Pseudomorphism in xonotlite and tobermorite with Co<sup>2+</sup> and Ni<sup>2+</sup> exchange for Ca<sup>2+</sup> at 25°C: Fid-Bau Portal

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Pseudomorphism in xonotlite and tobermorite with Co²⁺ and Ni²⁺ exchange for Ca²⁺ at 25°C

Komarneni, Sridhar / Roy, Rustum / Roy, Della M.

AbstractExchange of Co²⁺ and Ni²⁺ for Ca²⁺ in xonotlite and tobermorite was investigated at 25°C. We show here for the first time that all the Ca²⁺ in xonotlite and tobermorite can be stoichiometrically exchanged with Co²⁺ or Ni²⁺. For example, 92.8 and 92.6% of the total Ca²⁺ present in zonotlite and tobermorite respectively, were exchanged by Co²⁺. This type of almost complete exchange of Ca²⁺ by Co²⁺ or Ni²⁺ did not result in the destruction of the crystal morphology of xonotlite and tobermorite which suggested a pseudomorphism. Studies of the kinetics of Co²⁺ exchange by xonotlite and tobermorite showed that the exchange is slow and total exchange of Ca²⁺ by Co²⁺ takes place in about 4–5 days. The Co²⁺ or Ni²⁺ exchange for Ca²⁺ is slow because of the necessity to break Ca-O bonds from the xonotlite and tobermorite structures. Partial Ca²⁺ exchange with Co²⁺ did not lead to a loss of all crystallinity while total exchange led to amorphization as detected by XRD.

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Pseudomorphism in xonotlite and tobermorite with Co²⁺ and Ni²⁺ exchange for Ca²⁺ at 25°C

Komarneni, Sridhar / Roy, Rustum / Roy, Della M.

AbstractExchange of Co²⁺ and Ni²⁺ for Ca²⁺ in xonotlite and tobermorite was investigated at 25°C. We show here for the first time that all the Ca²⁺ in xonotlite and tobermorite can be stoichiometrically exchanged with Co²⁺ or Ni²⁺. For example, 92.8 and 92.6% of the total Ca²⁺ present in zonotlite and tobermorite respectively, were exchanged by Co²⁺. This type of almost complete exchange of Ca²⁺ by Co²⁺ or Ni²⁺ did not result in the destruction of the crystal morphology of xonotlite and tobermorite which suggested a pseudomorphism. Studies of the kinetics of Co²⁺ exchange by xonotlite and tobermorite showed that the exchange is slow and total exchange of Ca²⁺ by Co²⁺ takes place in about 4–5 days. The Co²⁺ or Ni²⁺ exchange for Ca²⁺ is slow because of the necessity to break Ca-O bonds from the xonotlite and tobermorite structures. Partial Ca²⁺ exchange with Co²⁺ did not lead to a loss of all crystallinity while total exchange led to amorphization as detected by XRD.

Pseudomorphism in xonotlite and tobermorite with Co²⁺ and Ni²⁺ exchange for Ca²⁺ at 25°C

Komarneni, Sridhar / Roy, Rustum / Roy, Della M.

AbstractExchange of Co²⁺ and Ni²⁺ for Ca²⁺ in xonotlite and tobermorite was investigated at 25°C. We show here for the first time that all the Ca²⁺ in xonotlite and tobermorite can be stoichiometrically exchanged with Co²⁺ or Ni²⁺. For example, 92.8 and 92.6% of the total Ca²⁺ present in zonotlite and tobermorite respectively, were exchanged by Co²⁺. This type of almost complete exchange of Ca²⁺ by Co²⁺ or Ni²⁺ did not result in the destruction of the crystal morphology of xonotlite and tobermorite which suggested a pseudomorphism. Studies of the kinetics of Co²⁺ exchange by xonotlite and tobermorite showed that the exchange is slow and total exchange of Ca²⁺ by Co²⁺ takes place in about 4–5 days. The Co²⁺ or Ni²⁺ exchange for Ca²⁺ is slow because of the necessity to break Ca-O bonds from the xonotlite and tobermorite structures. Partial Ca²⁺ exchange with Co²⁺ did not lead to a loss of all crystallinity while total exchange led to amorphization as detected by XRD.

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Title:

Pseudomorphism in xonotlite and tobermorite with Co²⁺ and Ni²⁺ exchange for Ca²⁺ at 25°C

Contributors:

Komarneni, Sridhar (author) / Roy, Rustum (author) / Roy, Della M. (author)

Published in:

Cement and Concrete Research ; 16 ; 47-58

Publication date:

1986-01-01

Size:

12 pages

ISSN:

DOI:

https://doi.org/10.1016/0008-8846(86)90067-0

Type of media:

Article (Journal)

Type of material:

Electronic Resource

Language:

English

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