Yingying Xu

University of Science and Technology Beijing | USTB · School of Mathematics and Physics

Both α-Co(OH)2 and Co3O4 porous microspheres have been synthesized by the simple solvothermal process as well as subsequent treatment. The morphologies and structures of the as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spect...

Hexagonal Ni0.25Co0.75(OH)2 nanoplates with rough and smooth surfaces have been synthesized with various amount of CTAB by a mild wet chemical approach. The diameters of these two nanoplates are estimated to be ~150 nm and the thicknesses are ~30nm. The electrochemical properties of the hexagonal nanoplates have also been investigated by a three el...

Strong nonlinear resistance has been found in the charge ordered ferroelectric iron oxyborate (Fe2OBO3) with a high dielectric constant and giant converse magnetoelectric effect. In low temperature range the I-V nonlinearity increases quickly with decreasing temperature. Transport measurements on polycrystalline and single crystal Fe2OBO3 indicate...

In this paper, we review the preparation of Fe-group metal oxide nanostructures by the thermal oxidation method developed in our lab. By this method, we have prepared several kinds of nanostructures, including nanowires and nanoleaves. The magnetic properties of these nanostructures have also been studied. By carefully controlling the reacting time...

The samples of Y1-xSrxBa2-xLaxCu3Oy (YSBLCO) were synthesized and characterized by DC magnetization measurements and X-ray diffraction. The structures of the samples were refined by Rietveld method. Although the carrier concentration in the samples is constant at different dopant levels, the superconductivity evidently changes. We attribute decreas...

To further understand the argument about the superconductivity in PrBa2Cu3Oy, We try to change YBa2Cu3Oy to PrBa2Cu3Oy gradually, studying the detailed change during the change, and hope to find some clue to the argument. The single-phase samples of Y1-xPrxBa2Cu3Oy (x = 0, 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1.0, respectively) were synthesized and charac...

To get some information about the interaction of two totally different kinds of superconductors in a mixture, we prepared the samples of mixture of two kinds of superconductors (YBa2Cu3O7+MgB2), using normal annealing method at low temperature (400 °C ~ 600 °C). The variations of the transition temperature (Tc) and critical current (Jc) of the mixt...

By suitably pressurizing iron substrates under different conditions, the resulting α-Fe(2)O(3) nanostructures, formed by its direct thermal oxidation, can gradually change in succession from nanowires to nanoleaves and to micropillars as the pressure is increased. The inter-relation between the pressure conditions and the resulting nanostructure is...

It is found that the Co3O4 nanowires, prepared by directly oxygenating cobalt foil, can keep an antiferromagnetic order until room temperature, quite different from other Co3O4 materials. The opposite behaviors of the M(T) curves under 100 and 6500 Oe, and the irreversible magnetic contributions at room temperature are observed. Detailed structural...

By carefully controlling the reacting conditions, including atmosphere, temperature, and time, α-Fe2O3 nanoleaves have been synthesized by oxygenating pure iron. X-ray diffraction and transmission electronic microscope analyses demonstrate that the nanoleaves are single crystalline. The X-ray photoelectron spectrum, Raman spectrum, optical absorpti...

The thermal stability of α-Fe2O3 and γ-Fe2O3 nanowires was studied by post annealing the samples at different temperatures. Before and after annealing, the samples were characterized by X-ray diffraction and scanning electron microscopy. The α-Fe2O3 nanowires are stable at the temperatures up to 600°C, and the crystalline structure becomes more per...

By carefully controlling the reacting time, temperature, and humidity, we have prepared Co3O4 nanowires by heating a pure cobalt foil in atmosphere. Scanning electronic microscopy demonstrates that the nanowires have a diameter ranging from 20 to 100 nm and their typical lengths are in the range of 10−20 μm. X-ray diffraction, X-ray photoelectron s...

By carefully controlling the reaction conditions, nanowires of Fe3O4 are directly acquired from nanowires of α-Fe2O3 in a reduced atmosphere at 410–430°C. X-ray diffraction, Raman spectrum, and transmission electron microscopic analyses demonstrate that the product is single-crystalline Fe3O4. The nanowires have diameters of 40–90nm and lengths of...

The non-monotonic relationship of Tc with the number of Cu-O planes (n) per unit cell for compounds of Tl2Ba2Can-1CunO2n+3 (n=1, 2, 3, 4 and 5) is investigated from the reaction between different structural blocks. The unit cell of the Tl superconductors is treated as two blocks: the perovskite block where the Cu-O planes are located and the rock s...

The samples of Y1-xSrxBa2-xLaxCu3Oy (YSBLCO) were synthesized and characterized by DC magnetization measurements and X-ray diffraction. The structures of the samples were refined by Rietveld method. Although the carrier concentration in the samples is constant at different dopant levels, the superconductivity evidently changes. We attribute decreas...

The nanowires of hematite (alpha-Fe2O3) have been characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy. It is discovered that there are three main shapes of alpha-Fe2O3 nanowires, needle-tip, large-tip...

Some basic magnetic properties of α-Fe2O3 nanowires synthesized by oxygenating pure iron are reported. The blocking temperature of the nanowires is 120 K, where the field-cooled and zero-field-cooled magnetization curves diverge, and the hysteresis loops vary notably with temperature. No evidence for Morin transition is found in the temperature ran...

Bulk MgB2 with SiO2 nanoparticles added has been synthesized using a simple solid-state reaction route. The lattice constant in the c direction increases with additive content due to a small amount of Si being doped into the lattice of the MgB2; however, Tc is almost fixed at 37.2 K. The addition of SiO2 nanoparticles also improves the Jc–H and Hir...