Formation of low-temperature deformation-induced segregations of nickel in Fe–Ni-based austenitic alloys

ABSTRACT

The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti.     

Facet-dependent antibacterial activity of Au nanocrystals

Engineered nanomaterials have attracted significantly attention as one of the most promising antimicrobial agents for against multidrug resistant infections. The toxicological responses of nanomaterials are closely related to their physicochemical properties, and establishment of a structure-activity relationship for nanomaterials at the nano-bio interface is of great significance for deep understanding antibacterial toxicity mechanisms of nanomaterials and designing safer antibacterial nanomaterials. In this study, the antibacterial behaviors of well-defined crystallographic facets of a series of Au nanocrystals, including {100}-facet cubes, {110}-facet rhombic dodecahedra, {111}-facet octahedra, {221}-facet trisoctahedra and {720}-facet concave cubes, was investigated, using the model bacteria Staphylococcus aureus. We find that Au nanocrystals display substantial facet-dependent antibacterial activities. The low-index facets of cubes, octahedra, and rhombic dodecahedra show considerable antibacterial activity, whereas the high-index facets of trisoctahedra and concave cubes remained inert under biological conditions. This result is in stark contrast to the previous paradigm that the high-index facets were considered to have higher bioactivity as compared with low-index facets. The antibacterial mechanism studies have shown that the facet-dependent antibacterial behaviors of Au nanocrystals are mainly caused by differential bacterial membrane damage as well as inhibition of cellular enzymatic activity and energy metabolism. The faceted Au nanocrystals are unique in that they do not induce generation of reactive oxygen species, as validated for most antibiotics and antimicrobial nanostructures. Our findings may provide a deeper understanding of facet-dependent toxicological responses and suggest the complexities of the nanomaterial-cell interactions, shedding some light on the development of high performance Au nanomaterials-based antibacterial therapeutics.     

93W合金有关力学参量的综合选评

 对93W合金材料进行了超声测量实验，并结合原有的超声测量结果进行了分析比较，提出了可以直接用冲击波速度关系式的三个系数c₀ 、λ和λ′来对钨合金的有关力学参量，如G₀、K₀、G₀′、K₀′等进行综合选评的方法。得到了一组对93W合金较为合理的力学参量推荐值。     

Chronoamperometric studies in an ammonia citrate electrolyte for the deposition of a nickel-molybdenum alloy

Dependences of the current and the chemical composition of cathodic deposits on the electrolysis time are studied in an ammonia-citrate electrolyte for the deposition of a nickel-molybdenum alloy in potentiostatic conditions. At potentials less negative than ?0.93 V, no nickel-molybdenum alloy deposition occurs and in the course of electrolysis there is observed a decrease in the current, which is connected with the blocking of the electrode surface by the formed molybdenum oxides. In the region of potentials of deposition of a nickel-molybdenum alloy there is realized the following shape of a time dependence of the current. Within the first few seconds of the electrolysis process, the current somewhat decreases. Then there occurs its increase, which is connected with the alloy deposition on the cathode. In the course of electrolysis there occurs a decrease in the molybdenum content in the cathodic deposit.     

O在Au(111)表面吸附的密度泛函理论研究

应用密度泛函理论，本文系统地研究了O在Au(111)表面上的吸附能、吸附结构、功函数、电子密度和投影态密度，给出了覆盖度从0.11ML到1.0ML的范围内，O的吸附特性随覆盖度变化的规律.研究发现O的稳定吸附位为3重面心立方(fcc)洞位，O在fcc洞位的吸附能对覆盖度比较敏感，其值随着覆盖度的增加而减小；O诱导Au(111)表面功函数的变化量与覆盖度成近线性关系，原因是Au表面电子向O偏移，形成表面偶极子；O—Au的相互作用形成成键态和反键态，且反键态都被占据，造成O—Au键很弱，O吸附能较小. 关键词： 表面吸附 Au(111)表面 密度泛函理论 电子特性     

Co-P非晶态合金电子性质和局域结构的理论研究

根据Co P非晶态合金结构的短程有序和结构中可能存在P -P相互作用的实验事实 ,选择了单磷原子簇模型ConP(n =1～ 5 )和双磷原子簇模型ConP2 (n =1～ 4 ) ,用密度泛函理论方法对其进行计算 .结果表明 ,在单磷Co2 P( 2 ) 、Co3 P( 1) 及Co4P( 2 ) 模型体系中 ,Co原子供给P原子电子 ,与电负性规则一致 ,同时Co和P之间具较强化学作用 ,可以形成稳定的原子簇 ;而在双磷和单磷原子簇Co5P( 1) 模型体系中 ,形成的原子簇不稳定 ,采用单磷Co2 P( 2 ) 、Co3 P( 1) 及Co4P( 2 ) 模型能较好地反映Co P非晶态合金的结构特点 .     

Non-isothermal short-range-order kinetics of binary alloys as influenced by solute-vacancy complexes

A model describing the roles of bound and unbound vacancies is proposed in order to predict defect decay and short-range-order kinetics of quenched binary alloys during linear heating experiments. This is an alternative treatment of a previous approach. The model has been applied to the differential scanning calorimetry (DSC) curves of Cu-5 at.% Zn quenched from different temperatures. An expression to calculate the activation energy for migration of solute-vacancy complexes was also developed which make use of DSC trace data. A value of 89.12±0.32 kJ mol^-1 was obtained for the above alloy. The relative contribution of bound and unbound vacancies to partition of effective activation energy corresponding to the ordering process as influenced by quenching temperature was also assessed. This revised version was published online in July 2006 with corrections to the Cover Date.     

An experimental study on the kinetics of leaching for the preparation of a Raney-silver catalyst

A Raney-Ag catalyst was prepared by leaching out aluminium from a Raney Ag-Al alloy with NaOH solution. The kinetics of leaching has been investigated in a stirred-batch-reactor at various temperatures by using alloy particles of different sizes. The kinetic model best fitting the experimental results has been determined. This revised version was published online in June 2006 with corrections to the Cover Date.     

快冷Fe_(71)Al_(29)合金中的两个内耗峰

用一个计算机控制的倒扭摆研究了快冷Fe71 Al2 9合金中的两个内耗峰 .在快冷的Fe71 Al2 9样品中分别在 180℃(P1 ) ,340℃ (P2 )和 5 10℃ (P3)出现了内耗峰 ,而在慢冷的Fe71 Al2 9样品中只发现了P3峰 .快冷样品中的P1 和P2峰在从 6 5 0℃冷却下来的测量过程中或在 35 0℃经过较长时间的时效后消失 ,其峰高随时效时间的增加而下降 ,直至消失 .P1 和P2 峰都有弛豫特征 ,它们的激活能分别为 :H1 =1.0 3± 0 .0 8eV(P1 峰 ) ;H2 =1.6 4± 0 .0 5eV(P2 峰 ) .P1 峰被认为是无序合金中Al原子在四面体点阵内的最近邻运动所引起 ,P2 峰则是无序合金中Al原子在四面体点阵内的次近邻运动所引起     

Near-barrier fusion reactions induced by α on197Au,193Ir,191Ir,185Re,181Ta,121Sb and69Ga nuclei

Fusion-evaporation cross-sections for the α-induced reactions upon¹⁹⁷Au,¹⁹³Ir,¹⁹¹Ir,¹⁸⁵Re,¹⁸¹Ta,¹²¹Sb and⁶⁹Ga nuclei at bombarding energies near the Coulomb barrier have been measured by off-line observation of the γ-rays emitted in the radioactive decay of the residual nuclei using stacked foil technique. The total fusion cross-section for the systems have been compared with simple statistical model calculations using the code ALICE/91 as well as with the coupled channel calculations that include the β₂ and ν₄ slatic deformations and dynamic couplings of the vibrational/rotational states of the target and the projet tile using the code CCDEF.