@misc{MuerrleHornberger, author = {Muerrle, Ulrich and Hornberger, Helga}, title = {Method of making a ceramic restoration}, pages = {8}, abstract = {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).}, language = {en} } @article{HornbergerMarquisFranks, author = {Hornberger, Helga and Marquis, Peter M. and Franks, J.}, title = {The impact of diamond-like coatings on the strength of dental ceramics}, series = {Journal of Dental Research}, volume = {74}, journal = {Journal of Dental Research}, pages = {522}, language = {en} } @article{HornbergerMarquis, author = {Hornberger, Helga and Marquis, Peter M.}, title = {Mechanical properties and microstructure of In-Ceram}, series = {Glastechnische Berichte - Glass Science and Technology}, volume = {68}, journal = {Glastechnische Berichte - Glass Science and Technology}, number = {6}, pages = {188 -- 194}, language = {en} } @article{KloiberAnetsbergerSchultheissetal., author = {Kloiber, Jessica and Anetsberger, Viktoria and Schultheiß, Ulrich and Hornberger, Helga}, title = {High quality surfaces of magnesium alloy AZ31 by adjusting appropriate electropolishing parameters}, series = {Electrochimica Acta}, volume = {513}, journal = {Electrochimica Acta}, publisher = {Elsevier}, doi = {10.1016/j.electacta.2024.145547}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-79298}, language = {en} } @article{KloiberSchultheissHornberger, author = {Kloiber, Jessica and Schultheiß, Ulrich and Hornberger, Helga}, title = {Impact of heat treatment on the surface quality of electropolished WE43 alloy}, series = {Materials Letters}, volume = {397}, journal = {Materials Letters}, publisher = {Elsevier BV}, issn = {0167-577X}, doi = {10.1016/j.matlet.2025.138821}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-83512}, pages = {5}, abstract = {In this study, the Mg alloy WE43 was solution annealed and precipitation hardened prior to electropolishing to evaluate the effects of different microstructures on the electropolishing result. While coarsely distributed precipitates led to surfaces showing wavy structures and dents after electropolishing, a uniform microstructure resulted in an even finish of the surface. The homogenization and refinement of the microstructure by heat treatment is a method to ensure improved electropolished surfaces of Mg materials}, language = {en} } @article{ManarancheHornberger, author = {Manaranche, Claire and Hornberger, Helga}, title = {A proposal for the classification of precious dental alloys according to their resistance to corrosion based on the iso 10271 standard}, series = {European Cells and Materials}, volume = {5}, journal = {European Cells and Materials}, number = {SUPPL. 1}, publisher = {Univ. of Wales}, address = {Aberystwyth, Wales}, pages = {34 -- 36}, abstract = {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}, language = {en} } @article{SchultheissHornberger, author = {Schultheiß, Ulrich and Hornberger, Helga}, title = {Comparison of etchants for corrosion-resistant stainless steels in medical engineering}, series = {Practical Metallography}, volume = {62}, journal = {Practical Metallography}, number = {1}, publisher = {de Gruyter}, doi = {10.1515/pm-2024-0094}, pages = {19 -- 30}, abstract = {Corrosion-resistant stainless steels are widely used in medical engineering. Today, additive manufacturing techniques are also used for this purpose, in particular for implant steels. Additively processed materials sometimes react differently to etching than conventionally processed ones. The use of etchants for contrasting the microstructure must therefore be adapted. Chemical etching using V2A etchant, Murakami, and anhydrous Kalling solutions, as well as electrochemical etching using nitric acid, sodium hydroxide, and oxalic acid were performed. Etched samples made of conventionally processed X2CrNi-Mo17-12-2 were compared to samples manufactured using selective laser melting and sintering, and the optimal contrast was developed in each case. It can be shown that the different etchants reveal different microstructural constituents and that etchants must therefore be selected as a function of the application.}, language = {en} } @unpublished{KloiberAnetsbergerSchultheissetal., author = {Kloiber, Jessica and Anetsberger, Viktoria and Schultheiss, Ulrich and Hornberger, Helga}, title = {Electropolishing of Magnesium Alloy Az31 with Varying Electrolyte Concentrations and Applied Potentials}, publisher = {SSRN}, doi = {10.2139/ssrn.4991311}, abstract = {Magnesium alloy AZ31 is a light material with a good mechanical stability and is used in various engineering applications. Although its tendency to localized corrosion is a limiting factor in its use. Electropolishing is a widely used process for improving the surface roughness and corrosion behavior of metals. However, there is a lack of knowledge about the electropolishing of magnesium and its alloys. In this study, an optimal electropolishing process for AZ31 was developed to improve the surface properties by varying the electrolyte concentration and the applied potential. The electrolyte composition was a mixture of phosphoric acid, ethanol and deionized water. The applied potentials were selected based on measured current density potential curves. Thereby, electropolishing was performed up to an electric charge of 18 As. The experimental results indicate that the electropolishing process should be carried out at a low current density to avoid bubble evolution and surface defects. Therefore, the concentration of the electropolishing electrolyte should have an appropriate low conductivity, and the applied potential should be in the transient or passive region of the polarization curve recorded prior to electropolishing. It could be shown that an optimized electropolishing process improved the surface of AZ31 by providing a bright and mirror-like surface and a lower roughness compared to a mechanically ground surface.}, language = {en} } @article{HornbergerWeissmannLutz, author = {Hornberger, Helga and Weissmann, R. and Lutz, N.}, title = {Machining of silica glasses using excimer laser radiation}, series = {Glastechnische Berichte - Glass Science and Technology}, volume = {69}, journal = {Glastechnische Berichte - Glass Science and Technology}, number = {2}, pages = {44 -- 49}, language = {en} } @article{HornbergerMarquisChristiansenetal., author = {Hornberger, Helga and Marquis, Peter M. and Christiansen, Silke H. and Albrecht, Manuel and Strunk, Horst P. and Franks, J.}, title = {Microstructure of a high strength alumina-glass composite combined with a diamond like carbon coating}, series = {Electron Microscopy and Analysis}, journal = {Electron Microscopy and Analysis}, doi = {10.1557/JMR.1996.0244}, pages = {559 -- 562}, abstract = {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.}, language = {en} } @article{ChristiansenAlbrechtStrunketal., author = {Christiansen, Silke H. and Albrecht, Manuel and Strunk, Horst P. and Hornberger, Helga and Marquis, Peter M. and Franks, J.}, title = {Mechanical properties and microstructural analysis of a diamond-like carbon coating on an alumina/glass composite}, series = {Journal of Materials Research}, volume = {11}, journal = {Journal of Materials Research}, number = {8}, doi = {10.1557/JMR.1996.0244}, pages = {1934 -- 1942}, abstract = {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.}, language = {en} } @article{KloiberSchultheissSoteloetal., author = {Kloiber, Jessica and Schultheiß, Ulrich and Sotelo, Lamborghini and Sarau, George and Christiansen, Silke H. and Gavras, Sarkis and Hort, Norbert and Hornberger, Helga}, title = {Corrosion behaviour of electropolished magnesium materials}, series = {Materials Today Communications}, journal = {Materials Today Communications}, edition = {Journal Pre-proof}, publisher = {Elsevier}, doi = {10.1016/j.mtcomm.2023.107983}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:898-opus4-68254}, abstract = {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.}, language = {en} }