XRD and NMR of Geopolymers

In his message posted in the topic how to separate neat geopolymer , Dr. Zhang Yunsheng (zhangys) from Southeast University, Hong Kong, China, wrote:

However, there is always some amount of metakaolin that is consumed with reference to XRD, IR and MAS-NMR spectral.

X-ray diffraction of geopolymers of the Na-PSS, K-PSS, (Na,K)-PSS types, are rather boring because they are amorphous by XRD. We get an amorphous diagram. Details are given in Prof. Davidovits’ book Geopolymer Chemistry & Applications, Chapter 4.

What you see in XRD are not remains of the raw-material (in this case the so-called metakaolin), but of the crystalline elements, which are always found in it, for example: muscovite, titanium oxide, quartz, etc. These elements do not take part in the geopolymerization.

As for 27Al NMR, the spectrum does not contain any Al(V) and Al(VI) sites, exclusively Al(IV). If you find remains of the so-called metakaolin, i.e. Al(V-VI), this means that your experimental conditions are not appropriate.

Prof. Dr. Joseph Davidovits.