Fluidization and sedimentation behaviors of nanoparticles.

Abstract

A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 to 100 nanometers in diameter. Nanoparticles were used by artisans since prehistoric times, albeit without knowledge of their nature. Analyzing the outcome from the experiments of the study, the following questions were considered: 1. What will be the behavior of fluidization of 13 nm aluminum oxide and 10-20 nm silicon dioxide nanoparticles that fall under Geldart group C? 2. What is the existing relationship between physical characteristics of 13 nm aluminum oxide and 10-20 nm silicon dioxide nanoparticles with the fluidization enhanced by vibration and acoustic sound? and 3. What is the effectiveness of fluidization enhanced by vibration and acoustic sound on nanoparticles materials under study used in the experiment depending on their physical properties? It was crucial to consider the above-mentioned questions to undertake the study on the fluidization and sedimentation to investigate the behavior of nanoparticles. From the findings, the experimental measurement of the pressures in different regions of the fluidized bed, in the plenum chamber, on the bed of the solid material, and above the bed of solid material was performed by using pressure transducers and the inverted U-tube manometers to investigate the behavior in the fluidization of samples of size 277 µm, 428 µm, 161 µm, and 338 µm. The applicability of the published correlations such as the Ergun equation was fitted to the experimental pressure drop measured using both measuring methods; the sphericities of the samples were measured using the fitted Ergun equation. The fluidization parameters such as minimum fluidization velocity, voidage, and height were measured from the experimental data and compared with the calculated minimum fluidization parameters obtained from the published correlations. Two methods were used during the experiment; acoustic sound fluidization and vibro-fluidization. During the enhanced fluidization by external forces of aluminum oxide and silicon dioxide nanoparticles, the primary size of nanoparticles formed agglomerate, and their fluidization was of agglomerate particulate fluidization. The use of the Richardson and Zaki equation and Stokes’ Law in the experimental data was to estimate the size of the agglomerate formed during fluidization associated with mechanical vibration and acoustic sound. It was found that the size of agglomerate formed during fluidization associated with mechanical vibration was 48 µm when aluminum oxide nanoparticles were under vibro-fluidization. The sedimentation behavior of nanoparticles was investigated from the batch settling test. It was noticeable by visual observation, aluminum oxide nanoparticles settled after 2 hours in a batch settling test while the silicon dioxide nanoparticles demonstrated different behavior in settling. It was observed that after 72 hours of batch settling test of silicon dioxide nanoparticles, a clear region was observable in the cylindrical tube. The use of Stokes’ Law demonstrated that the size of the settled silicon dioxide nanoparticles could be estimated from sedimentation theory.