We prepared Co-doped ZnO films by the electrochemical deposition. X-ray diffraction (XRD), high resolution transmission microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), x-ray absorption near-edge structure (XANES), vibrating sample magnetometer (VSM), optical absorption, and photoluminescence (PL) measurements were carried out on the samples. The results showed Co atoms substituted Zn atoms in the ZnO lattice without the formation of the impurity phase. VSM measurements showed the ferromagnetic properties for the Co-doped ZnO samples. When the Co doping concentration increased, the band gaps were widened and the PL peak positions shifted towards the short wavelength direction.
Mn-doped ZnO were synthesized by solid state reaction and sol-gel method respectively. It was found that samples synthesized by solid state reaction containing Mn 2 O 3 and MnO 2 are a mixture of ferromagnetic and paramagnetic phases. Contrary, samples without second phases were found to be paramagnetic at room temperature. According to previous report, interface effects between Zn-rich Mn 2 O 3 and MnO 2 interfaces may be the origin of the ferromagnetic behavior observed in our samples prepared by solid reaction, so the alloy of Zn 1−x Mn x O may be paramagnetic at room temperature. Prepared by sol-gel technique, the samples without second phases in the XRD patterns are also room-temperature paramagnetic. Therefore we believe that the magnetism of Zn 1−x Mn x O is paramagnetic at room temperature.
This work demonstrats a convenient and effective approach to synthesize WSe 2 nanorods at only 600 °C in argon atmosphere after ball milling. The friction and wear properties of WSe 2 nanorods as additives in two kinds of base oil, GyT130 oil and 60N oil were systematically investigated. Compared to base oil, the friction coefficient of the base oil containing WSe 2 nanorods was obviously reduced and the wear behaviour was improved. The nanorods in the 60N base oil showed better tribological properties than that in the GYT130 oil. The friction-and-wear mechanism of the WSe 2 nanorods as lubrication additive was discussed.
The magnetic NiO/Fe19Ni81 nanostructure bilayer is deposited onto the colloidal spheres grown on a Si wafer by the self-assembly technology. The nanocap and the nanodot arrays form on the spherical surface and the Si substrate, respectively, which are confirmed by scanning electron microscopy and transmission electron microscopy measurements. Compared to the flat bilayer with the same composition deposited on the Si substrate, the exchange bias field HE from the nanocap is twice as large. The enhancement of HE in the nanocap is ascribed to the decreased thickness of the ferromagnetic layer induced by the sphere surface. The size and space of the biased caps are estimated based on the thickness variations induced by the sphere surfaces.
The [Co/CoO] 5 multilayer nanocap arrays are fabricated on the colloidal sphere arrays which are prepared on the Si substrate by the self-assembly technology. Compared to bilayer film, the H EB of multilayer film is larger than that of the bilayer film. The increase of H EB for multilayer should be ascribed to the interface increase between FM and AFM layers. In the multilayer film structure, H EB of the nanocap array is bigger than that of the flat film, which is attributed to the decrease of FM layer thickness, the decrease of grain size, and the increase of structural defects caused by curved substrate. And the typical step is observed in flat, and the step is reduced significantly in the nanocap array due to the enhancement of interfacial coupling between neighbor FM layers. For the [Co/CoO] 5 multilayer nanocap array, H EB increases first, and then decreases when CoO sublayer thickness changes. When CoO sublayer thickness is 15 nm, H EB reaches its maximum. This result may be related to the topography of nanostructure multilayer on curved substrate.
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