Images taken by the atomic force microscope of the mineral calcite, 6 minutes apart, as it is exposed to and progressively reacts with supercritical carbon dioxide.

It
is a challenging task to study the behavior of CO₂ with instruments
under geological conditions involving high-pressure. A new atomic force
microscope (AFM) was developed by scientists at Lawrence Berkeley
National Laboratory, Wright State University, and Pacific Northwest
National Laboratory to withstand the pressure encountered by stored
 greenhouse gases underground.

Scientists
can view images and movies of reactions as and when they take place
under similar conditions as at a carbon sequestration site using the new
AFM. Removing CO₂ from industrial emissions and accumulating it
underground enables researchers to give answers to some basic questions
such as the interaction of carbon dioxide with adjacent mineral
surfaces. The new device provides the required answers.

CO₂
is injected into porous rocks present underground at a distance of more
than half a mile below the surface, where the pressure and temperature
conditions are favorable to sustain CO₂ in a supercritical fluid state.
At this state, CO₂ exhibits both liquid and gaseous properties.
Researchers wanted to observe a real time viewing of the reactions
taking place under native environmental conditions. The chemical
interactions between minerals present in rock formations and
supercritical CO₂ could be understood better with the help of the
images.

The
researchers designed an apparatus to enable an atomic force microscope
to withstand temperatures approximately up to 350 K and pressures of 100
atmospheres. Scientists used this microscope to produce images and a
real-time film of the reaction of supercritical CO₂ with a hydrated
calcite surface. Calcite surfaces are easy to prepare and they can be
used for AFM studies. It can be used to observe other chemical reactions
taking place at high pressures.

SOURCE