INL's Modular Hybrid Plasma Reactor
Lowering the Cost of Nanoparticle Production
October / November 07
Volume 5 Number 5
Nanotechnology has improved the quality of numerous products, from windows and auto paint finish to cosmetics and body armor. Unfortunately, the ability to achieve the potential of nanoparticles in improving material properties has been limited commercially by the high cost of production. A revolutionary technology, called the Modular Hybrid Plasma Reactor, has been developed at Idaho National Laboratory that provides a more cost- and energy-efficient system to create nanoparticles.
A common method of creating nanoparticles is to break down materials into their smaller components using reactors. Plasma reactors have been used for this process for decades. The formation of nanoparticles relies on three phases: keeping the feed material at a high temperature, maintaining the gas phase once the material is converted and forming nanoparticles from the gas phase as it exits the reactor.
Peter Kong, the technical leader for plasma processing at INL, described the process of development of the Modular Hybrid Plasma Reactor. He first identified the problems with the existing reactor technology: not a high enough temperature available for a larger reaction region; residence time for material inside the plasma (or high temperature area) was too short; temperature was quenched or decreased too quickly.
"Knowing those barriers," Kong says, "I started looking at what were the potential fixes that could overcome those barriers. That led to the formulation of the new reactor concept that is more advanced, robust, versatile and addresses the fundamental barriers."
Kong's reactor features a larger reaction region and higher uniform temperatures (>7000°K). This allows for the process to be sustained longer, thereby increasing the residence time. It is able to accept solid, liquid and gaseous reactants due to a versatile feed process, and accommodate large, particle-sized feed materials. The bench scale reactor is being scaled up to a 300 kW pilot production system, and is able to process more materials and produce better products at the same energy level consumption as other reactors.
Instead of creating a precursor chemical to use as the feed material in the creation of nanoparticles, the reactor at INL starts with the end product. "If you start with aluminum," Kong says, "you end up with aluminum, so you eliminate a lot of the unit process operations in between, plus any equipment associated with the steps of that process. Overall efficiency and cost reduction would be quite a bit better when compared to the current commercial process." Using benign starting materials also reduces the problem of toxic wastes as byproducts of the reaction, thus providing environmental benefits.
In 2001, a Cooperative Research and Development Agreement (CRADA), was established between INL and PPG Industries, Inc. PPG has also taken a license option with the lab so that when the technology is mature enough, it will adopt the system for nanoparticle production. The company uses nanoparticles to create products such as CeramiClear and SunClean. CeramiClear, a clearcoat to protect the surface of cars, contains a highly cross-linked network of nanomaterials. CeramiClear is so effective that more arduous testing had to be devised. It received the PACE (Premier Automotive Suppliers' Contributions to Excellence) award in 2003. SunClean windows have a titanium dioxide nano-coating that has photocatalytic and hydrophilic properties, enabling the glass to be self-cleaning. The sun's UV rays facilitate the breakdown of organic dirt, which is then washed away through the sheeting action of water droplets.
Nanotechnology has applications in many other fields. In cosmetics, microcapsules transport Vitamin A deeper into the skin, thereby improving the health, not just the look, of skin. Body armor is being designed for soldiers that is lighter and more flexible than Kevlar, but becomes rigid upon stimulus to provide greater ballistic protection. In information technology, the controlled deposition of layered structures just a few atoms thick engenders smaller, faster, more power-efficient silicon transistors. In the medical field, there are hopes of being able to treat cancer at the individual cell level by using nanoparticles as a delivery system for pharmaceuticals.
Stacey Cashmore is a technical writing intern at Idaho National Laboratory.
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