Dispersion Of Fumed Silica Research Articles

Anticorrosive self-stratified PDMS-epoxy coating for marine structures

Four self-stratified coatings were prepared by dispersion of titanium dioxide (TiO2) and hydrophobic fumed silica (SiO2) nanoparticles in polydimethylsiloxane (PDMS)-Epoxy mix separately and in combination. Incorporating a definite ratio of nanofillers in PDMS-Epoxy incompa ible polymer blend to form a single coat paint system with anticorrosive and improved hydrophobic properties by the self-stratifying process is the chief highlight of this research work. The appropriate characterization techniques like Fourier Transform Infrared (FTIR) spectroscopy in Attenuated Total Reflection (ATR) mode of the coatings top and bottom layers emphasized the intended stratification. The Field Emission Scanning Electron Microscopy (FESEM) displayed the morphology of the coated samples top and bottom layers and the existence of the intended stratification in the coatings cross-section. The PDMS-Epoxy coating inclusive of both the nanofillers exhibited improved hydrophobic nature, appreciable surface free energy, augmented adherence to the substrate and lesser shear force in pseudo barnacle strength test in terms of shear. This innovative formulation pertains to the application on underwater substrates with improved anti-biofouling properties.

Film formation behavior and mechanical properties of one-component waterborne crosslinkable polysiloxane/fumed silica nanocomposite coatings

One-component waterborne crosslinkable polysiloxane/fumed silica nanocomposite coatings were fabricated by mixing of vinyl dimethicone emulsion, hydrogen dimethicone emulsion, Karstedt catalyst capsules dispersion, and fumed silica dispersion. Effects of the type and content of fumed silica, catalyst dosage, and surfactant concentration on the film-formation and mechanical properties of the coatings were investigated. The hydrophilic fumed silica, Aerosil A380, with the largest specific surface area, endowed the coatings with the highest optical transparency (>80 %) and the best mechanical properties (e.g. elastic modulus: 0.95 MPa, tensile strength: 1.44 MPa, and elongation-at-break: 423 %). As the A380 content increased, the coatings exhibited descending and then ascending tack-free time, despite of catalyst dosage and surfactant concentration. The crosslinking density of polysiloxane matrix was less impacted by fumed silica if appropriate catalyst dosage was used. The fumed silica could hinder the coalescence of dimethicone droplets, hence, resulting in smooth, granular, and even porous surface of the cured films with increasing silica content. The mechanically reinforcing role of hydrophilic fumed silica for this waterborne coating was demonstrated. More surfactants and appropriate catalyst dosage favored for better mechanically reinforcing role. In addition, the nanocomposite films were breathable and thermally stable. They could potentially act as novel film-forming cosmetics, base materials carrying medicine for skin disease, and eco-friendly industrial coatings.

Study on the Low and High Strain Rate Behavior of Fumed Nano Silica Dispersions

Shear Thickening Fluids (STFs) are a special class of field responsive non-Newtonian fluids which exhibit transition from low viscosity to high viscosity state when they are subjected to shearing deformation above the critical shear rate (CSR). Due to this unique characteristic of STFs, these have found application in ballistics, especially in the development of special class of body armors called Liquid Body Armors (LBAs) which are lighter in weight and more flexible as compared to conventional heavy armours. Fumed silica (FS) is a rheologically significant material as it is a well known viscosity modifier owing to its fractal structure, and is generally used in paints, coatings, sealants, printing inks etc. In this study, two different grades of FS (A-130 and A-150) were used for the synthesis of STFs. The low strain rate studies were conducted on cone and plate rheometer and high strain rate experiments were accomplished on split Hopkinson pressure bar (SHPB) set up. The colloidal dispersions in PPG-400 (Poly Propylene Glycol 400) were synthesized using ultrasonic homogenization technique. From the experiments it was observed that A-150 fumed silica dispersion exhibited higher severity in shear thickening in the low strain rate domain, whereas A-130 fumed silica dispersion exhibited higher specimen stress and compressional strain rate under high strain rate dynamic compressive loading. Thus, it can be inferred that the same material may exhibit different behaviors in the low and high strain rate regimes. Therefore, both the studies play a vital role to completely characterize the material, especially when the material has to be subjected to ballistic applications.

Dynamic Properties on NMR Spectroscopy of Non-Aqueous Electrolyte Solution Coexisting with Fumed Silica Dispersion

In this study, the non-aqueous LiClO4 solution mixed with fumed silica as model system of LIBs was applied, and the dynamic properties and influences which solvent molecules received from solid phase or Li+ ion in using the NMR spectroscopy and the relaxation time(T1, T2 ) measurements were evaluated. The NMR signal of 1H in PC molecules is influenced by coexisting solid phase in LiClO4-PC solution /oxide powder. The dynamic property of the PC molecules drastically decreased in comparison with the system of the liquid only system. In IR spectra of PC/Alumina systems, the vibration in higher wavenumber range are predominantly observed due to indirect electron-donation from solid surface. The signal intensity depends on influenced liquid content from solid phase. Especially, the LiClO4-PC solution /alumina systems, the intensity is abruptly decreased due to widely spread influences of solid phases. Moreover, the influence from the solid phase to the PC molecules is much smaller than the water molecules from the 1H spin-spin relaxation time (T 2). As for the electrolyte concentration dependence, PC system was more remarkable than the water solution system, namely the network structure of the whole PC solvent is greatly affected by the addition of the Li+ ion, and it is thought that relaxation time largely decreased.

Quantitative nonlinear thixotropic model with stretched exponential response in transient shear flows

We propose a rheological model for ideal thixotropy, defined as a reversible time-dependent shear-thinning viscous response, in both shear-rate-controlled (RC Model) and stress-controlled (SC Model) forms. The model introduces a spectrum of structure parameters that collectively relaxes as a stretched exponential. It retains time-invariance symmetry with only a stretching exponent β as an additional model parameter relative to conventional single-structure-parameter models. The kinetic equations are nonlinear in both the structure parameters and the flow parameters of strain rate or stress. We demonstrate that introducing multiple structure parameters can successfully capture the stretched-exponential and nonmonotonic evolution of stress or shear rate in general step tests; and using nonlinear kinetic equations can explain the relaxation time's dependence on both the initial and final values of shear rate or stress in step tests. We present rheological data for a fumed silica dispersion in a number of shear histories including steady state, step shear rate, step stress, shear-rate ramp, and stress ramp. A systematic way to parameterize the models is provided. Both models fit experimental data well although the SC Model provides better agreement with the measurements. The ideal thixotropic models can be combined with existing methods that incorporate viscoelasticity so as to extend their validity into the region of low shear rates.

Dynamic Properties on NMR Spectroscopy of Non-Aqueous Electrolyte Solution Coexisting with Fumed Silica Dispersion

For various electrochemical devices in practical use, porous solid materials are widely fabricated for holding electrolyte solutions. It is reported that electrolyte solutions related to ion-solvent interaction indicate different properties by coexistence of solid phase[1], and an elucidation of liquid phase properties of solid-liquid interface in the non-aqueous electrolyte solution system is important for improving the performance of energy storage devices such as lithium ion batteries(LIBs). In addition, in late years the study of new electrolyte materials used highly-concentrated electrolytes attracts attention. Dahn et al.[2], report that highly-concentrated aqueous electrolyte solutions improve charge rate and wider overvoltage. It is also very important to investigate properties of the highly-concentrated electrolytes in aiming at the performance enhancement of LIBs. In this study, NMR spectroscopic behavior of non-aqueous LiClO4 solution mixed with fumed silica as model system of gel electrolyte for LIBs, and their dynamic properties and influences to solvent molecules from solid phase or Li+ ion by measurement of the spin-lattice(T 1) and spin-spin (T 2) relaxation phenomena. Samples were prepared in Ar glovebox by mixing propylene carbonate(PC) or LiClO4/PC of predetermined concentration (1-3 M) and fumed silica(FS) (200 ± 50 m2 g-1), amorphous silica nanoparticles with self-cohesive properties in NMR tube. A content of liquid phase were ranged from 90-100 vol% by gravimetry. We measured 1H and 7Li NMR spectroscopy (Varian INOVA 400; 9.39T) , spin–lattice relaxation time; T 1 measurements, and spin–spin relaxation time ;T 2 measurements (XiGo Nanotools Acorn area ; 0.3T). In 1H NMR spectra, little amount of solid phase (fumed silica) at around 1% affected to NMR signal which was deformed to the broadened band. It was shown that the dynamic properties of the PC molecules drastically decreased in comparison with the system of the liquid system only. Owing to the shielding effect to the 1H nucleus of the PC molecules by the surface charge of fumed silica, a signal continues to shift to higher magnetic field with the increasing of the solid-phase content without the depending on the LiClO4 concentration. This phenomenon also observed in the water solution system equally. From the calculation of the integrated intensity of the 1H NMR signals, that is the 1H qNMR analysis, in 90-100 vol%, the relatively slight influence in comparison with the aqueous-solid system which the hydrogen nucleus of propylene carbonate affected by fumed silica was observed. It is suggested that the influence from the solid phase to the PC molecules is much smaller than the water molecules from the 1H spin-spin relaxation time (T 2) as shown in Fig. 1. Dependences of T 1 and T 2 relaxation time on liquid content indicated that the interaction between the fumed silica surface and the PC molecules is much smaller than the case of the water molecules. On the other hand, as for the electrolyte concentration dependence, more remarkable variation was observed in the system containing PC rather than that of the aqueous system. Because the molar ratio of water molecules to Li+ ions is ca. 53 in 1 mol L-1 LiClO4 aqueous solution, the water molecule participating in the hydration to Li+ ion is a small portion, and most water molecules form a hydrogen bonding network. Whereas most PC molecules solvate with Li+ ion because the molar ratio of water molecules to Li+ ions is ca. 11 in 1 mol L-1 PC LiClO4 solution. Therefore the network structure of the whole solvent is greatly affected by the addition of the Li+ ion, and it is thought that relaxation time largely decreased. This result is supported from the increase of viscosity with the increase of the electrolyte concentration of the LiClO4/PC solution. Furthermore, from result of a measurements of the 7Li NMR and the Li+ ion conductance, it was shown that the interaction between the fumed silica surface and the Li+ ion in the PC solvent was smaller than in the water solvent. The details of the liquid phase properties in other solvents and the comparison with the PC system will be also reported in this research. This study was supported by the JST Core Research for Evolutional Science and Technology (CREST). 【Reference】 [1] M. Mizuhata et al., J. Mol. Liq., 83, 179, (1999). [2] Wu Li, J. R. Dahn, D. S. Wainwright, Science, 264, 1115, (1994). Figure 1

Direct Evidence for Percolation of Immobilized Polymer Layer around Nanoparticles Accounting for Sol-Gel Transition in Fumed Silica Dispersions.

Immobilized polymer fractions have been claimed to be of vital importance for sol-gel transitions generally observed in nanoparticle dispersions but remain a matter of debate regarding mechanism and difficulty for prediction. Here we investigate the immobilized layer structures of trifunctionality polyether polyol (PPG) near the surfaces of hydrophilic and hydrophobic fumed silica (FS) nanoparticles to reveal the role of surface chemistry on the molecular dynamics and sol-gel transitions of the dispersions. Using modulated differential scanning calorimetry, we measure the specific heat capacity during glass transition and the enthalpy during cold-crystallization. Comparing with hydrophobic FS that forms a fully immobilized (glassy) layer, we find that hydrophilic FS immobilizes more PPG, forming a partially immobilized outer layer being unable to crystallize next to the inner glassy layer. By correlating the thickness of the glassy layer with half of the minimum spacing between nanoparticles, we directly evidence the percolation of this layer along the nearest neighbor nanoparticles responsible for the sol-gel transition. Using effective volume fraction including the glassy layer, we successfully construct master curves of relative viscosity of both hydrophilic and hydrophobic FS dispersions, pointing to a common sol-gel transition mechanism mediated by the surface chemistry.

Adjustable rheology of fumed silica dispersion in urethane prepolymers: Composition-dependent sol and gel behaviors and energy-mediated shear responses

Variation of colloidal and interfacial interactions leads to a microstructural diversity in fumed silica dispersions exhibiting absolutely different sol- or gel-like rheological responses. In this study, fumed silicas with different surface areas (200–400 m2/g) and surface characteristics (hydrophilic or hydrophobic) are dispersed into moisture-cured polyurethane. The microstructures investigated using transmission electron microscope are associated perfectly with three different rheological behaviors: (i) Sols with well-dispersed silica aggregates, (ii) weak gels with agglomerate-linked networks, and (iii) strong gels with concentrated networks of large agglomerates. Though sols and gels are well distinguished by shear thickening or sustained thinning response through steady shear flow test, it is interesting that the sols and weak gels exhibit a uniform modulus plateau-softening-hardening-softening response with increasing dynamic strain at frequency 10 rad s−1 while the strong gels show a sustained sof...

Uniform Pores in Cross-Linked Polymers by Dispersed Fumed Silica Templating

Hydrophobic fumed silica dispersions in organic monomers were explored as a pore-forming system in polymer synthesis. The method developed provides a simple and effective way of controlling the pore size in highly cross-linked polymers. Fumed silica suspensions in divinylbenzene were polymerized with subsequent etching of the silica particles, therefore creating the porosity in the polymer. The resulting polymers are mesoporous materials, exhibiting an extremely narrow pore size distribution with an average pore size of about 100 angstrom, replicating the size of the nanofiller. BET surface areas were found appreciably high (similar to 350 m(2)/g). Furthermore, the rheological behavior of the prepolymerization mixtures was studied to elucidate the formation of the porous network and showed that a tridimensional network of particles is formed at a minimum silica fraction (Phi(v)) of 0.08. (Less)

Extensional rheology of shear-thickening fumed silica nanoparticles dispersed in an aqueous polyethylene oxide solution

In this paper, the shear and extensional rheology of fumed silica nanoparticles dispersed in an aqueous polyethylene oxide (PEO) solution is investigated. The role of particle concentration, polymer concentration, and polymer molecular weight on both the shear and the elongational behavior of the dispersions was examined. The fumed silica dispersions were found to strongly shear thicken. Increasing particle concentration was found to increase the degree of shear thickening. The effect of polymer concentration and polymer molecular weight on shear-thickening behavior was found to be nonmonotonic. The data showed a maximum in shear thickening at an optimum polymer concentration and molecular weight. Increasing the polymer concentration and molecular weight was found to reduce the critical shear rate for the onset of shear thickening. Linear viscoelastic measurements showed a qualitatively similar trend in the elastic modulus. Extensional rheology was conducted using a capillary breakup extensional rheometer. The dispersions showed strong strain-hardening behavior with thickening magnitudes similar to that observed under shear. The trends in the magnitude of extensional hardening with particle and polymer concentration were found to be similar to shear. In some cases, extensional thickening of nearly 1000 times was observed. However, in contrast to shear, increasing the molecular weight of the PEO corresponded to a sharp increase in extensional strain-hardening likely due to the role of polymer-induced elasticity which was shown to cause extensional hardening even in the absence of nanoparticles.

Rheological behavior and film characterization of fumed silica dispersion in carbodiimide based UV-curable coating material

Carbodiimide based UV curable coating materials, which were developed as a high refractive raw coating material, were prepared by dispersion with fumed silica inorganic particles in order to overcome low hardness and strength of the cured films. Three kinds of fumed silica particles were dispersed having various reactive surfaces, and the rheological behavior of the dispersions was observed. Compared to the hydrophilic silica (Si-hi) dispersion, two types of hydrophobic silica (Si-ho-n and Si-ho-a) dispersion showed sol behavior in high concentrations. In particular, the Si-ho-a dispersion showed viscous sol characteristics for high shear rates. The surface hardness of the film obtained by UV curing of the fumed silica dispersion increased in the more highly concentrated dispersion, and the haze of the film also increased. Further, the film was highly refractive.

A rheological study on temperature dependent microstructural changes of fumed silica gels in dodecane

The effect of temperature on colloid systems of hydrophobic and hydrophilic fumed silica in dodecane was investigated mainly by means of dynamic rheology. Dynamic frequency sweeps showed frequency-independent elastic modulus (G′), indicating the presence of gel networks in both dispersions. Dynamic temperature sweeps consisting of a heating and cooling cycle were also conducted. For the hydrophobic fumed silica gel, G′ slowly decreased with rising temperature owing to the increased particle mobility and decreased strength of hydrogen bonds due to the higher thermal energy. However, the hydrophilic fumed silica gel showed a rather unusual temperature dependent behavior involving a transition temperature (Tc) and an irreversible increase in G′ during the cooling cycle. This unusual behavior was believed to be related to the restructuring of nanoparticle chain aggregates (NCA) of fumed silica in gels as also revealed by FTIR results. Further analysis on this behavior showed that elevated temperature tended to increase the fractal dimension (Df) of aggregates, resulting in more compact NCAs and thereby a denser gel network with a higher G′. These results suggest that temperature is an important external variable that can be regarded as an optional simple way to tailor the viscoelastic properties and to control the microstructure of colloidal systems such as fumed silica dispersions in dodecane.

The Interaction of Gemini Surfactants C12-s-C12·2Br with Aqueous Suspension of Fumed Silica

The interaction of Gemini surfactant C12-s-C122Br with aqueous suspension of fumed silica have been investigated by DLS, Zeta potential, conductivity, pH value and fluorescence. With the increase of surfactant concentration, four regions exist during the adsorption and aggregation process, which can be recognized as ion exchange adsorption, electrostatic repulsion, adsorption layer formation by hydrophobic interactions and free micelle formation. The Gemini surfactant C12-s-C122Br shows strong adsorption ability on the fumed silica. Zeta potential was turned from negative to positive by the addition of small quantitates of C12-s-C122Br. The “dispersion-flocculation-dispersion” phenomena was observed for the addition of s=2 during 0.1 to 4 mmol L-1. 5% fumed silica dispersion system can be gelled by s=2 of 1mmol L-1. These phenomena have never been observed for the systems containing s=4 and s=6.

In vitro dentin permeability after application of Gluma® desensitizer as aqueous solution or aqueous fumed silica dispersion

ObjectivesTo assess and to compare the effects of Gluma® Desensitizer (GDL) with an experimental glutaraldehyde and HEMA containing fumed silica dispersion (GDG) on dentin permeability using a chemiluminous tracer penetration test.Material and MethodsTwenty disc-shaped dentin specimens were dissected from extracted human third molars. The dentin specimens were mounted in a split chamber device for determination of permeability under liquid pressure using a photochemical method. Ten specimens were randomly selected and allocated to the evaluation groups Gluma® Desensitizer as aqueous solution and glutaraldehyde/HEMA as fumed silica dispersion, respectively. Dentin disc permeability was determined at two pressure levels after removal of smear with EDTA, after albumin soaking, and after application of the desensitizing agents. Two desensitizer-treated and rinsed specimens of each group were examined by scanning electron microscopy (SEM) for surface remnants.ResultsComparatively large standard deviations of the mean EDTA reference and albumin soaked samples permeability values reflected the differences of the dentin substrates. The mean chemiluminescence values of specimen treated with GDL and GDG, respectively, were significantly reduced after topical application of the desensitizing agents on albumin-soaked dentin. The effects of GDL and GDG on permeability were not significantly different. Treated specimens showed no surface remnants after rinsing.ConclusionsThe experimental desensitizer gel formulation reduced dentin permeability as effectively as the original Gluma® Desensitizer solution.

Distortion of Single‐Particle Optical Sensing (SPOS) Particle Count by Sub‐Countable Particles

AbstractSingle particle optical sensing (SPOS) is a highly sensitive particle characterization technique for the measurement of the large particle (> 0.5 μm) tail of a submicron particle size distribution. We have examined the SPOS technique for fumed silica dispersions which have a mass mean particle size of ~140 nm. The reported large particle population varies as a highly non‐linear function of sample concentration and is accompanied by the distortion of the particle size distribution. A similar response is also demonstrated for monodisperse polystyrene latex spheres. The source of spurious particle counts and the distortion of the particle size distribution is shown to be secondary coincidence. Model calculations indicate that the primary contributors to spurious counts are particles near the peak of the size distribution. These particles are substantially smaller than the nominal minimum 0.5 μm diameter. These findings establish the limited range of reliability for SPOS measurements when used to measure a small fraction of the total particle size distribution and establish the need for new particle characterization metrologies.

Magnesium ion-conducting gel polymer electrolytes dispersed with fumed silica for rechargeable magnesium battery application

Effect of fumed silica dispersion on poly(vinylidene fluoride-co-hexafluoropropylene)-based magnesium ion-conducting gel polymer electrolyte has been studied using various physical and electrochemical techniques. The composite gel electrolytes are free-standing and flexible films with enough mechanical strength. The optimized composition with 3 wt.% filler offers a maximum ionic conductivity of ∼1.1 × 10−2 S cm−1 at ∼25 °C with good thermal and electrochemical stabilities. The Mg2+ ion conduction in the gel nanocomposite film is confirmed from the cyclic voltammetry, impedance spectroscopy, and transport number measurements. The space-charge layers formed between filler particles and gel electrolyte are responsible for the enhancement in ionic conductivity. The applicability of the gel nanocomposite to a rechargeable battery is examined by fabricating a prototype cell consisting of Mg [or Mg-multiwalled carbon nanotube (MWCNT) composite] and MoO3 as negative and positive electrodes, respectively. The discharge capacity and the rechargeability of the cell have been improved when Mg metal is substituted by Mg-MWCNT composite. The discharge capacity of the optimized cell has found to be ∼175 mAh g−1 of MoO3 for an initial ten charge–discharge cycles.

Characterization of Large Particles in Fumed Silica Based CMP Slurry

AbstractLarge particles in fumed silica dispersions were characterized by sedimentation, light scattering techniques, Transmission Electron Microscopy (TEM), and lacunarity. Applying centrifugation to fumed silica dispersions generated differences in sedimentation rates of large particles. The sedimentation rates of the large particles were affected by morphological differences and the particles remaining in the supernatant displayed buoyant behavior. The large particle morphology varied from branch like aggregates containing large primary particles to particles comprised of highly coalesced, tightly packed small primary particles. The results indicate the presence of different types of large particles in fumed silica dispersions to which conventional large particle characterization is unable to distinguish.

Aggregation, ageing and transport properties of surface modified fumed silica dispersions

We have investigated the aggregation, ageing and transport properties of surface modified silica dispersions in DMSO by photon correlation spectroscopy and conductivity measurements. The surface modification introduces Li+-ions that dissociate in the dispersion creating a single Li+-ion conducting electrolyte. We show that the surface modification changes the aggregation and ageing properties of the material. There is a pronounced ageing observed for the modified silica dispersions. At high concentrations of fumed silica a gel state is found, which in the case of the surface modified silica is a very weak gel that can be rejuvenated by ultrasonic treatment. The key parameter controlling the aggregation in this system is hydrogen bonding and the surface modification results in a very low number of sites for hydrogen bonding. In addition there is a contribution from repulsive electrostatic interactions in the surface modified silica dispersions due to the highly charged surfaces of these particles. Furthermore, the Li+-ion diffusion, at low silica concentration, is three orders of magnitude faster than that of the silica particles and in the gel state the silica particles are immobile. We also find that the Li+-ion diffusion is virtually independent of the silica concentration in the dispersions.

Improving Inkjet Print Performance with Fumed Silica at the Size Press

A very thin layer of a fumed silica based coating (0.5-1.0 g/m2) applied to plain paper at the size press improves inkjet printing performance. The silica coating behaves as an inorganic sponge with a well defined void and channel structure to absorb ink rapidly for enhancing color qualities, print uniformity and image resolution.The rapid drying of a print and immobilization of the ink colorant improves many performance aspects when using today's modern high speed printers. A paper with a size press treatment of fumed silica is a novel approach and a cost efficient solution to meet the requirements of tomorrow's printer design. The successful development of both cationic and anionic fumed silica dispersions at high solids content are an essential advancement towards this goal.

Viscoelastic Behavior and Ability of Dissipating Energy of SiO 2 Dispersions under Stress Shear

The viscoelastic behavior and the ability of dissipating energy of fumed silica dispersions in ethylene glycol, propylene glycol, and butylene glycol have been studied under oscillation stress shear. The systems show linear viscoelastic, shear thinning, and shear thickening behaviors as the shear stress (σ) increases. In linear viscoelastic region, the storage modulus ( G′) and loss modulus ( G″) remain unchanged; in shear thinning region, G′ decreases and the sequence of the decreasing degree of G′ is EG/SiO 2>PG/SiO 2> BG/SiO 2; however, G″ remains unchanged with σ increasing; in shear thickening region, both G′ and G″ increase as σ increases. The magnitude of G″ is larger than that of G′ over the studied range of stress, indicating that the dispersions mainly possess viscous property, and the energy dissipated is larger than the energy stored. The dissipated energies ( E d) of EG/SiO 2, PG/SiO 2, and BG/SiO 2 dispersions increase with the maximum strain (γ 0) increasing in a second power relation under low shear stress; however, in the shear thickening region, the E d of EG/SiO 2, PG/SiO 2, and BG/SiO 2 dispersions show an exponential increase with γ 0 increasing by the exponents of n=2.79, 4.93, and 4.88, respectively.