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Rare earth doped up-conversion luminescent nano-materials exhibit abundant emission colors under suitable excitation condition. In this work, NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanoparticles were synthesized by co-precipitation method. The pure red emission can be realized by the designed NaYF4:Er/Ho@NaYF4 nanocrystals and the R/Gs reach 23.3 and 25 under excitations of 980 and 1550 nm lasers, respectively. The R/G declines as the power increasing with the emission color changing from red to yellow, which is due to the quick saturation of the energy levels, radiating red emissions. Meanwhile, the emission intensity of NaYbF4:Tm@NaYF4 nanocrystals increases by 58.3 folds after encasing the inert shell NaYF4 and the CIE color coordinate reaches (0.1646, 0.0602) under 980 nm laser excitation. Furthermore, broad range multicolor from blue to red and yellow up-conversion emissions is achieved by mixing NaYF4:Er/Ho@NaYF4 and NaYbF4:Tm@NaYF4 nanocrystals, which could be applied to colorful displaying, security anti-counterfeiting and information coding. [ABSTRACT FROM AUTHOR]

Studies on coal permeability at high temperatures (> 300 ℃) under the thermo–hydro–mechanical–chemical (THMC) coupling effect are few and their conclusions are divergent. Herein, the influence of different volumetric stresses (12, 24, and 36 MPa) on bituminous coal permeability is discussed. Moreover, the permeability evolution law of bituminous coal under different pore pressures (0.2–0.8 MPa) and temperatures (300 ℃–600 ℃) are studied using a self-made triaxial test machine with the THMC coupling effect. The experimental findings and micro-computed tomography (micro-CT) test results of coal samples under different temperatures in situ are reported. The obtained results show that (1) bituminous coal permeability underwent a negative logarithmic change with pore pressure (0.2–0.8 MPa) at different temperatures because of gas adsorption–expansion, gas slippage, and shear deformation. (2) Bituminous coal permeability varied with temperature in stages; this result differs from traditional research results. At 300 ℃–450 ℃, the permeability continuously decreased and slightly increased at 450 ℃–600 ℃; however, it was still lower than that at 300 ℃. The micro-CT results show consistent porosity evolution with permeability. (3) At 300 ℃–450 ℃, the permeability attenuation of bituminous coal mainly resulted from coal softening deformation. The continuous increase in the coefficient of linear thermal expansion increased the permeability decay rate. With the increasing temperature from 450 ℃ to 600 ℃, the accelerated pyrolysis of the coal sample enhanced the permeability, the coefficient of linear thermal expansion exhibited a negative correlation with temperature, and the inhibition effect of coal compression on permeability was weakened, slightly increasing the permeability at this stage. However, the continuous compression accumulation effect of stress still played a principal role, inducing low permeability. (4) Under the same temperature and pore pressure, the correlation between the permeability and volumetric stress of the coal samples decreased exponentially. Highlights: The permeability evolution of bituminous coal under high temperature and triaxial pressure was studied Bituminous coal permeability decreases with temperature at 300 ℃–450 ℃, and increases with temperature at 450 ℃–600 ℃ The microstructure evolution of bituminous coal under in situ high temperature condition was studied by in situ micro-CT scanning technology The weakening mechanism of bituminous coal under high temperature was clarified The differences with previous research results were discussed and explained [ABSTRACT FROM AUTHOR]

The ever-increasing deepwater oil and gas development in the Qiongdongnan Basin, South China Sea has initiated the need to evaluate submarine debris-flow hazard risks to seafloor infrastructures. This paper presents a case study on evaluating the debris-flow hazard risks to the planned pipeline systems in this region. We used a numerical model to perform simulations to support this quantitative evaluation. First, one relict failure interpreted across the development site was simulated. The back-analysis modeling was used to validate the applicability of the rheological parameters. Then, this model was applied to forecast the runout behaviors of future debris flows originating from the unstable upslope regions considered to be the most critical to the pipeline systems surrounding the Manifolds A and B. The model results showed that the potential debris-flow hazard risks rely on the location of structures and the selection of rheological parameters. For the Manifold B and connected pipeline systems, because of their remote distances away from unstable canyon flanks, the potential debris flows impose few risks. However, the pipeline systems around the Manifold A are exposed to significant hazard risks from future debris flows with selected rheological parameters. These results are beneficial for the design of a more resilient pipeline route in consideration of future debris-flow hazard risks. [ABSTRACT FROM AUTHOR]

Ethylene sulfate (DTD) is investigated as a novel film formation electrolyte additive for graphite anode material in lithium-ion battery. The CV results reveal that DTD is reduced prior to ethylene carbonate (EC) at the interface between graphite and electrolyte, while it cannot prevent the sustained reduction of propylene carbonate (PC) when the amount of DTD is lesser than 3 wt% in the PC-based electrolyte. XPS analyses demonstrate that the reduction products of DTD, LiSO, and ROSOLi are formed at the surface of graphite in the EC-based electrolyte, which is beneficial to lower the interfacial resistance as suggested by the EIS results. In addition, SEM images show a smoother and homogeneous surface film at the surface of graphite when DTD is incorporated into the electrolyte. Consequently, the Li/graphite half cells cycled in EC-based electrolyte containing DTD exhibit higher specific capacity and improved cycling capability than that without DTD. [ABSTRACT FROM AUTHOR]