[en] The recently observed variations of the transition temperature (T sub c) with oxygen content in the Bi based (2212) and (2223) superconductors are analyzed in terms of p+, the hole concentration per CuO2 sheet. This analysis shows that in this system, T sub c increases with p+ initially, reaching maxima at p+ = 0.2 approx. 0.3, followed by monotonic decrease of T sub c with p+. The forms of these variations are similar to those observed in the La(2-x)Sr(x)CuO4 and YBa2Cu3Oy systems, suggesting that p+ may be an important variable governing superconductivity in the cuprate superconductors

[en] Ternary lead-free solder alloys Sn-Ag-Cu were considered as the potential alternatives to lead-tin alloys comparing with other solders. In this paper, microstructure and mechanical properties of Sn-2.5Ag-0.7Cu, Sn-3.5Ag-0.7Cu, Sn-3.5Ag-0.7Cu-0.1RE, and Sn-3.5Ag-0.7Cu-0.25RE alloys were researched. Coarse β-Sn grains were formed in Sn-2.5Ag-0.7Cu and Sn-3.5Ag-0.7Cu alloys and bulky Ag₃Sn intermetallics were found in Sn-3.5Ag-0.7Cu alloy. With the addition of trace rare earth (RE) elements the coarse β-Sn grains were refrained, at the same time, Cu₆Sn₅ and Ag₃Sn intermetallics were finer according to the adsorption affection of the active rare earth elements. Due to the fine and uniform microstructure, the tensile strength and elongation were improved. In addition, the wetting properties were also enhanced. All these results indicated that adding trace rare earth elements was an efficient way to develop new solders

No abstract available

[en] Short communications only

[en] A high-efficiency diffusion-multiple approach was employed to determine the phase diagram of the Nb-Cr-Si ternary system which is critical for the design of niobium silicide-based in situ composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. The formation of the Nb(Cr,Si)₂ Laves phase is beneficial to the high oxidation resistance of the composites and the Nb-Cr-Si system serves as the base for understanding the Laves phase formation. The results clearly demonstrate the applicability of the diffusion-multiple approach in determining such complex phase diagrams as Nb-Cr-Si which contains 14 phases. Two isothermal sections at 1000 and 1150 deg. C were constructed from the results obtained from diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Three ternary compounds, CrNbSi, (Cr,Nb)₆Si₅ and (Cr,Nb)₁₁Si₈, were observed at both temperatures, and the C14 Laves phase of the Cr-Nb binary system was stabilized by Si to lower temperatures

[en] A high-efficiency diffusion-multiple approach was employed to map the phase diagram of the Nb-Ti-Si ternary system, which is critical for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. Titanium is one of the most important elements for oxidation resistance and fracture toughness enhancement. Three isothermal sections of Nb-Ti-Si at 1000, 1150 and 1200 deg. C were constructed from the results obtained from diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and electron backscatter diffraction (EBSD). Extremely high solubility of Nb in Ti₅Si₄ (up to ∼46 at.% Nb at 1200 deg. C, substituting for Ti) was observed

[en] A high-efficiency diffusion-multiple approach was employed to map the phase diagram of the Nb-Al-Si ternary system which is very valuable for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. Aluminum is an alloying element for these composites, thus the Nb-Al-Si phase diagram, especially solubility of Al in Nb₅Si₃, is important information for the composite design. An isothermal section at 1000 deg. C was constructed from the results obtained from a diffusion multiple using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). A ternary phase Nb₃Si₅Al₂ was observed. The solubility data of Al in αNb₅Si₃ and NbSi₂ as well as Si solubility in Nb₃Al, Nb₂Al and NbAl₃ were obtained. The new isothermal section helps to judge the reliability of the existing literature results and to add new data to the Nb-Al-Si phase equilibria

[en] The equation of state and structural changes of YAlO₃ perovskite, a GdFeO₃-type perovskite with Pbnm symmetry, have been investigated to 8.5 GPa in a diamond-anvil cell at room temperature using single-crystal X-ray diffraction. A fit of a third-order Birch-Murnaghan equation of state to the P-V data yields values of K_T0=192(2) GPa and K'₀=7.3(4), with compressional moduli of the axes, K_a0=220(7) GPa, K_b0=157(3) GPa and K_c0=212(2) GPa, and their pressure derivatives, K'_a0=12(2), K'_b0=4.4(6)(6) and K'_c0=8.7(4). The evolution of the structure with pressure shows that compression of the YO12 site is strongly anisotropic with the four longest Y-O separations more compressible than the eight shorter Y-O bond lengths. Consequently the distortion of the YO12 site decreases with increasing pressure. In contrast, the AlO6 site undergoes nearly isotropic compression and is more compressible than the YO12 site. The interoctahedral angles, angle Al-O1-Al and angle Al-O2-Al, show a significant increase with pressure, reflected in the movement of O1 along <100>. The structure of YAlO₃ perovskite therefore becomes less distorted with increasing pressure, in contrast with other Pbnm perovskites such as CaSnO₃

[en] The phenotypic plasticity of Sagittaria graminea to nitrogen and phosphate including morphology, growth and biomass allocation, and the impact of the biological invasion on biodiversity and grassland agroecosystem were investigated. The nitrogen was from NH4NO3 and the concentration was 0g (control), 0.4g/kg (LN),0.6g/kg (MN) and 0.8g/kg (HN) air-dried soil; the phosphate was from NaH2PO4 and the concentration was 0g (control), 0.2g/kg (LP), 0.4g/kg (MP) and 0.6g/kg (HP) air-dried soil. According to the characteristics of the flowering, seedling and clonal reproduction of the Sagittaria graminea, it was harvested in the blooming period, and the height of each plant, the number of leaves, and the female and male flowers were counted. The results showed that Sagittaria graminea had plasticity and adaptability to different nutriention. With the increase of nitrogen, the root biomass was decreased and total biomass, leaf biomass, flower biomass, relative growth rate, net assimilation rate, leaf number and plant height was increased; with the increase of phosphate, total biomass and leaf biomass increased and plant height, petiole biomass, root biomass, root/shoot, relative growth rate and net assimilation rate were not changed. (author)

[en] If the distribution of pair plasmas is a bi-Maxwellian with T_{perpendicular}/T_parallel > 1 and if this anisotropy is sufficiently large, large-amplitude Alfven waves with arbitrary polarizations can arise. Simulation results show that an amplitude of the excited Alfven waves increases as the temperature anisotropy increases. Nonlinear evolution of the large-amplitude Alfven waves causes magnetic trapping, which could provide the saturation mechanism. After saturation, the initial bi-Maxwellian distribution of particles still remains and a residual temperature anisotropy persists long, at least on the time scale of simulations. (author)