MATERIALS -- Steel for the 21st century . . .
Researchers at ORNL in collaboration with the Caterpillar Technical Center have developed a new modified cast austenitic stainless steel with significantly more high-temperature performance, durability and reliability than the common commercial grade of that stainless steel -- and at the same cost per pound as cast stainless steel. Called CF8C-Plus, development of the new cast steel was driven by the need for more performance and reliability in high-temperature exhaust components for advanced diesel engines for heavy-duty truck applications. However, it is also directly applicable to critical or structural components in a wide range of other applications, including marine diesel engines, industrial gas turbines, microturbines, automotive gasoline engines, natural gas reciprocating engines, and advanced, large land-based gas turbines or steam turbines. The new steel was developed by "engineered microstructures," a unique, rapid and practical ORNL alloy design method, derived from using more that 20 years of nanoscale microstructural/microcomposition data from the analysis of the roles of all the various alloying elements in the multitude of complex precipitate phases that form in stainless steels and alloys at high temperatures. This new steel resists failure during creep, mechanical fatigue and especially thermal fatigue, at up to 850C, a 200 degree improvement in performance and reliability over the common grade of such cast steel. [Contact: Marty Goolsby, 865-576-0226; goolsbymb@ornl.gov]
CHEMISTRY -- Nanostructures in a new light . . .
Getting single molecules of semiconducting polymers to orient themselves vertically on a glass surface is more than just a novelty, says Mike Barnes of the lab's Chemical Sciences Division. It turns out that the discovery could have applications in a number of areas, including for nanoscale electronics, polymer-based light emitting diodes and nano-scale sensors. Barnes and colleagues used ink-jet printing techniques to isolate the single molecules and achieve an extraordinary degree of orientational uniformity and intramolecular organization. "What's remarkable is that the orientation is in the non-intuitive z direction, like pencils all standing on their erasers instead of lying flat," Barnes said. As a result, they have photophysical properties that are quite different than similar molecules oriented randomly in thin films. For example, oriented single molecules emit light that lasts for several hours instead of just a few minutes, which is typical of randomly oriented single molecules of semiconducting polymers. This may have important implications in enhancing polymer-based optoelectronic device performance. The work has been published in Nanoletters and a paper is scheduled to appear in a June letter to the editor in Journal of Physical Chemistry B. [Contact: Ron Walli, 865-576-0226; wallira@ornl.gov]
INDUSTRY -- A sizzling partnership . . .
Reliability and efficiency are hot issues for manufacturers of microturbines, and companies like United Technologies, Ingersoll-Rand and General Electric look to ORNL for answers to some of their problems. Microturbines, which typically burn natural gas and can supply from 30 kilowatts to 500 kilowatts of electricity, operate most efficiently at temperatures approaching 1,200 degrees Celsius. Unfortunately, metallic components such as rotors have difficulty surviving in that environment, so the challenge is to develop ceramic rotors, which tolerate heat well, able to turn at speeds greater than 80,000 revolutions per minute and last 11,000 hours. Matt Ferber and Hua-Tay Lin of the lab's Metals and Ceramics Division take a unique approach to the problem as they examine actual microturbine ceramic components after they have been in use for hundreds of hours. It's the best way to see exactly what has happened – or what is happening – to the components. Microturbines can be used to provide electricity in remote locations or to supplement or replace electricity purchased from utilities. [Contact: Ron Walli, 865-576-0226; wallira@ornl.gov]
PHYSICS -- Record-setting sensors . . .
Nanoscale sensors 1,000 times more sensitive than those available today could be available in a couple of years as researchers at ORNL are approaching detection of single molecules under ambient conditions. Already, Panos Datskos and Nickolay Lavrik have set a world record by detecting 5.5 femtograms -– or about 5/1,000hs of a millionth of a millionth of a gram -– using tiny gold-coated silicon cantilvers (2 microns long and 50 nanometers thick) that they activate using a diode laser. The laser causes the cantilevers to vibrate – in this case at about 2 megahertz – and, depending on the coating, absorb particles of DNA, proteins, cells or trace amounts of various chemical contaminants. Datskos expects the sensors to be able to detect a single molecule by increasing the resonance frequency to 50 megahertz. The higher the frequency, the smaller the amount of mass that can be detected; however, the cantilevers must also be made smaller and stiffer. The research was published in the April 21 issue of Applied Physics Letters. [Contact: Ron Walli, 865-576-0226; wallira@ornl.gov]