Li Xiaoli, Sun Xiao, Zhang Xuguang, Zheng Yi, Minus Marilyn L
Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, 02115, USA.
Department of Chemical Engineering, Northeastern University, Boston, MA, 02115, USA.
Sci Rep. 2024 Nov 1;14(1):26276. doi: 10.1038/s41598-024-77198-9.
The earliest silicon-based aerogels attracted attention due to their nanoscale porous structure and high transparency. Still, they need to be more balanced with the poor mechanical properties. Their brittle structure limits the development of this promising new material. Therefore, the goal of this work is to optimize the mechanical properties of aerogels while maintaining transparency. The good mechanical properties of polymers have made them the material of choice for this work. Polyvinyl alcohol (PVA), which can undergo self-crosslinking through side-chain hydroxyl groups forming hydrogen bonds, was chosen as the raw material to simplify and expedite the production process. The production process was experimented with, analyzed, and refined. Considering the time efficiency of the experimental process, a one-step gelling method was invented to facilitate the sol-gel transition. The one-step gelling method maintained the high transparency of PVA aerogels and reduced the time required for the gelation process compared to the freeze-thawing method. This work employs carbon dioxide supercritical drying to ensure minimal structural collapse and maximize the porous structure's retention. The transmittance of PVA aerogels can reach up to 93.67% at a wavelength of 1333 nm. The internal structure of aerogels with different PVA concentrations was observed using a Scanning electron microscope. Applying Beer-Lambert's Law eliminated the effect of sample thickness on transparency. The relationship between the transparency of PVA aerogels, their microstructure, and macroscopic concentration was studied and analyzed for the first time. While ensuring light transmittance, the modulus of the PVA aerogel reached as high as 6.18 ± 0.56 MPa at 13 wt%.
最早的硅基气凝胶因其纳米级多孔结构和高透明度而备受关注。然而，它们在机械性能方面仍需进一步平衡，其脆性结构限制了这种有前景的新材料的发展。因此，这项工作的目标是在保持透明度的同时优化气凝胶的机械性能。聚合物良好的机械性能使其成为这项工作的首选材料。聚乙烯醇（PVA）可以通过侧链羟基形成氢键进行自交联，被选为原料以简化和加快生产过程。对生产过程进行了实验、分析和优化。考虑到实验过程的时间效率，发明了一种一步凝胶法来促进溶胶 - 凝胶转变。与冻融法相比，一步凝胶法保持了PVA气凝胶的高透明度，并减少了凝胶化过程所需的时间。这项工作采用二氧化碳超临界干燥来确保结构坍塌最小化，并最大限度地保留多孔结构。PVA气凝胶在波长1333nm处的透光率可达93.67%。使用扫描电子显微镜观察了不同PVA浓度气凝胶的内部结构。应用比尔 - 朗伯定律消除了样品厚度对透明度的影响。首次研究和分析了PVA气凝胶的透明度、微观结构和宏观浓度之间的关系。在确保透光率的同时，13wt%的PVA气凝胶模量高达6.18±0.56MPa。
