Rosa Katunar, MariaIgnacio Pastore, JuanCisilino, AdrianMerlo, Julieta...
9页
查看更多>>摘要：Osteoporosis is a skeletal disorder characterized by a decrease in bone strength leading to a higher risk of fracture. In this scenario, many osteoporotic patients require permanent prosthesis. Surface modification is a strategy to improve the osseointegration for cementless implants. This work assesses the in vivo performance of a surface modification consisting in a bioactive silica-based layer with strontium-doped bioactive glass particles. The layer was made by sol-gel and applied onto titanium nail-shaped implants. Osseointegration tests were performed on an osteoporotic rat model generated by ovariectomization. The effectiveness of the osteoporotic rat model was systematically analyzed for structure and bone quality using classic and novel techniques: nano indentation, micro-Raman spectroscopy and digital image processing. It was found that Sr-glass coatings applied on nail-shaped implants result with lower numbers of particles than for plane samples. The positive effect of bioactive Sr-glass coatings on the new bone tissue formation was evident from the results of the Raman tests. Besides, histomorphometric results showed that the newly formed bone thicknesses around coated Sr-bioactive implants are 15% larger than those formed around titanium materials 15 and 30 days after implantation. These results indicated that even when the nail-shaped implants have a relative low number of bioactive Sr-glass particles, they have a positive effect to induce the formation of new bone. Further research is needed to find the means to increase the number of particles in the coating, while tests at longer times are necessary to investigate the period of effectiveness.
查看更多>>摘要：Based on the excellent thermodynamic and service performances of nano-structured coatings, 8YSZ nano agglomerated spraying powder and its nano-structured thermal barrier coating (TBC) were successfully prepared by the integrated application of nanotechnology and atmospheric plasma spraying. The influences of spraying granulation process (solid content of slurry and inlet air temperature) on the spraying powder characteristics and the water quenching-thermal shock cycling behavior at 1050 ?degrees C of 8YSZ nano-structured TBC were investigated, respectively. The results showed that the nano-agglomerated powders exhibit apple-like, hollow spheroids with relatively uniform particle size when the spraying granulation process involved a 40% solid content of slurry, a 240 ?degrees C inlet air temperature, and a 35 Hz atomizer rotation frequency. The fluidity and apparent density were 57.53 s/50 g and 1.39 g/cm(3), respectively. The nano-agglomerated 8YSZ spraying powders met the requirements of plasma-spraying technology. The plasma-sprayed 8YSZ nano-structured coating was composed of a single t-ZrO2 phase, had a layered structure and a certain amount of nanostructures, and presented a special "bimodal microstructure ". The average porosity of the coating was 7.49%. 8YSZ nano structured TBC failed layer-by-layer after water quenching-thermal shock 264 cycles at 1050 ?degrees C. The main reasons for the failure of 8YSZ nano-structured TBC were the large thermal stress and cracks in the substrate caused by the water quench-thermal shock cycle, and the mismatch of thermal expansion between the metal bond coat and the ceramic coat.
查看更多>>摘要：High-entropy (AlCrTiZrNb)N/WS2 nano-multilayers with different thicknesses of WS2 layers were synthesized by reactive magnetron sputtering. The influence of MoS2 layers on the microstructure of the nano-multilayered films was studied by X-ray diffraction (XRD), scanning electron microscope (SEM), and high-resolution transmission electron microscope (HRTEM). Mechanical properties were examined through nanoindentation, HSR-2M coating friction and wear tester. The results show that when the thickness of the WS300.6 layer is less than 1.2 nm, the WS2 layer can be transformed into a cubic phase under the action of the (AlCrTiZrNb)N layer template, and a coherent epitaxial interface layer is formed between the two layers, resulting in an increase in hardness. The maximum values of hardness and elastic modulus of the high-entropy (AlCrTiZrNb)N/WS2 film are 22.5 GPa and 300.6 GPa, respectively, when the WS2 layer thickness reaches 1.2 nm. As the thickness of the WS2 layer further increases, the WS2 layer cannot maintain the cubic structure and the epitaxial growth interface is destroyed, resulting in a decrease in the hardness. The friction coefficient of the (AlCrTiZrNb)N/WS2 nano-multilayered film is lower than that of the (AlCrTiZrNb)N monolithic film.
Munroe, Paul R.Abbas, MusharafKhalid, ArslanSmith, Gregory M....
14页
查看更多>>摘要：The present study investigates the splat formation behaviour of Ni particles plasma sprayed onto AISI 1008 mild steel and 316 austenitic stainless steel substrates to draw a comparative analysis of splat formation on both surfaces. A range of analytical techniques were used to analyse the surface and cross-sectional characteristics of the splats formed on both substrates. Most of the splats observed on both of the substrates were halo type splats driven by Rayleigh-Taylor instabilities. A linear relationship was identified between the size of the central core of the splats and their outer ring of debris, which was distinct for each substrate. The diffusion profile, obtained through STEM-EDS analysis, revealed a higher degree of diffusion across the interface between splat and stainless steel substrate as compared to mild steel, suggesting a better bond efficiency for stainless steel. Cross-sectional observations, together with theoretical calculations, showed evidence of substrate melting as well as the presence of metallurgical bonds for both mild steel and stainless steel substrates.
NSTL
Elsevier