Monolithic and shrinkage-free hydrophobic silica aerogels via new rapid supercritical extraction process

D. B. Mahadik, Yoon Kwang Lee, N. K. Chavan, S. A. Mahadik, Hyung Ho Park

Research output: Contribution to journalArticle

35 Citations (Scopus)

Abstract

Aerogels have unusual mechanical and thermal properties and are useful in thermal insulation applications. However, aerogel production can be a tedious process if aerogels are made using supercritical extraction of a solvent from a sol-gel matrix. We employ a new rapid and simple supercritical extraction process that is better than conventional methods. This technique relies on rapid heating of the sol in a confined mold under a 50 bar initial pressure supplied by dry N2 gas in an autoclave. The initial pre-pressure of N2 gas and base catalyst concentration dictate whether aerogels or xerogels are formed. A model is presented based on the various experimental results that predicts that gelation occurred after the solvent reached a supercritical state. Aerogels produced using this new rapid supercritical extraction process are monolithic, shrinkage-free, have a prescribed shape and size, and possess high surface area (∼800 m2/g) and low thermal conductivity (∼0.035-0.041 W/(m K)). The hydrophobicity as measured by water contact angle was enhanced from 119° to 158° using a hydrophobic co-precursor in the sol.

Original languageEnglish
Pages (from-to)84-91
Number of pages8
JournalJournal of Supercritical Fluids
Volume107
DOIs
Publication statusPublished - 2016 Jan 1

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry

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