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Shake-gels are aqueous mixtures of silica and Poly(ethylene-oxide) (PEO) that form reversible gels when subjected to an applied force, such as shaking. This shear-thickening effect can be observed using a rheometer, which shows discrete, sudden changes in the material's viscosity. Preliminary qualitative investigations have shown that the gelation time varies depending on the conditions used. We also measure the time required for the gel to relax and revert to its liquid state. To quantify the relationships between these variables and better understand the process and kinetics, a systematic investigation was conducted, focusing on the effects of polymer concentration and temperature on gelation and relaxation times. Experiments were carried out using a rheometer with double-gap concentric cylinder geometry, applying a constant shear rate to samples with varying polymer concentrations and temperatures. The results showed that, at a fixed shear rate, gelation and relaxation times varied significantly, ranging from a few seconds to over an hour. Both gelation and relaxation occurred more rapidly as polymer concentration increased. Additionally, higher temperatures led to faster gelation and relaxation times and vice versa. [Display omitted] [ABSTRACT FROM AUTHOR]

Colloidal silica-filled deproteinized natural rubber (DPNR) grafted with poly(methyl methacrylate) (PMMA) (DPNR-graft-PMMA/silica) was prepared and characterized. DPNR-graft-PMMA/silica was prepared by graft copolymerization of NR latex with MMA and tert-butyl hydroperoxide/tetraethylenepentamine as initiators, followed by the addition of silica precursor, i.e., vinyltriethoxysilane (VTES). Various amounts of colloidal silica were introduced by varying VTES concentrations accordingly. The resulting DPNR-graft-PMMA/silica sample was analyzed through Fourier transformed infrared and nuclear magnetic resonance (NMR) spectroscopy. PMMA was successfully grafted on NR particles, and colloidal silica particles productively generated in DPNR-graft-PMMA latex. Properties of DPNR-graft-PMMA/silica, i.e., tensile strength and hardness, were significantly improved than those of DPNR. Low water contact angles of DPNR-graft-PMMA and DPNR-graft-PMMA/silica indicated the polar characteristic of colloidal silica and PMMA particles, enhancing the compatibility of those components in DPNR-graft-PMMA/silica. [ABSTRACT FROM AUTHOR]

Wet-mix shotcrete technology is widely used worldwide. One possible approach to developing this technology is the use of various admixtures to improve its pumpability and shootability. However, the commonly used slump test is insufficient to evaluate the capabilities of fresh shotcrete, because they do not assess the influence of multiple factors on its workability and placement properties. The purpose of this paper is to investigate and determine the effect of colloidal silica with a particle size of 10 nm (with 2%, 3%, and 4% replacement) on high-performance shotcrete from a rheological and mechanical perspective. In addition, to compare these indicators, silica fume is used with a 4% and 7% mixing rate. Rheological parameters such as torque viscosity and flow resistance of fresh concrete were evaluated using an ICAR rheometer, and the measured values were correlated with pumpability and shootability. The results of the study demonstrate that torque viscosity decreases and flow resistance increases with the increase in the percentage of colloidal silica. Similarly, silica fume increases flow resistance and reduces torque viscosity. These findings demonstrate the possibility of obtaining high-performance shotcrete with improved pumpability and shootability by employing more colloidal silica and silica fume. It was also established that these supplementary cement materials improve the strength and durability of shotcrete. [ABSTRACT FROM AUTHOR]

We combined a nickel–aluminum–zirconium complex hydroxide (NAZ) with colloidal silica as a binder to prepare a granulated agent for adsorbing heavy metals from aqueous media. Three samples with different particle diameters were prepared to evaluate the effects on the properties: small (NAZ-S), medium (NAZ-M), and large (NAZ-L). We confirmed the granulation of the prepared samples at a binder content of 25%. NAZ-S had the largest specific surface area and number of hydroxyl groups, followed by NAZ-M and then NAZ-L. Regarding the adsorption capacity, NAZ-S adsorbed the most chromium(VI) ions followed by NAZ-M and then NAZ-L. The binding energy of Cr(2p) at 575–577 eV was detected after adsorption, and the effects of the temperature, contact time, and pH on the adsorption of chromium(VI) ions were evaluated. We identified the following adsorption mechanism: ion exchange with sulfate ions in the interlayer region of the NAZ samples. Finally, the chromium(VI) ions adsorbed by the NAZ samples were easily desorbed using a desorption solution. The results showed that NAZ offers great potential for the removal of chromium(VI) ions from aqueous solutions. [ABSTRACT FROM AUTHOR]

Pile foundations in sands are susceptible to damage during earthquake-induced liquefaction. In the last decade, colloidal silica treatment in sand has been considered a novel technique to improve the properties of sand without disturbing the structure. The 1-g shaking table tests were performed in the current study to examine the liquefaction performance of the pile foundation in colloidal silica-treated sand. Colloidal silica treatment considerably reduces the pore water pressure ratio of sand. Moreover, the ground surface remained intact after shaking, and a minimal settlement was noticed in the case of all the relative density samples treated with colloidal silica. The colloidal silica ground improvement method is suitable to mitigate liquefaction damages during shaking events in sandy soils and guarantees the protection of structures during earthquakes and other shaking events. It is important to analyse the influence of water on the strength in order to get more insights into colloidal silica stabilised sites. The water table fluctuations of the field might change the strength of sand stabilised using weakly cemented colloidal silica. So, the current study also aims to demonstrate the effect of variations in strength with the fluctuation of the water table in colloidal silica-treated sand. Treating the sand layers with an optimal amount of colloidal silica reduces pore water pressure ratio and settlement in all relative density samples. The treatment with colloidal silica slowdowns the maximum settlement time for all the tests conducted. [ABSTRACT FROM AUTHOR]

Nanotechnology has been with us as a science since the first nanoscale features were observed under a microscope. Nanotechnology is an emerging technology and one of the key components of the technological advances of the present century. The use of materials with nanometer-based structures has led human knowledge to develop and provide solutions to produce superior products in the future. With the advent of modern nanotechnology and the study of the unique properties of nanoparticles, the field of their use was provided in many branches of engineering, of which geotechnical engineering is no exception. In this paper, while introducing colloidal silica nanoparticles and their gelation, study on the important characteristics and effect of this type of nanoparticles on sandy soils properties will be discussed. In fact, we discussed previous studies on the use of colloidal nano silica in sandy soil, their properties, their effects on soil, and the equipment used in nanotechnology. The current review is an attempt to summarize the applications of nanotechnology in geotechnical engineering. Furthermore, this paper plans a comprehensive review on characteristics of colloidal nano silica, its effect on curing approaches and aging, its behavior upon the addition with sandy soil in terms of strength improvement, liquefaction potential, cyclic properties, hydraulic conductivity, and compressibility. Lastly, the optimal percentage of nano silica for various purposes was presented. [ABSTRACT FROM AUTHOR]

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Improvement of saturated loose sand in developed sites which are susceptible to liquefaction phenomena requires passive stabilization. Colloidal silica, whose nanoparticles have a superficial charge and could be mobile by a small driving force, has been used for this kind of soil improvement. This study investigated the effect of an electric field in colloidal silica injection in Firouzkooh sandy soil by creating coupled electric and hydraulic flow. With establishing a direct electrical field in a soil sample, the influence of electrophoretic on introducing nanosilica particles in the sand sample was evaluated against the hydraulic flow. The unconfined compression strength of the injected specimens was evaluated. The experiments were carried out on two different grain size distributions of sand. The silica grouts with 10% and 30% of colloidal silica by weight were injected under the electric gradients of 1.5 v cm and 2 v cm . In addition, two other types of grouts with ionic strength of 0.1 was also investigated, and all the grouts pH was adjusted at 9. The results show that the samples with salination and higher ionic strength did not meet stabilization. In contrast, the strength of other specimens increased, making the electrophoretic mobility much more dominant than the hydraulic regime. Also, a comparison between two different grain size distributions shows that the smaller the soil grain size, the greater the unconfined compressive strength of the soil. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of the fouling of a ceramic membrane by a mixture containing high concentrations of humic acid and colloidal silica during cross-flow ultrafiltration under various operating conditions. Two types of feed water were tested: feed water containing humic acid and feed water containing a mixture of humic acid and colloidal silica. The colloidal silica exacerbated the fouling, yielding lower fluxes (109–394 L m−2 h−1) compared to the humic acid feed water (205–850 L m−2 h−1), while the retentions were higher except for the highest cross-flow rate. For the humic acid feed water, the irreversible resistance prevails under the cross-flow rate of 5 L min−1. During the filtration of an organic–inorganic mixture, the reversible resistance due to the formation of a colloidal cake layer prevails under all operating conditions with an exception. The exception is the filtration of the organic–inorganic mixture of a 50 mg L−1 humic acid concentration which resulted in a lower flux than the one of a 150 mg L−1 humic acid concentration under 150 kPa and a cross-flow rate of 5 L min−1. Here, the irreversible fouling is unexpectedly overcome. This is unusual and occurs due to the low agglomeration at low concentrations of humic acid under a high cross-flow rate. Under lower transmembrane pressure and a moderate cross-flow rate, fouling can be mitigated, and relatively high fluxes are yielded with high retentions even in the presence of nanoparticles. In this way, colloidal silica influences the minimization of membrane fouling by organic humic acid contributing to the control of in-pore organic fouling.

The response of sands stabilized with colloidal silica aqueous gel is investigated in the laboratory. The role of colloidal silica on subsequent sand behavior is examined with the aid of monotonic and cyclic loading tests so as to establish the mechanical response of the treated sand. Depending on the loading conditions when the strength of the treated sand is enhanced and liquefaction is averted, its stiffness may reduce and its compressibility increase. This contradictory behavior is investigated on the basis of an extended database including direct shear, triaxial, and normal compression tests. Initial stiffness is lower for treated sand compared with untreated sand under drained and undrained monotonic loading conditions. It is demonstrated that only dense treated sand shows similar stress-strain properties with the untreated sand under cyclic loading, whereas loose treated sand accumulates strain and excess pore-water pressure much faster than the untreated sand. The critical state line applying to the treated sand lies substantially above that manifested by untreated sand. The two lines converge as the stress level increases to around 2,000 kPa. [ABSTRACT FROM AUTHOR]

Alumina‐based, porous filter media was made via a binder jet 3D printing process consisting of an alumina powder printing step with subsequent heating, colloidal silica infiltration, drying, and sintering to consolidate particles yet retain a net open porous microstructure. The composites made were alumina‐silica or alumina‐mullite, where the silica sintering aid was used to densify and join the alumina particles. The resulting composite structures had open porosities in the 25–31 vol% range as measured by Archimedes density. Pressure drops were measured across the filter media at constant flow rates to compare disc shapes and complex, 3D printed filters based on the N95 design requirements. Complex, 3D‐printed alumina composites were produced with acceptable pressure drops for N95 implementation. [ABSTRACT FROM AUTHOR]

Magnesium hydroxide (Mg(OH) 2) suspensions are encountered in the nuclear industry as legacy waste that is to be packaged for long-term storage. It is desirable to increase the solids content of the waste to minimize the total volume, yet this would produce high yield stress fluids that are difficult to process. However, high solids content suspensions of low yield strength are desired. Blending nano-silica (nano-SiO 2) into a high yield stress suspension of 27 vol% Mg(OH) 2 , the suspension yield stress was reduced from 86 Pa to 47 Pa. X-ray CT imaging revealed that approximately two-thirds of the 3 vol% nano-SiO 2 added to the Mg(OH) 2 suspension was well-dispersed, with the rest forming large clusters that had minimal interaction with the Mg(OH) 2 network. SEM images showed small aggregates/individual particles of nano-SiO 2 dispersed between Mg(OH) 2 particles. We conclude that the finely dispersed nano-SiO 2 act like ball bearings to lubricate contacts between the irregularly shaped Mg(OH) 2 particles, thus decreasing yield stress. When aging the samples for several days, the yield stress of the binary suspension increased, reversing the yield stress reduction that was observed within the first day. The network stiffening is attributed to the formation of magnesium silicate hydrate (MSH) due to a reaction between soluble Mg2+ and Si(OH) 4. The MSH precipitates onto the nano-SiO 2 to fuse particles together, thus reducing their effectiveness as flow modifiers. While this is a side effect of this particular binary suspension, the initial yield stress drop remains encouraging to provide the desired fluid conditions to process legacy wastes. [Display omitted] [ABSTRACT FROM AUTHOR]

Significant challenges remain for the remediation of chlorinated-solvent plumes in groundwater, such as trichloroethene (TCE) and tetrachloroethene (PCE). A novel slow-release permanganate gel (SRP-G) technique may show promise for the in-situ treatment (remediation) of chlorinated contaminant plumes in groundwater. A series of laboratory experiments were conducted to characterize the primary physical factors that influence SRP-G gelation processes to optimize SRP-G performance for plume treatment. Specifically, experiments were conducted to quantify gel zeta potential, particle size distribution, and viscosity to determine SRP-G gelation characteristics and processes. These experiments tested various concentrations of two SRP-G amendment solutions (NaMnO 4 and KMnO 4) prepared with 30-wt.% and 50-wt.% colloidal silica to determine such influences on zeta potential, particle size distribution, and viscosity. The results of this study show that SRP-G solutions with low zeta potential and relatively high pH favor more rapid SRP-G gelation. The concomitant interaction of the predominantly negatively charged colloidal silica particles and the positively charged dissociated cations (Na+ and K+) in the SRP-G solution had the effect of stabilizing charge imbalance via attraction of particles and thereby inducing a greater influence on the gelation process. Gel particle size distribution and changes in viscosity had a significant influence on SRP-G solution gelation. The addition of permanganate (NaMnO 4 or KMnO 4) increased the average particle size distribution and the viscosity of the SRP-G solution and decreased the overall gelation time. SRP-G amendments (NaMnO 4 or KMnO 4) prepared with 50-wt.% colloidal silica showed more effective gelation (and reduced gelation time) compared to SRP-G amendments prepared with 30-wt.% colloidal silica. Under the conditions of these experiments, it was determined that both the 7-wt.% NaMnO 4 solution and 90 mg/L KMnO 4 solution using 50-wt.% colloidal silica would be the optimal injection SRP-G solution concentrations for this in-situ treatment technique. [Display omitted] • Slow-release permanganate gel (SRP-G) solution was unstable at low zeta potential and relatively high pH. • Increase in permanganate concentration caused decreasing gelation time for the SRP-G solution. • Gelation time decreased with increases in SRP-G solution viscosity. • SRP-G solution is a promising technique for in-situ chlorinated plume treatment in aquifers. [ABSTRACT FROM AUTHOR]

The volume fraction dependent morphological transition of droplets during the evaporation of colloidal silica solution was investigated using the spray-drying method. The colloidal solution was prepared from sodium silicate using the sol-gel method. Spray drying with a tubular reactor was used in the experiment, with the volume fraction of the colloidal silica varying from 15 to 2%. It was demonstrated that a morphological transition from a sphere shape to a donut-like shape takes place at a colloidal volume fraction of between 4% and 2%, even when the drying rate remains moderate and is not extremely fast. A spherical silica particle shape was found at a colloidal volume fraction of between 15% and 8%. The morphological transition depends strongly on the volume fraction of the colloids in the droplets. Further, the ?-potential of the particles in the droplet also affects the transition by applying an interparticle electrostatic force. The same high surface charge of sol silica provides a repulsive interaction between the sol particles inside the droplet. The transition is hindered when the colloid volume fraction is increased because of the inherent spatial constraint. The Fourier-transform infrared (FT-IR) spectra of both the spherical and donut-like particles confirm the chemical bonding of the powder silica product. Moreover, X-ray diffractometry (XRD) analysis revealed an amorphous phase of the silica particles produced from spray drying. These preliminary results open up a new path for controlling the formation of a wide variety of silica particles using the spray-drying method. In addition, the different silica particle morphologies enable a variety of particle applications.

Colloidal silica is usually used for the chemical mechanical polishing of zirconia ceramic wafer in industry, but the process is often optimized only through experience without a precise understanding of the polishing mechanism. There are still many theoretical and technical issues, especially the material removal mechanism and the effect of polishing on the phase transformation, have not been studied in depth. In this study, the effect of the abrasive concentration, polishing pressure and slurry pH on the material removal rate was analyzed. It is found that the removal rate tends to be stable when the concentration exceeds 30 wt%; the influence of pressure on the polishing rate conforms to the Preston formula. When the pH of the slurry is 6, the removal rate is the highest, but polishing under acidic conditions will leave corrosion pits due to the dissolution of the stabilizer. Through X-ray photoelectron spectroscopy analysis of the residue on the wafer surface, it was found that Si-O-Zr bonds were formed, but it was uncertain whether the residue was zirconium silicate. Through X-ray diffraction analysis, it is found that polishing will not affect the crystal structure of zirconia. The Zr-O-Si bond formed by tribochemical action on the ceramic surface prevents the deep migration of surface hydroxyl groups. At the same time, kinetic factors will cause internal hydroxyl groups to transfer to the surface for recovery oxygen vacancies, thereby stabilizing the tetragonal phase. [ABSTRACT FROM AUTHOR]

Settlement during an earthquake occurs due to the permanent change in volume, which reduces the shear strength of the soil. Reduction of shear strength in soil leads to considerable damage in pile-supported structures due to the generation of extra lateral loads to piles by lateral movement of loose soil. Tests were carried out to examine the behavior of the pile foundation in colloidal silica treated sand under the application of vertical, lateral, and combined loading conditions at different initial relative densities. Dry sand (untreated), fully saturated sands (untreated), and colloidal silica treated sands were used to examine the property enhancement of colloidal silica sand under different load conditions. PLAXIS 3D geotechnical professional software was used for the numerical analysis of the tests mentioned above. The soil parameters, as well as the pile considerations which were obtained from the laboratory, were used in the present analysis. The numerical results obtained from the investigations were similar to the experimental test results for all the loading cases. Colloidal silica stabilization in sand increases the vertical, lateral, and combined loading capacity of the pile. The pile bending moment of the colloidal silica treated sands was lower than untreated sands. Results indicated that colloidal silica treatment could be an effective ground improvement technique to enhance the vertical and lateral load-carrying capacity of the pile. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride/SiO2/glass fiber mixtures were calcined at 650 and 850°C and the resulting materials were used to improve the through‐plane thermal conductivity of a polypropylene (PP) composite. The mixtures were characterized using Fourier transmission infrared spectroscopy, X‐ray photoelectron spectroscopy, and scanning electron microscopy. At 850°C, the glass fiber surface was largely covered by hexagonal boron nitride. A significant improvement of through‐plane thermal conductivity of PP composite was observed after the addition of hexagonal boron nitride/SiO2/glass fiber calcined at 850°C. Calcination temperature and the presence of glass fiber strongly affected the through‐plane thermal conductivity of the composite. [ABSTRACT FROM AUTHOR]

Hierarchical micro/mesoporous carbons obtained by template carbonization were investigated by nitrogen adsorption/desorption and gave a type IV isotherm with a H1 hysteresis loop closing perfectly near P/P 0 = 0.6. When using the 2D-NLDFT theory to calculate the pore size distribution (PSD) from the adsorption branch of the isotherms, while assuming slit pores with a heterogeneous rough surface (2D–HS–SLIT model), an unexpected artifact was observed ca. 3.5 nm. Recognizing that the H1 hysteresis loop is usually related to the adsorption in materials with cylindrical pores, where in general it is recommended to use the desorption branch for the pore size analysis, we have applied the 2D–HS–SLIT model to the adsorption isotherm up to P/P 0 = 0.2 and a cylindrical pore model to the desorption isotherm down to P/P 0 = 0.2. Interestingly, the application of this dual shape pore model to hierarchical micro/mesoporous carbons of various mesopore sizes and oxygenated surface functionalities shows an excellent fit with the experimental isotherms, while the mesopore peak in the PSDs is narrower, and the previously labeled artifact is eliminated. It is noteworthy that the cumulative surface area values are significantly larger than when applying the 2D–HS–SLIT model, what is due to the larger surface area of cylindrical than slit-shaped mesopores. [Display omitted] [ABSTRACT FROM AUTHOR]

Shear thickening behavior in colloidal dispersions occurs at a wide range of shear rates and concentrations. Using a small gap, parallel plate rheology allows access to shear rates up to 200,000 s−1. Fumed silica suspensions exhibited irreversible shear thickening at critical shear rates above 10,000 s−1, which depended strongly on silica concentration. Introducing 10 nm and 110 nm spherical silica particles to 180 nm fumed silica solutions resulted in increasing the critical thickening shear rate along with reducing the magnitude of thickening. The introduction of sufficient spherical particles to the fumed silica solutions via particle addition at 2 wt% or particle replacement at 7 wt% resulted in no shear thickening or formation of agglomerates. Although shear thickening was tuned by varying the concentration and particle size of spherical silica; hysteresis, i.e., the irreversibility of thickening, remained. In addition, rheo-small-angle light scattering measured the formation of agglomerates greater than 1 μm after shear thickening. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis and characterization of Zirconium(IV) Propoxide (ZTP), Colloidal Silica (CS), and Methyltrimethoxysilane (MTMS)-derived non-stick hard coatings prepared via the sol–gel method. In the synthetic procedure, two different solutions were prepared separately based on the different hydrolysis rates of the silicon (SolS) and zirconium (SolZ) components. Polydimethoxysilane (PDMS) and Fluoralkylsilane (FAS) were used as hydrophobicity-promoting agents. The solution was applied onto aluminum surface, which was afterward dried and densified at 250 °C. The final solution was characterized by FTIR spectroscopy to determine the Zr–O–Si hetero-bonding and Si–O–Si and Zr–O–Zr homo-bonding. Coatings were analyzed by their hardness, hydrophobicity, and gloss. A homogeneous solution and crack-free hybrid coating was obtained. FTIR results showed that homo- and hetero-bonding between Zr and Si elements were obtained from a precipitation-free solution. Measured contact angles varied between 100° and 112°, and these results were evaluated according to the surface and gel structure. Highlights: A crack-free, hydrophobic, hard hybrid thin films were synthesized using ZTP, MTMS and CS via sol–gel method. ZTP increased the contact angle of the film surface. Precipitation-free SolS solution was obtained due to the reactions between methyl groups in MTMS and the colloidal silica particles. PDMS and FAS components further increased the wetting angle of the hybrid film up to a specific ratio. FTIR results showed that Zr–O–Si hetero-bonding and Si–O–Si, Zr–O-Zr homo-bonding were obtained as result of the precipitation-free solution. [ABSTRACT FROM AUTHOR]

Liquefaction mitigation in already existing sites has become a cause of concern for geotechnical engineers across the world. One of the possible solutions for such sites is the recently developed technique called colloidal silica grouting. The technique utilises the slow injection of colloidal silica grout at the edge of the location through injection wells and delivers it to the required location through natural groundwater flow. Later, silica particles gel and bind the soil particle together by changing the pH that, in turn, increases the strength and rigidity of loose soil. The test results obtained from the laboratory and field studies are promising and feasible to recommend colloidal silica as a potential grout material for various soil engineering applications. The present review explains the use of colloidal silica stabilisation for ground enhancement and discusses the treatment method, together with the gelation and significant factors affecting the gel formation. The current paper reviews the tests performed in colloidal silica treated soil to determine the mechanical properties, hydraulic conductivity, and evaluation of liquefaction potential. Scanning electron microscopy analysis of colloidal silica treated soil was also included to explore the microstructural bonding of soil grouted with colloidal silica. Also, the advantages and challenges of colloidal silica grouting techniques in ground improvement are included in the study. Furthermore, future research scope of colloidal silica treated soil in unexplored areas is also mentioned based on the current literature review. [ABSTRACT FROM AUTHOR]

Four different consolidants for adobe buildings conservation were synthetized and evaluated. Adobe bricks materials tested from several Mining Haciendas of the seventeenth and eighteenth centuries located in Guanajuato, Mexico; these materials were characterized using XRD analysis, granulometry, porosity, moisture content, and mechanical resistance. The four consolidants synthetized are formulations based on TEOS (F1); TEOS with silica nanoparticles (F2); TEOS with PDMS-OH (F3) and hybrid consolidant formed by TEOS, PDMS, and nanoparticle silica (F4). The consolidants were tested and evaluated by porosity changes, absorption, and durability. The results show that colloidal silica improves the fulfill porosity by TEOS gels and the PDMS improves the flexibility on TEOS gel avoiding the crack. Thus, the addition of both components to TEOS gel results as an excellent consolidant treatment to adobe materials. Highlights: TEOS and different additives are proposed as adobe conservation treatment. Mechanical resistance increases according to the additive consolidant treatment. The different additives shown different penetration capacity that modify the consolidant process. PDMS additive increases the chemical stability on TEOS consolidant. [ABSTRACT FROM AUTHOR]

The relative mobility of weakly- and strongly-bound portions of hydrophobe-capped ethoxylate surfactants leads to discrepancies in NMR signal intensity which, surprisingly, increase with temperature. Nonionic surfactants have been widely used for many consumer products and industrial processes, and their applications often involve temperature-cycling across cloud point temperature (T cloud). To explore the behavior of nonionic surfactants across T cloud and when mixed with colloidal silica at a very dilute concentration around 0.1 wt%, a series of 1,2-epoxybutane-capped alcohol ethoxylates (BAEs) with various cloud points is used as a model system. BAEs with cloud points from 15 to 64 °C were successfully prepared by varying the lengths of 1,2-epoxybutane (BO) and ethylene oxide (EO) blocks and their phase behavior across T cloud was studied using nuclear magnetic resonance spectroscopy (NMR), dynamic light scattering (DLS) and differential scanning calorimetry (DSC). In the absence of silica, the NMR signals are not greatly affected by the cloud point transition, but both the water and surfactant exhibit a decrease in spin-spin relaxation time once the temperature reaches the T cloud. In the presence of silica, the NMR spectra indicate significantly reduced mobility of the EO portion relative to the alkyl and BO segments. Furthermore, our results suggest that the BAE surfactants are not fractionally clouding out or precipitating with a portion of the compositional distribution during the cloud point transition. [ABSTRACT FROM AUTHOR]

Organic-inorganic hybrid coatings were developed via a sol-gel method using hexagonal boron nitride (h-BN) as a ceramic filler material incorporated into a polymeric matrix. To investigate the effects of h-BN on the properties of polymer-based coatings, parameters such as hardness, coefficient of friction, and hydrophobicity were investigated. Colloidal silica (CS), methyltrimethoxysilane (MTMS), water, and acid catalyst containing coatings were prepared by varying the content of h-BN from 10% to 25%. All the coatings were prepared with the same experimental procedure and coated on 1050 aluminum alloy plates. The compensating contents of MTMS and colloidal silica with a fixed molar ratio of MTMS and CS were set to be 1:1.2, and a specific amount of the catalyst was utilized. Coatings were examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and energy-dispersive X-ray spectroscopy (EDS). The most promising physical properties were determined to be the pencil hardness of 8B, adhesion strength of 5B, coefficient of friction of 0.332 N, and water contact angle of 114.75°. Therefore, it can be concluded that the h-BN improves the physical properties of polymeric coatings. In addition, this study demonstrates the effect of h-BN on the adherence of polymer matrix-based hybrid coatings. [ABSTRACT FROM AUTHOR]

To get the controlled size and monodispersed silica nanoparticle is a popular topic since its broad applications are in a lot of fields such as biological medicine, military project, catalyst, and chip industry. The Stöber process was often used to prepare silica nanoparticle because of its low cost and easy operation. Here, the combined method of microchannel and microwave was proposed to accelerate the rate of both nucleation and growth reactions, which is important to the dimension and uniformity of the monodispersed silica nanoparticle. It was found that the particle size ranging from 15 to 400 nm was achieved by varying the concentration of TEOS and NH4OH with the combined method of microchannel-mixed (MC) and microchannel-microwave (MM). X-ray powder diffraction, Fourier transform infrared spectroscopy, dynamic light scattering, and scanning electron microscopy were used to characterize all the particles. Compared with the MC way, it showed a larger particle size and narrower distribution under the same operating condition experiment with the MM method due to the higher reaction rate of the nucleation and growth. When the concentration of NH4OH is 0.2 M, the size range of produced particles for the MC method is 17.7–28 nm comparing to the MM method is 151–213 nm. Besides, the higher yield of the silica nanoparticles was obtained by the MM method than the MC way because of the better mass and heat transfer. When the concentration of TEOS is 0.25 M, the yield of silica produced by the MC method is 70–77% comparing to the data of 87–92% by the MM combined method. The results of this paper may have important implications for developing the productivity of the industry. Highlights: Fast and continuous synthesis of silica nanoparticles by microchannel-microwave combined method for the first time. Two methods (the microchannel-mixed method and microchannel-microwave method) were investigated and compared in different concentrations of TEOS and NH4OH. The particle size was larger and better distributed by using the microchannel-microwave method than that of the microchannel-mixed method under the same operating condition. The higher yield of the silica nanoparticles was obtained by the microchannel-microwave combined method. [ABSTRACT FROM AUTHOR]

Colloidal silica as nanostructured binder for refractory castables has attracted many attentions in recent years. In the present study, phase composition, microstructure and reactivity evolution of silica gel at different heating conditions were investigated to find suitable system for colloidal silica application. The results showed that atmosphere and carbon slightly affected phase composition of the silica gel at elevated temperatures, and the crystalline phases were composed of major α-cristobalite and minor α-tridymite. The morphology and particle size of the silica gel were greatly affected by atmosphere and carbon during heating. The spherical nano-silica particles with sizes of 40–50 nm rapidly grew into macroscale rod-like particles with temperature increasing from 800-1000 °C to above 1200 °C in air, and sintering of silica particles was observed. However, the size and morphology of the spherical nano-silica particles retained at high temperature in a reducing atmosphere, and many well developed columnar mullite crystals and some SiC whiskers formed on heating silica gel, alumina fines and carbon at 1500 °C, which was due to carbon inclusions retarding the growth of nano-silica particles and the nano silica remained high reactivity at high temperature. Thus, colloidal silica was suitable for application in carbon-containing refractory castables. [ABSTRACT FROM AUTHOR]

This contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial effect of seawater was reflected in an improvement in compressive strength for up to 14 days of hydration, while in the 28 days compressive strength values were comparable to that of cement pastes produced with demineralized water. The combination of seawater and NS significantly promotes cement hydration kinetics due to a synergistic effect, resulting in higher calcium hydroxide (CH) production. NS can thus react with the available CH through the pozzolanic reaction and produce more calcium silicate hydrate (C-S-H) gel. A noticeable improvement of strength development, as the result of the synergistic effect of NS and seawater, was therefore observed. In addition, mercury intrusion porosimetry (MIP) tests confirmed significant improvements in microstructure when NS and seawater were combined, resulting in the production of a more compact and dense hardened paste structure. The optimal amount of NS to be mixed with seawater, was found to be 3 wt% of cement. [ABSTRACT FROM AUTHOR]

Solvent extraction (SX) is one of the most widely applied hydrometallurgical processes in copper production from oxide ore. As the high-grade ore deposits have been developed and depleted, now only low-grade ore deposits are being developed and are therefore facing obstacles of extreme processing conditions. This results in leaching gangue minerals and requires a more complicated solvent extraction system. Recently, synergistic solvent extraction has been introduced to separate copper from the leached solution with high impurities. However, operational obstacles arise due to the complicated solvent extraction process, including multi-stages of extraction, and using more than one extractant in a single solvent extraction system. The phase separation in solvent extraction is one of the major issues in field operation. A poor phase separation could affect the entire process and eventually cause production loss. Therefore, in this study, the phase separation behaviours were studied in consideration of the field operation. Major parameters considered in the study were the type of diluent, temperature, mixing speed, solution pH and Oxidation Reduction Potential (ORP), and addition of impurities (flocculant and colloidal silica). The phase separation behaviours in the continuous counter-current SX system using a pilot-scale mixer-settler in the above conditions was investigated.

Colloidal silica (silica sol) nanoparticles were synthesized by ammonia- and hydrochloric acid-catalyzed hydrolysis of tetraethoxysilane with subsequent condensation and polymerization. Silica particles with the size of 12‒160 nm were obtained at different temperatures and ratios of the initial reactants and studied by means of TEM, AFM, IR spectroscopy and zeta-potential measurements. The reaction conditions providing the minimum particle size in the final product of the most complete hydrolysis were determined. At pH above 8.5, an increase in the SiO2 content of the sol to 23 wt.% did not change the particle size. At a low (~ 1.8 wt.%) SiO2 content of the sol, a wide variation in pH also did not exert a significant effect on the particle size. Stability of the silica sols synthesized in an alkaline medium was enhanced by the replacement of alcohol with water during evaporation at pH 8.5‒9.5. The possibility to produce silica sols with the required characteristics (particle size, pH, stability, purity, and SiO2 content in an aqueous or alcohol medium) makes them applicable in various industries.

Effect of colloidal nanosilica (SiO2) on the mechanical, thermal and rheological properties of poly(vinyl acetate) synthesized by in situ emulsion polymerization method was investigated. For this purpose, a poly(vinyl acetate) latex containing 1.5 wt% colloidal silica nanoparticles was produced and the results were compared with of a blank sample. The effect of nanoparticles on the shear strength of a blank and modified poly(vinyl acetate) was characterized by tensile test. The effect of nanoparticles on glass transition temperature (Tg), thermal stability and char yield of pristine poly(vinyl acetate) and its nanocomposite was evaluated by differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA), respectively. The rheological behavior of the products was studied by rheometric mechanical spectrometry (RMS). Eventually, field emission scanning electron microscopy (FE-SEM) coupled with elemental mapping of X-ray spectroscopy (EDX) was used to study the morphology and elemental analysis of the nanocomposite. The results showed that the shear strength was improved by 11% with increasing 1.5 wt% colloidal silica nanoparticles into poly(vinyl acetate). Besides, with the addition of silica nanoparticles, Tg increased approximately 1°C due to creating more free volume between the polymer chains. The TGA results showed that the nanocomposite char yield increased by 3.8% at 800°C in comparison with the blank polymer char yield, suggesting a thermal stability improvement in the presence of colloidal silica nanoparticles as a result of molecular interactions. The results of RMS revealed the shear thinning behavior of the latexes. The FE-SEM-EDX results showed a uniform dispersion of nanoparticles throughout the poly(vinyl acetate) matrix.

Quartz glass is a typical optical material. In this research, colloidal silica (SiO2) and colloidal cerium oxide (CeO2) are used as abrasive grains to polish quartz glass in the shear thickening polishing (STP) process. The STP method employs the shear-thickening mechanism of non-Newtonian power-law fluid to achieve high-efficiency and high-quality polishing. The different performance in material removal and surface roughness between SiO2 and CeO2 slurries was analyzed. The influence of the main factors including polishing speed, abrasive concentration, and pH value on the MRR, workpiece surface roughness, and the surface topography was discussed. Two different slurries can both achieve fine quartz surface in shear thickening polishing with the polishing speed 100 rpm, and pH value 8. The quartz glass surface roughness Ra decreases from 120 ± 10 to 2.3 nm in 14 minutes’ polishing with 8 wt% 80 nm SiO2 slurry, and the MRR reaches 121.6 nm/min. The quartz glass surface roughness Ra decreases from 120 ± 10 to 2.1 nm in 12 minutes polishing by 6 wt% 100 nm CeO2 slurry and the MRR reaches 126.2 nm/min.

Clays and soils produce strong small‐angle X‐ray scattering (SAXS) because they contain large numbers of nanoparticles, namely allophane and ferrihydrite. These nanoparticles are amorphous and have approximately spherical shape with a size of around 3–10 nm. The weight ratios of these nanoparticles will affect the properties of the clays and soils. However, the nanoparticles in clays and soils are not generally quantified and are sometimes ignored because there is no standard method to quantify them. This paper describes a method to quantify nanoparticles in clays and soils with SAXS. This is achieved by deriving normalized SAXS intensities from unit weight of the sample, which are not affected by absorption. By integrating the normalized SAXS intensities over the reciprocal space, one obtains a value that is proportional to the weight ratio of the nanoparticles, proportional to the square of the difference of density between the nanoparticles and the liquid surrounding the nanoparticles, and inversely proportional to the density of the nanoparticles. If the density of the nanoparticles is known, the weight ratio of the nanoparticles can be calculated from the SAXS intensities. The density of nanoparticles was estimated from the chemical composition of the sample. Nanoparticles in colloidal silica, silica gels, mixtures of silica gel and α‐aluminium oxide, and synthetic clays have been quantified with the integral SAXS method. The results show that the errors of the weight ratios of nanoparticles are around 25% of the weight ratio. It is also shown that some natural clays contain large fractions of nanoparticles; montmorillonite clay from the Mikawa deposit, pyrophillite clay from the Shokozan deposit and kaolinite clay from the Kanpaku deposit contain 25 (7), 10 (2) and 19 (5) wt% nanoparticles, respectively, where errors are shown in parentheses. [ABSTRACT FROM AUTHOR]

The ballistic resistance of high-strength fabrics improves upon impregnation with Shear Thickening Fluids (STFs). The performance of such STF treated fabrics depends on the rheological properties of the STF which in turn are governed by the physicochemical properties of the STF. The present study utilizes rheological characterization of shear thickening silica-polyethylene glycol dispersions (of different material configurations in terms of packing fraction, particle size and continuous phase viscosity) to assess their performance and obtain the best STF material configuration for ballistic body armor applications based on the design criteria proposed herein. The ballistic performance assessment results showed that the STFs with high packing fractions which thicken discontinuously, are highly effective compared to the continuously shear thickening fluids. Furthermore, the use of smaller particle size dispersed phase in the STF formulation was determined to be economical. Also, the use of lower molecular weight dispersion medium was suggested as it allows for a broader working temperature range of the STF. Additionally, the technological issues associated with the development and the practical application of STF-Armor were addressed. [ABSTRACT FROM AUTHOR]

In the present study, a zirconia-based primary slurry free from silica (S-0) was prepared by replacing the colloidal silica sol binder in the commercial zirconia-based slurry (S-6.4) with an aqueous polymer binder. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), and line scan analyses from the surface of cast samples show that the thickness of reaction layer has been decreased from 10 to 6 µm in the samples S-6.4 and S-0, respectively. Also, the microhardness tests obtained from the sample surfaces show a 80 µm decrease in the surface-hardened layer. [ABSTRACT FROM AUTHOR]

A deep understanding of the behavior and specifications of grouting materials between soil particles is required to increase the applications of various grouting technologies. Out of the different grouts that can be injected in fine-grained soils, colloidal silica has been selected in this study due to its unknown effects on fine-grained soils. In this study, the effects of colloidal silica on silty sand with different amounts of silt were studied, and the strength parameters (c, ϕ) of stabilized samples under long-term static loading was evaluated. A total of 42 uniaxial compression tests and 75 consolidated-drained triaxial tests were done on the samples. Uniaxial compression tests were conducted to determine the most suitable age of the samples for testing, which was three days. The results of the triaxial tests indicate an increase in the drained cohesion parameter in all samples, while changing the drained internal friction angle in silty sands decreases. [ABSTRACT FROM AUTHOR]

In the booming field of nanotechnology, colloidal silica (CS) has been introduced for ground improvement and liquefaction mitigation. It possesses a great ability to restrain pore pressure generation during seismic events by using an innovative stabilization technique, with the advantages of being a cost-effective, low disturbance, and environmentally friendly method. This paper firstly introduces molecular structures and some physical properties of CS, which are of great importance in the practical application of CS. Then, evidence that can justify the feasibility of CS transport in loose sand layers is demonstrated, summarizing the crucial factors that determine the rate of CS delivery. Thereafter, four chemical and physical methods that can examine the grouting quality are summed and appraised. Silica content and chloride ion concentration are two effective indicators recommended in this paper to judge CS converge. Finally, the evidence from the elemental tests, model tests, and field tests is reviewed in order to demonstrate CS's ability to inhibit pore water pressure and lower liquefaction risk. Based on the conclusions drawn in previous literature, this paper refines the concept of CS concentration and curing time being the two dominant factors that determine the strengthening effect. The objective of this work is to review CS treatment methodologies and emphasize the critical factors that influence both CS delivery and the ground improving effect. Besides, it also aims to provide references for optimizing the approaches of CS transport and promoting its responsible use in mitigating liquefaction. [ABSTRACT FROM AUTHOR]

Colloidal silica has been utilized as a binder agent in various areas owing to its sinterability and high permeability. However, regarding its use in MgO–CaO hot gunning mixes are lacking. In this study, phase compositions and physical properties of different colloidal silica contents on hot gunning mixes were investigated. The rebound loss rate of hot gunning mixes at 1100 °C was also evaluated via thermal simulation. In addition, the interface analysis between the gunned layer and Mag-Chrome bricks was presented, and the results were compared with those obtained using conventional phosphate-bonded mixes. The results indicate that the colloidal silica-bonded MgO–CaO hot gunning mixes achieve the appropriate mechanical strength and bulk density with 5 wt% of colloidal silica; the primary phases of mixes were forsterite and monticellite. In comparison with the conventional phosphate-bonded gunning mixes, the use of colloidal silica led to better physical properties and lower rebound loss rate under the present experimental conditions. Moreover, the gunned layers obtained were more compact and cohesive than the ones prepared using conventional phosphate-bonded mixes. [ABSTRACT FROM AUTHOR]

• Hydrophobic hybrid coatings with excellent transparency and high hardness were prepared. • The hybrid coatings exhibited excellent dust removal performance under gravity. • The surface roughness preferentially contributed to good dust removal performance. • The hydrophobic silylmethyl groups can further enhance the dust removal performance. • The hybrid coatings demonstrated excellent durability under simulated environment of Mars. Transparent hybrid coatings were prepared from methyltrimethoxysilane (MTMS) and colloidal silica nanoparticles (SiO 2) by a sol-gel process. Influences of colloidal silica content and aging time on the surface morphology, surface composition, and the properties such as transparency, water contact angles (WCA), and pencil hardness, of the hybrid coatings were systematically investigated. Coatings with WCA as high as 110–120° and pencil hardness of 4–5 H could be achieved at appropriate colloidal silica content and aging time. The dust removal performance of the hybrid coatings was examined by vertical tilting of the dust-deposited coatings using volcanic ash as the standard dust. When the WCA was over about 100°, the hybrid coatings exhibited excellent dust removal performance under gravity, regardless of the quantity of the dust deposited. Oxygen plasma etching experiments and the dust removal tests in dry chamber indicated that the nanometer-scale surface roughness could endow the hybrid coatings with the good dust removal performance. The hydrophobic methyl groups can further enhance the dust removal performance. The hybrid coating with MTMS/SiO 2 mass ratio of 1.3:1 was cast on the coverslips of the solar cell for Mars, and undergone two durability series tests, i.e. thermal shock/humidity series (THS) test and high-low temperature cycle/electron beam radiation/vacuum ultraviolet radiation series (HEVS) test. The anti-dust coverslips showed good durability in HEVS tests and dust removal percentage of 75.8% after HEVS test, implying its good service life on Mars. [ABSTRACT FROM AUTHOR]

Novel hydrophobic composites (FS-PSA/SiO2) were prepared by directly physically mixing fluorine–silicon-containing poly (styrene–acrylate) latexes (FS-PSA) with colloidal silica. Sol–gel processes were carried out between silica particles and silanol groups on the surface of poly (styrene–acrylate) latexes to enhance the roughness and hydrophobicity of composite films. TEM photos revealed that FS-PSA latexes exhibited a clear core–shell structure, and the intermolecular hydrogen bonding guaranteed the uniform dispersion of silica particles. The average diameter data indicated that the copolymerization and sol–gel process had all increased the average diameter of the composite latexes. FTIR and XPS spectra confirmed that two kinds of Si–O bonds existed in the composite films, of which one was related to the Si–O groups of colloidal silica while the other was related to the Si–O–Si groups obtained from the sol–gel processes. SEM and AFM images revealed that the sol–gel processes had increased the roughness of the composite films. The water contact angle (WCA) of the composite films were found to increase with the copolymerization and sol–gel processes. Thermogravimetric analysis (TGA) curves demonstrated that the FS-PSA/SiO2 composite films exhibited much better thermal stability than the PSA and FS-PSA films. [ABSTRACT FROM AUTHOR]

• Zeolite hollow fibers were prepared by a phase inversion-assisted extrusion method. • Cd2+ adsorption tests were conducted using the hollow fibers and zeolite powder. • The zeolite hollow fibers have longer breakthrough times than the powder counterpart. • Conventional hollow fibers have better adsorption performances than those with 3-channel design. Geometry greatly affects performances in adsorption and catalytic reactions. Since the crystal structure of zeolite collapses at high temperature, it is difficult to synthesize hollow fibers from only zeolite by sintering. In this study, we synthesized zeolite hollow fibers using colloidal silica, which has excellent heat and chemical resistance, as an inorganic binder. The zeolite hollow fiber precursor was immersed in a colloidal silica aqueous solution and calcined at 600 °C. Additional silica coating significantly improves the mechanical robustness by increasing the fracture load by up to 200%, while the zeolite content, specific surface area/pore volume reduced slightly. These results show that colloidal silica functions as an effective inorganic binder without blocking the pores of the zeolite. The cadmium adsorption showed that for a 100-ppm Cd2+ solution, the breakthrough time at C / C 0 = 0.05 was effectively extended by 20% (112 min) and 65% (153 min) for conventional hollow fiber and 3-channel designs, respectively, compared to the powder counterpart (93 min). [ABSTRACT FROM AUTHOR]

The volume fraction dependent morphological transition of droplets during the evaporation of colloidal silica solution was investigated using the spray-drying method. The colloidal solution was prepared from sodium silicate using the sol-gel method. Spray drying with a tubular reactor was used in the experiment, with the volume fraction of the colloidal silica varying from 15 to 2%. It was demonstrated that a morphological transition from a sphere shape to a donut-like shape takes place at a colloidal volume fraction of between 4% and 2%, even when the drying rate remains moderate and is not extremely fast. A spherical silica particle shape was found at a colloidal volume fraction of between 15% and 8%. The morphological transition depends strongly on the volume fraction of the colloids in the droplets. Further, the ζ-potential of the particles in the droplet also affects the transition by applying an interparticle electrostatic force. The same high surface charge of sol silica provides a repulsive interaction between the sol particles inside the droplet. The transition is hindered when the colloid volume fraction is increased because of the inherent spatial constraint. The Fourier-transform infrared (FT-IR) spectra of both the spherical and donut-like particles confirm the chemical bonding of the powder silica product. Moreover, X-ray diffractometry (XRD) analysis revealed an amorphous phase of the silica particles produced from spray drying. These preliminary results open up a new path for controlling the formation of a wide variety of silica particles using the spray-drying method. In addition, the different silica particle morphologies enable a variety of particle applications. [ABSTRACT FROM AUTHOR]

Phenolphthalein polyethersulfone (PES-C)/silica (SiO2) composite nanofibrous membranes were prepared via solution blowing. The spinning solutions were prepared by mixing a solution of PES-C in dimethylacetamide with different amounts of colloidal SiO2 in ethylene glycol. Attenuated total reflectance–Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, thermal gravimetric analysis, and water contact angles were conducted to characterize the properties of composite nanofibrous membranes. The results showed that the thermal properties and surface wettability were improved by the addition of appropriate amount of nano-SiO2. Furthermore, permeation fluxes of pure water and the filtration of starch suspension were measured to evaluate the antifouling property of the PES-C/SiO2 composite membranes. [ABSTRACT FROM AUTHOR]

The effects of the structure of di- and triblock copolymers of poly(L-lysine) - LYS with poly(ethylene glycol) - PEG as well as the length of nonionic fragment in the LYS-PEG macromolecule on the copolymer chains conformation in the adsorption layer formed on the colloidal silica (SiO2) surface were examined. Spectrophotometry and turbidimetry were applied for the determination of copolymer adsorbed amounts and stability coefficients of silica aqueous suspensions. The electrokinetic parameters such as solid surface charge density and zeta potential were also estimated. The adsorption of LYS-PEG was proved to be the highest at pH 10 whereas the lowest adsorption on the solid surface was found for the triblock copolymer with long fragments of LYS at the same pH value. [ABSTRACT FROM AUTHOR]