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To expound the mechanisms responsible for the effect of electrolyte on the interfacial tensions (IFTs) of mixed solutions containing zwitterionic surfactant alkyl sulfobetaine (ASB) and anionic sur...

To expound the mechanisms responsible for reducing interfacial tensions (IFTs) in amphoteric and ionic surfactant mixed systems, the IFTs of mixed solutions containing alkyl sulfobetaine (ASB) and different ionic surfactants against hydrocarbons with different carbon numbers have been investigated by the spinning drop method. For cationic surfactants, the antagonistic effect for reducing IFT appears between cationic and ASB molecules because of electrostatic repulsion, which results in competitive adsorption. On the other hand, the synergistic effect will be observed in ionic and ASB mixed systems as a result of the mixed adsorption caused by the electrostatic attraction. The “chain length compatibility” between the anionic surfactant and ASB molecules leads to a stronger synergistic effect and further reduces IFT. However, “size compatibility” plays the crucial role, and only mixed solutions containing an anionic surfactant with a larger hydrophobic group can produce ultralow IFT against hydrocarbons. Th...

Open-cell foams consisting of interconnected struts are widely used in thermal applications such as volumetric solar receivers. The thermal performance of foams strongly relies on their radiative behaviors which intrinsically depends on the radiative properties of struts. This study proposed a feasible approach to determine the radiative properties of solid struts by a pore scale identification from a macro scale measurement. First, the normal-hemispherical transmittance and reflectance spectra of two nickel foams were measured by an experimental system. Second, a pore scale forward calculation was conducted by a combination of Monte Carlo Ray-tracing method and real foam structures obtained from micro-computed tomography technique. Last, an Adaptive Particle Swarm Optimization algorithm was adopted to retrieve the spectral reflectivity and specularity of nickel struts from the measured spectra. The results show that it is unreasonable to assume the reflection behavior of strut surface simply as either specular or diffused, and also, it is unreliable to assign the reflectivity of strut surface directly by Fresnel's law. Within the investigated wavebands 0.4–2.2 μm, the average reflectivity of nickel struts is 12% lower than that of a nickel mirror. The proportion of specular reflection at nickel strut surface is between 37%–52%, almost increasing with wavelengths.

Betaines and anionic-nonionic surfactants are suitable for applying in enhanced oil recovery (EOR) in the high-temperature and high-salinity reservoir conditions. We have used the spinning drop method to investigate the interfacial tension (IFT) values of alkyl carboxylicbetaine (ACB) and five types of anionic-nonionic surfactant (C14E3C, C16E3C, C18E3C, C18E5C and C18E10C) with different ethylene oxide (EO) numbers and different alkyl chain lengths against hydrocarbons and crude oil. Thereafter, under the same conditions, the IFT values of ACB and anionic-nonionic surfactant mixed solutions have also been investigated. The experimental results exhibit that for achieving ultralow IFT the proper hydrophilic-lipophilic balance (HLB) is prerequisite, but the tightness of the adsorption film is the key factor, which is controlled by the consistency of the spaces occupied at the oil side and the water side of an interface. This mechanism is so called “size compatibility”. The ultralow level IFTs have been reached during wider concentration ranges as the mixed systems against crude oil, which have not happened when the hydrocarbons are the oil phase. These phenomena demonstrate the strong synergistic effect among ACB, anionic-nonionic surfactant and natural surface-active materials, which is important for the development of high-temperature and high-salinity oil reservoirs.

High-temperature radiative properties of open-cell foams are relatively scarce due to measurement limitation. This study aims to numerically predict the volumetric radiative properties of irregular open-cell foams at high temperatures. The prediction is based on established relations which link the volumetric radiative properties to the structural parameters and/or component optical/radiative properties. Four typical foams are considered, including copper foams, nickel foams, zirconia foams and alumina foams. Former two are made of opaque metals, while latter two are made of semitransparent oxidized ceramics. For the four foams, the highest temperatures investigated are up to 1084 K, 1605 K, 1633 K and 2300 K, respectively. The variations of radiative properties with wavelength and temperature are analyzed. It was found that high temperature can strengthen radiation absorption inside metal and ceramic foams at most of wavebands. The temperature has almost no influence on the scattering phase function of metal and ceramic foams. Compared to copper foams, the nickel foams behave more absorbing at most of wavebands and temperatures. Alumina foams show an obviously forward predominance (asymmetry factor g > 0.4), and the fraction of forward scattering increases with increasing wavelength. Zirconia foams show a slight backward predominance (asymmetry factor g = -0.1) at short wavelengths, and a closely isotropic scattering was found at around wavelength λ = 7 μm. This study provides a feasible way to obtain the radiative properties of open-cell foams at high temperatures. Normal-normal transmittance and normal-hemispherical transmittance/reflectance of foams were measured at room temperature. The experimental results validate the numerical approach to obtaining radiative properties from analytical relations and bulk properties.