(Fig. 10) signals occurred at 38 ppm, 8 ppm
and 14 ppm, which were assigned to aluminates in different AleO
coordination: AlO4, AlO5 and AlO6, respectively. The peak observed at
38 ppm, which is dominant, is the typical signal for aluminium
phosphate AlPO4. The shape of the signals suggests the amorphous
nature of those structures, which most probably form a network. In
this combination residue formation was very poor and none of the
formed aluminates was able to form a sufficient protection barrier.
The 27Al NMR signal ratios changed when additional components
were added. Additionally, the shape of the signals was narrower,
suggesting that the structure was more ordered, similar to
crystalline structures. To better distinguish all signals and to estimate
distances between various Al atoms in different structural
units to the surrounding P atoms, 27Al(31P) REDOR NMR was used