Category: Nanoscale Bulk Technologies

from the the-diamond-age dept.
An article on Space Daily.com reports researchers at Vanderbilt University have created a prototype diamond-based thermionic solar cell that is potentially 3 to 4 times more efficient than conventional silicon-based cells. The operation of the diamond cells depends on their nanoscale properties.

The cells use diamond films covered with millions of microscopic pyramids: about 10 million per square centimeter. When heated, the tips of these pyramids, which are only a few atoms across, emit streams of high-energy electrons. At the nanoscale, the laws of physics favor the efficient production of high-energy electrons. "It is this nanoscale physics that makes the device work," says Vanderbilt Prof. Timothy S. Fisher, who led the research. He collaborated with Weng Poo Kang, an associate professor of electrical engineering and computer science. The bottom of the diamond film is laminated to a metal sheet that acts as a cathode. When heated, the tips of the tiny pyramids emit streams of electrons that flow across the intervening vacuum to the anode, creating an electric current.

from the active-materials dept.
Researchers at Sandia National Laboratory and the University of New Mexico report they have created what they call self-assembling "intelligent nanostructures" that report on their environment by changing color from blue to fluorescent red under mechanical, chemical, or thermal stress.
According to their press release, the material can distinguish between different solvents by changing color. The material also can report changes in mechanical stress and temperature. When the environmental disturbance is removed, the structures change back to their original color in some cases, making them potentially reusable.
The Sandia/UNM fabrication method evenly pre-distributes monomers — simpler precursors of polymers — within a silica matrix through self-assembly. Exposure to UV light polymerizes the monomers into conjugated polymers housed in nanoscopic channels that penetrate the matrix of the material. The result is a nanocomposite that is mechanically robust, optically transparent, and produces telltale changes of color under changing environmental conditions. The researchers claim they also can control interactions between polymer units that affect a materialís electrical and optical properties.
Aspects of the work are also reported in the 19 April 2001 issue of Nature.

from the alternatives dept.
A simple method of producing non-carbon nanotubes has been developed by O.G. Schmidt and K. Eberl, scientists at the Max Planck Institute for Solid State Research in Stuttgart, Germany. The new technique makes it possible to prepare tubes from very different substances, such as silicon, as well as to vary their dimensions and to deposit the nano objects very exactly. Their method employs a strained semiconductor sheet that springs free of a crystalline substrate that holds it flat; the sheet then curls up into a nanotube.

According to the researchers, "Deposition techniques are capable of combining materials of almost unlimited diversity, including semiconductors, insulators, metals, polymers, etc. This richness will create new nano-objects of unknown diversity, which will find their fortune in the wide and interdisciplinary fields of micro- and nano-electromechanical systems."

Details of the work are reported in Nature, v410:168 (8 March 2001).

from the if-it's-broke-no-need-to-fix-it dept.
JohnPierce writes about work at UIUC published in Nature:"An AP article on Yahoo says: 'Researchers have developed the first material that automatically repairs itself, offering a potential way of fixing the hairline cracks that develop in the space-age composites used in everything from tennis rackets to aircraft. The scientists' secret: tiny capsules of glue that are added to the composite material… To heal tiny cracks automatically, the Illinois researchers sprinkled capsules about the thickness of a human hair throughout an experimental fiberglass-like compound. When a crack appeared, capsules in its path broke open, spilled their contents and sealed the cracks.'
Food for thought: Micro encapsulation is already in widespread use in medicine and food, so using it in construction materials is a natural progression. Nanotechnology will be able to encapsulate high strength repair substances that will survive high temperatures. Self repair will no doubt become a standard Nano application."