Structural synergy of NanoAl2O3/NanoAl composites with high thermomechanical properties and ductility

Achieving a combination of high strength and ductility in metal-based composites is still a difficult task, and it is especially challenging in a wide temperature range. Here, nanoAl2O3/nanoAl composites with high tensile and compressive strength and excellent ductility at 25 and 500 °C were obtained using Al and Al2O3 nanopowders via a combination of high-energy ball milling (HEBM) and spark plasma sintering (SPS). Being about three times lighter than conventional high-strength steel (with a density of 2.7 g/cm3 vs. that of 7.8 g/cm3 for steel), the nanoAl2O3/nanoAl materials demonstrated tensile strength and elongation before failure comparable with those of steel. The nanoAl2O3/nanoAl composites were strengthened with two types of Al2O3 NPs, in situ formed, and introduced into the powder mixture. The resulting materials had a bimodal microstructure consisting of Al with micron and submicron grains surrounded by an Al/Al2O3 framework whose structural components were all in the size range of 20–50 nm. Among the studied compositions (0, 1, 2, 3, 4, 5, 10, and 20 wt.% of Al2O3), the Al-3%Al2O3 material showed the best thermomechanical properties, such as a tensile strength of 512 MPa and 280 MPa and a compressive strength of 489 MPa and 344 MPa at 25 and 500 °C, respectively, with an elongation to failure of 15–18%. These results show the promise of nanoAl2O3/nanoAl composites for use as small items in the automotive and aviation industries.</p

Synthesis of Iron Oxide Nanoclusters by Thermal Decomposition

Herein, we report a novel one-step solvothermal synthesis of magnetite nanoclusters (MNCs). In this report, we discuss the synthesis, structure, and properties of MNCs and contrast enhancement in <i>T</i>₂-weighted MR images using magnetite nanoclusters. The effect of different organic acids, used as surfactants, on the size and shape of MNCs was investigated. The structure and properties of samples were determined by magnetic measurements, TGA, TEM, HRTEM, XRD, FTIR, and MRI. Magnetic measurements show that obtained MNCs have relatively high saturation magnetization values (65.1–81.5 emu/g) and dependence of the coercive force on the average size of MNCs was established. MNCs were transferred into an aqueous medium by Pluronic F-127, and <i>T</i>₂-relaxivity values were determined. <i>T</i>₂-Weighted MR phantom images clearly demonstrated that such magnetite nanoclusters can be used as contrast agents for MRI