Article: Effects of Pressure, Thermal Treatment, and O2 Loading in MCM41, MSU-H, and MSU-F Mesoporous Silica Systems Probed by Raman Spectroscopy
The Journal of Physical Chemistry C. 2015 Dec. 10, v. 119, no. 49
2015
Abstract: ... in MCM41, MSU-H, and MSU-F representative mesoporous silica. We compared the starting powders ... the MSU-H Si–O–Si hydrolysis occurs, whereas such a process is absent or much less efficient in the MSU-F ... whereas the MSU-F tablets tend to form the tridymite crystalline phase. Such a finding could be related ...
| Abstract | We present a Raman study of the effects induced by pressure, thermal treatments, and O₂ loading in MCM41, MSU-H, and MSU-F representative mesoporous silica. We compared the starting powders with the mechanically pressed tablets produced applying pressures of ∼0.2 and ∼0.45 GPa. The spectra of the three untreated tablets evidence that the main value of the Si–O–Si angle decreases and that in the MCM41 and the MSU-H Si–O–Si hydrolysis occurs, whereas such a process is absent or much less efficient in the MSU-F. Despite their different networks, the three powders tend to crystallize in cristobalite when treatments are at 1000 °C. The MCM41 and MSU-H tablets exhibit behavior similar to their starting powders, whereas the MSU-F tablets tend to form the tridymite crystalline phase. Such a finding could be related by the differences in the Si–O–Si hydrolysis, occurring during the tablets production. Finally, we inserted O₂ molecules within the interstices of the SiO₂ wall only in MSU-F. By monitoring the O₂ content as a function of the delay time from the loading end, we provide evidence that the O₂ remains in the interstices for a sufficiently large time to modify the material properties by inserting small molecules and not only through the surface functionalization. |
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| Keywords | Raman spectroscopy ; heat treatment ; hydrolysis ; monitoring ; oxygen ; physical chemistry ; porous media ; powders ; silica |
| Language | English |
| Dates of publication | 2015-1210 |
| Size | p. 27434-27441. |
| Publishing place | American Chemical Society |
| Document type | Article |
| ISSN | 1932-7455 |
| DOI | 10.1021%2Facs.jpcc.5b10206 |
| Database | NAL-Catalogue (AGRICOLA) |
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