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Abstract: This research explores how variations in laser powder bed fusion (LPBF) parameters—laser power (P), scanning speed (v), and base plate preheating temperature (ϑp)—affect the mechanical properties of the EOS Co-Cr SP2 dental alloy. A central composite design (CCD) was used to optimize the process parameters. Mechanical testing focused on crucial properties for dental applications, including yield strength (Rp0.2), elongation (ε), toughness (KVa), and flexural strength (Rms). Microstructural analysis was conducted using light and electron microscopy, while XRD identified microstructural phases. Statistical analysis (ANOVA, Scheffé post hoc test, α = 0.05) revealed significant effects of P, v, and ϑp on the mechanical properties. Response surface models (RSMs) were developed, and optimal parameters were determined to achieve maximum toughness and flexural strength. Maximum values were obtained with laser power above 205Wand base plate preheating at 310 ◦C. The mathematical model predicted toughness values with less than 5% deviation from experimental results, indicating high accuracy.
Keywords: LPBF, production parameters, Co-Cr dental alloy, CCD, mechanical properties, ANOVA
Published in DiRROS: 18.10.2024; Views: 220; Downloads: 8181
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Abstract: Magnesium and its alloys, valued for their lightweight and durable characteristics, have garnered increasing attention for biomedical applications due to their exceptional biocompatibility and biodegradability. This work introduces a comparison of advanced and basic methods—laser texturing and sandblasting—on magnesium surfaces to enhance bioactivity for biomedical applications. Employing a comprehensive analysis spanning surface morphology, hardness, wettability, tribological performance, and corrosion behavior, this study elucidates the intricate relationship between varied surface treatments and magnesium’s performance. Findings reveal that both laser texturing and sandblasting induce grain refinement. Notably, sandblasting, particularly with a duration of 2 s, demonstrates superior wear resistance and reduced corrosion rates compared to untreated magnesium, thereby emerging as a promising approach for enhancing magnesium bioactivity in biomedical contexts. This investigation contributes to a deeper understanding of the nuanced interactions between diverse surface treatments and their implications for magnesium implants in chloride-rich environments, offering valuable insights for prospective biomedical applications.
Keywords: biomaterial, microstructure, hardness, friction/wear, corrosion
Published in DiRROS: 18.10.2024; Views: 187; Downloads: 12412
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Abstract: Fungal growth and degradation of wood may be caused by damage in the surface coating. The larger the cracks, the greater in principle the possibility of moisture-induced problems. Measuring basic unknown material parameters and employing hygrothermal simulations, the suitability and the maximum acceptable vertical crack size in the surface coating for a given bottom window profile made of thermally modified (TM) spruce(wood) with that made of native spruce were compared for location Ljubljana. Validation with the field test data was the second objective of the respective research. The average calculated maximum moisture content in TM spruce is about 4% (kg/kg) lower than that of native spruce. The 3 mm wide crack in the surface coating of a window frame made of native spruce is of the highest concern, whereas a 9 mm wide crack in the coating of a TM spruce profile is still acceptable. As far as moisture content is concerned in our study the TM spruce window frames were proved to be significantly more suitable for installation than the corresponding frames made of native Norway spruce. It was shown that isopleth, VTT and biohygrothermal models for mould growth do not properly capture the comparison between both materials, mainly because they classify both in the same material class/substrate category and they do not consider the material moisture content.
Keywords: hygrothermal simulations, mould growth modelling, cracks in surface coating, thermally modified wood, wooden window frame
Published in DiRROS: 16.10.2024; Views: 229; Downloads: 385
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Abstract: This work aims to evaluate the corrosion and biocompatibility properties of oxide films generated on Ti6Al4V alloys using both traditional and novel methods. Oxide films were generated by anodization and plasma treatment to achieve a blue surface finish. The oxide films were then characterized and compared to a native film formed on the Ti6Al4V. Electrochemical tests, incorporating potentiodynamic tests and electrochemical impedance spectroscopy, were employed to define the electrochemical resistance of oxides in an environment simulating biological exposure. In vitro tests were conducted to study ion release and biocompatible properties over a 6-week period of exposure to a 0.9 wt% NaCl solution, at body temperature. Various spectroscopic techniques, including ToF-SIMS, XRD, and Raman analysis, were used to study the structure and chemistry of the oxide films. The sub-surface layer was analysed by microstructural investigation. The type of oxidation was found to have a key influence on the oxide composition, especially with respect to the depth distribution of the individual alloy elements through the oxide film. The oxidation process determines which of the alloying elements are released into the environment, as a result of the corrosion reactions.
Keywords: oxide film, biocompatibility, surface characterization, ion release, simulated body fluid
Published in DiRROS: 16.10.2024; Views: 235; Downloads: 221
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Abstract: The paper seeks to examine the social image of suicide at the end of the 19th and the beginning of the 20th century, focusing on the case of Trieste as a major Austrian urban centre, where the suicide rates were visibly increasing from at least the 1870s onwards. The perception of the growing presence of suicide in society made it possible to observe the reflec-tions on suicide from the last quarter of the 19th century, originating from different parts of Europe (Morselli, Masaryk, Durkheim), and at the same time how the discourses around suicide shed light on a somewhat broader picture of society, including its fears (of social problems and change, not least the potential threat of the imitative effect that the daily press was believed to create by reporting on suicides).The newspaper discourse usually followed the scientific publications of the time, and the contemporaneous observations on the mass of suicides were confirmed through statistical analyses and medical, sociological, philosophical, and other debates, while raising many other social issues with which suicide in urban areas could be linked (alcoholism, the growth of the proletariat, poverty, changing values, etc.). All these factors shaped the public debate on suicide as a problem of modern society, with an emphasis on (big) cities, where the prob-lem of suicide was much more pronounced than in smaller, non-industrial towns, or in the countryside of the Austrian Littoral.
Keywords: suicide, cities, modernisation, 1870-1910, Trieste, Koper, Austria-Hungary
Published in DiRROS: 15.10.2024; Views: 159; Downloads: 95
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