Design and Construction of a Vibrating Fluidized Bed Reactor for Particle Atomic and Molecular Layer Deposition

Atomic and Molecular Layer Deposition (ALD/MLD) is a series of self-limiting gas phase reactions that are used to deposit films uniformly. ALD is used to deposit inorganic films, whereas MLD is used to deposit organic films. These processes use the concept of self-limiting surface reactions in alternating dosing and purging phases to achieve a dense, uniform coating [1]. The amount of time with each reactant dose and purge can be altered, as well as how many cycles are used, to optimize the maximum amount of uniform coverage on selected support materials. Both ALD and MLD have a wide range of applications including catalysts and barrier coatings. Particle ALD was introduced in the early 2000s at the University of Colorado Boulder [1] and involves a specialized vibrating fluidized bed to achieve conformal coatings on primary particles, which will be constructed herein.

The build of this reactor involved the knowledge of the desired chemistry, fluidization, mechanical mixing, material choices and their restrictions, heat transfer, instrumentation and control, accessibility, economics, and safety. Proper fluidization and mixing ensure that the concentration of the reactants are dispersed equally, prevents agglomeration, and reduces mass transfer limitations. This reactor was designed to operate and perform ALD and MLD to create CO2 capture materials which will require multiple precursors and a range of temperature conditions. An extensive Standard Operating Procedure (SOP) outlines the entire system and its individual components. Safety being the utmost important aspect in any reactor, the SOP is meant to detail the overall process and guide and identify any internal failures that might be occurring.

After the construction of this reactor, numerous tests were performed including temperature monitoring, fluidization testing, and performance of hardware and software checks. The baseline of ALD in this reactor was demonstrated through alumina ALD with trimethyl aluminum and water. Developing these skill sets has provided a deeper, thorough understanding and hands on experience of chemical engineering fundamentals. The design and construction of this reactor was performed by a graduate student and an undergraduate student with support from a research associate and the machine shop.

References

[1] Alan W. Weimer. J. Nanopart Res 21:9 (2019)