Career

Supervisor: Dennis Arigbe

Research field: Nanoporous Material

Work type: Experimental

Available for: HiWi, Bachelor Thesis, Master Thesis

Start date: Flexible

Project brief:

For optimizing the supercritical drying of aerogels, it is crucial to understand the drying kinetics, especially on a larger scale. A new large-scale plant is installed in the technical hall to measure this. One important property that needs to be monitored therefore is the development of the CO2/solvent mixture composition throughout the entire drying process at various measuring points. Raman spectroscopy is used as the analysis tool, because it has several advantages, like a low measure volume. 

To get reliable composition results, a very important step is to calibrate the measuring setup properly. For the parameters like pressure, temperature and mixture composition in the expected regions, different measuring points need to be evaluated and measured. After postprocessing of the arising data, the calibration results need to be regressed with a suitable model.

Objectives:

• Measuring the Raman signals at different Parameters
• Postprocessing of the data
• Regression of the experimental data
• Validation of the regression model

Supervisor: Lara Gibowsky

Research field: Nanoporous Material

Work type: Experimental

Available for: Master Thesis

Start date: Flexible

Project brief:

(Biopolymer-based) aerogels are lightweight solid materials, which are particularly suitable for applications as insulation material but also in the food and pharmaceutical industries due to their low density, high porosity and specific surface area. They have a very fine, air-filled pore structure, the properties of which are decisive for their subsequent use. 

Despite the high relevance, the manufacturing process, which consists of the three steps gelation, solvent exchange and supercritical drying, still represents a cost and time challenge for the application in the industry. In order to be able to implement larger aerogel quantities in production, this often takes place in packed beds. However, this causes the disadvantage of mechanical stress on the gel particles due to their own weight as well as external forces such as pressure loss across the packed bed. In extreme cases, this stress can lead to plastic deformation of the gel particles, resulting in irreversible damage to the microstructure, loss of the characteristic properties and increased pressure drops across the packed bed. 

The correlation between the process parameters of the solvent exchange and the mechanical and microstructural properties of the gel particles has not yet been clarified.

Objectives:

• Investigation of solvent exchange and supercritical drying in packed bed systems
• Investigation of the influence of process parameters (solvent concentration, flow rate, etc.) on deformation mechanisms of soft gels in packed beds
• Production and screening of different gel systems (various biopolymers and particle sizes)
• Analyzing the microstructure and deformation of the final aerogels
• Analyzing the correlations to identify the critical states in the manufacturing process

Supervisor: Alberto Bueno (aerogel-it)

Research field: Nanoporous Material

Work type: Experimental and Theoretical

Available for: Master Thesis

Start date: Flexible

Project brief:

In order to produce nanoporous solid materials such as aerogels it is required to dry a wet gel without disrupting the porous structure of it. Different drying techniques such as freeze drying have been developed in order to preserve the nanoporous structure. Supercritical CO₂ (scCO₂) drying has been proven to be a universal drying technique and gives the best results to produce aerogels. The misconception that scCO₂ drying is an expensive and time-consuming technique has limited this technique to just the lab scale.

Recently, it has been proven that scCO₂ drying is feasible at an industrial scale and can compete with standard drying techniques. To further attract industrial attention, better analytical tools which allow a better measurement of the drying kinetics are necessary. Measuring the scCO₂ drying kinetics has proven a challenge since the density and viscosity of the bulk fluid are changing constantly during the process.

In order to determine the real drying kinetics from the experimental data, it is required to develop mathematical algorithms which correlate the system flow dynamics with the data obtained during the drying experiments. The corrected data obtained can be applied in mathematical models in order to optimize the whole process.

Objectives:

• Non-steady state residence time distributions are to be determined and fitted to RTD models.
• A deconvolution algorithm is used to recover the real kinetics which are going to be used to evaluate a mathematical model describing the process.
• Determination of RTD distribution at different conditions of temperature, pressure and CO₂/solvent compositions.
• Effect of the internal geometry of the autoclave in the drying kinetics.
• Development of a deconvolution algorithm in Python.
• Further development of a mathematical model which represents the process (Python).

Supervisor: Razan Altarabeen

Research field: Nanoporous Material

Work type: Experimental

Available for: Project Work

Start date: Flexible

Project brief:

One of the common approaches towards green energy is reduction of CO₂ emissions. Electricity and Heating of households generate high percentage of CO₂ and an amount of this heat is lost when conventional insulation materials are used.

Innovative insulation materials can reduce the required heating power by minimizing heat losses and thus reduce CO₂ emissions. One potential solution is the use of Aerogels which are highly porous lightweight materials (up to 99% air).

Lignin, the most second abundant carbon source which is found in the plant wall can be used as a bio-polyol to synthesize bio-based PU Aerogels. The aim of this project is to incorporate lignin in PU Hydrogels via sol gel process followed by supercritical CO₂ drying to obtain lignin-PU aerogels.

The methods used in this project include the sol-gel gelation process for hydrogel formation, supercritical CO₂ drying to preserve the porous structure, BET measurements for surface area analysis, SEM for morphological characterization, and thermal conductivity determination using the Hot Disk method.

Objectives:

• Solubility measurement of lignin in different solvent mixtures.
• Optimization of the aerogels density
• Evaluation of the crosslinking of lignin in the lignin-PU aerogels.
• Supercritical CO₂ drying of the aerogels
• Characterization of the lignin-aerogel in regard to their mechanical and thermal properties

Supervisor: Razan Altarabeen

Research field: Nanoporous Material

Work type: Experimental

Available for: Project Work

Start date: Flexible

Project brief:

Biopolymer aerogels, such as alginate aerogels, are nanoporous ultralight materials with high biocompatibility, which enables them to be tailored for various applications such as tissue engineering and drug delivery systems. One major challenge is their porous structure, which is prone to damage and collapse when subjected to moisture due to the surface’s hydrophilicity.

Coating can be used to prevent the penetration of moisture, thus reducing the shrinkage of aerogels. However, conventional coating strategies often involve synthetic chemicals and complex processes. Preliminary results showed lignin’s potential as a biopolymer additive for the coating of alginate aerogel particles.

In this project, the main focus is the investigation of the lignin-alginate interaction, the study of the gelation mechanism, and the analysis of the coating layer’s thickness and homogeneity.

The methods used include BET measurements for surface area analysis, SEM for morphological characterization, FTIR spectroscopy for structural analysis, and CamSizer for particle size distribution analysis.

Objectives:

• Lignin Alginate aerogel particles formation via dripping method.
• Evaluation of lignin’s influence on crosslinking and shrinkage behaviour of alginate particles.
• Drying of the hydrogel particles via supercritical CO2 drying.
• Characterization of the lignin coating layer and surface characteristics