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Instantaneous high temperature improved the low-temperature sintering efficiency of the un-doped MgB 2 superconductor, and the MgB 2 was rapidly synthesized at 600 °C for only 2 h. In addition to the refinement of MgO impurity particles, the sudden high temperature induced defects within the MgB 2 grains, e.g. twinning crystal, and the J c performance is therefore significantly enhanced, about 2.2 × 10 3 A·cm − 2 at 4 T for bulk sample. Differed from the two-dimensional nucleation growth mode of the MgB 2 grains in the high-temperature sintered un-doped sample, the low-temperature sintered MgB 2 grains accord with the dislocation growth mechanism, relying on the thermal-stress-triggered twinning crystal. [ABSTRACT FROM AUTHOR]

Sintering temperature plays a vital role in the evolution of phase structure and microstructure in polycrystalline FeSe 0.5 Te 0.5 bulks fabricated by the two-step sintering method, and thus significantly influences their superconducting properties. Elevated sintering temperature (600–700 °C) at second step facilitates the substitution of Te into the superconducting phase, which leads to the increased lattice distortion and thus contributes to the enhancement of superconductivity (the value of T c reaches 15.6 K). At the same time, the accelerated growth of the superconducting grains and the improved homogeneity motivated by elevated sintering temperature serve as the main reason for the sharp superconducting transition. [ABSTRACT FROM AUTHOR]

A significant enhancement of critical current density (J c) was obtained in MgB2 +3wt.% glycine samples with a large amount of MgO. The improvements in J c and in the irreversible magnetic field (H irr) are attributed to the pinning effects of high C-substitution level, nanoscale MgO, and to the even boundaries of small grains. This doping method overcomes the degradation of J c under a low field in previously reported SiC-doped samples. Moreover, the formation of MgO was demonstrated to be the result of the reactions between Mg, CO2 and O2. [ABSTRACT FROM AUTHOR]

Lamellar MgB2 grains were synthesized by Cu-activated sintering at low temperature. We found that the Mg–Cu liquid can provide a constant liquid environment and the formation of lamellar MgB2 grains is attributed to the two-dimensional nucleation and growth mechanism in the liquid–solid interface. According to the analysis on the temperature dependence of resistivity, these lamellar MgB2 grains possess much better grain connectivity than the typical morphology of MgB2 grains synthesized by the traditional solid-state sintering. [Copyright &y& Elsevier]

Multi-doped MgB2 superconductors with excellent critical current density (Jc ) were rapidly synthesized by low-temperature activated sintering with Cu addition as the activator and nano SiC addition as the carbon-based chemical. Combined with microstructure observation and flux pinning force analysis, it is found that the enhancement of Jc (especially at low field) was mainly attributed to the higher density, lower crystallinity and the concentration of Cu activator around the sintered voids. [Copyright &y& Elsevier]

In this work, 316L/CuCrZr functionally graded materials were prepared by laser powder bed fusion. Not only the strong bonding of 316L and CuCrZr was achieved, but more importantly, the grain-size gradients and heterogeneous microstructures were introduced into the samples. The gradient microstructure was characterized by ultrafine equiaxed grains sandwiched between micron-scale columnar grains. The dual-scale heterogeneous microstructure was composed of the BCC α-Fe and FCC ε-Cu phases. This grain size gradient and heterogeneous microstructure ensure that the samples possess high shear and tensile strength. The formation mechanisms of the grain-size gradients and heterogeneous microstructures of the samples were further discussed. The proposed strategy that functionally graded materials with grain size gradients and heterostructures can be fabricated by additive manufacturing may open up a new avenue for materials design. [Display omitted] [ABSTRACT FROM AUTHOR]