6,670 research outputs found
Role of disordered bipolar complexions on the sulfur embrittlement of nickel general grain boundaries
Minor impurities can cause catastrophic fracture of normally ductile metals. Here, a classic example is represented by the sulfur embrittlement of nickel, whose atomic-level mechanism has puzzled researchers for nearly a century. In this study, coupled aberration-corrected electron microscopy and semi-grand-canonical-ensemble atomistic simulation reveal, unexpectedly, the universal formation of amorphous-like and bilayer-like facets at the same general grain boundaries. Challenging the traditional view, the orientation of the lower-Miller-index grain surface, instead of the misorientation, dictates the interfacial structure. We also find partial bipolar structural orders in both amorphous-like and bilayer-like complexions (a.k.a. thermodynamically two-dimensional interfacial phases), which cause brittle intergranular fracture. Such bipolar, yet largely disordered, complexions can exist in and affect the properties of various other materials. Beyond the embrittlement mechanism, this study provides deeper insight to better understand abnormal grain growth in sulfur-doped Ni, and generally enriches our fundamental understanding of performance-limiting and more disordered interfaces
Alkyl substituted cucurbit[6]uril assisted competitive fluorescence recognition of lysine and methionine in aqueous solution
The use of competitive ratiometric fluorescence indicator displacement chemosensors derived from two alkyl substituted cucurbit[6]uril-based host-guest complexes is reported. In particular, the differing binding abilities of two cucurbit[6]uril derivatives towards the target analytes led to a useful ratiometric detection signal output for the discrimination of lysine and methionine versus the other tested α-amino acids in aqueous solution
Quantum spin Hall effect induced by electric field in silicene
We investigate the transport properties in a zigzag silicene nanoribbon in
the presence of an external electric field. The staggered sublattice potential
and two kinds of Rashba spin-orbit couplings can be induced by the external
electric field due to the buckled structure of the silicene. A bulk gap is
opened by the staggered potential and gapless edge states appear in the gap by
tuning the two kinds of Rashba spin-orbit couplings properly. Furthermore, the
gapless edge states are spin-filtered and are insensitive to the non-magnetic
disorder. These results prove that the quantum spin Hall effect can be induced
by an external electric field in silicene, which may have certain practical
significance in applications for future spintronics device.Comment: 4 pages, 5 figure
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