A New Method of Preparation of Aerogel-Like Materials Using a Freeze-Drying Process

Klvana, D.; Chaouki, Jamal; Repellin-Lacroix, M.; Pajonk, G.M.

doi:10.1051/jphyscol:1989405

“…It is reported that pore structure was damaged in several ways during freezing of gel [18], resulting in the pore size distribution different from that of aerogel. It is also revealed that the principal difference between cryogel and aerogel is in relation with their respective macropore volumes [19]. The observed water-durability of cryogel might therefore be related to such differences.…”

Section: Discussionmentioning

confidence: 96%

Silica-doped alumina cryogels with high thermal stability

Osaki

¹

,

Nagashima

²

,

Watari

³

et al. 2007

Journal of Non-Crystalline Solids

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“…After first experiments described by Y. Trambouze [7,8] the cryogel-derived powders of the individual refractory oxides were carefully studied by D. Klvana, J. Kirchnerova and J. Chaouki [10,73]. Recent investigations continue to open the new features and applications of the cryogel-derived porous materials.…”

Section: Cryogel-based Porous Structures and Ceramicsmentioning

confidence: 99%

“…However, their intermediates were not initially considered as cryogels; this term was introduced into the inorganic materials science by D. Klvana and G. M. Pajonk who have published the first comparative studies of cryogels and aerogels [10,11]. According to the currently used concept, inorganic cryogels is specific kind of freeze drying synthesis products obtained by low temperature processing of gels and residues containing significant amount of inorganic components.…”

Section: Introductionmentioning

confidence: 98%

Inorganic cryogels for energy saving and conversion

Shlyakhtin

¹

,

Oh

²

2008

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Cryogels are usually obtained by freezing and thawing or freeze drying of gels and residues. Essential morphological features of the cryogels are bimodal pore size distribution, nanosize of the primary particles (crystallites) and their low agglomeration. Widely used for a decades in the polymer science and technology, cryogels find now a growing number of applications in the electroceramic materials. Freeze casting technique based on the freeze gelation effect is proved to be useful forming method in the production of complex-shaped SiO 2 -containing electroceramics. Directed modification of the micromorphology by using solvent exchange schemes allows to obtain SiO 2 cryogel monoliths with density ≤ 0.05 g cm −3 and specific surface area 700-800 m 2 g −1 suitable for cryogenic thermal insulation of the superconducting devices. Excellent electrocatalytic activity of the macro/mesoporous PtRu/C cryogels in the methanol oxidation reaction makes them perspective anode materials of direct methanol fuel cells. Application of the cryogel-derived starting powders promoted substantial reduction of the sintering temperatures for a number of electroceramic materials. MnO 2 -and V 2 O 5 -based cryogels are efficient cathode materials for secondary lithium batteries with specific capacity up to 300 mAh g −1 .Recent studies demonstrated also a feasibility of cryochemical approaches to the synthesis of complex oxide-based nanocrystalline electrode materials for electrochemical supercapacitors with high specific capacity at current densities up to 50 mA cm −2 .

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“…The pore liquid is frozen and then sublimed in vacuo. There were some attempts to use this method for the production of aerogels [180][181][182]. However, the aging period must be extended to stabilize the gel network, the solvent must be replaced by one with a low expansion coefficient and a high sublimation pressure, and low freezing temperatures are attained by addition of salts.…”

Section: Freeze Dryingmentioning

confidence: 99%

Aerogels

Hüsing

¹

,

Schubert

²

2006

Ullmann's Encyclopedia of Industrial Chemistry

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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.

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A New Method of Preparation of Aerogel-Like Materials Using a Freeze-Drying Process

Cited by 14 publications

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Silica-doped alumina cryogels with high thermal stability

Silica-doped alumina cryogels with high thermal stability

Inorganic cryogels for energy saving and conversion

Aerogels

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