Ingenieurwissenschaften
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- ItemHybrid-Aerogele als biomemetische 3D-Gerüststrukturen für regenerative Knochenkrebstherapie(Hannover : Technische Informationsbibliothek, 2025) Maleki, HajarThe treatment of malignant bone tumors and the restoration of bone damage following tumor resection remain significant clinical challenges. Addressing tumor-induced bone damage typically requires the implantation of biomimetic porous 3D materials with dual functionality: the local treatment of residual tumor cells and the subsequent restoration of bone tissue. There is an urgent need to develop dual-functional scaffold materials that fulfill the stringent requirements for both biological and tumor-therapeutic efficacy. Aerogels have emerged as promising biomaterials for targeted bone tissue regeneration due to their exceptional physical and microstructural properties, particularly their extensive po- rosity, pore interconnectivity, and high internal surface area. The primary objective of this project is to develop novel multi-functional 3D-printed composite aerogels as scaffold materials for bone tumor management. These aerogels are designed using surface-modified silk fibroin (SF) combined with functional nanoparticles to achieve dual functionality: high photothermal conversion for tumor ablation and osteogenic properties for bone regeneration. The design leverages surface modification, self-assembly, and ad- vanced 3D printing techniques. The unique self-assembly properties of surface-modified SF in solution, coupled with its hybridization with anisotropic nanomaterials (e.g., electrospun silica nanofibers, photothermally active nanoparticles/ agents such 2D nanosheets), enable the production of range of multifunctional composite aerogel scaffolds with interconnected and hierarchical porosity and biodegradability. Furthermore, the most promising materials undergo evaluation for their in vitro therapeutic efficacy and bone regeneration capabilities. By integrating 3D printing with innovative material concepts (e.g., composite aerogels), this project aims to address the critical clinical challenges of bone healing.
- ItemDFG-Abschlussbericht: Analyse eines neuen Verfahrens zum kontinuierlichen Strangpressen unter Anwendung der Ähnlichkeitstheorie(Hannover : Technische Informationsbibliothek, 2025-04-30) Gebhard, Johannes; Tekkaya, A. ErmanDas kontinuierliche Strangpressen ist die Kombination aus direktem und indirektem Strang- pressen mit einem stationären oder beweglichen Ventil. Dabei wird der Werkstoff von dem ersten Rezipienten mit einem direkten Stempel durch das Ventil in einen zweiten Rezipienten gepresst. Aus dem zweiten Rezipienten kann der Werkstoff mit einem Hohlstempel mit Press- werkzeug indirekte gepresst werden. Das Ventil lässt den Stofffluss nur in Pressrichtung zu, wodurch der Werkstoff aus dem zweiten Rezipient indirekt zum profilgepresst werden kann, während der nächste Pressblock in dem ersten Rezipienten eingelegt wird. Dabei kann die Austrittsgeschwindigkeit über den gesamten Zyklus konstant gehalten werden und der übliche Stillstand beim Block-auf-Block pressen wird vermieden. Da derzeitig keine Anlage zum kon- tinuierlichen Strangpressen existiert, wurde das Verfahren mit physikalischen Modellversu- chen, Ersatzversuchen mit Aluminium und numerisch untersucht. Mit Ersatzversuchen mit Alu- minium konnte die Funktionalität des stationären Ventils nachgewiesen werden. Da in dem Ersatzversuch Stempel und Hohlstempel nicht unabhängig voneinander bewegt werden kön- nen, wurde ein Modell einer kontinuierlichen Strangpresse mit Plastilin als Modellwerkstoff entwickelt, bei dem Stempel und Hohlstempel unabhängig voneinander bewegt werden kön- nen. Mithilfe der Modellversuche und numerischer Prozessvorhersage können für das konti- nuierliche Strangpressen mit beweglichem und stationärem Ventil Prozessfester aufgestellt werden. Selbst für schwer pressbare Legierungen (hier EN AW-7075) kann mit beiden Vari- anten ein kontinuierlicher Profilaustritt ermöglicht werden ohne die Solidustemperatur zu errei- chen oder die zulässige Stempellast zu überschreiten. Mit numerischen und analytischen Me- thoden konnte gezeigt werden, dass die Verschweißung der Querpressnaht deutlich verbes- sert werden kann.
- ItemDevelopment of Photocatalytically Active Anodized Layers by a Modified Phosphoric Acid Anodizing Process for Air Purification(Basel : MDPI, 2023) Lederer, Stephan; Benfer, Sigrid; Bloh, Jonathan; Javed, Rezan; Pashkova, Aneta; Fuerbeth, WolframOne of the key urban air quality issues is pollution by nitrogen oxides (NOx). To reduce NOx, facade cladding could be provided with photocatalytic properties by incorporating titanium dioxide nanoparticles. For this purpose, a modified phosphoric acid anodizing process (MPAA) was developed for the facade alloy EN AW-5005, in which highly ordered anodized structures with a low degree of arborization and tortuosity were produced. Pore widths between 70 nm and 150 nm and layer thicknesses of about 2–3 μm were obtained. The subsequent impregnation was carried out by dip coating from water-based systems. Depending on the dip-coating parameters and the suspension used, the pores can be filled up to 60% with the TiO2 nanoparticles. Photocatalytic tests according to ISO 22197-1 certify a high photocatalytic activity was obtained with rPCE values > 8 and with rPCE > 2, achieving “photocatalytically active for air purification”. Tests on the corrosion resistance of the anodized coatings with a commercially available aluminum and facade cleaner confirm a protective effect of the anodized coatings when compared with nonanodized aluminum material, as well as with compacted anodized layers.
- ItemPlasma Electrolytic Oxidation on Magnesium AZ31 with Sepiolite as Inhibitor Carrier for Improved Corrosion Protection(Basel : MDPI, 2023) Sottor, Robert; Gruen, Ricarda; Kremmer, Kerstin; Lederer, Stephan; Schneider, Michael; Fuerbeth, WolframPlasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte containing nanosized sepiolite fibers was carried out on magnesium alloy AZ31. The mineral fibers were loaded with different corrosion inhibitors and incorporated in situ during the PEO treatment. The composition and microstructure of the PEO coatings were investigated by SEM. It was shown that the fibers are located on the surface as well as inside the “weak spots” of the coating, i.e., pores and discharge channels. The fixation of the particles is caused by sintering due to the heat developed during the PEO treatment. Investigations using electrochemical impedance spectroscopy and linear sweep voltammetry in 0.01 M NaCl solution confirmed an improvement of the corrosion protection. The use of the inhibitors shifts the critical pitting potential in the anodic direction. Regarding efficiency, cerium-loaded sepiolite showed the best behavior by shifting the pitting potential by +0.9 V.
- ItemMechanisms of Secondary Spreading and Micro Droplet Formation on Steel(Bristol : IOP Publishing, 2024-12) Seeger, Lea; Lobnig, Renate; Schuch, Elmar; Guo, Surong; Fürbeth, WolframA new theory for secondary spreading based on the wetting theory of thin films is presented. It explains how micro droplets within the spreading zone and the primary droplet retain their shape, although connected by a thin electrolyte film and how humidity and salt concentration affect the growth rate of micro droplets. The trigger for secondary spreading, polarization or alkalization, is identified by using droplets of sodium hydroxide solution. Secondary spreading thus occurs on steel from pH 13.5 without corrosion or external polarization. The limiting pH value found explains why secondary spreading on steel only occurs when certain salts are used. The effect of the substrate is investigated by changing the microstructure of the steel. By comparing the sizes of micro droplets and micro structural phases and by scanning electron microscopy/energy-dispersive X-ray analysis measurements of the spreading zone, the existence of an electrolyte film connecting the micro droplets is supported. Ecorr potential profiles of secondary spreading droplets of sodium chloride solution on steel acquired by means of SKP are used to assess the contribution of secondary spreading to the total corrosion current, which is estimated to be low compared to that of the cathodic zone at the edge of the droplet.