Showing papers by "Xinhua Wu published in 2008"
TL;DR: In this article, the room temperature tensile properties, including Young's modulus of the composites, have been measured and their tribological properties assessed using a sliding wear test, and it has been found that the modulus, the yield and ultimate strength of Ti6Al4V are increased by the TiB and that the ductility is decreased.
73 citations
TL;DR: In this article, the transport and magnetic properties of compacted LaMnO3+? manganite nanoparticles of an average size of 18nm have been investigated in the temperature range 5?300?K.
Abstract: Transport and magnetic properties of compacted LaMnO3+? manganite nanoparticles of an average size of 18?nm have been investigated in the temperature range 5?300?K. The nanoparticles exhibit a paramagnetic-to-ferromagnetic (FM) transition at the Curie temperature TC ~ 246?K. However, the spontaneous magnetization disappears at a higher temperature of about 270?K. It was found that at low temperatures the FM core occupies about 50% of the particle volume. The temperature dependence of the resistivity shows a metal?insulator transition and a low-temperature upturn below the resistivity minimum at T ~ 50?K. The transport at low temperatures is controlled by the charging energy and spin-dependent tunnelling through grain boundaries. It has been found that the charging energy decreases monotonically with increasing magnetic field. The low temperature I?V characteristics are well described by an indirect tunnelling model while at higher temperatures both direct and resonant tunnelling dominates. The experimental features are discussed in the framework of a granular ferromagnet model.
30 citations
Patent•
30 Jan 2008
TL;DR: In this paper, a method of controlling the microstructure of a metal having at least two phases, a first phase having a lower molar volume than a second phase, was proposed.
Abstract: A method of controlling the microstructure of a metal having at least two phases, a first phase having a lower molar volume than a second phase. The metal is heated to a predetermined temperature, and a predetermined pressure is applied for a predetermined time such that the proportion of the first phase of the metal with the lower molar volume is increased and the proportion of the second phase of the metal is decreased. The predetermined temperature is the same as, or within a predetermined range of the transformation temperature of the first and second phases. The method may be used on gamma titanium aluminide alloys involving a gamma-alpha phase transformation and on beta titanium alloys which involve a beta-alpha phase transformation.
10 citations
TL;DR: In this paper, the authors discussed the return to equilibrium of quenched beta Ti alloys and of massively transformed TiAl alloys, and they showed that the addition of carbon leads to very significant refinement of the alpha, which precipitates during the aging and virtual elimination of grain boundary alpha.
Abstract: The return to equilibrium of quenched beta Ti alloys and of massively transformed TiAl alloys are discussed in this article. In the case of Ti-15-3 (Ti-15V-3Sn-3Al-3Cr), it is shown that the addition of carbon leads to very significant refinement of the alpha, which precipitates during the aging of quenched samples and to the virtual elimination of grain boundary alpha. Correspondingly, there is no enrichment of oxygen at grain boundaries during aging of the C-containing alloy but significant enrichment in the C-free samples. The precipitation of alpha 2 in annealed massively transformed cast samples of TiAl alloys is shown to lead to very significant refinement of the as-cast structure and thus to a significant improvement in properties. The cast samples were either hot isostatically pressed (“hipped”) or annealed to precipitate the alpha, and it has been shown that the pressures used in “hipping” strongly influence the microstructure and properties. This unexpected result is shown to be due to the fact that the molar volume of alpha 2 is larger than that of gamma, and that cooling within the hot isostatic press or after annealing is rapid enough to retain the different proportions of alpha formed at the high temperature.
2 citations
TL;DR: In this article, structural, magnetic and transport properties of Pr0.5Ca 0.5Mn1-Ni x O3 (x = 0, 0.04, 0.,07, 0, 1.1) series have been investigated.
Abstract: Structural, magnetic and transport properties of Pr0.5Ca0.5Mn1- x Ni x O3 (x =0, 0.04, 0.07, 0.1) series have been investigated. The substitution of Mn ions by Ni induces drastic changes in the magneto-transport properties of Pr0.5Ca0.5MnO3. The physical behavior depends drastically on O stoichiometry. For the low Ni doping x=0.04, 0.07, spin glass configuration is rather favored than ferromagnetism; while for x=0.10, the ferromagnetic phase is significantly suppressed. Pronounced irreversibility between zero-field cooled (ZFC) and field cooled (FC) magnetization and a kink in the ZFC curve observed for x=0.04 and 0.07 are indicative of spin-glass-like state. Applied hydrostatic pressure of about 10 kbar reduces the temperature of charge ordering in an x=0 sample by about 10 K indicating a pressure induced suppression of the Jahn-Teller distortions and of the electron-phonon coupling. Electron magnetic resonance (EMR) unambiguously evidences appearance of FM phase in Ni doped manganites. Temperature dependence of EMR spectra parameters allow us to speculate on the effect of magnetic inhomogeneities.
1 citations