Static and dynamic evolution of CO adsorption onγ-U(100)surface with different levels of Mo doping using DFT and AIMD calculations

Alloys of uranium and molybdenum are considered as the future of nuclear fuel and defense materials.However,surface corrosion is a fundamental problem in practical applications and storage.In this study,the static and dynamic evolution of carbon monoxide(CO)adsorption and dissociation onγ-U(100)surface with different Mo doping levels was investigated based on density functional theory and ab initio molecular dynamics.During the static calculation phase,parameters,such as adsorption energy,configuration,and Bader charge,were evaluated at all adsorption sites.Furthermore,the time-dependent behavior of CO molecule adsorption were investigated at the most favorable sites.The minimum energy paths for CO molecu-lar dissociation and atom migration were investigated using the transition state search method.The results demonstrated that the CO on the uranium surface mainly manifests as chemical adsorption before dissociation of the CO molecule.The CO molecule exhibited a tendency to rotate and tilt upright adsorption.However,it is difficult for CO adsorption on the surface in one of the configurations with CO molecule in vertical direction but oxygen(O)is closer to the surface.Bader charge illustrates that the charge transfers from slab atoms to the 2π*antibonding orbital of CO molecule and particularly occurs in carbon(C)atoms.The time is less than 100 fs for the adsorptions that forms embryos with tilt upright in dynamics evolution.The density of states elucidates that the overlapping hybridization of C and O 2p orbitals is mainly formed via the d orbitals of uranium and molybdenum(Mo)atoms in the dissociation and re-adsorption of CO molecule.In conclusion,Mo doping of the surface can decelerate the adsorption and dissociation of CO molecules.A Mo-doped surface,created through ion injection,enhanced the resistance to uranium-induced surface corrosion.

First-principles study of co-adsorption behavior of O_(2)and CO_(2)molecules onδ-Pu(100)surface

First principles calculation is performed to study the co-adsorption behaviors of O_(2)and CO_(2)onδ-Pu(100)surface by using a slab model within the framework of density functional theory(DFT).The results demonstrate that the most favorable co-adsorption configurations are T_(v)-C_(4)O_(7)and T_(p1)-C_(2)O_(8),with adsorption energy of-17.296 e V and-23.131 e V for CO_(2)-based and O_(2)-based system,respectively.The C and O atoms mainly interact with the Pu surface atoms.Furthermore,the chemical bonding between C/O and Pu atom is mainly of ionic state,and the reaction mechanism is that C 2 s,C 2 p,O 2s,and O 2p orbitals overlap and hybridize with Pu 6 p,Pu 6 d,and Pu 5 f orbital,resulting in the occurrence of new band structure.The adsorption and dissociation of CO_(2)molecule are obviously promoted by preferentially occupying adsorbed O atoms,therefore,a potential CO_(2)protection mechanism for plutonium-based materials is that in CO_(2)molecule there occurs complete dissociation of CO_(2)→C+O+O,then the dissociated C atom combines with O atom from O_(2)dissociation and produces CO,which will inhibit the O_(2)from further oxidizing Pu surface,and slow down the corrosion rate of plutoniumbased materials.

Oxidation induced ductility enhancement of Zr based metallic glass ribbons in vicinity of glass transition temperature

Zr-based metallic glasses(MGs)possess a wide supercooled liquid region,which gives a wide processing window for superplastic forming to make microdevices with demanding size accuracy and surface finishing.The existence of oxygen may have an influence on the thermoplastic deformation process.Therefore,the effect of oxidation on the mechanical behavior of the MGs in the vicinity of glass transition temperature is of great significance for practical forming of MG components.In the present study,the effect of oxidation on tensile properties of Zr50Cu40Al10 metallic glass was investigated.The tested samples were characterized by XRD and SEM analysis.For the samples tested in air,the strength decreases 187 MPa,61 MPa and 59 MPa and the ductility increases 0.31,0.36,and 0.77 at 420℃,430℃,and 440℃,respectively,compared with those tested in flowing argon.ZrO_(2) preferentially formed during the tensile testing at 420℃,and both ZrO_(2) and Al_(2)O_(3) oxides formed at 430℃.The dilution of Zr elements in the remaining amorphous matrix caused by preferential oxidation on the surface layer attributes to the decrease in strength and enhancement in ductility of the Zr_(50)Cu_(40)Al_(10) metallic glasses.

Effect of short-time low-temperature austenitizing on microstructure and mechanical properties of DT300 ultra-high strength steel fabricated by laser powder bed fusion

To address the inhomogeneous microstructure and improve the mechanical properties of DT300 ultra-high strength steel specimens fabricated by laser powder bed fusion,different post-heat treatment schedules are performed.With the increase in austenitizing temperature and time,the migration rate of austenite grain boundaries continuously increases with the dissolution of nano-carbides,and the formation of nano-oxides and twin martensite is also inhibited accordingly.The rapid growth in the size of prior austenite grains and martensite laths,as well as the decrease in the content of nano-oxides and twin martensite,led to a rapid decrease in the strength(yield strength and ultimate tensile strength)from HT2 to HTF specimens.The HT1 specimens(austenitizing at 830℃for 30 min,then oil quenching and tempering at 300℃for 120 min and finally air cooling)display excellent mechanical properties of yield strength of 1572 MPa,ultimate tensile strength of 1847 MPa,elongation of 9.84%,and fracture toughness of 106 MPa m^(1/2),which are counterparts to those of conventional DT300 steel forgings after heat treatment.

柔性钙钛矿发光二极管:进展,挑战与展望

金属卤化物钙钛矿具有优异的光电性能和良好的延展性,是一种很有前途的适合于柔性光电子器件的材料,并且可以集成到便携式和可穿戴式的显示设备中,在下一代显示和照明方面展现出巨大的潜力.目前,柔性钙钛矿发光二极管领域已经取得了令人鼓舞的进展,最大外量子效率已经超过28%.在此,我们总结了近年来在柔性钙钛矿发光二极管领域取得的主要突破,旨在提供一个全面的回顾,以促进柔性钙钛矿发光二极管的进一步发展.此外,我们还讨论了阻碍柔性钙钛矿发光二极管器件性能和商业化的主要挑战.最后,我们对柔性钙钛矿发光二极管的未来机遇和应用前景进行了展望和总结.

线粒体RNAm^(3)C修饰酶METTL8的活力依赖于亚型特异的N-末端延伸结构且METTL8能修饰多种非天然底物tRNA

定位于线粒体的METTL8-Iso1和分布在核仁的METTL8-Iso4均为甲基转移酶基因METTL8通过mRNA选择性剪接产生的亚型,它们的区别仅为前者有N-末端延伸结构.METTL8-Iso1的功能是催化产生线粒体tRNATh和tRNASe(UCN)第32位3-甲基胞苷(mC32)修饰.METTL8-Iso4是否也具有tRNAmC32修饰活性以及N-末端延伸在线粒体tRNAmC32修饰中的作用尚不清楚。我们发现,N-末端延伸上有几个保守的关键氨基酸残基,而METTL8-Iso4由于缺少N-未端延伸而不具备tRNAmC32修饰活力.体外实验和体内实验的结果表明,甲基转移酶METTL2A和Trm140上对应的这些关键位点也是各自对底物tRNAmC32修饰活性所必需的。在跨细胞区室与跨物种的酶对tRNA体外催化的交又实验中,我们意外地发现METTL8-Iso1也能催化几种人细胞质tRNA甚至大肠杆菌tRNA的mC32修饰。此外,mC32修饰并不影响tRNA的N-苏氨酰氨基甲酰腺苷(t'A)修饰和氨基酰化活力.除了METTL8与人线粒体丝氨酰-tRNA合成酶(SARS2)的相互作用外,我们还进一步发现了人线粒体苏氨酰-tRNA合成酶(TARS2)与METTL8-IsoI之间的相互作用。体外实验中,METTL8-Iso1显著促进了SARS2和TARS2的氨酰化活力,表明线粒体IRNA的修饰和氨基酰化之间存在功能联系:总之,该结果加深了对线粒体mC32修饰生物发生机制的理解,并提供了一种制备仅含mC32修饰的人细胞质或细菌tRNA的方法,有助于未来研究mC32修饰对tRNA结构和功能的影响。