III. Hello, when explaining the preparation process of aerogels, the term ??sol??gel method?? is often mentioned. What exactly is the sol??gel method? Could you provide a systematic explanation of this chemical concept, describe the role it plays in the preparation of aerogels, and also outline what other products can be manufactured using the sol??gel method besides aerogels?
1. Definition
The Sol??Gel Process is a versatile chemical method that transforms a system from a liquid (solution or sol) into a solid network (gel) through hydrolysis and condensation reactions.
路 Sol: A colloidal suspension of nanoparticles (1??100 nm) uniformly dispersed in a liquid.
路 Gel: As reactions proceed, particles aggregate and interconnect, forming a three-dimensional network that traps liquid inside the pores.
In essence, it is a liquid ?? colloid ?? solid porous network transformation.
2. Role in Aerogel Preparation
Aerogel preparation involves three main stages:
锛?1锛?Sol formation: Precursors such as metal alkoxides (e.g., TEOS) undergo hydrolysis and condensation to form a nanoparticle-containing sol.
锛?2锛?Gelation: The sol gradually evolves into a three-dimensional gel network, with liquid still occupying the pores.
锛?3锛?Drying: The liquid in the pores is removed by supercritical drying or ambient pressure drying, preserving the fragile gel network and yielding a highly porous solid ?? the aerogel.
In aerogel synthesis, the sol??gel process is the foundation that builds the nanoporous skeleton, directly influencing pore size, surface area, and performance.
3. Other Applications
Beyond aerogels, the sol??gel process is widely applied in advanced materials:
路 Optical & electronic materials: optical coatings, antireflective films, waveguides, semiconductor oxides.
路 Ceramics: high-purity, ultrafine ceramic powders and ceramic coatings.
路 Catalysts & adsorbents: porous oxides with large surface area for catalysis and pollutant removal.
路 Biomedical materials: drug delivery systems, bioactive glasses.
路 Protective coatings: high-temperature coatings, thermal barrier layers, and fire-retardant coatings.
