Showing posts with label aerosoles. Show all posts
Showing posts with label aerosoles. Show all posts

Tuesday, January 18, 2011

Aerogels: The lightest stuff gets lighter

Known as “the lightest material on the planet,” aerogels consist mostly of air. But the services this stuff could potentially provide are substantial.

Their low thermal and acoustic conductivity makes them superb heat and noise insulators. They’re very absorbent, perfect for an oil spill or umm, kitty litter. And depending on their construction, they can specifically filter certain toxins or pollution particles.

Unfortunately, their construction doesn’t come easy, especially when made out of carbon nanotubes (silica, metal oxides, or other carbon-based materials typically comprise aerogels). But a team of scientists is reporting they’ve fabricated a multi-walled carbon nanotube (MWCNT) aerogel.
Published in ACS Nano, the study describes this new “frozen smoke” as the lightest of its kind, with a density of just four milligrams per cubic centimeter.

The chemists, from University of Central Florida, removed the moisture from a wet gel of dispersed carbon nanotubes, leaving a material with honeycomb structures with varying degrees of porosity. The below image shows the pristine multi-walled carbon nanotubes at each step of the fabrication process.

The MWCNT aerogel has a large surface area and conducts electricity very well but not heat, so its use in electronics is far-reaching. After testing the aerogel’s compressibility, the chemists also discovered it is highly squishable (video) and recovers quickly.

This sensitivity to pressure and its porosity make the material a good candidate for sensing chemical vapors and changes in pressure. So if you tend to think, heft connotes value, you may be wrong in the case of areogels.

Tuesday, November 10, 2009

ESA Climate Studies - Aerosol Gas Survey

Aerosol optical depth measured by SEVIRI. Climate studies to benefit from 12 years of satellite aerosol data

Aerosols, very small particles suspended in the air, play an important role in the global climate balance and in regulating climate change.

They are one of the greatest sources of uncertainty in climate change models. ESA's GlobAerosol project has been making the most of European satellite capabilities to monitor them.

Using data from the Along Track Scanning Radiometer-2 on the ERS-2 satellite, the Advanced Along Track Scanning Radiometer and the Medium Resolution Imaging Spectrometer on Envisat and the Spinning Enhanced Visible & InfraRed Imager (SEVIRI) instrument on the Meteosat Second Generation, GlobAerosol has produced a global aerosol dataset going back to 1995. The full dataset is available on the GlobAerosol website.

Some aerosols occur naturally, originating from sea-spray, wind-blown dust, volcanic eruptions and biochemical emissions from oceans and forests, while others are produced through emissions from industrial pollution, fossil-fuel burning, man-made forest fires and agriculture.

Wind-blown dust
They are important because they strongly affect Earth’s energy balance in two ways: they scatter and absorb sunlight and infrared emission from Earth's surface, and act as condensation nuclei for the formation of cloud droplets. According to the Intergovernmental Panel on Climate Change, these effects tend to cool the planet to almost the same degree as carbon dioxide emissions warm it. These estimates are uncertain, however, so more data are needed.

Satellite data can provide essential information on the global distribution of aerosols to help understand the impact of these processes for the purposes of predicting weather and climate as well as for monitoring the transport of industrial pollution.