Structural and tribological properties of the re-casted dental NiCrMo alloy

The crisis related to the COVID 19 pandemic caused an increase in nickel prices on the global markets. From this perspective, it seems promising to search for the possibilities of effective recycling of nickel-based alloys as biomaterials. The topic of the recasting of Ni-Cr dental alloys is currently being broadly described in the literature. Nonetheless, there are still no conclusive results on the impact of recasting on the quality of the cast dentures. Considering the aforementioned, for research, the effect of recasting on the wear resistance and microstructure of NiCrMo dental alloy was investigated. The Heraenium NA alloy was used for testing. Abrasion resistance was tested by the ball on disc method. Microstructure and wear trace were observed using an optical microscope and a scanning electron microscope. The tests showed a higher wear resistance of the re-casted material. The average coefficient of friction for the initially cast alloys was 0.664, while for the remelted samples the mean value was 0.441. The tested samples are characterised by an abrasive-adhesive wear mechanism. Piling up of the wear tracks edges was observed - the highest for H100. For the H100 samples, a slightly lower average hardness value (HV10) was observed - 226 compared to 233 (HV10) for the samples made from the re-casted alloy (H0). The presence of a dendritic structure of alloys was demonstrated. Blocky eutectic precipitations are visible against the matrix. The observed growth of interdendritic precipitations constitute a natural barrier for the counterpart material and increases its tribological properties. Obtained results suggest that alloy recasting does not constitute a limitation to its use. © 2021 Institute of Physics Publishing. All rights reserved.

Synthesis of a novel anti-fog and high-transparent coating with high wear resistance inspired by dry rice fields.

During the outbreak of COVID-19, the fogging of goggles was a fatal problem for doctors. At present, there are many ways to prevent fogging by adjusting surface wettability. However, the mechanical properties of most super-hydrophilic antifogging coatings are poor, easy to lose their antifogging properties when encountering fingers or cloth friction. To address this issue, the Konjac Glucomannan was cross-linked with water-soluble silicone fluid to form a binder, then being combined with the modified Ecokimera to prepare an eco-friendly super-hydrophilic coating that possessed excellent super-hydrophilicity, and the water contact angle (WCA) was 2.51 ± 1°. In addition, the WCA is still about 5° after 180 times of antifogging tests. The friction resistance of the coating was as high as 24 m. Moreover, the light transmittance was only reduced by 3%. Besides, they also had the excellent self-cleaning property. After being stored in the laboratory environment for 90 days, it can still maintain the hydrophilic property (WCA is about 5°). In general, the method proposed in this study is low-cost and eco-friendly, and can be widely used in the preparation of antifogging coatings.