Sánchez del Río, Manuel and Boccaleri, Enrico and Milanesio, Marco and Croce, Gianluca and Beek, Wouter van and Tsiantos, Constantinos and Chyssikos, Georgios D. and Gionis, Vassilis and Kacandes, Georges H. and Súarez Barrios, Mercedes and García Romero, Emilia (2009) A combined synchrotron powder diffraction and vibrational study of the thermal treatment of palygorskite–indigo to produce Maya blue. Journal of materials science, 44 . pp. 5524-5536. ISSN 0022-2461
Official URL: http://www.springer.com/materials/journal/10853
The heating process (30–200 ºC) of a palygorskite- indigo mixture has been monitored in situ and simultaneously by synchrotron powder diffraction and Raman spectroscopy. During this process, the dye and the clay interact to form Maya blue (MB), a pigment highly resistant to degradation. It is shown that the formation of a very stable pigment occurs in the 70–130 ºC interval; i.e., when palygorskite starts to loose zeolitic water, and is accompanied by a reduction of the crystallographic a parameter, as well as by alterations in the C=C and C=O bonds of indigo. Mid- and near-infrared spectroscopic work and microporosity measurements, employed to study the rehydration process after the complex formation, provide evidence for the inhibition of the rehydration of MB as compared with palygorskite. These results are consistent with the blocking of the palygorskite tunnel entrance by indigo molecules with a possible partial penetration inside the tunnels. The surface silanols of palygorskite are not perturbed by indigo, suggesting that MB is not a surface complex.
|Uncontrolled Keywords:||Palygorskite–indigo; Maya blue; Diffraction and Raman spectroscopy|
|Subjects:||Sciences > Geology > Mineralogy|
|Deposited On:||25 Oct 2011 13:36|
|Last Modified:||25 Oct 2011 13:36|
Repository Staff Only: item control page