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Journal of Materials Science

, Volume 29, Issue 17, pp 4481–4486 | Cite as

Synthesis and thermal evolution of structure in alkoxide-derived niobium pentoxide gels

  • N. P. Bansal
Papers

Abstract

Niobium pentoxide gels in the form of transparent monoliths and powder have been synthesized from the controlled hydrolysis and polycondensation of niobium pentaethoxide under different experimental conditions using various mole ratios of Nb(OC2H5)5:H2O:C2H5OH:HCl. Alcohol acted as the mutual solvent and HCl as the deflocculating agent. In the absence of HCl, precipitation of colloidal particles was encountered on the addition of any water to the alkoxide. The gels were subjected to various thermal treatments and characterized by differential thermal analysis, thermogravimetric analysis, X-ray diffraction and infra-red spectroscopy. After drying at 400°C, the gels were amorphous to X-rays. The amorphous powder crystallized into the low temperature orthorhombic form of Nb2O5 at ~ 500°C, which transformed irreversibly into the high temperature monoclinic α-Nb2O5 between 900 to 1000°C. The kinetics of crystallization of the amorphous niobium pentoxide have been investigated by non-isothermal differential scanning calorimetry. The crystallization activation energy was determined to be 399 kJ mol−1.

Keywords

Crystallization Differential Scanning Calorimetry Niobium Differential Thermal Analysis C2H5OH 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman & Hall 1994

Authors and Affiliations

  • N. P. Bansal
    • 1
  1. 1.National Aeronautics and Space AdministrationLewis Research CenterClevelandUSA

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