07 Fakultät Konstruktions-, Produktions- und Fahrzeugtechnik
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/8
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Item Open Access Alumina and zirconia-reinforced polyamide PA-12 composites for biomedical additive manufacturing(2021) Nakonieczny, Damian S.; Kern, Frank; Dufner, Lukas; Antonowicz, Magdalena; Matus, KrzysztofThis work aimed to prepare a composite with a polyamide (PA) matrix and surface-modified ZrO2 or Al2O3 to be used as ceramic fillers (CFs). Those composites contained 30 wt.% ceramic powder to 70 wt.% polymer. Possible applications for this type of composite include bioengineering applications especially in the fields of dental prosthetics and orthopaedics. The ceramic fillers were subjected to chemical surface modification with Piranha Solution and suspension in 10 M sodium hydroxide and Si3N4 to achieve the highest possible surface development and to introduce additional functional groups. This was to improve the bonding between the CFs and the polymer matrix. Both CFs were examined for particle size distribution (PSD), functional groups (FTIR), chemical composition (XPS), phase composition (XRD), and morphology and chemical composition (SEM/EDS). Filaments were created from the powders prepared in this way and were then used for 3D FDM printing. Samples were subjected to mechanical tests (tensility, hardness) and soaking tests in a high-pressure autoclave in artificial saliva for 14, 21, and 29 days.Item Open Access PA-12-zirconia-alumina-cenospheres 3D printed composites : accelerated ageing and role of the sterilisation process for physicochemical properties(2022) Nakonieczny, Damian S.; Antonowicz, Magdalena; SimhaMartynkova, Gražyna; Kern, Frank; Pazourková, Lenka; Erfurt, Karol; Hüpsch, MichałThe aim of this study was to conduct artificial ageing tests on polymer-ceramic composites prepared from polyamide PA-12 polymer matrix for medical applications and three different variants of ceramic fillers: zirconia, alumina and cenospheres. Before ageing, the samples were subjected to ethyl oxide sterilization. The composite variants were prepared for 3D printing using the fused deposition modeling method. The control group consisted of unsterilized samples. Samples were subjected to artificial ageing in a high-pressure autoclave. Ageing conditions were calculated from the modified Hammerlich Arrhenius kinetic equation. Ageing was carried out in artificial saliva. After ageing the composites were subjected to mechanical (tensile strength, hardness, surface roughness) testing, chemical and structural (MS, FTIR) analysis, electron microscopy observations (SEM/EDS) and absorbability measurements.Item Open Access Adjustment of micro- and macroporosity of ß-TCP scaffolds using solid-stabilized foams as bone replacement(2023) Dufner, Lukas; Oßwald, Bettina; Eberspaecher, Jan; Riedel, Bianca; Kling, Chiara; Kern, Frank; Seidenstuecker, MichaelTo enable rapid osteointegration in bioceramic implants and to give them osteoinductive properties, scaffolds with defined micro- and macroporosity are required. Pores or pore networks promote the integration of cells into the implant, facilitating the supply of nutrients and the removal of metabolic products. In this paper, scaffolds are created from ß-tricalciumphosphate (ß-TCP) and in a novel way, where both the micro- and macroporosity are adjusted simultaneously by the addition of pore-forming polymer particles. The particles used are 10-40 wt%, spherical polymer particles of polymethylmethacrylate (PMMA) (Ø = 5 m) and alternatively polymethylsilsesquioxane (PMSQ) (Ø = 2 m), added in the course of ß-TCP slurry preparation. The arrangement of hydrophobic polymer particles at the interface of air bubbles was incorporated during slurry preparation and foaming of the slurry. The foam structures remain after sintering and lead to the formation of macro-porosity in the scaffolds. Furthermore, decomposition of the polymer particles during thermal debindering results in the formation of an additional network of interconnecting micropores in the stabilizing structures. It is possible to adjust the porosity easily and quickly in a range of 1.2-140 m with a relatively low organic fraction. The structures thus prepared showed no cytotoxicity nor negative effects on the biocompatibility.Item Open Access Effect of simulated mastication on structural stability of prosthetic zirconia material after thermocycling aging(2023) Ziębowicz, Anna; Oßwald, Bettina; Kern, Frank; Schwan, WilliRecent trends to improve the aesthetic properties-tooth-like color and translucency-of ceramic dental crowns have led to the development of yttria-stabilized zirconia (Y-TZP) materials with higher stabilizer content. These 5Y-TZP materials contain more cubic or t’ phase, which boosts translucency. The tradeoff as a consequence of a less transformable tetragonal phase is a significant reduction of strength and toughness compared to the standard 3Y-TZP composition. This study aims at determining the durability of such 5Y-TZP crowns under lab conditions simulating the conditions in the oral cavity during mastication and consumption of different nutrients. The test included up to 10,000 thermal cycles from 5 °C to 55 °C “from ice cream to coffee” and a chewing simulation representing 5 years of use applying typical loads. The investigation of the stress-affected zone at the surface indicates only a very moderate phase transformation from tetragonal to monoclinic after different varieties of testing cycles. The surface showed no indication of crack formation after testing. It can, therefore, be assumed that over the simulated period, dental crowns of 5Y-TZP are not prone to fatigue failure.Item Open Access Deposition of 3YSZ-TiC PVD coatings with high-power impulse magnetron sputtering (HiPIMS)(2021) Gaedike, Bastian; Guth, Svenja; Kern, Frank; Killinger, Andreas; Gadow, RainerOptimized coating adhesion and strength are the advantages of high-power impulse magnetron sputtering (HiPIMS) as an innovative physical vapor deposition (PVD) process. When depositing electrically non-conductive oxide ceramics as coatings with HiPIMS without dual magnetron sputtering (DMS) or mid-frequency (MF) sputtering, the growing coating leads to increasing electrical insulation of the anode. As a consequence, short circuits occur, and the process breaks down. This phenomenon is also known as the disappearing anode effect. In this study, a new approach involving adding electrically conductive carbide ceramics was tried to prevent the electrical insulation of the anode and thereby guarantee process stability. Yttria-stabilized zirconia (3YSZ) with 30 vol.% titanium carbide (TiC) targets are used in a non-reactive HiPIMS process. The main focus of this study is a parameter inquisition. Different HiPIMS parameters and their impact on the measured current at the substrate table are analyzed. This study shows the successful use of electrically conductive carbide ceramics in a non-conductive oxide as the target material. In addition, we discuss the observed high table currents with a low inert gas mix, where the process was not expected to be stable.Item Open Access Effect of calcination temperature on the phase composition, morphology, and thermal properties of ZrO2 and Al2O3 modified with APTES (3-aminopropyltriethoxysilane)(2021) Nakonieczny, Damian S.; Kern, Frank; Dufner, Lukas; Dubiel, Agnieszka; Antonowicz, Magdalena; Matus, KrzysztofThis paper describes the effect of calcination temperature on the phase composition, chemical composition, and morphology of ZrO2 and Al2O3 powders modified with 3-aminopropyltriethoxysilane (APTES). Both ceramic powders were modified by etching in piranha solution, neutralization in ammonia water, reaction with APTES, ultrasonication, and finally calcination at 250, 350, or 450 °C. The obtained modified powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, particle size distribution (PSD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and thermogravimetric analysis (TGA).