Environmental Engineering Reference
In-Depth Information
1.4.7.3 Surface Synthesis
When a material is supported on the surface of a support, the resulting
composite material is expected that presents improved properties such as
mechanical performance, thermal stability and a high degree of dispersion.
Some surface synthesis has been reported [74-76] using aqueous ammonia
and precipitating agent urea or by impregnation of metallic salts following
calcinations and hydrothermal treatment [77-79].
Various methods for the synthesis of LDHs can be used. h e choice
of the method will depend on the characteristics and application of the
required material.
1.5
Characterization of Layered Double Hydroxides
Many physico-chemical techniques have been used to characterize LDHs.
Some of the most commonly used techniques are XRD, FTIR and TG/
DTA. Some other techniques are more specii c for some LDHs such as
SEM, DSC, NMR and Raman spectroscopy.
1.5.1 X-ray Dif raction
X-ray dif raction ( XRD) is the main analytical technique for characteriza-
tion of LDHs and crystalline phases. It is also used to determine the inter-
layer spacing and thickness of a single layer. h e technique involves directing
X-rays to the crystal. h e radiation will be either rel ected or dif racted at
dif erent angles. h is technique is used to study the purity of the LDH inter-
calated material. h e phase purity of the material is determined by the sharp-
ness and/or the broadness of the dif raction peaks. h e broader rel ections
correspond to the amorphous phase, while the sharper rel ections corre-
spond to the crystalline phase. From the dif raction data, the d-spacing of
the intercalated LDH material can be determined. h e rel ections with the
greatest d-spacing correspond to the d-spacing of the intercalated LDH [80].
1.5.2
Fourier Transform Infrared Spectroscopy
Fourier transform infrared spectroscopy (FTIR) is one of the molecular
vibrational spectroscopic techniques used for both qualitative and quan-
titative analysis [81]. h e FTIR analysis is not a diagnostic tool for LDHs,
but can be useful to identify the presence of foreign anions in the interlayer
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