悬浮液复合流态与煤炭分选效果关系的研究

主要对维持块煤重介质分选机中悬浮液密度相对稳定的水平—垂直复合流态进行研究。实验室试验和工业生产实践证明，与水平—上升流相比，水平—下降流的介质循环量小，有利于悬浮液密度的相对稳定和分选槽中重产物的下沉。

Flow softening behavior and microstructure evolution of Al-5Zn-2Mg aluminum alloy during dynamic recovery

The flow stress behavior and microstructure development of Al-5Zn-2Mg （7005） aluminum alloy were studied by hot compression tests at deformation temperatures between 300-500 ＆#176;C and strain rates between 0.05-50 s-1. The deformed structures of the samples were observed by optical microscopy （OM）, transmission electron microscopy （TEM） and electron backscattering diffraction （EBSD） analysis. The calculated activation energy is 147 kJ/mol, which is very close to the activation energy for lattice self-diffusion in aluminum （142 kJ/mol）. Dynamic recovery is the dominant restoration mechanism during the deformation. At high strain rate of 50 s-1, temperature rise due to deformation heating leads to a significant flow softening. Microstructure observations indicated that the remaining softening after deformation heating correction at high strain rate and the softening observed at high temperature are associated with grain coarsening induced by grain boundary migration during dynamic recovery process.

Processing map and hot deformation behavior of Ta-particle reinforced TiAl composite

The hot deformation behavior of a Ta-particle reinforced TiAl composite was studied.Ti-48Al-2Cr-2Nb-0.2 W(at.%)/20 vol.%Ta metal matrix composite was fabricated by spark plasma sintering.The deformation behavior was investigated by hot compression tests at the temperature ranging from 1050 to 1200℃ and the strain rate ranging from 1×10-3 to 1 s-1.The constitutive equation containing true strain variables was established.The values of activation energy Q under different strain degrees are between 240 and 280 kJ/mol,which are lower than that of pure TiAl.Based on dynamic material modeling,the processing maps at various strain degrees were established,and the optimized parameters for hot working are 1050-1100℃ and 0.005-0.01 s-1.The microstructural evolution during deformation was characterized,which indicated that the dynamic recrystallization plays an important role in this process.

Hot deformation and processing maps of as-sintered CNT/Al-Cu composites fabricated by flake powder metallurgy

The deformation behaviors of as-sintered CNT/Al-Cu composites were investigated by isothermal compression tests performed in the temperature range of 300-550°C and strain rate range of 0.001-10 s-1 with Gleeble 3500 thermal simulator system.Processing maps based on dynamic material model(DMM)were established at strains of 0.1-0.6,and microstructures before and after hot deformation were characterized by scanning electron microscopy(SEM),electron backscatter diffraction(EBSD)and high-resolution transmission electron microscopy(HRTEM).The results show that the strain has a significant influence on the processing maps,and the optimum processing domains are at temperatures of 375-425°C with strain rates of 0.4-10 s-1 and at 525-550°C with 0.02-10 s-1 when the strain is 0.6.An inhomogeneous distribution of large particles,as well as a high density of tangled dislocations,dislocation walls,and some sub-grains appears at low deformation temperatures and strain rates,which correspond to the instability domain.A homogeneous distribution of fine particles and dynamic recrystallization generates when the composites are deformed at 400 and 550°C under a strain rate of 10 s-1,which correspond to the stability domains.

Enhanced photocurrent and photoluminescence spectra in MoS2 under ionic liquid gating

We report substantial improvements and modulation in the photocurrent （PC） and photoluminescence （PL） spectra of monolayer MoS2 recorded under electrostatic and ionic liquid gating conditions. The photocurrent and photo- luminescence spectra show good agreement with a dominant peak at 1.85 eV. The magnitude of the photoluminescence can be increased 300% by ionic liquid gating due to the passivation of surface states and trapped charges that act as recombination centers. The photocurrent also doubles when passivated by the ionic liquid. Interestingly, a significant shift of the PL peak position is observed under electrostatic （14 meV） and ionic liquid （30 meV） gating, as a result of passivation. The ionic liquid provides significant screening without any externally applied voltage, indicating that these surface recombination centers have net charge. The acute sensitivity of monolayer MoS2 to ionic liquid gating and passivation arises because of its high surface-to-volume ratio, which makes it especially sensitive to trapped charge and surface states. These results reveal that, in order for efficient optoelectronic devices to be made from monolayer MoS2, some passivation strategy must be employed to mitigate the issues associated with surface recombination.