<i>In situ</i> x-ray imaging of nanoparticle agglomeration in fluidized beds

Abstract

A high spatial (down to 400 nm) and temporal resolution (down to 1 ms) x-ray imaging apparatus has been designed to study the agglomeration of arc plasma synthesized zinc oxide nanoparticles (average diameter of 50 nm) in fluidized beds under different gas flow velocities. The mean volume distribution of the nanoparticle agglomerates was determined with x-ray microtomography and found to correspond to a lognormal distribution with a mean value of 0.70×109μm3 and a variance of 3.6×1021 (μm3)2. The average density of the agglomerates was found to be 2.9gcm−3 compared to 5.6gcm−3 for the individual nanoparticles. The powder assembly was then dynamically imaged using an x-ray image intensifier coupled to a digital camera using a field of view of 24.20 mm by 32.25 mm and a temporal resolution of 40 ms. Sequential frames were captured into computer memory for a range of gas flow velocities from 0.026ms−1 to 0.313ms−1. The breakup energy of the agglomerates was calculated to be approximately 2×10−8J using a combination of dynamic observations and physical properties of the agglomerate system extracted from the x-ray microtomographic data.