Aggregation and gelation kinetics of fumed silica–ethanol suspensions

Smith, William E.; Zukoski, Charles F.

doi:10.1016/j.jcis.2006.09.016

Cited by 26 publications

(27 citation statements)

References 40 publications

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“…The decrease in gelation time at high temperature was attributed to larger Brownian motion of the particles resulting in faster collisions (Metin et al 2011). Similar results for gelation time were reported for silica particles suspended in ethanol by Smith and Zukoski (2006). Silica Concentration (wt%)…”

Section: Rheological Measurementssupporting

confidence: 75%

Phase behavior and rheological characterization of silica nanoparticle gel

2012

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Preferential injection into high permeability thief zones or fractures can result in early breakthrough at production wells and large unswept areas of high oil saturation, which impact the economic life of a well. A variety of conformance control techniques, including polymer and silica gel treatments, have been designed to block flow through the swept zones. Over a certain range of salinities, silica nanoparticle suspensions form a gel in bulk phase behavior tests. These gels have potential for in situ flow diversion, but in situ flow tests are required to determine their applicability. To determine the appropriate scope of the in situ tests, it is necessary to obtain an accurate description of nanoparticle phase behavior and gel rheology. In this paper, the equilibrium phase behavior of silica nanoparticle solutions in the presence of sodium chloride (NaCl) is presented with four phase regions classified as a function of salinity and nanoparticle concentration. Once the gelation window was clearly defined, rheology experiments of silica nanoparticle gels were also carried out. Gelation time decreases exponentially as a function of silica concentration, salinity, and temperature. Following a power law behavior, the storage modulus, G 0 , increases with particle concentration. Steady shear measurements show that silica nanoparticle gels exhibit nonNewtonian, shear thinning behavior. This comprehensive study of the silica nanoparticle gels has provided a clear path forward for in situ tests to determine the gel's applicability for conformance control operations.

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Section: Rheological Measurementssupporting

confidence: 75%

Phase behavior and rheological characterization of silica nanoparticle gel

2012

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“…1. Particle interaction via a hard-sphere (HS) potential with a short-ranged attractive part is widely used to model colloidal systems and gels (15,16,(27)(28)(29). The total packing fraction is ϕ tot and the range is set to λ = 1.03, a value often used in colloidal modeling (30,31) …”

Section: Resultsmentioning

confidence: 99%

Arrested demixing opens route to bigels

Varrato

Michele

Belushkin

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

107

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Understanding and, ultimately, controlling the properties of amorphous materials is one of the key goals of material science. Among the different amorphous structures, a very important role is played by colloidal gels. It has been only recently understood that colloidal gels are the result of the interplay between phase separation and arrest. When short-ranged attractive colloids are quenched into the phase-separating region, density fluctuations are arrested and this results in ramified amorphous space-spanning structures that are capable of sustaining mechanical stress. We present a mechanism of aggregation through arrested demixing in binary colloidal mixtures, which leads to the formation of a yet unexplored class of materials--bigels. This material is obtained by tuning interspecies interactions. Using a computer model, we investigate the phase behavior and the structural properties of these bigels. We show the topological similarities and the geometrical differences between these binary, interpenetrating, arrested structures and their well-known monodisperse counterparts, colloidal gels. Our findings are supported by confocal microscopy experiments performed on mixtures of DNA-coated colloids. The mechanism of bigel formation is a generalization of arrested phase separation and is therefore universal.spinodal decomposition | DNA-coated colloids | programmable interactions | amorphous self-assembly T he properties of a self-assembled material are ultimately controlled by the interactions among its building blocks and by the conditions in which they are prepared. It is by tuning these two properties that different structures can be obtained. Shortranged attractive colloidal systems, for example, can form crystals, two glasses of different origin, or gels. The latter have great technological importance. Colloidal gels find applications in synthetic colloid porous materials (1, 2), functionalization of surfaces and films production (3, 4), ceramics processing (5, 6), protein assemblies (7, 8), food science (9, 10), and soft matter (11, 12). Although they have been known for some time (13,14), it has only recently been understood that the colloidal gels arise as a result of arrested phase separation (15-18).The gels are characterized by a ramified amorphous spacespanning structure that is capable of sustaining mechanical stress. The colloidal density plays a crucial role in the aggregation and therefore in the resulting structure. At low densities, irreversible aggregation leads to fractal gels. At intermediate densities more compact porous structures are observed, whereas a homogeneous glass emerges when the solute occupies more than 50% of the volume (11,10,14,19).It has been proven that when colloidal particles are quenched into the gas-liquid phase separation region, gelation occurs as a consequence of dynamic arrest that interferes with phase separation (15, 18). After the quench, the system is thermodynamically unstable and strong density fluctuations set in, favoring the separation of the fluid into two ...

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“…2b are almost identical to those for the samples obtained by burning out the resin in the resininfiltrated sample. It is well known that the gelation of silica particles occurs in water and ethanol at room temperature [7,8]. Therefore, it was expected that some of the fumed silica contacted with ethanol might be aggregated during the infiltration process.…”

Section: Methodsmentioning

confidence: 99%

Effect of resin infiltration on fumed silica-based thermal insulations

Kim

Park

et al. 2010

Res Chem Intermed

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The thermal conductivities and the strengths of fumed silica-based thermal insulations prepared by the dry process and the resin infiltration method have been studied. Infiltration of the insulation samples prepared by dry processing of mixtures, consisting of fumed silica, ceramic fiber and a SiC opacifier, was performed to strengthen their binding structure. The high temperature thermal conductivities for the insulation samples obtained by the resin infiltration method were similar to those for the samples prepared by the dry process. On the other hand, the bending strengths for the former were superior to those for the latter. However, the resin-infiltrated samples were more brittle than the samples obtained by the dry process due to the occurrence of rigid bonding between the fibers and the infiltrated resin in the porous insulations. The thermosetting resin solution infiltration method appeared to be applicable to producing a dust-free fumed silica-based thermal insulation.

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Aggregation and gelation kinetics of fumed silica–ethanol suspensions

Cited by 26 publications

References 40 publications

Phase behavior and rheological characterization of silica nanoparticle gel

Phase behavior and rheological characterization of silica nanoparticle gel

Arrested demixing opens route to bigels

Effect of resin infiltration on fumed silica-based thermal insulations

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