2008 June 26 Thursday
Nanomaterials Reduce Energy Needed To Boil Water

It is happening down at the nanoscale.

Troy, N.Y. — Whoever penned the old adage “a watched pot never boils” surely never tried to heat up water in a pot lined with copper nanorods.

A new study from researchers at Rensselaer Polytechnic Institute shows that by adding an invisible layer of the nanomaterials to the bottom of a metal vessel, an order of magnitude less energy is required to bring water to boil. This increase in efficiency could have a big impact on cooling computer chips, improving heat transfer systems, and reducing costs for industrial boiling applications.

This would be useful for camping equipment where cooking fuel can be in short supply.

The researchers weren't trying for this valuable result. So much for central planning.

“Like so many other nanotechnology and nanomaterials breakthroughs, our discovery was completely unexpected,” said Nikhil A. Koratkar, associate professor in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer, who led the project. “The increased boiling efficiency seems to be the result of an interesting interplay between the nanoscale and microscale surfaces of the treated metal. The potential applications for this discovery are vast and exciting, and we’re eager to continue our investigations into this phenomenon.”

30 times more bubble action. Sounds like an advertisement for a bathroom cleaner.

Koratkar and his team found that by depositing a layer of copper nanorods on the surface of a copper vessel, the nanoscale pockets of air trapped within the forest of nanorods “feed” nanobubbles into the microscale cavities of the vessel surface and help to prevent them from getting flooded with water. This synergistic coupling effect promotes robust boiling and stable bubble nucleation, with large numbers of tiny, frequently occurring bubbles.

“By themselves, the nanoscale and microscale textures are not able to facilitate good boiling, as the nanoscale pockets are simply too small and the microscale cavities are quickly flooded by water and therefore single-use,” Koratkar said. “But working together, the multiscale effect allows for significantly improved boiling. We observed a 30-fold increase in active bubble nucleation site density — a fancy term for the number of bubbles created — on the surface treated with copper nanotubes, over the nontreated surface.”

Does this bubbling cause a pot to absorb external heat more rapidly? Would it reduce heat loss from convection of air? I would expect the bubbles would carry away heat more rapidly so that more heat would get captured from a cooking flame.

By Randall Parker    2008 June 26 10:37 PM   Entry Permalink | Comments (13)
2007 July 29 Sunday
Thin Nanosheet Strong As Plexiglass

Fun with nanotechnology.

Tightly packed molecules lend unexpected strength to nanothin sheet of material

Scientists at the University of Chicago and Argonne National Laboratory have discovered the surprising strength of a sheet of nanoparticles that measures just 50 atoms in thickness.

“It’s an amazing little marvel,” said Heinrich Jaeger, Professor in Physics at the University of Chicago. “This is not a very fragile layer, but rather a robust, resilient membrane.”

Even when suspended over a tiny hole and poked with an ultrafine tip, the membrane boasts the equivalent strength of an ultrathin sheet of plexiglass that maintains its structural integrity at relatively high temperatures.

“When we first realized that they can be suspended freely in air, it truly surprised all of us,” said Xiao-Min Lin, a physicist at Argonne’s Center for Nanoscale Materials.

They used gold particles separated by organic (probably meaning carbon-based) nanoparticles.

The experimental material consisted of gold particles separated by organic “bumpers” to keep them from coming into direct contact. The research team suspended this array of nanoparticles in a solution, then spread the solution across a small chip of silicon, a popular semiconductor material. When the solution dried, it left behind a blanket of nanoparticles that drape themselves over holes in the chip, each hole measuring hundreds of nanoparticles in diameter. Then the researchers probed the strength of the freely suspended nanoparticle layer by poking it with the tip of an atomic force microscope.

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The research team also found that the material held together when heated until reaching temperatures of 210 degrees and beyond.

What I wonder: Will nanomaterials made from more plentiful elements perform just as well at many tasks as rarer elements which we will run out of? How much will nanotech allow us to develop substitutes for rarer elements? Once we develop renewable substitutes for fossil fuels will we suffer shortages of anything besides land?

By Randall Parker    2007 July 29 08:33 AM   Entry Permalink | Comments (4)
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