| January
2006 |
| |
|
Tungsten
Oxide Microducts for Chemical Sensing
Richard
Cavicchi, Process Measurements Division
|
|
|
| |
| Advances in nanotechnology
are creating a growing repertoire of nanostructures. Nanotubes, nanowires,
nanoribbons, and nanospheres are finding applications in emerging fields
such as nanoelectronics and nanofluidics. Researchers working collaboratively
at the University of MD and the Chemical Science and Technology Laboratory
at NIST recently discovered a process that produces hollow tungsten oxide
"beams" or "microducts" with rectangular, cross-sectional dimensions below
1 micrometer and lengths of up to 300 micrometers. These tiny ducts may
find uses as structural elements in chemical sensors, microelectromechanical
systems or as submicron fluidic channels. The microducts beams are formed
by treating a tungsten film in a H2/Ar plasma at temperatures between 550
°C and 620 °C. The treatment must occur in a regime of limited mass transfer
of gas-phase species to the surface and a trace amount of oxygen must be
present. This work was recently featured on the front page of the website
of the Materials Research Society and is published in the Journal of Materials
Research [Vol. 20, No. 11 (2005) 2889]. |
| |
| |
| March
2006 |
| |
Researchers Perform On-the-Fly
Measurement
of the Length
of Nanowires
Soo
Kim / Michael
Zachariah, Process Measurements Division
|
|
 |
| |
| Nanowires comprise
a subset of nanoparticles as building block in nanotechnology. One of the
key issues in eventual product realization is manufacturability and quality
control. In addition, the formation of new nanoparticle/fiber based materials
in bulk quantities increases the level of concern for human health and the
environment. These requirements call out for metrologies than can measure
physical/chemical properties during manufacturing as well as monitor transport
and fate of these materials in the environment. Researchers in the Process
Measurements Division have recently shown how ion-mobilty of gas-phase suspended
nanowires can be used to measure their length. Essentially the approach
is akin to electrophoresis, but in the gas-phase. The actual experiments
demonstrating the method were conducted on carbon nanotubes which the researchers
grew during the actual measurement process, and showed how the diagnostic
tool could be used during manufacturing. They have also used the method
to determine the growth kinetics of nanotubes for various temperatures,
catalyst size, and carbon growth source, and have shown that aerosol grown
nanotubes grow 100X faster than substrate grown materials. Current work
is focusing on a model for how the nanotubes align and transport in the
presence of an applied field. The method is also being considered as a tool
to deliver constant length fibers for toxicology studies. |
