Hello, I recently characterise pure silica aerogels for XRD patterns, and of course they are amophous has a broad peak at around 22°. However there also is a narrow peak at around 9 or 10 degree, as the figure shown attached. Anyone has the idea where this peak comes from? For example I see some say that is possilbly caused by silicon attached by alkyl group.
Dear Yujing Liu ,
Aerogels may present themselves in several morphological types and associations. Siloxanes and hydrated species are possible.
The x-ray of the sample reminds me of the structure published in A multi-dimensional microporous silicate that is isomorphous to zeolite MCM-68, Koyama Y., Ikeda T., Tatsumi T., Kubota Y., Angew. Chem. Int. Ed, V 47, pg 1042-1046, 2008.
The structure described in the above reference is very crystalline since the CIF file is available; it is worth simulating small particle sizes and evaluate the similarities.
Naturally, your sample has higher disorganization and low particle size, near amorphous; nevertheless, the microporous silicate diffraction (attached) is somehow similar. It is clear the attached diffraction has a larger particle size; however, the similarity at about 10 and just after 20 degrees is worth enough to check.
Best regards,
WNM
Dear Yujing Liu ,
Aerogels may present themselves in several morphological types and associations. Siloxanes and hydrated species are possible.
The x-ray of the sample reminds me of the structure published in A multi-dimensional microporous silicate that is isomorphous to zeolite MCM-68, Koyama Y., Ikeda T., Tatsumi T., Kubota Y., Angew. Chem. Int. Ed, V 47, pg 1042-1046, 2008.
The structure described in the above reference is very crystalline since the CIF file is available; it is worth simulating small particle sizes and evaluate the similarities.
Naturally, your sample has higher disorganization and low particle size, near amorphous; nevertheless, the microporous silicate diffraction (attached) is somehow similar. It is clear the attached diffraction has a larger particle size; however, the similarity at about 10 and just after 20 degrees is worth enough to check.
Best regards,
WNM
Yes dear it is familiar to have such pattern as it clearly assigned to the amorphous structure of either stable or unstable compounds. To verify the case, calcinations at higher temperature will tell whether the peak of 2θ around 10o is belong to a stable compound as part of silica structure or is assigned to the amorphous structure of the residual reactants. I had such case during laboratory studying on the effects of calcination temperatures on the structure of modified nanosilica prepared by sol–gel. I found that at calcination temperature 250oC, only the peak of 2θ =22.05720 appeared indicating the occurrence of silica particles densification and change, while at 125oC the analysis of as produced silica powder revealed two broad peaks within pattern equivalent Bragg angle 2θ =12.0860 and for the second peak 2θ =22.05720
Best regards
Article Investigating the effects of calcination temperatures on the...
Dear Wagner Da Nova Mussel ,
thank you for the idea. Sorry to reply you late. I recently checked many papers that involving carbon group attached silica, basically people don't characterise XRD patterns. Even they do so, few of them to show 2theta before 10°.
Anyway, do you think it is possilbe this peak comes from the functional group attached on silxane structure? Because I think silicate has this Si-O-R and my sample has similar structure as well?
Kind regards.
Dear Yujing Liu ,
It could be possible, depending on the attached group.
Depending on the reaction medium, the -R functional could generate the peak; nevertheless, some other peaks would necessarily be present in a crystalline material. Based on the amorphous sample, I don't believe that is the case.
It looks like to have microporous silica grains. As suggested by Dr. Mohammed Hussein, a heating experiment may destroy the macroporous material structure and give some insights into the original material's interpretation. It is worth trying.
Best regards,
WNM
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