TY - JOUR A1 - Köck, Hannah A1 - Striegl, Birgit A1 - Kraus, Annalena A1 - Zborilova, Magdalena A1 - Christiansen, Silke H. A1 - Schäfer, Nicole A1 - Grässel, Susanne A1 - Hornberger, Helga T1 - In Vitro Analysis of Human Cartilage Infiltrated by Hydrogels and Hydrogel-Encapsulated Chondrocytes JF - Bioengineering N2 - Osteoarthritis (OA) is a degenerative joint disease causing loss of articular cartilage and structural damage in all joint tissues. Given the limited regenerative capacity of articular cartilage, methods to support the native structural properties of articular cartilage are highly anticipated. The aim of this study was to infiltrate zwitterionic monomer solutions into human OA-cartilage explants to replace lost proteoglycans. The study included polymerization and deposition of methacryloyloxyethyl-phosphorylcholine- and a novel sulfobetaine-methacrylate-based monomer solution within ex vivo human OA-cartilage explants and the encapsulation of isolated chondrocytes within hydrogels and the corresponding effects on chondrocyte viability. The results demonstrated that zwitterionic cartilage–hydrogel networks are formed by infiltration. In general, cytotoxic effects of the monomer solutions were observed, as was a time-dependent infiltration behavior into the tissue accompanied by increasing cell death and penetration depth. The successful deposition of zwitterionic hydrogels within OA cartilage identifies the infiltration method as a potential future therapeutic option for the repair/replacement of OA-cartilage extracellular suprastructure. Due to the toxic effects of the monomer solutions, the focus should be on sealing the OA-cartilage surface, instead of complete infiltration. An alternative treatment option for focal cartilage defects could be the usage of monomer solutions, especially the novel generated sulfobetaine-methacrylate-based monomer solution, as bionic for cell-based 3D bioprintable hydrogels. KW - osteoarthritis KW - human articular cartilage KW - chondrocytes KW - hydrogels KW - zwitterionic monomers KW - infiltration Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-61235 N1 - Corresponding author: Helga Hornberger VL - 10 SP - 1 EP - 21 PB - MDPI ER - TY - JOUR A1 - Kloiber, Jessica A1 - Schultheiß, Ulrich A1 - Sotelo, Lamborghini A1 - Sarau, George A1 - Christiansen, Silke A1 - Gavras, Sarkis A1 - Hort, Norbert A1 - Hornberger, Helga T1 - Corrosion behaviour of electropolished magnesium materials JF - Materials Today Communications N2 - Although magnesium and its alloys are promising candidates as biodegradable implant materials, the tendency for localized corrosion mechanism in physiological environment limit their biomedical application. Electropolishing is an attractive strategy for improving the corrosion behaviour of metals, but it is still largely unexplored in magnesium materials. In this study, the characterization of electropolished surfaces of AM50 and pure magnesium was performed, focussing on their in vitro degradation behaviour in cell medium. Corrosion rates were evaluated using potentiodynamic polarisation. The surface morphology before and after the onset of corrosion was investigated by scanning electron microscopy and confocal laser scanning microscopy. The presented electropolishing process led to improved surface performances, observable by significantly lower corrosion rates (0.08 mm·year-1 in Dulbecco's modified Eagle's medium), lower arithmetical mean height (0.05 µm), lower water contact angle (25-35°) and lower micro hardness (35-50 HV 0.1) compared to mechanically and chemically treated surfaces. MgO/Mg(OH)2 could be detected on electropolished surfaces. The localized corrosion mode could be reduced, but not entirely prevented. Electropolishing shows great potential as post-treatment of magnesium-based components, but detailed tests of the long-term corrosion behaviour are an important area of future research. KW - biomedical application KW - corrosion behaviour KW - electropolishing KW - magnesium alloy KW - pure magnesium KW - surface characterization Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-68254 N1 - Corresponding author: Helga Hornberger PB - Elsevier ET - Journal Pre-proof ER - 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 - 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 - Randow, Clemens A1 - Fleck, Claudia T1 - Fatigue and surface structure of titanium after oxygen diffusion hardening JF - Materials Science & Engineering A N2 - The characterization of oxygen diffusion zone in titanium and the effect of this zone on macroscopic properties are still of high interest for a base to predict and to enhance life time of titanium and titanium alloy components. The aim of this study was to contribute to the understanding of the impact of oxygen on fatigue properties of oxygen diffusion hardened Ti and Ti alloys. Oxygen diffusion hardening implies two process steps, first the oxidation of the surface and secondly the diffusion of oxygen into metal matrix. Due to the one-step treatment used in this study the oxidation step could take place easily avoiding scaling and grain boundary diffusion. In spite of this precaution, the fatigue properties in the present study were found to be decreased after the performed oxygen diffusion hardening. The reason for the reduction of mechanical properties were claimed to be oxide clusters on the surface acting as crack initiation sites. Comparison and discussion with literature revealed varying partially contradictory fatigue results. Therefore precise analysis of the fatigue failure is necessary as a base for further development of the oxygen diffusion hardening. KW - Titanium alloys KW - Oxygen diffusion KW - Surface hardening KW - Fatigue Y1 - 2015 U6 - https://doi.org/10.1016/j.msea.2015.02.006 VL - 630 SP - 51 EP - 57 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 - Belli, Renan A1 - Kreppel, Stefan A1 - Petschelt, Anselm A1 - Hornberger, Helga A1 - Boccaccini, Aldo R. A1 - Lohbauer, Ulrich T1 - Strengthening of dental adhesives via particle reinforcement JF - Journal of the Mechanical Behavior of Biomedical Materials N2 - The bond between methacrylic polymer adhesives and dental restoratives is not perfect and may fail either in the short or in the long term. This study aims to evaluate the effects of particle incorporation in a self-etch model adhesive on mechanical and physical properties that are relevant during application and service. Filled adhesives containing 5, 10, 15 or 25 wt% glass fillers were compared to their unfilled counterpart in terms of water sorption and solubility; viscosity and dynamic viscosity during polymerization were recorded using rheological measurements and compared to FTIR analysis of the real-time degree of cure. Elastic modulus and ultimate tensile strength measurements were performed in uniaxial tension; the energy to fracture was used to calculate the fracture toughness of the adhesives. Finally, the experimental adhesives were applied on dentin substrate to test the bond strength using the microtensile test. Results showed that the incorporation of 5–10 wt% nanofiller to self-etching dental adhesives is efficient in accelerating the polymerization reaction and increasing the degree of cure without compromising the film viscosity for good wettability or water sorption and solubility. Fillers increased the elastic modulus, tensile strength and fracture toughness to a plateau between 5 and 15 wt% filler concentration, and despite the tendency to form agglomerations, active crack pinning/deflection toughening mechanisms have been observed. The bond strength between resin composite and dentin was also improved when adhesives with up to 10 wt% fillers were used, with no additional improvements with further packing. The use of fillers to reinforce dental adhesives may therefore be of great practical benefit by improving curing and mechanical properties. KW - Nanoparticles KW - Bond strength KW - Elasticity KW - Adhesives KW - Dentin Y1 - 2014 U6 - https://doi.org/10.1016/j.jmbbm.2014.05.007 VL - 37 IS - 9 SP - 100 EP - 108 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 - 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 - 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 - PAT A1 - Muerrle, Ulrich A1 - Hornberger, Helga T1 - Method of making a ceramic restoration N2 - Production of a dental reconstruction comprises: (a) forming a mold (12) from a model (10); (b) using (12) to make an isotropically heat-expandable replica from a ceramic precursor (14); (c) oxidizing (14) to produce an enlarged ceramic replica; (d) forming a silicone mold from this replica; (e) using (d) to make a second ceramic replica; and (f) sintering the second replica with volume reduction to form a replica identical to (10). T2 - Verfahren zur Herstellung einer Zahnrestauration aus Keramik Y1 - 2003 UR - https://depatisnet.dpma.de/DepatisNet/depatisnet?action=bibdat&docid=EP000001346702A1 ER - TY - JOUR A1 - Manaranche, Claire A1 - Hornberger, Helga T1 - A proposal for the classification of precious dental alloys according to their resistance to corrosion based on the iso 10271 standard JF - European Cells and Materials N2 - A lot of dental alloys are available on the market. Among these alloys, there are the conventional alloys, the so called casting alloys used without ceramics, the bonding alloys used with high fusing ceramics and the universal alloys used without or with low fusing ceramics. It is im portant to know the physical and mechanical properties of these materials but also their biocompatibility and their resistance to corrosion. Dental alloys are generally placed in the mouth for many years, they must not induce adverse biological reactions such as gingival swelling and erythema, mucosal pain and lichenoid reactions. Although these troubles are often caused not by the materials itself (1, 2), they can be induced by the metallic ions released during their corrosion. In order to decrease the risks to the health, it is necessary to study the corrosion of the dental alloys. Currently, the ISO 10271 Standard (3), describes 3 different corrosion tests: a static immersion test (chemical corrosion), an electrochemic al test and a tarnish test. However, there are no indications yet about the possible interpretation of test results. In this paper, we propose a method to compare and classify the dental alloys in relation to their chemical and electrochemical corrosion results. METHODS: The material tested are pure metals such as gold, palladium, silver, copper and zinc as well as dental alloys which are commercially sold (see Table 1). 54 different materials have been tested. A minimum of four samples of each material were tested by electrochemic al corrosio n and a minimum of three in chemical test. The samples were cast and prepared as indicated by the manufacturer and by the ISO 10271. For the electrochemical test, the samples are in the form of disks 11 mm in diameter. They are tested with a potentiostat/galvanostat Voltalab Model 21. For the chemical test, the samples are rectangular with the dimensions 35X10X1.7 mm. The solution used and the operating conditions are described in the ISO 10271. The concentration of metallic ions released is measured by Induced Coupled Plasma Y1 - 2003 UR - https://www.researchgate.net/publication/242728857_A_proposal_for_the_classification_of_precious_dental_alloys_according_to_their_resistance_to_corrosion_based_on_the_ISO_10271_standard VL - 5 IS - SUPPL. 1 SP - 34 EP - 36 PB - Univ. of Wales CY - Aberystwyth, Wales 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 - Reich, Sven A1 - Hornberger, Helga T1 - The effect of multicolored machinable ceramics on the esthetics of all-ceramic crowns JF - Journal of Prosthetic Dentistry N2 - Statement of problems: Computer-aided design/computer-assisted machining systems offer the possibility of fabricating restorations from one machinable ceramic block. Whether multishaded blocks improve esthetic results and are a viable alternative to individually stained ceramics has not been fully determined. Purpose: The aim of this investigation was to examine the effect of multishaded blocks on the esthetic appearance of all-ceramic CEREC crowns and compare these crowns with single-shade and stained restorations. Material and methods: Ten subjects were included in this study. For each subject, 6 different crowns were milled with the use of a CEREC machine. One crown was milled from each of the following machinable ceramic materials: CEREC Vitablocs Mark II in classic colors; Vitablocs Mark II in 3D-Master colors; Vitablocs Mark II in either classic or 3D-Master colors, with additional staining; Megadenta Bloxx multishaded; Mark II experimental multilayer; and an experimental multilayer leucite ceramic. Three independent examiners assessed the esthetic appearance of crowns fabricated to match each subject's anterior tooth shade. A scale of 1 to 6 was used to score the shade match and esthetic adaptation of each crown, with 1 representing excellent characteristics and 3.5 serving as the threshold for clinical acceptability. The examiners' scores were averaged, and the mean values were analyzed with the Wilcoxon signed rank test (P=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 - TY - JOUR A1 - Hornberger, Helga A1 - Weissmann, R. A1 - Lutz, N. T1 - Machining of silica glasses using excimer laser radiation JF - Glastechnische Berichte - Glass Science and Technology Y1 - 1996 VL - 69 IS - 2 SP - 44 EP - 49 ER - TY - JOUR A1 - Christiansen, Silke H. A1 - Albrecht, M. A1 - Strunk, Horst P. A1 - Hornberger, Helga A1 - Marquis, Peter M. A1 - Franks, J. T1 - Mechanical properties and microstructural analysis of a diamond-like carbon coating on an alumina/glass composite JF - Journal of Materials Research N2 - We investigate the mechanical and microstructural properties of a diamond-like carbon coating (DLC) which is deposited by plasma enhanced chemical vapor deposition (PECVD) onto an alumina/aluminosilicate glass composite used for biomedical applications. Ball-on-ring tests yield a fracture strength that is essentially influenced by the surface topology/roughness. The surface topology of the coating is investigated by atomic force microscopy (AFM). Tribology tests and nanoindentation represent the wear resistance and hardness; these are properties that are mainly influenced by the microstructural properties of the DLC coating. This microstructure is investigated by transmission electron microscopy (TEM) and analyzed by parallel electron energy loss spectroscopy (PEELS). For the general applicability of the coated composite, the interfacial adhesion of the DLC coating on the comparably rough substrate (roughness amplitudes and wavelengths are in the micrometer range) is important. Therefore, we focus on TEM investigations that show the interface to be free of gaps and pores that we, together with a characteristic microstructure adjacent to the interface, relate to the excellent adhesion. The interlayer consists of a high density of SiC grains, part of them directly bound to the substrate, and part of them bound to other SiC grains. This interlayer is followed by an essentially different region of the coating as concerns the microstructure; this region consists of nanocrystalline diamond particles embedded in an amorphous carbon matrix. It is this heterogeneous microstructure to which we attribute (i) the good adhesion based upon the interface stabilizing SiC grains, and (ii) the high hardness and wear resistance based upon the diamond nanocrystals in the coating. Y1 - 1996 U6 - https://doi.org/10.1557/JMR.1996.0244 VL - 11 IS - 8 SP - 1934 EP - 1942 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 - JOUR A1 - Hornberger, Helga A1 - Marquis, Peter M. A1 - Franks, J. T1 - The impact of diamond-like coatings on the strength of dental ceramics JF - Journal of Dental Research Y1 - 1995 VL - 74 SP - 522 ER - TY - JOUR A1 - Hornberger, Helga A1 - Marquis, Peter M. T1 - Mechanical properties and microstructure of In-Ceram BT - a ceramic-glass composite for dental crowns JF - Glastechnische Berichte - Glass Science and Technology Y1 - 1995 VL - 68 IS - 6 SP - 188 EP - 194 ER - TY - JOUR A1 - Hornberger, Helga A1 - Marquis, Peter M. A1 - Christiansen, Silke H. A1 - Albrecht, M. A1 - Strunk, Horst P. A1 - Franks, J. T1 - Microstructure of a high strength alumina-glass composite combined with a diamond like carbon coating JF - Electron Microscopy and Analysis N2 - We investigate the mechanical and microstructural properties of a diamond-like carbon coating (DLC) which is deposited by plasma enhanced chemical vapor deposition (PECVD) onto an alumina/aluminosilicate glass composite used for biomedical applications. Ball-on-ring tests yield a fracture strength that is essentially influenced by the surface topology/roughness. The surface topology of the coating is investigated by atomic force microscopy (AFM). Tribology tests and nanoindentation represent the wear resistance and hardness; these are properties that are mainly influenced by the microstructural properties of the DLC coating. This microstructure is investigated by transmission electron microscopy (TEM) and analyzed by parallel electron energy loss spectroscopy (PEELS). For the general applicability of the coated composite, the interfacial adhesion of the DLC coating on the comparably rough substrate (roughness amplitudes and wavelengths are in the micrometer range) is important. Therefore, we focus on TEM investigations that show the interface to be free of gaps and pores that we, together with a characteristic microstructure adjacent to the interface, relate to the excellent adhesion. The interlayer consists of a high density of SiC grains, part of them directly bound to the substrate, and part of them bound to other SiC grains. This interlayer is followed by an essentially different region of the coating as concerns the microstructure; this region consists of nanocrystalline diamond particles embedded in an amorphous carbon matrix. It is this heterogeneous microstructure to which we attribute (i) the good adhesion based upon the interface stabilizing SiC grains, and (ii) the high hardness and wear resistance based upon the diamond nanocrystals in the coating. Y1 - 1995 U6 - https://doi.org/10.1557/JMR.1996.0244 SP - 559 EP - 562 ER -