In-situ formation of Ag nanoparticles in the MAO coating during the processing of cp-Ti

Silver nanoparticle (Ag-NP) containing antibacterial micro-arc oxidation (MAO) coatings have already been synthesized over titanium-based materials via the MAO process employed in silver acetate (AgC2H3O2) containing electrolyte. However, the way of incorporation and in-situ formation of Ag-NPs within the MAO coating have not been documented yet. Present work was initiated to reveal the mechanism of Ag-NP formation within the MAO coatings. Thus, the structure of the MAO coating fabricated on commercial purity titanium in the AgC2H3O2-containing electrolyte was investigated by electron microscopy techniques. To this end, the cross-sectional high-resolution electron microscopy studies were carried out on lamella cut out with the focused ion beam technique, and these investigations were backed by X-ray photoelectron spectroscopy measurements of chemical composition on the surface of the MAO coating. These studies revealed that Ag is dispersed in the form of nanoparticles throughout the coating and that a higher density was confirmed closer to the micro-pores

Mechanical properties of Al-60 pct SiCp composites alloyed with Mg

In the present work, the effect of an Mg addition on the mechanical properties of the Al-60 vol pct SiCp composites were investigated by uniaxial compression, three-point bending, impact and wear tests (composite-metal and composite-abrasive types). The composites were produced by the pressure-infiltration technique. The composition of the Al matrix was varied between 0 and 8 pct Mg. The mean diameter of the SiC particles was 23 µm. Upon addition of Mg, Mg 2 Si precipitated in the matrix and the amount of the porosity dramatically decreased. Mg-alloyed-matrix composites exhibited higher strength, lower toughness, and higher wear resistance than pure-Al-matrix composites. During composite-metal wear testing, wear progressed in two sequential periods (running-in and steady state). Weight loss during wear testing decreased with increasing Mg content of the matrix. The degree of improvement of abrasive resistance depended on the abrasive-grain size. Above 200 °C, the composite-abrasive wear resistance decreased with increasing test temperature for all materials

Mechanical design, analysis, and laboratory testing of a dental implant with axial flexibility similar to natural tooth with periodontal ligament

At the interface between the jawbone and the roots of natural teeth, a thin, elastic, shock-absorbing tissue, called the periodontal ligament, forms a cushion which provides certain flexibility under mechanical loading. The dental restorations supported by implants, however, involve comparatively rigid connections to the jawbone. This causes overloading of the implant while bearing functional loading together with neighboring natural teeth, which leads to high stresses within the implant system and in the jawbone. A dental implant, with resilient components in the upper structure (abutment) in order to mimic the mechanical behavior of the periodontal ligament in the axial direction, was designed, analyzed in silico, and produced for mechanical testing. The aims of the design were avoiding high levels of stress, loosening of the abutment connection screw, and soft tissue irritations. The finite element analysis of the designed implant revealed that the elastic abutment yielded a similar axial mobility with the natural tooth while keeping stress in the implant at safe levels. The in vitro mechanical testing of the prototype resulted in similar axial mobility predicted by the analysis and as that of a typical natural tooth. The abutment screw did not loosen under repeated loading and there was no static or fatigue failure