Skip to main content

Dehydroxylation and Transformations of the 2:1 Phyllosilicate Pyrophyllite at Elevated Temperatures: An Infrared Spectroscopic Study

Buy Article:

$28.00 plus tax (Refund Policy)

Abstract:

The thermally-induced dehydroxylation and transformations of the 2:1 phyllosilicate pyrophyllite have been studied using infrared spectroscopy in the frequency range 350 ­11000 cm ­1 and the temperature range 200 ­1500°C. The dehydroxylation of pyrophyllite to pyrophyllite dehydroxylate occurs between 500 and 900°C. It is characterized by a decrease in the intensity of the OH signals and phonon bands of pyrophyllite and the eventual disappearance of these features as well as the appearance of extra signals related to pyrophyllite dehydroxylate and an intermediate phase. Our results are consistent with previous observations that the SiO4 tetrahedral sheet structure still exists in pyrophyllite dehydroxylate, that the Si ­O ­Al linkages and 2:1 structure remain in the pyrophyllite dehydroxylate, and that AlO5 trigonal bipyramids form. Two extra OH bands at 3690 and 3702 cm ­1 and their overtones at 7208 and 7234 cm ­1 are observed, for the first time, in samples annealed at the temperature range 550 ­900°C. Our results suggest that the formation and dehydroxylation of the extra OH species can be strongly affected by kinetic effects. The experimental evidence shows that the dehydroxylation of pyrophyllite is a two-stage process. The appearance of these additional OH bands is interpreted in terms of an unknown intermediate phase, and may be related to the second endothermic peak observed at high temperatures in DTA experiments. Pyrophyllite dehydroylate decomposes into a Si-rich amorphous phase and mullite in the temperature range 950 ­1100°C. Cristobalite is observed in the temperature range 1150 ­1500°C.

Keywords: -CRISTOBALITE; DEHYDROXYLATION; INTERMEDIATE PHASE; IR SPECTROSCOPY; MULLITE; PYROPHYLLITE DEHYDROXYLATE; TRANSFORMATION.

Document Type: Research Article

DOI: https://doi.org/10.1346/000986002760832874

Publication date: 2002-04-01

More about this publication?
  • The JOURNAL publishes articles of interest to the international community of clay scientists, including but not limited to areas in mineralogy, crystallography, geology, geochemistry, sedimentology, soil science, agronomy, physical chemistry, colloid chemistry, ceramics, petroleum engineering, foundry engineering, and soil mechanics. Clays and Clay Minerals exists to disseminate to its worldwide readership the most recent developments in all of these aspects of clay materials. Manuscripts are welcome from all countries.

    Clays and Clay Minerals is the official publication of The Clay Minerals Society.

    The Editor-in-Chief is Professor Joseph W. Stucki jstucki@illinois.edu

    Publications of The Clay Minerals Society
    Source Clays

  • Editorial Board
  • Information for Authors
  • Membership Information
  • Annual Meeting of The Clay Minerals Society
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
UA-1313315-24
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more