Forschungsrichtungen

4.10.2021
Spraycoating of Silicon Nanoparticles as Anode Material in Solid State Batteries 

The reasearch in our group about solid state batteries is carried out as part of the "OptiKeraLyt" project (material and process optimization for lithium-ion batteries with ceramic solid state electrolytes). Within our subproject, one of the issues is the connection between anode and solid state electrolyte. In particular we are investigating the spraycoating of planar and surface structured solid state electrolytes with silicon nanoparticle dispersions. Important parameters are the coating homogeneity and the achievable coating thicknesses and porosities.  

Possible topics for Master/Bachelor theses and projects: 

  • Investigation of the silicon nanoparticle layer formation during spraycoating -> experimental investigation and model development 
  • Investigations into the reduction of so-called coffee ring structures (accumulation of nanoparticles at the droplet edge) by suitable choice of dispersing media 
  • Analysis of sprayed layers by means of light-, electron- and confocal-microscopy   
  • Experiments on the planarization of sprayed nanoparticle layers 

MA_Julian
left: Scanning electron microscopy image of a spray coted silicon nanoparticle layer, right: confocal microscopy image of single spray coated silicon nanoparticle droplets

Contact:  

M.Sc. Julian Neises 

Email: 

julian.neises@uni-due.de 

 

4.10.2021
Additively manufactured ceramic parts 

 The novel LCM method (lithography-based ceramic manufacturing) can be used to additively manufacture ceramics such as alumina and zirconia. In this process, suspension thin films with a ceramic nanoparticle content of 40-65% are selectively crosslinked step by step using the DLP (Digital Light Processing) principle to form a 3D workpiece. In the subsequent step, a heat treatment is mandatory to burn out the crosslinked polymer and trigger a sintering process. The materials produced in this way are investigated in terms of their structural and electromagnetic properties. 

Possible topics for Master/Bachelor theses and projects: 

  • Influence of printing and sintering parameters on microstructure and surface quality 
  • Investigation of printed and sintered structures using light, electron and confocal microscopy, profilometer measurements and determination of density/porosity 
  • Structured surface modification by laser-induced metallization 
  • Simulation and measurement of the electromagnetic properties of additively manufactured structures    


MA_Kai3
left: Setup of the 3D printer, middle: scanning electron microscope image of sintered alumina, right: examples of complicated structures that can be produced via LCM technique.


Contact:  

Dr. Masoud Sakaki 

Email:  

masoud.sakaki@uni-due.de 

Contact:  

M.Sc. Kai-Daniel Jenkel  

Email:  

kai-daniel.jenkel@uni-due.de  

 

4.10.2021
Lithium-Ion Battery Anodes based on Silicon Nanoparticles and vertically aligned Carbon Nanotubes 

A new concept for silicon-based anodes with high rate capabilities is investigated. Vertically-aligned carbon nanotubes (CNT-forests/VACNTs) grown via chemical vapor deposition act as electrically conductive scaffolding with the aim to expand the two-dimensional surface of Cu current collectors. Silicon nanoparticles (Si-NP) integrated into this CNT-structure are used as active material due to their high Li storage capability and their high tolerance against pulverization. Compared to conventional anodes, this concept offers a higher proportion of active material in direct electrical contact with the current collector and hence, possibly better performance at higher current densities. Figure 1 b) illustrates the basic anode concept. As grown VACNTs are densely packed and therefore, leave no space for a coating with Si-NPs beyond the topmost surface (Fig. 1 a) & c)). In order to be able to benefit from the CNT’s advantages, two methods for structuring VACNTs were developed: UV-Laser and solvent treatment. These process steps induce a “CNT-bunching” which yields a compacted structure with gaps that can be used for the infiltration of Si-NPs (Fig. 1 b) & d)). Si-NP deposition is achieved via doctor blading, spray coating and dip coating 

Master/Bachelor theses and projects typically include the following fields of work: 

  • Anode manufacturing via doctor blading, spray coating and dip coating. 
  • SEM analysis of samples. 
  • Assembly of electrochemical test cells/batteries. 
  • Electrochemical measurements, such as galvanostatic/potentiostatic cycling, electrochemical impedance spectroscopy, cyclic voltammetry. 

MA_Damian
Schematic illustration of our anode concept. Silicon nanoparticles (Si-NP) are deposited on top of an electrically conductive scaffold of vertically aligned carbon nanotubes (VACNTs). a) as grown VACNTs leave no space for Si-NP infiltration; b) structured VACNTs provide side walls that can be covered with Si-NP. Top view SEM image of a VACNT layer: c) untreated; d) after ethanol spray treatment. SEM image of a VACNT layer after slurry deposition via dip coating: e) top view, f) cross-sectional view, the voids between CNT-bunches are now completely fill with anode active material (Si-NP)

Contact:  

M.Sc. Damian Pandel 

Email: 

damian.pandel@uni-due.de 

 

4.10.2021
Inkjet-printed Silicon Schottky diodes 

By dispersing silicon nanoparticles in suitable organic solvents, Silicon is made printable. Inkjet printing enables the deposition of single droplets in the picoliter range, that can subsequently be functionalized by laser treatment and be utilized to produce Schottky diodes. By developing specialized Silicon inks and thereby controlling the drying behaviour, fine patterning of the deposited nanoparticles - even below the native resolution of inkjet printing - can be achieved. 

Possible topics for Master/Bachelor theses and projects: 

  • Inkjet-printing of dispersed Silicon nanoparticles, foto resist and metal inks 
  • Development of Silicon inks for optimisation of nanoparticle deposition profiles 
  • Investigation of printed nanoparticle structures by light, electron and confocal microscopy; profilometer measurements and UV excimer laser treatment 
  • Fabrication of Schottky diodes and electrical characterisation thereof by measurements of IV characterstics and high frequency operation 

MA_Fabian
Left: Threedimension confocal image of an inkjet-printed Silicon nanoparticle structure. Right: Scanning electron microscope image of the nanoparticles after structuring by laser treatment

Contact:  

M.Sc. Fabian Langer 

Email: 

fabian.langer@uni-due.de 

 

4.10.2021
Fabrication, characterization and optimization of Silicon µ-cone Schottky diodes 

The laser treatment of a Si nanoparticle thin film results in a self-organized cone-shaped μ-structure (µ-cones), which is highly crystalline. Sandwiched between two metal layers, whereby one is forming a Schottky contact to the Si µ-cones, Schottky diodes with switching speeds in the GHz-range can be realized. Due to the lateral discontinuity of the μ-cones, as well as their small footprint, this structure is expected to be mechanically flexible. 

In this context, the following topics are of interest for future graduate work:  

  • The realization of µ-cone Schottky diodes on flexible substrates such as paper or foils 

To demonstrate the flexibility of the µ-cone Schottky diodes, the transfer of the diode structure to flexible substrates is needed.  

  • The reduction of losses due to parasitic current paths by integrating a printing process for Si-NP deposition 

So far, the diode functionality of the µ-cone Schottky diodes could be demonstrated up to 4GHz, although this measurement is limited due to relatively high losses. The aim is therefore to reduce these losses, for example by reducing parasitic current paths by integrating a printing process for the Si-NP deposition.  

MA_Laura
left: Scanning electron microscope (SEM) image of self-organized cone shaped Si structure caused by the laser treatment of a silicon nanoparticle thin film (top view); right: schematic image of the diode structure (side view)

Contact: 

M.Sc. Laura Kühnel 

Email: 

laura.kuehnel@uni-due.de 

 

 

Further topics, please contact: Andreas Trampe


However, you can also address all scientific staff in the NST department to specific questions that are of particular interest to you.