@article{GumpertEitelKottasetal.2025, author = {Gumpert, Fabian and Eitel, Dominik and Kottas, Olaf and Helbig, Uta and Lohbreier, Jan}, title = {Multiscale simulations of three-dimensional nanotube networks: Enhanced modeling using unit cells}, series = {Computational Materials Science}, volume = {254}, journal = {Computational Materials Science}, publisher = {Elsevier BV}, issn = {0927-0256}, doi = {10.1016/j.commatsci.2025.113891}, year = {2025}, abstract = {This study presents a simulation approach for three-dimensional nanotube networks using cubic and tetragonal unit cells to enhance modeling efficiency. A random-walk algorithm was developed to generate these networks, which were analyzed using a Finite Element Method (FEM) simulation to assess their electrical conductivity. The percolation probability as a function of the nanotube filling factor can be derived from these simulation results. Smaller tetragonal unit cells can replicate the behavior of larger networks with significantly reduced computational effort, achieving up to a 20-fold reduction in computation time while obtaining similar results. In this work, the focus is on carbon-doped titanate nanotubes for hydrogen applications, but the method is adaptable to other applications with similar nanotube network composites. The findings are expected to provide a universal framework for the investigation of nanotube-based materials.}, language = {en} } @article{EitelAumuellerGleissetal.2025, author = {Eitel, Dominik and Aum{\"u}ller, Jessica and Gleiß, Julia and Blum, Michaela and Hagemann, Ulrich and Kottas, Olaf and Panzer, Sabrina and Helbig, Jens and Helbig, Uta and Teipel, Ulrich}, title = {Insight into the formation of carbon-doped titanate nanotubes}, series = {Chemical Engineering Journal Advances}, volume = {24}, journal = {Chemical Engineering Journal Advances}, publisher = {Elsevier BV}, issn = {2666-8211}, doi = {10.1016/j.ceja.2025.100898}, year = {2025}, abstract = {The formation of carbon-doped titanate nanotubes has been studied by using a simplified synthesis approach and extracting samples at different stages during the formation. The hydrothermal synthesis was conducted in a rotary evaporator with a PFA flask under ambient conditions. The resulting samples have been analyzed regarding their morphology, structure and surface area using X-ray diffraction, scanning electron microscopy and gas adsorption measurements. The results show the formation of high surface area nanosheets after a synthesis time as short as 2 h. Even though the surface area at this stage has already reached 212 m2/g, a change in morphology to elongated structures is not observed until 4 h of synthesis, suggesting the formation of the nanotubes during this phase. From that moment on, the d100 value, corresponding to the layer spacing between the nanotube layers, is further decreasing. Additionally, the formation of bundles with longer synthesis times was observed. This effect is discussed to be caused by a self-assembly process of nanotubes assisted by the continuous rotation of the flask in the rotary evaporator. The analysis of the final sample after 24 h revealed remaining carbon shells from the precursor powder. The presence of Ti-O-C bonds observed by X-ray photoelectron spectroscopy proved the incorporation of carbon in the nanotube structure.}, language = {en} }