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Title: Ionic interactions in crystallite growth of CoMgAl-hydrotalcite-like compounds
Authors: Xu, Z.P. 
Zeng, H.C. 
Issue Date: 2001
Citation: Xu, Z.P., Zeng, H.C. (2001). Ionic interactions in crystallite growth of CoMgAl-hydrotalcite-like compounds. Chemistry of Materials 13 (12) : 4555-4563. ScholarBank@NUS Repository.
Abstract: With XRD, FTIR, CHN, ICP, and DTA/TGA techniques, ionic interactions in the forms of cation replacement/incorporation in basal layers and anion exchange/insertion in the interlayer space have been investigated. The crystallite size is increased significantly, whereas basal spacing is reduced when Co2+ cations or both Co2+ and Co3+ in CoIICoIII-NO3hydrotalcite-like compound (CoIICoIII-NO3-HT) are replaced with Al3+ or Mg2+ and Al3+. IR vibrational modes of hydroxyl groups and intercalated anions have been utilized in identifying exchanged interlayer species, and thermal events revealed by DTA/TGA have been correlated in verifying compositional changes and ionic interactions. In exchange experiments of CoIICoIII-NO3-HT, aluminum is not only incorporated into the basal layers but is also inserted into the interlayer space (in the form of H2AlO3 -), which causes an increase in planar growth of basal layers (to about 3 times) and a similar increase (to 2-3 times) in the basal layer stacking along the c-axis. Other experiments for CoIIAl-NO3-HT and MgAl-NO3-HT also indicate similar increases in the planar growth (to 2-3 times) when nitrate anions are replaced by aluminate anions, although the extent of increase in layer number in the c-axis is not as high. It appears that stronger cation-to-anion attraction promotes the inter-basal-layer stacking in the c-axis, while smaller anion-to-anion lateral repulsion is beneficial to the intra-basal-layer growth; these can be practically achieved by incorporation of more trivalent cations and/or replacement of low-charged anions with higher charged ones.
Source Title: Chemistry of Materials
ISSN: 08974756
DOI: 10.1021/cm010222b
Appears in Collections:Staff Publications

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