Effects of gas adsorption isotherm and liquid contact angle on capillary force for sphere-on-flat and cone-on-flat geometries

Hsiao, Erik; Marino, Matthew; Kim, Seong H.

doi:10.1016/j.jcis.2010.09.005

Cited by 37 publications

(46 citation statements)

References 50 publications

(88 reference statements)

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“…). Hsiao et al theorized that adsorbed layers increase F cap , which provides support for this hypothesis. Additionally, Fisher et al found the Kelvin equation, Eq.…”

Section: Resultsmentioning

confidence: 89%

“…As described above, it is assumed in capillary condensation theory no adsorbed molecular layers on the particle surfaces exist. However, similar to non‐volatile liquids (Figure a), the adsorbed layers can interact with the condensed capillary bridge and affect F cap . In order for the adsorbed layer to induce a sudden change in macroscopic behavior, it is expected an abrupt change would similarly be found on the adsorption isotherm.…”

Section: Resultsmentioning

confidence: 99%

“…Only one surface is necessary for adsorption to occur, whereas capillary condensation requires two surfaces. Adsorbed layers can interact with the condensed bridge and cause deviations from the predictions . For the purposes of this work, we focus on systems that involve only capillary condensation and no vapor adsorption, as illustrated in Figure b and as described by the Kelvin equation …”

Section: Introductionmentioning

confidence: 99%

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Linking micro‐scale predictions of capillary forces to macro‐scale fluidization experiments in humid environments

et al. 2016

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The effects of increasing relative humidity (RH) on fluidization/defluidization are investigated experimentally and understood via particle-level predictions for the resulting capillary force. Experimentally, defluidization is found to be more sensitive to small changes in RH than fluidization. This sensitivity is captured by a new defluidization velocity U df , which characterizes the curvature of the defluidization plot (pressure drop vs. velocity) observed between the fully-fluidized (constant pressure drop) and packed-bed (linear pressure drop dependence on velocity) states; this curvature is indicative of a partially-fluidized state arising from humidity induced cohesion. Plots of U df vs. RH reveal two key behaviors, namely U df gradually increases with a relatively constant slope, followed by an abrupt increase at RH $55%. Furthermore, the bed transitions from Group A to Group C behavior between RH of approximately 60-65%. From a physical standpoint, these macro-scale trends are explained via a theory for capillary forces that, for the first time, incorporates measured values of particle surface roughness. Specifically, a model for the cohesive energy of rough surfaces in humid environments shows the same qualitative behavior as U df vs. RH for RH <55%, unlike predictions of the cohesive force. Furthermore, the abrupt transition at RH $60-65% is explained via the previously observed onset of liquid-like water adsorption, rather than crystal/ice-like adsorption, onto glass surfaces. V C 2016 American Institute of Chemical Engineers AIChE J, 62: [3585][3586][3587][3588][3589][3590][3591][3592][3593][3594][3595][3596][3597] 2016

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“…). Hsiao et al theorized that adsorbed layers increase F cap , which provides support for this hypothesis. Additionally, Fisher et al found the Kelvin equation, Eq.…”

Section: Resultsmentioning

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Linking micro‐scale predictions of capillary forces to macro‐scale fluidization experiments in humid environments

et al. 2016

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“…At a RH of 50%-60%, the thickness of the adsorbed water layer was estimated to be 0.98 nm on the native oxide-coated silicon surface and 0.4 nm on the hydrophobic Si-H surface [27]. Therefore, the initial friction behavior would have a large contribution from the capillarity effect on the native silicon oxide surface, which would be lacking on the Si-H surface [28]. As a result, the initial friction force of the Si-H/SiO 2 pair was much smaller than that of the Si-SiO x /SiO 2 pair.…”

Section: Friction-induced Reduction Of Adhesion During the Running-inmentioning

confidence: 99%

Running-in process of Si-SiO x /SiO2 pair at nanoscale—Sharp drops in friction and wear rate during initial cycles

et al. 2013

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Abstract:Using an atomic force microscope, the running-in process of a single crystalline silicon wafer coated with native oxide layer (Si-SiO x ) against a SiO 2 microsphere was investigated under various normal loads and displacement amplitudes in ambient air. As the number of sliding cycles increased, both the friction force F t of the Si-SiO x /SiO 2 pair and the wear rate of the silicon surface showed sharp drops during the initial 50 cycles and then leveled off in the remaining cycles. The sharp drop in F t appeared to be induced mainly by the reduction of adhesion-related interfacial force between the Si-SiO x /SiO 2 pair. During the running-in process, the contact area of the Si-SiO x /SiO 2 pair might become hydrophobic due to removal of the hydrophilic oxide layer on the silicon surface and the surface change of the SiO 2 tip, which caused the reduction of friction force and the wear rate of the Si-SiO x /SiO 2 pair. A phenomenological model is proposed to explain the running-in process of the Si-SiO x /SiO 2 pair in ambient air. The results may help us understand the mechanism of the running-in process of the Si-SiO x /SiO 2 pair at nanoscale and reduce wear failure in dynamic microelectromechanical systems (MEMS).

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“…The capillary force exerted on the contacting surfaces due to the meniscus is caused by the liquid surface tension and the curvature of the capillary bridge. 32 The amount of this force can be derived from the exact Young−Laplace equation for the curved liquid−vapor interface as 32,33 π…”

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confidence: 99%

Experimental and Theoretical Investigations on the Nanoscale Kinetic Friction in Ambient Environmental Conditions

et al. 2015

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The liquid lubrication, thermolubricity and dynamic lubricity due to mechanical oscillations are investigated with an atomic force microscope in ambient environmental conditions with different relative humidity (RH) levels. Experimental results demonstrate that high humidity at low-temperature regime enhances the liquid lubricity while at high-temperature regime it hinders the effect of the thermolubricity due to the formation of liquid bridges. Friction response to the dynamic lubricity in both high- and low-temperature regimes keeps the same trends, namely the friction force decreases with increasing the amplitude of the applied vibration on the tip regardless of the RH levels. An interesting finding is that for the dynamic lubricity at high temperature, high-humidity condition leads to the friction forces higher than that at low-humidity condition while at low temperature the opposite trend is observed. An extended two-dimensional dynamic model accounting for the RH is proposed to interpret the frictional mechanism in ambient conditions.

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Effects of gas adsorption isotherm and liquid contact angle on capillary force for sphere-on-flat and cone-on-flat geometries

Cited by 37 publications

References 50 publications

Linking micro‐scale predictions of capillary forces to macro‐scale fluidization experiments in humid environments

Linking micro‐scale predictions of capillary forces to macro‐scale fluidization experiments in humid environments

Running-in process of Si-SiO x /SiO2 pair at nanoscale—Sharp drops in friction and wear rate during initial cycles

Experimental and Theoretical Investigations on the Nanoscale Kinetic Friction in Ambient Environmental Conditions

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