Stability of a bi-layer free film: simultaneous or individual rupture events?

We consider the stability of a long free film of liquid composed of two immiscible layers of differing viscosities, where each layer experiences a van der Waals force between its interfaces. We analyse the different ways in which the system can exhibit interfacial instability when the liquid layers are sufficiently thin. For an excess of surfactant on one gas–liquid interface, the coupling between the layers is relatively weak and the instability is manifested as temporally separated rupture events in each layer. Conversely, in the absence of surfactant, the coupling between the layers is much stronger and the instability is manifested as rupture of both layers simultaneously. These features are consistent with recent experimental observations.

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Closed Form Solutions for the Problem of Statical Behavior of Nano/Micromirrors Under the Effect of Capillary Force and Van Der Waals Force

Volume 11: Nano and Micro Materials, Devices and Systems; Microsystems Integration ◽

10.1115/imece2011-63112 ◽

2011 ◽

Author(s):

Ali Darvishian ◽

Hamid Moeenfard ◽

Hasan Zohoor ◽

Mohammad Taghi Ahmadian

Keyword(s):

Capillary Force ◽

Rotation Angle ◽

Van Der Waals ◽

Van Der Waals Force ◽

Combined Effect ◽

Geometrical Parameters ◽

Closed Form Solutions ◽

The Stability ◽

Vdw Force ◽

Stability Limits

The current paper deals with the problem of static instability of Micro/Nano mirrors under the combined effect of capillary force and van der Waals force. First the governing equations of the statical behavior of Micro/Nano mirrors under the combined effect of capillary force and casimir force is obtained using the newtons first law of motion. The dependence of the critical tilting angle on the physical and geometrical parameters of the nano/micromirror and its supporting torsional beams is investigated. It is found that existence of vdW torque can considerably reduce the stability limits of the nano/micromirror. It is also found that rotation angle of the mirror due to capillary force highly depends on the vdW toque applied to the mirror. Finally analytical tool Homotopy Perturbation Mehtod (HPM) is utilized for prediction of the nano/micromirror behaviour under combined capillary and vdW force. It is observed that a sixth order perturbation approximation accurately predicts the rotation angle and stability limits of the mirror. Results of this paper can be used for successful fabrication of nano/micromirrors using wet etching process where capillary force plays a major role in the system.

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Dominance of cohesion of EG-water molecules over Van der Waals force between SiO2-ZnO nanoparticles in the liquid interface

Powder Technology ◽

10.1016/j.powtec.2020.10.079 ◽

2021 ◽

Vol 379 ◽

pp. 537-546

Author(s):

Jalal Alsarraf ◽

Abdullah A.A.A. Al-Rashed ◽

Abdulwahab A. Alnaqi ◽

Aysan Shahsavar Goldanlou

Keyword(s):

Zno Nanoparticles ◽

Van Der Waals ◽

Liquid Interface ◽

Van Der Waals Force ◽

Water Molecules

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First direct measurement of van der Waals force

AccessScience ◽

10.1036/1097-8542.br0718131 ◽

2015 ◽

Keyword(s):

Direct Measurement ◽

Van Der Waals ◽

Van Der Waals Force

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FLUCTUATION-INDUCED RADIATIVE HEAT TRANSFER AND VAN DER WAALS FORCE FOR SPHERICAL SHAPES

Proceeding of First Thermal and Fluids Engineering Summer Conference ◽

10.1615/tfesc1.fnd.012853 ◽

2016 ◽

Author(s):

Yi Zheng ◽

Alok Ghanekar

Keyword(s):

Heat Transfer ◽

Radiative Heat Transfer ◽

Radiative Heat ◽

Van Der Waals ◽

Van Der Waals Force

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Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

10.26434/chemrxiv.8052218.v3 ◽

2019 ◽

Author(s):

Henrik Pedersen ◽

Björn Alling ◽

Hans Högberg ◽

Annop Ektarawong

Keyword(s):

Thin Films ◽

Thermodynamic Stability ◽

First Principles ◽

Thermal Equilibrium ◽

Density Functional ◽

Van Der Waals ◽

Chemical Vapor ◽

First Principles Calculations ◽

Functional Theory ◽

The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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First-Principles Study on Graphene/Mg2Si Interface of Selective Laser Melting Graphene/Aluminum Matrix Composites

Metals ◽

10.3390/met11060941 ◽

2021 ◽

Vol 11 (6) ◽

pp. 941

Author(s):

Zhanyong Zhao ◽

Shijie Chang ◽

Jie Wang ◽

Peikang Bai ◽

Wenbo Du ◽

...

Keyword(s):

Interfacial Energy ◽

First Principles ◽

Lattice Mismatch ◽

Van Der Waals ◽

Aluminum Matrix ◽

Van Der Waals Force ◽

Aluminum Matrix Composites ◽

Matrix Composites ◽

Charge Density Difference ◽

Interface Charge

The bonding strength of a Gr/Mg2Si interface was calculated by first principles. Graphene can form a stable, completely coherent interface with Mg2Si. When the (0001) Gr/(001) Mg2Si crystal plane is combined, the mismatch degree is 5.394%, which conforms to the two-dimensional lattice mismatch theory. At the interface between Gr/Mg2Si, chemical bonds were not formed, there was only a strong van der Waals force; the interfaces composed of three low index surfaces (001), (011) and (111) of Mg2Si and Gr (0001) have smaller interfacial adhesion work and larger interfacial energy, the interfacial energy of Gr/Mg2Si is much larger than that of α-Al/Al melt and Gr/Al interfacial (0.15 J/m2, 0.16 J/m2), and the interface distance of a stable interface is larger than the bond length of a chemical bond. The interface charge density difference diagram and density of states curve show that there is only strong van der Waals force in a Gr/Mg2Si interface. Therefore, when the Gr/AlSi10Mg composite is stressed and deformed, the Gr/Mg2Si interface in the composite is easy to separate and become the crack propagation source. The Gr/Mg2Si interface should be avoided in the preparation of Gr/AlSi10Mg composite.

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