Nanomaterial Yields Cool Results

By adding a small amount of iron (about 1 percent by volume), the NIST team enhanced the effective cooling capacity of the so-called “giant magnetocaloric effect” material by 15 to 30 percent. The result, writes materials scientist Virgil Provenzano and his NIST colleagues, “is a much-improved magnetic refrigerant for near-room-temperature applications.”

The original material—a gadolinium-germanium-silicon alloy—already is considered an attractive candidate for a room-temperature magnetic refrigerant. However, its cooling potential is undercut by significant energy costs exacted during the on-and-off cycling of an applied magnetic field, the process that drives the refrigeration device. These costs—called hysteresis losses—translate into commensurate losses of energy available for cooling.

The iron supplement overcomes this disadvantage. It nearly eliminates hysteresis and the associated energy cost, permitting the material to perform near the peak of its potential.

Independently suggested by two scientists in the 1920s, earning one the Nobel Prize in 1949, magnetic refrigerators offer sizable prospective advantages over the century-old technology of today’s vapor-compression cooling systems. Potential pluses include substantial gains in energy efficiency, lower cost of operation, elimination of environmentally damaging coolants, and nearly noise- and vibration-free operation.