Fluidization and coating of very dense powders by Fluidized Bed Chemical Vapour Deposition

Rodriguez, Philippe; Caussat, Brigitte; Ablitzer, Carine; Iltis, X.; Brothier, Méryl

doi:10.1016/j.cherd.2012.11.007

Cited by 16 publications

(10 citation statements)

References 15 publications

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“…A similar value of U mf was found in the two reactors, near to 2.7 cm s −1 . This value is very close to that previously found in the 5‐cm stainless‐steel FBCVD reactor using pure argon 21. According to Liu et al 22 and to Guo et al 23, when the reduction of the reactor diameter leads to modifications of the FB hydrodynamics, the U mf value increases and a pressure overshoot appears on the pressure drop curves, due to wall effects.…”

Section: Resultssupporting

confidence: 89%

Fluidized‐Bed Chemical Vapor Deposition of Silicon on Very Dense Tungsten Powder

et al. 2015

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A very dense tungsten powder was coated by silicon from silane using the fluidized-bed chemical vapor deposition process. A reactor of reduced diameter was developed in order to decrease the weight of powders treated. Results show that the fluidization of this powder is possible in this reactor, but with non-optimal gas solid contact induced by the high powder density. Important disturbances of the fluidized-bed temperatures appeared in the presence of silane, due to a partial bed defluidization related to the cohesive nature of the deposit. These disturbances are clearly exacerbated by the exceptional density of the particles. This is probably why a powder agglomeration has been unavoidable when the bed temperature was too low and/or the silane inlet concentration too high. However, a set of operating parameters could be found, allowing a uniform and continuous coating of the whole powder surface.

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Section: Resultssupporting

confidence: 89%

Fluidized‐Bed Chemical Vapor Deposition of Silicon on Very Dense Tungsten Powder

et al. 2015

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“…Metal -diketonates are advantageous, due to their relatively high vapour pressure at moderate temperatures and their thermal stability, 10 which explains the increased use of the nontoxic and inexpensive aluminium tris(acetylacetonate) Al(C5H7O2)3 as a precursor in MOCVD. [11][12][13][14][15][16][17][18][19] It is well-known that gas-phase reactions play an important role in the determination of the film composition, purity, and growth rate. 9 Due to the high activation energy of the unimolecular dissociation of metal -diketonates, the homogeneous decomposition of the gaseous precursor is considered as the rate-limiting step for film growth.…”

Section: Introductionmentioning

confidence: 99%

Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Grimm

Baik

Hemberger

et al. 2021

Phys. Chem. Chem. Phys.

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“…The ratio between the fixed bed height and the reactor diameter H 0 / D was fixed at three since this ratio allows for optimal heat transfers in the bed according to Rodriguez et al . This led to powder weights of 1500 and 740 g for reactor diameters of 3.8 and 3.0 cm, respectively.…”

Section: Methodsmentioning

confidence: 99%

“…The minimum fluidization velocity U mf was 3 cm/s, which was determined by studying the fluidization of the tungsten powder at room temperature . A fluidization ratio U g / U mf close to or higher than five ensures appropriate gas‐powder contact for CVD on these powders .…”

Section: Methodsmentioning

confidence: 99%

Silicon coating on very dense tungsten particles by fluidized bed CVD for nuclear application

Vanni

Caussat

Ablitzer

et al. 2015

Phys. Status Solidi A

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Tungsten particles were coated by silicon from silane (SiH4) at 645 °C using fluidized bed chemical vapor deposition (FB‐CVD). The coated particles were made from a surrogate tungsten powder and showed a median diameter (75 μm) and density (19,300 kg/m3). We studied the behavior of these tungsten particles due to their similarity with U(Mo) particles which are being investigated for use as fuel in research reactors. The results show that the fluidized bed's thermal gradient and pressure drop both increase as soon as silane is injected into the reactor. These phenomena are linked to the reactivity of silane and the very high density of the tungsten powder, and they represent a risk of bed agglomeration. A low inlet molar fraction of silane (0.5%) makes it possible to limit this risk. An increase in the fluidizing gas velocity and a decrease in the reactor diameter from 3.8 to 3.0 cm, have little impact on these phenomena for the operating range studied. Characterizations (EDX, SEM, XRD, etc.) show that all the tungsten particles are uniformly coated by a continuous film of silicon, mainly crystallized and of nodular morphology. The thickness of this silicon layers varies between 0.1 and 1 μm, which corresponds to the target. As the feasibility of the coating has been demonstrated, new experiments are in progress with fissile particles.

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Fluidization and coating of very dense powders by Fluidized Bed Chemical Vapour Deposition

Cited by 16 publications

References 15 publications

Fluidized‐Bed Chemical Vapor Deposition of Silicon on Very Dense Tungsten Powder

Fluidized‐Bed Chemical Vapor Deposition of Silicon on Very Dense Tungsten Powder

Gas-phase aluminium acetylacetonate decomposition: revision of the current mechanism by VUV synchrotron radiation

Silicon coating on very dense tungsten particles by fluidized bed CVD for nuclear application

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