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Three organic-inorganic hybrid materials, namely [RE(H2O)3K(H2O)2 (pddc)2]2H4[SiW12O40]·2H2O (RE = Pr (1), Nd (2); H2pddc = 3,4-pyridine dicarboxylic acid) and [Y(pzdc)(H2O)3]2H2[SiW12O40]·4H2O (3) (H2pzdc = 2,3-pyrazine dicarboxylic acid) have been synthesized and characterized by elemental analyses, IR spectra, UV spectra, TG analyses and X-ray crystallography. Single crystal X-ray analyses reveal that 1-3 all exhibit 2D layer structures. Interestingly, 1 and 2 are isostructural differenting from 3. In 3, the polyoxoanions [SiW12O40]4- connect the rare earth cations [Y(pzdc)(H2O)3]2C via Y-O bonds forming a (4, 4)-connected 2D topology net with Schl€afli symbol of 32.62.72. [ABSTRACT FROM AUTHOR]

A rare monocapped trivacant Keggin fragment [A-α-AsIIIAsVMo9O34]6–has been captured and an organic-inorganic hybrid arsenomolybdate (H2en)[Ni(en)2(H2O)]{[Ni(en)2][AsIIIAsVMo9O34]}∙3H2O (1) was obtained under hydrothermal conditions. The structure of 1 was determined by X-ray single-crystal diffraction and further characterized by IR spectroscopy, X-ray powder diffraction (XRPD), scanning electron microscope with energy dispersive X-ray (EDX-SEM) and X-ray photoelectron spectroscopy (XPS). Single-crystal structural analysis indicates that 1 contains the peculiar monocapped trivacant [A-α-AsIIIAsVMo9O34]6–fragment derived from the rare trivacant Keggin type [A-α-AsVMo9O34]9–unit capped by a triangular pyramidal {AsO3} group.1represents the first Ni-substituted inorganic-organic arsenomolybdate containing the [A-α-AsIIIAsVMo9O34]6–subunit. [ABSTRACT FROM AUTHOR]

The glide of <110>/{111} superdislocations in Ni 3 Al becomes prevalent in tertiary creep and take a dominant role in influencing the creep resistance of Ni-based single crystal superalloys at the tertiary stage. Here we carried out atomistic simulations to investigate the mobility law of screw, 30° mixed, 60° mixed and edge <110> superdislocations in Ni 3 Al. Based on the Peierls-Nabarro model, we found that the distance of the dissociated anti-phase boundary (APB) and complex stacking fault (CSF) of <110> superdislocations increases with increasing the character angle (from screw to edge), keeping a good accordance with the analysis by anisotropic elastic theory. We further study the motion of the superdislocations at temperatures ranging from 300 K to 1000 K. The dislocation mobility is distinct to its character angle, i.e. , the edge-like (30° and 90°) superdislocations have a higher speed than the screw-like (0° and 60°) superdislocations. For all types of superdislocations, the drag coefficient increases linearly with increasing temperature in the phonon-drag regime, while behaves to be independent on temperature in the asymptotic regime. Finally, we explored the origin of mobility disparity between the edge-like and screw-like superdislocations in terms of energy landscape for the dislocation glide. We observed that the two 1 / 2 <110> dissociated superpartials move coordinately in edge-like superdislocations with no variation of APB ribbon width. However, the motion of two superpartials are uncorrelated in screw-like superdislocations with the expansion and reduction of APB, resulting in a relatively higher Peierls barrier. Our present work could help to understand the creep failure in Ni-based single crystal superalloys. • The equilibrium configurations of <110> superdislocations in Ni 3 Al are characterized using the Peierls-Nabarro model. • The distance of anti-phase boundary and complex stacking fault increases with increasing the character angle (from screw to edge). • Edge-like (30° and 90°) superdislocations have a relatively higher mobility than screw-like (0° and 60°) superdislocations. • The mobility disparity between the edge-like and screw-like superdislocations lies in their distinct glide manners. [ABSTRACT FROM AUTHOR]

The excellent mechanical properties of Ni-based superalloys rely on their unique two-phase microstructure. Here we probe the influence of interfacial dislocation network on strain-rate sensitivity in Ni-based single crystal superalloys. The interfacial dislocation could generate a weak long-range interaction to the matrix dislocations at low stress, and react with the incoming dislocation to form junctions at high stress. The weak interaction results in the dislocation pile-up around the interphase boundary, while the strong dislocation reaction makes the gradual loss of interface coherency. With the activation energies, we predict the dependence of strain-rate sensitivity on temperature in a regime with two bounds correlated with these two kinds of interactions. The predicted values match well with that measured in experiments at elevated temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]