摘要：We study the self-diffusion of adatom on Pt(100) surface by molecular dynamics. The metal is modeled by the surface embedded-atom potential. Besides the conventional concerted exchange mechanism, a new exchange mechanism in which an ad-dimer diffuses by a concerted motion of three atoms is observed. The importance is that it could become a dominant diffusion mechanism in some cases.

摘要：An empirical formula for composition demixing analysis in cathodic arc ion plating using alloy target is established based on the concepts of average charged state and relative demixing parameter. The level of composition demixing effect is presented by demixing degree of one element. For binary constituent alloy target, the composition change trend in coating is discussed and the limit of demixing degree for each element is determined. The content of one element with higher average charged state gets larger in coating than in alloy target, at meantime, the content of one element with lower average charged state gets less. For each one of the two constituents, the less the atom percent in alloy target, the larger the difference of its contents between the coating and the target. For triple constituent alloy target, the content change of one element with moderate average charged state is discussed in detail. Its content in coating getting larger or less is determined by the combination result of the contents of the other two elements in alloy target. For a given content of the element with moderate average charged state in triple alloy target, the content deviation level of that element from coating to alloy target will be not larger than that using binary alloy target containing only that element and one of the two others. According to the wanted coating composition, the composition design of alloy target is easily deduced from the formula.

摘要：The alloying design of cast hot-forging die steels was analyzed. The relationship of the life of cast hot-forging dies with the failure patterns was studied. The thermal wear resistance was believed to be the key property for the alloying design of cast hot-forging die steels. The alloying design parameters were selected and optimized for the cast hot-forging die steel with high wear resistance. The wear resistance of the optimized cast die steel was evaluated in comparison with commercial H13 steels and 3Cr2WSV steel. In the new cast hot-forging die steel, VC is predominant carbide with Cr and Mo as the main solution elements in α-Fe. It is found that the cast die steel has significantly lower wear rate than normal H13 steel and 3Cr2W8V steel, almost the same as that of high purity H13 steel. The high wear resistance of the new cast hot-forging die steel can be attributed to its reasonable alloying design and nonsensibility to the detrimental function of S and P.

摘要：Rechargeable Li-O2 batteries have attracted considerable interests because of their exceptional energy density. However, the short lifetime still remained as one of the bottle-neck obstacles for the practical application of rechargeable Li-O2 batteries. The development of efficient cathode catalyst is highly desirable to reduce the energy barrier of Li-O2 reaction and electrode failure. In this work, we report a facile strategy for the fabrication of a high-per- formance cathode catalyst for rechargeable Li-O2 batteries by the encapsulation of high content of active Fe nanorods into N-doped carbon nanotubes with high stability （denoted as Fe@NCNTs）. First-principles calculations reveal that the synergistic charge transfer and redistribution between the interface of Fe nanorods, the CNT walls and the active N dopants greatly facilitate the chemisorption and subsequent dissociation of O2 molecules into the epoxy intermediates on the carbon surface, which benefits the uniform growth of nanosized discharge products on CNT surface and thus boosts the reversibility of Li-O2 reactions. As a result, the cathode with Fe@NCNT catalyst exhibRs long cycling sta- bility with high capacities （1000 mA h g-1 for 160 cycles and 600 mA h g-t for 270 cycles）. Based on the total mass of Fe@NCNTs ＋ Li2O2, high gravimetric energy densities of 2120-2600 W h kg-~ can be achieved at the power densities of 50-795 W kg-1.

摘要：Understanding the temperature-dependent hardness of covalent materials is of fundamental scientific interest and crucial technical *** we propose a temperature-dependent hardness formula for zinc-blende structured covalent materials based on the dislocation *** results indicate that at low temperatures,the Vickers hardness is primarily modulated by Poisson’s ratio and the shear modulus,with the latter playing a dominant *** an increase in temperature,the governing mechanism for the plastic deformation switches from shuffle-set dislocation control to glide-set dislocation control,and the hardness decreases precipitously at elevated ***,the intrinsic parameter a3G is revealed for zinc-blende structured covalent materials,which represents the resistance of a material to softening at high *** temperaturedependent hardness model agrees remarkably well with the experimental data of zinc-blende structured covalent *** work not only sheds light on the physical origin of hardness,but also provides a practical guide for the design of superhard materials.

摘要：The effects of TiB_(2) and Zr on the microstructure,aging response and mechanical properties of hot-extruded Al-Zn-Mg-Cu based materials were investigated and compared by multi-scale microstructure characterization *** results showed that proper addition of TiB_(2) particles could refine grain size during solidification,promote dynamic recrystallization during extrusion,and inhibit grain growth during solution ***,Zr addition had minor influence on the grain refinement during solidification,but could effectively suppress recrystallization and grain growth compared with the Zr-free ***,the TiB_(2) addition could simultaneously enhance the aging kinetics and peak-aged hardness of the ***,Zr addition could also improve the peak-aged hardness with minor effect on the aging kinetics of the ***,the quench sensitivity,elastic modulus and tensile properties of the materials were compared and ***,the relationship between the microstructure and mechanical properties,and the strengthening mechanisms were discussed in detail.

摘要：Photoredox catalysis has become an indispensable solution for the synthesis of small organic ***,the precise construction of single-atomic active sites not only determines the catalytic performance,but also avails the understanding of structure–activity ***,we develop a facile approach to immobilize single-atom Ni sites anchored porous covalent organic framework(COF)by use of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)trianiline and 2,6-diformylpyridine(Ni SAS/TD-COF).Ni SAS/TDCOF catalyst achieves excellent catalytic performance in visible-light-driven catalytic carbon–nitrogen cross-coupling reaction between aryl bromides and amines under mild *** reaction provides amine products in excellent yields(71%–97%)with a wide range of substrates,including aryl and heteroaryl bromides with electron-deficient,electron-rich and neutral ***,Ni SAS/TD-COF could be recovered from the reaction mixture,corresponding to the negligible loss of photoredox performance after several *** work provides a promising opportunity upon rational design of single-atomic active sites on COFs and the fundamental insight of photoredox mechanism for sustainable organic transformation.

摘要：The segregation of Sn and discontinuous precipitation at grain boundaries are detrimental to the strength,ductility,and machinability of the Cu−Ni−Sn alloy.A strategy to solve the above problems is multi-component composition design by introducing strong enthalpic interaction *** this work,a series of Cu_(80)Ni_(15)Sn_(5−x)Ti_(x)(at.%)alloys were designed by cluster-plus-glue-atom model,and the effects of Ti content on the microstructure and properties of the alloys were systematically investigated using TEM and other analysis *** results demonstrate that Ti can effectively inhibit the segregation and discontinuous precipitation while promoting continuous precipitation to improve the high-temperature stability of the *** the Ti content increases,the distribution of Ti changes from uniform distribution to predominant *** hardness and conductivity of the alloy exceed those of the C72900(Cu−15Ni−8Sn(wt.%))commercial alloy and the Cu_(80)Ni_(15)Sn_(5)(at.%)reference alloy when Ti is in the solution state.