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Friday, 4 May 2012

Showing Their Metal: Researched materials and inventing a new one that makes a splash in the marketplace

May 4, 2012

AFA: Alumina-Forming Austenitic Stainless Steels, developed by materials researchers at Oak Ridge National Laboratory, feature an increased upper-temperature oxidation limit that is up to 200 C higher than that of conventional stainless steels. The innovation won an R&D 100 Award in 2009 and was licensed to Carpenter Technology Corporation. Image: Oak Ridge National Laboratory

Inventing new metal products is tough. R&D finds out how recent R&D 100 Award-winning technologies have fared in the marketplace.

Metals are among the most heavily researched materials, and inventing a new one that makes a splash in the marketplace is often excruciatingly difficult.

The R&D Magazine editors investigated the commercial progress of two recent R&D 100 Award winners that have made significant gains in their markets. Relative to the many years of work leading up to the awards, the successful license agreements and real-world applications have been a pleasant surprise for the developers.

Evolving alloy gains market traction
Steel alloys that operate in high-temperature situations, such as aircraft engines and metal-forming machinery, are often austenitic, meaning they have as their primary base a face-centered cubic crystal. These crystals have multiple contacts—or lattice points—per flat surface, giving them extra strength even when operating temperatures skyrocket.

They are typically iron combined with about 18% chromium and 8% nickel. Despite their strength and high-temperature durability, they are often passed over for nickel-based alloys when temperatures reach 600 C or more. The key issues, say researchers at Oak Ridge National Laboratory (ORNL), Oak Ridge, Tenn., are creep and corrosion. Because austenitic steels cannot be hardened through heat treatment, they are vulnerable to upper-temperature oxidation. And, at these temperatures, austenitic steels are more vulnerable to permanent deformation under stress. Despite experiments with the addition of carbides and nitrides, most efforts improved corrosion at the expense of creep.

ORNL wanted a better solution that would allow them to keep the excellent weldability and formability of stainless steel without having to migrate to difficult-to-work, expensive nickel metals. The reason? For more than a decade, ORNL had been working with industrial partners to design recuperators (counter-flow heat exchangers for waste heat recovery) for turbines that can endure high-temperature, wet operating conditions. Traditionally, recuperators have been made from 347 stainless steel, but performance and durability degrades markedly at 650 C, and the problem gets worse in moist air.

In 2008, ORNL finished development of a new austenitic-forming process it hoped would suit applications like turbine recuperaters. The method induces a protective aluminum oxide surface layer without having to add oxides conventionally. Counter-intuitively, the process improvement was made when the titanium and vanadium alloying additions—frequently used for strength—were deleted from the preparation. This allowed protective aluminum oxide scale formation to begin despite much lower levels of aluminum in the austenitic alloy. Low aluminum levels stabilize the matrix structure of the metal and permit better creep resistance through a nanoscale niobium carbide precipitate formation.

The result of this process change is an upper-temperature oxidation (corrosion) limit that is greater than or equal to conventional stainless steels at 50 to 200 C higher. Creep is reportedly excellent at temperatures of 700 to 800 C, which is optimal for use in high-grade machinery such as turbines. In addition, the material can be used under the aggressive oxidizing conditions encountered in energy conversion and chemical process systems.

The breakthrough earned the ORNL team a 2009 R&D 100 Award for AFA: Alumina-Forming Austenitic Steels. In March 2011, Carpenter Technology Products, a Wyomissing, Pa., company that produces stainless and specialty alloys, licensed the technology. Their goal for commercial products is to build on the research done by Bruce A. Pint—group leader of the Corrosion Science & Technology Group in the Materials Science & Technology Division at ORNL—and his team after they won their R&D 100 Award. In 2010, they successfully made AFA steel foils for advanced turbine recuperator applications. Three commercially cast foils measuring approximately 100 µm performed well in testing, forming chemically stable external alumina scale at temperatures up to 900 C. Acceptable oxidation was also shown for sheet specimens exposed in a 65 kW microturbine for 2,871 hours. One of the test compositions was selected for a commercial foil batch.

"The commercial material was first delivered to a turbine manufacturer in 2011. We expect engine tests in 2012," says Pint. In addition to winning the R&D 100 Award, Pint and other AFA team members, Craig Blue, Michael Brady, Alex DeTrana, Alan Liby, Joe Marasco, Phil Maziasz, Michael Santella, and Yukinori Yamamoto also received an outstanding team accomplishment award at ORNL's annual awards.

Printed electronics realized with award-winning tools
Ever since the Gutenberg Bible was printed, the method of applying substances, mostly inks, to various substrates has been one of the touchstones of low-cost volume fabrication. For hundreds of years, the model has been confined to ink on paper, but as the mastery of materials increases, so do the options for volume printing.

As improved printing technology allowed the use of "inks" containing or consisting entirely of polymers or even metals, the push has been to make such methods commercially useful. Aside from specialized deposition roll-to-roll processes such as flexible photovoltaics, one of the most compelling avenues is printed electronics. Either sheet-based (low-volume) or roll-to-roll (high-volume), printed electronics depend on the accurate and consistent dispersion of liquids containing the appropriate metallized particles.

Since 1999, NovaCentrix, Austin, Texas, has been striving to develop both the machinery and inks to make these technologies possible. In 2009, the company won its first R&D 100 Award for a printed electronics process tool, the PulseForge 3100 with Pulse Thermal Processing. It then followed up with another R&D 100 Award-winning product in 2010, Metalon ICI Low Cost Conductive Ink. Together these products were NovaCentrix's bid to gain a competitive advantage in the printed electronics market.

"Although distinctly different technologies, they are complementary by design," says Stan Farnsworth, vice president of marketing at NovaCentrix. These technologies represent an early entry in a changing printing industry, he says. "Printed electronics conferences are now beginning to include a new category based on this technology."

Unlike traditional ovens used to deposit high-technology inks, PulseForge tools dry and sinter metallic-based as well as non-metallic inks including ceramics and semiconductors in milliseconds without heating the substrate. The proprietary technology involves high-speed sintering with visible-light flash lamps, restricting the rise in temperature. Reduced thermal load helps reduce cycle times significantly, speeding production. Lower temperatures also allow the use of plastic substrates, enabling production with the efficient roll-to-roll process.

Metalon ICI, meanwhile, is a low-cost nanostructured copper oxide-based ink for printing conductive thin films. During the printing process it converts from oxide to basic copper, allowing highly electrically conductive wires to form. At $75/kg in 2010, the ink was about 100 times less expensive than comparable silver-based inks at the time of its introduction.

"Our sales have grown tremendously year on year, and our staff has doubled," says Farnsworth. "We are optimistic about 2012, as thus far in the year the growth trend is continuing. We are also in the process of expanding our facility size, by about double, to accommodate additional manufacturing operations and staff."

Part of this growth is due to two major licensing agreements signed in 2011. The first, with Showa Denko in Japan, is intended to produce more advanced inks.

In August 2011, DuPont Microcircuit Materials (MCM), a division of DuPont Electronics & Communications in Research Triangle Park, N.C., purchased a license to begin using NovaCentrix's PulseForge tools. According to Scott Gordon, market segment manager with DuPont MCM, the move was based on industry analyst predictions that emerging markets in printed electronics will stress low-temperature processing and dramatically higher speeds of production. The photonic curing technology used by the PulseForge was designed specifically with these production characteristics in mind, and DuPont was attracted to the PulseForge’s ability to advance their efforts in printing radio-frequency identification tags, and the thin-film semiconductor layers and fine-line microcircuitry crucial to flexible displays.

PulseForge has since been updated to a slightly more advanced 3200 system, and an ultra-high power version for semiconductor processing called the PulseForge 3300 was developed.

"Additionally, we have continued to strengthen our IP position by filing additional patents world wide. 'Me-too' competitors are a sign of success, and we are dutifully wary of potential emerging copycats," says Farnsworth.

The company now has sales offices in Japan and Germany, and filled out its goals for an expected customer base. Its ink customers are global, and multiple tool customers are based in the United States, Europe, and Japan.

Though PulseForge and the Metalon inks have been used primarily for new technology development, NovaCentrix has seen other uses for its processing tools.

"Although anticipated, we have been pleasantly surprised how many companies are using the PulseForge tools and related technology to dry thin films. It turns out that energy-efficient rapid drying of thin films is in big demand," says Farnsworth.

Source: R&D Magazine


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