33. Shape-Preserving Chemical Conversion of Self-Assembled 3-D Bioclastic Micro/Nanostructures Via Low-Temperature Displacement Reactions

  1. Dongming Zhu and
  2. Kevin Plucknett
  1. Shawn M. Allan,
  2. Michael R. Weatherspoon,
  3. Phillip D. Graham,
  4. Ye Cai,
  5. Michael S. Haluska,
  6. Robert L. Snyder and
  7. Kenneth H. Sandhage

Published Online: 26 MAR 2008

DOI: 10.1002/9780470291238.ch33

Advances in Ceramic Coatings and Ceramic-Metal Systems: Ceramic Engineering and Science Proceedings, Volume 26, Number 3

Advances in Ceramic Coatings and Ceramic-Metal Systems: Ceramic Engineering and Science Proceedings, Volume 26, Number 3

How to Cite

Allan, S. M., Weatherspoon, M. R., Graham, P. D., Cai, Y., Haluska, M. S., Snyder, R. L. and Sandhage, K. H. (2005) Shape-Preserving Chemical Conversion of Self-Assembled 3-D Bioclastic Micro/Nanostructures Via Low-Temperature Displacement Reactions, in Advances in Ceramic Coatings and Ceramic-Metal Systems: Ceramic Engineering and Science Proceedings, Volume 26, Number 3 (eds D. Zhu and K. Plucknett), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470291238.ch33

Author Information

  1. Georgia Institute of Technology 771 Ferst Drive Atlanta, GA 30332

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 2005

ISBN Information

Print ISBN: 9781574982336

Online ISBN: 9780470291238

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Keywords:

  • protuberances;
  • morphology;
  • parameters;
  • agriculture;
  • magnesium

Summary

An astounding variety of self-assembled, rigid (bioclastic) micro/nanostructures are generated by micro-organisms known as diatoms (single-celled algae). Each diatom species assembles an intricate silica nanoparticle-based microshell (frustule) with a particular three-dimensional (3-D) shape and with specific patterns of nanoscale features (pores, channels, ridges, protuberances, etc.). Sustained reproduction of a single diatom can yield enormous numbers of intricate frustules with identical 3-D shapes and fine features. The massive parallelism and genetic precision of such 3-D nanoparticle self-assembly are highly attractive for device applications. However, in order to expand the use of such micro/nanostructures into a broad range of applications, processes need to be developed to change the silica-based chemistry of diatom frustules into other compositions, so as to achieve a wider variety of properties.

Displacement reactions can be used to convert SiO2-based diatom frustules into other oxides while preserving the 3-D morphology of the starting frustule. In this paper, an oxidation-reduction reaction between Mg gas and SiO2 frustules has been used to convert the frustules into MgO-bearing replicas. The influence of processing parameters (reaction temperatures, times, and reactant ratios) on the nanostructural evolution, and on the final product phases (particularly the secondary Si-bearing phases), has been examined. Nanocrystalline MgO-bearing replicas of diatom frustules have been synthesized at temperatures as low as 650°C within a few hours.