for room-temperature embedment of anatase titania (TiO2) nanoparticles into porous cellulose aerogels was reported. The obtained anatase TiO2/cellulose (ATC) aerogels were characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nitrogen adsorption measurements, and thermogravimetric analysis. The results showed that high-purity anatase TiO2 nanoparticles with sizes of 3.69 ± 0.77 nm were evenly dispersed in the cellulose aerogels, which leaded to the significant improvement in specific surface area and pore volume of ATC aerogels. Meanwhile, the hybrid ATC aerogels also had a high loading content of TiO2 (ca. 17.7 %). Furthermore, through a simple photocatalytic degradation test of indigo carmine dye under UV light, ATC aerogels exhibited superior photocatalytic activity and shape stability, which might be useful in some fields like governance of water pollution, and chemical leaks.

  2. Thermal properties of organic and modified inorganic aerogels

    SciTech Connect

    Pekala, R.W.; Hrubesh, L.W.

    1992-08-01

    Aerogels are open-cell foams that have already been shown to be among the best thermal insulating solid materials known. Improvements in the thermal insulating properties of aerogels are possible by synthesizing new organic varieties, by using additives within existing aerogel matrix, and by optimizing their nanostructures. We discuss these approaches and give some examples of aerogels which demonstrate the improvements.

  3. Ultralow percolation threshold in aerogel and cryogel templated composites.

    PubMed

    Irin, Fahmida; Das, Sriya; Atore, Francis O; Green, Micah J

    2013-09-10

    We demonstrate a novel concept for preparing percolating composites with ultralow filler content by utilizing nanofiller-loaded aerogel and cryogels as a conductive template. This concept is investigated for several porous systems, including resorcinol-formaldehyde (RF), silica, and polyacrylamide (PAM) gels, and both graphene and carbon nanotubes are utilized as nanofiller. In each case, a stable, aqueous nanofiller dispersion is mixed with a sol-gel precursor and polymerized to form a hydrogel, which can then be converted to an aerogel by critical point drying or cryogel by freeze-drying. Epoxy resin is infused into the pores of the gels by capillary action without disrupting the monolithic structure. We show that conductive graphene/epoxy composites are formed with a very low graphene loading; a percolation threshold as low as 0.012 vol % is obtained for graphene-RF cryogel/epoxy composite. This is the lowest reported threshold of any graphene-based nanocomposites. Similar values are achieved in other aerogel and nanofiller systems, which demonstrates the versatility of this method. PMID:23927050

  4. Chemical Analyses of Silicon Aerogel Samples

    SciTech Connect

    van der Werf, I.; Palmisano, F.; De Leo, Raffaele; Marrone, Stefano

    2008-04-01

    After five years of operating, two Aerogel counters: A1 and A2, taking data in Hall A at Jefferson Lab, suffered a loss of performance. In this note possible causes of degradation have been studied. In particular, various chemical and physical analyses have been carried out on several Aerogel tiles and on adhesive tape in order to reveal the presence of contaminants.

  5. Nonflammable, Hydrophobic Aerogel Composites for Insulation

    NASA Technical Reports Server (NTRS)

    Redouane, Begag

    2005-01-01

    Aerogel composites that are both nonflammable and hydrophobic have been developed for use as lightweight thermal- insulation materials for cryogenic systems. Aerogels are well known in the industry for their effectiveness as thermal insulators under cryogenic conditions, but the treatments used heretofore to render them hydrophobic also make them flammable. Nonflammability would make it safer to use aerogel insulation, especially in oxygen-rich environments and on cryogenic systems that contain liquid oxygen. A composite of this type is a silica aerogel reinforced with fibers. In comparison with unreinforced aerogels, the aerogel composite is about ten times as stiff and strong, better able to withstand handling, and more amenable to machining to required shapes. The composite can be made hydrophobic and nonflammable by appropriate design of a sol-gel process used to synthesize the aerogel component. In addition to very low thermal conductivity needed for insulation, aerogel composites of this type have been found to exhibit high resistance to moisture and nonflammability in oxygen-rich atmospheres: Samples floating on water for months gained no weight and showed no signs of deterioration. Samples were found to be nonflammable, even in pure oxygen at atmospheric pressure [14.7 psia (0.10 MPa)

  6. A novel activated carbon for supercapacitors

    SciTech Connect

    Shen, Haijie; Liu, Enhui; Xiang, Xiaoxia; Huang, Zhengzheng; Tian, Yingying; Wu, Yuhu; Wu, Zhilian; Xie, Hui

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer A novel activated carbon was prepared from phenol-melamine-formaldehyde resin. Black-Right-Pointing-Pointer The carbon has large surface area with microporous, and high heteroatom content. Black-Right-Pointing-Pointer Heteroatom-containing functional groups can improve the pseudo-capacitance. Black-Right-Pointing-Pointer Physical and chemical properties lead to the good electrochemical properties. -- Abstract: A novel activated carbon has been prepared by simple carbonization and activation of phenol-melamine-formaldehyde resin which is synthesized by the condensation polymerization method. The morphology, thermal stability, surface area, elemental composition and surface chemical composition of samples have been investigated by scanning electron microscope, thermogravimetry and differential thermal analysis, Brunauer-Emmett-Teller measurement, elemental analysis and X-ray photoelectron spectroscopy, respectively. Electrochemical properties have been studied by cyclic voltammograms, galvanostatic charge/discharge, and electrochemical impedance spectroscopy measurements in 6 mol L{sup -1} potassium hydroxide. The activated carbon shows good capacitive behavior and the specific capacitance is up to 210 F g{sup -1}, which indicates that it may be a promising candidate for supercapacitors.

  7. Thermal properties of methyltrimethoxysilane aerogel thin films

    NASA Astrophysics Data System (ADS)

    Acquaroli, Leandro N.; Newby, Pascal; Santato, Clara; Peter, Yves-Alain

    2016-10-01

    Aerogels are light and porous solids whose properties, largely determined by their nanostructure, are useful in a wide range of applications, e.g., thermal insulation. In this work, as-deposited and thermally treated air-filled silica aerogel thin films synthesized using the sol-gel method were studied for their thermal properties using the 3-omega technique, at ambient conditions. The thermal conductivity and diffusivity were found to increase as the porosity of the aerogel decreased. Thermally treated films show a clear reduction in thermal conductivity compared with that of as-deposited films, likely due to an increase of porosity. The smallest thermal conductivity and diffusivity found for our aerogels were 0.019 W m-1 K-1 and 9.8 × 10-9 m2 s-1. A model was used to identify the components (solid, gaseous and radiative) of the total thermal conductivity of the aerogel.

  8. Solid phase microextraction device using aerogel

    DOEpatents

    Miller, Fred S.; Andresen, Brian D.

    2005-06-14

    A sample collection substrate of aerogel and/or xerogel materials bound to a support structure is used as a solid phase microextraction (SPME) device. The xerogels and aerogels may be organic or inorganic and doped with metals or other compounds to target specific chemical analytes. The support structure is typically formed of a glass fiber or a metal wire (stainless steel or kovar). The devices are made by applying gel solution to the support structures and drying the solution to form aerogel or xerogel. Aerogel particles may be attached to the wet layer before drying to increase sample collection surface area. These devices are robust, stable in fields of high radiation, and highly effective at collecting gas and liquid samples while maintaining superior mechanical and thermal stability during routine use. Aerogel SPME devices are advantageous for use in GC/MS analyses due to their lack of interfering background and tolerance of GC thermal cycling.

  9. Superfluid 3He in ``nematically ordered'' aerogel

    NASA Astrophysics Data System (ADS)

    Dmitriev, Vladimir

    2014-03-01

    Liquid 3He immersed in aerogel allows investigation of the influence of impurities on unconventional superfluidity. In most of such experiments silica aerogels are used. These aerogels consist of thin strands which form a ``wisp.'' Although it is established that superfluid phases of 3He in silica aerogels (A-like and B-like) have the same order parameters as A and B phases of bulk 3He, many new phenomena were observed. In particular, it was found that global anisotropy of aerogel (e.g. caused by squeezing or stretching) can orient the order parameter. Depending on prehistory and on the type of the anisotropy the A-like phase may be homogeneous or in a state with random orbital part of the order parameter. Theory predicts that a large stretching anisotropy may even influence the order parameter structure: polar phase (or A phase with polar distortion), which are not realized in bulk 3He, may become more favorable than pure A phase. Large stretching anisotropy is hardly achievable in silica aerogel. Therefore in experiments described in the talk we used a new type of aerogel, consisting of Al2O3 . H2O strands which are parallel to each other, i.e. this aerogel may be considered as infinitely stretched. We found that the superfluid phase diagram of 3He in such ``nematically ordered'' aerogel is different from the case of 3He in silica aerogel and that both observed A and B phases have large polar distortion. This distortion is larger at low pressures and grows on warming. There are indications that a pure polar phase appears near the superfluid transition temperature. Recent results will be also presented.

  10. Physics of Interplanetary Dust Collection with Aerogel

    NASA Technical Reports Server (NTRS)

    Anderson, William W.

    1998-01-01

    This report presents the results of research undertaken to study various problems associated with hypervelocity capture of dust particles in aerogel. The primary topics investigated were the properties of shocked aerogel and the requirements for reliable capture of particles on the STARDUST mission. In particular, the viscosity of shocked aerogel has been an open question. The results presented here suggest that the viscosity of aerogel at high impact velocities is negligible, although there remains some uncertainty about lower velocities. The model adopted for viscosity treats the mixture of polymeric silica and decomposition products and finds that, for particle velocities of 6-7 km/s, the viscosity is similar to that typical of light gasses at STP. Expressions for the Hugoniot of aerogel as a function of density were also obtained from the available data. All aerogels of interest for cosmic dust collectors have very similar shock velocity-particle velocity Hugoniot curves. The strength behavior of aerogel for low-speed penetration was measured, but further work is needed to study the proper way to apply this to the issue of terminal deceleration of a dust particle. Preliminary calculations designed to maximize the penetration depths were performed to determine the required density of aerogel to reliably stop a particle in a 3 cm thickness of aerogel (the path length expected for a normal impact into the STARDUST collector). In order to stop a particle of density rho(sub p) and diameter d(sub p), the mean density of the aerogel collector should be no less than that given by the expression bar rho(sub 0) = 1.085 X 10(exp -4 )rho(sub p)d(sub p), for densities measured in g/ cu cm and the particle diameter measured in micrometers.

  11. Activated carbon monoliths for methane storage

    NASA Astrophysics Data System (ADS)

    Chada, Nagaraju; Romanos, Jimmy; Hilton, Ramsey; Suppes, Galen; Burress, Jacob; Pfeifer, Peter

    2012-02-01

    The use of adsorbent storage media for natural gas (methane) vehicles allows for the use of non-cylindrical tanks due to the decreased pressure at which the natural gas is stored. The use of carbon powder as a storage material allows for a high mass of methane stored for mass of sample, but at the cost of the tank volume. Densified carbon monoliths, however, allow for the mass of methane for volume of tank to be optimized. In this work, different activated carbon monoliths have been produced using a polymeric binder, with various synthesis parameters. The methane storage was studied using a home-built, dosing-type instrument. A monolith with optimal parameters has been fabricated. The gravimetric excess adsorption for the optimized monolith was found to be 161 g methane for kg carbon.

  12. Cotton-derived bulk and fiber aerogels grafted with nitrogen-doped graphene

    NASA Astrophysics Data System (ADS)

    Wang, Chunhui; Li, Yibin; He, Xiaodong; Ding, Yujie; Peng, Qingyu; Zhao, Wenqi; Shi, Enzheng; Wu, Shiting; Cao, Anyuan

    2015-04-01

    Three-dimensional graphene-based structures such as graphene aerogels or foams have shown applications in energy, environmental matters, and many other areas. Here, we present a method to convert raw cotton into functional aerogels containing a significant amount of nitrogen-doped graphene (N-graphene) sheets grafted on carbonized cellulose fibers. Urea was introduced into raw cotton as a molecular template as well as a nitrogen source to synthesize mushroom-like N-graphene sheets strongly attached to cotton skeletons. The excellent processability of raw cotton allows us to configure bulk or meter-long fiber shaped aerogels, with high porosity and flexibility. Synergistic effects stemming from the integration of N-graphene and carbonized cotton skeletons promise potential applications as conductive electrodes for supercapacitors, with a measured specific capacitance of 107.5 F g-1 in a two-electrode system. Our results indicate a low-cost and scalable approach toward high-performance graphene-based aerogels and electrodes via biomass templating.Three-dimensional graphene-based structures such as graphene aerogels or foams have shown applications in energy, environmental matters, and many other areas. Here, we present a method to convert raw cotton into functional aerogels containing a significant amount of nitrogen-doped graphene (N-graphene) sheets grafted on carbonized cellulose fibers. Urea was introduced into raw cotton as a molecular template as well as a nitrogen source to synthesize mushroom-like N-graphene sheets strongly attached to cotton skeletons. The excellent processability of raw cotton allows us to configure bulk or meter-long fiber shaped aerogels, with high porosity and flexibility. Synergistic effects stemming from the integration of N-graphene and carbonized cotton skeletons promise potential applications as conductive electrodes for supercapacitors, with a measured specific capacitance of 107.5 F g-1 in a two-electrode system. Our results

  13. High surface area, electrically conductive nanocarbon-supported metal oxide

    DOEpatents

    Worsley, Marcus A; Han, Thomas Yong-Jin; Kuntz, Joshua D; Cervanted, Octavio; Gash, Alexander E; Baumann, Theodore F; Satcher, Jr., Joe H

    2014-03-04

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust.

  14. High surface area, electrically conductive nanocarbon-supported metal oxide

    SciTech Connect

    Worsley, Marcus A.; Han, Thomas Yong-Jin; Kuntz, Joshua D.; Cervantes, Octavio; Gash, Alexander E.; Baumann, Theodore F.; Satcher, Jr., Joe H.

    2015-07-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust.

  15. A facile route for 3D aerogels from nanostructured 1D and 2D materials

    PubMed Central

    Jung, Sung Mi; Jung, Hyun Young; Dresselhaus, Mildred S.; Jung, Yung Joon; Kong, Jing

    2012-01-01

    Aerogels have numerous applications due to their high surface area and low densities. However, creating aerogels from a large variety of materials has remained an outstanding challenge. Here, we report a new methodology to enable aerogel production with a wide range of materials. The method is based on the assembly of anisotropic nano-objects (one-dimensional (1D) nanotubes, nanowires, or two-dimensional (2D) nanosheets) into a cross-linking network from their colloidal suspensions at the transition from the semi-dilute to the isotropic concentrated regime. The resultant aerogels have highly porous and ultrafine three-dimensional (3D) networks consisting of 1D (Ag, Si, MnO2, single-walled carbon nanotubes (SWNTs)) and 2D materials (MoS2, graphene, h-BN) with high surface areas, low densities, and high electrical conductivities. This method opens up a facile route for aerogel production with a wide variety of materials and tremendous opportunities for bio-scaffold, energy storage, thermoelectric, catalysis, and hydrogen storage applications. PMID:23152940

  16. A facile route for 3D aerogels from nanostructured 1D and 2D materials.

    PubMed

    Jung, Sung Mi; Jung, Hyun Young; Dresselhaus, Mildred S; Jung, Yung Joon; Kong, Jing

    2012-01-01

    Aerogels have numerous applications due to their high surface area and low densities. However, creating aerogels from a large variety of materials has remained an outstanding challenge. Here, we report a new methodology to enable aerogel production with a wide range of materials. The method is based on the assembly of anisotropic nano-objects (one-dimensional (1D) nanotubes, nanowires, or two-dimensional (2D) nanosheets) into a cross-linking network from their colloidal suspensions at the transition from the semi-dilute to the isotropic concentrated regime. The resultant aerogels have highly porous and ultrafine three-dimensional (3D) networks consisting of 1D (Ag, Si, MnO(2), single-walled carbon nanotubes (SWNTs)) and 2D materials (MoS(2), graphene, h-BN) with high surface areas, low densities, and high electrical conductivities. This method opens up a facile route for aerogel production with a wide variety of materials and tremendous opportunities for bio-scaffold, energy storage, thermoelectric, catalysis, and hydrogen storage applications.

  17. Development of aerogel-lined targets for inertial confinement fusion experiments

    SciTech Connect

    Braun, Tom

    2013-03-28

    This thesis explores the formation of ICF compatible foam layers inside of an ablator shell used for inertial confinement fusion experiments at the National Ignition Facility. In particular, the capability of p- DCPD polymer aerogels to serve as a scaffold for the deuterium-tritium mix was analyzed. Four different factors were evaluated: the dependency of different factors such as thickness or composition of a precursor solution on the uniformity of the aerogel layer, how to bring the optimal composition inside of the ablator shell, the mechanical stability of ultra-low density p-DCPD aerogel bulk pieces during wetting and freezing with hydrogen, and the wetting behavior of thin polymer foam layers in HDC carbon ablator shells with liquid deuterium. The research for thesis was done at Lawrence Livermore National Laboratory in cooperation with the Technical University Munich.

  18. Preparation of activated carbons with mesopores by use of organometallics

    SciTech Connect

    Yamada, Yoshio; Yoshizawa, Noriko; Furuta, Takeshi

    1996-12-31

    Activated carbons are commercially produced by steam or CO{sub 2} activation of coal, coconut shell and so on. In general the carbons obtained give pores with a broad range of distribution. The objective of this study was to prepare activated carbons from coal by use of various organometallic compounds. The carbons were evaluated for pore size by nitrogen adsorption experiments.

  19. USING POWDERED ACTIVATED CARBON: A CRITICAL REVIEW

    EPA Science Inventory

    Because the performance of powdered activated carbon (PAC) for uses other than taste and odor control is poorly documented, the purpose of this article is to critically review uses that have been reported (i.e., pesticides and herbicides, synthetic organic chemicals, and trihalom...

  20. MODELING MERCURY CONTROL WITH POWDERED ACTIVATED CARBON

    EPA Science Inventory

    The paper presents a mathematical model of total mercury removed from the flue gas at coal-fired plants equipped with powdered activated carbon (PAC) injection for Mercury control. The developed algorithms account for mercury removal by both existing equipment and an added PAC in...

  1. Aerogel Blanket Insulation Materials for Cryogenic Applications

    NASA Technical Reports Server (NTRS)

    Coffman, B. E.; Fesmire, J. E.; White, S.; Gould, G.; Augustynowicz, S.

    2009-01-01

    Aerogel blanket materials for use in thermal insulation systems are now commercially available and implemented by industry. Prototype aerogel blanket materials were presented at the Cryogenic Engineering Conference in 1997 and by 2004 had progressed to full commercial production by Aspen Aerogels. Today, this new technology material is providing superior energy efficiencies and enabling new design approaches for more cost effective cryogenic systems. Aerogel processing technology and methods are continuing to improve, offering a tailor-able array of product formulations for many different thermal and environmental requirements. Many different varieties and combinations of aerogel blankets have been characterized using insulation test cryostats at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Detailed thermal conductivity data for a select group of materials are presented for engineering use. Heat transfer evaluations for the entire vacuum pressure range, including ambient conditions, are given. Examples of current cryogenic applications of aerogel blanket insulation are also given. KEYWORDS: Cryogenic tanks, thermal insulation, composite materials, aerogel, thermal conductivity, liquid nitrogen boil-off

  2. Method for nanoencapsulation of aerogels and nanoencapsulated aerogels produced by such method

    NASA Technical Reports Server (NTRS)

    Sullivan, Thomas A. (Inventor)

    2007-01-01

    A method for increasing the compressive modulus of aerogels comprising: providing aerogel substrate comprising a bubble matrix in a chamber; providing monomer to the chamber, the monomer comprising vapor phase monomer which polymerizes substantially free of polymerization byproducts; depositing monomer from the vapor phase onto the surface of the aerogel substrate under deposition conditions effective to produce a vapor pressure sufficient to cause the vapor phase monomer to penetrate into the bubble matrix and deposit onto the surface of the aerogel substrate, producing a substantially uniform monomer film; and, polymerizing the substantially uniform monomer film under polymerization conditions effective to produce polymer coated aerogel comprising a substantially uniform polymer coating substantially free of polymerization byproducts.Polymer coated aerogel comprising aerogel substrate comprising a substantially uniform polymer coating, said polymer coated aerogel comprising porosity and having a compressive modulus greater than the compressive modulus of the aerogel substrate, as measured by a 100 lb. load cell at 1 mm/minute in the linear range of 20% to 40% compression.

  3. Supercapacitor Electrodes from Activated Carbon Monoliths and Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Dolah, B. N. M.; Othman, M. A. R.; Deraman, M.; Basri, N. H.; Farma, R.; Talib, I. A.; Ishak, M. M.

    2013-04-01

    Binderless monoliths of supercapacitor electrodes were prepared by the carbonization (N2) and activation (CO2) of green monoliths (GMs). GMs were made from mixtures of self-adhesive carbon grains (SACG) of fibers from oil palm empty fruit bunches and a combination of 5 & 6% KOH and 0, 5 & 6% carbon nanotubes (CNTs) by weight. The electrodes from GMs containing CNTs were found to have lower specific BET surface area (SBET). The electrochemical behavior of the supercapacitor fabricated using the prepared electrodes were investigated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge (GCD). In general an addition of CNTs into the GMs reduces the equivalent series resistance (ESR) value of the cells. A cell fabricated using electrodes from GM with 5% CNT and 5% KOH was found to have the largest reduction of ESR value than that from the others GMs containing CNT. The cell has steeper Warburg's slope than that from its respective non-CNT GM, which reflect the smaller resistance for electrolyte ions to move into pores of electrodes despite these electrodes having largest reduction in specific BET surface area. The cell also has the smallest reduction of specific capacitance (Csp) and maintains the specific power range despite a reduction in the specific energy range due to the CNT addition.

  4. Composite Silica Aerogels Opacified with Titania

    NASA Technical Reports Server (NTRS)

    Paik, Jon-Ah; Sakamoto, Jeffrey; Jones, Steven; Fleurial, Jean-Pierre; DiStefano, Salvador; Nesmith, Bill

    2009-01-01

    A further improvement has been made to reduce the high-temperature thermal conductivities of the aerogel-matrix composite materials described in Improved Silica Aerogel Composite Materials (NPO-44287), NASA Tech Briefs, Vol. 32, No. 9 (September 2008), page 50. Because the contribution of infrared radiation to heat transfer increases sharply with temperature, the effective high-temperature thermal conductivity of a thermal-insulation material can be reduced by opacifying the material to reduce the radiative contribution. Therefore, the essence of the present improvement is to add an opacifying constituent material (specifically, TiO2 powder) to the aerogel-matrix composites.

  5. Aerogel commercialization: Technology, markets and costs

    SciTech Connect

    Carlson, G.; Lewis, D.; McKinley, K.; Richardson, J.; Tillotson, T.

    1994-10-07

    Commercialization of aerogels has been slow due to several factors including cost and manufacturability issues. The technology itself is well enough developed as a result of work over the past decade by an international-community of researchers. Several extensive substantial markets appear to exist for aerogels as thermal and sound insulators, if production costs can keep prices in line with competing established materials. The authors discuss here the elements which they have identified as key cost drivers, and they give a prognosis for the evolution of the technology leading to reduced cost aerogel production.

  6. Sound velocity of liquid 4He in aerogel

    NASA Astrophysics Data System (ADS)

    Matsumoto, Koichi; Arai, Osamu; Okuda, Yuichi; Tajiri, Koji

    2000-07-01

    The sound velocity and attenuation of liquid 4He in 93.7% and 94.6% porosity aerogels were measured for a frequency of 10 MHz. The sound velocity in 93.7% aerogel was larger than that in bulk 4He, whereas that in 94.6% was smaller. A model of the aerogel- 4He composite gave satisfactory agreement with the dependence of the sound velocity on the temperature and the aerogel density. This shows that the normal fluid is clamped to aerogel strands, although the viscous penetration depth is comparable to the typical size of a void in the aerogel.

  7. Carbon nanomaterials: Biologically active fullerene derivatives.

    PubMed

    Bogdanović, Gordana; Djordjević, Aleksandar

    2016-01-01

    Since their discovery, fullerenes, carbon nanotubes, and graphene attract significant attention of researches in various scientific fields including biomedicine. Nano-scale size and a possibility for diverse surface modifications allow carbon nanoallotropes to become an indispensable nanostructured material in nanotechnologies, including nanomedicine. Manipulation of surface chemistry has created diverse populations of water-soluble derivatives of fullerenes, which exhibit different behaviors. Both non-derivatized and derivatized fullerenes show various biological activities. Cellular processes that underline their toxicity are oxidative, genotoxic, and cytotoxic responses.The antioxidant/cytoprotective properties of fullerenes and derivatives have been considered in the prevention of organ oxidative damage and treatment. The same unique physiochemical properties of nanomaterials may also be associated with potential health hazards. Non-biodegradability and toxicity of carbon nanoparticles still remain a great concern in the area of biomedical application. In this review, we report on basic physical and chemical properties of carbon nano-clusters--fullerenes, nanotubes, and grapheme--their specificities, activities, and potential application in biological systems. Special emphasis is given to our most important results obtained in vitro and in vivo using polyhydroxylated fullerene derivative C₆₀(OH)₂₄.

  8. Carbon nanomaterials: Biologically active fullerene derivatives.

    PubMed

    Bogdanović, Gordana; Djordjević, Aleksandar

    2016-01-01

    Since their discovery, fullerenes, carbon nanotubes, and graphene attract significant attention of researches in various scientific fields including biomedicine. Nano-scale size and a possibility for diverse surface modifications allow carbon nanoallotropes to become an indispensable nanostructured material in nanotechnologies, including nanomedicine. Manipulation of surface chemistry has created diverse populations of water-soluble derivatives of fullerenes, which exhibit different behaviors. Both non-derivatized and derivatized fullerenes show various biological activities. Cellular processes that underline their toxicity are oxidative, genotoxic, and cytotoxic responses.The antioxidant/cytoprotective properties of fullerenes and derivatives have been considered in the prevention of organ oxidative damage and treatment. The same unique physiochemical properties of nanomaterials may also be associated with potential health hazards. Non-biodegradability and toxicity of carbon nanoparticles still remain a great concern in the area of biomedical application. In this review, we report on basic physical and chemical properties of carbon nano-clusters--fullerenes, nanotubes, and grapheme--their specificities, activities, and potential application in biological systems. Special emphasis is given to our most important results obtained in vitro and in vivo using polyhydroxylated fullerene derivative C₆₀(OH)₂₄. PMID:27483572

  9. Enhanced capacitive properties of commercial activated carbon by re-activation in molten carbonates

    NASA Astrophysics Data System (ADS)

    Lu, Beihu; Xiao, Zuoan; Zhu, Hua; Xiao, Wei; Wu, Wenlong; Wang, Dihua

    2015-12-01

    Simple, affordable and green methods to improve capacitive properties of commercial activated carbon (AC) are intriguing since ACs possess a predominant role in the commercial supercapacitor market. Herein, we report a green reactivation of commercial ACs by soaking ACs in molten Na2CO3-K2CO3 (equal in mass ratios) at 850 °C combining the merits of both physical and chemical activation strategies. The mechanism of molten carbonate treatment and structure-capacitive activity correlations of the ACs are rationalized. Characterizations show that the molten carbonate treatment increases the electrical conductivity of AC without compromising its porosity and wettability of electrolytes. Electrochemical tests show the treated AC exhibited higher specific capacitance, enhanced high-rate capability and excellent cycle performance, promising its practical application in supercapacitors. The present study confirms that the molten carbonate reactivation is a green and effective method to enhance capacitive properties of ACs.

  10. Hydrothermal self-assembly and supercapacitive behaviors of Co(II) ion-modified graphene aerogels in H{sub 2}SO{sub 4} electrolyte

    SciTech Connect

    Bao, Qi; Hui, K.N.; Hui, K.S.; Wang, Yi; Hong, Xiaoting

    2014-08-15

    Highlights: • 3D Co(II) ions modified graphene aerogels were prepared by one-step hydrothermal process. • The aerogel electrodes showed hybrid supercapacitor behaviors. • The aerogel electrodes exhibited high rate capability and long-term cycling stability. - Abstract: Reduced graphene oxide (r-GO) aerogels decorated with divalent cobalt ions were synthesized via a one-pot hydrothermal self-assembly route. The interaction of Co(II) ions with 3D r-GO aerogels was investigated by spectroscopic techniques, including Raman, attenuated total reflectance infrared, and X-ray photoelectron spectroscopies. The excellent electrochemical properties of the aerogels were confirmed by cyclic voltammetry, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy in an acid electrolyte (1 M H{sub 2}SO{sub 4}). The Co(II) ion-modified r-GO aerogels can be used as high-performance hybrid supercapacitor materials with a specific capacitance of 387.2 F g{sup –1} at 1 A g{sup –1} current density and a good cycling stability without capacity decay over 1000 cycles. The mechanical integrity enhancement of the hybrid r-GO aerogel framework and the improvement in its unique capacitive performance are attributed to the efficient interconnection produced by electro-active Co(II) ions.

  11. Kinetics of adsorption with granular, powdered, and fibrous activated carbon

    SciTech Connect

    Shmidt, J.L.; Pimenov, A.V.; Lieberman, A.I.; Cheh, H.Y.

    1997-08-01

    The properties of three different types of activated carbon, fibrous, powdered, and granular, were investigated theoretically and experimentally. The adsorption rate of the activated carbon fiber was found to be two orders of magnitude higher than that of the granular activated carbon, and one order of magnitude higher than that of the powdered activated carbon. Diffusion coefficients of methylene blue in the fibrous, powdered, and granular activated carbons were determined experimentally. A new method for estimating the meso- and macropore surface areas in these carbons was proposed.

  12. Tortuosity of 4He Films on Aerogel

    SciTech Connect

    Ashton, C. E.; Golov, A. I.; Mulders, N.

    2006-09-07

    A torsional oscillator has been used to study the flow of liquid 4He through silica aerogel. The tortuosity and dissipation of the flow in the fractal aerogel environment has been measured, for both capillary condensed films and a fully saturated cell. The scaling of tortuosity as a function of filling fraction has been investigated. We compare the results of our 88%-porous aerogel to a 92%-porous sample where a transverse sound technique was used. Our more sensitive technique has reduced the scatter in both the frequency and dissipation data. Like in the previous transverse sound experiment, we find tortuosity as a function of filling fraction to scale with an exponent of {approx} -1.1. Further experiments are planned, to find the dependence of the exponent on the fractal dimension and porosity of aerogel.

  13. Aqueous mercury adsorption by activated carbons.

    PubMed

    Hadi, Pejman; To, Ming-Ho; Hui, Chi-Wai; Lin, Carol Sze Ki; McKay, Gordon

    2015-04-15

    Due to serious public health threats resulting from mercury pollution and its rapid distribution in our food chain through the contamination of water bodies, stringent regulations have been enacted on mercury-laden wastewater discharge. Activated carbons have been widely used in the removal of mercuric ions from aqueous effluents. The surface and textural characteristics of activated carbons are the two decisive factors in their efficiency in mercury removal from wastewater. Herein, the structural properties and binding affinity of mercuric ions from effluents have been presented. Also, specific attention has been directed to the effect of sulfur-containing functional moieties on enhancing the mercury adsorption. It has been demonstrated that surface area, pore size, pore size distribution and surface functional groups should collectively be taken into consideration in designing the optimal mercury removal process. Moreover, the mercury adsorption mechanism has been addressed using equilibrium adsorption isotherm, thermodynamic and kinetic studies. Further recommendations have been proposed with the aim of increasing the mercury removal efficiency using carbon activation processes with lower energy input, while achieving similar or even higher efficiencies.

  14. Supercapacitors Based on Three-Dimensional Hierarchical Graphene Aerogels with Periodic Macropores.

    PubMed

    Zhu, Cheng; Liu, Tianyu; Qian, Fang; Han, T Yong-Jin; Duoss, Eric B; Kuntz, Joshua D; Spadaccini, Christopher M; Worsley, Marcus A; Li, Yat

    2016-06-01

    Graphene is an atomically thin, two-dimensional (2D) carbon material that offers a unique combination of low density, exceptional mechanical properties, thermal stability, large surface area, and excellent electrical conductivity. Recent progress has resulted in macro-assemblies of graphene, such as bulk graphene aerogels for a variety of applications. However, these three-dimensional (3D) graphenes exhibit physicochemical property attenuation compared to their 2D building blocks because of one-fold composition and tortuous, stochastic porous networks. These limitations can be offset by developing a graphene composite material with an engineered porous architecture. Here, we report the fabrication of 3D periodic graphene composite aerogel microlattices for supercapacitor applications, via a 3D printing technique known as direct-ink writing. The key factor in developing these novel aerogels is creating an extrudable graphene oxide-based composite ink and modifying the 3D printing method to accommodate aerogel processing. The 3D-printed graphene composite aerogel (3D-GCA) electrodes are lightweight, highly conductive, and exhibit excellent electrochemical properties. In particular, the supercapacitors using these 3D-GCA electrodes with thicknesses on the order of millimeters display exceptional capacitive retention (ca. 90% from 0.5 to 10 A·g(-1)) and power densities (>4 kW·kg(-1)) that equal or exceed those of reported devices made with electrodes 10-100 times thinner. This work provides an example of how 3D-printed materials, such as graphene aerogels, can significantly expand the design space for fabricating high-performance and fully integrable energy storage devices optimized for a broad range of applications. PMID:26789202

  15. Supercapacitors Based on Three-Dimensional Hierarchical Graphene Aerogels with Periodic Macropores.

    PubMed

    Zhu, Cheng; Liu, Tianyu; Qian, Fang; Han, T Yong-Jin; Duoss, Eric B; Kuntz, Joshua D; Spadaccini, Christopher M; Worsley, Marcus A; Li, Yat

    2016-06-01

    Graphene is an atomically thin, two-dimensional (2D) carbon material that offers a unique combination of low density, exceptional mechanical properties, thermal stability, large surface area, and excellent electrical conductivity. Recent progress has resulted in macro-assemblies of graphene, such as bulk graphene aerogels for a variety of applications. However, these three-dimensional (3D) graphenes exhibit physicochemical property attenuation compared to their 2D building blocks because of one-fold composition and tortuous, stochastic porous networks. These limitations can be offset by developing a graphene composite material with an engineered porous architecture. Here, we report the fabrication of 3D periodic graphene composite aerogel microlattices for supercapacitor applications, via a 3D printing technique known as direct-ink writing. The key factor in developing these novel aerogels is creating an extrudable graphene oxide-based composite ink and modifying the 3D printing method to accommodate aerogel processing. The 3D-printed graphene composite aerogel (3D-GCA) electrodes are lightweight, highly conductive, and exhibit excellent electrochemical properties. In particular, the supercapacitors using these 3D-GCA electrodes with thicknesses on the order of millimeters display exceptional capacitive retention (ca. 90% from 0.5 to 10 A·g(-1)) and power densities (>4 kW·kg(-1)) that equal or exceed those of reported devices made with electrodes 10-100 times thinner. This work provides an example of how 3D-printed materials, such as graphene aerogels, can significantly expand the design space for fabricating high-performance and fully integrable energy storage devices optimized for a broad range of applications.

  16. Method for making monolithic metal oxide aerogels

    DOEpatents

    Droege, M.W.; Coronado, P.R.; Hair, L.M.

    1995-03-07

    Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The present invention is especially advantageous for making metal oxides other than silica that are prone to forming opaque, cracked aerogels. 6 figs.

  17. Process for preparing polymer reinforced silica aerogels

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Capadona, Lynn A. (Inventor)

    2011-01-01

    Process for preparing polymer-reinforced silica aerogels which comprises a one-pot reaction of at least one alkoxy silane in the presence of effective amounts of a polymer precursor to obtain a silica reaction product, the reaction product is gelled and subsequently subjected to conditions that promotes polymerization of the precursor and then supercritically dried to obtain the polymer-reinforced monolithic silica aerogels.

  18. Method for making monolithic metal oxide aerogels

    DOEpatents

    Droege, Michael W.; Coronado, Paul R.; Hair, Lucy M.

    1995-01-01

    Transparent, monolithic metal oxide aerogels of varying densities are produced using a method in which a metal alkoxide solution and a catalyst solution are prepared separately and reacted. The resulting hydrolyzed-condensed colloidal solution is gelled, and the wet gel is contained within a sealed, but gas permeable, containment vessel during supercritical extraction of the solvent. The present invention is especially advantageous for making metal oxides other than silica that are prone to forming opaque, cracked aerogels.

  19. Fibrous-Ceramic/Aerogel Composite Insulating Tiles

    NASA Technical Reports Server (NTRS)

    White, Susan M.; Rasky, Daniel J.

    2004-01-01

    Fibrous-ceramic/aerogel composite tiles have been invented to afford combinations of thermal-insulation and mechanical properties superior to those attainable by making tiles of fibrous ceramics alone or aerogels alone. These lightweight tiles can be tailored to a variety of applications that range from insulating cryogenic tanks to protecting spacecraft against re-entry heating. The advantages and disadvantages of fibrous ceramics and aerogels can be summarized as follows: Tiles made of ceramic fibers are known for mechanical strength, toughness, and machinability. Fibrous ceramic tiles are highly effective as thermal insulators in a vacuum. However, undesirably, the porosity of these materials makes them permeable by gases, so that in the presence of air or other gases, convection and gas-phase conduction contribute to the effective thermal conductivity of the tiles. Other disadvantages of the porosity and permeability of fibrous ceramic tiles arise because gases (e.g., water vapor or cryogenic gases) can condense in pores. This condensation contributes to weight, and in the case of cryogenic systems, the heat of condensation undesirably adds to the heat flowing to the objects that one seeks to keep cold. Moreover, there is a risk of explosion associated with vaporization of previously condensed gas upon reheating. Aerogels offer low permeability, low density, and low thermal conductivity, but are mechanically fragile. The basic idea of the present invention is to exploit the best features of fibrous ceramic tiles and aerogels. In a composite tile according to the invention, the fibrous ceramic serves as a matrix that mechanically supports the aerogel, while the aerogel serves as a low-conductivity, low-permeability filling that closes what would otherwise be the open pores of the fibrous ceramic. Because the aerogel eliminates or at least suppresses permeation by gas, gas-phase conduction, and convection, the thermal conductivity of such a composite even at

  20. Silica Aerogel Captures Cosmic Dust Intact

    NASA Technical Reports Server (NTRS)

    Tsou, P.

    1994-01-01

    The mesostructure of silica aerogel resembles stings of grapes, ranging in size from 10 to 100 angstrom. This fine mesostructure transmits nearly 90 percent of incident light in the visible, while providing sufficiently gentle dissipation of the kinetric energy of hypervelocity cosmic dust particles to permit their intact capture. We introduced silica aerogel in 1987 as capture medium to take advantage of its low density, fine mesostruicture and most importantly, its transparency, allowing optical location of captured micron sized particles.

  1. High Temperature Aerogels for Thermal Protection Systems

    NASA Technical Reports Server (NTRS)

    Hurwitz, Frances I.; Mbah, Godfrey C.

    2008-01-01

    High temperature aerogels in the Al2O3-SiO2 system are being investigated as possible constituents for lightweight integrated thermal protection system (TPS) designs for use in supersonic and hypersonic applications. Gels are synthesized from ethoxysilanes and AlCl3.6H2O, using an epoxide catalyst. The influence of Al:Si ratio, solvent, water to metal and water to alcohol ratios on aerogel composition, morphology, surface area, and pore size distribution were examined, and phase transformation on heat treatment characterized. Aerogels have been fabricated which maintain porous, fractal structures after brief exposures to 1000 C. Incorporation of nanofibers, infiltration of aerogels into SiC foams, use of polymers for crosslinking the aerogels, or combinations of these, offer potential for toughening and integration of TPS with composite structure. Woven fabric composites having Al2O3-SiO2 aerogels as a matrix also have been fabricated. Continuing work is focused on reduction in shrinkage and optimization of thermal and physical properties.

  2. Aerogel Composites for Aerospace Thermal Protection

    NASA Technical Reports Server (NTRS)

    White, Susan

    2003-01-01

    Aerogel composites formed by infiltrating organic and/or inorganic aerogels into fiber matrix materials enable us to exploit the low thermal conductivity and low density of aerogels while maintaining the strength, structure and other useful properties of a porous fiber matrix. New materials for extreme heating ranges are needed to insulate future spacecraft against the extreme heat of planetary atmospheric entry, but the insulation mass must be minimized in order to maximize the payload. A reusable system passively insulates to survive heating unchanged for relatively low heating. Ablators, which sacrifice mass to control heating, are used to protect vehicles against more extreme heating for a single use thermal protection system (TPS). Aerogel composites were fabricated and tested for spacecraft thermal protection. The high-temperaturey high heat flux tests described in this paper were performed in NASA Ames arc-jet facilities to simulate spacecraft atmospheric entry, and include heating conditions predicted for the forebody and backshell of the Mars Science Lander (MSL) entry probe. The aerogel composites tested showed excellent thermal performance in the arc-jet tests, functioning both as reusuable insulation under lower heat fluxes, and as ablative aerogels under the extreme heating predicted for the MSL forebody.

  3. Pore morphology study of silica aerogels

    SciTech Connect

    Hua, D.W.; Anderson, J.; Haereid, S.; Smith, D.M.

    1994-12-31

    Silica aerogels have numerous properties which suggest applications such as ultra high efficiency thermal insulation. These properties relate directly to the aerogel`s pore size distribution. The micro and meso pore size ranges can be investigated by normal small angle x-ray scattering and possibly, nitrogen adsorption. However, the measurement of larger pores (> 250 {angstrom}) is more difficult. Due to their limited mechanical strength, mercury porosimetry and nitrogen condensation can disrupt the gel structure and electron microscopy provides only limited large scale structure information. The use of small angle light scattering techniques seems to have promise, the only hurdle is that aerogels exhibit significant multiple scattering. This can be avoided if one observes the gels in the wet stage since the structure of the aerogel should be very similar to the wet gel (as the result of supercritical drying). Thus, if one can match the refractive index, the morphology can be probed. The combination of certain alcoholic solvents fit this index matching criteria. Preliminary results for the gel network (micron range) and primary particle structure (manometer) are reported by using small angle light scattering and ultra-small angle x-ray scattering. The effects on structure over the length scale range of <1 nm to >5 {mu}m under different conditions (precursors, pH, etc.) are presented. The change in structure of an aerogel during isostatic compaction to 228 MPa (to simulate drying from wetting solvents) are also discussed.

  4. Ambient pressure process for preparing aerogel thin films reliquified sols useful in preparing aerogel thin films

    DOEpatents

    Brinker, Charles Jeffrey; Prakash, Sai Sivasankaran

    1999-01-01

    A method for preparing aerogel thin films by an ambient-pressure, continuous process. The method of this invention obviates the use of an autoclave and is amenable to the formation of thin films by operations such as dip coating. The method is less energy intensive and less dangerous than conventional supercritical aerogel processing techniques.

  5. Less-costly activated carbon for sewage treatment

    NASA Technical Reports Server (NTRS)

    Ingham, J. D.; Kalvinskas, J. J.; Mueller, W. A.

    1977-01-01

    Lignite-aided sewage treatment is based on absorption of dissolved pollutants by activated carbon. Settling sludge is removed and dried into cakes that are pyrolyzed with lignites to yield activated carbon. Lignite is less expensive than activated carbon previously used to supplement pyrolysis yield.

  6. Hierarchically structured activated carbon for ultracapacitors

    PubMed Central

    Kim, Mok-Hwa; Kim, Kwang-Bum; Park, Sun-Min; Roh, Kwang Chul

    2016-01-01

    To resolve the pore-associated bottleneck problem observed in the electrode materials used for ultracapacitors, which inhibits the transport of the electrolyte ions, we designed hierarchically structured activated carbon (HAC) by synthesizing a mesoporous silica template/carbon composite and chemically activating it to simultaneously remove the silica template and increase the pore volume. The resulting HAC had a well-designed, unique porous structure, which allowed for large interfaces for efficient electric double-layer formation. Given the unique characteristics of the HAC, we believe that the developed synthesis strategy provides important insights into the design and fabrication of hierarchical carbon nanostructures. The HAC, which had a specific surface area of 1,957 m2 g−1, exhibited an extremely high specific capacitance of 157 F g−1 (95 F cc−1), as well as a high rate capability. This indicated that it had superior energy storage capability and was thus suitable for use in advanced ultracapacitors. PMID:26878820

  7. Durable polymer-aerogel based superhydrophobic coatings: a composite material

    DOEpatents

    Kissel, David J.; Brinker, Charles Jeffrey

    2016-02-02

    Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

  8. Durable polymer-aerogel based superhydrophobic coatings, a composite material

    DOEpatents

    Kissel, David J; Brinker, Charles Jeffrey

    2014-03-04

    Provided are polymer-aerogel composite coatings, devices and articles including polymer-aerogel composite coatings, and methods for preparing the polymer-aerogel composite. The exemplary article can include a surface, wherein the surface includes at least one region and a polymer-aerogel composite coating disposed over the at least one region, wherein the polymer-aerogel composite coating has a water contact angle of at least about 140.degree. and a contact angle hysteresis of less than about 1.degree.. The polymer-aerogel composite coating can include a polymer and an ultra high water content catalyzed polysilicate aerogel, the polysilicate aerogel including a three dimensional network of silica particles having surface functional groups derivatized with a silylating agent and a plurality of pores.

  9. Aerogels: A new material for emissive display applications

    SciTech Connect

    Glauser, S.A.C.; Lee, H.W.H.

    1997-03-01

    The remarkable optical and electronic properties of doped and undoped silica aerogels establish their utility as unique, multifunctional host materials for fluorescent dyes and other luminescent materials for display and imaging applications. We present results on the photoluminescence and absorption of undoped silica aerogels and aerogels doped with Er{sup 3+}, rhodamine 6G (R6G), and fluorescein. We also demonstrate evidence of Fowler-Nordheim tunneling of electrons in aerogels. 4 refs., 10 figs.

  10. System and method for suppressing sublimation using opacified aerogel

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeff S. (Inventor); Snyder, G. Jeffrey (Inventor); Calliat, Thierry (Inventor); Fleurial, Jean-Pierre (Inventor); Jones, Steven M. (Inventor); Palk, Jong-Ah (Inventor)

    2008-01-01

    The present invention relates to a castable, aerogel-based, ultra-low thermal conductivity opacified insulation to suppress sublimation. More specifically, the present invention relates to an aerogel opacified with various opacifying or reflecting constituents to suppress sublimation and provide thermal insulation in thermoelectric modules. The opacifying constituent can be graded within the aerogel for increased sublimation suppression, and the density of the aerogel can similarly be graded to achieve optimal thermal insulation and sublimation suppression.

  11. Eureka! Aerogel capture of meteoroids in space

    NASA Technical Reports Server (NTRS)

    Brownlee, D. E.; Horz, F.; Hrubsch, L.; Mcdonnell, J. A. M.; Tsou, P.; Williams, J.

    1994-01-01

    Light gas gun studies have shown that 6 km/s solid mineral and glass test particles can be successively captured in 0.05 g cm(exp -3) aerogel without severe heating or fragmentation. In spite of this work, there has been uncertainty in the performance of aerogel for hypervelocity capture of real meteoroids. Natural impacts differ from simulations in that the particles are likely to be structurally weak and they typically impact at higher velocity that can be simulated in the laboratory. We are fortunate now to have had two successful capture experiments using aerogel exposed in space. These experiments provide fundamental data for the assessment of the value of silica aerogel for capture of hypervelocity meteoroids from spacecraft. The first experiment used 0.02 g cm(exp -3) aerogel flown on the lid of a Shuttle Get Away Special canister. During its 9 day exposure, the 0.165 m(exp 2) of aerogel in this Sample Return Experiment (SRE) captured two long 'carrot-shaped' tracks and one highly fractured bowl shaped 'crater'. The second collection was with 0.04 m(exp 2) of 0.05 g cm(exp -3) aerogel exposed on ESA's Eureca freeflying spacecraft that was exposed for 11 months before recovery by the Shuttle. The Eureca aerogel exposure consisted of four 10x10 cm module trays that were part of the TiCCE meteoroid collector built by the University of Kent at Canterbury. To date we have found ten 'carrot-shaped' tracks and two 'craters' on this experiment. The longest tracks in both exposures are over 2 mm long. Two of the TiCCE modules had a 0.1 micron Al film suspended a millimeter above the aerogel. On these modules several of the projectiles fragmented during passage through the film producing fields of carrot shaped tracks from the resulting miniature 'meteor' shower. Most of the tracks in these showers have observable particles at their ends. We have extracted one of the carrot track meteoroids and mounted it in epoxy for sectioning. So far the examination of these 14

  12. Vibration damping with active carbon fiber structures

    NASA Astrophysics Data System (ADS)

    Neugebauer, Reimund; Kunze, Holger; Riedel, Mathias; Roscher, Hans-Jürgen

    2007-04-01

    This paper presents a mechatronic strategy for active reduction of vibrations on machine tool struts or car shafts. The active structure is built from a carbon fiber composite with embedded piezofiber actuators that are composed of piezopatches based on the Macro Fiber Composite (MFC) technology, licensed by NASA and produced by Smart Material GmbH in Dresden, Germany. The structure of these actuators allows separate or selectively combined bending and torsion, meaning that both bending and torsion vibrations can be actively absorbed. Initial simulation work was done with a finite element model (ANSYS). This paper describes how state space models are generated out of a structure based on the finite element model and how controller codes are integrated into finite element models for transient analysis and the model-based control design. Finally, it showcases initial experimental findings and provides an outlook for damping multi-mode resonances with a parallel combination of resonant controllers.

  13. Charcoal and activated carbon at elevated pressure

    SciTech Connect

    Antal, M.J. Jr.; Dai, Xiangfeng; Norberg, N.

    1995-12-01

    High quality charcoal has been produced with very high yields of 50% to 60% from macadamia nut and kukui nut shells and of 44% to 47% from Eucalyptus and Leucaena wood in a bench scale unit at elevated pressure on a 2 to 3 hour cycle, compared to commercial practice of 25% to 30% yield on a 7 to 12 day operating cycle. Neither air pollution nor tar is produced by the process. The effects of feedstock pretreatments with metal additives on charcoal yield are evaluated in this paper. Also, the influences of steam and air partial pressure and total pressure on yields of activated carbon from high yield charcoal are presented.

  14. Adsorbed natural gas storage with activated carbon

    SciTech Connect

    Sun, Jian; Brady, T.A.; Rood, M.J.

    1996-12-31

    Despite technical advances to reduce air pollution emissions, motor vehicles still account for 30 to 70% emissions of all urban air pollutants. The Clean Air Act Amendments of 1990 require 100 cities in the United States to reduce the amount of their smog within 5 to 15 years. Hence, auto emissions, the major cause of smog, must be reduced 30 to 60% by 1998. Natural gas con be combusted with less pollutant emissions. Adsorbed natural gas (ANG) uses adsorbents and operates with a low storage pressure which results in lower capital costs and maintenance. This paper describes the production of an activated carbon adsorbent produced from an Illinois coal for ANG.

  15. A hybrid-assembly approach towards nitrogen-doped graphene aerogel supported cobalt nanoparticles as high performance oxygen reduction electrocatalysts.

    PubMed

    Liu, Ruili; Jin, Yeqing; Xu, Peimin; Xing, Xia; Yang, Yuxing; Wu, Dongqing

    2016-02-15

    As a novel electrocatalyst for oxygen reduction reaction (ORR), nitrogen-doped graphene aerogel supported cobalt nanoparticles (Co-NGA) is archived by a hybrid-assembly of graphene oxide (GO), o-phthalonitrile and cobalt acetate and the following thermal treatment. The hybrid-assembly process successfully combines the ionic assembly of GO sheets and Co ions with the coordination between o-phthalonitrile and Co ions, which can be converted to nitrogen doped carbon and Co nanoparticles in the pyrolysis process under nitrogen flow. Remarkable features of Co-NGA including the macroporous graphene scaffolds, high surface area, and N/Co-doping effect can lead to a high catalytic efficiency for ORR. As the results, the composites pyrolyzed at 600°C (Co-NGA600) shows excellent electrocatalytic activities and kinetics for ORR in basic media, which are comparable with those of Pt/C catalyst, together with superior durability.

  16. Production of activated carbon from TCR char

    NASA Astrophysics Data System (ADS)

    Stenzel, Fabian; Heberlein, Markus; Klinner, Tobias; Hornung, Andreas

    2016-04-01

    The utilization of char for adsorptive purposes is known since the 18th century. At that time the char was made of wood or bones and used for decoloration of fluids. In the 20th century the production of activated carbon in an industrial scale was started. The today's raw materials for activated carbon production are hard coal, peat, wood or coconut shells. All these materials entail costs especially the latter. Thus, the utilization of carbon rich residues (biomass) is an interesting economic opportunity because it is available for no costs or even can create income. The char is produced by thermo-catalytic reforming (TCR®). This process is a combination of an intermediate pyrolysis and subsequently a reforming step. During the pyrolysis step the material is decomposed in a vapor and a solid carbon enriched phase. In the second step the vapor and the solid phase get in an intensive contact and the quality of both materials is improved via the reforming process. Subsequently, the condensables are precipitated from the vapor phase and a permanent gas as well as oil is obtained. Both are suitable for heat and power production which is a clear advantage of the TCR® process. The obtained biochar from the TCR® process has special properties. This material has a very low hydrogen and oxygen content. Its stability is comparable to hard coal or anthracite. Therefore it consists almost only of carbon and ash. The latter depends from input material. Furthermore the surface structure and area can be influenced during the reforming step. Depending from temperature and residence time the number of micro pores and the surface area can be increased. Preliminary investigations with methylene blue solution have shown that a TCR® char made of digestate from anaerobic digestion has adsorptive properties. The decoloration of the solution was achieved. A further influencing factor of the adsorption performance is the particle size. Based on the results of the preliminary tests a

  17. Mesoporous Carbon for Capacitive Deionization of Saline Water

    SciTech Connect

    Tsouris, Costas; Mayes, Richard T; Kiggans, Jim; Sharma, Ms. Ketki; Yiacoumi, Sotira; DePaoli, David W; Dai, Sheng

    2011-01-01

    Self-assembled mesoporous carbon (MC) materials have been synthesized and tested for application in capacitive deionization (CDI) of saline water. MC was prepared by self-assembly of a triblock copolymer with hydrogen-bonded chains via a phenolic resin, such as resorcinol or phloroglucinol in acidic conditions, followed by carbonization and, in some cases, activation by KOH. Carbon synthesized in this way was ground into powder, from which activated MC sheets were produced. In a variation of this process, after the reaction of triblock copolymer with resorcinol or phloroglucinol, the gel that was formed was used to coat a graphite plate and then carbonized. The coated graphite plate in this case was not activated and was tested to serve as current collector during the CDI process. The performance of these MC materials was compared to that of carbon aerogel for salt concentrations ranging between 1000 ppm and 35,000 ppm. Resorcinol-based MC removed up to 15.2 mg salt per gram of carbon, while carbon aerogel removed 5.8 mg salt per gram of carbon. Phloroglucinol-based MC-coated graphite exhibited the highest ion removal capacity at 21 mg of salt per gram of carbon for 35,000 ppm salt concentration.

  18. Plasmonic enhancement of visible-light water splitting with Au-TiO2 composite aerogels.

    PubMed

    DeSario, Paul A; Pietron, Jeremy J; DeVantier, Devyn E; Brintlinger, Todd H; Stroud, Rhonda M; Rolison, Debra R

    2013-09-01

    We demonstrate plasmonic enhancement of visible-light-driven splitting of water at three-dimensionally (3D) networked gold-titania (Au-TiO2) aerogels. The sol-gel-derived ultraporous composite nanoarchitecture, which contains 1 to 8.5 wt% Au nanoparticles and titania in the anatase form, retains the high surface area and mesoporosity of unmodified TiO2 aerogels and maintains stable dispersion of the ~5 nm Au guests. A broad surface plasmon resonance (SPR) feature centered at ~550 nm is present for the Au-TiO2 aerogels, but not Au-free TiO2 aerogels, and spans a wide range of the visible spectrum. Gold-derived SPR in Au-TiO2 aerogels cast as films on transparent electrodes drives photoelectrochemical oxidation of aqueous hydroxide and extends the photocatalytic activity of TiO2 from the ultraviolet region to visible wavelengths exceeding 700 nm. Films of Au-TiO2 aerogels in which Au nanoparticles are deposited on pre-formed TiO2 aerogels by a deposition-precipitation method (DP Au/TiO2) also photoelectrochemically oxidize aqueous hydroxide, but less efficiently than 3D Au-TiO2, despite having an essentially identical Au nanoparticle weight fraction and size distribution. For example, 3D Au-TiO2 containing 1 wt% Au is as active as DP Au/TiO2 with 4 wt% Au. The higher photocatalytic activity of 3D Au-TiO2 derives only in part from its ability to retain the surface area and porosity of unmodified TiO2 aerogel. The magnitude of improvement indicates that in the 3D arrangement either a more accessible photoelectrochemical reaction interphase (three-phase boundary) exists or more efficient conversion of excited surface plasmons into charge carriers occurs, thereby amplifying reactivity over DP Au/TiO2. The difference in photocatalytic efficiency between the two forms of Au-TiO2 demonstrates the importance of defining the structure of Au[parallel]TiO2 interfaces within catalytic Au-TiO2 nanoarchitectures. PMID:23877169

  19. Reduction of bromate by granular activated carbon

    SciTech Connect

    Kirisits, M.J.; Snoeyink, V.L.; Kruithof, J.C.

    1998-07-01

    Ozonation of waters containing bromide can lead to the formation of bromate, a probable human carcinogen. Since bromate will be regulated at 10 {micro}g/L by the Stage 1 Disinfectants/Disinfection By-Products Rule, there is considerable interest in finding a suitable method of bromate reduction. Granular activated carbon (GAC) can be used to chemically reduce bromate to bromide, but interference from organic matter and anions present in natural water render this process inefficient. In an effort to improve bromate reduction by GAC, several modifications were made to the GAC filtration process. The use of a biologically active carbon (BAC) filter ahead of a fresh GAC filter with and without preozonation, to remove the biodegradable organic matter, did not substantially improve the bromate removal of the GAC filter. The use of the BAC filter for biological bromate reduction proved to be the most encouraging experiment. By lowering the dissolved oxygen in the influent to the BAC from 8.0 mg/L to 2.0 mg/L, the percent bromate removal increased from 42% to 61%.

  20. Aerogel/Particle Composites for Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Sakamoto, Jeffrey; Jones, Steven

    2006-01-01

    Optimizing solution chemistry and the addition of titania and fumed silica powder reduces shrinkage. These materials would serve to increase thermal efficiency by providing thermal insulation to suppress lateral heat leaks. They would also serve to prolong operational lifetime by suppressing sublimation of certain constituents of thermoelectric materials (e.g., sublimation of Sb from CoSb3) at typical high operating temperatures. [The use of pure silica aerogels as cast-in-place thermal-insulation and sublimation-suppression materials was described in "Aerogels for Thermal Insulation of Thermoelectric Devices" (NPO-40630), NASA Tech Briefs, Vol. 30, No. 7 (July 2006), page 50.] A silica aerogel is synthesized in a solgel process that includes preparation of a silica sol, gelation of the sol, and drying of the gel in a solvent at a supercritical temperature and pressure. The utility of pure silica aerogel is diminished by a tendency to shrink (and, therefore, also to crack) during the gelation and supercritical-drying stages. Moreover, to increase suppression of sublimation, it is advantageous to make an aerogel having greater density, but shrinkage and cracking tend to increase with density. A composite material of the type under investigation consists mostly of titania oxide powder particles and a small addition of fumed silica powder, which are mixed into the sol along with other ingredients prior to the gelation stage of processing. The silica aerogel and fumed silica act as a binder, gluing the titania particles together. It is believed that the addition of fumed silica stiffens the aerogel network and reduces shrinkage during the supercritical-drying stage. Minimization of shrinkage enables establishment of intimate contact between thermoelectric legs and the composite material, thereby maximizing the effectiveness of the material for thermal insulation and suppression of sublimation. To some extent, the properties of the composite can be tailored via the

  1. Three-Dimensional Assembly of Yttrium Oxide Nanosheets into Luminescent Aerogel Monoliths with Outstanding Adsorption Properties.

    PubMed

    Cheng, Wei; Rechberger, Felix; Niederberger, Markus

    2016-02-23

    The preparation of macroscopic materials from two-dimensional nanostructures represents a great challenge. Restacking and random aggregation to dense structures during processing prevents the preservation of the two-dimensional morphology of the nanobuilding blocks in the final body. Here we present a facile solution route to ultrathin, crystalline Y2O3 nanosheets, which can be assembled into a 3D network by a simple centrifugation-induced gelation method. The wet gels are converted into aerogel monoliths of macroscopic dimensions via supercritical drying. The as-prepared, fully crystalline Y2O3 aerogels show high surface areas of up to 445 m(2)/g and a very low density of 0.15 g/cm(3), which is only 3% of the bulk density of Y2O3. By doping and co-doping the Y2O3 nanosheets with Eu(3+) and Tb(3+), we successfully fabricated luminescent aerogel monoliths with tunable color emissions from red to green under UV excitation. Moreover, the as-prepared gels and aerogels exhibit excellent adsorption capacities for organic dyes in water without losing their structural integrity. For methyl blue we measured an unmatched adsorption capacity of 8080 mg/g. Finally, the deposition of gold nanoparticles on the nanosheets gave access to Y2O3-Au nanocomposite aerogels, proving that this approach may be used for the synthesis of catalytically active materials. The broad range of properties including low density, high porosity, and large surface area in combination with tunable photoluminescence makes these Y2O3 aerogels a truly multifunctional material with potential applications in optoelectronics, wastewater treatment, and catalysis. PMID:26756944

  2. Three-Dimensional Assembly of Yttrium Oxide Nanosheets into Luminescent Aerogel Monoliths with Outstanding Adsorption Properties.

    PubMed

    Cheng, Wei; Rechberger, Felix; Niederberger, Markus

    2016-02-23

    The preparation of macroscopic materials from two-dimensional nanostructures represents a great challenge. Restacking and random aggregation to dense structures during processing prevents the preservation of the two-dimensional morphology of the nanobuilding blocks in the final body. Here we present a facile solution route to ultrathin, crystalline Y2O3 nanosheets, which can be assembled into a 3D network by a simple centrifugation-induced gelation method. The wet gels are converted into aerogel monoliths of macroscopic dimensions via supercritical drying. The as-prepared, fully crystalline Y2O3 aerogels show high surface areas of up to 445 m(2)/g and a very low density of 0.15 g/cm(3), which is only 3% of the bulk density of Y2O3. By doping and co-doping the Y2O3 nanosheets with Eu(3+) and Tb(3+), we successfully fabricated luminescent aerogel monoliths with tunable color emissions from red to green under UV excitation. Moreover, the as-prepared gels and aerogels exhibit excellent adsorption capacities for organic dyes in water without losing their structural integrity. For methyl blue we measured an unmatched adsorption capacity of 8080 mg/g. Finally, the deposition of gold nanoparticles on the nanosheets gave access to Y2O3-Au nanocomposite aerogels, proving that this approach may be used for the synthesis of catalytically active materials. The broad range of properties including low density, high porosity, and large surface area in combination with tunable photoluminescence makes these Y2O3 aerogels a truly multifunctional material with potential applications in optoelectronics, wastewater treatment, and catalysis.

  3. Nano-casted Metal Oxide Aerogels as Dual Purpose Structural Components for Space Exploration

    NASA Technical Reports Server (NTRS)

    Vassilaras, Plousia E.

    2004-01-01

    NASA missions and space exploration rely on strong, ultra lightweight materials. Such materials are needed for building up past and present space vehicles such as the Sojourner Rover (1997) or the two MERs (2003), but also for a number of components and/or systems including thermal insulators, Solar Sails, Rigid Aeroshells, and Ballutes. The purpose of my internship here at Glenn Research Center is to make dual purpose materials; materials that in addition to being lightweight have electronic, photophysical and magnetic properties and, therefore, act as electronic components and sensors as well as structural components. One type of ultra lightweight material of great interest is aerogels, which have densities ranging from 0.003 g/cc to 0.8 g/cc . However, aerogels are extremely fragile and, as a result, have limited practical applications. Recently, Glenn Research Center has developed a process of nano-casting polymers onto the inorganic network of silica-based aerogels increasing the strength 300 fold while only increasing the density 3 fold. By combining the process of nano-casting polymers with inorganic oxide networks other than silica, we are actively pursuing lightweight dual purpose materials. To date, thirty different inorganic oxide aerogels have been prepared using either standard sol-gel chemistry or a non-alkoxide method involving metal chloride precursors and an epoxide; epichlorohydrin, propylene oxide or trimethylene oxide, as proton scavengers. More importantly, preliminary investigations show that the residual surface hydroxyl groups on each of these inorganic oxide aerogels can be successfully crosslinked with urethane. In addition to characterizing physical and mechanical properties such as density, strength and flexibility, each of these metal oxide aerogels are being characterized for thermal and electronic conductivity and magnetic and optical properties.

  4. REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...

  5. Volatiles in interplanetary dust particles and aerogels

    NASA Technical Reports Server (NTRS)

    Gibson, E. K., Jr.; Harmetz, C. P.

    1991-01-01

    Volatiles measured in 25 interplanetary dust particles (IDPs) are a mixture of both indigenous materials and contaminants associated with the collection and processing of the ODPs prior to analysis. Most IDPs have been collected in the stratosphere using a silicone oil/freon mixture (20:1 ratio) coated on collector plates. Studies have shown that silicone oil, freon and hexane residues remain with the ODPs, despite attempts to clean the IDPs. Analysis of the IDPs with the LMMS-technique produces spectra with a mixture of indigeneous and contaminants components. The contamination signal can be identified and removed; however, the contamination signal may obscure some of the indigeneous component's signal. Employing spectra stripping techniques, the indigenous volatile constituents associated with the IDPs can be identified. Volatiles are similar to those measured in CI or CM carbonaceous chondrites. Collection of IDPs in low-Earth orbit utilizing a Cosmic Dust Collection Facility attached to Space Station Freedom has been proposed. The low-density material aerogel has been proposed as a collection substrate for IDPs. Our studies have concentrated on identifying volatile contaminants that are associated with aerogel. We have found that solvents used for the preparation of aerogel remain in aerogel and methods must be developed for removing the entrapped solvents before aerogels can be used for an IDP collection substrate.

  6. Aerogel Beads as Cryogenic Thermal Insulation System

    NASA Technical Reports Server (NTRS)

    Fesmire, J. E.; Augustynowicz, S. D.; Rouanet, S.; Thompson, Karen (Technical Monitor)

    2001-01-01

    An investigation of the use of aerogel beads as thermal insulation for cryogenic applications was conducted at the Cryogenics Test Laboratory of NASA Kennedy Space Center. Steady-state liquid nitrogen boiloff methods were used to characterize the thermal performance of aerogel beads in comparison with conventional insulation products such as perlite powder and multilayer insulation (MLI). Aerogel beads produced by Cabot Corporation have a bulk density below 100 kilograms per cubic meter (kg/cubic m) and a mean particle diameter of 1 millimeter (mm). The apparent thermal conductivity values of the bulk material have been determined under steady-state conditions at boundary temperatures of approximately 293 and 77 kelvin (K) and at various cold vacuum pressures (CVP). Vacuum levels ranged from 10(exp -5) torr to 760 torr. All test articles were made in a cylindrical configuration with a typical insulation thickness of 25 mm. Temperature profiles through the thickness of the test specimens were also measured. The results showed the performance of the aerogel beads was significantly better than the conventional materials in both soft-vacuum (1 to 10 torr) and no-vacuum (760 torr) ranges. Opacified aerogel beads performed better than perlite powder under high-vacuum conditions. Further studies for material optimization and system application are in progress.

  7. Determination of Young's modulus of silica aerogels using holographic interferometry

    NASA Astrophysics Data System (ADS)

    Chikode, Prashant P.; Sabale, Sandip R.; Vhatkar, Rajiv S.

    2016-05-01

    Digital holographic interferometry technique is used to determine elastic modulus of silica aerogels. Tetramethoxysilane precursor based Silica aerogels were prepared by the sol-gel process followed by supercritical methanol drying. The alcogels were prepared by keeping the molar ratio of tetramethoxysilane: methyltrimethoxysilane: H2O constant at 1:0.6:4 while the methanol / tetramethoxysilane molar ratio (M) was varied systematically from 12 to 18. Holograms of translucent aerogel samples have been successfully recorded using the digital holographic interferometry technique. Stimulated digital interferograms gives localization of interference fringes on the aerogel surface and these fringes are used to determine the surface deformation and Young's modulus (Y) of the aerogels.

  8. Strong, conductive, lightweight, neat graphene aerogel fibers with aligned pores.

    PubMed

    Xu, Zhen; Zhang, Yuan; Li, Peigang; Gao, Chao

    2012-08-28

    Liquid crystals of anisotropic colloids are of great significance in the preparation of their ordered macroscopic materials, for example, in the cases of carbon nanotubes and graphene. Here, we report a facile and scalable spinning process to prepare neat "core-shell" structured graphene aerogel fibers and three-dimensional cylinders with aligned pores from the flowing liquid crystalline graphene oxide (GO) gels. The uniform alignment of graphene sheets, inheriting the lamellar orders from GO liquid crystals, offers the porous fibers high specific tensile strength (188 kN m kg(-1)) and the porous cylinders high compression modulus (3.3 MPa). The porous graphene fibers have high specific surface area up to 884 m(2) g(-1) due to their interconnected pores and exhibit fine electrical conductivity (2.6 × 10(3) to 4.9 × 10(3) S m(-1)) in the wide temperature range of 5-300 K. The decreasing conductivity with decreasing temperature illustrates a typical semiconducting behavior, and the 3D interconnected network of 2D graphene sheets determines a dual 2D and 3D hopping conduction mechanism. The strong mechanical strength, high porosity, and fine electrical conductivity enable this novel material of ordered graphene aerogels to be greatly useful in versatile catalysts, supercapacitors, flexible batteries and cells, lightweight conductive fibers, and functional textiles. PMID:22799441

  9. Strong, conductive, lightweight, neat graphene aerogel fibers with aligned pores.

    PubMed

    Xu, Zhen; Zhang, Yuan; Li, Peigang; Gao, Chao

    2012-08-28

    Liquid crystals of anisotropic colloids are of great significance in the preparation of their ordered macroscopic materials, for example, in the cases of carbon nanotubes and graphene. Here, we report a facile and scalable spinning process to prepare neat "core-shell" structured graphene aerogel fibers and three-dimensional cylinders with aligned pores from the flowing liquid crystalline graphene oxide (GO) gels. The uniform alignment of graphene sheets, inheriting the lamellar orders from GO liquid crystals, offers the porous fibers high specific tensile strength (188 kN m kg(-1)) and the porous cylinders high compression modulus (3.3 MPa). The porous graphene fibers have high specific surface area up to 884 m(2) g(-1) due to their interconnected pores and exhibit fine electrical conductivity (2.6 × 10(3) to 4.9 × 10(3) S m(-1)) in the wide temperature range of 5-300 K. The decreasing conductivity with decreasing temperature illustrates a typical semiconducting behavior, and the 3D interconnected network of 2D graphene sheets determines a dual 2D and 3D hopping conduction mechanism. The strong mechanical strength, high porosity, and fine electrical conductivity enable this novel material of ordered graphene aerogels to be greatly useful in versatile catalysts, supercapacitors, flexible batteries and cells, lightweight conductive fibers, and functional textiles.

  10. DEVELOPMENT OF ACTIVATED CARBONS FROM COAL COMBUSTION BY-PRODUCTS

    SciTech Connect

    Harold H. Schobert; M. Mercedes Maroto-Valer; Zhe Lu

    2003-09-30

    The increasing role of coal as a source of energy in the 21st century will demand environmental and cost-effective strategies for the use of coal combustion by-products (CCBPs), mainly unburned carbon in fly ash. Unburned carbon is nowadays regarded as a waste product and its fate is mainly disposal, due to the present lack of efficient routes for its utilization. However, unburned carbon is a potential precursor for the production of adsorbent carbons, since it has gone through a devolatilization process while in the combustor, and therefore, only requires to be activated. Accordingly, the principal objective of this work was to characterize and utilize the unburned carbon in fly ash for the production of activated carbons. The unburned carbon samples were collected from different combustion systems, including pulverized utility boilers, a utility cyclone, a stoker, and a fluidized bed combustor. LOI (loss-on-ignition), proximate, ultimate, and petrographic analyses were conducted, and the surface areas of the samples were characterized by N2 adsorption isotherms at 77K. The LOIs of the unburned carbon samples varied between 21.79-84.52%. The proximate analyses showed that all the samples had very low moisture contents (0.17 to 3.39 wt %), while the volatile matter contents varied between 0.45 to 24.82 wt%. The elemental analyses show that all the unburned carbon samples consist mainly of carbon with very little hydrogen, nitrogen, sulfur and oxygen In addition, the potential use of unburned carbon as precursor for activated carbon (AC) was investigated. Activated carbons with specific surface area up to 1075m{sup 2}/g were produced from the unburned carbon. The porosity of the resultant activated carbons was related to the properties of the unburned carbon feedstock and the activation conditions used. It was found that not all the unburned carbon samples are equally suited for activation, and furthermore, their potential as activated carbons precursors could be

  11. Fluorine-Free Oil Absorbents Made from Cellulose Nanofibril Aerogels.

    PubMed

    Mulyadi, Arie; Zhang, Zhe; Deng, Yulin

    2016-02-01

    Aerogels based on cellulose nanofibrils (CNFs) have been of great interest as absorbents due to their high absorption capacity, low density, biodegradability, and large surface area. Hydrophobic aerogels have been designed to give excellent oil absorption tendency from water. Herein, we present an in situ method for CNF surface modification and hydrophobic aerogel preparation. Neither solvent exchange nor fluorine chemical is used in aerogel preparations. The as-prepared hydrophobic aerogels exhibit low density (23.2 mg/cm(-3)), high porosity (98.5%), good flexibility, and solvent-induced shape recovery property. Successful surface modification was confirmed through field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and water contact angle measurements. The hydrophobic aerogels show high absorption capacities for various oils, depending on liquid density, up to 47× their original weight but with low water uptake (<0.5 g/g aerogel). PMID:26761377

  12. Merging allylic carbon-hydrogen and selective carbon-carbon bond activation

    NASA Astrophysics Data System (ADS)

    Masarwa, Ahmad; Didier, Dorian; Zabrodski, Tamar; Schinkel, Marvin; Ackermann, Lutz; Marek, Ilan

    2014-01-01

    Since the nineteenth century, many synthetic organic chemists have focused on developing new strategies to regio-, diastereo- and enantioselectively build carbon-carbon and carbon-heteroatom bonds in a predictable and efficient manner. Ideal syntheses should use the least number of synthetic steps, with few or no functional group transformations and by-products, and maximum atom efficiency. One potentially attractive method for the synthesis of molecular skeletons that are difficult to prepare would be through the selective activation of C-H and C-C bonds, instead of the conventional construction of new C-C bonds. Here we present an approach that exploits the multifold reactivity of easily accessible substrates with a single organometallic species to furnish complex molecular scaffolds through the merging of otherwise difficult transformations: allylic C-H and selective C-C bond activations. The resulting bifunctional nucleophilic species, all of which have an all-carbon quaternary stereogenic centre, can then be selectively derivatized by the addition of two different electrophiles to obtain more complex molecular architecture from these easily available starting materials.

  13. Nanotube Aerogel Sheet Flutter for Actuation, Power Generation, and Infrasound Detection

    PubMed Central

    Kang, Tae June; Kim, Taewoo; Jang, Eui Yun; Im, Hyeongwook; Lepro-Chavez, Xavier; Ovalle-Robles, Raquel; Oh, Jiyoung; Kozlov, Mikhail E.; Baughman, Ray H.; Lee, Hong H.; Kim, Yong Hyup

    2014-01-01

    Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect infrasound at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for infrasound frequencies. PMID:25130708

  14. Nanotube aerogel sheet flutter for actuation, power generation, and infrasound detection.

    PubMed

    Kang, Tae June; Kim, Taewoo; Jang, Eui Yun; Im, Hyeongwook; Lepro-Chavez, Xavier; Ovalle-Robles, Raquel; Oh, Jiyoung; Kozlov, Mikhail E; Baughman, Ray H; Lee, Hong H; Kim, Yong Hyup

    2014-01-01

    Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect infrasound at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for infrasound frequencies. PMID:25130708

  15. Metal-carbon nanocomposites based on activated IR pyrolized polyacrylonitrile

    NASA Astrophysics Data System (ADS)

    Efimov, Mikhail N.; Zhilyaeva, Natalya A.; Vasilyev, Andrey A.; Muratov, Dmitriy G.; Zemtsov, Lev M.; Karpacheva, Galina P.

    2016-05-01

    In this paper we report about new approach to preparation of metal-carbon nanocomposites based on activated carbon. Polyacrylonitrile is suggested as a precursor for Co, Pd and Ru nanoparticles carbon support which is prepared under IR pyrolysis conditions of a precursor. The first part of the paper is devoted to study activated carbon structural characteristics dependence on activation conditions. In the second part the effect of type of metal introduced in precursor on metal-carbon nanocomposite structural characteristics is shown. Prepared AC and nanocomposite samples are characterized by BET, TEM, SEM and X-ray diffraction.

  16. Slotted Polyimide-Aerogel-Filled-Waveguide Arrays

    NASA Technical Reports Server (NTRS)

    Rodriguez-Solis, Rafael A.; Pacheco, Hector L.; Miranda, Felix A.; Meador, Mary Ann B.

    2013-01-01

    Polyimide aerogels were considered to serve as a filling for millimeter-wave waveguides. While these waveguides present a slightly higher loss than hollow waveguides, they have less losses than Duroid substrate integrated waveguides (less than 0.15 dB at Ka-band, in a 20 mm section), and exhibit an order of magnitude of mass reduction when compared to commercial waveguides. A Ka-band slotted aerogel-filled-waveguide array was designed, which provided the same gain (9 dBi) as its standard waveguide counterpart, and a slotted aerogel-filled-waveguide array using folded-slots was designed for comparison, obtaining a gain of 9 dB and a bandwidth of 590 MHz.

  17. High strength air-dried aerogels

    SciTech Connect

    Coronado, Paul R.; Satcher, Jr., Joe H.

    2012-11-06

    A method for the preparation of high strength air-dried organic aerogels. The method involves the sol-gel polymerization of organic gel precursors, such as resorcinol with formaldehyde (RF) in aqueous solvents with R/C ratios greater than about 1000 and R/F ratios less than about 1:2.1. Using a procedure analogous to the preparation of resorcinol-formaldehyde (RF) aerogels, this approach generates wet gels that can be air dried at ambient temperatures and pressures. The method significantly reduces the time and/or energy required to produce a dried aerogel compared to conventional methods using either supercritical solvent extraction. The air dried gel exhibits typically less than 5% shrinkage.

  18. Activated Carbon Composites for Air Separation

    SciTech Connect

    Baker, Frederick S; Contescu, Cristian I; Tsouris, Costas; Burchell, Timothy D

    2011-09-01

    Coal-derived synthesis gas is a potential major source of hydrogen for fuel cells. Oxygen-blown coal gasification is an efficient approach to achieving the goal of producing hydrogen from coal, but a cost-effective means of enriching O2 concentration in air is required. A key objective of this project is to assess the utility of a system that exploits porous carbon materials and electrical swing adsorption to produce an O2-enriched air stream for coal gasification. As a complement to O2 and N2 adsorption measurements, CO2 was used as a more sensitive probe molecule for the characterization of molecular sieving effects. To further enhance the potential of activated carbon composite materials for air separation, work was implemented on incorporating a novel twist into the system; namely the addition of a magnetic field to influence O2 adsorption, which is accompanied by a transition between the paramagnetic and diamagnetic states. The preliminary findings in this respect are discussed.

  19. Highly porous activated carbons prepared from carbon rich Mongolian anthracite by direct NaOH activation

    NASA Astrophysics Data System (ADS)

    Byamba-Ochir, Narandalai; Shim, Wang Geun; Balathanigaimani, M. S.; Moon, Hee

    2016-08-01

    Highly porous activated carbons (ACs) were prepared from Mongolian raw anthracite (MRA) using sodium hydroxide as an activation agent by varying the mass ratio (powdered MRA/NaOH) as well as the mixing method of chemical agent and powdered MRA. The specific BET surface area and total pore volume of the prepared MRA-based activated carbons (MACs) are in the range of 816-2063 m2/g and of 0.55-1.61 cm3/g, respectively. The pore size distribution of MACs show that most of the pores are in the range from large micropores to small mesopores and their distribution can be controlled by the mass ratio and mixing method of the activating agent. As expected from the intrinsic property of the MRA, the highly graphitic surface morphology of prepared carbons was confirmed from Raman spectra and transmission electron microscopy (TEM) studies. Furthermore the FTIR and XPS results reveal that the preparation of MACs with hydrophobic in nature is highly possible by controlling the mixing conditions of activating agent and powdered MRA. Based on all the results, it is suggested that the prepared MACs could be used for many specific applications, requiring high surface area, optimal pore size distribution, proper surface hydrophobicity as well as strong physical strength.

  20. Characterization of Activated Carbons from Oil-Palm Shell by CO2 Activation with No Holding Carbonization Temperature

    PubMed Central

    Herawan, S. G.; Hadi, M. S.; Ayob, Md. R.; Putra, A.

    2013-01-01

    Activated carbons can be produced from different precursors, including coals of different ranks, and lignocellulosic materials, by physical or chemical activation processes. The objective of this paper is to characterize oil-palm shells, as a biomass byproduct from palm-oil mills which were converted into activated carbons by nitrogen pyrolysis followed by CO2 activation. The effects of no holding peak pyrolysis temperature on the physical characteristics of the activated carbons are studied. The BET surface area of the activated carbon is investigated using N2 adsorption at 77 K with selected temperatures of 500, 600, and 700°C. These pyrolysis conditions for preparing the activated carbons are found to yield higher BET surface area at a pyrolysis temperature of 700°C compared to selected commercial activated carbon. The activated carbons thus result in well-developed porosities and predominantly microporosities. By using this activation method, significant improvement can be obtained in the surface characteristics of the activated carbons. Thus this study shows that the preparation time can be shortened while better results of activated carbon can be produced. PMID:23737721

  1. Homogeneity and elemental distribution in self-assembled bimetallic Pd-Pt aerogels prepared by a spontaneous one-step gelation process.

    PubMed

    Oezaslan, M; Liu, W; Nachtegaal, M; Frenkel, A I; Rutkowski, B; Werheid, M; Herrmann, A-K; Laugier-Bonnaud, C; Yilmaz, H-C; Gaponik, N; Czyrska-Filemonowicz, A; Eychmüller, A; Schmidt, T J

    2016-07-27

    Multi-metallic aerogels have recently emerged as a novel and promising class of unsupported electrocatalyst materials due to their high catalytic activity and improved durability for various electrochemical reactions. Aerogels can be prepared by a spontaneous one-step gelation process, where the chemical co-reduction of metal precursors and the prompt formation of nanochain-containing hydrogels, as a preliminary stage for the preparation of aerogels, take place. However, detailed knowledge about the homogeneity and chemical distribution of these three-dimensional Pd-Pt aerogels at the nano-scale as well as at the macro-scale is still unclear. Therefore, we used a combination of spectroscopic and microscopic techniques to obtain a better insight into the structure and elemental distribution of the various Pd-rich Pd-Pt aerogels prepared by the spontaneous one-step gelation process. Synchrotron-based extended X-ray absorption fine structure (EXAFS) spectroscopy and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDX) were employed in this work to uncover the structural architecture and chemical composition of the various Pd-rich Pd-Pt aerogels over a broad length range. The Pd80Pt20, Pd60Pt40 and Pd50Pt50 aerogels showed heterogeneity in the chemical distribution of the Pt and Pd atoms inside the macroscopic nanochain-network. The features of mono-metallic clusters were not detected by EXAFS or STEM-EDX, indicating alloyed nanoparticles. However, the local chemical composition of the Pd-Pt alloys strongly varied along the nanochains and thus within a single aerogel. To determine the electrochemically active surface area (ECSA) of the Pd-Pt aerogels for application in electrocatalysis, we used the electrochemical CO stripping method. Due to their high porosity and extended network structure, the resulting values of the ECSA for the Pd-Pt aerogels were higher than that for

  2. Record Methane Storage in Monolithic and Powdered Activated Carbons

    NASA Astrophysics Data System (ADS)

    Soo, Yuchoong; Nordwald, E.; Hester, B.; Romanos, J.; Isaacson, B.; Stalla, D.; Moore, D.; Kraus, M.; Burress, J.; Dohnke, E.; Pfeifer, P.

    2010-03-01

    The Alliance for Collaborative Research in Alternative Fuel Technology (ALL-CRAFT) has developed activated carbons from corn cob as adsorbent materials for methane gas storage by physisorption at low pressures. KOH activated carbons were compressed into carbon monolith using chemical binders. High pressure methane isotherms up to 250 bar at room temperature on monolithic and powdered activated carbons were measured gravimetrically and volumetrically. Record methane storage capacities of 250 g CH4/kg carbon and 130 g CH4/liter carbon at 35 bar and 293 K have been achieved. BET surface area, porosity, and pore size distributions were measured from sub-critical nitrogen isotherms. Pore entrances were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A prototype adsorbed natural gas (ANG) tank, loaded with carbon monoliths, was tested in Kansas City.

  3. Synthesis of fluorescent carbon nanoparticles directly from active carbon via a one-step ultrasonic treatment

    SciTech Connect

    Li, Haitao; He, Xiaodie; Liu, Yang; Yu, Hang; Kang, Zhenhui; Lee, Shuit-Tong

    2011-01-15

    Water-soluble fluorescent carbon nanoparticles were synthesized directly from active carbon by a one-step hydrogen peroxide-assisted ultrasonic treatment. The carbon nanoparticles were characterized by transmission electron microscopy, optical fluorescent microscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometer. The results showed that the surface of carbon nanoparticles was rich of hydroxyl groups resulting in high hydrophilicity. The carbon nanoparticles could emit bright and colorful photoluminescence covering the entire visible-to-near infrared spectral range. Furthermore, these carbon nanoparticles also had excellent up-conversion fluorescent properties.

  4. An emerging platform for drug delivery: aerogel based systems.

    PubMed

    Ulker, Zeynep; Erkey, Can

    2014-03-10

    Over the past few decades, advances in "aerogel science" have provoked an increasing interest for these materials in pharmaceutical sciences for drug delivery applications. Because of their high surface areas, high porosities and open pore structures which can be tuned and controlled by manipulation of synthesis conditions, nanostructured aerogels represent a promising class of materials for delivery of various drugs as well as enzymes and proteins. Along with biocompatible inorganic aerogels and biodegradable organic aerogels, more complex systems such as surface functionalized aerogels, composite aerogels and layered aerogels have also been under development and possess huge potential. Emphasis is given to the details of the aerogel synthesis and drug loading methods as well as the influence of synthesis parameters and loading methods on the adsorption and release of the drugs. Owing to their ability to increase the bioavailability of low solubility drugs, to improve both their stability and their release kinetics, there are an increasing number of research articles concerning aerogels in different drug delivery applications. This review presents an up to date overview of the advances in all kinds of aerogel based drug delivery systems which are currently under investigation.

  5. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  6. [Effects of different fertilizer application on soil active organic carbon].

    PubMed

    Zhang, Rui; Zhang, Gui-Long; Ji, Yan-Yan; Li, Gang; Chang, Hong; Yang, Dian-Lin

    2013-01-01

    The variation characteristics of the content and components of soil active organic carbon under different fertilizer application were investigated in samples of calcareous fluvo-aquic soil from a field experiment growing winter wheat and summer maize in rotation in the North China Plain. The results showed that RF (recommended fertilization), CF (conventional fertilization) and NPK (mineral fertilizer alone) significantly increased the content of soil dissolved organic carbon and easily oxidized organic carbon by 24.92-38.63 mg x kg(-1) and 0.94-0.58 mg x kg(-1) respectively compared to CK (unfertilized control). The soil dissolved organic carbon content under OM (organic manure) increased greater than those under NPK and single fertilization, soil easily oxidized organic carbon content under OM and NPK increased greater than that under single chemical fertilization. OM and NPK showed no significant role in promoting the soil microbial biomass carbon, but combined application of OM and NPK significantly increased the soil microbial biomass carbon content by 36.06% and 20.69%, respectively. Soil easily oxidized organic carbon, dissolved organic carbon and microbial biomass carbon accounted for 8.41% - 14.83%, 0.47% - 0.70% and 0.89% - 1.20% of the total organic carbon (TOC), respectively. According to the results, the fertilizer application significantly increased the proportion of soil dissolved organic carbon and easily oxidized organic carbon, but there was no significant difference in the increasing extent of dissolved organic carbon. The RF and CF increased the proportion of soil easily oxidized organic carbon greater than OM or NPK, and significantly increased the proportion of microbial biomass carbon. OM or RF had no significant effect on the proportion of microbial biomass carbon. Therefore, in the field experiment, appropriate application of organic manure and chemical fertilizers played an important role for the increase of soil active organic carbon

  7. Manufacturing complex silica aerogel target components

    SciTech Connect

    Defriend Obrey, Kimberly Ann; Day, Robert D; Espinoza, Brent F; Hatch, Doug; Patterson, Brian M; Feng, Shihai

    2008-01-01

    Aerogel is a material used in numerous components in High Energy Density Physics targets. In the past these components were molded into the proper shapes. Artifacts left in the parts from the molding process, such as contour irregularities from shrinkage and density gradients caused by the skin, have caused LANL to pursue machining as a way to make the components.

  8. Lightweight and thermally insulating aerogel glass materials

    NASA Astrophysics Data System (ADS)

    Gao, Tao; Jelle, Bjørn Petter; Gustavsen, Arild; He, Jianying

    2014-07-01

    Glass represents an important and widely used building material, and crucial aspects to be addressed include thermal conductivity, visible light transmittance, and weight for windows with improved energy efficiency. In this work, by sintering monolithic silica aerogel precursors at elevated temperatures, aerogel glass materials were successfully prepared, which were characterized by low thermal conductivity [k ≈ 0.17-0.18 W/(mK)], high visible transparency (T vis ≈ 91-96 % at 500 nm), low density (ρ ≈ 1.60-1.79 g/cm3), and enhanced mechanical strength (typical elastic modulus E r ≈ 2.0-6.4 GPa). These improved properties were derived from a series of successive gelation and aging steps during the desiccation of silica aerogels. The involved sol → gel → glass transformation was investigated by means of thermo-gravimetric analysis, scanning electron microscopy, nanoindentation, and Fourier transform infrared spectroscopy. Strategies of improving further the mechanical strength of the obtained aerogel glass materials are also discussed.

  9. Aerogel insulation systems for space launch applications

    NASA Astrophysics Data System (ADS)

    Fesmire, J. E.

    2006-02-01

    New developments in materials science in the areas of solution gelation processes and nanotechnology have led to the recent commercial production of aerogels. Concurrent with these advancements has been the development of new approaches to cryogenic thermal insulation systems. For example, thermal and physical characterizations of aerogel beads under cryogenic-vacuum conditions have been performed at the Cryogenics Test Laboratory of the NASA Kennedy Space Center. Aerogel-based insulation system demonstrations have also been conducted to improve performance for space launch applications. Subscale cryopumping experiments show the thermal insulating ability of these fully breathable nanoporous materials. For a properly executed thermal insulation system, these breathable aerogel systems are shown to not cryopump beyond the initial cooldown and thermal stabilization phase. New applications are being developed to augment the thermal protection systems of space launch vehicles, including the Space Shuttle External Tank. These applications include a cold-boundary temperature of 90 K with an ambient air environment in which both weather and flight aerodynamics are important considerations. Another application is a nitrogen-purged environment with a cold-boundary temperature of 20 K where both initial cooldown and launch ascent profiles must be considered. Experimental results and considerations for these flight system applications are discussed.

  10. Aerogel Insulation Systems for Space Launch Applications

    NASA Technical Reports Server (NTRS)

    Fesmire, James E.

    2005-01-01

    New developments in materials science in the areas of solution gelation processes and nanotechnology have led to the recent commercial production of aerogels. Concurrent with these advancements has been the development of new approaches to cryogenic thermal insulation systems. For example, thermal and physical characterizations of aerogel beads under cryogenic-vacuum conditions have been performed at the Cryogenics Test Laboratory of the NASA Kennedy Space Center. Aerogel-based insulation system demonstrations have also been conducted to improve performance for space launch applications. Subscale cryopumping experiments show the thermal insulating ability of these fully breathable nanoporous materials. For a properly executed thermal insulation system, these breathable aerogel systems are shown to not cryopump beyond the initial cooldown and thermal stabilization phase. New applications are being developed to augment the thermal protection systems of space launch vehicles, including the Space Shuttle External Tank. These applications include a cold-boundary temperature of 90 K with an ambient air environment in which both weather and flight aerodynamics are important considerations. Another application is a nitrogen-purged environment with a cold-boundary temperature of 20 K where both initial cooldown and launch ascent profiles must be considered. Experimental results and considerations for these flight system applications are discussed.

  11. Mechanically Robust Polymer-Graphene Aerogels

    NASA Astrophysics Data System (ADS)

    Ha, Heonjoo; Shanmuganathan, Kadhiravan; Ellison, Christopher

    2015-03-01

    Graphene has been intensely studied for the past several years due to its many attractive properties. Graphene oxide (GO) aerogels are particularly interesting due to their light weight and excellent performance in various applications, such as environmental remediation, super-hydrophobic and super-oleophilic materials, energy storage, etc. However, GO aerogels are generally weak and delicate which complicates their handling and potentially limits their application outside the research lab. The focus of this work is to synthesize mechanically stable aerogels that are robust and easy to handle without substantially sacrificing their low density. To overcome this challenge, we found that by intermixing a small amount of readily available and thermally crosslinkable polymer can enhance the mechanical properties without disrupting other characteristic intrinsic properties of the aerogel itself. This method is a simple straight-forward procedure that does not include any tedious chemical reactions or harsh chemicals. Furthermore, we will demonstrate the performance of these materials as a super-absorbent and pressure sensor.

  12. View of a Cometary Impact Into Aerogel

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Closeup view of a cometary impact (upper right) into aerogel was inspected by scientists at a laboratory at the Johnson Space Center hours after the Stardust Sample Return Canister was delivered to the Johnson Space Center from the spacecraft's landing site in Utah.

  13. JPL Activated Carbon Treatment System (ACTS) for sewage

    NASA Technical Reports Server (NTRS)

    1976-01-01

    An Activated Carbon Treatment System (ACTS) was developed for sewage treatment and is being applied to a one-million gallon per day sewage treatment pilot plant in Orange County California. Activities reported include pyrolysis and activation of carbon-sewage sludge, and activated carbon treatment of sewage to meet ocean discharge standards. The ACTS Sewage treatment operations include carbon-sewage treatment, primary and secondary clarifiers, gravity (multi-media) filter, filter press dewatering, flash drying of carbon-sewage filter cake, and sludge pyrolysis and activation. Tests were conducted on a laboratory scale, 10,000 gallon per day demonstration plant and pilot test equipment. Preliminary economic studies are favorable to the ACTS process relative to activated sludge treatment for a 175,000,000 gallon per day sewage treatment plant.

  14. Activated Carbon Modified with Copper for Adsorption of Propanethiol

    PubMed Central

    Moreno-Piraján, Juan Carlos; Tirano, Joaquín; Salamanca, Brisa; Giraldo, Liliana

    2010-01-01

    Activated carbons were characterized texturally and chemically before and after treatment, using surface area determination in the BET model, Boehm titration, TPR, DRX and immersion calorimetry. The adsorption capacity and the kinetics of sulphur compound removal were determined by gas chromatography. It was established that the propanethiol retention capacity is dependent on the number of oxygenated groups generated on the activated carbon surface and that activated carbon modified with CuO at 0.25 M shows the highest retention of propanethiol. Additionally is proposed a mechanism of decomposition of propenothiol with carbon-copper system. PMID:20479992

  15. Composite carbon foam electrode

    DOEpatents

    Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

    1997-05-06

    Carbon aerogels used as a binder for granulated materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivity and power to system energy. 1 fig.

  16. Composite carbon foam electrode

    DOEpatents

    Mayer, Steven T.; Pekala, Richard W.; Kaschmitter, James L.

    1997-01-01

    Carbon aerogels used as a binder for granularized materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivty and power to system energy.

  17. Characteristics of Cometary Dust Tracks in Stardust Aerogel and Laboratory Calibrations

    NASA Technical Reports Server (NTRS)

    Burchell, M. J.; Fairey, S. A. J.; Wozniakiewicz, P.; Brownlee, D. E.; Hoerz, F.; Kearsley, A. T.; See, T. H.; Tsou, P.; Westphal, A.; Green, S. F.; Trigo-Rodriguez, J. M.; Dominguez, G.

    2007-01-01

    The cometary tray of the NASA Stardust spacecraft s aerogel collector has been examined to study the dust that was captured during the 2004 fly by of comet 81P/Wild-2. An optical scan of the entire collector surface revealed 256 impact features in the aerogel (width > 100 microns). 20 aerogel blocks (out of a total of 132) were removed from the collector tray for a higher resolution optical scan and 186 tracks were observed (track length > 50 microns and width > 8 microns). The impact features were classified into three types based on their morphology. Laboratory calibrations were conducted which reproduce all three types. This work suggests that the cometary dust consisted of some cohesive, relatively strong particles as well as particles with a more friable or low cohesion matrix containing smaller strong grains. The calibrations also permitted a particle size distribution to be estimated for the cometary dust. We estimate that approximately 1200 particles bigger than 1 micron struck the aerogel. The cumulative size distribution of the captured particles was obtained and compared with observations made by active dust detectors during the encounter. At large sizes (>20 microns) all measures of the dust are compatible, but at micrometer scales and smaller discrepancies exist between the various measurement systems which may reflect structure in the dust flux (streams, clusters etc.) along with some possible instrument effects.

  18. Surface-Functionalization of Nanostructured Cellulose Aerogels by Solid State Eumelanin Coating.

    PubMed

    Panzella, Lucia; Melone, Lucio; Pezzella, Alessandro; Rossi, Bianca; Pastori, Nadia; Perfetti, Marco; D'Errico, Gerardino; Punta, Carlo; d'Ischia, Marco

    2016-02-01

    Bioinspired aerogel functionalization by surface modification and coating is in high demand for biomedical and technological applications. In this paper, we report an expedient three-step entry to all-natural surface-functionalized nanostructured aerogels based on (a) TEMPO/NaClO promoted synthesis of cellulose nanofibers (TOCNF); (b) freeze-drying for aerogel preparation; and (c) surface coating with a eumelanin thin film by ammonia-induced solid state polymerization (AISSP) of 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA) previously deposited from an organic solution. Scanning electron microscopy showed uniform deposition of the dark eumelanin coating on the template surface without affecting porosity, whereas solid state (13)C NMR and electron paramagnetic resonance (EPR) spectroscopy confirmed the eumelanin-type character of the coatings. DHI melanin coating was found to confer to TOCNF templates a potent antioxidant activity, as tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays as well as strong dye adsorption capacity, as tested on methylene blue. The unprecedented combination of nanostructured cellulose and eumelanin thin films disclosed herein implements an original all-natural multifunctional aerogel biomaterial realized via an innovative coating methodology.

  19. Surface-Functionalization of Nanostructured Cellulose Aerogels by Solid State Eumelanin Coating.

    PubMed

    Panzella, Lucia; Melone, Lucio; Pezzella, Alessandro; Rossi, Bianca; Pastori, Nadia; Perfetti, Marco; D'Errico, Gerardino; Punta, Carlo; d'Ischia, Marco

    2016-02-01

    Bioinspired aerogel functionalization by surface modification and coating is in high demand for biomedical and technological applications. In this paper, we report an expedient three-step entry to all-natural surface-functionalized nanostructured aerogels based on (a) TEMPO/NaClO promoted synthesis of cellulose nanofibers (TOCNF); (b) freeze-drying for aerogel preparation; and (c) surface coating with a eumelanin thin film by ammonia-induced solid state polymerization (AISSP) of 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA) previously deposited from an organic solution. Scanning electron microscopy showed uniform deposition of the dark eumelanin coating on the template surface without affecting porosity, whereas solid state (13)C NMR and electron paramagnetic resonance (EPR) spectroscopy confirmed the eumelanin-type character of the coatings. DHI melanin coating was found to confer to TOCNF templates a potent antioxidant activity, as tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays as well as strong dye adsorption capacity, as tested on methylene blue. The unprecedented combination of nanostructured cellulose and eumelanin thin films disclosed herein implements an original all-natural multifunctional aerogel biomaterial realized via an innovative coating methodology. PMID:26734842

  20. Synthesis of Yttria-Stabilized Zirconia Aerogels by a Non-Alkoxide Sol-Gel Route

    SciTech Connect

    Chervin, C N; Clapsaddle, B J; Chiu, H W; Gash, A E; Satcher, Jr., J H; Kauzlarich, S M

    2005-02-11

    Homogeneous, nanocrystalline powders of yttria-stabilized zirconia were prepared using a nonalkoxide sol-gel method. Monolithic gels, free of precipitation, were prepared by addition of propylene oxide to aqueous solutions of Zr{sup 4+} and Y{sup 3+} chlorides at room temperature. The gels were dried with supercritical CO{sub 2}(l), resulting in amorphous aerogels that crystallized into cubic stabilized ZrO{sub 2} following calcination at 500 C. The aerogels and resulting crystalline products were characterized using in-situ temperature profile X-ray diffraction, thermal analysis, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and nitrogen adsorption/desorption analysis. TEM and N{sub 2} adsorption/desorption analysis of an aerogel indicated a porous network structure with a high surface area (409 m{sup 2}/g). The crystallized yttria-stabilized zirconia maintained high surface area (159 m{sup 2}/g) upon formation of homogeneous, nanoparticles ({approx}10 nm). Ionic conductivity at 1000 C of sintered YSZ (1500 C, 3 hours) prepared by this method, was 0.13 {+-} 0.02 {Omega}{sup -1} cm{sup -1}. Activation energies for the conduction processes from 1000-550 C and 550-400 C, were 0.95 {+-} 0.09 and 1.12 {+-} 0.05 eV, respectively. This is the first reported synthesis and characterization of yttria-stabilized zirconia via an aerogel precursor.

  1. Preparation of nitrogen-enriched activated carbons from brown coal

    SciTech Connect

    Robert Pietrzak; Helena Wachowska; Piotr Nowicki

    2006-05-15

    Nitrogen-enriched activated carbons were prepared from a Polish brown coal. Nitrogen was introduced from urea at 350{sup o}C in an oxidizing atmosphere both to carbonizates obtained at 500-700{sup o}C and to activated carbons prepared from them. The activation was performed at 800{sup o}C with KOH in argon. It has been observed that the carbonization temperature determines the amount of nitrogen that is incorporated (DC5U, 8.4 wt % N{sup daf}; DC6U, 6.3 wt % N{sup daf}; and DC7U, 5.4 wt % N{sup daf}). X-ray photoelectron spectroscopy (XPS) measurements have shown that nitrogen introduced both at the stage of carbonizates and at the stage of activated carbons occurs mainly as -6, -5, and imine, amine and amide groups. On the other hand, the activation of carbons enriched with nitrogen results in the formation of pyridonic nitrogen and N-Q. The introduction of nitrogen at the activated carbon stage leads to a slight decrease in surface area. It has been proven that the most effective way of preparing microporous activated carbons enriched with nitrogen to a considerable extent and having high surface area ({approximately} 3000 m{sup 2}/g) is the following: carbonization - activation - reaction with urea. 40 refs., 1 fig., 6 tabs.

  2. Acoustical Evaluation of Carbonized and Activated Cotton Nonwovens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The process of manufacturing a carbonized and activated nonwoven made by cotton fiber was investigated in this paper. The study was focused on the acoustic application and nonwoven composites with cotton nonwoven as a base layer and glass fiber nonwoven, cotton nonwoven, and carbonized and activated...

  3. A Magnesium-Activated Carbon Hybrid Capacitor

    SciTech Connect

    Yoo, HD; Shterenberg, I; Gofer, Y; Doe, RE; Fischer, CC; Ceder, G; Aurbach, D

    2013-12-11

    Prototype cells of hybrid capacitor were developed, comprising activated carbon (AC) cloth and magnesium (Mg) foil as the positive and negative electrodes, respectively. The electrolyte solution included ether solvent (TBF) and a magnesium organo-halo-aluminate complex 0.25 M Mg2Cl3+-Ph2AlCl2-. In this solution Mg can be deposited/dissolved reversibly for thousands of cycles with high reversibility (100% cycling efficiency). The main barrier for integrating porous AC electrodes with this electrolyte solution was the saturation of the pores with the large ions in the AC prior to reaching the potential limit. This is due to the existence of bulky Mg and Al based ionic complexes consisting Cl, alkyl or aryl (R), and THF ligands. This problem was resolved by adding 0.5 M of lithium chloride (LiCl), thus introducing smaller ionic species to the solution. This Mg hybrid capacitor system demonstrated a stable cycle performance for many thousands of cycles with a specific capacitance of 90 Fg(-1) for the AC positive electrodes along a potential range of 2.4 V. (C) 2014 The Electrochemical Society. All rights reserved.

  4. Impact of polishing on the light scattering at aerogel surface

    NASA Astrophysics Data System (ADS)

    Barnyakov, A. Yu.; Barnyakov, M. Yu.; Bobrovnikov, V. S.; Buzykaev, A. R.; Danilyuk, A. F.; Katcin, A. A.; Kononov, S. A.; Kirilenko, P. S.; Kravchenko, E. A.; Kuyanov, I. A.; Onuchin, A. P.; Ovtin, I. V.; Predein, A. Yu.; Protsenko, R. S.

    2016-07-01

    Particle identification power of modern aerogel RICH detectors strongly depends on optical quality of radiators. It was shown that wavelength dependence of aerogel tile transparency after polishing cannot be described by the standard Hunt formula. The Hunt formula has been modified to describe scattering in a thin layer of silica dust on the surface of aerogel tile. Several procedures of polishing of aerogel tile have been tested. The best result has been achieved while using natural silk tissue. The resulting block has optical smooth surfaces. The measured decrease of aerogel transparency due to surface scattering is about few percent. This result could be used for production of radiators for the Focusing Aerogel RICH detectors.

  5. Highly compressible 3D periodic graphene aerogel microlattices

    PubMed Central

    Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.

    2015-01-01

    Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications. PMID:25902277

  6. Synthesis and biomedical applications of aerogels: Possibilities and challenges.

    PubMed

    Maleki, Hajar; Durães, Luisa; García-González, Carlos A; Del Gaudio, Pasquale; Portugal, António; Mahmoudi, Morteza

    2016-10-01

    Aerogels are an exceptional group of nanoporous materials with outstanding physicochemical properties. Due to their unique physical, chemical, and mechanical properties, aerogels are recognized as promising candidates for diverse applications including, thermal insulation, catalysis, environmental cleaning up, chemical sensors, acoustic transducers, energy storage devices, metal casting molds and water repellant coatings. Here, we have provided a comprehensive overview on the synthesis, processing and drying methods of the mostly investigated types of aerogels used in the biological and biomedical contexts, including silica aerogels, silica-polymer composites, polymeric and biopolymer aerogels. In addition, the very recent challenges on these aerogels with regard to their applicability in biomedical field as well as for personalized medicine applications are considered and explained in detail.

  7. Evaluating Dimethyldiethoxysilane for use in Polyurethane Crosslinked Silica Aerogels

    NASA Technical Reports Server (NTRS)

    Randall, Jason P.; Meador, Mary Ann B.; Jana, Sadhan C.

    2008-01-01

    Silica aerogels are highly porous materials which exhibit exceptionally low density and thermal conductivity. Their "pearl necklace" nanostructure, however, is inherently weak; most silica aerogels are brittle and fragile. The strength of aerogels can be improved by employing an additional crosslinking step using isocyanates. In this work, dimethyldiethoxysilane (DMDES) is evaluated for use in the silane backbone of polyurethane crosslinked aerogels. Approximately half of the resulting aerogels exhibited a core/shell morphology of hard crosslinked aerogel surrounding a softer, uncrosslinked center. Solid state NMR and scanning electron microscopy results indicate the DMDES incorporated itself as a conformal coating around the outside of the secondary silica particles, in much the same manner as isocyanate crosslinking. Response surface curves were generated from compression data, indicating levels of reinforcement comparable to that in previous literature, despite the core/shell morphology.

  8. Highly compressible 3D periodic graphene aerogel microlattices

    SciTech Connect

    Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.

    2015-04-22

    Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young’s moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Ultimately, adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.

  9. Synthesis and biomedical applications of aerogels: Possibilities and challenges.

    PubMed

    Maleki, Hajar; Durães, Luisa; García-González, Carlos A; Del Gaudio, Pasquale; Portugal, António; Mahmoudi, Morteza

    2016-10-01

    Aerogels are an exceptional group of nanoporous materials with outstanding physicochemical properties. Due to their unique physical, chemical, and mechanical properties, aerogels are recognized as promising candidates for diverse applications including, thermal insulation, catalysis, environmental cleaning up, chemical sensors, acoustic transducers, energy storage devices, metal casting molds and water repellant coatings. Here, we have provided a comprehensive overview on the synthesis, processing and drying methods of the mostly investigated types of aerogels used in the biological and biomedical contexts, including silica aerogels, silica-polymer composites, polymeric and biopolymer aerogels. In addition, the very recent challenges on these aerogels with regard to their applicability in biomedical field as well as for personalized medicine applications are considered and explained in detail. PMID:27321857

  10. Highly compressible 3D periodic graphene aerogel microlattices.

    PubMed

    Zhu, Cheng; Han, T Yong-Jin; Duoss, Eric B; Golobic, Alexandra M; Kuntz, Joshua D; Spadaccini, Christopher M; Worsley, Marcus A

    2015-04-22

    Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.

  11. Highly compressible 3D periodic graphene aerogel microlattices

    NASA Astrophysics Data System (ADS)

    Zhu, Cheng; Han, T. Yong-Jin; Duoss, Eric B.; Golobic, Alexandra M.; Kuntz, Joshua D.; Spadaccini, Christopher M.; Worsley, Marcus A.

    2015-04-01

    Graphene is a two-dimensional material that offers a unique combination of low density, exceptional mechanical properties, large surface area and excellent electrical conductivity. Recent progress has produced bulk 3D assemblies of graphene, such as graphene aerogels, but they possess purely stochastic porous networks, which limit their performance compared with the potential of an engineered architecture. Here we report the fabrication of periodic graphene aerogel microlattices, possessing an engineered architecture via a 3D printing technique known as direct ink writing. The 3D printed graphene aerogels are lightweight, highly conductive and exhibit supercompressibility (up to 90% compressive strain). Moreover, the Young's moduli of the 3D printed graphene aerogels show an order of magnitude improvement over bulk graphene materials with comparable geometric density and possess large surface areas. Adapting the 3D printing technique to graphene aerogels realizes the possibility of fabricating a myriad of complex aerogel architectures for a broad range of applications.

  12. Microbial Enzyme Activity and Carbon Cycling in Grassland Soil Fractions

    NASA Astrophysics Data System (ADS)

    Allison, S. D.; Jastrow, J. D.

    2004-12-01

    Extracellular enzymes are necessary to degrade complex organic compounds present in soils. Using physical fractionation procedures, we tested whether old soil carbon is spatially isolated from degradative enzymes across a prairie restoration chronosequence in Illinois, USA. We found that carbon-degrading enzymes were abundant in all soil fractions, including macroaggregates, microaggregates, and the clay fraction, which contains carbon with a mean residence time of ~200 years. The activities of two cellulose-degrading enzymes and a chitin-degrading enzyme were 2-10 times greater in organic matter fractions than in bulk soil, consistent with the rapid turnover of these fractions. Polyphenol oxidase activity was 3 times greater in the clay fraction than in the bulk soil, despite very slow carbon turnover in this fraction. Changes in enzyme activity across the restoration chronosequence were small once adjusted for increases in soil carbon concentration, although polyphenol oxidase activity per unit carbon declined by 50% in native prairie versus cultivated soil. These results are consistent with a `two-pool' model of enzyme and carbon turnover in grassland soils. In light organic matter fractions, enzyme production and carbon turnover both occur rapidly. However, in mineral-dominated fractions, both enzymes and their carbon substrates are immobilized on mineral surfaces, leading to slow turnover. Soil carbon accumulation in the clay fraction and across the prairie restoration chronosequence probably reflects increasing physical isolation of enzymes and substrates on the molecular scale, rather than the micron to millimeter scale.

  13. Ozone Removal by Filters Containing Activated Carbon: A Pilot Study

    SciTech Connect

    Fisk, William; Spears, Mike; Sullivan, Douglas; Mendell, Mark

    2009-09-01

    This study evaluated the ozone removal performance of moderate-cost particle filters containing activated carbon when installed in a commercial building heating, ventilating, and air conditioning (HVAC) system. Filters containing 300 g of activated carbon per 0.09 m2 of filter face area were installed in two 'experimental' filter banks within an office building located in Sacramento, CA. The ozone removal performance of the filters was assessed through periodic measurements of ozone concentrations in the air upstream and downstream of the filters. Ozone concentrations were also measured upstream and downstream of a 'reference' filter bank containing filters without any activated carbon. The filter banks with prefilters containing activated carbon were removing 60percent to 70percent of the ozone 67 and 81 days after filter installation. In contrast, there was negligible ozone removal by the reference filter bank without activated carbon.

  14. Deep Bed Adsorption Testing using Silver-Functionalized Aerogel

    SciTech Connect

    Nick Soelberg; Tony Watson

    2012-06-01

    Nuclear fission results in the production of fission products and activation products, some of which tend to be volatile during used fuel reprocessing and evolve in gaseous species into the reprocessing facility off-gas systems. Analyses have shown that I129, due to its radioactivity, high potential mobility in the environment, and high longevity (half life of 15.7 million years), can require control efficiencies of up to 1,000x or higher to meet regulatory emission limits. Two Aerogel sorption tests that have been performed this fiscal year. The maximum iodine decontamination factor (DF) was measured to be over 10,000, above the 1,000-10,000 target DF range. The mass transfer zone may be as short as 0.5 inches under the sorption conditions of the first test. Only a small fraction of the iodine sorbed on Bed 1 was desorbed during the purge periods. The silver-functionalized Aerogel appears to have potential to be a very effective and efficient iodine sorbent.

  15. Uncooled thin film pyroelectric IR detector with aerogel thermal isolation

    SciTech Connect

    Ruffner, J.A.; Clem, P.G.; Tuttle, B.A.

    1998-01-01

    Uncooled pyroelectric IR imaging systems, such as night vision goggles, offer important strategic advantages in battlefield scenarios and reconnaissance surveys. Until now, the current technology for fabricating these devices has been limited by low throughput and high cost which ultimately limit the availability of these sensor devices. We have developed and fabricated an alternative design for pyroelectric IR imaging sensors that utilizes a multilayered thin film deposition scheme to create a monolithic thin film imaging element on an active silicon substrate for the first time. This approach combines a thin film pyroelectric imaging element with a thermally insulating SiO{sub 2} aerogel thin film to produce a new type of uncooled IR sensor that offers significantly higher thermal, spatial, and temporal resolutions at a substantially lower cost per unit. This report describes the deposition, characterization and optimization of the aerogel thermal isolation layer and an appropriate pyroelectric imaging element. It also describes the overall integration of these components along with the appropriate planarization, etch stop, adhesion, electrode, and blacking agent thin film layers into a monolithic structure. 19 refs., 8 figs., 6 tabs.

  16. Fractal analysis of granular activated carbons using isotherm data

    SciTech Connect

    Khalili, N.R.; Pan, M.; Sandi, G.

    1997-08-01

    Utilization of adsorption on solid surfaces was exercised for the first time in 1785. Practical application of unactivated carbon filters, and powdered carbon were first demonstrated in the American water treatment plant, and a municipal treatment plant in New Jersey, in 1883 and 1930, respectively. The use of activated carbon became widespread in the next few decades. At present, adsorption on carbons has a wide spread application in water treatment and removal of taste, odor, removal of synthetic organic chemicals, color-forming organics, and desinfection by-products and their naturally occurring precursors. This paper presents an analysis of the surface fractal dimension and adsorption capacity of a group of carbons.

  17. Mesoporous polyurethane aerogels for thermal superinsulation: Textural properties and thermal conductivity

    NASA Astrophysics Data System (ADS)

    Diascorn, N.; Sallee, H.; Calas, S.; Rigacci, A.; Achard, P.

    2015-07-01

    Organic aerogels based on polyurethane were elaborated via sol-gel synthesis and dried with supercritical carbon dioxide (CO2). The influence of the catalyst concentration was investigated, first in order to decrease the reaction kinetics, then to study its impact on the obtained materials properties. It was shown that this parameter also influences the global shrinkage and the bulk density of the resulting materials. Its effect on the dry materials was studied in terms of morphological, textural and thermal properties in order to determine the main correlations thanks to scanning electron microscopy (SEM), nitrogen adsorption, non-intrusive mercury porosimetry and thermal conductivity measurements. Results allowed us to demonstrate a correlation between the bulk density, the texture and the thermal conductivity of this family of polyurethane aerogels and to determine an optimal density range for thermal performance associated with a fine internal mesoporous texture.

  18. Selecting activated carbon for water and wastewater treatability studies

    SciTech Connect

    Zhang, W.; Chang, Q.G.; Liu, W.D.; Li, B.J.; Jiang, W.X.; Fu, L.J.; Ying, W.C.

    2007-10-15

    A series of follow-up investigations were performed to produce data for improving the four-indicator carbon selection method that we developed to identify high-potential activated carbons effective for removing specific organic water pollutants. The carbon's pore structure and surface chemistry are dependent on the raw material and the activation process. Coconut carbons have relatively more small pores than large pores; coal and apricot nutshell/walnut shell fruit carbons have the desirable pore structures for removing adsorbates of all sizes. Chemical activation, excessive activation, and/or thermal reactivation enlarge small pores, resulting in reduced phenol number and higher tannic acid number. Activated carbon's phenol, iodine, methylene blue, and tannic acid numbers are convenient indicators of its surface area and pore volume of pore diameters < 10, 10-15, 15-28, and > 28 angstrom, respectively. The phenol number of a carbon is also a good indicator of its surface acidity of oxygen-containing organic functional groups that affect the adsorptive capacity for aromatic and other small polar organics. The tannic acid number is an indicator of carbon's capacity for large, high-molecular-weight natural organic precursors of disinfection by-products in water treatment. The experimental results for removing nitrobenzene, methyl-tert-butyl ether, 4,4-bisphenol, humic acid, and the organic constituents of a biologically treated coking-plant effluent have demonstrated the effectiveness of this capacity-indicator-based method of carbon selection.

  19. Observation of viscoelasticity in boron nitride nanosheet aerogel.

    PubMed

    Zeng, Xiaoliang; Ye, Lei; Sun, Rong; Xu, Jianbin; Wong, Ching-Ping

    2015-07-14

    The viscoelasticity of boron nitride nanosheet (BNNS) aerogel has been observed and investigated. It is found that the BNNS aerogel has a high damping ratio (0.2), while it exhibits lightweight and negligible temperature dependence below 180 °C. The creep behavior of the BNNS aerogel markedly demonstrates its strain dependence on stress magnitude and temperature, and can be well simulated by the classical models.

  20. Preparation and characterization of activated carbon produced from pomegranate seeds by ZnCl 2 activation

    NASA Astrophysics Data System (ADS)

    Uçar, Suat; Erdem, Murat; Tay, Turgay; Karagöz, Selhan

    2009-08-01

    In this study, pomegranate seeds, a by-product of fruit juice industry, were used as precursor for the preparation of activated carbon by chemical activation with ZnCl 2. The influence of process variables such as the carbonization temperature and the impregnation ratio on textural and chemical-surface properties of the activated carbons was studied. When using the 2.0 impregnation ratio at the carbonization temperature of 600 °C, the specific surface area of the resultant carbon is as high as 978.8 m 2 g -1. The results showed that the surface area and total pore volume of the activated carbons at the lowest impregnation ratio and the carbonization temperature were achieved as high as 709.4 m 2 g -1 and 0.329 cm 3 g -1. The surface area was strongly influenced by the impregnation ratio of activation reagent and the subsequent carbonization temperature.

  1. Thio-,amine-,nitro-,and macrocyclic containing organic aerogels & xerogels

    DOEpatents

    Fox, Glenn A.; Tillotson, Thomas M.

    2005-08-02

    An organic aerogel or xerogel formed by a sol-gel reaction using starting materials that exhibit similar reactivity to the most commonly used resorcinol starting material. The new starting materials, including thio-, amine- and nitro-containing molecules and functionalized macrocyclic molecules will produce organic xerogels and aerogels that have improved performance in the areas of detection and sensor technology, as well as water stream remediation. Also, further functionalization of these new organic aerogels or xerogels will yield material that can be extracted with greater facility than current organic aerogels.

  2. Aerogel Materials by Evaporative Drying: Potential for Space Applications

    NASA Technical Reports Server (NTRS)

    Plawsky, Joel L.

    1999-01-01

    Aerogel wafers were made using an evaporative drying procedure. The main steps were sol formulation, gelation, aging, capping, and drying. Of these, the most critical step was drying. Both the rate of evaporation and temperature of the system must be controlled for best results. Aerogel materials should be benchmarked against more traditional foams and current systems may have to be redesigned to make best use of aerogel strengths. Finally, the flexibility of this procedure lends itself to producing aerogel materials for many uses other than insulation. Such uses may include catalysis, sensing, and composite materials.

  3. Mechanically Strong Lightweight Materials for Aerospace Applications (x-aerogels)

    NASA Technical Reports Server (NTRS)

    Leventis, Nicholas

    2005-01-01

    The X-Aerogel is a new NASA-developed strong lightweight material made by reacting the mesoporous surfaces of 3-D networks of inorganic nanoparticles with polymeric crosslinkers. Since the relative amount of the crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by templated casting of polymeric precursors on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralightweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the thermal conductivity of styrofoam. XAerogels have been demonstrated with several polymers such as polyurethanes/polyureas, epoxies and polyolefins, while crosslinking of approximately 35 different oxide aerogels yields a wide variety of dimensionally stable, porous lightweight materials with interesting structural, magnetic and optical properties. X-Aerogels are evaluated for cryogenic rocket fuel storage tanks and for Advanced EVA suits, where they will play the dual role of the thermal insulator/structural material. Along the same lines, major impact is also expected by the use of X-Aerogels in structural components/thermal protection for small satellites, spacecrafts, planetary vehicles and habitats.

  4. Grain-based activated carbons for natural gas storage.

    PubMed

    Zhang, Tengyan; Walawender, Walter P; Fan, L T

    2010-03-01

    Natural gas has emerged as a potential alternative to gasoline due to the increase in global energy demand and environmental concerns. An investigation was undertaken to explore the technical feasibility of implementing the adsorbed natural gas (ANG) storage in the fuel tanks of motor vehicles with activated carbons from biomass, e.g., sorghum and wheat. The grain-based activated carbons were prepared by chemical activation; the experimental parameters were varied to identify the optimum conditions. The porosity of the resultant activated carbons was evaluated through nitrogen adsorption; and the storage capacity, through methane adsorption. A comparative study was also carried out with commercial activated carbons from charcoal. The highest storage factor attained was 89 for compacted grain-based activated carbons from grain sorghum with a bulk density of 0.65 g/cm(3), and the highest storage factor attained is 106 for compacted commercial activated carbons (Calgon) with a bulk density of 0.70 g/cm(3). The storage factor was found to increase approximately linearly with increasing bulk density and to be independent of the extent of compaction. This implies that the grain-based activated carbons are the ideal candidates for the ANG storage.

  5. Impact of sulfur oxides on mercury capture by activated carbon.

    PubMed

    Presto, Albert A; Granite, Evan J

    2007-09-15

    Recent field tests of mercury removal with activated carbon injection (ACI) have revealed that mercury capture is limited in flue gases containing high concentrations of sulfur oxides (SOx). In order to gain a more complete understanding of the impact of SOx on ACl, mercury capture was tested under varying conditions of SO2 and SO3 concentrations using a packed bed reactor and simulated flue gas (SFG). The final mercury content of the activated carbons is independent of the SO2 concentration in the SFG, but the presence of SO3 inhibits mercury capture even at the lowest concentration tested (20 ppm). The mercury removal capacity decreases as the sulfur content of the used activated carbons increases from 1 to 10%. In one extreme case, an activated carbon with 10% sulfur, prepared by H2SO4 impregnation, shows almost no mercury capacity. The results suggest that mercury and sulfur oxides are in competition for the same binding sites on the carbon surface.

  6. Impact of Sulfur Oxides on Mercury Capture by Activated Carbon

    SciTech Connect

    Presto, A.A.; Granite, E.J.

    2007-09-15

    Recent field tests of mercury removal with activated carbon injection (ACI) have revealed that mercury capture is limited in flue gases containing high concentrations of sulfur oxides (SOx). In order to gain a more complete understanding of the impact of SOx on ACI, mercury capture was tested under varying conditions of SO2 and SO3 concentrations using a packed bed reactor and simulated flue gas (SFG). The final mercury content of the activated carbons is independent of the SO2 concentration in the SFG, but the presence of SO3 inhibits mercury capture even at the lowest concentration tested (20 ppm). The mercury removal capacity decreases as the sulfur content of the used activated carbons increases from 1 to 10%. In one extreme case, an activated carbon with 10% sulfur, prepared by H2SO4 impregnation, shows almost no mercury capacity. The results suggest that mercury and sulfur oxides are in competition for the same binding sites on the carbon surface.

  7. CCN activation of pure and coated carbon black particles.

    PubMed

    Dusek, U; Reischl, G P; Hitzenberger, R

    2006-02-15

    The CCN (cloud condensation nucleus) activation of pure and coated carbon black particles was investigated using the University of Vienna cloud condensation nuclei counter (Giebl, H.; Berner, A.; Reischl, G.; Puxbaum, H.; Kasper-Giebl, A.; Hitzenberger, R. J. Aerosol Sci. 2002, 33, 1623-1634). The particles were produced by nebulizing an aqueous suspension of carbon black in a Collison atomizer. The activation of pure carbon black particles was found to require higher supersaturations than predicted by calculations representing the particles as insoluble, wettable spheres with mobility equivalent diameter. To test whether this effect is an artifact due to heating of the light-absorbing carbon black particles in the laser beam, experiments at different laser powers were conducted. No systematic dependence of the activation of pure carbon black particles on laser power was observed. The observations could be modeled using spherical particles and an effective contact angle of 4-6 degrees of water at their surface. The addition of a small amount of NaCl to the carbon black particles (by adding 5% by mass NaCl to the carbon black suspension) greatly enhanced their CCN efficiency. The measured CCN efficiencies were consistent with Kohler theory for particles consisting of insoluble and hygroscopic material. However, coating the carbon black particles with hexadecanol (a typical film-forming compound with one hydrophobic and one hydrophilic end) efficiently suppressed the CCN activation of the carbon black particles.

  8. Soil Inorganic Carbon in Deserts: Active Carbon Sink or Inert Reservoir?

    NASA Astrophysics Data System (ADS)

    Monger, H. C.; Cole, D. R.

    2011-12-01

    Soil inorganic carbon is the third largest C pool in the active global carbon cycle, containing at least 800 petagrams of carbon. Although carbonate dissolution-precipitation reactions have been understood for over a century, the role of soil inorganic carbon in carbon sequestration, and in particular pedogenic carbonate, is a deceptively complex process because it involves interdependent connections among climate, plants, microorganisms, silicate minerals, soil moisture, pH, and Ca supply via rain, dust, or in situ weathering. An understanding of soil inorganic carbon as a sink or reservoir also requires examination of the system at local to continental scales and at seasonal to millennial time scales. In desert soils studied in North America, carbon isotope ratios and radiocarbon dates were measured in combination with electron microscopy, lab and field experiments with biological calcite formation, and field measurements of carbon dioxide emissions. These investigations reveal that soil inorganic carbon is both an active sink and a inert reservoir depending on the spatial and temporal scale and source of calcium.

  9. Role of nitrogen in pore development in activated carbon prepared by potassium carbonate activation of lignin

    NASA Astrophysics Data System (ADS)

    Tsubouchi, Naoto; Nishio, Megumi; Mochizuki, Yuuki

    2016-05-01

    The present work focuses on the role of nitrogen in the development of pores in activated carbon produced from lignin by K2CO3 activation, employing a fixed bed reactor under a high-purity He stream at temperatures of 500-900 °C. The specific surface area and pore volume obtained by activation of lignin alone are 230 m2/g and 0.13 cm3/g at 800 °C, and 540 m2/g and 0.31 cm3/g at 900 °C, respectively. Activation of a mixture of lignin and urea provides a significant increase in the surface area and volume, respectively reaching 3300-3400 m2/g and 2.0-2.3 cm3/g after holding at 800-900 °C for 1 h. Heating a lignin/urea/K2CO3 mixture leads to a significant decrease in the yield of released N-containing gases compared to the results for urea alone and a lignin/urea mixture, and most of the nitrogen in the urea is retained in the solid phase. X-ray photoelectron spectroscopy and X-ray diffraction analyses clearly show that part of the remaining nitrogen is present in heterocyclic structures (for example, pyridinic and pyrrolic nitrogen), and the rest is contained as KOCN at ≤600 °C and as KCN at ≥700 °C, such that the latter two compounds can be almost completely removed by water washing. The fate of nitrogen during heating of lignin/urea/K2CO3 and role of nitrogen in pore development in activated carbon are discussed on the basis of the results mentioned above.

  10. Ocean bottom sediments as an active carbon pool.

    NASA Astrophysics Data System (ADS)

    Zimov, N.; Zimov, S. A.

    2015-12-01

    Bottom deposits of oceans, seas and lakes are long term carbon sinks - particulate organic carbon falls to the bottom where it is covered by sediments and preserved by anoxic conditions. However, the upper horizons of these deep sediments ('active layer') interact with bottom waters through diffusion, bubbling of gasses and bioturbation and can thus also act as temporary carbon sources given favorable environment conditions. Oxygen diffusion is the main factor that limits organic decomposition in bottom deposits. Depth of diffusion depends on porosity of sediments and rates of oxygen consumption in the upper horizons. Amplified organic rain leads to higher oxygen demand and, consequently, to a thinner oxic horizon in the bottom sediments. Declined ocean productivity, in contrast, allows oxygen to diffuse deeper into the bottom sediments and remobilizes previously preserved carbon. Therefore a substantial decline in ocean productivity during glacial periods could cause ocean sediments to shift abruptly from a carbon sink to a considerable carbon source. To estimate the effects of the phenomena described above, we present a model of the dynamics and vertical distribution of organic carbon in ocean sediments that considers the input of organic rain, sediments porosity, oxygen availability, rates of sedimentation to the ocean floor and bioturbation. The model enables quantification of bulk carbon storage, carbon distribution within the 'active layer', and the flux of carbon from the upper sediment horizons to deeper deposits as sediments accumulate on the ocean floor. Applying our model, we find that during glacial periods, decreased ocean productivity led to the mobilization of old carbon previously stored within anoxic horizons. Under this scenario, carbon transfer from sediments to ocean waters would have exceeded 10 kg/m2. Our study therefore, suggests that the ocean floor is not merely a passive buffer in the global carbon cycle, but instead an active pool which

  11. Prilling and supercritical drying: A successful duo to produce core-shell polysaccharide aerogel beads for wound healing.

    PubMed

    De Cicco, Felicetta; Russo, Paola; Reverchon, Ernesto; García-González, Carlos A; Aquino, Rita Patrizia; Del Gaudio, Pasquale

    2016-08-20

    Bacterial infections often affect the wound, delaying healing and causing areas of necrosis. In this work, an aerogel in form of core-shell particles, able to prolong drug activity on wounds and to be easily removed was developed. Aerogel microcapsules consisted of a core made by amidated pectin hosting doxycycline, an antibiotic drug with a broad spectrum of action, and a shell consisting of high mannuronic content alginate. Particles were obtained by prilling using a coaxial nozzle for drop production and an ethanolic solution of CaCl2 as gelling promoter. The alcogels where dried using supercritical CO2. The influence of polysaccharides and drug concentrations on aerogel properties was evaluated. Spherical particles with high drug encapsulation efficiency (87%) correlated to alginate concentration in the processed liquid feeds were obtained. The release of the drug, mainly concentrated into the pectin core, was prolonged till 48h, and dependent on both drug/pectin ratio and alginate concentration. PMID:27178955

  12. Prilling and supercritical drying: A successful duo to produce core-shell polysaccharide aerogel beads for wound healing.

    PubMed

    De Cicco, Felicetta; Russo, Paola; Reverchon, Ernesto; García-González, Carlos A; Aquino, Rita Patrizia; Del Gaudio, Pasquale

    2016-08-20

    Bacterial infections often affect the wound, delaying healing and causing areas of necrosis. In this work, an aerogel in form of core-shell particles, able to prolong drug activity on wounds and to be easily removed was developed. Aerogel microcapsules consisted of a core made by amidated pectin hosting doxycycline, an antibiotic drug with a broad spectrum of action, and a shell consisting of high mannuronic content alginate. Particles were obtained by prilling using a coaxial nozzle for drop production and an ethanolic solution of CaCl2 as gelling promoter. The alcogels where dried using supercritical CO2. The influence of polysaccharides and drug concentrations on aerogel properties was evaluated. Spherical particles with high drug encapsulation efficiency (87%) correlated to alginate concentration in the processed liquid feeds were obtained. The release of the drug, mainly concentrated into the pectin core, was prolonged till 48h, and dependent on both drug/pectin ratio and alginate concentration.

  13. Liquid-phase adsorption of organic compounds by granular activated carbon and activated carbon fibers

    SciTech Connect

    Lin, S.H.; Hsu, F.M.

    1995-06-01

    Liquid-phase adsorption of organic compounds by granular activated carbon (GAC) and activated carbon fibers (ACFs) is investigated. Acetone, isopropyl alcohol (IPA), phenol, and tetrahydrofuran (THF) were employed as the model compounds for the present study. It is observed from the experimental results that adsorption of organic compounds by GAC and ACF is influenced by the BET (Brunauer-Emmett-Teller) surface area of adsorbent and the molecular weight, polarity, and solubility of the adsorbate. The adsorption characteristics of GAC and ACFs were found to differ rather significantly. In terms of the adsorption capacity of organic compounds, the time to reach equilibrium adsorption, and the time for complete desorption, ACFs have been observed to be considerably better than GAC. For the organic compounds tested here, the GAC adsorptions were shown to be represented well by the Langmuir isotherm while the ACF adsorption could be adequately described by the Langmuir or the Freundlich isotherm. Column adsorption tests indicated that the exhausted ACFs can be effectively regenerated by static in situ thermal desorption at 150 C, but the same regeneration conditions do not do as well for the exhausted GAC.

  14. Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation.

    PubMed

    Wei, Mingyu; Gao, Long; Li, Jun; Fang, Jia; Cai, Wenxuan; Li, Xiaoxia; Xu, Aihua

    2016-10-01

    Graphitic carbon nitride supported on activated carbon (g-C3N4/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C3N4 was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C3N4 to CO was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C3N4/AC catalyst within 20min with PMS, while g-C3N4+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C3N4 loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO and SO4(-)) in AO7 oxidation was proposed in the system. The CO groups play a key role in the process; while the exposure of more N-(C)3 group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants. PMID:27214000

  15. Activation of peroxymonosulfate by graphitic carbon nitride loaded on activated carbon for organic pollutants degradation.

    PubMed

    Wei, Mingyu; Gao, Long; Li, Jun; Fang, Jia; Cai, Wenxuan; Li, Xiaoxia; Xu, Aihua

    2016-10-01

    Graphitic carbon nitride supported on activated carbon (g-C3N4/AC) was prepared through an in situ thermal approach and used as a metal free catalyst for pollutants degradation in the presence of peroxymonosulfate (PMS) without light irradiation. It was found that g-C3N4 was highly dispersed on the surface of AC with the increase of surface area and the exposition of more edges and defects. The much easier oxidation of C species in g-C3N4 to CO was also observed from XPS spectra. Acid Orange 7 (AO7) and other organic pollutants could be completely degraded by the g-C3N4/AC catalyst within 20min with PMS, while g-C3N4+PMS and AC+PMS showed no significant activity for the reaction. The performance of the catalyst was significantly influenced by the amount of g-C3N4 loaded on AC; but was nearly not affected by the initial solution pH and reaction temperature. In addition, the catalysts presented good stability. A nonradical mechanism accompanied by radical generation (HO and SO4(-)) in AO7 oxidation was proposed in the system. The CO groups play a key role in the process; while the exposure of more N-(C)3 group can further increase its electron density and basicity. This study can contribute to the development of green materials for sustainable remediation of aqueous organic pollutants.

  16. Physicochemical and porosity characteristics of thermally regenerated activated carbon polluted with biological activated carbon process.

    PubMed

    Dong, Lihua; Liu, Wenjun; Jiang, Renfu; Wang, Zhansheng

    2014-11-01

    The characteristics of thermally regenerated activated carbon (AC) polluted with biological activated carbon (BAC) process were investigated. The results showed that the true micropore and sub-micropore volume, pH value, bulk density, and hardness of regenerated AC decreased compared to the virgin AC, but the total pore volume increased. XPS analysis displayed that the ash contents of Al, Si, and Ca in the regenerated AC respectively increased by 3.83%, 2.62% and 1.8%. FTIR spectrum showed that the surface functional groups of virgin and regenerated AC did not change significantly. Pore size distributions indicated that the AC regeneration process resulted in the decrease of micropore and macropore (D>10 μm) volume and the increase of mesopore and macropore (0.1 μm

  17. JV Task 90 - Activated Carbon Production from North Dakota Lignite

    SciTech Connect

    Steven Benson; Charlene Crocker; Rokan Zaman; Mark Musich; Edwin Olson

    2008-03-31

    The Energy & Environmental Research Center (EERC) has pursued a research program for producing activated carbon from North Dakota lignite that can be competitive with commercial-grade activated carbon. As part of this effort, small-scale production of activated carbon was produced from Fort Union lignite. A conceptual design of a commercial activated carbon production plant was drawn, and a market assessment was performed to determine likely revenue streams for the produced carbon. Activated carbon was produced from lignite coal in both laboratory-scale fixed-bed reactors and in a small pilot-scale rotary kiln. The EERC was successfully able to upgrade the laboratory-scale activated carbon production system to a pilot-scale rotary kiln system. The activated carbon produced from North Dakota lignite was superior to commercial grade DARCO{reg_sign} FGD and Rheinbraun's HOK activated coke product with respect to iodine number. The iodine number of North Dakota lignite-derived activated carbon was between 600 and 800 mg I{sub 2}/g, whereas the iodine number of DARCO FGD was between 500 and 600 mg I{sub 2}/g, and the iodine number of Rheinbraun's HOK activated coke product was around 275 mg I{sub 2}/g. The EERC performed both bench-scale and pilot-scale mercury capture tests using the activated carbon made under various optimization process conditions. For comparison, the mercury capture capability of commercial DARCO FGD was also tested. The lab-scale apparatus is a thin fixed-bed mercury-screening system, which has been used by the EERC for many mercury capture screen tests. The pilot-scale systems included two combustion units, both equipped with an electrostatic precipitator (ESP). Activated carbons were also tested in a slipstream baghouse at a Texas power plant. The results indicated that the activated carbon produced from North Dakota lignite coal is capable of removing mercury from flue gas. The tests showed that activated carbon with the greatest iodine number

  18. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S.

    2010-06-01

    A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

  19. Activated carbon fibers and engineered forms from renewable resources

    DOEpatents

    Baker, Frederick S

    2013-02-19

    A method of producing activated carbon fibers (ACFs) includes the steps of providing a natural carbonaceous precursor fiber material, blending the carbonaceous precursor material with a chemical activation agent to form chemical agent-impregnated precursor fibers, spinning the chemical agent-impregnated precursor material into fibers, and thermally treating the chemical agent-impregnated precursor fibers. The carbonaceous precursor material is both carbonized and activated to form ACFs in a single step. The method produces ACFs exclusive of a step to isolate an intermediate carbon fiber.

  20. Nickel adsorption by sodium polyacrylate-grafted activated carbon.

    PubMed

    Ewecharoen, A; Thiravetyan, P; Wendel, E; Bertagnolli, H

    2009-11-15

    A novel sodium polyacrylate grafted activated carbon was produced by using gamma radiation to increase the number of functional groups on the surface. After irradiation the capacity for nickel adsorption was studied and found to have increased from 44.1 to 55.7 mg g(-1). X-ray absorption spectroscopy showed that the adsorbed nickel on activated carbon and irradiation-grafted activated carbon was coordinated with 6 oxygen atoms at 2.04-2.06 A. It is proposed that this grafting technique could be applied to other adsorbents to increase the efficiency of metal adsorption.