The Ni-bearing metals and the Fe-oxides (wustite/magnetite) within sulfides (troilite/pentlandite) in the D'Orbigny angrites were considered for better constraining the changing Redox as well as temperature-compos...
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The Ni-bearing metals and the Fe-oxides (wustite/magnetite) within sulfides (troilite/pentlandite) in the D'Orbigny angrites were considered for better constraining the changing Redox as well as temperature-composition conditions during their formation. microstructures and compositions of sulfide-metal-oxide phase assemblages were characterized by scanning and transmission electron microscopy coupled with polarized optical microscopy to reveal the element diffusion path in the Fe-Ni-S-O quaternary system for their formation. The temperatures under which these reactions took place were between 900 and 600 degrees C. The metal-sulfide assemblage and troilite with wustite-magnetite core-shell crystals restrict D'Orbigny's late Redox-changing conditions. Considering these temperatures together with iron-wustite and wustite-magnetite Redox buffers, late events in D'Orbigny took place under log(fO(2)) similar to -17 to -25.
Direct oesteointegration between a polymeric implant made of a polymer such as a PEEK and host tissues involves direct connection via surface energy, which can be increased by plasma surface modification. Thin coating...
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Direct oesteointegration between a polymeric implant made of a polymer such as a PEEK and host tissues involves direct connection via surface energy, which can be increased by plasma surface modification. Thin coatings are preferably produced by deposition from the gaseous phase (CVD - chemical vapour deposition). In the frame of this research study, PEEK substrates were modified by the PTFE + SiO2/organic silicone multilayer structures that were designed via a biomimetic concept based on algae shell structures. The coatings exhibited mechanical wear resistance and ensured adequate human fibroblast cell proliferation. The proliferation was characterized using confocal microscopy. The analysis together with detailed microstructural characterization with transmission electron microscopy techniques (tem) established a complex correlative microscopy characterization and allowed the determination of the mechanical and biological features of the coatings. High-resolution tem (HRtem) observations revealed possibilities of gas circulation in between the substrate material and the outside environment without making direct contact.
The lifetime of protective coatings is usually limited due to the formation of defects in the form of cracks, resulting in the destruction of coatings. Understanding the initial stages of structural defects during the...
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The lifetime of protective coatings is usually limited due to the formation of defects in the form of cracks, resulting in the destruction of coatings. Understanding the initial stages of structural defects during the wearing process of coatings on the nano- and atomic scale allows for predictions of the lifetimes of fabricated coatings. The main goal of the presented work was to study the nanoscale wear mechanisms of advanced Zr/ZrxN multilayer coatings both ex situ and in situ. These coatings allow for reduced failures due to crack deflection characteristics and the ability for layers by layer coating remove. The analysis indicated thatto increase the quality of the coating's adhesion, it was necessary to decrease the thickness of the metallic buffer layer. This decrease caused the formation of much finer, equiaxial grains, resulting in the stabilization of the isotropic residual stress of the total coating and the improved resistance to the formation of defects in the form of cracks. The adequate thickness of the buffer layer is a very important aspect in the explanation of the differences in the quality of coating adhesion;however, it is insufficient to explain differences in its wear resistance properties. The detailed microstructure study revealed that the nature of the tribofilm formed during the wear process might have a significant impact on the speed of its progression. The analysis showed that at higher phase ratios, namely, 1:4, with a larger amount of ceramic phase in the multilayer structure, a lower amount of the unfavourable hard tribofilm was produced. A similar behaviour was observed in the scratch experiments performed in situ of the scanning electron microscope. In the case of plastic dominated deformation, continuous chips were formed remaining within the scratch track. In the coating with ceramic dominated properties, the chips were discontinuous and moved away from the scratch track during the test. To have adequate coating adhesion to the sub
Wear mechanisms operating at the nanoscale may directly influence mechanical and biological properties of the advanced protective coatings used in industry. In the present research, the biomechanical properties of the...
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Surface functionalization of medical devices made of polyaryletheretherketone (PEEK) is an essential requirement when a direct osteointegration between implants and host tissues is desired. The main objective of the w...
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Surface functionalization of medical devices made of polyaryletheretherketone (PEEK) is an essential requirement when a direct osteointegration between implants and host tissues is desired. The main objective of the work was to improve bio-activity and tribological properties of advanced polymer PEEK type materials through development of biomimetic, smart polytetrafluorethylene (PTFE) composite coatings. The optimal biological (fibroblasts cell proliferation) and tribological (micro-hardness, scratch adhesion) properties of the PTFE coating were found for porous, nano-composite, multi-layered structures. Coatings were more porous on the surface what made it prone for fibroblast cell proliferation, and more dense close to the PEEK substrate, what positively influenced on their tribological properties.
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