We have studied how different growth conditions, namely, oxygen flow rate, annealing temperature and annealing time affect the diameter, aspect ratio and number density of CuO nanorods using scanning and transmission electron microscopy. CuO nanorods are synthesized by thermal annealing of thin copper foil. It is observed that while the diameter and number density of nanorods depend critically on the oxygen flow rate and annealing temperature, the aspect ratio and dispersion in diameter of nanorods can mostly be improved by thermal annealing for extended time periods. The growth mechanism of the nanorods is inferred from the evolution of observed microstructural changes. It is proposed that the growth of nanorods takes place from triangular shaped pyramids due to the relaxation of stress accumulated in oxide film during the process of oxidation and annealing.

We present results of detailed ac susceptibility, magnetization and specific heat measurements in Heusler alloys Ni50Mn34In16 and Ni50Mn34Sn16. These alloys undergo a paramagnetic to ferromagnetic transition around 305 K, which is followed by a martensitic transition in the temperature regime around 220 K. Inside the martensite phase both the alloys show signatures of field-induced transition from martensite to austenite phase. Both field- and temperature-induced martensite–austenite transitions are relatively sharp in Ni50Mn34In16. We estimate the isothermal magnetic entropy change and adiabatic temperature change across the various phase transitions in these alloys and investigate the possible influence of these transitions on the estimated magnetocaloric effect. The sharp martensitic transition in Ni50Mn34In16 gives rise to a comparatively large inverse magnetocaloric effect across this transition. On the other hand the magnitudes of the conventional magnetocaloric effect associated with the paramagnetic to ferromagnetic transition are quite comparable in these alloys.

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Hematite (α-Fe2O3) nanowires have been synthesized on a large surface area by thermal oxidation of iron foil in an ozone-rich environment. The effects of annealing time, temperature, and oxidizing environment on the growth of nanowires have been systematically studied. The samples were characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). It was found that annealing in ozone-rich environment for 2–4 h at 700 °C yielded the best results in terms of number density and diameter of nanowires. The average diameter of the nanowires was found to be 85 nm. It was found that nanowires are bicrystal in nature with a length around 4 μm, which grows uniquely along the [110] direction.

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