The effect of excitation current intensity on the mechanical properties of ZL205 A castings solidified under a traveling magnetic field was studied. The results of the experiment indicate that the excitation current intensity of the traveling magnetic field has a great influence on the mechanical properties of the ZL205 A castings. When the excitation current intensity is 15 A, the tensile strength and elongation of ZL205 A alloy castings increase 27.2% and 67.7%, respectively, compared with those of the same alloy solidified under gravity. The improvement of mechanical properties is attributed to the decrease of micro-porosity in the alloy. Under the traveling magnetic field, the feeding pressure in the alloy melt before solidification can be enhanced due to the electromagnetic force. Moreover, the melt flow induced by the traveling magnetic field can decrease the temperature gradient. The feeding resistance will be increased because the temperature gradient decrease. So traveling magnetic field has an optimum effect on feeding.
Low density ZnO nanorods are grown by modified chemical vapor deposition on silicon substrates using gold as a catalyst.We use high resolution photoiuminescence spectroscopy to gain the optical properties of these nanorods in large scale.The as-grown samples show sharp near-band-gap luminescence with a full width at half maximum of bound exciton peaks at about 300μeV,and the ratio of ultraviolet/yellow luminescence larger than 100.Highly spatial and spectral resolved scanning electron microscope-cathodoluminescence is performed to excite the ZnO nanorods in single rods or different positions of single rods with the vapour-solid grovth mechanism.The bottom of the nanorod has a 3.31-eV luminescence,which indicates that basal plane stacking faults are related to the defects that are created at the first stage of growth due to the misfit between ZnO and Si.
谢涌介万奇王涛WIEDENMANN MichaelNEUSCHL BenjaminMADEL Manfred王亚彬FENEBERG MartinTHONKE Klaus
Two medium-entropy alloys,NbZrTi and NbHfZrTi,were prepared by arc melting.Both NbZrTi and NbHfZrTi alloys are composed of simple body-centered cubic(bcc)solid solution phase and exhibit dendritic structure.After being homogenized,both NbZrTi and NbHfZrTi alloys are still composed of the single bcc solid solution phase,but the microstructure of the two alloys transforms from the dendritic structure into the polycrystalline structure.Two alloys display significantly workhardening effect during compression at room temperature and show relatively good deformation plasticity during compressive deformation at room temperature.For NbZrTi and NbHfZrTi alloys,the dynamic recrystallized grains form along the boundary during compression at the temperatures of 1073 and 1273 K.
The band alignment of a (0001)CdS/CdTe heterojunction is in situ studied by synchrotron radiation photoemission spectroscopy (SRPES).The heterojunction is formed through stepwise deposition of a CdTe film on a wurtzite (0001)CdS single crystalline substrate via molecular beam epitaxy.CdS shows an upward band bending of 0.55 eV,the valence band offset △Ev is calculated to be 0.65 e V and the conduction band offset △ Ec is 0.31 eV.The interracial band alignment is sketched to display type-Ⅰ band alignment.
Spin-polarized first-principle was performed to study the structural stability and the electronic states of Cr doped ZnS with the Cr component of 50% in zincblende(ZB), wurtzite(W) and rocksalt(RS) structures under pressure.The results show that the zincblende and wurtzite structures become unstable under low pressures of about4.68 and 9.61 GPa, respectively, but the rocksalt structure can be maintained up to an extremely high pressure of about 32.92 GPa. Both zincblende and wurtzite Zn0.5Cr0.5S display half metallic features under pressure, while rocksalt Zn0.5Cr0.5S exhibits metallic feature. The half metallic features can be ascribed to the stronger interactions between S-3p and Cr-3d states and the metallic feature is due to the higher crystal symmetry of rocksalt Zn0.5Cr0.5S. These results can provide helpful guidance for Cr doped ZnS to be used in spintronic devices.
Using tellurium as a solvent, we grew ZnT e ingots of 30 mm in diameter and 70 mm in length by a temperature gradient solution growth method. Hall tests conducted at 300 K indicated that the as-grown ZnT e exhibits p-type conductivity, with a carrier concentration of approximately 1014 cm-3, a mobility of approximately 300 cm2·V-1·s-1, and a resistivity of approximately 102 ·cm. A simple and effective method was proposed for chemical surface texturization of ZnT e using an HF:H2O2:H2O etchant. Textures with the sizes of approximately 1 μm were produced on {100}, {110}, and {111}Zn surfaces after etching. The etchant is also very promising in crystal characterization because of its strong anisotropic character and Te-phase selectivity.
