Papers by Keyword: Dispersion Ceramic

Abstract: Functional ceramic nanopowders with emphasis on biomedical applications were engineered by gas-phase condensation using the CO₂ laser vaporization (LAVA) technique. Europium doped strontium aluminate nanoparticles (NP) were prepared from a SrO/α-Al₂O₃/Eu₂O₃ powder mixture. Excited with ultraviolet radiation (UV), the as-prepared amorphous NP revealed red photoluminescence emission. After annealing in reductive atmosphere crystalline SrAl₂O₄:Eu²⁺ nanopowder was obtained showing strong green emission at UV excitation. Ferrimagnetic iron oxide (Fe_xO_y) nanopowders were prepared starting from α-Fe₂O₃ powder. In oxygen-free condensation atmosphere γ-Fe₂O₃ NP were obtained. Oxygen as condensation gas yielded γ-and ε-Fe₂O₃ NP. Superparamagnetic NP were prepared starting from α-Fe₂O₃/SiO₂ mixtures. Depending on the mixing ratio γ-Fe₂O₃ nanocrystallites embedded in a SiO₂ glass matrix or γ-Fe₂O₃-SiO₂ Janus NP were obtained. These NP provide a reactive SiO₂ interface for subsequent functionalizing. The co-vaporization of α-Al₂O₃ as the main proportion and t-ZrO₂ yielded zirconia-toughened-alumina NP. Reinforcing effects of Al₂O₃-ZrO₂ dispersion ceramics will be increased using NP with an intraparticle dispersion of these phases. Future applications of the LAVA prepared NP include biological fluorescence labeling, and drug targeting, magnetic resonance imaging, and hyperthermic cancer therapy, as well as sintering of load bearing ceramic implants, respectively.

Abstract: The primary purpose of this work was the examination of the surface and the strength of ATZ ceramic after hydrothermal treatment. Hydrothermal treatment of ATZ ceramic leads to changes of roughness and phase composition on the surface. The phase composition and the microstructure on the surface and within the peripheral zone were determined after applying a stepwise broad ion beam polishing technique and quantitative phase analysis. With this technique a penetration depth of the phase transformation of less than 14 µm was observed. Investigations of the cross sectional area by means of FESEM have shown a transformation zone of about 9 µm. Both methods lead to comparable results with a very small, morphologically changed peripheral layer. The study of the strength after ageing with different thickness of the samples showed that for a thickness of 2.0 mm there is no negative influence on mechanical behaviour. In consideration of this fact no significant change of tribological properties is expected.

Abstract: The aim of this study was to record corrosion behaviour of ZTA and ATZ ceramics under hydrothermal conditions and under influence of boiling acids. Ageing was performed for 30 h and for 100 h in an autoclave at 134 °C and at a pressure of 2 bar. The sample surface was characterised with the help of measurements of surface finish, strength and microhardness, as well as by means of determination of wetting angle of contact. Leaching behaviour was analysed by means of scanning electron micrographs and weightings. The results of all tests with ZTA and ATZ ceramics performed in connection with this survey showed positive results, i.e. neither acid treatment nor hydrothermal ageing resulted in significant changes of properties.

Abstract: For orthopaedic applications an Alumina Toughened Zirconia Ceramic was tested regarding its mechanical behaviour. We observed a marked higher strength compared to the requirements according to FDA guidelines and a significantly higher strength compared to alumina ceramic despite of 15 % decreased fatigue burst strength. The wear resistance after ring-on-disc method is significantly improved comparing to standard Al2O3/Al2O3 pairings. It means the application of endoprosthetic components made of ATZ-ceramic offers more safety and reliability.

Abstract: Abstract. A new ceramic material for orthopaedic applications was investigated. Therefore a gradient ceramic was prepared with a zirconia gradient within an alumina matrix by an infiltration process. This material was characterized regarding its microstructure, stress distribution inside the ceramic, zirconia phase analysis and strength. It could be shown that the flexural strength of the new ceramic is twice as high as of pure alumina ceramic. By this and the low monoclinic zirconia content this material offers a potential for its use in high load bearing implants like hip heads for joint endoprostheses.