Welches C/N-Verhältnis führt bei sehr hohen Drücken und Temperaturen zur Polymerisierung von kleinen Molekülen des Systems C-H-N-O?
Zusammenfassung der Projektergebnisse
Chemical reactions of small molecules consisting of light elements (e.g. carbon C, hydrogen H, nitrogen N and oxygen O) have been of interest because of the unique and surprising chemical, physical and mechanical properties of their reaction products. Well-known examples include the polymerisation of carbon dioxide, nitrogen and carbon monoxide. The aim of this project was not only to synthesise novel materials in the chemical system C-H-N-O but also attempted to understand the polymerisation reaction better and especially to understand which carbon content is required for a polymerisation of those molecules. In order to achieve this aim, I performed high pressure and high temperature experiments in laser heated diamond anvil cells. The starting materials for those experiments were solid organic molecules and gas mixtures of molecules with different carbon to nitrogen ratios ranging from C:N = 1:2 to C:N = 1:20. The main tools that I used for the characterisation of the compounds were X-ray diffraction, Raman spectroscopy, luminescence spectroscopy, second harmonic generation and optical microscopy. In order to understand a chemical reaction one has to know the starting material itself. Therefore, all of the performed studies started with experiments where the respective compound had been analysed upon pressure increase only in order to understand its behaviour at high pressures without heating. After that, laser heating experiments were performed with all compounds. I was able to induce chemical reactions in all studied compounds. Here, the derivatives urea, CH4N2O, and carbohydrazide, CH6N4O, were particularly interesting, because they showed similar non-crystalline reaction products which are presumably polymerisation products. The two gas mixtures with very small C:N ratios of 1:10 and 1:20 also showed a chemical reaction upon laser heating. However, I was not able to determine whether the reaction was a polymerisation or not. Due to the unforeseen early termination of the project, I was not able to fully characterise all of the reaction products and to determine the C:N region where polymerisation reactions are possible. However, the promising results obtained in this project should be investigated further.
Projektbezogene Publikationen (Auswahl)
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“Phase transitions and chemical reaction of urea at high pressures and temperatures”. Joint AIRAPT-25 & EHPRG-53, Madrid, Spain, September 2015
N. Schrodt, L. Bayarjargal, W. Morgenroth and B. Winkler
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“Urea at high pressures and high temperatures”. 23th Annual Meeting of the German Crystallographic Society, Göttingen, Germany, March 2015
N. Rademacher, L. Bayarjargal, W. Morgenroth and B. Winkler
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“5-aminotetrazole monohydrate up to 51 GPa: pressure-induced phonon softening and phase transitions”. EHPRG-54, Bayreuth, Germany, September 2016
N. Schrodt, W. Morgenroth, L. Bayarjargal and B.Winkler
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“Pressure-induced phonon softening and phase transition of 5-aminotetrazole monohydrate”. 24th Annual Meeting of the German Crystallographic Society, Stuttgart, Germany, March 2016
N. Schrodt, W. Morgenroth, L. Bayarjargal and B.Winkler
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“Understanding chemical reactions of small molecules at extreme conditions by means of high pressure pair distribution function analysis”. THERMEC’2016, Graz, Austria, June 2016
N. Schrodt, L. Bayarjargal, W. Morgenroth and B.Winkler
