Gas Transport in Sol-Gel Derived Porous Carbon Aerogels

1996 ◽  
Vol 464 ◽  
Author(s):  
G. Reichenauer ◽  
J. Fricke
Keyword(s):  
Sol Gel ◽  
Water Desalination ◽  
Carbon Aerogels ◽  
High Porosity ◽  
Nanoporous Carbons ◽  
Time Resolved ◽  
Resorcinol Formaldehyde ◽  
Dead End ◽  
Gas Expansion ◽  
Different Gases

ABSTRACTDue to their high electrical conductivity, their large specific surface area and their high porosity sol-gel derived nanoporous carbons are promising materials for electrodes, e.g. in water desalination systems or fuel cells. In order to optimize their properties with respect to these applications information is needed about transient and steady state transport through the interconnected pores.Dynamic gas expansion and time resolved permeation measurements allow to determine the relevantquantities, i.e. the permeability, the ratio of gas phase to surface diffusion and the volume of dead end pores along with the tortuosity.Experimental data on nanoporous carbons of different density are presented. All samples investigated were prepared via pyrolysis of resorcinol formaldehyde aerogels. The measurements were performed with different gases below 0.1 MPa.

Fabrication of Carbon Aerogels

2006 ◽  
Vol 11-12 ◽  
pp. 19-22 ◽  
Author(s):  
Y.N. Feng ◽  
Lei Miao ◽  
Yong Ge Cao ◽  
T. Nishi ◽  
Sakae Tanemura ◽  
...  
Keyword(s):  
Pore Size ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Limited Range ◽  
Molar Ratio ◽  
Carbon Aerogels ◽  
Resorcinol Formaldehyde ◽  
Catalyst Content ◽  
Fabrication Parameters ◽  
Pyrolysis Processes

RF (Resorcinol-Formaldehyde) aerogels and carbon aerogels were prepared through the sol-gel method following the routes of polymerization, gelation, supercritical drying and pyrolysis processes. The influence of fabrication parameters on the textural structure of the samples, e.g., specific surface area, pore size, and pore size distribution, etc., were systematically investigated. With a decrease in the R/F molar ratio, or an increase in the catalyst content within a limited range, the porosity of the nanostructure materials increases. The optimal temperature of pyrolysis for RF aerogel was investigated by TGA (Thermogravimetric Analysis).

The Effect of Carbonization Temperature on Carbon Aerogels Structure

2020 ◽  
Vol 842 ◽  
pp. 182-185
Author(s):  
Sha Sha Wang ◽  
Yue Long Xu ◽  
Li Hui Zhang ◽  
Zhen Fa Liu
Keyword(s):  
Pore Size ◽  
Network Structure ◽  
Sol Gel ◽  
Carbonization Temperature ◽  
Carbon Aerogels ◽  
Sem Images ◽  
Resorcinol Formaldehyde ◽  
Graphitization Degree ◽  
Adsorption Amount ◽  
Xrd Patterns

Phloroglucinol–resorcinol–formaldehyde (PRF) carbon aerogels were synthesized by sol–gel reaction. The results of condition of shrinkage showed a degree of crosslinking more obvious with the increasing of the carbonization temperature. CA900 displays the highest adsorption amount and the biggest loops, as well as an increase in pore size and volume in comparison to the others samples. The SEM images of carbon aerogels under different carbonization temperature possess closer network structure and excellent connectivity, the holes between the network are abundant. The XRD patterns show that the high carbonization temperature can enhance the graphitization degree of carbon aerogels.

Preparation and Characterization of Phloroglucinol-Resorcinol-Formaldehyde Carbon Aerogels

2013 ◽  
Vol 423-426 ◽  
pp. 523-527
Author(s):  
Xuan Liu ◽  
Zhen Fa Liu ◽  
Hao Lin Fu ◽  
Rui He ◽  
Li Hui Zhang
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
High Specific Surface Area ◽  
Carbon Aerogels ◽  
Resorcinol Formaldehyde ◽  
Sol Gel Process ◽  
Solvent Replacement ◽  
Organic Aerogels

Phloroglucinol-resorcinol-formaldehyde organic aerogels (PRF) were prepared using phloroglucinol, resorcinol and formaldehyde in a sol-gel process, solvent replacement and drying at room temperature. The phloroglucinol-resorcinol-formaldehyde carbon aerogels (CPRF) were prepared by charring the PRF at high temperature under the aegis of helium flow. The microstructure of CPRF was characterized by infrared spectroscopy, specific surface area analyzer and scanning electron microscopy. The results showed that the CPRF had continuous network structure and high specific surface area.

scholarly journals Fabrication Of Carbon Aerogels From Coir For Oil Adsorption

2022 ◽  
Vol 964 (1) ◽  
pp. 012033
Author(s):  
Hieu M Nguyen ◽  
Khoi A Tran ◽  
Tram T N Nguyen ◽  
Nga N H Do ◽  
Kien A Le ◽  
...  
Keyword(s):  
Freeze Drying ◽  
Oil Spills ◽  
Sol Gel ◽  
Urea Solution ◽  
Carbon Aerogels ◽  
Low Density ◽  
High Porosity ◽  
Motor Oil ◽  
Sol Gel Process ◽  
Oil Adsorption

Abstract Coir, known as coconut fibers, are an abundant cellulosic source in Vietnam, which are mostly discarded when copra and coconut water are taken, causing environmental pollution and waste of potential biomass. In this research, carbon aerogels from chemically pretreated coir were successfully synthesized via simple sol-gel process with NaOH-urea solution, economical freeze-drying, and carbonization. The samples, including pretreated coir, coir aerogels, and carbon aerogels, are characterized using FTIR spectroscopy, SEM, XRD spectroscopy, and TGA. The carbon aerogels exhibit low density (0.034–0.047 g/cm3), high porosity (97.63–98.32 %), and comparable motor oil sorption capacity (22.71 g/g). The properties of carbon aerogels are compared with those of coir aerogels, indicating such better values than those of coir aerogels. Coir-derived carbon aerogels is a potential replacement for the hydrophobically-coated cellulose aerogels in term of treating oil spills.

scholarly journals Water-Ionic Liquid Binary Mixture Tailored Resorcinol-Formaldehyde Carbon Aerogels without Added Catalyst

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4208 ◽  
Author(s):  
Balázs Nagy ◽  
István Bakos ◽  
Erik Geissler ◽  
Krisztina László
Keyword(s):  
Ionic Liquid ◽  
Water Content ◽  
Sol Gel ◽  
Structural Defects ◽  
Carbon Aerogels ◽  
Process Conditions ◽  
Scanning Electron Micrographs ◽  
Initial Water ◽  
Resorcinol Formaldehyde ◽  
Bead Size

The potential applications of mesoporous carbon aerogels are wide-ranging. These gels are often obtained from resorcinol-formaldehyde (RF) hydrogel precursors. The sol-gel method in this synthesis provides an efficient and versatile means of product control through systematic variation of process conditions, such as pH, stoichiometry, concentration, catalyst, further additives, etc., in addition to the drying and pyrolytic conditions. Here, a novel means of tuning the texture of carbon aerogels is proposed. Water-1-ethyl-3-methylimidazolium ethyl sulfate ([emim][EtSO4] mixtures constitutes a polycondensation medium that requires no added catalyst, thus yielding an intrinsically metal-free carbon aerogel after pyrolysis. We also show that the carbon morphology is tailored by the supramolecular structure of the aqueous ionic liquid. The results of scanning electron micrographs, low-temperature nitrogen adsorption/desorption isotherms, and small-angle X-ray scattering (SAXS) confirm that changing the initial water concentration from 9 to 55 wt % gives rise to systematic alteration of the mesopore size and volume, as well as of the bead size. The pore structure becomes consolidated only when the water content exceeds 25 wt %. When the water content reaches 55 wt %, the bead size increases by two orders of magnitude. The electrocatalytic performance, however, is compromised, most probably by structural defects.

scholarly journals Structural Evolution in Carbon Aerogels as a function of Precursor Material and Pyrolysis Temperature

1996 ◽  
Vol 431 ◽  
Author(s):  
J. Gross ◽  
C. T. Alviso ◽  
R. W. Pekala
Keyword(s):  
Pyrolysis Temperature ◽  
Phenol Formaldehyde ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Structural Evolution ◽  
Vitreous Carbon ◽  
Carbon Aerogels ◽  
High Porosity ◽  
Precursor Material

AbstractSeveral organic reactions that proceed through a sol-gel transition have been identified at LLNL. The most-studied reaction involves the aqueous polycondensation of resorcinol (1,3- dihydroxybenzene) with formaldehyde. Recently, we have shown that phenol can be added to this polymerization as a comonomer. The resultant crosslinked gels are supercritically dried from carbon dioxide (Tc=31°C, Pc = 7.4 MPa) to give resorcinol-phenol-formaldehyde (RPF) aerogels. Because RPF aerogels are composed of a highly crosslinked aromatic polymer, they can be pyrolyzed in an inert atmosphere to form vitreous carbon monoliths (CRPF). The resultant aerogels are black in color and no longer transparent, yet they retain the high porosity (40–98 %), ultrafine cell/pore size (< 50 nm), high surface area (600–800 m2/g), and interconnected particle (˜10 nm) morphology of their organic precursors. In this study, we examine the acoustic and mechanical properties of these materials as a function of precursor material and pyrolysis temperature. It is shown that the elastic moduli of RPF and CRPF is higher than that of pure RF / CRF aerogels at a given density. Upon pyrolysis RPF aerogels tend to shrink to a larger extent.

scholarly journals Selectivity of Tungsten Oxide Synthesized by Sol-Gel Method Towards Some Volatile Organic Compounds and Gaseous Materials in a Broad Range of Temperatures

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 523 ◽  
Author(s):  
Simonas Ramanavičius ◽  
Milda Petrulevičienė ◽  
Jurga Juodkazytė ◽  
Asta Grigucevičienė ◽  
Arūnas Ramanavičius
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Sol Gel ◽  
Temperature Dependent ◽  
Sensing Systems ◽  
Sensing Material ◽  
Operational Temperature ◽  
Volatile Organic ◽  
Different Gases

In this research, the investigation of sensing properties of non-stoichiometric WO3 (WO3−x) film towards some volatile organic compounds (VOC) (namely: Methanol, ethanol, isopropanol, acetone) and ammonia gas are reported. Sensors were tested at several temperatures within the interval ranging from a relatively low temperature of 60 up to 270 °C. Significant variation of selectivity, which depended on the operational temperature of sensor, was observed. Here, the reported WO3/WO3–x-based sensing material opens an avenue for the design of sensors with temperature-dependent sensitivity, which can be applied in the design of new gas- and/or VOC-sensing systems that are dedicated for the determination of particular gas- and/or VOC-based analyte concentration in the mixture of different gases and/or VOCs, using multivariate analysis of variance (MANOVA).

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