Thermographic picture of the involved authors.
Source: BAM, Division Thermographic Methods
Mechanochemistry is widespread in the synthesis of organic, metal-organic and inorganic compounds. There, solid materials react due to the mechanical impact created by the collision with milling balls. Mechanochemical syntheses are fast, mostly quantitative and easy to implement in the laboratory. The reduction of the amount of solvent is a huge advantage in comparison to conventional synthesis and leads the way to more environmentally friendly and green synthesis routes.
Different physico-chemical effects occur simultaneously during the milling process. Therefore, it is difficult to get insights into the underlying mechanisms. For the investigation of mechanochemical syntheses in real time a new combination of three different analytical methods was developed. The combination of synchrotron X-ray diffraction, Raman spectroscopy and thermography enables the correlation of the structural development with the influence of temperature. With this combination it is possible to get information on the crystalline, molecular and temperature state that occurs during milling.
Exemplarily, three different mechanochemical reactions were investigated in situ. A correlation between chemical composition and small changes in temperature could be determined. General trends in temperature shifts were detected. In the beginning of the reaction the impact of the milling balls leads to a mixing of reactants and the reduction of the particle size accompanied by a rapid rise in temperature. If no reaction takes place the difference in temperature reaches a plateau which is an equilibrium of heating and cooling effects. An additional increase in temperature results from chemical energy. This energy is assembled by the reaction and latent crystallization heat. The release of by products, e.g. water, leads to local plateaus or a decrease in the overall temperature of the milling jar. The presented setup is suitable for the detection of all intermediates that are discussed in literature for mechanochemical syntheses. Combining the three different analytical methods for real time analysis increases the gain of information dramatically and allows a deeper understanding of the progression of mechanochemical syntheses.
Thermographic picture of the involved authors.
Source: BAM, Division Thermographic Methods and Division Structure Analysis
In situ investigations of mechanochemical one-pot syntheses
Hannes Kulla, Sebastian Haferkamp, Irina Akhmetova, Mathias Röllig, Christiane Maierhofer, Klaus Rademann, Franziska Emmerling
Angewandte Chemie International Edition, 2018, Vol. 57, 20, pp 5930-5933
BAM Department Analytical Chemistry; Reference Materials, Division Structure Analysis and Department Non-destructive testing, Division Thermographic Methods