Surface Roughness Tuning at Sub-Nanometer Level by Considering the Normal Stress Field in Magnetorheological Finishing.

Although magnetorheological finishing (MRF) is being widely utilized to achieve ultra-smooth optical surfaces, the mechanisms for obtaining such extremely low roughness after the MRF process are not fully understood, especially the impact of finishing stresses. Herein we carefully investigated the relationship between the stresses and surface roughness. Normal stress shows stronger impacts on the surface roughness of fused silica (FS) when compared with the shear stress. In addition, normal stress in the polishing zone was found to be sensitive to the immersion depth of the magnetorheological (MR) fluid. Based on the above, a fine tuning of surface roughness (RMS: 0.22 nm) was obtained. This work fills gaps in understanding about the stresses that influence surface roughness during MRF.

Boosting the Photocatalytic Activity of P25 for Carbon Dioxide Reduction by using a Surface-Alkalinized Titanium Carbide MXene as Cocatalyst.

Although they are widely used as cocatalysts in promoting photocatalysis, practical application of noble metals is limited by their high cost and rarity. Development of noble-metal-free cocatalysts is thus highly demanded. Herein titanium carbide (Ti3 C2 ) MXene is shown to be a highly efficient noble-metal-free cocatalyst with commercial titania (P25) for photocatalytic CO2 reduction. Surface alkalinization of Ti3 C2 dramatically enhances the activity; the evolution rates of CO (11.74 µmol g-1 h-1 ) and CH4 (16.61 µmol g-1 h-1 ) are 3- and 277-times higher than those of bare P25, respectively. The significantly enhanced activity is attributed to the superior electrical conductivity and charge-carrier separation ability, as well as the abundant CO2 adsorption and activation sites of surface-alkalinized Ti3 C2 MXene, indicating its promise as a highly-active noble-metal-free cocatalysts for photocatalytic CO2 reduction.