Supertwisted spirals of layered materials enabled by growth on non-Euclidean surfaces

Science ◽  
2020 ◽  
Vol 370 (6515) ◽  
pp. 442-445 ◽  
Author(s):  
Yuzhou Zhao ◽  
Chenyu Zhang ◽  
Daniel D. Kohler ◽  
Jason M. Scheeler ◽  
John C. Wright ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Crystal Lattice ◽  
Screw Dislocation ◽  
General Model ◽  
Euclidean Geometry ◽  
Layered Materials ◽  
Tungsten Disulfide ◽  
Mathematical Framework ◽  
Tungsten Diselenide ◽  
And Tungsten

Euclidean geometry is the fundamental mathematical framework of classical crystallography. Traditionally, layered materials are grown on flat substrates; growing Euclidean crystals on non-Euclidean surfaces has rarely been studied. We present a general model describing the growth of layered materials with screw-dislocation spirals on non-Euclidean surfaces and show that it leads to continuously twisted multilayer superstructures. This model is experimentally demonstrated by growing supertwisted spirals of tungsten disulfide (WS2) and tungsten diselenide (WSe2) draped over nanoparticles near the centers of spirals. Microscopic structural analysis shows that the crystal lattice twist is consistent with the geometric twist of the layers, leading to moiré superlattices between the atomic layers.

Effect of anion and cation substitution in tungsten disulfide and tungsten diselenide on conductivity and thermoelectric power

2017 ◽  
Vol 51 (6) ◽  
pp. 725-728 ◽  
Author(s):  
G. E. Yakovleva ◽  
A. I. Romanenko ◽  
A. S. Berdinsky ◽  
V. A. Kuznetsov ◽  
A. Yu. Ledneva ◽  
...  
Keyword(s):  
Thermoelectric Power ◽  
Tungsten Disulfide ◽  
Cation Substitution ◽  
Tungsten Diselenide ◽  
And Tungsten

Influence of carbon fibers and tungsten disulfide on the properties and structure of polytetrafluoroethylene

2018 ◽  
Vol 4 (3) ◽  
pp. 26-34
Author(s):  
A. A. Okhlopkova ◽  
A. P., Vasilev ◽  
T. S. Struchkova ◽  
A. G. Alekseev ◽  
P. N. Grakovich
Keyword(s):  
Carbon Fibers ◽  
Tungsten Disulfide ◽  
And Tungsten

Tribological Studies of Transmission Oil Dispersed With Molybdenum Disulfide and Tungsten Disulfide Nanoparticles

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
V. Srinivas ◽  
R. N. Thakur ◽  
A. K. Jain ◽  
M. Saratchandra Babu
Keyword(s):  
Molybdenum Disulfide ◽  
Size Variation ◽  
Tungsten Disulfide ◽  
Particle Size Analyzer ◽  
Transmission Oil ◽  
Mos2 Nanoparticles ◽  
The Stability ◽  
Friction And Wear Characteristics ◽  
Load Conditions ◽  
And Tungsten

This paper compares the tribological properties of transmission oil dispersed with molybdenum disulfide (MoS2) and tungsten disulfide (WS2) nanoparticles. Lubricant samples are prepared by dispersing MoS2 and WS2 nanoparticles in 0.5 wt.% in transmission oil. The nanoparticles are stabilized in the lubricant by surface modification with surfactant SPAN 80. The stability of the lubricant in terms of size variation of dispersed nanoparticles is evaluated using particle size analyzer. The antiwear, antifriction, and extreme pressure (EP) properties are tested on a four-ball wear tester and a comparison is made to assess the relative performance of MoS2 and WS2 nanoparticles. The friction and wear characteristics of lubricant dispersed with nanoparticles are strongly dependent upon the load taken into consideration. The lubricant dispersed with WS2 nanoparticles gave higher weld load and load wear index (LWI) than that of lubricant dispersed with MoS2 nanoparticles. The metallographic studies show that under high load conditions, the WS2 nanoparticles deposit more than MoS2 nanoparticles, thereby giving better performance at higher load conditions.

Chronicling a Blood-spattered Isle

2021 ◽  
pp. 55-111
Author(s):  
Oren Falk
Keyword(s):  
Structural Analysis ◽  
Case Studies ◽  
General Model ◽  
Brute Force ◽  
The Past ◽  
Textual Source ◽  
Recording Process ◽  
Medieval Europe ◽  
Authorial Intent ◽  
History Of

This chapter implements the general model of violence on case studies from the history of medieval Iceland, especially the Battle of Helgastaðir (1220) and other episodes from the life of Guðmundr Arason, Bishop of Hólar (r.1203–37). It also establishes how structural analysis of sagas—using the concepts of récit, histoire, and uchronia—nuances the picture of history reconstructed from such sources, tracing the transformation of occurrences (what happened) into events (experienced manifestations of meaning). Guðmundar saga A, the main textual source consulted here, demonstrates how uchronia, the ideology of the past, enabled texts to function autonomously of authorial intent: uchronic texts may reveal truths their authors were ignorant of, let alone truths they wished to suppress. By unpacking the ways brute force inflects both the historical social contests recorded in the saga and the narrative tensions of the recording process itself, this chapter highlights the necessity of examining violence in terms of a complex negotiation of power, signification, and risk. In the course of this investigation, various details of medieval Icelandic history are filled in, deepening and qualifying the general portrayal offered in the Introduction. Readers with little background in Icelandic history are familiarized with the contours of this history, while experts find some of its truisms (such as the categorical distinction between farmers and chieftains, or the supposed uniqueness of Iceland in high medieval Europe) re-examined

Dynamic mechanical properties, thermal and heat resistance of multiblock co-poly(urethane-imide) films with graphene and tungsten disulfide

2019 ◽  
Vol 68 (8) ◽  
pp. 1603-1612 ◽  
Author(s):  
A. L. Didenko ◽  
V. E. Smirnova ◽  
E. N. Popova ◽  
G. V. Vaganov ◽  
D. A. Kuznetcov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Resistance ◽  
Dynamic Mechanical Properties ◽  
Tungsten Disulfide ◽  
Dynamic Mechanical ◽  
And Tungsten

scholarly journals Exfoliated Nanocomposites Based on Polyaniline and Tungsten Disulfide

10.5772/63457 ◽  
2016 ◽  
Author(s):  
Barrit C.S. Lane ◽  
Rabin Bissessur ◽  
Alaa S. Abd-El-Aziz ◽  
Wael H. Alsaedi ◽  
Douglas C. Dahn ◽  
...  
Keyword(s):  
Tungsten Disulfide ◽  
And Tungsten
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