Pseudomorphism in xonotlite and tobermorite with Co2+ and Ni2+ exchange for Ca2+ at 25°C
1986; Elsevier BV; Volume: 16; Issue: 1 Linguagem: Inglês
10.1016/0008-8846(86)90067-0
ISSN1873-3948
AutoresSridhar Komarneni, Rustum Roy, Della M. Roy,
Tópico(s)Nuclear materials and radiation effects
ResumoAbstract Exchange of Co 2+ and Ni 2+ for Ca 2+ in xonotlite and tobermorite was investigated at 25°C. We show here for the first time that all the Ca 2+ in xonotlite and tobermorite can be stoichiometrically exchanged with Co 2+ or Ni 2+ . For example, 92.8 and 92.6% of the total Ca 2+ present in zonotlite and tobermorite respectively, were exchanged by Co 2+ . This type of almost complete exchange of Ca 2+ by Co 2+ or Ni 2+ did not result in the destruction of the crystal morphology of xonotlite and tobermorite which suggested a pseudomorphism. Studies of the kinetics of Co 2+ exchange by xonotlite and tobermorite showed that the exchange is slow and total exchange of Ca 2+ by Co 2+ takes place in about 4–5 days. The Co 2+ or Ni 2+ exchange for Ca 2+ is slow because of the necessity to break Ca-O bonds from the xonotlite and tobermorite structures. Partial Ca 2+ exchange with Co 2+ did not lead to a loss of all crystallinity while total exchange led to amorphization as detected by XRD.
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