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Nanophase Technologies Corp., headquartered in Romeoville, Ill., is one such supplier that is helping to drive the development of these new markets. The company was established in the late 1980s by several Argonne National Laboratory researchers who spent the next several years refining and developing a unique process to fabricate nanomaterials, called physical vapor synthesis (PVS). Today, as a publicly held corporation, Nanophase Technologies operates a production facility in Burr Ridge, Ill., with the capacity to produce over 1 million pounds of nanomaterials per year. When coupled with the company’s proprietary surface treatment chemistry, these PVS-produced nanocrystalline particles can be dispersed in a wide range of formats and tailored to meet a variety of applications, including ceramic manufacturing.
Manufacturing TechnologyThe near-atomic size of nanomaterials, combined with the dynamic properties of their surface atoms, mean they can be used to alter and enhance the performance of raw materials, such as zinc, aluminum and iron, yielding materials with chemical, mechanical, electrical and optical behavior that goes beyond the capability of the original material. Nanomaterials provide improved catalysis, dispersion, transparency, and surface smoothness and gloss, as well as finer abrasiveness and ceramic toughness in applications ranging from high-tech coatings and chemical/mechanical polishing (CMP) slurries to fuel cells and multi-layer ceramic capacitors (MLCCs). Because of their potential for improving science and engineering as a whole, nanomaterials and other nanotechnologies have been called “the next industrial revolution” by such key organizations as the National Science and Technology Council. However, this revolution can occur on a broad scale only through the right manufacturing process—one that can provide the necessary material solution, in the form required, and in commercial volumes. Nanophase Technologies has spent the past 10 years developing and refining such a process.
First, the company uses PVS to create its nanomaterials. In PVS, plasma is used to heat a precursor metal. The metal atoms boil off, creating a vapor. A gas is introduced to cool the vapor, which condenses into liquid molecular clusters. As the cooling process continues, the molecular clusters are frozen into solid nanoparticles. The metal atoms in the molecular clusters mix with oxygen atoms, forming metal oxides—such as aluminum oxide—smaller than 100 nanometers.
After nanoparticles are created through PVS, some applications require their surfaces be engineered to meet additional customer requirements. Nanophase Technologies achieves this through a process called discrete particle encapsulation (DPE). In DPE, selected chemicals are used to form a thin polymeric shell around each nanoparticle—providing the characteristic a customer needs. This coating is chemically modified so the nanoparticle will disperse in the best format for customers. The shell contains spacer molecules that prevent the nanoparticles from coming into contact with each other. The result is steric stabilization for nanoparticles used in non-liquid solvents and polymers, and electrosteric stabilization for those needing to disperse in a fluid.
Achieving ImprovementsWithin the past year, Nanophase Technologies has made great strides in further improving its core PVS nanocrystalline manufacturing process. The company announced in June 2001 that a series of process improvement initiatives enabled the company to achieve an additional 30% output per reactor, significantly improve the particle size control, and enhance the quality and purity of its nanomaterials.
“This was a significant milestone for the company and continued our two-year sequence of successes in lowering manufacturing costs by consistently improving a wide range of operating parameters and reducing supply chain costs,” said Joseph Cross, Nanophase’s president and CEO. During the previous 15 months, the company had reduced its variable manufacturing cost by approximately 50% and increased output per reactor from 30 to 100%, depending on the material being produced, as part of an overall lean manufacturing approach. The company expects to achieve further manufacturing cost reductions and product improvements over the next several years through these measures.
As evidence of these improvements, the company announced in July the availability of three new custom-engineered, high-purity nanocrystalline metal oxides:
- NanoTek® Zinc Oxide HP,designed to provide high reliability electronics applications, including capacitors, varistors, photoprinting and electrophotography
- NanoTek Aluminum Oxide HP, designed for use in polishing applications, including semiconductors and rigid memory disks; the lighting industry for fabrication of transparent glass envelopes for high intensity lighting applications; and high performance thermal spray applications
- NanoTek Cerium Dioxide HP, targeted for polishing applications, including semiconductors and rigid memory disks, as well as catalysis applications requiring high surface areas combined with high levels of chemical purity
In August, Nanophase Technologies announced that nanosized materials such as antimony tin oxide and indium tin oxide could be used in high-tech coatings to absorb infrared radiation and enable thermal control in environments exposed to direct sunlight (such as car windows and architectural glass). The improved technology provides coatings with lower haze and improved transparency, as well as conductive and static dissipating properties. Potential applications include video displays, touch screen applications and packaging for static sensitive electrical components, such as computer memory. The company plans to co-engineer coatings with customers to match specific application requirements.
Advancing Technology Through PartnershipsWhile much has been done to advance the commercialization of nanomaterials, the developments have, in many ways, merely scratched the surface of the vast potential for these unique products. Nanophase Technologies plans to continue its efforts to lead the industry in further technology developments and applications.
For ceramics in particular, the company is pursuing a number of promising technologies, including thermal spray coatings, fuel cells and electronic ceramics. “There is documented evidence that nanostructured ceramic coatings, such as those based on aluminum oxide and mixtures of alumina and titania, have some significant benefits, including high hardness and wear resistance,” said Dr. Don Freed, vice president of business development.
“Applications such as fuel cells and passive electronic components are two other areas,” he added. “For instance, most varistors are based on zinc oxide, and there is very significant evidence showing that as you decrease the particle size of the zinc oxide, the electrical properties of the varistor improve significantly—you get a much wider range of operation in terms of voltage and current.
“And then there’s a whole area of electronics called hybrid circuits, or microelectronics. The substrates for that, which are made from aluminum oxide, are a very substantial amount of the platform. So again, as you make the particles smaller, and the structure of the material becomes finer, you improve the properties of the material,” Dr. Freed said.
But while the company continues to invest in developing these unique materials, it does more than simply supply a “powder.” Rather, it is focused on integrating technologies to provide optimally engineered solutions to its customers.
“No one really wants to own a bag of nanopowder, no matter how much we extol the virtues of this wonderful nanocrystalline material,” said Dr. Freed. “We intend to grow by manufacturing nanomaterials, but we can’t do it alone. We really want to focus on finding and developing mutually beneficial relationships with companies.”