UCL Department of Chemical Engineering


Bernhard Tjaden

Bernhard received his BSc in renewable energy systems from Technikum Wien in Vienna in 2008. He spent one semester in France at the Polytech Annecy-Chambéry. He then obtained a double MSc degree from KTH and Aalto university in sustainable energy systems in 2013. After that, he directly started his PhD at UCL.

Research project

Title: Microstructure analysis of oxygen transport membrane porous support and correlation with mass transport properties

Microstructural parameters play an important role in characterising, comparing and evaluating porous materials. Among such parameters, tortuosity, porosity and average pore size diameter are crucial for describing gaseous diffusion mechanisms in electrochemical devices. However, unlike the latter two parameters, tortuosity cannot be measured directly which is why different methods have been developed to determine the tortuosity of porous samples. These methods differ considerably from each other in terms of calculation approach and applied data sets.

In my project, I utilise advanced tomography techniques, simulation and diffusion cell experiments to calculate tortuosity of a porous support layer of an oxygen transport membrane. Then, the results are compared the suitability of these different approaches in estimating diffusive mass transport of gases through porous membranes is evaluated.

So far, a Wicke Kallenbach type diffusion cell is used for planar support samples and the diffusive fluxes of a selection of binary gas mixtures across the membrane are measured by means of gas chromatography. Tortuosity is then extracted by applying equimolar and equimass diffusion models. In addition, tomography and simulation have been carried out across X ray nano computed tomography and FIB SEM tomography sample reconstructions: for image quantification a fast marching computation technique using MATLab is applied while the simulation in StarCCM+ models the effective transport parameters of the porous phase.


MSc in Sustainable Energy Systems, KTH, 2013
BSc in Renewable Energy Systems, Technikum Wien, 2011