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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 -