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Highly wear-resistant and biocompatible carbon nanocomposite coatings for dental implants
Penkov, O.V.,Pukha, V.E.,Starikova, S.L.,Khadem, M.,Starikov, V.V.,Maleev, M.V.,Kim, D.E. IPC Science and Technology Press 2016 Biomaterials Vol.102 No.-
<P>Diamond-like carbon coatings are increasingly used as wear-protective coatings for dental implants, artificial joints, etc. Despite their advantages, they may have several weak points such as high internal stress, poor adhesive properties or high sensitivity to ambient conditions. These weak points could be overcome in the case of a new carbon nanocomposite coating (CNC) deposited by using a C-60 ion beam on a Co/Cr alloy. The structure of the coatings was investigated by Raman and XPS spectroscopy. The wear resistance was assessed by using a reciprocating tribotester under the loads up to 0.4 N in both dry and wet sliding conditions. Biocompatibility of the dental implants was tested in vivo on rabbits. Biocompatibility, bioactivity and mechanical durability of the CNC deposited on a Co/Cr alloy were investigated and compared with those of bulk Co/Cr and Ti alloys. The wear resistance of the CNC was found to be 250-650 fold higher compared to the Co/Cr and Ti alloys. Also, the CNC demonstrated much better biological properties with respect to formation of new tissues and absence of negative morphological parameters such as necrosis and demineralization. Development of the CNC is expected to aid in significant improvement of lifetime and quality of implants for dental applications. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Khadem, M.,Penkov, O.V.,Pukha, V.E.,Maleyev, M.V.,Kim, D.E. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.80 No.-
The wear resistance and optical properties of ultra-thin diamond-like carbon (DLC) coatings deposited on glass substrates at room temperature were investigated. The coatings were deposited using a C<SUB>60</SUB> ion beam. A sequence of surface treatments including ion-beam etching, molecular-beam deposition and ion-beam deposition were used for production of ultra-thin DLC coatings with a nano-patterned surface. The goal of the surface nano-patterning was to improve the wear resistance of the DLC coatings while maintaining a low thickness to obtain a high optical transparency. The experimental results demonstrated the excellent ability of the ultra-thin DLC coatings to improve the wear resistance of the glass substrates. A comparison between the wear rate for the DLC coating with nano-patterns and that of a more smooth coating revealed that the nano-patterned surface shows a 39% higher wear resistance. Furthermore, the coatings demonstrated a high transparency (94-97%) in the visible-light wavelength range.
Nemati, N.,Emamy, M.,Penkov, O.V.,Kim, J.,Kim, D.E. Elsevier Ltd 2016 Materials & Design Vol.90 No.-
<P>The mechanical and tribological properties of extruded aluminum matrix composites reinforced with various weight percentages (1, 3, 5, 7, 10 wt.%) of Al13Fe4 complex metallic alloys (CMAs) were investigated. The nano-composites were produced using conventional powder metallurgy and a hot extrusion process. The tribological behavior of the composites was investigated under normal loads in the range of 20-80 N using a reciprocating high-temperature tribo-tester over a temperature range of 25-350 degrees C. At an optimized reinforcing agent concentration of 5 wt.%, the composite showed a significant enhancement in Young's modulus (similar to 108 MPa) and hardness (similar to 1.85 GPa). The lowest coefficient of friction of 0.1 was attained at a temperature of 250 degrees C with a reinforcing agent concentration of 5 wt.%. Also, the wear rate was reduced by a factor of similar to 25 compared to the unreinforced aluminum specimen. The significant improvement in the tribological properties of the nanocomposite was attributed to the enhanced mechanical properties due to severe plastic deformation incurred during the extrusion process and incorporation of well distributed CMA nanoparticles in the matrix which provided oobstacles for dislocation motion. Detailed microstructural analyses revealed that incorporation of the second phase to the Al matrix led to microstructure refinement and increased the hardness up to similar to 2 GPa. Furthermore, the nanoparticles aided in the formation of hard and temperature-resistant tribo-layers which reduced the wear rate of the composite (Al-5 wt.% Al13Fe4) down to 1.5 x 10(-4) at 250 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.</P>