An experimental study was conducted to assess the solid hold-up distribution in a fluidized bed of zirconia and aluminum nanoparticles. For this purpose, two different techniques, radioactive densitometry and fibre optic measurement, were used. The results showed that while the fluidization of these nanoparticles occurs in the agglomeration state, it performs homogeneously in terms of phase concentration. This matter is important especially when a polymerization reaction should take place uniformly on the surface of nanoparticles, where the monomer is the fluidizing gas. Both techniques presented uniform solid hold-up distribution over the cross-section, although the fibre optic method overestimated the overall solid concentration, which was obtained based on bed expansion results. The radioactive densitometry was, however, capable of properly predicting the phase concentration within the bed according to the bed expansion observation. Finally, the effect of bulk density on the fluidization of nanoparticles was discussed by comparing the fluidization of different types of particulate materials.On a mené uneétude expérimentale pourévaluer la distribution de rétention de solide dans un lit fluidisé de nano particules de zircon et d'aluminium.À cette fin, deux techniques différentes, la densimétrie radioactive et la mesure par fibres optiques, ontété utilisées. Les résultats montrent qu'alors que la fluidisation de ces nano particules survientà l'état d'agglomération, elle est relativement performante en termes de concentration de phase. Cet aspect est important, car une réaction de polymérisation devrait se produire uniformémentà la surface des nano particules, le monomèreétant le gaz fluidifiant. Les deux techniques ont mis enévidence une distribution de rétention de solide uniforme dans la section transversale, bien que la méthode par fibres optiques ait surestimé la concentration de solide globale, obtenueà partir des résultats d'expansion du lit. Cependant, la densimétrie radioactive est capable de prédire de manière correcte la concentration de phase dans le lit d'après l'observation de l'expansion de lit. Enfin, l'effet de la masse volumique apparente sur la fluidisation des nano particules est examiné en comparant la fluidisation de différents types de matériaux particulaires.

Zirconia nanoparticles were encapsulated by polyethylene via a polymerization compounding method using a Ziegler‐Natta catalyst. The chemical reaction was carried out in an organic solvent under moderate pressure of ethylene monomer. Transmission electron microscopy (TEM) indicated the presence of a thin layer of polymer, about 6 nm, uniformly applied around the particles. However, the thickness of coating layer can be controlled as a function of time and operating conditions of the process. The morphology study using scanning electron microscopy (SEM) as well as TEM revealed that although the nanoparticles seem to be coated individually, some agglomerates, encapsulated by a polymer film, could be observed. The grafting of the catalyst to the original surface of particles was further confirmed by X‐ray photoelectron spectroscopy (XPS).

For the first time, a fluidized bed reactor was used for encapsulating nanoparticles by the polymerization compounding approach using Ziegler-Natta catalysts. The polymerization reaction was carried out using a solvent-free process in a gas-phase reactor. This direct gas-solid reaction greatly simplified collecting the particles of interest after polymerization because none of the extra steps often found in encapsulation processes, such as filtering and drying, were performed in this work. The grafting of the catalyst to the original surface of particles was confirmed by X-ray photoelectron spectroscopy. Micrographs obtained by transmission electron microscopy confirmed the presence of a thin layer of polymer, in the order of a few nanometers, around the particles. The thickness of this coating was affected by the operating conditions of the process. The characterization of the modified particles with electron microscopy also revealed that zirconia nanoparticles tend to be coated in an agglomerated state, whereas aluminum particles were mostly individually encapsulated by the polymer. In addition, the effects of temperature and pressure were studied on the encapsulation process and a kinetic analysis was presented based on the available models in the literature. V

For the first time, an in situ polymerization technique was applied to produce mullite-bonded porous SiC ceramics via a reaction bonding technique. In this study, SiC microsized particles and alumina nanopowders were successfully coated by polyethylene (PE), which was synthesized from the particle surface in a slurry phase reactor with a Ziegler-Natta catalyst system. The thermal studies of the resulting samples were performed with differential scanning calorimetry and thermogravimetric analysis. The morphology analysis obtained by transmission electron microscopy and scanning electron microscopy (SEM) confirmed that PE was successfully grafted onto the particle surface. Furthermore, the obtained porous ceramics were characterized in terms of their morphologies, phase composition, open porosity, pore size distribution, and mechanical strength. SEM observations and mercury porosimtery analysis revealed that the quality of the dispersion of nanosized alumina powder into the microsized SiC particles was strongly enhanced when the particles were coated by polymers with in situ polymerization. This resulted in a higher strength and porosity of the formed ceramic porous materials with respect to the traditional process. In addition, the X-ray diffraction results reveal that the amount of mullite as the binder increased significantly for the samples fabricated by this novel method. The effects of the sintering temperature, forming pressure, and polymer content on the physical and mechanical properties of the final porous ceramic were also evaluated in this study.

The encapsulation of aluminum nanoparticles by polyvinylidene fluoride (PVDF) was carried out in supercritical conditions via in situ polymerization. The aluminum particles possessed an average diameter of 43.7 nm. The presence of PVDF on the particles was validated by thermogravimetric analysis (TGA). This result was further approved by X-ray photoelectron spectroscopy (XPS), which showed high intensity peaks of fluorine and carbon on the particles after the encapsulation process, which are associated with the presence of hydrocarbon-based PVDF. As observed by transmission electron microscopy (TEM) images, the nanoparticles were uniformly coated by a polymer of a few nanometers in thickness. The results showed that there is a good consistency between the calculated thickness of the polymer coating and the results obtained by TEM. In addition, the effect of polymerization time on the kinetics of the reaction was investigated. Finally, it was found that the thickness of the polymer layer can be controlled by the duration of the encapsulation process. POLYM. ENG. SCI., 52:637-642, 2012.