Four new type II organic dyes with D-π-A structure (donor-π-conjugated-acceptor) and two typical type II sensitizers based on catechol as reference dyes are synthesized and applied in dye sensitized solar cells (DSCs). The four dyes can be adsorbed on TiO 2 through hydroxyl group directly. Electron injection can occur not only through the anchoring group (hydroxyl group) but also through the electron-withdrawing group (-CN) located close to the semiconductor surface. Experimental results show that the type II sensitizers with a D-π-A system obviously outperform the typical type II sensitizers providing much higher conversion efficiency due to the strong electronic push-pull effect. Among these dyes, LS223 gives the best solar energy conversion efficiency of 3.6%, with J sc =7.3 mA•cm -2 , V oc =0.69 V, FF=0.71, the maximum IPCE value reaches 74.9%.
In this study, the nanogrinding process for single-crystal nickel was investigated using a molecular dynamics simulation. A series of simulations were conducted with different tool radii and grinding methods to explore the effects of chip morphology, friction forces, subsurface damage, and defect evolution on the nanogrinding process. The results demonstrate that the workpiece atoms at the back of the tool were affected by the forward stretching and upward elastic recovery when no chips were produced. Although the machining depth was the smallest, the normal force was the largest, and dislocation entanglement was formed. The small number of defect atoms indicates that the extent of subsurface damage was minimal. Moreover, when spherical chips were produced, a typical columnar defect was generated. The displacement vector of the chip atoms aligned with the machining direction and as the chips were removed by extrusion, the crystal structure of the chip atoms disintegrated, resulting in severe subsurface damage. By contrast, when strip chips were produced, the displacement vector of the chip atoms deviated from the substrate, dislocation blocks were formed at the initial stage of machining, and the rebound-to-depth ratio of the machined surface was the smallest.
In this study, molecular dynamics simulations were used to simulate the iterative rotational friction of nickel-based single crystals using diamond grinding balls in both the presence and absence of water. First, the friction force, depth and morphology of wear marks, wear rate, and evolution of internal defects during the friction process of nickel-based single crystals were investigated. Second, a comparative study of the frictional wear of nickel-based single crystals in both the presence and absence of water was carried out in terms of temperature, water molecule distribution, atomic displacement vector, and wear scar depth during the friction process. Finally, the formation process of irregular grinding chips under aqueous conditions was elucidated. The following phenomena were observed: As the number of rubs increased, the single rub depth of the workpiece, the wear rate, and the rate of increase in the number of defective atoms produced all decreased. A comparison of friction under aqueous and water-free conditions showed that, in the presence of water, the force exerted by the grinding ball on the workpiece was shared by the water molecules. This resulted in a decrease in the roughness of the machined surface, a reduction in the number of internally generated layer errors, a lower overall friction temperature, and a nickel matrix that was protected by water molecules. Finally, when grinding under aqueous conditions, water molecules interfered with the normal chip removal process of the grinding balls, leading to the production of irregular grinding chips.
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