Zr-Co(Cu)-Al bulk metallic glasses with optimal glass-forming ability and their compressive properties

The formation of bulk metallic glasses（BMGs） in the ternary Zr（56） Co（28-x）Al（16） and quaternary Zr（56） Co（28-x）CuxAl16（x=2, 4, 5, 6, 7, mole fraction, %） glassy alloys was investigated via the copper mold suction casting method. The main purpose of this work was to locate the optimal BMG-forming composition for the quaternary Zr Co（Cu）Al alloys and to improve the plasticity of the parent alloy. The X-ray diffractometry（XRD）, transmission electron microscopy（TEM） and differential scanning calorimetry（DSC） were used to investigate the glassy alloys structure and their glass forming ability（GFA）. In addition, the compression test, microhardness, nano-indentation and scanning electron microscopy（SEM） were utilized to discuss the possible mechanisms involved in the enhanced plasticity achievement. The highest GFA among Cu-containing alloys was found for the Zr（56） Co（22） Cu6 Al（16） alloy, which was similar to that of the base alloy. Furthermore, the plasticity of the base alloy increased significantly from 3.3% to 6% for the Zr（56） Co（22） Cu）6 Al（16） BMG. The variations in the plasticity and GFA of the alloys were discussed by considering the positive heat of mixing within Cu and Co elements.

Mechanical properties of TiO_2-hydroxyapatite nanostructured coatings on Ti-6Al-4V substrates by APS method

TiO2-hydroxyapatite （HA） nanostructured coatings were produced by atmospheric plasma spray method. The effects of starting powder composition and grain size on their mechanical properties were investigated. The microstructure and morphology were characterized by X-ray diffraction and scanning electron microscopy （SEM）. It is found that the coating with 10% HA has the best mechanical properties. Based on Rietveld refinement method, the mean grain size of the as-received powder （212 nm） extensively decreases to 66.4 nm after 20 h of high-energy ball milling. In spite of grain growth, the deposited coatings maintain their nanostructures with the mean grain size of 112 nm. SEM images show that there is a lower porosity in the coating with a higher HA content. Optical microscopy images show that uniform thickness is obtained for all the coatings.

Effect of different sol-gel synthesis processes on microstructural and morphological characteristics of hydroxyapatite-bioactive glass composite nanopowders

The aim of this work was to study the influence of the different synthesis processes on microstructural and morphological characteristics and distribution of hydroxyapatite-bioactive glass(HAp-BG)composite nanopowders obtained by sol-gel method.HAp-BG composite nanopowders with 20 wt%bioactive glass were prepared using a sol-gel method via four routes:(I)mixing the prepared HAp solution with BG solution before aging time;(II)mixing the prepared BG solution with the prepared HAp gel after gelation;(III)mixing the calcined BG nanopowders with the prepared HAp solution;and(IV)mixing the two prepared calcined nanopowders by mechanochemical activation.The prepared nanopowders were evaluated and studied by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectrometer(EDS),Fourier transform infrared(FTIR),transmission electron diffraction(TEM)and Brunauer-Emmet-Teller(BET)method to investigate the phase structure,microstructure and morphology,functional groups,and the size and distribution of nanopowders.Results indicated that morphology,crystallinity,crystallite size and specific surface area(SSA)of the powders are highly correspondent to the process and type of synthesis method.These findings suggest that the modified sol-gel derived HAp-BG composite nanopowders are expected to efficiently provide a possibility to produce a good candidate to use for fabrication of a bulk nanostructured HAp-BG composite for bone tissue engineering.