Nanomaterial Yields Cool Results

A pinch of iron dramatically boosts the cooling performance of a material considered key to the development of magnetic refrigerators, report researchers at the National Institute of Standards and Technology (NIST) in the June 24 issue of the journal Nature. The achievement might move the promising technology closer to market, opening the way to substantial energy and cost savings for homes and businesses.

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.

Source: NIST

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• Tiny Miracles

Would You Like a Bouquet of Nanoflowers?

Today the Institute of Physics releases some of the most beautiful science images of the year so far, a collection of photomicrographs of tiny "flowers" and "trees" less than one thousandth the width of a human hair. The images are published in the Institute journal Nanotechnology.

These stunning images were taken by Ghim Wei Ho, a PhD student studying nanotechnology at Cambridge University. She has named some of her best photographs nanobouquet, nanotrees, and nanoflower because of their curious similarity to familiar organic structures such as flower-heads and tiny growing trees.

Ghim Wei's work involves making new types of materials based on nanotechnology and these flowers are an example of such a new material. Here, nanometre scale wires (about one thousandth the diameter of a human hair) of a silicon-carbon material (silicon carbide) are grown from tiny droplets of a liquid metal (Gallium) on a silicon surface, like the chips inside our home computers.

The wires grow as a gas containing methane flows over the surface. The gas reacts at the surface of the droplets and condenses to form the wires. By changing the temperature and pressure of the growth process the wires can be controllably fused together in a natural process to form a range of new structures including these flower-like materials.

Source: Institute of Physics

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• Tiny Miracles

Manipulating atoms and molecules has a vast and shining future for products ranging from drugs to medical gear to computers.

In the near nanotech future, today's medical instruments will seem crude. Take magnetic resonance imaging of the brain. A current MRI offers surgeons a macro view, comparable to a satellite picture of the Earth. Applying nanotechnology will enable the MRI to create the equivalent of street-by-street photos.

Pharmaceutical companies will use nanotech to develop molecules to treat neurological diseases. In the computer industry the possibilities are endless, such as computers the size of a dot. The German chemical giant BASF is working on a toothpaste that will not only resist tooth decay--the familiar ad slogan--but reverse it by rebuilding tooth enamel.

Prompted by what amounts to an international footrace for nanotechnology supremacy, Congress is about to sign off on $2.4 billion in research grants for nanotech.

Source: Forbes

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