P-002

Austėja Šernaitė

austeja.sernaite@chgf.stud.vu.lt

Greta Inkrataitė, Ramūnas Skaudžius

Department of Inorganic Chemistry, Vilnius University, Lithuania

Drying speed and shrinkage coefficient significance in the synthesis of crack-free silica xerogels via the sol-gel method

Xerogels are highly porous materials that are obtained via the sol-gel process in which the gel is dried in ambient pressure. Due to their noteworthy characteristics such as high surface area, small pore size and low density, they can find applications in catalysis and have been established as prospects for thermal and acoustic insulation as well as biomedical applications due to low thermal conductivity and potential biocompatibility respectively [1,2].

However, a prevalent problem impacting the widespread usage of xerogels is their tendency to crack during the drying phase due to high capillary action. The present study hypothesizes that the drying speed and shrinkage coefficient of the gel may serve as reliable indicators of whether the xerogel will end up cracked.

In our experimental design, we varied the filling of gel in the containers (10%; 40%; 50% and 90% visually) and the size of holes in the lids of the containers, drilled to regulate the drying speed. All xerogels were synthesized via the acid catalyzed sol-gel method outlined by Skruodiene et al. with minor adjustment to the drying time [3]. The shrinkage coefficient was calculated by dividing the amount of shrinkage height-wise by the amount of shrinkage width-wise. The experimental results demonstrate that both these variables have an impact, however one more crucial factor for achieving no cracks was found to be the pouring of the gel into the containers and transferring them to the ultrasound bath. It is imperative that there is as little amount of air bubbles as possible. The findings indicate that the most effective method for producing crack-free xerogels is to perforate the lid with a 4 mm wide aperture in the middle and to fill the container with a quantity of gel such that the shrinkage coefficient is approximately equal to any of these numbers: 0.44 (40%), 0.55 (50%), 0.61 (50%), 0.69 (50%), 1.03 (90%).

References

[1] N. Gizli, S. S. Çok, and F. Koç, “Aerogel, xerogel, and cryogel: Synthesis, surface chemistry, and properties—Practical environmental applications and the future developments,” Advanced Materials for Sustainable Environmental Remediation: Terrestrial and Aquatic Environments, pp. 195–229, Jan. 2022, doi: 10.1016/B978-0-323-90485-8.00021-7.

[2] M. Catauro et al., “Synthesis of SiO2 and CaO rich calcium silicate systems via sol-gel process: Bioactivity, biocompatibility, and drug delivery tests,” J Biomed Mater Res A, vol. 102, no. 9, pp. 3087–3092, Sep. 2014, doi: 10.1002/JBM.A.34978.

[3] M. Skruodiene et al., “Synthesis and Investigation of Novel Optical Active SiO2 Glasses with Entrapped YAG:Ce Synthesized via Sol–Gel Method,” Gels 2023, Vol. 9, Page 488, vol. 9, no. 6, p. 488, Jun. 2023, doi: 10.3390/GELS9060488.