Fluidization of Nanoparticle Agglomerates at Elevated Temperatures

The behavior of hydrophobic and hydrophilic nanoparticles was investigated. In a novel approach, the interparticle force (IPF) was altered by changing the temperature of the gas–solid fluidized bed in the range 25–110 °C. The hydrodynamic state of the bed was monitored by examining pressure fluctuations using coherent and incoherent analysis. Formation, coalescence, eruption, and mobility of bubbles in the fluidized bed were determined in addition to investigating the behavior of agglomerates. The diameter of the agglomerate was calculated from the incoherent output of the power spectral density of pressure fluctuations in the agglomerate particulate fluidization (APF) regime at various temperatures. No bubbles were detected in the bed of the silica nanopowder at low temperatures whereas small bubbles form at higher temperature. In contrast, hydrophilic titania nanopowder becomes fluidized in the ABF regime at lower temperatures and tends to fluidize at the APF regime with increasing bed temperature.