New organic aerogels based upon a phenolic-furfural reaction

Pekala, R.W.; Alviso, C.T.; Lu, X.; Groß, Joachim; Fricke, J.

doi:10.1016/0022-3093(95)00027-5

Cited by 172 publications

(89 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…A decisive advantage compared with RF or MF polymerization is that alcoholic solutions can be used. The laborious solvent exchange before drying is thus avoided [153], [154].…”

Section: Organic Aerogelsmentioning

confidence: 99%

Aerogels

Hüsing

Schubert

2006

Ullmann's Encyclopedia of Industrial Chemistry

View full text Add to dashboard Cite

The article contains sections titled: 1. Introduction 2. Synthesis 2.1. Network Formation and Structure 2.1.1. Inorganic Aerogels 2.1.1.1. SiO 2 Aerogels 2.1.1.2. Metal Oxide Aerogels 2.1.2. Inorganic/Organic Hybrid Aerogels 2.1.3. Organic Aerogels 2.2. Drying Methods 2.2.1. Supercritical Drying 2.2.1.1. Drying in Organic Solvents 2.2.1.2. Supercritical Drying with CO 2 2.2.2. Freeze Drying 2.2.3. Ambient Pressure Drying 2.3. Modification of Aerogels after Drying 3. Properties 3.1. Structural Properties 3.2. Physical and Chemical Properties 3.2.1. Optical Properties 3.2.2. Mechanical and Acoustic Properties 3.2.3. Thermal Conductivity 3.2.4. Hydrophobicity 4. Applications 4.1. Çerenkov Detectors 4.2. Thermal Insulation 4.3. Catalysis 4.4. Application as Storage Media 4.5. Electrical and Electronic Applications 4.6. Acoustic and Mechanical Applications 4.7. Optical Applications 4.8. Other Applications 5. Future Perspectives Aerogels are unique among solid materials. They have extremely low densities (up to 95 % of their volume is air), large open pores, and a high inner surface area. This combination of properties results in interesting physical properties, e.g., for silica aerogels extremely low thermal conductivities and low sound velocities are combined with optical transparency. Aerogels are typically prepared via wet chemical processes, such as sol – gel processing, and thus their pore system is initially filled with liquid. Only special drying techniques allow for exchange of the pore liquid against air while maintaining the filigrane solid framework. The most common drying technique is supercritical extraction, and sometimes chemical modification of the inner surface can be used to facilitate drying. The structure of the gel network, and thus the physical properties of aerogels, decisively depends on the choice of the precursors and the chemical reaction parameters for preparing the gels. Therefore, the later materials properties can be deliberately designed in the starting reaction solution.

show abstract

“…A decisive advantage compared with RF or MF polymerization is that alcoholic solutions can be used. The laborious solvent exchange before drying is thus avoided [153], [154].…”

Section: Organic Aerogelsmentioning

confidence: 99%

Aerogels

Hüsing

Schubert

2006

Ullmann's Encyclopedia of Industrial Chemistry

View full text Add to dashboard Cite

show abstract

“…Resorcinol and phenol are valuable precursors of carbonaceous solids. Phenol is less reactive than resorcinol but is cheaper [9][10][11]. Resorcinol, although expensive, presents several advantages for the preparation of gels.…”

Section: Introductionmentioning

confidence: 99%

Bimodal activated carbons derived from resorcinol-formaldehyde cryogels

Szczurek

Amaral-Labat

Fierro

et al. 2011

Science and Technology of Advanced Materials

View full text Add to dashboard Cite

Resorcinol-formaldehyde cryogels prepared at different dilution ratios have been activated with phosphoric acid at 450• C and compared with their carbonaceous counterparts obtained by pyrolysis at 900• C. Whereas the latter were, as expected, highly mesoporous carbons, the former cryogels had very different pore textures. Highly diluted cryogels allowed preparation of microporous materials with high surface areas, but activation of initially dense cryogels led to almost non-porous carbons, with much lower surface areas than those obtained by pyrolysis. The optimal acid concentration for activation, corresponding to stoichiometry between molecules of acid and hydroxyl groups, was 2 M l −1 , and the acid-cryogel contact time also had an optimal value. Such optimization allowed us to achieve surface areas and micropore volumes among the highest ever obtained by activation with H 3 PO 4 , close to 2200 m 2 g −1 and 0.7 cm 3 g −1 , respectively. Activation of diluted cryogels with a lower acid concentration of 1.2 M l −1 led to authentic bimodal activated carbons, having a surface area as high as 1780 m 2 g −1 and 0.6 cm 3 g −1 of microporous volume easily accessible through a widely developed macroporosity.

show abstract

“…There are several precursors that can be used to develop carbon gels including phenol, resorcinol or cresol in the case of hydroxybenzenes whereas as aldehyde it is possible to use formaldehyde, furfural, etc. (Czzakel et al, 2005;Dingcai & Rouwen, 2006;Long et al, 2008aLong et al, , 2008bPekala et al, 1995 ;Scherdel & Reichenauer, 2009). Amongst all the possible variations, probably the most commonly synthesized carbon gels are those based on resorcinol and formaldehyde, although in order to reduce the cost of the materials involved in the synthesis process, some less expensive precursors, such as phenol (Mukai et al, 2005a;Scherdel & Reichenauer, 2009;Teng & Wang, 2000) or cellulose (Gryzb et al, 2010), have attracted interest in recent years.…”

Section: Synthesis Of Nanostructured Carbon Xerogelsmentioning

confidence: 99%

“…Basically, an organic gel is a solid nanostructure comprised of nano-sized pores and interlinked primary particles obtained by means of polymerization reactions between hydroxylated benzenes and aldehydes, and then subjected to a drying process. The most commonly used monomers are resorcinol and formaldehyde (Al-Mutasheb & Ritter, 2003;Czzakel et al, 2005;Job et al, 2004;Tian et al, 2011a;Zhang et al, 2007;Zhu et al, 2007;Zubizarreta et al, 2008a) but, there are other potential combinations such as phenol/formaldehyde (Mukai et al, 2005a;Scherdel & Reichenauer, 2009;Teng & Wang, www.intechopen.com Nanomaterials 188 2000), phenol/furfural (Dingcai & Ruowen, 2006;Long et al, 2008a;Pekala et al, 1995), phenol/melamine/formaldehyde (Long et al, 2008b), cresol/formaldehyde (Li et al, 2001;Zhu et al, 2006), etc. As shown in Figure 1, the formation of organic gels involves the following stages: (i) formation of a three-dimensional polymer in a solvent, known as gelation step, (ii) curing period where the crosslinking of previously formed polymer clusters (particles) takes place and, finally, (iii) drying step, that can be performed under subcritical, supercritical or freezing conditions, resulting in xerogels, aerogels and cryogels, respectively (Al-Mutasheb & Ritter, 2003;Czzakel et al, 2005;Job et al, 2004;Zubizarreta et al, 2008a).…”

Section: Introductionmentioning

confidence: 99%