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Composite iron oxides are very important advanced materials. In this paper different types of iron oxides α-FeOOH, α-Fe2O3 and composite oxide NiFe2O4 were synthesized via a simple hydrothermal method at 180°C for 10 h. The phases and morphologies of the products were characterized by X-ray diffractometer and high-resolution transmission electron microscopy. The results indicated that α-FeOOH nanorods were prepared when mole concentration of NaOH solution was 3M. By increasing the concentration of NaOH to 5M and 8M, we obtained qusi-fusiform α-Fe2O3 single-crystallines and composite oxide NiFe2O4 nanocrystals, respectively. Our experiments showed that both the concentration of NaOH solution and existence of sulphate ions affect the formation of varying morphologies of the products.

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In this work, the thermal stability of annealed Ag/Nb multilayers was investigated as the individual layer thickness (h) varies from 1 nm to 100 nm. The lamellar structures remain unchanged after annealing at 500 °C for 1 h, and the hardness at all scales remains undiminished after annealing. The results show that two low energy interfaces are responsible for the superior thermal stabilities. The coherent interface is formed when h < 20 nm, and the amorphous interface is formed when h ≥ 20 nm, respectively. The evolution of interfacial structures and the process of solid state amorphization are discussed accordingly.

Resistivity is an important parameter to determine the electrical properties of semiconductor materials, which can be obtained from four-probe measurement to get the doping concentration and other important information. This paper gives an introduction of an intelligent DC four-probe meter based on Micro-Controller Unit (MCU), including the principle, the overall framework and the function of each module. The design of hardware and software of the system are described. This instrument has the advantages of miniature size, modular structure, strong anti-interference ability and low power consumption.