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A fascinating structure transition of cerium around 5 GPa has been studied using high-resolution synchrotron angle-dispersive powder diffraction techniques. This study indicates that the structural transition of cerium strongly depends on the process of compression. Two runs experiments with different compression conditions demonstrate two different structural transition sequences at room temperature around 5 GPa, fcc′→ C 2/ m →bct for regular compression, fcc′→ C 2/ m →α-U→bct for the pre-compression. These results show that pressure is not the only factor to determining structural transformation at high pressure, and the structural transformation sequences can be varied by changing the external conditions e.g. pre-compression.

In order to figure out the oxidation behavior of steels during heating, five micro-alloyed steels were subjected to continuous and isothermal oxidation using the thermo gravimetric analyzer and the Gleeble-3500 thermo-mechanical simulator. The microstructure of oxide scales, especially the thickness fractions of Fc2O3, Fe3O4 and FeO layers, was analyzed using the scanning electron microscope (SEM), electron probe microanalyzer (EPMA) and electron backscattered diffraction (EBSD) techniques. The micro-alloyed steels containing alloying elements (Si, Cr, Ni and Cu) show a higher oxidation resistance compared with the low carbon steel. It is found that alloying elements accumulated at scale/substrate interface during high temperature oxidation. Alloying elements function in two ways in the oxidation of steels: one is enhancing the scale/substrate interface and consequently suppressing the blister of scales; and the other is impeding the outward diffusion of iron cations from substrate to scales, resulting in the decrease of oxidation rate. As the diffusion of iron cations is impeded, the thickness fractions of Fe2O3 and Fe3O4 of micro-alloyed steels are more than those of low carbon steels.

A bismuth oxide (Bi2O3)-dispersed carboxylated nitrile butadiene rubber (XNBR) flexible film was prepared as a flexible lead-free material for gamma ray (γ-ray) attenuation. However, obtaining a uniform and stable dispersion of Bi2O3 in carboxylated nitrile butadiene rubber latex (XNBRL) is a challenge due to sedimentation induced by the remarkable density differences. Here, this challenge was approached by reducing the Bi2O3 particle radius, increasing the viscosity of the latex, and adding a dispersant. The experimental results confirmed that Bi2O3 was well dispersed in the XNBRL in the concentration range of 30–70 wt%. The mechanical properties demonstrated that the Bi2O3/XNBR flexible films had a good resistance to oil, acid, alkali, and hot air. The linear attenuation coefficients of the Bi2O3/XNBR flexible films obtained from the experiments were in good agreement with the calculated values. The attenuation efficiencies of the Bi2O3/XNBR flexible films with different thicknesses and Bi2O3 contents were investigated for a few different γ-ray energies. These results showed that the Bi2O3/XNBR flexible films have wide application prospects for low-energy γ-ray attenuation.

Despite the fact that five kinds of uranium nitrides, i.e., uranium mononitrides (UN, R3m and Fm3m), a uranium dinitride (UN2, Fm3m), and uranium sesquinitrides (α-U2N3, Ia3; β-U2N3,P3m1), have been confirmed, until now the phase relations are not well understood because of the puzzling nonstoichiometric issue. This work reinvestigated the crystallographic structures of these phases using cluster formula theory. The principal clusters (cuboctahedron with six squares and eight triangles) in these phases were determined. N atoms can occupy either six octahedral sites (square face centers) or eight tetrahedral sites (formed by a center atom and a triangle) in the principal cluster of 13 U atoms, resulting in these diversified phases and the nonstoichiometric issue. Also, phase transformations at certain temperatures and pressures (from CaF2-type UN2 to Mn2O3-type U2N3, from Mn2O3-type U2N3 to NaCl-type UN, and from NaCl-type UN to HgIn-type UN) were deduced by tracking the bond and angle changes of a si...

The temperature and stress fields in beryllium during high speed cutting process were studied by employing a thermo-mechanically coupled finite element method (FEM). The results show that the temperatures in beryllium increase only a little during the cutting process. Both of the residual stresses for along and normal to the cutting direction are tensile stresses in the surface of beryllium after cutting. The cutting force and thrust force are about 280 and −250 kN/m at the steady stage, respectively. The main effects of coolant on the cutting process are to decrease the friction coefficient and heat between the tool and the workpiece, so to reduce the temperature, but almost no effects are made for stress. This study is helpful to enhance the understanding for stress formation and optimize the process parameters of beryllium.

A duplex treatment of plasma nitriding followed by deposition of a Ti/TiN multilayer coating was performed on commercial pure iron. Plasma nitriding was carried out using high frequency low bias voltage plasma immersion ion implantation (HLPIII), and the Ti/TiN multilayer films were deposited using unbalanced magnetron sputtering on the nitrided iron surface. The plasma nitriding layer was 4 μm thick, consisting of mainly e-Fe3N and γ-Fe4N. The microhardness of the iron with Ti/TiN multilayer coating + plasma nitriding duplex treatment was over 18 GPa, somewhat harder than that of iron with a Ti/TiN multilayer film but without plasma nitriding, and almost 5 times that of the (only) nitrided iron. The film-cohesion for Ti/TiN multilayer film on the nitrided substrate was much better than that on the substrate without nitriding treatment. Comparing with the Ti/TiN film on bare iron, the samples with Ti/TiN multilayer coating + plasma nitriding duplex treatment have better corrosion resistance.

Neutral trinuclear metallomacrocycles, [Cp∗RhCl(μ-4-PyS)]3 (3) and [Cp∗IrCl(μ-4-PyS)]3 (4) [Cp∗ = pentamethylcyclopentadienyl, 4-PyS = 4-pyridinethiolate], have been synthesized by self-assembly reactions of [Cp∗RhCl2]2 (1) and [Cp∗IrCl2]2 (2) with lithium 4-pyridinethiolate, respectively. In situ reaction of complex 3 with three equivalent of lithium 4-pyridinethiolate resulted in [Cp∗Rh(μ-4-PyS)(4-PyS)]3 (5) containing both skeleton and pendent 4-PyS groups. Chelating coordination of 2-pyridinethiolate broke down the triangular skeleton to give mononuclear metalloligands Cp∗Rh(2-PyS)(4-PyS) (6) and Cp∗Ir(2-PyS)(4-PyS) (7) [2-PyS = 2-pyridinethiolate], which could also be synthesized from Cp∗RhCl(2-PyS) (10) and Cp∗IrCl(2-PyS) (11) with lithium 4-pyridinethiolate. The coordination reactions of 6 with complexes 1 and 2 gave dinuclear complexes [Cp∗Rh(2-PyS)(μ-4-PyS)][Cp∗RhCl2] (8) and [Cp∗Rh(2-PyS)(μ-4-PyS)][Cp∗IrCl2] (9), respectively. Molecular structures of 3, 4, 6 and 11 were determined by X-ray crystallographic analysis. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.

Four half-sandwich cobalt complexes, Cp∗Co(2-PyS)2 (2), Cp∗Co(2-PyS)2 · HI (3), Cp∗Co(2-PyS) (4-PyS) (4), (Cp∗Co)2(μ-PhS)2(μ-2-PyS)I (5) [Cp∗ = pentamethylcyclopentadienyl, 2-PyS = 2-pyridinethiolate, 4-PyS = 4-pyridinethiolate, PhS = benzenethiolate] were successfully synthesized by the reactions of 2-pyridinethione, lithium 4-pyridinethiolate and lithium benzenethiolate with Cp∗Co(2-PyS)I (1), respectively. Complexes 2 and 3 have the structures with two 2-pyridinethiolates ligands coordinated to the cobalt atom. Two different pyridinethiolates ligands can be identified in complex 4. The molecular structure of 5 consists of two Cp∗–Co fragments, which are triply bridged by three sulfur atoms from different ligands. The molecular structures of 3 and 5 were determined by X-ray crystallographic analysis. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.

Five binuclear half-sandwich cobalt complexes, [(η5-C5H4)Co(CO)I2]2SiMe2 (3), [(η5-C5H4)Co(S2C2B10H10)]2SiMe2 (4), [(η5-C5H4)]2Co2(μ2-S2C2B10H10)SiMe2 (5), [(η5-C5H3)CoI2](μ-I)[(η5-C5H3)Co(CO)I](SiMe2)2 (8), [(η5-C5H3)Co(S2C2B10H10)]2(SiMe2)2 (9), were successfully synthesized in moderate yield by the reactions of corresponding ligands, (C5H5)2SiMe2 (1) and (C5H4)2(SiMe2)2 (6), respectively. The molecular structures of 3, 5, 6, 8 and 9 was determined by X-ray crystallographic analysis, which distinctly depict various molecular structures containing the Cp rings and the metal centers with halide or 1,2-dicarba-closo-dodecaborane-1,2-dithiolato ligands. For the (η5-C5H4)2SiMe2 complexes, coordination of the fragments CpCo favors a exo conformation. With the rigid structure of the di-bridged ligand (C5H4)2(SiMe2)2, only cis isomers of the corresponding (η5-C5H3)2(Si2Me2)2 complexes are formed. All the complexes have been well characterized by elemental analysis, NMR and IR spectra.

The half-sandwich cobalt(III) and rhodium(III) complexes with pyridine-2-thiolato ligands Cp*Co(PyS)I (3) and Cp*Rh(PyS)Cl (4) [Cp* = pentamethylcyclopentadienyl, PyS = pyridine-2-thiolate] were obtained by reactions of lithium pyridine-2-thiolate (PySLi) with Cp*Co(CO)I2 (1) and [Cp*RhCl2]2 (2), respectively, in high yield. Complexes 3 and 4 reacted with monodentate LiSC2(H)B10H10 to give Cp*Co(PyS)[SC2(H)B10H10] (5) and Cp*Rh(PyS)[SC2(H)B10H10] (6), respectively. Reactions of 3 and 4 with Li2S2C2B10H10 resulted in C−H activation of a methyl group of the Cp* of the cobalt complex to give [(C5Me4CH2SC5H4N)Co(S2C2B10H10)] (7). No such activation of a methyl group of the Cp* of the rhodium complex occurred, and Cp*Rh[Py(H)S](S2C2B10H10) (8) was the product.

The reaction of bis[(2-methoxyethyl)cyclopentadienyl] titanium dichloride with dilithium dithiolato carborane in THF give a novel hexanuclear organotitanium ion complex [ Cp 6 ′ Ti 6 ( μ 3 -O ) 8 ] [ C 2 B 10 H 10 ( μ - S 2 ) 2 C 2 B 9 H 10 ] 2 (Cp′ = C5H4CH2CH2OCH3) ([1][2]2) as yellow crystal blocks. The cation [1]2+ has an octahedral metallic skeleton of six titanium atoms with the tricoordinated oxygen (μ3-O) and the anion [2]− consists of two S2 bridged 7,8-dicarbaundecaborate cluster and 1,2-dicarba-closo-dodecaborate cluster.

Beryllium is a specific metal, its atomic configuration is ls 1 2s 2 and affects the shape of s valence band and p valence band because there is no electron in the p sublayer, which dimers bond length is 11% more than inside and (0001) atomic spacing shows 6% abnormal expansion. Compared with other elements, beryllium shows abnormal surface properties which the surface adsorption energy is up to 3.32 eV/atom due to electron exciting from s layer to p layer in the solid. In this paper, the adsorption and oxidation properties for Be and Be/00Cr17Ni14Mo2 stainless steel bonding joint were investigated by auger electron spectroscopy (AES) and two secondary ion mass spectrometry (SIMS). The results show that Beryllium, welding seam and 00Cr17Ni14Mo2 stainless steel matrix with beryllium adsorbed strongly in C and O then seriously oxidized even in super high-vacuum atmosphere, whose compounds remained in the welding joint and formed inclusion and segregation, and resulted in reducing bonding strength. Thus, pretreatment of beryllium surface and control of bonding atmosphere are significantly important, which can determine directly the success or failure of diffusion bonding for Be/00Cr17Ni14Mo2 stainless steel, and provides a guide for beryllium welding with other material.

Microstructure of nickel deposit ,which was prepared with pulse-plating technology on depleted uranium surface, has been studied by X-ray diffractometry（XRD）,Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM). The results indicate that the crystallographic structure of the deposit is face centered cubic; the deposit has a highly preferred orientation of (200), the relative orientation density of (200) is 3.44; the average grain size is about 45.5nm. The deposit is fine and has multi-crystal nature as well as crystallographic defects as dislocation, stacking and twin. It’s feasible to prepare nanocrystalline nickel deposit on depleted uranium surface with pulse plating technology.

The interface structure of Be/HR-1 stainless steel (SS) joint following diffusion bonding was investigated. Metallurgical observation, electron scanning microscopy, X-ray diffraction and scanning Auger microspectroscopy were performed for basic evaluation of bonded joints. There are intermetallic compounds such as Be11Fe and Be12Cr in the interface region of Be/SS joints, which drastically reduce the mechanical strength of the joints. Cu, Ag and Al barriers can block effective inter-diffusion of Be and HR-1 stainless steel, then forming brittle phases.

Four half-sandwich cobalt complexes bearing pendant sulfur or oxygen ligands have been reported and tested as catalysts for olefin polymerization in the presence of MAO. The molecular structure of complexes 1 has been determined by X-ray crystallographic analysis. Complexes 1 and 2 exhibited high activities of up to 106 g PE mol−1Co h−1 with moderate molecular weight (Mw ≈ 104 g mol−1) of polyethylene in the ethylene polymerization.

We describe an experimental instrument used for measuring nondestructively the residual stress using short wavelength X-ray, tungsten kα1. By introducing a photon energy screening technology, the monochromatic X-ray diffraction of tungsten kα1 was realized using a CdTe detector. A high precision Huber goniometer is utilized in order to reduce the error in residual stress measurement. This paper summarizes the main performance of this instrument, measurement depth, stress error, as opposed to the neutron diffraction measurements of residual stress. Here, we demonstrate an application on the determination of residual stress in an aluminum alloy welded by the friction stir welding.

This study presents high pressure phase transitions and equation of states of cerium under pressures up to 51 GPa at room temperature. The angle-dispersive x-ray diffraction experiments are carried out using a high energy synchrotron x-ray source. The bulk moduli of high pressure phases of cerium are calculated using the Birch–Murnaghan equation. We discuss and correct several previous controversial conclusions, which are caused by the measurement accuracy or personal explanation. The c/a axial ratio of e-Ce has a maximum value at about 29 GPa, i.e., c/a ≈ 1.690.