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[Display omitted] Methanol is a promising hydrogen carrier for fuel cell vehicles (FCVs) via methanol steam reforming (MSR) reaction. Ceria supported copper catalyst has attracted extensive attentions due to the extraordinary oxygen storage capacity and abundant oxygen vacancies. Herein, we developed a colloidal solution combustion (CSC) method to synthesize a porous Cu/CeO 2 (CSC) catalyst. Compared with Cu/CeO 2 catalysts prepared by other methods, the Cu/CeO 2 (CSC) catalyst possesses highly dispersed copper species and abundant Cu+-O v -Ce3+ sites at the copper-ceria interface, contributing to methanol conversion of 66.3 %, CO 2 selectivity of 99.2 %, and outstanding hydrogen production rate of 490 mmol g cat −1 h−1 under 250 °C. The linear correlation between TOF values and Cu+-O v -Ce3+ sites amount indicates the vital role of Cu+-O v -Ce3+ sites in MSR reaction, presenting efficient ability in activation of water. Subsequently, a deep understanding of CSC method is further presented. In addition to serving as a hard template, the colloidal silica also acts as disperser between nanoparticles, enhancing the copper-ceria interactions and facilitating the generation of Cu+-O v -Ce3+ sites. This study offers an alternative approach to synthesize highly dispersed supported copper catalysts. [ABSTRACT FROM AUTHOR]

Colloidal silica-bonded castables offer several advantages compared to traditional calcium aluminate cement (CAC)-bonded castables, including lower torque values during mixing, superior drying properties, and a lower CaO content. Nevertheless, information on the combination of CAC and colloidal silica is limited, and the effect of CAC additions on the drying properties of colloidal silica-bonded castables remains unknown. In this study, these drying properties were measured by rapidly heating 400 kg samples to 500 °C and assessing the resulting damage to each sample. Additionally, the physical and chemical properties of small-scale samples were analyzed to evaluate the impact of CAC addition. The analyzed properties included cold crushing strength (CCS), density, permanent linear change (PLC) and weight loss. The microstructure of the samples was investigated by FESEM and EDS. The results indicate that adding 1.5 wt.% increased the cold crushing strength at 20 °C, while lower CAC amounts had no noticeable effect. A mullite phase was observed in the sample without CAC, and correspondingly, anorthite was found in those with CAC additions. The samples exhibited significant differences in the drying tests, with the degrees of damage increasing with the CAC addition. [ABSTRACT FROM AUTHOR]

This first part of the work is devoted to development of high-performance cement composites (HPCCs) with aim to elaborate a mix design methodology for obtaining defined properties of HPCC with industrial by-products such as fly ash, silica fume, and colloidal silica. The research employs innovative methods of experimental design and response surface optimization to find a compromise between the set compressive strength and mix workability. Stage 1 consists in selecting appropriate raw materials and designing an initial mix. Stage 2 involves finding an optimal dosage of superplasticizer. Stage 3 is the response surface optimization, which includes experiment planning with variable parameters x1 (fly ash) and x2 (nanosilica), conducting practical experiments, results of analysis and approximation, using mathematical models of 1st, 2nd, and 3rd order polynomials. The final Stage 4 implies finding the optimal compromise solution between strength and mix flowability, as well as experimental validation of the results obtained. The approach developed can be used for the design of similar multi-component mixes. [ABSTRACT FROM AUTHOR]

Fabricating large-scale porous bioactive glass bone scaffolds presents significant challenges. This study aims to develop formable, in situ setting scaffolds with a practical gelation time of about 10 min by mixing 45S5 bioactive glass with sodium silicate (waterglass) and an acid initiator. The effects of pH (2–11), waterglass concentration (15–50 wt.%), and acid initiator type (phosphoric or boric acid) were examined to optimize gelation kinetics and microstructure. A 10 min gelation time was achieved with boric acid and phosphoric acid at various pH levels by adjusting the waterglass concentration. Exponential and polynomial models were proposed to predict gelation times in basic and acidic environments, respectively. The optical properties of the gels were studied qualitatively and quantitatively, providing insights into gelation kinetics and structure. Acidic gels formed smaller particles in a dense network (pores < 550 nm) with higher light transmittance, while basic gels had larger aggregates (pores ~5 µm) and lower transmittance. As the waterglass concentration decreased, pore size and transmittance converged in both groups. The onset of gelation was detected around 8 min using the derivative of light transmittance. This work identifies the key factors controlling waterglass gelation and their impact on gel structure, enabling the tailored creation of formable, in situ setting bioactive glass bone scaffolds. [ABSTRACT FROM AUTHOR]

The nature of serpentinite interaction with low-concentration sulfuric acid solutions is studied. Using IR-Fourier spectroscopy, X-ray, and serpentinite leaching with sulfuric acid solutions containing 10–60% of stoichiometrically required amount (SRA) of H2SO4 (taken relative to the molar magnesium content in serpentinite), it is shown that the appearance and influence of silica on the course of serpentinite dissolution is detected at concentrations of 30–40% of SRA of H2SO4. On the basis of the obtained results, this article points out the technological, economic, and ecological advantages of use of sulfuric acid solutions of low concentrations in the process of acid processing with the aim of producing magnesium salts.

The coexistence of different foulant compositions in the feed water of reverse osmosis (RO) systems causes serious complications in the fouling process of the membranes. Hence, in this technical research, the phenomenon of combined inorganic (gypsum)-colloidal (silica particles) fouling (inorganic-colloidal fouling) of brackish water RO (BWRO) process was studied in the lab-scale experiments. Moreover, the effect of the presence of air micro–nano bubbles (AMNBs) in the feed water; as a new practical method for control of membrane fouling, was investigated on this phenomenon. For this purpose, a suspension with the potential of inorganic scaling [calcium sulfate, Saturation index (SI)=0.96 ] and colloidal fouling (colloidal silica, 50 mg/L) was used to form the inorganic and colloidal foulings (simultaneously) on the membrane surface during the inorganic-colloidal fouling process. All experiments were performed twice, once in the absence and once in the presence of AMNBs. Finally, the results of this research were compared with the results of the inorganic and colloidal fouling studies. Based on the results, the inorganic-colloidal fouling formed a dense and compact fouling layer on the membrane surface, which severely reduced the permeate flux (76.3%) and salt rejection (4%). The amount of decrease of these two parameters in inorganic-colloidal fouling was much higher than each of individual inorganic and colloidal foulings. In the presence of AMNBs, both types of inorganic and colloidal foulings greatly reduced and the major portion of inorganic-colloidal fouling was related to the colloidal fouling. Thus, a significant decline was observed in adverse effects of inorganic-colloidal fouling on the membrane performance and the permeate flux and salt rejection decreased by 18.5% and about 1%, respectively. The results of this study could introduce the micro–nano bubbles (MNBs) technology as an effective method to inhibit the inorganic-colloidal fouling in RO systems. Practical Applications: Today, reverse osmosis processes are known as efficient technologies for supplying drinking water from brackish and sea water resources due to their high ability to remove various compounds. The separated compounds from the water accumulate near the membrane surface and consequently deposit on it and/or inside its pores. This phenomenon is called membrane fouling and has adverse effects on the performance of reverse osmosis processes. Water resources usually have different types of pollutants that simultaneous presence of them can intensify the membrane fouling process. Gypsum scaling and colloidal silica fouling are two major common types of reverse osmosis membrane fouling. Therefore, in this research, the effects of the inorganic-colloidal fouling were studied on the performance of a commercial brackish water reverse osmosis membrane, in presence and absence of air micro–nano bubbles. The results showed that the combined fouling formed a complex fouling layer on the membrane surface in absence of air micro–nano bubbles. In real-scale reverse osmosis process, this layer can severely reduce the membrane permeate flux and salt rejection which result to increase in the operational and maintenance costs. Alternatively, the presence of air micro–nano bubbles in the reverse osmosis feed flow could limit both inorganic and colloidal foulings and their synergetic effects on each other. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to perform the surface treatment of synthetic α-Fe2O3 red iron oxide pigment with hydrolysate 3-aminopropyl silane (A) and colloidal silica (CS) and investigate the effects of surface-treated pigment on the styrene acrylic (SA) emulsion and polyurethane (PU) dispersion. Design/methodology/approach: For this purpose, firstly red iron oxide particles were modified with A and CS separately in an aqueous medium. After isolation of the modified iron oxide were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). Moreover, the degree of the dispersion stability of the modified pigment in coatings with SA emulsion and PU dispersion was investigated by using an oscillation rheometer. Loss (G''), storage (G') modulus, loss factor [tan(δ)] and yield stress (τ0) values were determined by performing amplitude and frequency sweep tests. Findings: The τ0 in SA coatings decreases with the amount of used A and increases with the amount of used CS. The τ0 decreases as the amount of used A and CS in PU coatings increases. The use of CS on red iron oxide pigments causes storage modulus to increase in SA coatings at low angular frequencies, while it causes a decrease in PU coatings. Originality/value: To the best of the authors' knowledge, for the first time, the suspended state of the iron oxide hybrid pigment formed with CS in the coating was investigated rheologically in this study. [ABSTRACT FROM AUTHOR]

Rapid face of urbanization has lead to increase in concrete production, rising concerns about its implications for climate change, depletion of resource materials and environmental degradation. Concrete is prone to attacks by various aggressive environment effects. Depending upon the requirements, different types of concrete have been developed using nano based materials. One of the most used materials at nano scale is nano silica. The effect of use of nano silica in the form of colloidal silica is used in the present study as replacement and addition to cement to study the sulphuric acid attack on concrete. Colloidal silica with 30% of nano solids of SYCOL-TX is replaced and added to cement in different proportions i.e., 0, 0.5, 1, 1.5, 2, 2.5 and 3% respectively. Optimum mix is found out by conducting compressive strength test to concrete specimens after 28 days of curing. The test samples prepared with optimum content of colloidal silica are immersed in different concentrations of 1.5, 3, 4.5 and 6% sulphuric acid solution for a time period of 28, 56, 90 and 180 days, after 28 days of water curing. Visual appearance, weight loss and compressive strength lossare determined in the study to study the effect of sulphuric acid attackon concrete specimens. From the results it is observed that incorporation of colloidal silica in concrete enhances its compressive strength and resistance to acidic environments in terms of durability. [ABSTRACT FROM AUTHOR]

Water seepage flow can dissolve soluble minerals that exist in rock formations. With the development of the excavated area due to dissolution, the water seepage velocity (discharge) into the dissolved rock will also increase. Therefore, water seepage and dissolution propagation are two interrelated processes. Mosul Dam foundation has experienced these processes since its construction, resulting in karstification in the reservoir and foundation of the dam. The present seepage-dissolution measure to minimize this phenomenon relies on traditional cementitious grouts. However, this measure has not been able to address the issue effectively. Currently, there are a few studies on the chemical remediation of soluble rocks under the influence of high-velocity water flow and water pressure. Therefore, the first part of the current study focuses on the impact of high-velocity water flow and water pressure on the dissolution acceleration of gypsum/anhydrite rocks. In the second part, the waterproof capacity of silica colloidal and its impact on the solubility reduction of the rocks is evaluated. Two distinct laboratory models were designed to simulate rock dissolution in the dam abutments and under the dam. Two sets of experiments were conducted on untreated and silica-treated samples. The experiments were executed on the samples extracted from Fatha Formation outcrop and problematic layers of brecciated gypsum situated at varying depths of the Mosul Dam foundation. The obtained findings reveal that the colloidal silica grout markedly prevents the water seepage impact on the soluble rock and that it can be very useful as an alternative to cement-based grouts. [ABSTRACT FROM AUTHOR]

Colloidal silica is a relatively new grouting low-carbon material used in soil improvement projects. A series of mechanical tests on a sand with different solid contents of the binder, i.e. 40, 30 and 20% solid content have been performed. Unconfined compressive strength at 7, 28 and 56 days, shear tests and permeability tests at 7 days were assessed. A statistical interpretation of these data has been performed and values were interpreted. A mathematical prediction model was suggested to estimate the mechanical strength of the grouted sand as the dilution grade varies. Furthermore, some considerations useful for geotechnical design on the evolution over time of the mechanical characteristics of the grouted sands have been carried out. Results show, from a statistical and mathematical view, that colloidal silica is a promising binder for ground improvement applications. [ABSTRACT FROM AUTHOR]

The waterglass or St o¨ ber method is commonly used to synthesize spherical colloidal silica; however, these methods have some disadvantages, such as complicated processes for the removal of sodium ions and expensive and energy-consuming raw materials such as tetraethoxysilane (TEOS). In this study, size-controlled spherical colloidal silica was synthesized from silicon metal at room temperature using an ultrasound process with hydrazine monohydrate as the solvent. Silicon metal dissolves easily in hydrazine monohydrate under ultrasound irradiation, and spherical colloidal silica can be synthesized by adding alcohol to this precursor solution. By changing the concentration or type of alcohol, size-controlled colloidal silica 20–200 nm in size could be easily obtained. In addition, finer and more monodisperse particles were produced by low-frequency ultrasound irradiation, which had a higher stirring effect at the particle formation stage. The present method is effective because size-controlled colloidal silica can be synthesized at room temperature using only silicon metal, hydrazine, and alcohol as raw materials, without complicated processes or expensive and energy-consuming raw materials such as TEOS or tetramethoxysilane (TMOS).

Fabricating large-scale porous bioactive glass bone scaffolds presents significant challenges. This study aims to develop formable, in situ setting scaffolds with a practical gelation time of about 10 min by mixing 45S5 bioactive glass with sodium silicate (waterglass) and an acid initiator. The effects of pH (2–11), waterglass concentration (15–50 wt.%), and acid initiator type (phosphoric or boric acid) were examined to optimize gelation kinetics and microstructure. A 10 min gelation time was achieved with boric acid and phosphoric acid at various pH levels by adjusting the waterglass concentration. Exponential and polynomial models were proposed to predict gelation times in basic and acidic environments, respectively. The optical properties of the gels were studied qualitatively and quantitatively, providing insights into gelation kinetics and structure. Acidic gels formed smaller particles in a dense network (pores < 550 nm) with higher light transmittance, while basic gels had larger aggregates (pores ~5 µm) and lower transmittance. As the waterglass concentration decreased, pore size and transmittance converged in both groups. The onset of gelation was detected around 8 min using the derivative of light transmittance. This work identifies the key factors controlling waterglass gelation and their impact on gel structure, enabling the tailored creation of formable, in situ setting bioactive glass bone scaffolds.

In lost wax technology, self-supporting ceramic moulds are made, which must have adequate strength after being filled with liquid metal. The final structural strength is determined by such factors as the thickness of the individual layers applied to the wax model resulting from the viscosity of the liquid mass, the specific strength of the layers formed, and the heat treatment of the moulds. The development of technology and materials is moving in the direction of increasing the specific strength of self-supporting ceramic moulds. The consequence of this is that the final strength of these moulds is too high, making it difficult to knock castings out of the moulds. Removing mould remnants from holes, closed spaces of the casting, corners, sharp edges, variable cross sections and etc. is cumbersome. In order to remove mould remnants from the casting, a method is used to dissolve them in heated solutions of suitable chemical composition and reaction. The paper presents the results of research on a new solution, the essence of which is the production of layers in a ceramic mould, in the middle zone of the mould, characterized by a significantly reduced final strength, achieved after firing. These layers are produced using a different liquid ceramic mass than the base one, based on an organic binder. As a result, thanks to the embedded layer, very good knock-out of castings is achieved and separation of residual ceramic mass. Special layers can be incorporated over the entire surface or only in those places where the bonding of the casting surface and ceramic mass occurs.

Improving the green mechanical strength of colloidal silica‐bonded corundum castables is essential to their widespread utility. The effects of varying contents (0–2 wt%) of La2O3 on the green mechanical strength of colloidal silica‐bonded corundum castables were investigated. The findings demonstrate that La2O3 has a positive impact on the green mechanical strength of colloidal silica‐bonded castables. The colloidal silica‐bonded corundum castable containing 2 wt% La2O3 exhibits higher green mechanical strength than the cement‐bonded corundum castable. Additionally, the castable shows excellent construction performance. The basic properties of La2O3 and La(OH)3 facilitate the absorption of H+ from the surface of colloidal silica to form more siloxane bonds and speed up gelation. Fourier transform infrared spectroscopy and X‐ray fluorescence spectroscopy analyses indicate that La3+ ions participate in the condensation of –Si–OH and bond the broken Si–O bonds to create Si–O–La chemical bonds. La3+ ions bridge the colloidal silica particles, leading to stable three‐dimensional network structures that result in an increased green mechanical strength of the castables. The water consumption during the hydration reaction expedites gelation, further contributing to the enhancement of the green mechanical strength of the corundum castables. Given its wide sources and stable performance, La2O3 can be considered an efficient setting agent with the potential for extensive industrial application. [ABSTRACT FROM AUTHOR]

PNIPAAm‐grafted thermoresponsive hollow nano‐holed polymeric‐shell (HHPS) particles were fabricated from surface‐modified colloidal silica (CS) with poly(ethylene glycol) methyl ether‐3‐(triethoxysilyl)propyl isocyanate (PEGME‐IPTES) and 3‐(trimethoxysilyl) propyl methacrylate (MPS) as templates. The polymeric shells were then synthesized through a "grafting‐through" approach via surface‐initiated polymerization of N‐isopropyl acrylamide (PNIPAAm) using potassium persulfate (KPS) as an initiator, followed by the etching of CS with hydrofluoric acid to remove the CS core templates. CS nanoparticles and PEGME‐IPTES were presynthesized using tetraethoxysilane (TEOS) and distilled water in methanol with ammonia solution as a catalyst by the sol–gel method and using 3‐(triethoxysilyl) propyl isocyanate (IPTES) with poly(ethylene glycol) methyl ether (PEGME) in the presence of dibutyltin dilaurate. The chemical structures of bare and modified CS, PNIPAAm, PNIPAAm‐CS, and HHPS particles were characterized by FT‐IR and NMR spectroscopies. SEM and TEM images confirmed that the resulting HHPS particles had a significant number of interconnected nanoholes. To evaluate the LCST behaviors of HHPS particles, the transition of transmittance and the changes in particle diameter according to the temperature change were measured through UV‐vis spectroscopy, DLS, and microscopy. [ABSTRACT FROM AUTHOR]

Colorless and transparent semi‐alicyclic fluoro‐containing polyimide (PI) nanocomposite films with enhanced high‐temperature dimensional stability and sustained optical transparency were designed and prepared via incorporation of nano‐sized colloidal silica (SiO2) fillers into the PI matrix derived from hydrogenated pyromellitic dianhydride (HPMDA) and 2,2′‐bis[(4‐aminophenoxy)phenyl]hexafluoropropane (BDAF). The derived PI composite films, abbreviated as 6FCPI‐X in which X stands for the weight percent of the SiO2 in the composite films, exhibited superior thermal and comparable optical properties to the pristine 6FCPI‐0 (6FDA‐BDAF) matrix film. For example, as for the thermal properties, 6FCPI‐35 composite film showed a glass transition temperature (Tg) of 279.1°C and a residual weight ratio at 750°C (Rw750) of 66.1%, which were apparently higher than those of 6FCPI‐0 matrix (Tg = 272.2°C; Rw750 = 47.1%). More importantly, the 6FCPI/SiO2 nanocomposite films showed obviously lower linear coefficients of thermal expansion (CTE) values as compared with that of the 6FCPI‐0 matrix. 6FCPI‐35 composite film showed a CTE value of 36.1 × 10−6/K in the temperature range of 50–250°C, which was lower than half of that of the 6FCPI‐0 matrix (CTE = 77.9 × 10−6/K) in the same range of temperature. In addition, incorporation of nano‐sized colloidal SiO2 particles basically maintained the intrinsically good optical properties of the pristine 6FCPI‐0 matrix film. 6FCPI‐35 composite film showed the optical transmittances of 81.7%, 85.3%, and 87.2% at the wavelength of 400 nm (T400), 450 nm (T450), and 500 nm (T500), respectively, which were in the same level with those of the 6FCPI‐0 film (T400 = 84.0%; T450 = 86.3%; T500 = 87.6%). The 6FCPI series of nanocomposite films also exhibited similar CIE Lab color parameters, including the yellow indices (b*) lower than 2.0 and haze values lower than 1.0%. [ABSTRACT FROM AUTHOR]

Improving the green mechanical strength of colloidal silica‐bonded corundum castables is essential to their widespread utility. The effects of varying contents (0–2 wt%) of La2O3 on the green mechanical strength of colloidal silica‐bonded corundum castables were investigated. The findings demonstrate that La2O3 has a positive impact on the green mechanical strength of colloidal silica‐bonded castables. The colloidal silica‐bonded corundum castable containing 2 wt% La2O3 exhibits higher green mechanical strength than the cement‐bonded corundum castable. Additionally, the castable shows excellent construction performance. The basic properties of La2O3 and La(OH)3 facilitate the absorption of H+ from the surface of colloidal silica to form more siloxane bonds and speed up gelation. Fourier transform infrared spectroscopy and X‐ray fluorescence spectroscopy analyses indicate that La3+ ions participate in the condensation of –Si–OH and bond the broken Si–O bonds to create Si–O–La chemical bonds. La3+ ions bridge the colloidal silica particles, leading to stable three‐dimensional network structures that result in an increased green mechanical strength of the castables. The water consumption during the hydration reaction expedites gelation, further contributing to the enhancement of the green mechanical strength of the corundum castables. Given its wide sources and stable performance, La2O3 can be considered an efficient setting agent with the potential for extensive industrial application. [ABSTRACT FROM AUTHOR]

This study aims to synthesize stable colloidal silica via the peptization method as a green and low-cost route. It is crucial to adopt a proper synthesis procedure and choose an appropriate raw material. To achieve this purpose, kaolin was employed as a silica rich source that occurs abundantly in nature. The process involves synthesis of the wet gel through the succession of calcination, acid leaching, alkaline treatment, sodium silicate precipitation, and then peptization of the wet gel. Effect of the acid type on acid leaching was evaluated. Effective factors affecting the gel purity such ad acid concentration, pH of gelation, and temperature of alkaline treatment, were studied and optimized via a statistical design of the experiments. Subsequently, the influential parameters on stability and particle size of the obtained colloidal silica, including the temperature of the gel formation, pH of sol medium, concentration of silica gel, and type of stabilizing base, were investigated via one-facto-at-a-time. The samples were characterized by X-ray fluorescence analysis (XRF), dynamic laser light scattering analysis (DLS), X-ray Diffraction (XRD), Fourier transform infrared (FTIR), Brunauer–Emmett–Teller (BET), and Field emission scanning electron microscopy (FESEM) analyses. Results showed that under optimum conditions, ultra-pure silica gel with a silica content of 99.34 % was obtained. The colloidal sample with the highest stability (zeta potential of −75.6 mV), had nanoparticles showing sizes in the range of 21–66 nm.

The anomalous viscosity of colloidal dispersions of silica has been known and studied for a long time. Several different mechanisms have been proposed to explain it, related to the electrical double layer, hydration layer, and porous/gel layer at the silica-water interface. However, it is still not entirely clear which mechanism is actually operative. Here, based on measurements of viscosity dependence on the concentration of indifferent electrolyte in highly diluted colloidal silica systems and its interpretation using the well-known Einstein equation, the concept of a swellable polyelectrolyte gel layer is corroborated. [ABSTRACT FROM AUTHOR]

Colloidal silica (CS) grouting is a soil improvement technique for seismic liquefaction risk mitigation consisting of the injection of a time-hardening, colloidal silica–based grout into potentially liquefiable sandy soils. A published laboratory test database—consisting of cyclic undrained triaxial tests on liquefiable clean untreated sand and on sand stabilized by 5% CS under different levels of initial stress anisotropy—is here discussed following an energy-based approach. The test results are presented and analyzed in terms of dissipated energy during cyclic loading. The obtained results show that (1) the development of dissipated energy is clearly related to the buildup of residual extra pore water pressure only for untreated sand samples; (2) under the same testing conditions, the dissipated energy at failure is significantly higher in stabilized sand than in untreated sand; and (3) the dissipated energy at failure is found to be independent of the cyclic stress amplitude and dependent on the degree of initial stress anisotropy for the untreated sand, while opposite trends are observed for stabilized sand. Therefore, contrary to the untreated sand, there is no evident advantage for using the dissipated energy at failure to assess the capacity of the stabilized sand. [ABSTRACT FROM AUTHOR]

Fucosylated glycosaminoglycans (FGs) derived from sea cucumbers exhibit potent intrinsic Xase (iXase) inhibition, anticoagulation, and antithrombosis. Plasma activated partial thromboplastin time (APTT), a widely used screening test worldwide, is crucial for evaluating anticoagulant efficacy. However, the applicability of these commercially available APTT reagents for assessing anticoagulation of FGs remains unreported. In this study, we investigated the disparity between ellagic acid and colloidal silica APTT reagents in evaluating anticoagulation of dHG-5 and dHLFG-4, two depolymerized FGs, and elucidated the underlying rationale. The results demonstrated that dHG-5 and dHLFG-4 exhibited heightened sensitivity to the ellagic acid APTT reagent both in vitro and in vivo, and did not significantly affect the activation of APTT reagents for plasma. In addition, both ellagic acid and colloidal silica APTT reagents inhibited the anti-iXase of dHG-5 and dHLFG-4, and the inhibition of the ellagic acid APTT reagent was less pronounced compared to the colloidal silica APTT reagent. These findings suggest that the reduced impact of the ellagic acid APTT reagent on the anti-iXase activity of dHG-5 and dHLFG-4 is responsible for the increased sensitivity in plasma APTT analysis. This study offers valuable insights into the characteristics of two APTT reagents applied for assessing the anticoagulant activity of FG-related compounds. [ABSTRACT FROM AUTHOR]

SiO2 based slurry was an ideal solution for addressing element pollution in fused silica polishing. However, it was still a huge challenge to enhance polishing efficiency. Herein, lignin was added into colloidal silica to manipulate SiO2 particles, thereby improving the removal efficiency of fused silica. Specifically, the variations of average particle size (Z-Average) and polymer dispersity index (PDI), -OH groups on particles surface, wettability and viscosity of colloidal silica with addition lignin in the range of 0–5% were introduced. Also, adhesion action and tribological characteristics with and without manipulation in polishing process were studied. Removal mechanism of fused silica using SiO2 based slurry and the key factors to improve polishing performance were discussed at different content of lignin. Colloidal silica was stable at lignin content of 2%, at which material removal rate (MRR) was increased by 216% and surface roughness (Ra) achieved 0.118 nm. This study embarked from abrasives variations directly (particles characteristics) and indirectly (colloidal silica) intending to reveal the change of removal mechanism on fused silica polishing. It provided new insights for fused silica polishing definitely. [ABSTRACT FROM AUTHOR]

MgO-containing and colloidal silica-bonded are important classes of refractory castables of, respectively, high refractoriness and straightforward processing. On the other hand, their combination is not synergetic. Although 0.1–1 wt% additions of MgO set and harden typical colloidal silica-bonded castables in a 1-hour time frame, greater amounts gel the system instantaneously. This paper addresses the combination of fine MgO sinter with a novel aqueous dispersion of colloidal silica whose particles' surfaces were modified with an epoxysilane-based coupling agent. Their low reactivity produced self-flowing MgO-colloidal silica suspensions of excellent workability and, after curing, generated a packed magnesium silicate hydroxide hydrate (Mg 5 Si 8 O 20 (OH) 2.8H 2 O) protective coating over MgO particles, hindering their hydroxylation and preventing volumetric expansion. The cast structures attained displayed safer drying and suitable strength. During thermal treatment, silica particles softened and promoted viscous flow, favoring grains densification. Therefore, after sintering, the microstructure comprised dense MgO grains surrounded by thin layers of forsterite (Mg 2 SiO 4). • A novel silanized colloidal silica dispersion was combined with fine MgO particles. • A self-flowing high-solid load suspension of excellent workability was attained. • MgO hydroxylation deleterious effects were overcome and early strength was improved. • During the first heating, strength, and rigidity remained higher than the silica-free reference. • A high-refractoriness microstructure (95% MgO) was attained after sintering. [ABSTRACT FROM AUTHOR]

This study examines the time evolution of silica/water clusters where the formation of a gel network from unitary silica particles is interrupted by a simple Couette shear field. The aim is to enable the general understanding of this simple system by examining the microscopic basis for the changes in viscosity by providing structural inputs from small-angle scattering for a simple theoretical model. The experimental system is an 8.3 nm particle silica solution (Ludox) where the gelation has been initiated by lowering the pH in a Couette cell providing a constant shear rate of 250 s-1. A unified small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS) procedure is described to measure the scattered intensity in a wavevector range of 3 × 10-4 < q (nm-1) < 3.1 × 10-1, probing structural changes over a broad range of length scales from the nanometre to the micrometre. Scattering data provide a new means of better understanding the behaviour of colloidal clusters when subjected to an external applied shear over a continuous time sequence after gel initiation; a fit of the time-dependent scattered intensity leads to an estimation of the cluster's effective volume fraction and size as a function of time. A reductionist theoretical basis is described to predict the time-dependent viscosity behaviour of the sheared colloidal suspension gel-initiated cluster growth from the volume fraction of the clusters. [ABSTRACT FROM AUTHOR]

The main hardness cations, calcium and magnesium are prevalent in groundwater and brackish waters. Their effect on silica polymerization has been one of the main themes in the study of silica fouling and scaling in membrane filtration processes. However, their synergistic effect in real alkaline brackish waters (pH range of 8.5-9) at low concentrations (below 50 ppm of Ca and Mg), when total silica concentration reaches beyond solubility has not been well studied. Previous research, however, has been conducted on the effect of calcium, magnesium during reverse osmosis (RO) filtration showing that they have catalytic effect on silica polymerization, causing formation of more colloidal silica and at a faster rate. We investigated this effect by conducting bench-scale RO flat sheet experiments with and without calcium and magnesium, at mildly alkaline pH. The feedwater was RO concentrate collected from operating plants. The formed colloidal silica was characterised by monitoring its mass concentration during the fouling phenomenon and after collection of rejects at different recoveries, over a long period of time. In addition, colloidal silica morphology and elemental compositions were studied by scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS) analyses. Scaled membranes from both RO trials were also examined by SEM-EDS to study the scaling layer, along with elemental analysis of scales by inductively coupled plasma atomic emission spectroscopy. The results unequivocally emphasized the catalytic effect of calcium and magnesium by formation of higher amount of colloidal silica at a faster rate. This was confirmed by a significant amount of silica scales on the membrane surfaces from the trial with hard water. [ABSTRACT FROM AUTHOR]

In lost wax technology, self-supporting ceramic moulds are made, which must have adequate strength after being filled with liquid metal. The final structural strength is determined by such factors as the thickness of the individual layers applied to the wax model resulting from the viscosity of the liquid mass, the specific strength of the layers formed, and the heat treatment of the moulds. The development of technology and materials is moving in the direction of increasing the specific strength of self-supporting ceramic moulds. The consequence of this is that the final strength of these moulds is too high, making it difficult to knock castings out of the moulds. Removing mould remnants from holes, closed spaces of the casting, corners, sharp edges, variable cross sections and etc. is cumbersome. In order to remove mould remnants from the casting, a method is used to dissolve them in heated solutions of suitable chemical composition and reaction. The paper presents the results of research on a new solution, the essence of which is the production of layers in a ceramic mould, in the middle zone of the mould, characterized by a significantly reduced final strength, achieved after firing. These layers are produced using a different liquid ceramic mass than the base one, based on an organic binder. As a result, thanks to the embedded layer, very good knockout of castings is achieved and separation of residual ceramic mass. Special layers can be incorporated over the entire surface or only in those places where the bonding of the casting surface and ceramic mass occurs. [ABSTRACT FROM AUTHOR]

Permeation grouting is used to fill the voids in soils with particulates for the purpose of improving soil strength. The technique has been predominatly used for cohesionless soils, however due to nanotechnological advancements in colloidal silica, its application to other soil types has more recently gained attention. Given sands with high silt fractions are a common geotechnical deposit, permeation grouting using colloidal silica is potentially an attractive improvement technique, yet has received limited attention. Therefore, this paper seeks to investigate the transport properties of colloidal silica in low-permeability silty sand, in terms of the effective grouting penetration range and peak strength. To this end, permeation injection is applied on low-permeability silty sand in a laboratory setting and then direct shear tests are undertaken. The results indicate colloidal silica concentrations should be greater than 10% to meet water resistance and strength requirements, while lower than 30% to ensure a uniform distribution of grout and adequate penetration. A low injection pressure of between 45 and 55 kPa, and between 65 and 75 kPa, is found to be suitable for permeating 20% and 30% concentrations of colloidal silica, respectively. After 7 days of curing time, silty sand at natural moisture content and treated with a 20% concentration of colloidal silica shows an increase in peak strength of between 58.1% and 78.4%, which increases further with curing time. A 20% concentration of colloidal silica is recommended for treating silty sand with a coefficient of permeability in the range 10−6 m/s, based on both injection range and peak strength after treatment. These findings may guide the practice of permeation grouting for low-permeability soils.

Chemical mechanical planarization (CMP) is a wafer-surface-polishing planarization technique based on a wet procedure that combines chemical and mechanical forces to fully flatten materials for semiconductors to be mounted on the wafer surface. The achievement of devices of a small nano-size with few defects and good wafer yields is essential in enabling IC chip manufacturers to enhance their profits and become more competitive. The CMP process is applied to produce many IC generations of nanometer node, or those of even narrower line widths, for a better performance and manufacturing feasibility. Slurry is a necessary supply for CMP. The most critical component in slurry is an abrasive particle which affects the removal rates, uniformity, defects, and removal selectivity for the materials on the wafer surface. The polishing abrasive is the source of mechanical force. Conventional CMP abrasives consist of colloidal silica, fume silica or other inorganic polishing particles in the slurries. We were the first to systematically study nanoparticles of the polymer type applied in CMP, and to compare traditional inorganic and polymer nanoparticles in terms of polishing performance. In particular, the polymer nanoparticle size, shape, solid content dosing ratio, and molecular types were examined. The polishing performance was measured for the polishing removal rates, total defect counts, and uniformity. We found that the polymer nanoparticles significantly improved the total defect counts and uniformity, although the removal rates were lower than the rates obtained using inorganic nanoparticles. However, the lower removal rates of the polymer nanoparticles are acceptable due to the thinner film materials used for smaller IC device nodes, which may be below 10 nm. We also found that the physical properties of polymer nanoparticles, in terms of their size, shape, and different types of copolymer molecules, cause differences in the polishing performance. Meanwhile, we used statistical analysis software to analyze the data on the polishing removal rates and defect counts. This method helps to determine the most suitable polymer nanoparticle for use as a slurry abrasive, and improves the reliability trends for defect counts. [ABSTRACT FROM AUTHOR]

This paper focuses on the recent advance in no-cement technology, mainly focusing on their properties, benefits, and prospects when calcium aluminate cement is replaced by a "dry-version" silica binder, using microsilica powder to replace silica-sol. A microsilica-gel bond system has been designed using microsilica powder and a tailor-made dispersant package to give excellent flow and to control the setting behaviour of the NCCs. The flow, set-behaviour and mechanical properties have been studied in comparison with silica-sol bonded NCCs and cement-bonded low cement castables (LCC). The microsilica-gel bonded NCCs not only exhibit higher flow, better workability and adequate green strength compared to the silica-sol bond system, but also entail easier handling, storage, and transportation thanks to the all-in-the-bag solution. The microsilica-gel bond system contains only a minor amount of cement as gelling agent; hence, the hot properties are much better than that of LCCs. Phase transformations and bond mechanism were investigated by SEM and XRD techniques after pre-firing at 1400 and 1500°C. Furthermore, the effect of drying agents on both lab- and industrial-scale explosion resistance was studied. The drying behaviour and explosion resistance of microsilica-gel bonded NCCs was further significantly improved by using a speciality drying agent (EMSIL-DRY™); a perfect 400 kgs block was produced with no problems using a fast-firing program (20°C to 850°C at a heating rate of 50°C). [ABSTRACT FROM AUTHOR]

Colloidal silica (CS) grouting is a soil improvement technique introduced as an innovative remedial measure against seismic liquefaction. It consists of injecting soils with a time-hardening, nanosilica-based solution forming a silica gel among soil particles. This paper presents the results of an experimental study on the effects of an initial static shear stress on the behaviour of a cyclically loaded clean sand stabilised with 5% CS. Undrained cyclic triaxial tests were performed to analyse the cyclic response of loose untreated and stabilised sand specimens, isotropically or anisotropically consolidated at the same initial mean effective stress. The consolidation stage was used to provide insight on the compressibility of stabilised soil. Stress–strain behaviour, pore water pressure response and cyclic shear resistance were investigated. The results showed that: (i) stabilised sand exhibits higher compressibility than the untreated one during isotropic consolidation; (ii) cyclic strength is higher for stabilised sand than for the untreated one, increasing as the degree of anisotropic initial stress increases; and (iii) extra pore water pressure development does not depend on the degree of initial anisotropy for stabilised sand, while the same does not hold for untreated sand. Simplified relationships are proposed to describe the consolidation process and the residual extra pore water pressure build-up process. [ABSTRACT FROM AUTHOR]

The traditional soil stabilization techniques, which primarily include calcium-rich additives, are gradually replaced by environmentally friendly techniques as the former increases the carbon footprint emissions. On the other hand, nanomaterials (particles with a size range of less than 100 nm) are gaining acceptance in geotechnical and geoenvironmental engineering due to their non-toxic nature and less energy consumption required for production. These materials have entirely different properties from conventional materials. When mixed with soil particles, their relatively larger specific surface area values trigger an easy and rapid reaction. The paper reviews the applicability of select nanomaterials such as metallic nanoparticles (which include nano-copper oxide (nano-CuO), nano-magnesium oxide (nano-MgO), iron oxide nanoparticles (nano-Fe2O3), nano-alumina (nano-Al2O3), nano-clay, nano-silica (nano-SiO2), colloidal silica, to name a few, in the areas of geotechnical and geoenvironmental engineering by highlighting the associated mechanisms of interaction. The targeted geotechnical properties include plasticity, compressibility, consolidation, permeability, and strength characteristics under different conditions. Further, the effect of the select nanoparticles on microbial activity, their applicability in remediation of organic and inorganic contaminants from different soil–water systems, and their cost-effectiveness are discussed. [ABSTRACT FROM AUTHOR]

Jin Kyeong Choi1 &ast;, Jun-Young Park2 &ast;, Soyoung Lee,3 Young-Ae Choi,4 Song Kwon,2 Min Jun Shin,2,5 Hui-Suk Yun,6 Yong Hyun Jang,7 Jinjoo Kang,4 Namkyung Kim,4 Dongwoo Khang,2,5,8 Sang-Hyun Kim4 1Department of Immunology, Jeonbuk National University Medical School, Jeonju, 54907, Republic of Korea1; 2Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Incheon, 21999, Republic of Korea; 3Immunoregulatory Materials Research Center, Korea Research Institute of Bioscience and Biotechnology, Jeongeup, 56212, Republic of Korea; 4CMRI, Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea; 5Department of Health Sciences and Technology, GAIHST, Gachon University, Incheon, 21999, Republic of Korea; 6Powder & Ceramics Division, Korea Institute of Materials Science, Changwon, 51508, Republic of Korea; 7Department of Dermatology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea; 8Department of Physiology, School of Medicine, Gachon University, Incheon, 21999, Republic of Korea&ast;These authors contributed equally to this workCorrespondence: Dongwoo Khang, Department of Physiology, School of Medicine, Gachon University, Incheon, 21999, Republic of Korea, Tel +82 32 899 6515, Email dkhang@gachon.ac.kr Sang-Hyun Kim, Department of Pharmacology, School of Medicine, Kyungpook National University, Daegu, 41944, Republic of Korea, Tel +82 53 420 4838, Email shkim72@knu.ac.krPurpose: The protein corona surrounding nanoparticles has attracted considerable attention as it induces subsequent inflammatory responses. Although mesoporous silica nanoparticles (MSN) are commonly used in medicines, cosmetics, and packaging, the inflammatory effects of the MSN protein corona on the cutaneous system have not been investigated till date.Methods: We examined the greater plasma protein adsorption on MSN leads to serious inflammatory reactions in Dermatophagoides farinae extract (DFE)-induced mouse atopic dermatitis (AD)-like skin inflammation because of increased uptake by keratinocytes.Results: We compare the AD lesions induced by MSN and colloidal (non-porous) silica nanoparticles (CSN), which exhibit different pore architectures but similar dimensions and surface chemistry. MSN-corona treatment of severe skin inflammation in a DFE-induced in vivo AD model greatly increases mouse ear epidermal thickness and infiltration of immune cells compared with the CSN-corona treatment. Moreover, MSN-corona significantly increase AD-specific immunoglobulins, serum histamine, and Th1/Th2/Th17 cytokines in the ear and lymph nodes. MSN-corona induce more severe cutaneous inflammation than CSN by significantly decreasing claudin-1 expression.Conclusion: This study demonstrates the novel impact of the MSN protein corona in inducing inflammatory responses through claudin-1 downregulation and suggests useful clinical guidelines for MSN application in cosmetics and drug delivery systems.Graphical Abstract: Keywords: protein Corona, atopic dermatitis, mesoporous silica, colloidal silica, claudin-1, immunotoxicity

d6r units were proved to be crucial for the synthesis of SSZ-16 zeolite with AFX topology, and FAU zeolite owning plenty of d6r units was chosen as the essential raw material for constructing AFX frameworks. In this work, SSZ-16 zeolite was directly synthesized using colloidal silica and sodium aluminate as the raw materials in short crystallization time of 5 h. The corresponding crystallization process were carefully investigated by various characterizations, demonstrating that the key to this success was the formation of d6r units built up by a large amount of s4r units which were formed with the assistance of the appropriate organic structure directing agent (OSDA) and seeds in the synthetic media. Interestingly, the products of C-SSZ-16 zeolites presented spherical shapes consisted of relatively small particles with size range from 30 to 50 nm. Moreover, after ion-exchanged with Cu ions, the Cu-C-SSZ-16 products showed excellent performance in the selective catalytic reduction of NO x with NH 3 (NH 3 -SCR) and better hydrothermal stability than conventional Cu-SSZ-16-con samples due to slightly higher Si/Al ratio of the Cu-C-SSZ-16. Therefore, remarkable catalytic performance and the use of low-cost raw materials as well as short period of synthesis time make AFX zeolites as potential applicants in NH 3 -SCR field, from an industrial viewpoint. [Display omitted] • SSZ-16 zeolite was synthesized directly using colloidal silica and sodium aluminate as raw materials. • Plenty of d6r units were built up by a large amount of s4r units with the assistance of the OSDA and seeds. • The Cu-based SSZ-16 product shows excellent activity and high hydrothermal stability in the NH 3 -SCR reaction. [ABSTRACT FROM AUTHOR]

Medical-grade ultrahigh molecular weight polyethylene (UHMWPE) is the material of choice for sliding surfaces in various articular joint implants owing to its excellent biocompatibility and superior physical properties, such as an exceptionally low coefficient of friction and excellent durability. However, the bioinert nature of UHMWPE limits its extended use in rapidly advancing medical fronts. In this study, bioactive surface modifications of UHMWPE were addressed using a newly developed laser-melt infiltration technique. UHMWPE was coated with binary mixtures of strontium apatite and colloidal silica particles and irradiated using a 30 W CO2 laser to reach the maximum temperature of 150 ± 5 °C. UHMWPE melts infiltrated the porous matrices of the coatings by capillary force and formed surface-selective composite materials between them. Capillary rise heights were evaluated by observing the uplift of the substrate after the selective dissolution of the coating substances and were found to be much higher than the estimated values based on the Lucas–Washburn equation. This finding suggests that the melt viscosity of UHMWPE confined within the nanopores might be significantly lower than that measured at macroscopic scales. Both strontium and silicate ions are known osteo-inductive factors, and their concentrations eluted from the binary coatings were substantially higher than those found in the single coatings. [ABSTRACT FROM AUTHOR]

This article examines the characteristics of shotcrete from the standpoint of resistance to plastic shrinkage cracking. The effects of 2%, 3%, and 4% replacement with colloidal silica (CS) with a 10-nm particle size on the performance of shotcrete was examined, as were the effects of addition of supplementary cement materials in combination with CS, such as silica fume (SF) and ultra-fine fly ash (UFFA). Plastic cracking was examined from three perspectives: its effect on strength development (especially at the initial stage), assessment of plastic shrinkage in accordance with the ASTM C1579, and related issues of bleeding and evaporation. Compressive and flexural strength tests were conducted to gain an understanding of the processes involved, and the Intelligent Crack Viewer FCV-30 was used to estimate crack widths. The results show that the replacement with CS increases the compressive and flexural strength during hardening, which increases its resistance to tensile shrinkage stresses. The practical assessment of cracks showed that a significant reduction in the width of plastic shrinkage cracks was also achieved. The combination of 4% SF and 2% CS significantly reduced the risk of cracking and improved strength characteristics. The application of CS reduced the effect of 20% UFFA on plastic cracking. [ABSTRACT FROM AUTHOR]

The present study fabricated high-performance silica/epoxy resin nanocomposites having a low coefficient of linear thermal expansion (CTE) and a high glass transition temperature (T g). This was accomplished by dispersing colloidal silica nanospheres having hydrophilic surfaces in epoxy resins, which limited the motion of the polymer chains. Nanocomposites were produced wherein isolated primary particles of colloidal silica without silane surface modification were dispersed uniformly. These particles were generated via the breakdown of loosely bound agglomerates of spherical silica particles during the agitation of a dispersion in an epoxy resin solution. Hydrogen bonding between hydroxyl groups on the hydrophilic surfaces of the dispersed silica nanoparticles and the cross-linked epoxy polymer network evidently limited thermally-induced motion of the polymer chains, resulting in a considerable reduction in the CTE and an increase in the T g for the nanocomposite. Graphical Abstract [ABSTRACT FROM AUTHOR]

Fucosylated glycosaminoglycans (FGs) derived from sea cucumbers exhibit potent intrinsic Xase (iXase) inhibition, anticoagulation, and antithrombosis. Plasma activated partial thromboplastin time (APTT), a widely used screening test worldwide, is crucial for evaluating anticoagulant efficacy. However, the applicability of these commercially available APTT reagents for assessing anticoagulation of FGs remains unreported. In this study, we investigated the disparity between ellagic acid and colloidal silica APTT reagents in evaluating anticoagulation of dHG-5 and dHLFG-4, two depolymerized FGs, and elucidated the underlying rationale. The results demonstrated that dHG-5 and dHLFG-4 exhibited heightened sensitivity to the ellagic acid APTT reagent both in vitro and in vivo, and did not significantly affect the activation of APTT reagents for plasma. In addition, both ellagic acid and colloidal silica APTT reagents inhibited the anti-iXase of dHG-5 and dHLFG-4, and the inhibition of the ellagic acid APTT reagent was less pronounced compared to the colloidal silica APTT reagent. These findings suggest that the reduced impact of the ellagic acid APTT reagent on the anti-iXase activity of dHG-5 and dHLFG-4 is responsible for the increased sensitivity in plasma APTT analysis. This study offers valuable insights into the characteristics of two APTT reagents applied for assessing the anticoagulant activity of FG-related compounds.

Recently, as an alternative solution for overcoming the scaling-down limitations of logic devices with design length of less than 3 nm and enhancing DRAM operation performance, 3D heterogeneous packaging technology has been intensively researched, essentially requiring Si wafer polishing at a very high Si polishing rate (500 nm/min) by accelerating the degree of the hydrolysis reaction (i.e., Si-O-H) on the polished Si wafer surface during CMP. Unlike conventional hydrolysis reaction accelerators (i.e., sodium hydroxide and potassium hydroxide), a novel hydrolysis reaction accelerator with amine functional groups (i.e., 552.8 nm/min for ethylenediamine) surprisingly presented an Si wafer polishing rate >3 times higher than that of conventional hydrolysis reaction accelerators (177.1 nm/min for sodium hydroxide). This remarkable enhancement of the Si wafer polishing rate for ethylenediamine was principally the result of (i) the increased hydrolysis reaction, (ii) the enhanced degree of adsorption of the CMP slurry on the polished Si wafer surface during CMP, and (iii) the decreased electrostatic repulsive force between colloidal silica abrasives and the Si wafer surface. A higher ethylenediamine concentration in the Si wafer CMP slurry led to a higher extent of hydrolysis reaction and degree of adsorption for the slurry and a lower electrostatic repulsive force; thus, a higher ethylenediamine concentration resulted in a higher Si wafer polishing rate. With the aim of achieving further improvements to the Si wafer polishing rates using Si wafer CMP slurry including ethylenediamine, the Si wafer polishing rate increased remarkably and root-squarely with the increasing ethylenediamine concentration. [ABSTRACT FROM AUTHOR]

Colloidal silica (CS) is a kind of nanomaterial used in soil/rock grouting techniques in different branches of civil engineering. Many studies have recently been performed to investigate the potential of CS in improving the mechanical behavior of cohesionless soils and mitigating the risk of seismic liquefaction in urbanized areas. CS grout is chemically and biologically inert and, when injected into a subsoil, it can form a silica gel and stabilize the desired soil layer, thus representing an attractive, environmentally friendly alternative to standard chemical grouting techniques. This paper firstly describes the characteristics of CS grout, the gelation process and the main features of the behavior of the pure gelled material. The grout delivery mechanisms through porous media are then explained, pointing out the crucial issues for practical application of CS grouting. All the grouting-induced effects on the soil behavior, which have been investigated by laboratory tests on small-sized soil elements, are reviewed, including the modifications to soil strength and stiffness under both static and seismic loading conditions, to soil compressibility and hydraulic conductivity. Published results from physical model tests and in situ applications are also presented. Finally, some aspects related to the mechanism of soil improvement are discussed. A critical discussion of each topic is presented, drawing particular attention to the controversial or not yet fully examined aspects to which future research on colloidal silica grouting should be directed.

This paper presents a laboratory investigation into the mechanical response of a silty sand, with a fines content of 10%, stabilized with colloidal silica (CS). To this end, a series of unconfined compression tests as well as monotonic and cyclic triaxial tests was performed on a silty sand, comprising a mixture of a clean sand and a silty sand, stabilized with two concentrations of CS. The effect of various parameters on the behaviour of the stabilized silty sand was studied, such as CS concentration, soil density, and the presence of fines. The test results were compared with the corresponding of the untreated silty sand as well as the parent clean sand. It is shown that stabilization, even at the lowest CS = 6% concentration studied, significantly improves the undrained shear strength as well as the liquefaction resistance of the stabilized silty sand. Both the monotonic and cyclic response of the stabilized soil are only slightly affected by density. Furthermore, cyclic straining up to at least 5% of double-amplitude axial strain does not influence the undrained shear strength of the stabilized silty sand.

The investigation focused on the rheological impact of sodium chloride and calcium chloride on PEO silica water mixtures, specifically studying their gelation/shear thickening behaviour referred to as "shake gels". Monitoring viscosity over time at a constant shear rate revealed a significant increase in viscosity by several orders of magnitude at a specific time point. Interestingly, higher concentrations of sodium chloride and calcium chloride correlated with shorter times required for gel formation. Following gel formation, dropping the shear rate facilitated the observation of the gel's relaxation back into a liquid state. Notably, higher concentrations of sodium chloride or calcium chloride resulted in slower relaxation processes. Furthermore, a notable difference emerged: at a consistent shear rate, calcium chloride exhibited faster gelation compared to sodium chloride, while during relaxation, calcium chloride relaxed at a slower pace than sodium chloride. This behaviour can be attributed to the effect of salt on polymer molecules. The presence of salt results in reduction in Debye length and polymer gets contracted. Consequently, shearing becomes more easier even though at lower shear rate as salt concentration increases. In contrast, during the relaxation process, polymer restructuring is hindered due to electrostatic repulsion and Debye length decreases, resulting in slower relaxation as salt concentration increases. The variations in gelation and relaxation behaviour between different salts can primarily be attributed to the differing ionic strengths exhibited by these salts. [Display omitted] [ABSTRACT FROM AUTHOR]