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In this paper, we reported the synthesis of NiO/Ni bilayer nanotubes by electrodeposition and thermal oxidation using anodic aluminum oxide templates. The morphology, structure, chemical composition and magnetic properties, especially magnetic exchange bias induced by subsequent magnetic field cooling, in this one-dimensional antiferromagnetic/ferromagnetic hybrid system were investigated. It was found that the effect of the annealing temperature, which mainly dominated the thickness of the NiO layer, and the annealing time, which mainly dominated the grain size of the NiO, on the exchange bias field showed competitive relationship. The optimized exchange bias field was achieved by the combination of the shorter annealing time and higher annealing temperature. [ABSTRACT FROM AUTHOR]

Abstract: The dynamics and mechanism of columnar grain growth of pure iron with small equiaxed grains were experimentally investigated under directional annealing. The results prove the existence of both a lower- and an upper limit of the withdrawing velocity for columnar grain growth. Importantly, there is an optimum withdrawing velocity at which the largest aspect ratio of columnar grains can be obtained. A kinetic approach is suggested to describe the growth of the columnar grains. The aspect ratio of the columnar grains can be successfully predicted by this approach. The mechanism of the columnar grain growth essentially can be described as selective growth or competitive migration of the grain boundaries. As a result of selective growth, the boundaries between the columnar grains abound in low-energy boundaries. Small island-like grains inside the columnars grain can be left over due to the low mobility of their small-angle boundaries or twin boundaries. [Copyright &y& Elsevier]

Abstract: Microstructural evolution during the directional annealing of the cold-rolled pure iron has been investigated. Columnar grains with the largest aspect ratio of 23.6 were produced in the specimen cold-rolled for 70% of thickness reduction at the hot zone temperature (HZT) of 850°C and a temperature gradient (TG) of 200°C/cm with an optimum drawing velocity of 5μm/s. It was found that the columnar grain structure was developed due to abnormal grain growth. There is a critical coarsening temperature, below which the secondary recrystallization does not occur during the annealing; consequently no columnar grain structure can be produced. No obvious evidence shows that the grain size after primary recrystallization has an influence on the microstructural evolution. Due to the strong crystallographic texture of the small grains ahead of the hot zone, the columnar grains have small aspect ratios. Most of the boundaries of the columnar grain are high angle coincidence site lattice (CSL) grain boundaries. The grains with twin or low angle grain boundaries are apt to form island grains in the columnar structure. [Copyright &y& Elsevier]

In this paper, the effect of annealing on the bipolar resistive switching characteristics of a Ti/Si 3 N 4 /n-GaN metal-insulator-semiconductor (MIS) structure memristor is demonstrated. The results show that the stability and repeatability of the bipolar resistive switching are greatly improved in annealed Ti/Si 3 N 4 /n-GaN MIS devices. The mechanism involved is revealed by both conductive force microscopy (CFM) and x-ray photoelectron spectroscopy (XPS). It is confirmed to in-situ local Ti doping in Si 3 N 4 by thermal annealing and can be ascribed to the local Ti dopants in the Si 3 N 4 bonding the N atoms at positive bias by electro-reductive process that benefits to form stable nanoscale Si filaments. On the contrary, the Si filaments rupture by recombining with N atoms near the n-GaN side at negative bias. The proposed device is apt to integrate with a GaN-based high electron mobility transistor (HEMT) to structure a one-transistor-one-resistor (1T1R) nonvolatile memory cell, which is expected to develop the application of the nitride semiconductors in data storage in addition to the applications in light-emitting diodes, laser diodes, power devices, and photodetectors. [ABSTRACT FROM AUTHOR]

Abstract: The evolution of precipitates in a Fe–2.5 Cu–1.5 Mn–4.0 Ni–1.0 Al multicomponent ferritic alloy during annealing at 500°C was systematically investigated by aberration-corrected scanning transmission electron microscopy. The atomic-scale structure and chemistry characterization reveal that primary precipitates with enriched Cu, Ni, Mn and Al originate from continuous growth of B2 ordered domains in the as-quenched alloy. The formation of a Cu-rich body-centered cubic (bcc) phase takes place by the decomposition of the B2 ordered primary phase, which forms a Cu-rich bcc core and ordered B2-Ni(Al,Mn) shell. The B2 shells serve as a buffer layer to moderate the coherent strain and to prohibit the inter-diffusion between the Cu-rich precipitates and bcc-Fe matrix, giving rise to a low coarsening rate of the precipitates. The Cu-rich precipitates experience a structural transformation from bcc to 9R at a critical size of ∼6nm during long time annealing, corresponding to obvious coarsening of the precipitates and dramatic loss in hardness of the alloy. [Copyright &y& Elsevier]