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When carbon dioxide and silica combine – new material created at ESRF


Scientists have created a new material by successfully combining for the first time, carbon dioxide and silica. The gas and solid were previously thought to be incompatible but under extremely high pressure and temperatures at the European Synchrotron, the ESRF, they combined to produce a hard, light carbon-rich crystal. The material remains in its new state even when conditions are returned to standard conditions. The results, published in Nature Communications (30 April 2014) have implications for planetary studies and could influence areas such as optical fibre technology.

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“After several years of strong technological efforts and synergetic thinking, we succeeded in joining what seemed to be two incompatible worlds. Carbon dioxide, a famous polluting gas and silica, a solid, a famous mineral and one of the most important materials in everyday life as it is found in glasses, windows, etc.”, said lead author Mario Santoro from Istituto Nazionale di Ottica-Consiglio Nazionale delle Ricerche (INO-CNR) and Laboratorio Europeo di Spettroscopie non Lineari (LENS).

 “Now these two worlds come together in a new chemical reaction conducted at high pressure and temperature conditions such as those found in planetary interiors, forming a novel, hard CO2-SiO2 crystalline compound”, he added.

The new material with an average chemical formula of C0.6Si0.4O2 is six to seven times less compressible than quartz. It was created under extreme conditions at the ESRF. The team of researchers from Italy and France used a diamond anvil cell, a device that allows samples to be subjected to extreme pressures, in this case 200,000 atmospheres. They loaded it with carbon dioxide and silica and heated the sample with a laser to temperatures exceeding 4000 degrees kelvin.

“Using extreme conditions of pressure and temperature and after many attempts, we were able to synthesize a new crystalline oxide of silicon and carbon with a structure based on that of the mineral cristobalite, in which both types of atoms have four oxygen neighbours. This represents an entirely new vision of the chemistry of oxides”, said Julien Haines from the Institut Charles Gerhardt Montpellier, CNRS and Université Montpellier 2.

Gaston Garbarino from the ESRF who is one of two scientists from ESRF to be named on the paper, said: “From the chemical point of view, the application of pressure and temperature is an excellent tool to force the atoms to be confined, increase their interactions and adopt new arrangements and connections, i.e. the synthesis of new materials. Besides the fact that this breakthrough will have an impact in materials science due to the possibility of designing new materials and applications based on CO2-SiO2; it gives a new way of interpreting the chemistry of oxides”. The composite provides an updated view of the periodic table.

The results could be especially significant for Earth and planetary sciences because the new material was formed under extreme conditions that are similar to those found both deep inside Earth and on other planets.


Structure of the new crystalline oxide of silicon and carbon

Credit for the structure image: M. Santoro,
F. A. Gorelli, R. Bini, A. Salamat,
G. Garbarino, C. Levelut, O. Cambon,
J. Haines.

Any novel chemical compound made from substances commonly found in the planets could be expected to be of interest to scientists modelling the structure, composition and history of the planets; in the case of the original components of this new material, carbon dioxide is the major constituent of the atmosphere on Mars and silica is found in Earth and other rocky planets.

With the conditions in such extreme environments being similar to those recreated at the ESRF for this experiment the team believes the new composite of carbon dioxide and silica could form, or may have formed in the past within planets inside or outside of our solar system. It is likely they consider, that carbon, a key component of the atmosphere of Mars and silicon, found inside the Earth and other rocky planets would have come into contact with each other at some point. The team believes the new mineral could be considered, therefore, for future studies on the structure and history of rocky planets.

“Of course we note that our synthesis conditions are far from the present geothermal curve of the Earth”, remarked Santoro. “When placed under 200,000 atmospheres of pressures the corresponding temperatures in our experiment were much higher than those in the Earth upper mantle. Nevertheless, these synthesis conditions may be close to those in the interior of other rocky planets or even that of the Earth in some primordial stage of the solar system. Given that our findings modify the current view of oxide chemistry, future studies on Earth’s mantle that deal with carbon and silicon compounds could face a higher degree of complexity than thought so far”.

The material also has characteristics that could prove interesting for applications in mechanics and heat transfer technology. It is expected that like other hard materials, including diamond, the new crystal will have very high thermal conductivity.

It is also anticipated that the material could be important for optical fibre technology: “The new material is expected to exhibit lower index of refraction than silica. Therefore, the demonstration of chemical compounds between CO2 and silica indicates that it should be possible, in principle, to obtain a new class of materials with application-tailored index of refraction. This is very important for optical fibre technology”, said Santoro. “However, all of these potential technological applications are not something which is just “beyond the door”, he concluded. 

Notes to editors

The details of the paper are as follows:

Title: Carbon enters silica forming a cristobalite-type CO2-SiO2 solid solution.

Journal: Nature Communications, DOI: 10.1038/ncomms4761.

Further information

Information about the ID27 beamline can be found here.


Authors and affiliations:

  1. Mario Santoro, Istituto Nazionale di Ottica-Consiglio Nazionale delle Ricerche (INO-CNR), and Laboratorio Europeo di Spettroscopie non Lineari (LENS), 50019 Sesto Fiorentino, Italy;
  2. Federico A. Gorelli, INO-CNR and LENS;
  3. Roberto Bini, LENS, and Dipartimento di Chimica dell’Università di Firenze;
  4. Ashkan Salamat, European Synchrotron Radiation Facility (ESRF), 38043 Grenoble, France;
  5. Gaston Garbarino, ESRF;
  6. Claire Levelut, Laboratoire Charles Coulomb, CNRS-Univ. Montpellier 2, 34095 Montpellier, France;
  7. Olivier Cambon, Institut Charles Gerhardt Montpellier, CNRS-Univ. Montpellier 2, 34095 Montpellier, France;
  8. Julien Haines, Institut Charles Gerhardt Montpellier, CNRS-Univ. Montpellier 2, 34095 Montpellier, France.



Top image: Members of the research team, from left to right: Federico Gorelli, Gaston Garbarino and Mario Santoro. Credit: ESRF/C. Argoud