Cryogels freeze-drying

Cryogels Freeze dried Finely divided powder, not suitable for producing monolithic ceramics... 

In the field of carbon nanotubes synthesis, widely studied for the moment, the one-step sol-gel method is examined as a way to prepare bimetallic catalysts leading to a high productivity in single-walled carbon nanotubes (SWNTs). For example, Su et al. [145] prepared a Fe-Mo/AljOj aerogel (dried in supercritical COj) and Mehn et al. [133] prepared a Fe-Mo/AljOj cryogel (freeze-dried) both with a good activity in SWNTs synthesis. 

Freezing-drying methods give rise to cryogels. In this case, the solvent is frozen and then removed by sublimation, avoiding a vapor-liquid interface... 

Some authors have named the polymeric matrices fabricated via conventional freeze-drying by the term cryogels. Certainly, freezing of polymeric solutions or colloidal dispersions causes solid-liquid phase separation, and the subsequent sublimation of the solidified solvent crystals fixes the system thus structured [17, 18], but no gelation occurs during these consecutive steps. Therefore, it is more correct to call such freeze-dried polymeric matrices cryostructurates or cryotexturates rather than cryogels. ... 

Fig. 4 Formation process of a pore by cryogelation (a) and by freeze-drying (b). Red, green, and gray circles represent monovinyl monomers, divinyl monomers, and polymer repeat units, respectively...

Fig. 18 Amide I region of (a) FTIR spectra and (b) X-ray difbnction profile of Ireeze-dried fibroin cryogels. Data obtained by freeze-drying of silk fibroin solutions before gelation are also shown dotted curves). tx) TEMED content (%) 0.07 solid curve), 0.10 long dash), 0.13 short dash), 0.17 short-long), 0.25 dash-dot-dot), 0.33 short-long-short), and 0.50 % dash-dot), (b) TEMED content (%) is indicated on the curves. Tprep = -18 °C Csf = 4.2 wt% EGDE = 20 mmol/g. (From [50] with permission from the American Chemical Society)...

Keywords Freeze-drying synthesis Co-precipitation Nanoparticle isolation Oriented porosity Carbon cryogel... 

---