Tharangattu Narayanan, left, and Jaime Taha-Tijerina (Jeff Fitlow/Rice University)
Materials scientists at Rice University in Houston have developed a process for enhancing the efficiency of lubricants to help remove excess heat in electric-power devices from micro-scale components to industrial transformers. The findings of graduate student Jaime Taha-Tijerina, postdoctoral researcher Tharangattu Narayanan, and colleagues appear in the journal ACS Nano (paid subscription required).
The team focused their inquiry on fluids for insulating and cooling energy systems. Electrical transformers are filled with fluids that cool and insulate the core and windings inside, as well as components that must remain separated from each other to keep voltage from leaking or shorting. Taha-Tijerina brought to the research his first-hand experience working for transformer manufacturer Prolec GE, in Monterrey, Mexico.
The researchers found that a very tiny amount of hexagonal boron nitride (h-BN) particles suspended in standard mineral oils are highly efficient at removing heat from a system. These h-BN particles have a two-dimensional structure and are related to carbon-based graphene, but even in minute quantities can have a big impact. “We found that 0.1 weight percentage of h-BN in transformer oil,” says Narayanan, “enhances it by nearly 80 percent.”
The h-BN nanosheets, about 600 nanometers wide and up to five atomic layers thick, disperse well in oil. Unlike graphene, which is highly conductive, however, h-BN particles are highly resistant to electricity. The researchers also found that oil maintained its viscosity or fluid resistance with the addition of nanoparticle fillers.
Taha-Tijerina tried using other materials to enhance the transformer oil — alumina, copper oxide, and titanium oxide — but none of the compounds has the combination of qualities exhibited by h-BN. Also, as noted by Rice materials scientist Pulickel Ajayan and lab chief where the research was conducted, “the two-dimensional nature of the fillers keeps them stable in oils without settling down for long periods of time.”
Read more: Energy Department to Fund Nanolubricant Plant
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