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 Modelling and experimental validation of the flame temperature profile in atmospheric plasma coating processes on the substrate(2024) Martínez-García, Jose; Martínez-García, Venancio; Killinger, AndreasThis work presents a characterisation model for the temperature distribution at different substrate depths during the atmospheric plasma spray (APS) coating process. The torch heat flow in this model is simulated as forced convection defined by a surface, a temperature profile, and a convection coefficient. The simulation model considers three plasma temperature profiles of the Al2O3 coating on a 5 mm thickness flat aluminium substrate. The simple and low-cost experimental procedure, based on a thermocouple, measures the plasma plume temperature distribution of the APS coating system, and their results are used to obtain the parameter values of each of the three proposed plasma temperature profiles. The experimental method for in situ non-contact temperature measurements inside the substrate is based on an infrared pyrometry technique and validates the simulation results. The Gaussian temperature profile shows excellent accuracy with the measured temperatures. The Gaussian approach could be a powerful tool for predicting residual stress through a coupled one-way thermal-mechanical analysis of the APS process.Item Open Access Thin GB14 coatings on implants using HVSFS(2024) Lanzino, Maria Carolina; Le, Long-Quan R. V.; Wilbig, Janka; Rheinheimer, Wolfgang; Seidenstuecker, Michael; Günster, Jens; Killinger, AndreasEnhancing osseointegration, the process by which medical implants securely bond to bone, is crucial for improving patient outcomes in orthopedics and dental surgery. Calcium alkali orthophosphates, with their superior bioactivity, resorbability, and chemical resemblance to bone minerals, have emerged as promising candidates for implant coatings. These materials offer improved solubility and lower melting points due to the substitution of calcium with potassium and sodium, along with the addition of magnesium oxide. This study investigates GB14 calcium alkali orthophosphate coatings applied via High Velocity Suspension Flame Spraying (HVSFS), a technique that enables precise control over coating properties. A porosity target of >10% was set to promote bone growth, and we achieved porosities up to 13%, ensuring better cell penetration and stability at the implant-bone interface. Coatings were produced using different gas parameters and distances, with their microstructure and phase composition analyzed using scanning electron microscope (SEM), Vickers hardness testing and X-ray diffraction (XRD). Additionally, roughness and porosity were also assessed. Different coating’s microstructures were achieved by varying stand-off distance and gas parameters. Increasing stand-off distance while reducing gas stoichiometry enabled the production of calcium alkali orthophosphate coatings with fewer cracks, higher porosity and a hardness level comparable to that of state-of-the-art tricalcium phosphate (TCP) coatings. The sample with optimized properties in terms of achieved microstructure and topography was selected for in vitro testing using MG63 osteosarcoma cells to evaluate cell proliferation and adhesion. WST (I) assay, LDH assay, and live/dead staining confirmed the biocompatibility of the coatings, highlighting the potential of HVSFS to enhance osseointegration and outperform conventional methods in implantology. No relevant cytotoxicity could be shown and cells show a good proliferation over time. These results highlight thus the potential of HVSFS to produce thin, bioactive and resorbable coatings to enhance osseointegration.Item Open Access Suspension-sprayed calcium phosphate coatings with antibacterial properties(2024) Lanzino, Maria Carolina; Le, Long-Quan R. V.; Höppel, Anika; Killinger, Andreas; Rheinheimer, Wolfgang; Dembski, Sofia; Al-Ahmad, Ali; Mayr, Hermann O.; Seidenstuecker, MichaelProsthesis loosening due to lack of osteointegration between an implant and surrounding bone tissue is one of the most common causes of implant failure. Further, bacterial contamination and biofilm formation onto implants represent a serious complication after surgery. The enhancement of osteointegration can be achieved by using bioconductive materials that promote biological responses in the body, stimulating bone growth and thus bonding to tissue. Through the incorporation of antibacterial substances in bioconductive, biodegradable calcium phosphate (CaP) coatings, faster osteointegration and bactericidal properties can be achieved. In this study, Cu-doped CaP supraparticles are spray-dried and suspension-sprayed CaP ceramic coatings with antibacterial properties are prepared using high-velocity suspension flame spraying (HVSFS). The objective was to increase the coatings’ porosity and investigate which Cu-doped supraparticles have the strongest antibacterial properties when introduced into the coating layers. Biocompatibility was tested on human Osteosarcoma cells MG63. A porosity of at least 13% was achieved and the supraparticles could be implemented, enhancing it up to 16%. The results showed that the addition of Cu-doped supraparticles did not significantly reduce the number of viable cells compared to the Cu-free sample, demonstrating good biocompatibility. The antimicrobial activity was assessed against the bacterial strains Escherichia coli and Staphylococcus aureus , with Safe Airborne Antibacterial testing showing a significant reduction in both Gram-positive and Gram-negative strains on the Cu-doped coatings.Item Open Access Metallization of carbon fiber-reinforced plastics (CFRP) : influence of plasma pretreatment on mechanical properties and splat formation of atmospheric plasma-sprayed aluminum coatings(2024) Semmler, Christian; Schwan, Willi; Killinger, AndreasCarbon fiber-reinforced plastics (CFRPs) have broad applications as lightweight structural materials due to their remarkable strength-to-weight ratio. Aluminum is often used as a bond coating to ensure adhesion between CFRPs and further coatings with a higher melting temperature. However, challenges persist in optimizing their surface properties and adhesion attributes for diverse applications. This investigation explores the impact of sandblasting and plasma pretreatment on CFRP surfaces and their influence on plasma-sprayed aluminum coatings. Two distinct CFRP substrates, distinguished by their cyanate ester and epoxy resin matrices, and two different aluminum powder feedstocks were employed. Plasma pretreatment induced micro-surface roughening in the range of 0.5 µm and significantly reduced the contact angles on polished specimens. Notably, on sandblasted specimens, plasma-activated surfaces displayed improved wetting behavior, which is attributed to the removal of polymeric fragments and augmented fiber exposure. Aluminum splats show a better interaction with carbon fibers compared to a polymeric matrix material. The impact of plasma activation on the coating adhesion proved relatively limited. All samples with plasma activation had deposition efficiencies that increased by 12.5% to 34.4%. These findings were supported by SEM single-splat analysis and contribute to a deeper comprehension of surface modification strategies tailored to CFRPs.Item Open Access Copper-enriched hydroxyapatite coatings obtained by high-velocity suspension flame spraying : effect of various gas parameters on biocompatibility(2024) Le, Long-Quan R. V.; Lanzino, M. Carolina; Blum, Matthias; Höppel, Anika; Al-Ahmad, Ali; Killinger, Andreas; Gadow, Rainer; Rheinheimer, Wolfgang; Seidenstuecker, MichaelHydroxyapatite (HAp)-coated bone implants are frequently used for orthopaedic or dental implants since they offer high biocompatibility and osteoconductivity. Yet, problems such as infections, e.g. periprosthetic joint infections, occur when implanting foreign material into the body. In this study, HAp coatings were produced via high-velocity suspension flame spraying (HVSFS). This method allows for the production of thin coatings. We investigated the effects of different gas parameters on the coating properties and on the biocompatibility, which was tested on the human osteosarcoma cell line MG63. Furthermore, Copper (Cu) was added to achieve antibacterial properties which were evaluated against standard microorganisms using the airborne assay. Three gas parameter groups (low, medium, and high) with different Cu additions (0 wt.%, 1 wt.% and 1.5 wt.%) were evaluated. Our findings show that porosity as well as hardness can be controlled through gas parameters. Furthermore, we showed that it is possible to add Cu through external injection. The Cu content in the coating as well as the release varies with different gas parameters. Both antibacterial efficacy as well as biocompatibility are affected by the Cu content. We could significantly reduce the amount of colony-forming units (CFU) in all coatings for E. coli , CFU for S. aureus was reduced by adding 1.5 wt.% of Cu to the coating. The biocompatibility testing showed a cytotoxicity threshold at a Cu-release of 14.3 mg/L in 120 hours. Based on our findings, we suggest medium gas parameters for HVSFS and the addition of 1 wt.% Cu to the coating. With these parameters, a reasonable antibacterial effect can be achieved while maintaining sufficient biocompatibility.