Atomic Force Microscopes Get 'Tougher'

Atomic Force Microscopes (AFM) are used for the purpose of measurement, imaging, and manipulation of Nano materials. The microscope uses the principle of piezoelectricity to sense the surface of the material in all the three dimensions. Scientists have developed a new assembly for the sensor of the atomic force microscope that gives the accurate picture of the nonosurfaces at pressure of 100 atmospheres and temperature as high as 350 K.

The technology is developed keeping in mind the difficulties met while operating the AFM in #-Link-Snipped-#the carbon sequestration processes. Carbon sequestration is one of the ways to reduce the greenhouse effect and the subsequent global warming. In this technique, carbon dioxide is captured as pure by-product. This is easily possible in petroleum refineries and power plants. The percentage of carbon in the flue gases in these industries is quite high. After carbon dioxide is captured, it is stored permanently in artificial capture pits. The sequestration process is achieved using subsurface saline aquifers, reservoirs, ocean water, aging oil fields, or other carbon sinks.

Now one must have got confused as to what relation exists between the carbon sequestration process and the AFM? The carbon sequestration processes are not efficient, as the carbon behavior in the geological storehouses cannot be monitored with required precision. The AFMs cannot sustain the pressure and temperature limits that are commonly found 0.5-1 mile below the earth’s surface. As a result, the performance of the stored carbon dioxide in years to come cannot be predicted and the efficiency value of the “carbon pit” in coming decades (or even centuries!) cannot be predicted.

The scientists at Pacific Northwest National Laboratory, Wright State University and Lawrence Berkeley National Laboratory have come with a new improved assembly for the AFM which could get sharp pictures and real time reaction of carbon dioxide with other minerals even in adverse conditions. The scientists were successful in getting images of the reaction between supercritical carbon dioxide and calcite mineral at an interval of about 6 minutes. They injected the captured carbon dioxide in porous rock formations where the CO2 is transformed in supercritical stage meaning that CO2 forms a mixture showing properties of both liquid and gas. The researchers aimed at finding out the performance of the CO2 with the minerals at depths of half mile. With the new high-pressure enabled assembly, they captured the reaction of supercritical CO2 with the hydrated calcite surface with precision. Calcite being a common mineral, it was not very difficult to prepare clean flat calcite surface for testing the new assembly for AFM.

With this knowledge, the geologists could now determine the possible feasibility of the selection of the site for carbon sequestration in future. The earlier AFMs could process and image the surfaces only when the surface pressures did not exceed 50 atm and variation of temperature in small range. According to Kevin Rosso, a PNNL Fellow who worked on this project, "The information from the new apparatus is key to more fully understanding geochemical processes under a much wider range of geologically relevant conditions-especially those relevant to carbon sequestration.”

The applications of the new AFM technology also extend to the study of reactions occurring at higher pressures. The material surface can be visualized in 3D after the reactions of two elements in a better way with the help of new device. However, as of now, the primary area of application is the study of reactions between CO2 and various minerals that are found in possible carbon sequestration sites.

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