A big part of our research is focused on the chemistry that happens as our materials form. This is quite challenging to study since many of our materials are prepared in a furnace and the main transformations occur at high temperatures (>600 ºC) and often under inert atmospheres such as nitrogen. A lot of our work in the past has used ‘quenching’ studies – simply switching off the furnace at certain temperatures and studying the materials at various stages during the heating process. This is very useful and can offer some fascinating insight into how crystalline phases evolve during synthesis. More recently, we have been starting to move into in situ studies. For example, we have been working recently on the I11 beamline at the Diamond Light Source, studying how crystalline nanoparticles evolve during sol-gel synthesis of ceramics. The set-up at I11 means that we can heat the sample in a sealed capillary, taking an X-ray diffraction pattern every 10 seconds to watch in real time how our system is developing!
Another fantastic mechanism study recently was some work done with the Complex Functional Materials Group at the University of Bristol. Using a transmission electron microscope fitted with a heating stage, we were able to watch nanowires of an yttrium barium copper oxide grow. Check out the full details of the work, published in Science!
One of the most interesting recent projects was a collaboration with colleagues at the Max Planck Institute for Colloids and Interfaces. We studied the mechanism of formation of graphitic nanostructures from a cellulose precursor. This is catalyzed by iron and again, it’s a simple procedure to prepare the initial sample (using iron salts and paper as the cellulose source). Using in situ TEM, we were able to observe the formation of nanoparticles of iron carbide (Fe3C) and then the etching of these particles through the carbon. Iron carbide is well known to catalyze the formation of carbon nanotubes in standard techniques like chemical vapour deposition, but it’s remarkable that the particles are able to move through a solid amorphous carbon matrix in the way we observed.