In recent years, reports on ultralow density aerogels are increasing. Our boehmite nanofiber (BNF) aerogels are ultralight materials that have ultralow density and high visible-light transmittance.
Because the refractive index is very low, it seems as if the object on the AlOOH aerogel is floating. In fact, the idea of this research is that I wanted to create a model like a hover board by applying the optical properties.
The fabrication method of these amaterials is simple. Just add base to gelate a BNF dispersion sol (commercially available), exchange solvent, then do supercritical drying.
Since the nanofiber structure has a rough surface, water and oil are repelled well after simple surface treatment with perfluoroalkylsilane (FAS).
We succeeded in fabricating transparent porous cryogel beads like BNF aerogel by vacuum freeze drying method. The boehmite nanofiber sol (in which the dispersion medium is tert-butyl alcohol) is dropped directly into liquid nitrogen to freeze instantly to prevent structural destruction caused by crystal growth of the dispersion medium, and dried under vacuum.
The final product has ultralow density and highly transparent. Interestingly, it is possible to directly observe the state of drying.
By freezing a wet gel consisting of a diluted framework, it was also possible to obtain millimeter-thick transparent monoliths. It can be applied to light emitters with fluorescent molecules added.
Although there are issues such as deterioration of optical properties and low yield when compared with aerogels by supercritical drying, It is an advantage that a transparent cryogels can be obtained by the simple process.
- [Open Access] Gen Hayase, Kazuya Nonomura, George Hasegawa, Kazuyoshi Kanamori, and Kazuki Nakanishi, “Ultralow-Density, Transparent, Superamphiphobic Boehmite Nanofiber Aerogels and Their Alumina Derivatives”, Chem. Mater. 2015, 27, 1, 3–5. doi:10.1021/cm503993n
- Gen Hayase, “Facile fabrication of ultralow-density transparent boehmite nanofiber cryogel beads and their application to a nanoglue”, ChemNanoMat 2017, 3, 3, 168–171. doi:10.1002/cnma.201600360
- [Open Access (Sample Issue)]Gen Hayase, Takuya Funatomi, Kota Kumagai “Ultralow-Bulk-Density Transparent Boehmite Nanofiber Cryogel Monoliths and Their Optical Properties for a Volumetric Three-Dimensional Display”, ACS Applied Nano Materials 2018, 1, 1, 26–30. doi:10.1021/acsanm.7b00097