A Focus on our PhD Students – Mohammed Mostafa Adnan

Although my academic degree states that I have completed the Chemical Engineering and Biotechnology program at the Norwegian University of Science and Technology (NTNU), I’m more of a materials scientist at heart with a keen interest in functional materials. It is therefore of no surprise that my PhD involves the synthesis and characterisation of hybrid materials, specifically for use in high voltage insulation applications.

My first forays into scientific research involved summer internships during my undergraduate program at NTNU. In these internships, while we ended up finding some useful properties and characteristics of different materials, we did not have the time to answer the ‘whys’ that popped up during the studies. I realized quickly that I would need to be at a place which would foster my curiosity and provide me the freedom to pursue the questions that interested me, and I found this at the Functional Materials and Materials Chemistry (FACET) group at NTNU.

My master’s thesis was on the preparation of asymmetric oxygen permeable membranes with Ti-doped yttrium manganite, which was synthesized by a modified Pechini method – this gave me my first exposure to the sol-gel technique in practice. I then commenced my PhD in 2017 under the supervision of Professor Mari-Ann Einarsrud.

The primary goal in this PhD is to improve the dielectric properties of epoxy, which is used as high voltage insulation in various applications (e.g. transformers, printed circuit boards, rotating machines, etc.). This may be achieved by incorporating inorganic oxide (SiO2 , TiO2 , Al2O3 ) nanoparticles into epoxy using an in-situ route, where the particles are synthesised directly in the epoxy via a sol-gel process with the use of silane coupling agents. The use of nanoparticles (as opposed to micron-sized particles) has been found to be beneficial not only to the mechanical and thermal properties of the epoxy, but possibly to the dielectric properties as well – this is suspected to be due to the increased interfacial area between the inorganic and organic components, which means that the state of dispersion of the nanoparticles is a critical factor. The use of this in-situ sol-gel route instead of a traditional ex-situ physical mixing process in our work has been found to be more successful in creating nanocomposites with well dispersed nanoparticles with interesting morphological features. The SiO2 forms hierarchical clusters exhibiting mass and surface fractal features, while traditionally prepared composites with pre -synthesised nanoparticles often form large agglomerates. The use of the silane coupling agents ensured that Class II hybrid materials were formed, with a direct chemical link at the interfaces between the organic and inorganic components. This work was presented at the XX International Sol-Gel Conference in St Petersburg, where I had the honour of being awarded one of the best poster prizes. In more recent developments, the epoxy-SiO2 nanocomposites were also observed to reduce the growth rate of “electrical trees” (see optical micrograph), indicating an improved resistance to pre-dielectric breakdown phenomenon. Morphological differences were also observed in the TiO2 and Al2O3 nanocomposites, with TiO2 forming more discrete particles and Al2O3 forming similar but larger hierarchical clusters than the SiO2 . The next step will be to investigate how the differences in morphology affect the mechanical and dielectric properties of the nanocomposites, and to elucidate the structure-property relations in these hybrid materials.

One of the main reasons my PhD project has fascinated me is the intermingling of several different fields – the use of both inorganic and organic chemistry to prepare materials for use in electrical engineering demonstrates the multidisciplinary nature of research today, which always brings up new questions to ask and new possibilities to pursue. It has also introduced me to the world of hybrid materials, and I believe that there is tremendous potential for these functional hybrid materials in a myriad of other applications.