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.

Hierarchically Nanostructured Zeolites of Tunable Porosities with Aerogel Templating

2011 ◽  
Vol 1306 ◽  
Author(s):  
Yousheng Tao ◽  
Morinobu Endo ◽  
Katsumi Kaneko
Keyword(s):  
Carbon Dioxide ◽  
Template Synthesis ◽  
Colloidal Silica ◽  
Lower Cost ◽  
Supercritical Drying ◽  
Nanoporous Carbon ◽  
Carbon Aerogels ◽  
Resorcinol Formaldehyde ◽  
Carbon Xerogels ◽  
Recent Developments

ABSTRACTWe present the synthesis of resorcinol-formaldehyde aerogels and carbon aerogels of different nanoporosities, emphasizing on the recent developments in fabrication pathways of lower cost. Recent results showed a simple way to the production of highly nanoporous carbon xerogels. While using an approach combined colloidal silica nanocasting and carbon dioxide supercritical drying, hydrophilicity-controlled carbon aerogels with high mesoporosity were synthesized. Then, we demonstrate the functions of these aerogels for template synthesis of hierarchically nanostructured zeolites having micropores and mesopores.

Gas permeability of carbon aerogels

1993 ◽  
Vol 8 (12) ◽  
pp. 3100-3105 ◽  
Author(s):  
F-M. Kong ◽  
J.D. LeMay ◽  
S.S. Hulsey ◽  
C.T. Alviso ◽  
R.W. Pekala
Keyword(s):  
Pore Size ◽  
Gas Flow ◽  
Gas Permeability ◽  
High Surface ◽  
High Surface Area ◽  
Supercritical Drying ◽  
Flow Equation ◽  
Carbon Aerogels ◽  
Thin Specimen ◽  
Potential Applications

Carbon aerogels are synthesized via the aqueous polycondensation of resorcinol with formaldehyde, followed by supercritical drying and subsequent pyrolysis at 1050 °C. As a result of their interconnected porosity, ultrafine cell/pore size, and high surface area, carbon aerogels have many potential applications such as supercapacitors, battery electrodes, catalyst supports, and gas filters. The performance of carbon aerogels in the latter two applications depends on the permeability or gas flow conductance in these materials. By measuring the pressure differential across a thin specimen and the nitrogen gas flow rate in the viscous regime, the permeability of carbon aerogels was calculated from equations based upon Darcy's law. Our measurements show that carbon aerogels have permeabilities on the order of 10−12 to 10−10 cm2 over the density range from 0.05–0.44 g/cm3. Like many other aerogel properties, the permeability of carbon aerogels follows a power law relationship with density, reflecting differences in the average mesopore size. Comparing the results from this study with the permeability of silica aerogels reported by other workers, we found that the permeability of aerogels is governed by a simple universal flow equation. This paper discusses the relationship among permeability, pore size, and density in carbon aerogels.

Performance Study and Structure Control of Carbon Aerogel

2013 ◽  
Vol 706-708 ◽  
pp. 897-900 ◽  
Author(s):  
Rui He ◽  
Xuan Liu ◽  
Zhen Fa Liu ◽  
Li Hui Zhang
Keyword(s):  
High Surface ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Carbon Aerogel ◽  
Preparation Condition ◽  
Carbon Aerogels ◽  
Performance Study ◽  
Structure Control ◽  
Sol Gel Process ◽  
Nanopore Structure

In this research the fabrication of carbon aerogel is reported. nanopore carbon aerogels were prepared via a sol-gel process with resorcinol and formaldehyde (RF) aerogels,which were cost-effectively manufacture form Rf wet gels by an ambient drying technique instead of conventional supercritical drying. The key of the work is to fabricate carbon aerogels with controllable nanopore structure, which means sharp pore size distribution and extremely high surface area.The influence of preparation condition of carbon aerogels was studied by scanning electron microscope and Micropore Physisorption Analyzer. The BET surface of the carbon aerogels are from 749m2/g to 1156m2/g .The size of the carbon nanoparticles are in the range of 20nm~40nm. The micro-pore volume and bore diameter can be controlled by gelation conditions such as RF mass fraction.

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.

Preparation and Characterization of Ultralow Density Silica Aerogels by Acetonitrile Supercritical Drying

2012 ◽  
Vol 519 ◽  
pp. 83-86 ◽  
Author(s):  
Guang Wu Liu ◽  
Xing Yuan Ni ◽  
Bin Zhou ◽  
Qiu Jie Yu
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Silica Aerogel ◽  
Sol Gel ◽  
Supercritical Drying ◽  
Silica Aerogels ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Sol Gel Process

This paper deals with the synthesis of ultralow density silica aerogels using tetramethyl orthosilicate (TMOS) as the precursor via sol-gel process followed by supercritical drying using acetonitrile solvent extraction. Ultralow density silica aerogels with 6 mg/cc of density was made for the molar ratio by this method. The microstructure and morphology of the ultralow density silica aerogels was characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. The results show that the ultralow density silica aerogel has the high specific surface area of 812m2/g. Thermal conductivities at desired temperatures were analyzed by the transient plane heat source method. Thermal conductivity coefficients of silica aerogel monoliths changed from 0.024 to 0.043W/ (m K) as temperature increased to 400°C, revealed an excellent heat insulation effect during thermal process.

Synthesis and Structural Characterization of SiO2-Al2O3 Xerogels

2007 ◽  
Vol 336-338 ◽  
pp. 2286-2289
Author(s):  
Fei He ◽  
Xiao Dong He ◽  
Yao Li
Keyword(s):  
Structural Change ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Supercritical Drying ◽  
High Specific Surface Area ◽  
Molar Ratio

Low-density xSiO2-(1-x)Al2O3 xerogels with x=0.9, 0.8, 0.7, 0.6 (mole fractions) were prepared by sol-gel and non-supercritical drying. Silica alkogels, which were the framework of binary composite materials, formed from tetraethyl orthosilicate (TEOS) by hydrolytic condensation with a molar ratio of TEOS: H2O: alcohol: hydrochloric acid: ammonia =1: 4: 10: 7.5×10-4: 0.0375. Aluminum hydroxide derived from Al(NO3)3·9H2O and NH4OH acting in the alcohol solution under the condition of catalyst. After filtrating and washing, the precipitation was mixed into silica sols to form SiO2-Al2O3 mixed oxide gels with different silicon and aluminum molar ratio. The structural change and crystallization of the binary xerogels were investigated after heat treatment at 600 for 2 h by the means of X-ray diffraction. Nitrogen adsorption experiment was performed to estimate specific surface area, porous volume and pore size distribution. The structural change of xerogels was observed by FT-IR spectroscopy. The resulting mixed xerogels possess of mesoporous structure which is characteristic of cylindrical pores, high specific surface area of 596-863 m2/g and a relatively narrow pore distribution of 2.8-30 nm. Al2O3 is introduced into the SiO2 phase and some of Al-O-Si bonds form.

scholarly journals Electrochemical Behavior of Carbon Aerogels Derived From Different Precursors

1995 ◽  
Vol 393 ◽  
Author(s):  
R.W. Pekala ◽  
C.T. Alviso ◽  
J.K. Nielsen ◽  
T.D. Tran ◽  
G.A.M. Reynolds ◽  
...  
Keyword(s):  
Cell Structure ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Supercritical Drying ◽  
Inert Atmosphere ◽  
Solid Matrix ◽  
Carbon Aerogels ◽  
Energy Storage Devices ◽  
Electrochemical Double Layer

ABSTRACTThe 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 aerogels have an open-cell structure with an ultrafine pore size (<100 nm), high surface area (400-1100 m2/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.

Facile synthesis of an amine hybrid aerogel with high adsorption efficiency and regenerability for air capture via a solvothermal-assisted sol–gel process and supercritical drying

2015 ◽  
Vol 17 (6) ◽  
pp. 3436-3445 ◽  
Author(s):  
Yong Kong ◽  
Xiaodong Shen ◽  
Sheng Cui ◽  
Maohong Fan
Keyword(s):  
Sol Gel ◽  
Supercritical Drying ◽  
Adsorption Efficiency ◽  
High Adsorption ◽  
Facile Synthesis ◽  
Composite Aerogel ◽  
Resorcinol Formaldehyde ◽  
Silica Composite ◽  
Sol Gel Process ◽  
Air Capture

An amine hybrid resorcinol–formaldehyde/silica composite aerogel with high adsorption efficiency and regenerability for air capture was developed by a solvothermal-assisted sol–gel process combined with supercritical drying.

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.

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