the engineers made their breakthrough using the process of selective doping, in which an impurity is added to a material that changes its properties. The process also shows promise for boosting vehicles’ fuel economy and reducing heat produced by semiconductors, a potentially important development for more efficient energy production.
Working at the nanometer level — a pinhead has a diameter of 1 million nanometers — the engineers added metal nickel to magnesium oxide, a ceramic. The resulting material contained clusters of nickel atoms no bigger than 10 square nanometers, a 90 percent size reduction compared to today’s techniques and an advancement that could boost computer storage capacity.
“Instead of making a chip that stores 20 gigabytes, you have one that can handle one terabyte, or 50 times more data,” Narayan says.
By introducing metallic properties into ceramics, Narayan says engineers could develop a new generation of ceramic engines able to withstand twice the temperatures of normal engines and achieve fuel economy of 80 miles per gallon. And since the thermal conductivity of the material would be improved, the technique could also have applications in harnessing alternative energy sources like solar energy
The engineers’ discovery also advances knowledge in the emerging field of “spintronics,” which is dedicated to harnessing energy produced by the spinning of electrons. Most energy used today is harnessed through the movement of current and is limited by the amount of heat that it produces, but the energy created by the spinning of electrons produces no heat. The NC State engineers were able to manipulate the nanomaterial so the electrons’ spin within the material could be controlled, which could prove valuable to harnessing the electrons’ energy. The finding could be important for engineers working to produce more efficient semiconductors.
Working with Narayan on the study were Dr. Sudhakar Nori, a research associate at NC State, Shankar Ramachandran, a former NC State graduate student, and J.T. Prater, an adjunct professor of materials science and engineering. Their findings are published as “The Synthesis and Magnetic Properties of a Nanostructured Ni-MgO System,” which appeared in the June edition of JOM, the journal of the Minerals, Metals and Materials Society. The research was sponsored by the National Science Foundation.
The synthesis and magnetic properties of a nanostructured Ni-MgO system
We have investigated the magnetic properties of the Ni-MgO system with an Ni concentration of 0.5 at.%. In asgrown crystals, Ni ions occupy substitutional Mg sites. Under these conditions the Ni-MgO system behaves as a perfect paramagnet. By using a controlled annealing treatment in a reducing atmosphere, we were able to induce clustering and form pure Ni precipitates in the nanometer size range. The size distribution of precipitates or nanodots is varied by changing annealing time and temperature. Magnetic properties of specimens ranging from perfect paramagnetic to ferromagnetic characteristics have been studied systematically to establish structure-property correlations. The spontaneous magnetization data for the samples, where Ni was precipitated randomly in MgO host, fits well to Bloch’s T3/2-law and has been explained within the framework of spin wave theory predictions.
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