This presentation will include a history of taking a process from an academic laboratory curiosity to the cusp of commercial processing – entirely during major global economic downturns. The role of intellectual property, government funding, university technology transfer, industrial support, and the perseverance and sacrifices of the scientists and engineers involved to succeed will all be discussed.
The functionalization of fine primary particles, including nanoparticles, is easily carried out using sequential self-limiting surface reactions in agitated systems. The self-limiting reactions result in the deposition of atomic or molecular layers, i.e. ALD or MLD. This functionalization process, referred to as Particle ALD/MLD, can be used to deposit conformal and pinhole-free films of refractory oxides, non-oxides, metals, and hybrid polymer-based materials, among others. It is also possible to deposit conformal porous or semi-continuous films where partial coverage is preferred instead. Fluidized bed reactors are well suited for large scale operations.
In this process, precursor chemical feedstocks can be utilized at nearly 100% efficiency without precursor breakthrough and loss. The ability to use precursors with efficiencies approaching 100% opens the door for a unique opportunity to utilize precursors that previously might have been considered to be too expensive. Fluidized beds containing particles comprising hundreds of thousands, even millions of m^2 of surface area can be coated efficiently. The dose times depend on the amount of surface area required to be coated and the flow rate of the precursor into the fluidized bed. Although dose times could potentially be very long for coating millions of m^2 of particles, i.e. minutes to hours, the efficient use of the precursor to place nearly perfect films on primary particles makes Particle ALD/MLD the low cost and potentially only process that can cost-effectively functionalize high surface area ultra-fine dry particles.
Particle ALD/MLD has been demonstrated to place nanofilms on primary nanoparticles as small as 10 nm as well as on nanotubes having surface areas approaching 1000 m2/g and within the porous structure of polymeric materials having porosity near 95%. Physical, optical, electrical, and magnetic properties of the particles can be controlled in order to passivate, activate, or is some manner functionalize the particles. Current applications of interest include passivation of phosphors and nanocrystals used in LEDs, improved cycling of Li-ion batteries, and high-activity sintering resistant catalysts among others.
Al Weimer is H. T. Sears Memorial Professor of Chemical and Biological Engineering at the University of Colorado, joining the faculty in 1996 after a 16-year career with the Dow Chemical Company. He is a Fellow of the American Institute of Chemical Engineers (AIChE) and has received a number of AIChE awards including the 2015 Nanoscale Science and Engineering Forum Award, the 2010 Excellence in Process Development Research Award, the 2009 Thomas Baron Award in Fluid-Particle Systems, and the 1997 Fluidized Processes Recognition Award. He has also received the 2005 U.S. Dept. of Energy Hydrogen Program R&D Award and was named an R&D 100 Award Winner in 2004 for his Particle ALD innovation. He received the Dow Chemical Company Excellence in Science Award in 1995, the Spangenberg Ceramics Founders Award in 1994 and was named Dow Central Research Inventor of the Year in 1993, all related to his invention and commercialization of processes to synthesize fine ceramic powders. He is named inventor on 32 issued U.S. Patents and has spun two startups out of his lab to commercialize the IP that was developed. He has directed the research of 29 Ph.D. students, publishing nearly 175 peer-reviewed journal articles, and mentored over 100 undergraduates with 28 of them ultimately receiving Ph.D. degrees, or, they are currently enrolled in Ph.D. programs. Al received his B.S. in Chemical Engineering from the University of Cincinnati in 1976 and his Ph.D. in Chemical Engineering from the University of Colorado in 1980.