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A criterion based on solidification microstructure was proposed to precisely predict the hot tearing behavior of cast alloys, which takes into account the effects of both mechanical and nonmechanical factors. This criterion focuses on the events occurring at the grain boundary, which are determined by the thermal contraction, solidification shrinkage, grain growing and liquid feeding. This criterion responds to a series of factors that affect hot tearing, such as alloy composition, mold design, casting process and microstructure. Its credibility has been validated by studying the hot tearing behavior of Mg-Ce alloys. In conformity with the experimental results, this criterion predicted decrease in the number of rods occurring hot tearing with increasing cerium content. A simplified criterion was derived and validated by Mg-Ce (equiaxed grain) and Mg-Al (columnar grain) alloy systems, which is suitable for the case where the eutectic liquid fraction is low and the liquid feeding can be ignored. In addition, a hot tearing index for equiaxed grains was proposed, that is, | d T / d ( f s 1 / 3 ) | near ( f s ) 1 / 3 = 1 , and its prediction results were consistent with the hot tearing susceptibility calculated from the experimental results.

Sensitive detecting of Hg2+ in the ecological environment and biological systems has become essential because these contaminants can cause serious health hazard and environmental pollution problem. Herein, we design and synthesize a new small molecule ratiometric fluorescent probe P-Hg for monitoring Hg2+ based on ESIPT/ICT mechanisms. The structure of probe P-Hg was confirmed by X-ray, NMR and HRMS spectrum. Significantly, the probe P-Hg exhibits desirable properties such as high sensitivity, high selectivity and good linearity of the concentrations of Hg2+ (0–35 μM) with a low detection limit (S/N = 3) of 5.8 nM. Furthermore, the detecting mechanism was proved by HRMS,1H NMR.

Bisbenzothienyl iridium(III) complexes, [Ir(bt)2(PR3)]X (bt: 2-phenylbenzo[ d]thiazole, R = n-Bu or Ph, X = OTf, BF4 or SbF6) are reported, two of which, (R = n-Bu or Ph, X = OTf), have been characterised by X-ray crystallography. The complexes are thermally stable and their photophysical properties are presented, together with their catalytic activity in the “borrowing hydrogen reaction” of alcohols with amines.

A water-soluble fluorescent SO2 derivatives probe PI-SO 2 based on a phenanthroimidazole dye, and a sensitive SO2 recognition site, aldehyde was constructed. The probe PI-SO 2 exhibits desirable properties such as high sensitivity, high selectivity and good water-solubility. Significantly, we have demonstrated that the probe PI-SO 2 is suitable for rapidly fluorescence detecting of SO2 derivatives in aqueous solution and serum. The application of the novel probe PI-SO 2 proved that it was not only a useful tool for the detection of SO2 derivatives in vitro, but also a potential assay for investigating the effects of SO2 derivatives, and demonstrating its value in practical applicationin of complex biological samples.

Magnesium alloy is a promising material for light-weight bipolar plates of proton exchange membrane fuel cell (PEMFC) owing to its low density, but high susceptibility to corrosion limits the application. In this paper, a novel hydrophobic Polytetrafluoroethylene (PTFE)/Carbon cloth/Ag multilayer coating is fabricated on Mg substrate. Potentiodynamic polarization results reveal that the multilayer coating decreases the corrosion current density of bare Mg dramatically from 17.24 μA/cm2 to 0.058 μA/cm2, meanwhile, the interfacial contact resistance (ICR) between carbon paper and coated magnesium drops from 100.6 mΩ cm2 to 27.28 mΩ cm2 at 1.4 MPa. The mechanism of the superior corrosion resistance and electrical property of coated Mg is discussed, which may shed light on the development of the novel light-weight magnesium bipolar plates of PEMFC.

We have designed and synthesized the original example of stable 3H-pyrrolizine fused diazaborepin using boron–amine (B–N) chemistry. 3H-Pyrrolizine fused ‘naked’ diazaborepin was achieved by organocatalyst (piperidinium acetate) in modest yield. The structure of diazaborepin was a twisted backbone in saddle shape with torsion angels of more than 20° from its crystal and theoretical data. It had a larger stokes shift (>70 nm) than classical BODIPYs and the type of solvent had an effect on their fluorescence property.

We use density functional theory calculations to explain why β′-long instead of β′-short forms during age-hardening process in Mg–Gd alloys. We calculate strain energies and interfacial energies of β″, β′-short and β′-long in Mg–Gd alloys and find that (1) results of strain energies and interfacial energies of β″ agree well with other theoretical works (2) habit plane of β′-long predicted by density functional theory calculations is consistent with experimental observation (3) strain energy is mainly responsible for the formation of β′-long instead of β′-short in the age-hardening process.

In this paper, the hot compressive deformation characteristics of a Mg–10Gd–3Y–0.5Zr (GW103K) alloy have been investigated by isothermal compression test at the temperature range of 350–450°C and strain rate range of 0.0001–0.1s−1. True stress–strain relationships at various strain rates showed the typical strain hardening and softening stage which is indicative of dynamic recrystallization during deformation. The results showed that the peak stress was obviously dependent on temperature and strain rate. A constitutive equation to describe the deformation process was established based on the hyperbolic sine function. The stress exponent n and apparent activation energy Q were determined to be 3.018 and 203.947 kJ/mol, respectively. Microstructure investigation showed that dislocation slipping was the dominant deformation mechanism during the hot deformation at all conditions. However, at the temperatures lower than 400 °C and strain rates higher than 0.01s−1, twinning was observed to be activated, which indicated another deformation mechanism. Dynamic recrystallization and dynamic precipitation were found to occur simultaneously under such deformation condition.

The 7th generation semi-submersible drilling unit (CSDU) represents a significant step forward for the ultra deepwater drilling units in terms of equipment specifications, operational efficiency, flexibility and reliability. Due to significant Variable Deck Load (VDL) increase, the 7th generation CSDU to be designed with larger main dimensions and particulars compared with its previous generations, which brings up a big challenge of the structural design. This paper presents the structural configuration selection and optimization design based on the profound investigation on the load-resistance characteristics of the overall structures and considering the stress distribution variation of the deck box with the integration of different lower hull configurations. This paper also investigates the effects of different types of upper and lower hull joints on the structural strength and fatigue in way of the main connection regions and provides the major connection optimization design. The optimized configuration and major connections have been used in the structural design of the 7th generation semi-submersible drilling unit.

A simple ligand-free cyclization of propargylic alcohols with enaminones has been developed by using FeBr3 as catalyst. This reaction provides an easy and convenient method to synthesize polysubstituted 1,2-dihydropyridine derivatives.

The Mg-13Y bulk alloy was prepared by conventional casting process and the Mg-13Y powder was processed by ball milling using the casting alloy under the protection of argon. The hydrogenation thermodynamics, hydrogenation process and phase transitions were carefully investigated in the Mg-13Y powder alloy. It is shown that the Mg-13Y casting alloy consists of Mg24Y5 phase and α-Mg containing yttrium which have different hydrogenation enthalpies, −195 kJ/mol H2 (by calculation) and −42 kJ/mol H2 (by Pressure–Composition–Temperature experiment), respectively. The structure evolution and phase transition in the Mg-13Y bulk alloy treated at 673 K and at 4 MPa for 40 h were observed by an optical microscopy (OM), a scanning electron microscopy (SEM), a transmission electron microscopy (TEM) and X-ray diffraction (XRD). The large Mg24Y5 phase in the bulk Mg-13Y alloy could be destroyed into fine cuboid-shaped YH2 phases during the hydrogenation process, which is probably responsible for the improvement of mechanical properties of Mg-13Y alloy.

A high-strength Mg-15.3Gd-1.8Ag-0.3Zr (GQ152K, mass fraction) alloy was prepared by conventional ingot metallurgy process. The solution and aging (denoted as T6) treated alloy exhibits remarkable mechanical properties with ultimate tensile strength of 421MPa and tensile yield strength of 309MPa. It has higher igniting temperature of 1 208 K. Moreover, it can stand against flame at 1 203K for over 6min in vertical burning tests, and its flammability behavior is very similar to that of 6101Al alloy. Vertical burning tests appear to be able to directly study the flammability behavior of Mg alloys and it appears to be a good approach to study the flammability behavior of Mg alloys in an aircraft fire accident.

Morphology and microstructure of precipitate phases in a Mg–12Dy–3Nd–0.4Zr (wt.%) alloy, before and after extrusion, has been studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). The eutectic phase, with composition of Mg 5 (Nd 0.47 Dy 0.53 ), has a fcc crystal structure ( a = 2.24 nm). The rectangular particles, at or near grain-boundaries in the solution treated state, has a fcc crystal structure ( a = 0.526 nm) with composition of Dy 17 Mg 3 . Many elliptical particles, distributed almost homogeneously across the matrix in the as-extruded alloy, was identified a fcc crystal structure ( a = 2.24 nm) with composition of Mg 5 (Nd 0.50 Dy 0.50 ), which should be identical to the eutectic phases except the difference in morphology.

The morphology and crystal structure of {beta}'' precipitate phases in a Mg-Dy-Gd-Nd system have been studied using transmission electron microscopy and X-ray diffraction. Three orientation relationships have been observed between {beta}'' precipitate phases and the {alpha} matrix phase with the habit plane parallel to {l_brace}112-bar 0{r_brace}{sub {alpha}}. The orientation relationship between the {beta}'' precipitates and the matrix is [0001]{sub {beta}}{sub ''}//[0001]{sub {alpha}}, [11-bar 00]{sub {beta}}{sub ''}//[11-bar 00]{sub {alpha}}. The structure of the {beta}''phase, with the interspaces between Dy/Gd/Nd atoms filled with magnesium atoms, is completely consistent with that of the matrix.

A novel fabrication process of surface modified composite layer by pulse current gas tungsten arc (GTA) surface modification process was used to deposit B4C particles on the surface of magnesium alloy AZ31. This method is an effective technique in producing a high performance surface modified composite layer. During the pulse current GTA surface modification process, considerable convection can exist in the molten pool due to various driving forces and the pulse current could cause violent stirring in the molten pool, and the large temperature gradient across the boundary between the GTA modified surface and matrix metal resulted in rapid resolidification with high cooling rates in the molten pool, so that the process result notable grain refinement in the GTA surface modified composite layer. The hardness and wear resistance of the GTA surface modified composite layer are superior to that of as-received magnesium alloy AZ31. The hardness values and wear resistance of GTA surface modified composite layer depend on the GTA process parameters and the B4C particles powder concentration and distribution. The optimum processing parameters for the formation of a homogeneous crack/defect-free and grain refinement microstructure were established.

Microstructure evolution, texture development and their influence on mechanical properties of Mg-10Gd-3Y-0.4Zr (wt.%) alloy processed by equal channel angular press (ECAP) at 450 °C were studied. The samples were prepared by ECAP from one to four passes. The results show that recrystallization preferentially occurred near the grain boundary, and the percentage of high-angle grain boundaries increases with the increase of passes. After four passes, the microstructure is still inhomogeneous, the fine and coarse grain zones exist simultaneously. It is attributed to the higher extrusion temperature; the grain grows and aggregates easily, which is confirmed through comparative experiment. The strength increases obviously after one pass, unexpectedly, it reduces slightly after two passes, the elongation is dramatically increased from 6.7% to 20.3%, which is due to the basal plane rotation from ED to the direction of flow strain and formation of a typical shear texture. The change of elongation and mechanical properties of this alloy during ECAP was discussed in terms of texture and the effect of the fine grain.

Friction stir processing (FSP) is a severe plastic deformation (SPD) processing, which is very useful to refine grain size and secondary phase as well as change the texture of metal materials. Many FSP research were focused on aluminum alloys, while there are few reports on FSP of magnesium alloys, esp. on precipitation-hardening Mg-RE alloys. This paper overviewed the micro structures and mechanical properties of several FSPed Mg-RE alloys, such as Mg-Gd-Zn-Zr, Mg-Gd-Ag-Zr, and Mg-Nd-Zn-Zr with or without long period stacking ordering (LPSO) structure. The effects of processing parameters, such as rotation rate and traversing speed, on microstructure and mechanical properties were evaluated. It shows that FSP can effectively lend to performance improvement by micro structure modification, including obtaining remarkable finer and more homogenized grains, changing distribution and volume percentage of secondary phase etc.

The solid track method-dual foil method i.e. 239Pu–235U pair and 115In—55Mn pair,which have been used to measure the neutron temperature and epithermal index in the irradiation site on the prototype MNSR, are described in this article. The experimental principle and method, measuring technique of the solid track method, the experimental results and error analysis are explained in details. The results are compared with those obtained by the dual foil mehtod-176 Lu—164Dy and 115In—55Mn pair, and they are in good coincidence within the error scope.