Thermal behavior of kaolinite–urea intercalation complex and molecular dynamics simulation for urea molecule orientation

Liu, Qinfu, Zhang, Shuai, Cheng, Hongfei, Wang, Ding, Li, Xiaoguang, Hou, Xinjuan, & Frost, Ray L. (2014) Thermal behavior of kaolinite–urea intercalation complex and molecular dynamics simulation for urea molecule orientation. Journal of Thermal Analysis and Calorimetry, 117(1), pp. 189-196.

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Abstract

The thermal behavior of kaolinite–urea intercalation complex was investigated by thermogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). In addition, the interaction mode of urea molecules intercalated into the kaolinite gallery was studied by means of molecular dynamics simulation. Three main mass losses were observed at 136 °C, in the range of 210–270 °C, and at 500 °C in the TG–DSC curves, which were, respectively, attributed to (1) melting of the surface-adsorbed urea, (2) removal of the intercalated urea, and (3) dehydroxylation of the deintercalated kaolinite. The three DSC endothermic peaks at 218, 250, and 261 °C were related to the successive removals of intercalated urea with three different distribution structures. Based on the angle between the dipole moment vector of urea and the basal surface of kaolinite, the three urea models could be described as follows: (1) Type A, the dipole moment vector is nearly parallel to the basal surface of kaolinite; (2) Type B, the dipole moment vector points to the silica tetrahedron with the angle between it and the basal surface of kaolinite ranging from 20°to 40°; and (3) Type C, the dipole moment vector is nearly perpendicular to the basal surface of kaolinite. The three distribution structures of urea molecules were validated by the results of the molecular dynamics simulation. Furthermore, the thermal behavior of the kaolinite–urea intercalation complex investigated by TG–DSC was also supported by FTIR and XRD analyses.

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ID Code: 83614
Item Type: Journal Article
Refereed: Yes
Keywords: Kaolinite, Urea, Intercalation, Thermal Behavior, Molecular dynamics simulation
DOI: 10.1007/s10973-014-3646-1
ISSN: 1588-2926
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2014 Akademiai Kiado, Budapest, Hungary
Deposited On: 16 Apr 2015 00:29
Last Modified: 16 Apr 2015 00:29

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