Two quinary high-entropy alloys （HEAs） with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entr...Two quinary high-entropy alloys （HEAs） with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning cMorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face- centered cubic high-entropy phase plus a minor interdendritic （Cu） phase and display a lower entropy of fasion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubie high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are signitieantly larger than those of the latter At-doped M1oy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860-912 K.展开更多
We report the electrostatic levitation of various kinds of seeds and flower buds.Coral berry and pepper near a spherical shape show a stable levitation state.The prolate ellipsoid soybeau and flower buds are always “...We report the electrostatic levitation of various kinds of seeds and flower buds.Coral berry and pepper near a spherical shape show a stable levitation state.The prolate ellipsoid soybeau and flower buds are always “standing” in the free space with satisfactory levitation stabiiity.For the irregular mushroom and wheat grain,the levitation state is characterized as a “top-heavy” posture.These special stable equilibrium states are proved by the analysis of surface charge distribution.The obtained saturation polarization charge of samples presents a good accordance with experimental data.The levitation ability is weighed by thefactor m(ε_(r) + 2) / (εrD^(2)).展开更多
基金Supported by the National Natural Science Foundation of China under Grant Nos 51571163,51371150,51271150 and 51327901
文摘Two quinary high-entropy alloys （HEAs） with equiatomic concentrations formed by doping either Cu or A1 elements into the quaternary NiFeCoCr alloy are produced by arc melting and spray casting techniques. Their entropy of fusion, thermal expansion coefficient and thermal diffusivity are experimentally investigated with differential scanning cMorimetry, dilatometry and laser flash methods. The NiFeCoCrCu HEAs contain a face- centered cubic high-entropy phase plus a minor interdendritic （Cu） phase and display a lower entropy of fasion and the Vickers hardness. The NiFeCoCrAl HEAs consist of two body-centered cubie high-entropy phases with coarse dendritic structures and show higher entropy of fusion and the Vickers hardness. Both the thermal expansion coefficient and the thermal diffusivity of the former Cu-doped alloy are signitieantly larger than those of the latter At-doped M1oy. Although the temperature dependence of thermal diffusivity is similar for both HEAs, it is peculiar that the thermal expansion curve of the NiFeCoCrAl alloy exhibits an inflexion at temperatures of 860-912 K.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50121101,50971103 and 50971105the Program for New Century Excellent Talents.
文摘We report the electrostatic levitation of various kinds of seeds and flower buds.Coral berry and pepper near a spherical shape show a stable levitation state.The prolate ellipsoid soybeau and flower buds are always “standing” in the free space with satisfactory levitation stabiiity.For the irregular mushroom and wheat grain,the levitation state is characterized as a “top-heavy” posture.These special stable equilibrium states are proved by the analysis of surface charge distribution.The obtained saturation polarization charge of samples presents a good accordance with experimental data.The levitation ability is weighed by thefactor m(ε_(r) + 2) / (εrD^(2)).
