Study of the Microstructure of Amorphous Silica Nanostructures Using High-Resolution Electron Microscopy, Electron...

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Amorphous silica is crucial for industrial and scientific applications.
• Understanding its atomic structure is key to predicting material properties.
• Alkali silica reaction (ASR) significantly alters silica structures.

Purpose of the Study:

• To investigate the structural evolution of amorphous silica during accelerated alkali silica reaction (ASR).
• To correlate structural changes with reaction time using advanced microscopy and spectroscopy techniques.

Main Methods:

• High-resolution transmission electron microscopy (HRTEM) for nanoscale imaging.
• Electron energy loss spectroscopy (EELS) for elemental and chemical state analysis.
• Electron pair distribution function (e-PDF) and X-ray powder diffraction (XRPD) for structural analysis.
• Solid-state nuclear magnetic resonance (NMR) for detailed nanostructure elucidation.

Main Results:

• Observed an increase in amorphous silica nanostructure and nanopore size with ASR progression.
• Detected potential formation of Si-OH surface species.
• Confirmed amorphous nature across all samples via HRTEM, XRPD, and e-PDF.
• Noted a shift in the XRPD diffuse peak towards higher angles with increased reaction time.
• Identified variations in EELS spectral features indicating evolving interactions between oxygen, silicon, and OH ions.

Conclusions:

• ASR induces measurable structural changes in amorphous silica, including altered nanostructure and pore size.
• The combined techniques provide a comprehensive understanding of silica's structural response to ASR.
• Further research can leverage these findings for material design and application optimization.