with various oxides demonstrate outstanding mechanical properties and enhanced
electrical conductivity.
Keywords Freeze-drying synthesis • Co-precipitation • Nanoparticle isolation •
Oriented porosity • Carbon cryogel
Abbreviations
CNT
Carbon nanotubes
FESEM Field emission SEM
GO
Graphene oxide
HAP
Hydroxyapatite
RGO
Reduced graphene oxide
RF
Resorcinol-formaldehyde
SEM
Scanning electron microscopy
TEM
Transmission electron microscopy
1 Introduction
The term “cryogel” was first introduced into the field of inorganic materials by
Klvana and Pajonk [1–3], who considered cryogels, together with xerogels and
aerogels, as one of the possible drying products of SiO 2 .nH 2 O- and Al 2 O 3 .nH 2 Obased hydrogels. In their experiments, freezing and freeze-drying of wet gels were
used to avoid pore collapse due to the extreme surface tension effects of water
removal during atmospheric drying and to retain most of the tiny morphological
features of gels in the dried state. As the term “cryogel” is most commonly used in
papers on inorganic materials obtained by freeze-drying [4–6], it will be used here
to be consistent with previous studies in this field. Therefore, the first studies on the
synthesis of inorganic cryogels go back to the early 1970s [7–9], soon after the
discovery of the freeze-drying synthesis of inorganic materials from frozen aqueous
solutions by Landsberg and Campbell [10].
This “extended” approach, whereby a cryogel is considered as the freeze-drying
product of any frozen liquid–solid system composed of a freeze-driable solvent and
at least one solid inorganic substance or carbon, is rather close to the concepts used
in a number of recent papers on the synthesis and processing of inorganic materials.
None of these products are true gels; indeed, some of them have never been gels.
Nevertheless, most of these products have several common features that will be
described in this brief review. Following the well-known approach “It doesn’t
matter whether a cat is white or black, as long as it catches mice” [11], the review
will focus on the most interesting examples of cryogel applications in the synthesis
and processing of inorganic materials during the last 6–7 years.
224
O.A. Shlyakhtin
electrical conductivity.
Keywords Freeze-drying synthesis • Co-precipitation • Nanoparticle isolation •
Oriented porosity • Carbon cryogel
Abbreviations
CNT
Carbon nanotubes
FESEM Field emission SEM
GO
Graphene oxide
HAP
Hydroxyapatite
RGO
Reduced graphene oxide
RF
Resorcinol-formaldehyde
SEM
Scanning electron microscopy
TEM
Transmission electron microscopy
1 Introduction
The term “cryogel” was first introduced into the field of inorganic materials by
Klvana and Pajonk [1–3], who considered cryogels, together with xerogels and
aerogels, as one of the possible drying products of SiO 2 .nH 2 O- and Al 2 O 3 .nH 2 Obased hydrogels. In their experiments, freezing and freeze-drying of wet gels were
used to avoid pore collapse due to the extreme surface tension effects of water
removal during atmospheric drying and to retain most of the tiny morphological
features of gels in the dried state. As the term “cryogel” is most commonly used in
papers on inorganic materials obtained by freeze-drying [4–6], it will be used here
to be consistent with previous studies in this field. Therefore, the first studies on the
synthesis of inorganic cryogels go back to the early 1970s [7–9], soon after the
discovery of the freeze-drying synthesis of inorganic materials from frozen aqueous
solutions by Landsberg and Campbell [10].
This “extended” approach, whereby a cryogel is considered as the freeze-drying
product of any frozen liquid–solid system composed of a freeze-driable solvent and
at least one solid inorganic substance or carbon, is rather close to the concepts used
in a number of recent papers on the synthesis and processing of inorganic materials.
None of these products are true gels; indeed, some of them have never been gels.
Nevertheless, most of these products have several common features that will be
described in this brief review. Following the well-known approach “It doesn’t
matter whether a cat is white or black, as long as it catches mice” [11], the review
will focus on the most interesting examples of cryogel applications in the synthesis
and processing of inorganic materials during the last 6–7 years.
224
O.A. Shlyakhtin