Structure Determination of Er Doped Ti-Al-Nb Alloy by Neutron Diffraction Analysis.

Neutron diffraction experiments with both conventional powder diffraction setup and under in-situ compressive loading were conducted to investigate the structural origins of large strength and toughness enhancements in Ti-16Al-27Nb alloy after Er addition. The primary phase is determined to be the ordered B2 structure form, in agreement with the previous electron microscopy study. Lattice strains of {210} and {100} planes were measured as a function of applied stress, and elastic anisotropy was found for both, and strong plastic nonlinearity was discovered for (210) reflection. The grain refinement during plastic deformation was proposed by both the 2D diffraction intensity distribution and SEM observations, while stress-induced martensitic phase transition was not observed in this study. It is believed that the activation of different slip systems and grain refinement might be the structural origin of the novel mechanical properties of this alloy.

Two-dimensional TaC nanosheets on a reduced graphene oxide hybrid as an efficient and stable electrocatalyst for water splitting.

A novel highly active and stable HER catalyst containing two-dimensional TaC nanosheets hybridized with reduced graphene oxide (2D TaC-RGO) was prepared as an efficient and stable hydrogen evolution reaction catalyst.

Synthesis of nanostructured clean surface molybdenum carbides on graphene sheets as efficient and stable hydrogen evolution reaction catalysts.

Small size molybdenum carbides (2.5 nm for MoC and 5.0 nm for Mo2C) with clean surface on graphene were prepared for efficient and stable hydrogen evolution reaction catalysts.

Disordered structure of ZrW1.8V0.2O7.9from a combined X-ray and neutron powder diffraction study at 530 K.

A novel compound, vanadium aliovalent substituted zirconium tungstate, ZrW1.8V0.2O7.9, was prepared with vanadium substituting tungsten rather than the common zirconium substitution. The structure of the high-temperature phase was refined from combined neutron and X-ray powder diffraction data gathered at 530 K. This phase is the disordered centric modification (space group Pa3) and the average crystal structure is similar to that of beta-ZrW2O8. The V atom occupies only a W2 site and charge compensation is achieved through oxygen vacancy, i.e. the oxygen vacancy occurs at only the O4 site. [Atom names follow the established scheme; Evans et al. (1996). Chem. Mater. 8, 2809-2823.].

Cubic ZrW(1.75)Mo(0.25)O(8) from a Rietveld refinement based on neutron powder diffraction data.

The solid solution in the system Zr-Mo-W-O with composition ZrW(1.75)Mo(0.25)O(8) (zirconium tungsten molybdenum octa-oxide) was prepared by solid-state reactions as a polycrystalline material. Its structure has cubic symmetry (space group P2(1)3) at room temperature. The structure contains a network of corner-sharing ZrO(6) octa-hedra (.3. symmetry) and MO(4) (M = W, Mo) tetra-hedra (.3. symmetry). Along the main threefold axis of the cubic unit cell, the MO(4) tetra-hedra are arranged in pairs forming M(2)O(8) units in which the M1O(4) tetra-hedra have larger distortions in terms of bond distances and angles than the M2O(4) tetra-hedra. These units are disordered over two possible orientations, with the M-O(terminal) vectors pointing to the [111] or [] directions. The reversal of the orientations of the M(2)O(8) units results from the concerted flips of these units. The time-averaged proportions of flipped and unflipped M(2)O(8) units were determined and the fraction of unflipped M(2)O(8) units is about 0.95. The order degree of the M(2)O(8) unit orientation is about 0.9. During the reversal process, the M-atom site has a migration about 0.93 Å, one of the O-atom sites has a 0.25 Šmigration distance, whereas two other O-atom sites migrate marginally (≃ 0.08 Å). The results prove the constraint strategy to be a reasonable approach based on the ratcheting mechanism.