Amphiphilic Janus particles are successfully obtained via a powerful strategy combining diffusion-induced phase separation and magnetically driven dewetting. A large-area, amphiphilic monolayer is been formed via a self-assembly paradigm based on a synergy between the amphiphilicity, shape anisotropy, and external magnetic field. This functionality holds great promise for practical applications in intelligent coatings, anti-bioadhesion, and antifouling surfaces.

Emulsion stability is a fundamental determination for separation technologies. We use the critical electric field (CEF) and viscosity changes in DC electrorheological (ER) experiments in dynamic mode to establish the level of stability of water-in-crude oil emulsions previously studied through bottle tests. The CEF value corresponds to the value of electric field at which the current reaches 95% or larger of the plateau value. Our results show that CEF can be obtained through current measurements and viscosity drops resulting from emulsion structure breakdown, although viscosity changes are not always a good proxy of stability. This implies that electrorheology cannot be uncritically used for static stability determination of the CEF value. Emulsion structure breakdown is explored through rheological characterization before and after voltage sweeps have been performed. When the electric field applied is below the CEF value, the storage and loss moduli response, as well as viscosity, as functions of frequency are recovered. However, when the electric field is greater than the CEF value, the emulsion structure breaks down irreversibly.

The stability of water-in-oil emulsions is controlled by several interfacial mechanisms that include the oil film rheology between approaching drops and the resistance to rupture of drop interfaces or a combination of these two interfacial controls. Film drainage is mainly a function of the continuous phase rheology. Temperature is regulated to control the viscosity of the continuous phase and, hence, determine its effect on emulsion stability through film drainage, in contrast with interfacial resistance to rupture. In this study, one crude oil is used to formulate water-in-oil emulsions. Oil-water interfacial tensions are measured to gauge other interfacial changes with temperature. The influence of cation type in the aqueous phase, which have been determined to affect emulsion stability, is examined by comparing the stability of emulsions made with either purely monovalent or divalent aqueous solutions with the same overall ionic strength. Divalent cations in water contribute to form stronger emulsions than those produced with purely monovalent aqueous phase. The critical field value, used as proxy of emulsion stability, approaches a plateau value for NaCl emulsions and slowly decreases for CaCl 2 , at sufficiently high temperature (50 °C), which is interpreted here to reflect the intrinsic drop-coating film resistance to coalescence. Interfacial tension does not vary significantly with either aqueous phase composition or temperature. From the comparison with previous results using a less asphaltic oil, it is speculated that the drop coating film is composed of a fraction of asphaltenes, for the crude oil studied here.

Several researchers have proposed that mobility control mechanisms can positively contribute to oil recovery in the case of emulsions generated in Enhanced-Oil Recovery (EOR) operations. Chemical EOR techniques that use alkaline components or/and surfactants are known to produce undesirable emulsions that create operational problems and are difficult to break. Other water-based methods have been less studied in this sense. EOR processes such as polymer flooding and LoSal TM injection require adjustments of water chemistry, mainly by lowering the ionic strength of the solution or by decreasing hardness. The decreased ionic strength of EOR solutions can give rise to more stable water-in-oil emulsions, which are speculated to improve mobility ratio between the injectant and the displaced oil. The first step toward understanding the connection between the emulsions and EOR mechanisms is to show that EOR conditions, such as salinity and hardness requirements, among others, are conducive to stabilizing emulsions. In order to do this, adequate stability proxies are required. This paper reviews commonly used emulsion stability proxies and explains the advantages and disadvantage of methods reviewed. This paper also reviews aqueous-based EOR processes with focus on heavy oil to contextualize in-situ emulsion stabilization conditions. This context sets the basis for comparison of emulsion stability proxies.

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Exchange coupled bimagnetic core/shell nanoparticles are promising for emerging multiferroic and spintronic technologies compared with traditional, single-phase materials, as they deliver numerous appealing effects, such as large exchange bias, tailored coercivities, and tunable blocking temperatures. However, it remains a challenge to manipulate their magnetic properties via exchange coupling due to the lack of a straightforward method that enables the general preparation of desired composites. Here we report a robust and general one-pot approach for the synthesis of different kinds of bimagnetic core/shell nanostructures (BMCS NSs). The formation of highly crystalline and monodisperse BMCS NSs adopted a self-adaptive sequential growth, circumventing the employment of complex temperature control and elaborate seeded growth techniques. As a result of large lattice misfit, the presence of interfacial imperfections as an extra source of anisotropy induced diverse exchange coupling interactions in ferro-ferrimagnetic and ferro-antiferromagnetic systems, which had great effects on the improvement of the magnetic properties of BMCS NSs. We envision that this new strategy will open up exciting opportunities toward large-scalable production of such high-quality BMCS NSs, thereby greatly potentiating the prospective applications of nanomagnetic materials.

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