Fabrication of a carbon nanotube-embedded silicon nitride membrane for studies of nanometer-scale mass transport

Jason K. Holt, Aleksandr Noy, Thomas R Huser, David Eaglesham, Olgica Bakajin

Research output: Contribution to journalArticle

134 Scopus citations

Abstract

Membranes consisting of multiwall carbon nanotubes embedded in a silicon nitride matrix were fabricated for fluid mechanics studies on the nanometer scale. Characterization by tracer diffusion and scanning electron microscopy suggests that the membrane is free of large voids. An upper limit to the diffusive flux of D 2O of 2.4 × 10 -8 mol/m 2 s was determined, indicating extremely slow transport through the membranes. By contrast, hydrodynamic calculations of water flow across a nanotube membrane of similar specifications predict a much higher molar flux of 1.91 mol/m 2 s, suggesting that the nanotubes used in the membrane have a "bamboo" morphology. The carbon nanotube membranes were then used to make nanoporous silicon nitride membranes, which were fabricated by sacrificial removal of the carbon. Nitrogen flow measurements on these structures give a membrane permeance of 4.7 × 10 -4 mol/m 2 s Pa at a pore density of 4 × 10 10 cm -2. Using a Knudsen diffusion model, the average pore size of this membrane is estimated to be 66 nm, which agrees well with TEM observations of the multiwall carbon nanotube outer diameter. These membranes are a robust platform for the study of confined molecular transport, with applications in separations and chemical sensing.

Original languageEnglish (US)
Pages (from-to)2245-2250
Number of pages6
JournalNano Letters
Volume4
Issue number11
DOIs
StatePublished - Nov 2004
Externally publishedYes

ASJC Scopus subject areas

  • Materials Science(all)
  • Electronic, Optical and Magnetic Materials
  • Chemistry (miscellaneous)

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