Towards High Surface Area α-Al₂O₃-Mn-Assisted Low Temperature Transformation

Area of Science:

• Materials Science
• Solid-State Chemistry

Background:

• Gamma-alumina (γ-Al2O3) is a common transition alumina.
• Conversion to alpha-alumina (α-Al2O3, corundum) typically requires high temperatures.
• Energy-efficient synthesis routes for α-Al2O3 are desirable.

Purpose of the Study:

• Investigate manganese-assisted conversion of γ-Al2O3 to α-Al2O3.
• Determine the feasibility of low-temperature corundum formation.
• Characterize the resulting α-Al2O3 properties.

Main Methods:

• X-ray Diffraction (XRD) for phase analysis.
• Solid-state 27Al-Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) spectroscopy.
• Post-synthetic acid treatment (HCl) for manganese removal.
• Thermal stability testing at 750°C for 7 days.

Main Results:

• Successful conversion of γ-Al2O3 to α-Al2O3 at 800°C using manganese assistance.
• Obtained α-Al2O3 with a high specific surface area (56 m² g⁻¹).
• Residual manganese removed effectively via HCl treatment.
• Synthesized porous corundum showed decreased porosity upon prolonged heating.

Conclusions:

• Manganese facilitates energy-saving conversion of γ-Al2O3 to α-Al2O3 at 800°C.
• The synthesized α-Al2O3 exhibits high surface area.
• Porosity stability at elevated temperatures remains a consideration for corundum applications.