Story Tips from the Department of Energy’s Oak Ridge National Laboratory, July 2016
MATERIALS – 3-D-printed heat sinks …
Increased power densities in electronics will require more efficient heat sinks, and additive manufacturing combined with a simple thermal annealing process could help designers meet that goal. A team that includes Oak Ridge National Laboratory's Tong Wu reported that while a 3-D printed aluminum alloy heat sink equaled or measured 10 percent worse than those manufactured conventionally, after the treatment the performance gap vanished. In fact, the optimized heat sink demonstrated a 22.8 percent reduction in junction temperature and 33 percent reduction in weight, said Wu, a member of ORNL's Power Electronics and Electric Machinery Research Center. Additive manufacturing makes it possible to produce one-piece exchangers with complex internal structures able to efficiently dissipate heat. [Contact: Ron Walli, (865) 576-0226; [email protected]]
Cutline: Temperature is represented by different colors for this heat sink for a 50-kilowatt DC-to-DC converter with red being the hottest.
MANUFACTURING – Inspections on the fly …
Production run spot checks of materials for lithium-ion batteries and fuel cells could be a thing of the past because of a process developed at Oak Ridge National Laboratory. The infrared/thermal nondestructive evaluation technique invented by a team led by David Wood examines key parameters such as porosity and thickness of the coating in real time without destroying product. In contrast, conventional inspection methods for roll-to-roll products require the production line to be stopped and the examined material to be destroyed. "Our approach ensures a higher, more consistent performance from the product, saves time, lowers costs and eliminates the use of destructive examination," Wood said. This technique, developed in collaboration with researchers at National Renewable Energy Laboratory, could also be used for other roll-to-roll produced products such as fuel cells. [Contact: Ron Walli, (865) 576-0226; [email protected]]
Cutline: ORNL technology enables quality checks of material during roll-to-roll processing, lowering costs and eliminating waste.
SUPERCONDUCTIVITY – Bridging the pseudogap …
Since the discovery of high-temperature superconductors — materials that can transport electricity with perfect efficiency at or near liquid nitrogen temperatures (minus-196 degrees Celsius) — scientists have been working to develop a theory that explains their essential physics. At the heart of this mystery is the pseudogap, a pivotal juncture on the path of superconducting copper oxides in which both insulating and conducting properties are present. Under these conditions, the conventional pathway to superconductivity is blocked, but a team led by Thomas Maier of Oak Ridge National Laboratory used the Titan supercomputer at ORNL to identify a possible alternative. Simulating a 16-atom cluster, the team measured a strengthening fluctuation of electronic antiferromagnetism, a specific magnetic ordering in which the spins of neighboring electrons point in opposite directions (up and down), as the system cooled. The findings add context to scientists' understanding of the pseudogap and how superconductivity emerges from the phase. [Contact: Jonathan Hines, 865-574-6944; [email protected]]
Cutline: In conventional low-temperature superconductivity (left), so-called Cooper pairing arises from the presence of an electron Fermi sea. In the pseudogap regime of the cuprate superconductors (right), parts of the Fermi sea are "dried out" and the charge-carrier pairing arises through an increase in the strength of the spin-fluctuation pairing interaction as the temperature is lowered.
PHYSICS – Calculating calcium-52 …
A multi-institution team led by Oak Ridge National Laboratory's Gaute Hagen used computation to corroborate experimental findings throwing calcium-52's status as a magic isotope into question. "If calcium-52 was magic, you would expect there to be a dip or kink in the graph showing the charge radii of calcium isotopes at calcium-52," Hagen said. "Our theory collaborators agreed with the experimental trend, and there were no signs of this kink." Atomic nuclei make up the vast majority of visible matter in the universe, and understanding the interactions between the neutrons and protons that make up nuclei has an impact on research spanning from the subatomic realm to astrophysical objects such as neutron stars. Nuclei are considered to be magic if they are composed of a designated series of numbers that include 2, 8, 20, 28 and 50. [Contact: Eric Gedenk, (865) 241-5497; [email protected]]
Cutline: After running a simulation proving calcium-48 was a magic isotope, ORNL researchers were surprised to find experimental data and simulations that suggested calcium-52 was not magic, as expected.
MANUFACTURING – 3-D printing with bamboo fiber …
Researchers at Oak Ridge National Laboratory are using bamboo fiber in 3-D printing experiments to determine whether bio-based feedstock materials are feasible in additive manufacturing. Chopped bamboo fibers were added to a bio-polymer resin to create bamboo-based pellets, resulting in a more sustainable material that can be used for manufacturing molds, prototypes, appliances and furniture. The research team 3-D printed a table that contains 10 percent bamboo fiber composite. "We are investigating the use of different types of cellulose fibers to develop feedstock materials with better mechanical performance that can increase the number of available composites and opportunities for sustainable practices," ORNL's Soydan Ozcan said. [Contact: Sara Shoemaker, (865), 576-9219; [email protected]]
Cutline: A 3-D printed table was manufactured using 10 percent bamboo fiber, an initial step toward sustainable practices using bio-derived materials.
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