scholarly journals Graphene fatigue through van der Waals interactions

2020 ◽  
Vol 6 (42) ◽  
pp. eabb1335
Author(s):  
Teng Cui ◽  
Kevin Yip ◽  
Aly Hassan ◽  
Guorui Wang ◽  
Xingjian Liu ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Flexible Electronics ◽  
Shear Fracture ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Pristine Graphene ◽  
Plane Shear ◽  
Dynamic Reliability ◽  
Polymer Interface ◽  
Out Of Plane

Graphene is often in contact with other materials through weak van der Waals (vdW) interactions. Of particular interest is the graphene-polymer interface, which is constantly subjected to dynamic loading in applications, including flexible electronics and multifunctional coatings. Through in situ cyclic loading, we directly observed interfacial fatigue propagation at the graphene-polymer interface, which was revealed to satisfy a modified Paris’ law. Furthermore, cyclic loading through vdW contact was able to cause fatigue fracture of even pristine graphene through a combined in-plane shear and out-of-plane tear mechanism. Shear fracture was found to mainly initiate at the fold junctions induced by cyclic loading and propagate parallel to the loading direction. Fracture mechanics analysis was conducted to explain the kinetics of an exotic self-tearing behavior of graphene during cyclic loading. This work offers mechanistic insights into the dynamic reliability of graphene and graphene-polymer interface, which could facilitate the durable design of graphene-based structures.

Proton and fluorine magnetic resonance studies of some benzoyl fluoride derivatives. Sensitivity of the fluorine shifts to intramolecular van der Waals interactions and steric effects

1977 ◽  
Vol 55 (22) ◽  
pp. 3936-3941 ◽  
Author(s):  
Ted Schaefer ◽  
Kirk Marat ◽  
Kalvin Chum ◽  
Alexander F. Janzen
Keyword(s):  
Magnetic Resonance ◽  
Van Der Waals ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Van Der Waals Interactions ◽  
Proton Proton ◽  
Out Of Plane ◽  
Spin Coupling Constants ◽  
The Individual ◽  
Spin Spin Coupling

The syntheses and the analyses of the high resolution proton and fluorine magnetic resonance spectra of the 3-fluoro-4-methyl-, 2-fluoro-5-chloro-, 2-fluoro-6-chloro-, 2,6-difluoro-, and of the pentafluorobenzoyl fluorides are reported. The spin–spin coupling constants over five bonds between the sidechain fluorine-19 and the ring protons are sensitive to intrinsic substituent perturbations. Their use in the deduction of conformational preferences is much more problematical than is the use of the corresponding proton–proton couplings in benzaldehyde derivatives. The 2-fluoro-6-chloro compound is nonplanar, as indicated by a finite magnitude of the long-range proton–fluorine coupling over six bonds. The nonplanarity is also indicated by a comparison of the through-space fluorine–fluorine coupling to those in the other compounds. The chemical shift of the sidechain fluorine moves to low field by over 35 ppm as the size of the two ortho substituents increases. The individual shifts are discussed in terms of intramolecular van der Waals interactions and of out-of-plane twisting of the COF group.

In-plane and out-of-plane shear fracture toughness of rocks

2021 ◽  
Author(s):  
Bahador Bahrami ◽  
Morteza Nejati ◽  
Majid Reza Ayatollahi ◽  
Thomas Dreisner
Keyword(s):  
Fracture Toughness ◽  
Shear Fracture ◽  
Shear Loading ◽  
Mode Ii ◽  
Mode Iii ◽  
Brazilian Disk ◽  
Plane Shear ◽  
Double Edge ◽  
Out Of Plane ◽  
Tensile Fracturing

<p><span>Rocks in the subsurface are exposed to high amount of confinement which can potentially suppress the formation or the development of tensile-based cracks and thus, give rise to shear-based fracture growth. However, measuring the shear fracture toughness of rocks have been studied less in the literature, as providing the required confinement to force the shear fracturing precede tensile fracturing is not an easy task. In the current study, two new tests namely the double-edge notched Brazilian disk (DNBD) and the axially double-edge notched Brazilian disk (ANBD) are proposed to measure the in-plane (true mode II) and the out-of-plane (true mode III) shear fracture toughness of rocks, </span><span>K</span><sub><span>IIc </span></sub><span>and </span><span>K</span><sub><span>IIIc</span></sub><span>, respectively. We use the term </span><span>true </span><span>to emphasis that not only sustains the crack shear loading, but also the type of fracturing is shear-based. Finite element method is used to study the variations of stress field around the crack tip in these tests and to prove the applicability of the tests in providing mode II and mode III loading conditions. It is argued that both tests are straightforward and have several advantages compared to the existing ones. The effectiveness of the tests is empirically corroborated by conducting some experiments on Bedretto Granite. The pulverized surface of fracture in both the tests denotes the existence of friction which indicate the shear-based nature of fracture. Finally, the measured values of </span><span>K</span><sub><span>IIc </span></sub><span>and </span><span>K</span><sub><span>IIIc </span></sub><span>for Bedretto granite are compared to each other and to the reported values of </span><span>K</span><sub><span>Ic </span></sub><span>in the literature. It is shown that </span><span>K</span><span>IIc </span><span>and </span><span>K</span><span>IIIc </span><span>values are close to each other while both are more than two times greater than </span><span>K</span><span>Ic</span><span>.</span></p>

Crystal Structures of Two New Cyclosporin Clathrates

2000 ◽  
Vol 65 (12) ◽  
pp. 1950-1958 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Alexandr Jegorov
Keyword(s):  
Crystal Structures ◽  
Methyl Ether ◽  
Van Der Waals ◽  
Van Der Waals Interactions ◽  
Solvent Molecules ◽  
Butyl Methyl Ether

Two isomorphous clathrates formed by dihydrocyclosporin A or cyclosporin V with tert-butyl methyl ether are reported and compared with the structures of related P21-symmetry cyclosporin clathrates. The cyclosporin molecules in both structures are associated via van der Waals interactions forming cavities occupied by solvent molecules (cyclosporin : tert-butyl methyl ether is 1 : 2).

Van der Waals interactions of the disulfide bond revealed: A microwave spectroscopic study of the diethyl disulfide–argon complex

2021 ◽  
Vol 154 (12) ◽  
pp. 124306
Author(s):  
Tao Lu ◽  
Daniel A. Obenchain ◽  
Jiaqi Zhang ◽  
Jens-Uwe Grabow ◽  
Gang Feng
Keyword(s):  
Spectroscopic Study ◽  
Disulfide Bond ◽  
Van Der Waals ◽  
Van Der Waals Interactions

scholarly journals Microscopic evidence of strong interactions between chemical vapor deposited 2D MoS2 film and SiO2 growth template

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Woonbae Sohn ◽  
Ki Chang Kwon ◽  
Jun Min Suh ◽  
Tae Hyung Lee ◽  
Kwang Chul Roh ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Spherical Aberration ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
Interface Layer ◽  
Van Der Waals Interactions ◽  
Strong Interactions ◽  
Transition Electron Microscopy ◽  
Oxide Substrates

AbstractTwo-dimensional MoS2 film can grow on oxide substrates including Al2O3 and SiO2. However, it cannot grow usually on non-oxide substrates such as a bare Si wafer using chemical vapor deposition. To address this issue, we prepared as-synthesized and transferred MoS2 (AS-MoS2 and TR-MoS2) films on SiO2/Si substrates and studied the effect of the SiO2 layer on the atomic and electronic structure of the MoS2 films using spherical aberration-corrected scanning transition electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The interlayer distance between MoS2 layers film showed a change at the AS-MoS2/SiO2 interface, which is attributed to the formation of S–O chemical bonding at the interface, whereas the TR-MoS2/SiO2 interface showed only van der Waals interactions. Through STEM and EELS studies, we confirmed that there exists a bonding state in addition to the van der Waals force, which is the dominant interaction between MoS2 and SiO2. The formation of S–O bonding at the AS-MoS2/SiO2 interface layer suggests that the sulfur atoms at the termination layer in the MoS2 films are bonded to the oxygen atoms of the SiO2 layer during chemical vapor deposition. Our results indicate that the S–O bonding feature promotes the growth of MoS2 thin films on oxide growth templates.

Concisely modularized assembling of graphene-based thin films with promising electrode performance

2019 ◽  
Vol 3 (7) ◽  
pp. 1462-1470 ◽  
Author(s):  
Weiwei Wei ◽  
Rohit L. Vekariy ◽  
Chuanting You ◽  
Yafei He ◽  
Ping Liu ◽  
...  
Keyword(s):  
Thin Films ◽  
Graphene Oxide ◽  
Reduced Graphene Oxide ◽  
Double Layer ◽  
Van Der Waals ◽  
Cellulose Nanofibers ◽  
Van Der Waals Interactions ◽  
Electrode Performance ◽  
Reduced Graphene

Highly dense thin films assembled from cellulose nanofibers and reduced graphene oxide via van der Waals interactions to realize ultrahigh volumetric double-layer capacitances.

A comparison between approaches for the calculation of van der Waals interactions in flotation systems

2021 ◽  
Vol 167 ◽  
pp. 106804
Author(s):  
C. Weber ◽  
P. Knüpfer ◽  
M. Buchmann ◽  
M. Rudolph ◽  
U.A. Peuker
Keyword(s):  
Van Der Waals ◽  
Van Der Waals Interactions
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