GOALI: Continuous Spatial Particle Atomic Layer Deposition Processing

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Atomic layer deposition (ALD) is the most precise method for manufacturing conformal, continuous thin film coatings. ALD processing is important in many manufacturing processes for optics, microelectronics, and biomedical applications, though it can be slow and costly. ALD uses sequential gas-solid reactions where gas-phase reactions are prevented by having precursors fed separately into the reaction chamber and react with functional groups bonded to the surface. The proposed GOALI project is a collaboration between an academic team from the University of Colorado at Boulder and an industrial partner, ALD NanoSolutions. The objective of the proposed research is to develop an improved fundamental understanding of spatial atomic layer deposition on particles (i.e. spatial Particle ALD), so that high-efficiency and low-cost continuous Particle ALD can be achieved.The proposed project will involve Computational Fluid Dynamics (CFD) model development and integrated experiments aimed at developing a scalable ALD process in which primary particles are coated uniformly and expensive precursor gases are effectively utilized. A continuum-scale model will account for agglomerate formation and breakup as well as chemical reactions, fluid dynamics, heat/mass transport, and all relevant multiphase interactions during fine particle agitation using vibration. The hypotheses to be tested include: (1) that a continuum-scale model will adequately describe the proposed agitated particle system; (2) that it is possible to coat individual nanoparticles in a continuous vibrating Particle ALD reactor without loss of active surface area; (3) that Particle ALD processing in a continuous vibrating Particle ALD reactor can be optimized to utilize the precursor gases nearly completely; (4) that the modified in-house lab system will provide data needed for experimental validation of the CFD model; and (5) that substrate particles coated by continuous spatial particle ALD will compare favorably with particles synthesized using a batch fluidized bed process - for the identical number of ALD cycles. Experiments carried out at ALD NanoSolutions will focus on validating the model predictions and findings of the academic team and scaling up the process. The ultimate objective of the project is to substantially improve the fundaental understanding of how Particle ALD enables primary fine particles, including nanoparticles, to be coated in an agitated particle bed reactor and enable process scale up for commercial production. A graduate student will be trained in close collaboration with the industrial partner and undergraduate students will be engaged in research. The project will also be used as a capstone design project for undergraduate student teams to perform process design and techno-economic analysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.