Experimental deconvolution of depressurization from capillary shrinkage during drying of silica wet-gels with SCF CO2 why aerogels shrink?

  • Chandana Mandal
  • Suraj Donthula
  • Parwani M. Rewatkar
  • Chariklia Sotiriou-LeventisEmail author
  • Nicholas LeventisEmail author
Original Paper: Nano- and macroporous materials (aerogels, xerogels, cryogels, etc.)


Silica aerogels are prepared by drying wet-gels under conditions that eliminate surface tension forces, typically by exchanging the pore-filling solvent with liquid or supercritical fluid (SCF) CO2 that is vented off like a gas. Thereby, silica wet-gels should not shrink during drying, but they do. According to the literature, most shrinkage (~71%) happens during depressurization of the autoclave. Here, based on prior literature, and working with wet-gels obtained via base-catalyzed gelation of tetramethylorthosilicate (TMOS), the basic hypothesis was that depressurization shrinkage takes place at the primary/secondary particle level. For this to happen there has to be available space to accommodate merging secondary particles, and a driving force. Secondary particles are mass fractals (by SAXS) and their empty space can accommodate primary particles from neighboring assemblies. The driving force was assumed to be H-bonding developing between surface silanols as soon as all fluids are removed from the pores. That hypothesis was put to test by replacing gelation solvents with nonhydrogen bonding toluene or xylene. Indeed, while the total drying shrinkage of toluene- or xylene-filled wet-gels was equal to that observed with aerogels obtained from acetone-filled wet-gels (~8–9%), the major part of that shrinkage (~74%) was transferred to the wet-gel stage. The remaining shrinkage (~26%) was assigned to interfacial tension forces between the pore-filling solvent and liquid or SCF CO2. Having transferred the major part of drying shrinkage to the wet-gel stage has technological implications, because it is easier to manipulate gels at that stage. Furthermore, our results underline that optimization of the drying process should take into account the fact that drying of silica wet-gels into aerogels is a two-stage moving boundary problem.


  • The major part of the shrinkage during drying silica wet-gels to aerogels with SCF CO2 is associated with the depressurization phase of the drying process.

  • A part of the shrinkage equal to that reported as depressurization shrinkage (70–75%) has been transferred to the wet-gel phase of processing.

  • The remaining part of the drying shrinkage has been assigned to interfacial tension.

  • The practical significance of those findings is related to the fact that it is easier to control shrinkage at the wet-gel phase of processing.

  • From a theoretical perspective, drying with SCF CO2 is a two-stage moving boundary problem.


Silica Wet-gel Aerogel Shrinkage Solvent exchange Toluene 



We thank the NSF under award no. 1530603 for financial support. We also thank Prof. Marc Hodes of Tufts University for fruitful discussions and the Materials Research Center of the Missouri University of Science and Technology for support with materials characterization.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Supplementary material

10971_2019_5124_MOESM1_ESM.pdf (4.9 mb)
Supplementary Information


  1. 1.
    Pierre AC, Pajonk GM (2012) Chem Rev 102:4243–4265CrossRefGoogle Scholar
  2. 2.
    Kistler SS (1931) Nature 127:741–741CrossRefGoogle Scholar
  3. 3.
    Smith DM, Scherer GW, Anderson JM (1995) J Non-Cryst Solids 188:191–206CrossRefGoogle Scholar
  4. 4.
    Kirkbir F, Murata H, Meyers D, Chaudhuri SR (1998) J Non-Cryst Solids 225:14–18CrossRefGoogle Scholar
  5. 5.
    Iswar S, Malfait WJ, Balog S, Winnefeld F, Lattuada M, Koebel MM (2017) Microporous Mesoporous Mater 241:293–302CrossRefGoogle Scholar
  6. 6.
    Satha H, Atamnia K, Despetis F (2013) J Biomater Nanobiotechnol 4:17–21CrossRefGoogle Scholar
  7. 7.
    Hæreid S, Nilsen E, Ranum V, Einarsrud MA (1997) J Sol-gel Sci Technol 8:153–157Google Scholar
  8. 8.
    Mohite DP, Larimore ZJ, Lu H, Mang JT, Sotiriou-Leventis C, Leventis N (2012) Chem Mater 24:3434–3448CrossRefGoogle Scholar
  9. 9.
    Leventis N (2007) Acc Chem Res 40:874–884CrossRefGoogle Scholar
  10. 10.
    Leventis N, Sotiriou-Leventis C, Zhang G, Rawashdeh A-MM (2002) Nano Lett 2:957–960CrossRefGoogle Scholar
  11. 11.
    He F, Zhao H, Qu X, Zhang C, Qiu W (2009) J Mater Process Technol 209:1621–1626CrossRefGoogle Scholar
  12. 12.
    Reichenauer G (2004) J Non-Cryst Solids 350:189–195CrossRefGoogle Scholar
  13. 13.
    Mitsiuk BM, Vysotsky ZZ, Polyakov MV (1964) Dokl Akad Nauk SSSR 155:1404–1406Google Scholar
  14. 14.
    Stein DJ, Maskara A, Hæreid S, Anderson J, Smith DM (1994) In: Cheetham AK, Brinker CJ, Mecartney MA, Sanchez C (eds) Better Ceramics Through Chemistry VI. Materials Research Society: Pittsburgh, PA, p 643–648Google Scholar
  15. 15.
    Rao AV, Bhagat SD, Hirashima H, Pajonk GM (2006) J Colloid Inter Sci 300:279–285CrossRefGoogle Scholar
  16. 16.
    Kanamori K, Aizawa M, Nakanishi K, Hanada T (2007) Adv Mater 19:1589–1593CrossRefGoogle Scholar
  17. 17.
    Prakash SS, Brinker CJ, Hurd AJ, Rao SM (1995) Nature 374:439–443CrossRefGoogle Scholar
  18. 18.
    Rangarajan B, Lira CT (1992) Mat Res Soc Symp Proc 271:559–566CrossRefGoogle Scholar
  19. 19.
    Bohannan EW, Gao X, Gaston KR, Doss CD, Sotiriou-Leventis C, Leventis N (2002) J Sol-gel Sci Technol 23:235–245.Google Scholar
  20. 20.
    Mandal C, Donthula S, Soni R, Bertino M, Sotiriou-Leventis C, Leventis N (2019a) J Sol-gel Sci Technol 90:127–139CrossRefGoogle Scholar
  21. 21.
    Mandal C, Donthula S, Majedi Far H, Saeed AM, Sotiriou-Leventis C, Leventis N (2019b) J Sol-gel Sci Technol 92:84–100CrossRefGoogle Scholar
  22. 22.
    Snook IK, van Megan W (1981) J Chem Soc Faraday Trans 2 77:181–190CrossRefGoogle Scholar
  23. 23.
    van Megan W, Snook IK (1979) J Chem Soc Faraday Trans 2 75:1095–1102CrossRefGoogle Scholar
  24. 24.
    Ash SG, Everett DH, Radke C (1973) J Chem Soc Faraday Trans 2 69:1256–1277CrossRefGoogle Scholar
  25. 25.
    Dahmouche K, Santilli CV, Chaker JA, Pulcinelli SH, Craievich AF (1999) J Appl Phys 38:172–175CrossRefGoogle Scholar
  26. 26.
    Kawaguchi T, Hishikura H, Iura J (1988) J Non-Cryst Solids 100:220–225CrossRefGoogle Scholar
  27. 27.
    Mohite DP, Mahadik-Khanolkar S, Luo H, Lu H, Sotiriou-Leventis C, Leventis N (2013) Soft Matter 9:1531–1539CrossRefGoogle Scholar
  28. 28.
    Leventis N, Elder IA, Rolison DR, Anderson ML, Merzbacher CI (1999) Chem Mater 11:2837–2845CrossRefGoogle Scholar
  29. 29.
    Rewatkar PM, Taghvaee T, Saeed AM, Donthula S, Mandal C, Chandrasekaran N, Leventis T, Shruthi TK, Sotiriou-Leventis C, Leventis N (2018) Chem Mater 30:1635–1647CrossRefGoogle Scholar
  30. 30.
    Cabrera Y, Cabrera A, Larsen FH, Felby C (2016) Holzforschung 70:709–718Google Scholar
  31. 31.
    Ilavsky J, Jemian PR (2009) J Appl Cryst 42:347–353CrossRefGoogle Scholar
  32. 32.
    Beaucage G (1995) J Appl Crystallogr 28:717–728CrossRefGoogle Scholar
  33. 33.
    Beaucage G (1996) J Appl Crystallogr 29:134–146CrossRefGoogle Scholar
  34. 34.
    Mang JT, Son SF, Hjelm RP, Peterson PD, Jorgensen BS (2007) J Mater Res 22:1907–1920CrossRefGoogle Scholar
  35. 35.
    Agbabiaka A, Wiltfong M, Park C (2013) J Nanomater 640436,
  36. 36.
    Potton JA, Daniell GJ, Rainford BD (1998) J Appl Cryst 21:891–897CrossRefGoogle Scholar
  37. 37.
    Tatchev D, Kranold R (2004) J Appl Crystallogr 37:32–39CrossRefGoogle Scholar
  38. 38.
    Winter HH (1987) Polym Eng Sci 27:1698–1702CrossRefGoogle Scholar
  39. 39.
    Kim S-Y, Choi D-G, Yang S-M (2002) Korean J Chem Eng 19:190–196CrossRefGoogle Scholar
  40. 40.
    Raghavan SR, Chen LA, McDowell C, Khan SA, Hwang R, White S (1996) Polymer 37:5869–5875CrossRefGoogle Scholar
  41. 41.
    Muthukumar M (1989) Macromolecules 22:4656–4658CrossRefGoogle Scholar
  42. 42.
    KjØniksen A-L, Nyström B, Lindman B (1998) Macromolecules 31:1852–1858CrossRefGoogle Scholar
  43. 43.
    Borba A, Vareda JP, Durães L, Portugal A, Simões PN (2017) New J Chem 41:6742–6759CrossRefGoogle Scholar
  44. 44.
    Brinker CJ, Scherer GW (1990) Sol-gel science: The physics and chemistry of sol-gel processing, Chap 3. Academic Press Inc, San Diego, CA, p 97–233Google Scholar
  45. 45.
    Graf C (2018) Silica, Amorphous in Kirk-Othmer Encyclopedia of Chemical Technology, 5th edn. John Wiley & Sons, New York, NY, p 7Google Scholar
  46. 46.
    Innocenzi P (2003) J Non-Cryst Solids 316:309–319CrossRefGoogle Scholar
  47. 47.
    Bertoluzza A, Fagnano C, Morelli MA, Gottardi V, Guglielmi M (1982) J Non-Cryst Solids 48:117–128CrossRefGoogle Scholar
  48. 48.
    Almeida RM, Pantano CG (1990) J Appl Phys 68:4225–4232CrossRefGoogle Scholar
  49. 49.
    Chen J, Li T, Li X, Chou K, Hou X (2017) High Temp Mater Proc 36:607–613Google Scholar
  50. 50.
    McDonald RS (1958) J Am Chem Soc 62:1168–1178Google Scholar
  51. 51.
    Wu MK (1996) Aerosol Sci Technol 25:392–398CrossRefGoogle Scholar
  52. 52.
    Pirard R, Blacher S, Brouers F, Pirard JP (1995) J Mater Res 10:2114–2119CrossRefGoogle Scholar
  53. 53.
    Pfeifer P, Avnir D (1983) J Chem Phys 79:3558–3565CrossRefGoogle Scholar
  54. 54.
    Celis R, Cornejo J, Hermosin MC (1996) Clay Min 31:355–363CrossRefGoogle Scholar
  55. 55.
    Kobersein JT, Morra B, Stein RS (1980) J Appl Cryst 13:34–45CrossRefGoogle Scholar
  56. 56.
  57. 57.
  58. 58.
  59. 59.
    Majedi Far H, Rewatkar PM, Donthula S, Taghvaee T, Saeed AM, Sotiriou-Leventis C, Leventis N (2019) Macromol Chem Phys 220:1800333CrossRefGoogle Scholar
  60. 60.
    Saeed AM, Rewatkar PM, Majedi Far H, Taghvaee T, Donthula S, Mandal C, Sotiriou-Leventis C, Leventis N (2017) ACS Appl Mater Interfaces 9:13520–13536CrossRefGoogle Scholar
  61. 61.
    García-Gonzáleza CA, Camino-Reva MC, Alnaief M, Zetzl C, Smirnova I (2012) J Supercrit Fluids 66:297–306CrossRefGoogle Scholar
  62. 62.
    Ozbakr Y, Erkey C (2015) J Supercrit Fluids 98:153–166CrossRefGoogle Scholar
  63. 63.
    Lebedev AE, Katalevich AM, Menshutina NV (2015) J Supercrit Fluids 105:122–132CrossRefGoogle Scholar
  64. 64.
    Karamanis G, Dinh H, Waisbord N, Hodes M (2018) In: Proceedings of the 16th International Heat Transfer Conference, IHTC16-24239, China National Convention Center, Beijing, ChinaGoogle Scholar

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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of ChemistryMissouri University of Science & TechnologyRollaUSA

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