China
Africa
Explore chapters and articles related to this topic
Monolayers and Multilayers
Published in Victor M. Starov, Nanoscience, 2010
Hernán Ritacco, Iván López-Montero, Francisco Monroy, Francisco Ortega, Ramón G. Rubio
In this kind of surface rheology experiments the barriers of the Langmuir through are driven to a sinusoidal motion of constant frequency, ω, that imposes a oscillatory strain perturbation in the film. Fourier transform analysis of the strain must show the true sinusoidal character of the movement and the monochromaticity, that is, the absence of frequency components other than the fundamental one, ω [47,48,115]. The monolayer is strained in the Langmuir trough by this uniaxial in-plane oscillatory motion of amplitude, u. Depending on the dimensions of the trough, u can be varied from 0 to typically 5% of the initial area A0, to perform an experiment within the linear regime. It must be considered that in this kind of rheological experiments nonlinearity can be reached by too high strain amplitude or too high strain rate, and that in order to perform experiments at variable strain amplitudes with constant frequency, the barrier speed c must be changed: u = c/ω.
Foaming Chemistry and Physics
Published in Leslie R. Rudnick, Lubricant Additives, 2017
Kalman Koczo, Mark D. Leatherman, Kevin Hughes, Don Knobloch
A significant amount of work has been done previously to determine which mechanisms are the main drivers of foam stability in nonaqueous fluids. Crude oils represent one set of nonaqueous fluids in which foaming has been studied extensively. In general, profoaming components in crude oils have been shown to contribute to foam stability by altering the air/oil surface rheology [32,38,187,188].
Effect of Elastic Contact Force on Tribological Characteristics of Current-carrying Roll Rings in Rotating Conductive Joints
Published in Tribology Transactions, 2023
Tianhua Chen, Chenfei Song, Zili Liu, Li Wang, Chao Sun, Xianjuan Pang, Yongzhen Zhang
The worn surfaces of the elastic rings after the tests were observed using an optical microscope, as shown in Fig. 5. A flake wear morphology was formed on the contact surface, and some material accumulation was observed along the edge of the contact surface. Because the sharp contact surface was at an initial right angle, the contact pressure could be sufficiently high to produce a strong surface rheology at the early rolling stage. Therefore, it was speculated that this type of plastic rheology occurs mainly during the run-in period. As rolling progressed, the contact surface expanded and became wider. It could be observed from Fig. 6 that a higher elastic force results in a larger wear width. The average wear widths were 288.52, 322.86, 356.12, and 378.79 μm as the elastic force increased. The expansion of the wear width could result in an increase in the contact area, which was beneficial for reducing the contact resistance. However, a large contact area could generally cause a higher friction force (17, 18). Therefore, the expansion of the contact area was not the reason for the decrease in the friction force at high elastic forces.
Estimating reservoir fluid interfacial tension: an insight into the role of polar species of crude oil
Published in Journal of Dispersion Science and Technology, 2022
Huaping Li, Sharath Chandra Mahavadi, Adrian Anton, Simon I. Andersen
It is well known that interfacial films between crude oil and water may solidify resulting in surface rheology and elasticity.[28] Observations of skin formation during pendant drop experiments such as that reported in crumpling experiments have been known for more than 4 decades.[44] We did not observe any film formation in the experiments reported herein, and we have previously shown that increasing content of a naphthenic acid will affect the film properties.[30] While we understand the importance of the film properties in the emulsion stability and the demulsification process there is no general understanding of how this impacts reservoir performance. However, it is highly unlikely that solid asphaltenic interfacial films abundantly exist in the reservoir rock matrix as this would severely impact the flow of oil and affect the reservoir rock properties.
Synergism between betaine surfactants under high-salt conditions
Published in Journal of Dispersion Science and Technology, 2022
Tianci Zhang, Jijiang Ge, Longjie Li, Hao Wu, Hongbin Guo, Jiawei Fan, Tao Zhang
So LHSB and OAB were selected to develop the heat-resistant and salt-tolerant foaming agents and investigate the synergism between the above two components. Betaine surfactants used in this study were provided by an industrial producer, there were some impurities in these commercially available products. The existence of impurities would disturb the investigation of surface properties (Foam properties, SFT, CMC, and surface rheology), so betaine surfactants (LHSB and OAB in this study) should be purified before the next step. The detailed purification procedure was described in the study of Ge J et al.[21] The chemical structures of LHSB and OAB are depicted in Figure 2.