TY - JOUR A1 - Hornberger, Helga A1 - Kissel, Hannah A1 - Striegl, Birgit A1 - Kronseder, Matthias A1 - Vollnhals, Florian A1 - Christiansen, Silke H. T1 - Bioactivity and corrosion behavior of magnesium barrier membranes JF - Materials and Corrosion N2 - In the current research, magnesium and its alloys have been intensively studied as resorbable implant materials. Magnesium materials combine their good mechanical properties with bioactivity, which make them interesting for guided bone regeneration and for the application as barrier membranes. In this study, the in vitro degradation behavior of thin magnesium films was investigated in cell medium and simulated body fluid. Three methods were applied to evaluate corrosion rates: measurements of (i) the gaseous volume evolved during immersion, (ii) volume change after immersion, and (iii) polarization curves. In this comparison, measurements of H2 development in Dulbecco's modified Eagle's medium showed to be the most appropriate method, exhibiting a corrosion rate of 0.5 mm·year−1. Observed oxide and carbon contamination have a high impact on controlled degradation, suggesting that surface treatment of thin foils is necessary. The bioactivity test showed positive results; more detailed tests in this area are of interest. Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-24499 N1 - Corresponding author: Helga Hornberger VL - 73 IS - 1 SP - 8 EP - 19 PB - Wiley ER - TY - JOUR A1 - Hornberger, Helga A1 - Witte, Frank A1 - Hort, Norbert A1 - Müller, Wolf-Dieter T1 - Effect of fetal calf serum on the corrosion behaviour of magnesium alloys JF - Materials Science and Engineering B N2 - The corrosion behaviour of WE43 magnesium alloys using the mini cell system was studied. Voltammetry and impedance spectroscopy were applied to study on the one hand the effect of microstructure of the working electrode and on the other hand the effect of proteins in the electrolyte. Two types of alloy samples were produced (i) by permanent mould casting and (ii) by gas atomization followed by extrusion. The results showed that the microstructure was strongly influenced by the production process. The extruded samples showed an improved homogeneity of phase distribution compared with cast samples as it was aimed for. Due to increased homogeneity it was expected to find higher corrosion resistance. However, the electrochemical results are contradictory and suggest an additional phase in the extruded microstructure. Using energy dispersive X-ray spectroscopy (EDX) the secondary magnesium rare earths (RE) phase of extruded samples showed differing composition than of cast samples as well as additional oxide phases. After the samples were electrochemically investigated in cell medium with and without fetal calf serum (FCS), an impact of FCS was detected in voltammetry due to the length of the polarisation curve. As the tip of the mini cell in contact with the working electrode is small, developing gases tend to spread on the working electrode and break the contact of liquid to the counter electrode; which results in disrupting the current flow. This effect was more pronounced when rising the voltage and was found reduced when using electrolytes with FCS. Impedance spectra were slightly deformed by FCS, seen as a kinetic effect but not as a basic differing corrosion reaction. The insight into the effects of FCS was provided by the mini cell system as this system enables to collect entire series of measurements. In contrast of two single measurements, those series reflected the slight difference caused by FCS. The focus of the electrochemical corrosion study was set on the first half hour of immersion. KW - Magnesium KW - Corrosion KW - Proteins KW - Impedance KW - Reproducibility KW - Polarization Y1 - 2011 U6 - https://doi.org/10.1016/j.mseb.2011.07.018 VL - 176 IS - 29 SP - 1746 EP - 1755 ER - TY - JOUR A1 - Manaranche, Claire A1 - Hornberger, Helga T1 - A proposal for the classification of dental alloys according to their resistance to corrosion JF - Dental Materials N2 - Objectives The purpose of this study was to establish a method to compare and classify dental alloys in relation to their resistance to corrosion. Methods Alloy samples and pure metal samples were prepared and tested in chemical and electrochemical corrosion according to ISO 10271. For electrochemical test, the rest potential versus time and a potentiodynamic scan were recorded. After chemical corrosion test, the ions released were analyzed by ICP (induced coupled plasma) spectroscopy. Results High gold alloys had a similar polarization curve than gold. The same effect was observed for Pd–base alloys, their curves were similar to the one of palladium. The ions released during chemical corrosion were non-precious metallic ions. Thereby Ni–Cr alloys were found to release the most ions. Au–Pt alloys showed the highest release of ions compared with other precious alloys but low compared with Ni–Cr. Electrochemical corrosion was more aggressive than chemical corrosion and every type of elements was etched, the higher the precious metal content, the higher the resistance to corrosion of the alloy. Discussion Using the recorded data, a classification system for electrochemical corrosion was developed and discussed to judge the results. Hereby were gold and zinc used as reference materials. The applied classification system defines five classes and it is proposed that alloys of class V are not acceptable. For chemical corrosion resistance, three classes were distinguished according to the quantity of metallic ions released and it is proposed that class III (100–1000 μg/cm2 week) is not acceptable. Palladium and Pd–base alloys showed a higher electrochemical and chemical corrosion resistance than gold. KW - Dental alloys KW - Precious alloys KW - Corrosion test KW - Resistance to corrosion KW - Classification KW - Ion release Y1 - 2007 U6 - https://doi.org/10.1016/j.dental.2006.11.030 VL - 23 IS - 11 SP - 1428 EP - 1437 ER - TY - JOUR A1 - Müller, Wolf-Dieter A1 - Hornberger, Helga T1 - The Influence of MgH2 on the Assessment of Electrochemical Data to Predict the Degradation Rate of Mg and Mg Alloys JF - International Journal of Molecular Science N2 - Mg and Mg alloys are becoming more and more of interest for several applications. In the case of biomaterial applications, a special interest exists due to the fact that a predictable degradation should be given. Various investigations were made to characterize and predict the corrosion behavior in vitro and in vivo. Mostly, the simple oxidation of Mg to Mg2+ ions connected with adequate hydrogen development is assumed, and the negative difference effect (NDE) is attributed to various mechanisms and electrochemical results. The aim of this paper is to compare the different views on the corrosion pathway of Mg or Mg alloys and to present a neglected pathway based on thermodynamic data as a guideline for possible reactions combined with experimental observations of a delay of visible hydrogen evolution during cyclic voltammetry. Various reaction pathways are considered and discussed to explain these results, like the stability of the Mg+ intermediate state, the stability of MgH2 and the role of hydrogen overpotential. Finally, the impact of MgH2 formation is shown as an appropriate base for the prediction of the degradation behavior and calculation of the corrosion rate of Mg and Mg alloys. KW - magnesium KW - magnesium alloys KW - magnesium hydride KW - corrosion Y1 - 2014 U6 - https://doi.org/10.3390/ijms150711456 VL - 15 SP - 11456 EP - 11472 ER - TY - JOUR A1 - Hornberger, Helga A1 - Virtanen, Sannakaisa A1 - Boccaccini, Aldo R. T1 - Biomedical coatings on magnesium alloys BT - a review JF - Acta Biomaterialia N2 - This review comprehensively covers research carried out in the field of degradable coatings on Mg and Mg alloys for biomedical applications. Several coating methods are discussed, which can be divided, based on the specific processing techniques used, into conversion and deposition coatings. The literature review revealed that in most cases coatings increase the corrosion resistance of Mg and Mg alloys. The critical factors determining coating performance, such as corrosion rate, surface chemistry, adhesion and coating morphology, are identified and discussed. The analysis of the literature showed that many studies have focused on calcium phosphate coatings produced either using conversion or deposition methods which were developed for orthopaedic applications. However, the control of phases and the formation of cracks still appear unsatisfactory. More research and development is needed in the case of biodegradable organic based coatings to generate reproducible and relevant data. In addition to biocompatibility, the mechanical properties of the coatings are also relevant, and the development of appropriate methods to study the corrosion process in detail and in the long term remains an important area of research. KW - Magnesium alloyn KW - Biodegradable materials KW - Coatings KW - Conversion KW - Deposition Y1 - 2012 U6 - https://doi.org/10.1016/j.actbio.2012.04.012 VL - 8 IS - 7 SP - 2442 EP - 2455 ER - TY - JOUR A1 - Hornberger, Helga A1 - Striegl, Birgit A1 - Trahanofsky, M. A1 - Kneissl, F. A1 - Kronseder, Matthias T1 - Degradation and bioactivity studies of Mg membranes for dental surgery JF - Materials Letter X N2 - Bioresorbable materials are under investigation due to their promising properties for applications as implant material. This study is about the degradation and bioactivity behaviour of magnesium foils, which allegorize dental membranes. The degradation behaviour including pitting corrosion during immersion tests can be precisely observed using micro-computed tomography. Using the bioactivity test according to Kokubo, it is shown that magnesium has strong Ca-phosphate layer formation correlated with high degradation. Therefore, magnesium foils appear to hold a great potential for bone implant application. KW - Magnesium KW - Dental membrane KW - Bioactivity KW - Corrosion rate Y1 - 2019 U6 - https://doi.org/10.1016/j.mlblux.2019.100007 VL - 2 IS - June SP - 1 EP - 5 PB - Elsevier ER - TY - JOUR A1 - Hornberger, Helga A1 - Marquis, Peter M. A1 - Christiansen, Silke H. A1 - Strunk, Horst P. T1 - Microstructure of a high strength alumina glass composite JF - Journal of Materials Research N2 - The morphology and microstructure of an Al2O3 glass composite (trade name In-Ceram, Vita Zahnfabrik) were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composite was produced by infiltration of a lanthanum-based glass throughout a porous Al2O3 body. This alumina body was formed by three classes of particles differing in size and shape: faceted particles typically ≤4 μm in diameter, platelets of average diameter 8 μm, 1.5 μm thickness, and small spheres 0.4 μm in diameter. The outstanding strength properties of the composite (600 MPa, ball-on-ring test) are a result of the high wetting capability of the glass phase on the Al2O3 surface. In addition, plastic strain relaxation in the faceted particles by dislocation formation compensates partially for residual stresses and impedes crack formation at the glass/Al2O3 interface. Y1 - 1996 U6 - https://doi.org/10.1557/JMR.1996.0104 VL - 11 IS - 4 SP - 855 EP - 858 ER - TY - PAT A1 - Hornberger, Helga A1 - Thiel, Norbert A1 - Vollmann, Markus T1 - Fully ceramic tooth replacement with a frame made of cer-stabilised zircon-oxide N2 - Vollkeramischer Zahnersatz mit einem Gerüst, das aus einem Gerüstmaterial aus einem Cer-stabilisierten Zirkonoxid (Ce-ZrO2) mit einem Anteil von bis zu 25 Gew% Aluminiumoxid (Al2O3) bezogen auf den Anteil an ZrO2 aufgebaut ist und einem Infiltrationsglasanteil im Gerüst von 0-40 Vol% bezogen auf das Volumen des Gerüsts sowie einer auf das Gerüstmaterial abgestimmten Verblendkeramik.Die Erfindung betrifft die Verwendung von cer-stabilisiertem ZrO2 zur Herstellung von Gerüstmaterialien, die als Restauration im Dentalbereich einsetzbar sind. T2 - Vollkeramischer Zahnersatz mit einem Gerüst aus einem cer-stabilisierten Zirkonoxid Y1 - 2002 UR - https://depatisnet.dpma.de/DepatisNet/depatisnet?action=bibdat&docid=WO002002047616A3 ER - TY - JOUR A1 - Gebhardt, F. A1 - Seuss, Sigrid A1 - Turhan, Metehan C. A1 - Hornberger, Helga A1 - Virtanen, Sannakaisa A1 - Boccaccini, Aldo R. T1 - Characterization of electrophoretic chitosan coatings on stainless steel JF - Materials Letters N2 - Electrophoretic chitosan deposits on stainless steel AISI 316 L were produced and characterized. The coating quality (thickness, defectiveness, corrosion protection ability) was seen to depend on the electric field used for EPD. Corrosion studies in concentrated simulated body fluid (SBF5) demonstrated that the surface characteristics of AISI 316 L can be positively influenced by the chitosan coating. KW - Chitosan KW - Electrophoretic deposition KW - Biomaterials KW - Electrochemistry Y1 - 2012 U6 - https://doi.org/10.1016/j.matlet.2011.08.088 VL - 66 IS - 1 SP - 302 EP - 304 ER - TY - PAT A1 - Aechtner, Stefan A1 - Hornberger, Helga A1 - Nagel, Emil A1 - Thiel, Norbert T1 - Composite material and method for the preparation thereof N2 - A composite material with a porous inorganic-nonmetallic matrix and a second material, characterized in that said porous inorganic-nonmetallic matrix has a bending strength of >=40 MPa as measured according to ISO 6 872; said second material is an organic material which at least partly fills the pores of said porous matrix; and said composite material has a modulus of elasticity, E, of >=25 GPa as measured according to ISO 10 477. Y1 - 2001 UR - https://depatisnet.dpma.de/DepatisNet/depatisnet?action=bibdat&docid=US020090001623A1 ER -