Phase-dependent thermophysical properties of α-and γ-Al2O3 in aqueous suspension

• α-Al2O3 phase always shows higher thermal conductivity and viscosity than γ-Al2O3 phase.
• α-Al2O3 phase shows more dispersion stability than γ-Al2O3 phase.
• Ultra-sonication helps in the breakdown of large cluster to smaller one.
• Temperature is directly proportional to thermal conductivity but inversely proportional to viscosity.
• At lower volume fraction, the suspension shows Newtonian characteristics.

This study demonstrates the thermal conductivity (TC) and viscosity of as prepared crystalline α-Al2O3 and amorphous γ-Al2O3 particles, having size in the range of 30–50 nm. The α and γ-Al2O3 aqueous suspension exhibited ∼10% and 6% enhancement in TC than de-ionized water, but α-Al2O3 showed (∼4–6%) higher TC than γ-Al2O3 aqueous suspension due to more crystallinity of α phase than γ phase. Ultrasonication helps in the breakdown of large clusters which further improves the dispersion stability and TC as verified by dynamic light scattering and zeta potential measurements. The Al2O3 aqueous suspension showed Newtonian characteristics at lower concentration.

The thermal conductivity and viscosity of Al2O3 aqueous suspension was influenced by crystallinity, sonication time, volume fraction, temperature and settling time. The crystalline γ-Al2O3 de-ionized water dispersion shows higher thermal conductivity than amorphous γ-Al2O3 due to its regular atomic arrangement and long order, which help in rapid transfer of phonon vibration from one atom to other.Figure optionsDownload as PowerPoint slide