Liquid carbon, which could be found inside giant planets, plays an important role in the development of future nuclear fusion technologies, a clean and almost unlimited source of energy. However, until now very little was known about carbon in its liquid form as it was virtually impossible to study in the laboratory. At ambient pressure the carbon does not melt, but becomes immediately gaseous, and only at high pressures and temperatures does the carbon become liquid.
Laser compression is known to convert solid carbon into liquid in fractions of a second. "The challenge is to use these fractions of a second for measurements, and in a way that was previously unimaginable, this has been achieved using DIPOLE 100-X, a high-energy laser that can create conditions with pressures of up to 10,000 tons per square centimetre and temperatures above 10,000 degrees in a very short time", comments Daniel Errandonea, professor of applied physics, researcher at the Institute for Materials Science (ICMUV), located in the Science Park of the University of Valencia (UV) and co-author of the work that has just published Nature.
Thanks to the capabilities of the DIPOLE 100-X, installed in the European free electron X-ray laser (EuXFEL), the research team has for the first time combined powerful laser compression with ultra-fast X-ray analysis and large area X-ray detectors.
According to the article, in the experiment high-energy pulses from the laser create compression waves through a solid carbon sample and liquefy the material for one billionth of a second. During this brief period, the sample is irradiated with EuXFEL X-rays, and carbon atoms scatter X-ray light in a similar way to how light diffracts into a grid. Thus, the created diffraction pattern provides valuable information about the distribution of atoms in liquid carbon, how they are organized and the interactions between them.
"Until now, the theoretical predictions on liquid carbon structure and melting point had diverged significantly. Their precise knowledge is crucial for planetary modelling and the design of better materials for nuclear fusion power generation", David Santamaría-Pérez, ICMUV researcher and co-author of the paper
The results reveal that the structure of liquid carbon is similar to that of solid diamond, where each carbon atom is surrounded by four other carbon atoms. This arrangement of carbon atoms is also adopted in a wide variety of organic compounds and is fundamental to the structure of many materials. They also allow the determination of the melting point, a crucial information for use in environments where temperature is a critical factor, such as fusion reactors. "Until now, the theoretical predictions on liquid carbon structure and melting point had diverged significantly. Their precise knowledge is crucial for planetary modelling and the design of better materials for energy generation by nuclear fusion," concludes Professor David Santamaría-Pérez, member of the ICMUV team, Also co-author of the article and member, together with D. Errandonea, of the Advanced Materials programme of the Complementary Plan for R+D+i.
The study is an international collaboration led by researchers from the University of Rostock and the Helmholtz-Zentrum Dresden-Rossendorf. In addition to the ICMUV, the work involves the universities of Edinburgh and Oxford, the national laboratories of Los Alamos and Livermore, the Sorbonne University, the Paul Scherrer Institute, and 35 other scientific institutions from Europe, USA and Asia.
Source: UV News
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