Alumina films were deposited on titania nanoparticles via atomic layer deposition (ALD) in a fluidized bed reactor at 180 °C and 1 bar. Online mass spectrometry was used for real time monitoring of effluent gases from the reactor during each reaction cycle in order to determine the optimal dosing time of precursors. Different oxygen sources were used to see which oxygen source, in combination with trimethyl aluminium (TMA), provides the highest alumina growth per cycle (GPC). Experiments were carried out in 4, 7 and 10 cycles using the optimal dosing time of precursors. Several characterization methods, such as high resolution transmission electron microscopy (HRTEM), Brunauer-Emmett-Teller (BET), energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and instrumental neutron activation analysis (INAA), were conducted on the products. Formation of the alumina film was confirmed by EDX mapping and EDX line profiling, FTIR and TEM. When using either water or deuterium oxide as the oxygen source, the thickness of the alumina film was greater than that of ozone. The average GPC measured by TEM for the ALD of TMA with water, deuterium oxide and ozone was about 0.16 nm, 0.15 nm and 0.11 nm, respectively. The average GPC calculated using the mass fraction of aluminum from INAA was close to those measured from TEM images. Excess amounts of precursors lead to a higher average growth of alumina film per cycle due to insufficient purging time. XRD analysis demonstrated that amorphous alumina was coated on titania nanoparticles. This amorphous layer was easily distinguished from the crystalline core in the TEM images. Decrease in the photocatalytic activity of titania nanoparticles after alumina coating was confirmed by measuring degradation of Rhodamine B by ultraviolet irradiation.@en

A method is developed for hydrodynamics scale-up of gas-solid fluidized beds based on recurrence quantification analysis of nonlinear time series of pressure fluctuations. This method is an improvement of the previous method by including the entropy of pressure fluctuations to the list of scale-up parameters. Experiments were carried out at varying conditions, e. g., bed diameter (5, 9, 15, 40 and 80. cm ID), particle size (150, 300, 400 and 600. μm), bed height at aspect ratios (1, 1.5 and 2) and superficial gas velocities (ranging 0.1 to 1.7. m/s) to identify the main parameters that influence the dynamics and to develop a general interpretation of the analysis results. By investigation of the effect of operating parameters on entropy, a quantitative empirical correlation is proposed for including the entropy in the scale-up parameters. It was shown that this correlation improves the Glicksman's method for the scale-up of fluidized beds.@en