Effect of initial sol concentration on the microstructure and morphology of carbon aerogels

Hajizadeh, Alireza; Bahramian, Ahmad Reza; Seifi, Azadeh; Naseri, Iman

doi:10.1007/s10971-014-3520-4

Cited by 25 publications

(7 citation statements)

References 30 publications

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“…Normally, the XRD pattern of CAs contains two peaks at 2θ values of around 23.5°and 43.5°, which originate from strong (0 0 2) and weak (1 0 1) carbon diffractions, respectively. 12, 104,105 As argued by Lin and Ritter, by comparing XRD patterns of CAs, graphite and activated carbon, it can be concluded that CAs are not completely amorphous. 106 Conventional CAs are considered as partly graphitized carbon materials with some graphite-like carbon structures interconnected via amorphous carbons.…”

Section: Structural Characteristics Of Carbon Aerogelsmentioning

confidence: 89%

Self-assembled and pyrolyzed carbon aerogels: an overview of their preparation mechanisms, properties and applications

Allahbakhsh

Bahramian

2015

Nanoscale

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An overview of the synthesis conditions and mechanisms for the fabrication of different types of carbon aerogels, as well as the structural and functional properties of these materials, is presented here. In this overview, carbon aerogels are classified into three major categories: (i) conventional pyrolyzed organic-based carbon aerogels, which are products of the pyrolysis process of organic aerogels; (ii) self-assembled carbon aerogels, which are products of a reduction process; and (iii) nanocomposite carbon aerogels. Synthesis mechanisms for the sol-gel process of organic aerogels are reviewed using different mechanisms suggested in the literature. Moreover, the overall fabrication process of self-assembled carbon aerogels (graphene and carbon nanotube aerogels) is covered and the suggested mechanism for the gelation process of self-assembled carbon aerogels during the reduction process is investigated using reported mechanisms. The structural performance and functional properties (electrochemical and thermal properties) of different types of carbon aerogels are covered in detail. Moreover, different structural features of carbon aerogels and the influence of synthesis conditions on these structural characteristics are assessed and compared. Based on the literature results covered in this review paper, carbon aerogels are perfect candidates for the fabrication of ultra-low density supercapacitors, as well as thermal insulating materials.

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Section: Structural Characteristics Of Carbon Aerogelsmentioning

confidence: 89%

Self-assembled and pyrolyzed carbon aerogels: an overview of their preparation mechanisms, properties and applications

Allahbakhsh

Bahramian

2015

Nanoscale

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“…As demonstrated in Figure 7, absorption bands at 1476 cm À1 , 1603 cm À1 , 1383 cm À1 , 2918 cm À1 , 2849 cm À1 , and 3400 cm À1 are attributed to novolac aerogel containing NPCMs, which are related to stretching vibration of the aromatic ring in novolac, carbonyl (C = O) stretching vibration in urethane group as well as PCL, PW stretching vibration of unsaturated C-H bonds, and N-H group stretching vibration in NPCMs. 16,31,32 The only distinct difference between pure novolac aerogel and novolac aerogel-NPCMs spectra is that there is a slight transfer in aforementioned wavelength numbers, which indicate interactions between novolac aerogel and NPCMs. Therefore, it can be concluded that placement, distribution, and NPCMs chemical reaction among novolac colloids and novolac aerogel colloids formation around NPCMs has been proceeded in an adequate way.…”

Section: Novolac Aerogel-npcms Ftir Characterizationmentioning

confidence: 99%

Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

Abdeali

Bahramian

2021

Intl J of Energy Research

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Summary Aerogels are one of the most promising nano‐dimension open‐cell foams with considerably varied characteristics such as high porosity, super large specific surface area, low density, and super low thermal conductivity. Aerogel's high porosity and microstructure consisting of micro‐ and nanoparticles as well as pores in nanometer dimension are the origin of distinctive properties. However, the main challenge of aerogels is their low density (0.05−0.50 gcm3), which leads to equal thermal diffusion (normalα×10−7) compared with general thermal insulators. To minimize aerogel thermal diffusion and to enhance thermal insulation, replacing some aerogel colloids with phase‐change material nanocapsules (NPCMs) (while aerogel IUPAC definition and at least porosity of 80% is preserved) is proposed in this work. While NPCMs undergo a physical change during phase transfer, temperature becomes persistent, and as a consequence, specific heat capacity (Cp) getting close to an infinite number and thermal diffusion (normalα=knormalρCp) will tend to very low values. Results have demonstrated that by only applying 4.5 wt.% of paraffin wax core /polyurethane shell (PW/PU) NPCMs instead of some novolac aerogel colloids, aerogel has experienced temperature decrement as well as stability. During NPCMs' melting process, thermal diffusivity has reached 2.5×10−12 and temperature increment delay rate has become 40%.

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“…Their low cost, high tensile strength, and fire‐retardant characteristics make them as a great candidate for preparation of organic aerogels. Recently, Bahramian research group has focused on the preparation and characterization of novolac type phenolic aerogels for high temperature applications 8–12 . Moreover, they reported a new sol–gel method for preparation of novolac aerogels named as solvent saturated vapor atmosphere (SSVA) 13 .…”

Section: Introductionmentioning

confidence: 99%

Microstructural properties, thermal insulation and thermal degradation behavior of boron‐containingmonolithic novolac xerogels

Seraji

Ahmad

2020

J of Applied Polymer Sci

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Enhancement of thermal stability‐insulation performance of hyper porous materials is the premier issue to design of novel porous thermal protection systems. Boron‐containing monolithic novolac xerogels (BCNXs) were synthesized using sol–gel networking of novolac resin with hexamethylenetetramine (HMTA) and boric acid at the solvent saturated vapor atmosphere (SSVA). The aim was to elucidate the effect of higher crosslinking density and thermal stable boron containing chemical bonds on the microstructure, thermal conductivity, and thermal oxidation stability of novolac xerogels. The results of FESEM and BET analysis showed that the microstructural characteristics of xerogels are significantly depend on the HMTA and boric acid concentration. The thermogravimetric results were analyzed using characteristic kinetic temperature (CKT)‐characteristic kinetic temperature range (CKTR) approximations. The effect of micromorphology of xerogels on the thermal conductivity was investigated. The effective thermal conductivity of samples were in the range of 0.031–0.048 W/m K.

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Effect of initial sol concentration on the microstructure and morphology of carbon aerogels

Cited by 25 publications

References 30 publications

Self-assembled and pyrolyzed carbon aerogels: an overview of their preparation mechanisms, properties and applications

Self-assembled and pyrolyzed carbon aerogels: an overview of their preparation mechanisms, properties and applications

Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

Microstructural properties, thermal insulation and thermal degradation behavior of boron‐containingmonolithic novolac xerogels

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