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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 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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

In this work, we explore a novel mineral processing approach using carbon dioxide to promote mineral alterations that lead to improved extractability of nickel from olivine ((Mg,Fe)2SiO4). The precept is that by altering the morphology and the mineralogy of the ore via mineral carbonation, the comminution requirements and the acid consumption during hydrometallurgical processing can be reduced. Furthermore, carbonation pre-treatment can lead to mineral liberation and concentration of metals in physically separable phases. In a first processing step, olivine is fully carbonated at high CO2 partial pressures (35 bar) and optimal temperature (200 °C) with the addition of pH buffering agents. This leads to a powdery product containing high carbonate content. The main products of the carbonation reaction include quasi-amorphous colloidal silica, chromium-rich metallic particles, and ferro-magnesite ((Mg1−x,Fex)CO3). Carbonated olivine was subsequently leached using an array of inorganic and organic acids to test their leaching efficiency. Compared to leaching from untreated olivine, the percentage of nickel extracted from carbonated olivine by acid leaching was significantly increased. It is anticipated that the mineral carbonation pre-treatment approach may also be applicable to other ultrabasic and lateritic ores.

Chemical Mechanical Planarization (CMP) is a process that is now routinely used to planarize metal as well dielectric films during the fabrication of integrated circuits. This process uses slurries comprised of fine abrasive particles, such as silica, ceria or alumina. The stability and performance of the slurries are influenced by the size and properties of these particles, which in turn are influenced by their synthesis route. Stability is important to improve slurry lifetime and minimize defects such as microscratching caused by particle agglomerates or large particle counts (LPC) during polishing. The rheological behavior of slurry affects the friction at the pad-particle-wafer interface and alters the material removal rate. It is, thus, necessary to carefully engineer the slurry characteristics to achieve good removal rate and planarity without causing defects. This paper reviews the published literature on the synthesis of abrasive particles used in the preparation of CMP slurries as well as stability and rheological characteristics of slurries made from these particles. A brief account of particle-film interactions and importance of LPC in wafer scratching is also provided.

Silica nano-particles are suspended in the colloidal silica and can be induced to gradually gel after the PH value changes. Thus colloidal silica can be utilized to rapidly seep through loose calcareous sand, and the silicon gel is gradually formed to bond sand particles. However, based on observation by scanning electron microscope(SEM), there are a lot of microcracks in the silica gel, which reduces the strength of the sand-gel composite. Therefore, in order to suppress crack growth, wood fibers are dispersed in the colloidal silica which still can seep through calcareous sand. 18 silicon-gel stabilized sand samples were prepared for tri-axial tests, where the concentration of colloidal silica is 20%, and wood fiber concentrations are 0%, 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, respectively. The results show that:(1) there exists an optimum ratio of wood fiber to colloidal silica, that is, as the concentration of wood fiber increases, the strength represented by the peak value of deviator stress rises first and then falls; (2) there are opposite trends between the two strength parameters, internal friction angle and cohesion, that is, when the wood fiber concentration is 0.04%, the cohesion reaches the maximum value and the internal friction angle reaches the minimum value; (3) The photos by SEM show that, there are wood fibers on the inner wall of the crack in the silica gel, which may reduce the extent of crack propagation and contribute to the strength of stabilized sand samples.

Foram produzidas amostras de amido termoplástico (TPS) reforçadas com materiais de alta área superficial, com o intuito de verificar a variação nas propriedades do polímero, com especial enfoque na sua permeabilidade a vapor d'água. Foram utilizadas como carga a sílica coloidal (área superficial de 122,7 m²/g) e uma zeólita do tipo ZSM-5, produzida em laboratório (área superficial de 261,3 m²/g), em teores de 2 a 10% em massa. Os resultados demonstraram que a adição de ambos os materiais melhorou as propriedades mecânicas do TPS, embora nos maiores teores houve redução da qualidade das interfaces e dessas propriedades, principalmente para a ZSM-5. Em todos os casos a introdução da carga inorgânica reduziu a permeabilidade ao vapor d'água em até 20% quando comparada à permeabilidade do TPS, porém a melhor dispersão da sílica coloidal na matriz permitiu as maiores reduções, apesar da área superficial inferior.Compositions of thermoplastic starch (TPS) reinforced by high surface area materials were produced, intending to study the variation in polymer properties, focusing on the permeability to water vapor. Colloidal silica (surface area 122.7 m²/g) and a ZSM-5 zeolite (surface area 261.3 m²/g) were used, in loadings from 2 to 10% weight. The results demonstrated that the addition of both materials was favorable to the TPS mechanical properties, however in higher loadings the quality of polymer interfaces and these properties were negatively affected, especially for ZSM-5. In all the cases the inorganic particles reduced the permeability to water vapor in levels below 20% when compared to pure TPS, although the best dispersion of colloidal silica determined better reductions, despite its lower surface area.

To overcome the challenges of mineral CO2 sequestration, Innovation Concepts B.V. is developing a unique proprietary Gravity Pressure Vessel (GPV) reactor technology, and has focussed on generating reaction products of high economic value. The GPV provides intense process conditions through hydrostatic pressurization and heat exchange integration that harvests exothermic reaction energy, thereby reducing energy demand of conventional reactor designs, in addition to offering other benefits. In this paper, a perspective on the status of this technology and outlook for the future is provided. To date, laboratory-scale tests of the envisioned process have been performed in a tubular rocking autoclave reactor. The mineral of choice has been olivine (~Mg1.6Fe2+0.4(SiO4) + ppm Ni/Cr), although asbestos, steel slags and oil shale residues are also under investigation. The effect of several process parameters on reaction extent and product properties have been tested: CO2 pressure, temperature, residence time, additives (buffers, lixiviants, chelators, oxidizers), solids loading, and mixing rate. The products (carbonates, amorphous silica and chromite) have been physically separated (based on size, density and magnetic properties), characterized (for chemistry, mineralogy and morphology) and tested in intended applications (as pozzolanic carbon-negative building material). Economically, it is found that product value is the main driver for mineral carbonation, rather than, or in addition to, the sequestered CO2. The approach of using a GPV and focusing on valuable reaction products could thus make CO2 mineralization a feasible and sustainable industrial process.

A avaliação do emprego de concretos refratários nanoligados em aplicações onde ocorre desgaste por erosão é de importante interesse devido aos estudos recentes que indicam esta rota como uma alternativa à substituição do cimento de aluminato de cálcio. Neste trabalho, os resultados de resistência à erosão a frio de formulações de concretos refratários de alta alumina ligados por sílica coloidal e a combinação deste aditivo com alumina hidratável, foram comparadas a um concreto refratário aluminoso de uso comercial, ligado por cimento de aluminato de cálcio, especificado pelo fabricante para uso em aplicações de desgaste por erosão. Os resultados mostraram um desempenho superior dos concretos nanoligados, indicando que a utilização deste agente ligante é muito promissora no desenvolvimento de produtos onde se requer alta resistência ao desgaste por erosão. A razão entre o valor do módulo de ruptura a quente e o volume erodido também se mostrou relevante como técnica de seleção de refratários para tais aplicações.Nanobonded refractory castables for erosion wear applications is of important interest based on recent publications that suggest the use of this route as an alternative to substitute the calcium aluminate cements. In this work, the cold erosion resistance of high-alumina refractory castables containing colloidal silica and a blend of colloidal silica and hydratable alumina as bonding agents were comparated to commercial calcium aluminate cement containing alumina refractory castable, specified by the producer as a suitable material for erosion wear applications. The results showed higher performance for the colloidal silica bonded castables, suggesting the use of this bonding system in the development of refractory castables for erosion wear applications. The ratio between the hot modulus of rupture and the eroded volume has also been shown as a relevant technique for the refractories selection in such environments.

Concretos mulitizados são comumente utilizados na indústria siderúrgica devido as suas excelentes propriedades. Entretanto, a presença de cimento de aluminato de cálcio, juntamente com SiO2, forma eutéticos e fases de baixo ponto de fusão, motivando assim a seleção de ligantes alternativos. Neste trabalho os três principais ligantes para refratários (cimento de aluminato de cálcio, alumina hidratável e sílica coloidal) foram incorporados em concretos com alto potencial de mulitização e suas propriedades a verde e a quente foram comparadas, definindo quais ligantes apresentam melhor desempenho. Os resultados indicam que a sílica coloidal, além de facilitar a etapa de secagem, resulta em excelentes propriedades a quente e em menor teor de líquido residual após queima, quando comparados com uma composição referência de alta alumina.Mullite based castables are usually applied for lining steel industries processing ladles due to their superior working performance. However, the presence of aluminate cement and SiO2 can deteriorate their hot properties by the formation of eutectics and low melting point phases, which motivates the search for alternatives biding systems. In this paper, the three main binders for refractory castables (aluminate cement, hydratable alumina and colloidal silica) were added to different compositions and their green and hot properties were compared, aiming to define which one presents better performance. The results indicated the colloidal silica as a promising substitute to the aluminate cement as it favors the drying process, provides excellent hot properties, higher refractoriness and generates low residual liquid phase after sintering, when compared to a high alumina composition.

Abstract Incorporation of nanoparticles composed of surface-functionalized fumed silica (FS) or native colloidal silica (CS) into a nanostructured block copolymer yields hybrid nanocomposites whose mechanical properties can be tuned by nanoparticle concentration and surface chemistry. In this work, dynamic rheology is used to probe the frequency and thermal responses of nanocomposites composed of a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer and varying in nanoparticle concentration and surface functionality. At sufficiently high loading levels, FS nanoparticle aggregates establish a load-bearing colloidal network within the copolymer matrix. Transmission electron microscopy images reveal the morphological characteristics of the nanocomposites under these conditions.

In this study, alkaline colloidal silica was prepared by titration of an alkaline solution such as sodium silicate with silicic acid in constant range of pH .This constant range of pH was achieved by using concentrated soduim silicate solutions as pH adjusting solutions during titration.The sodium silicate solutions having a variety of concentrations were passed through ion-exchange resin to prepare the silicic acid solutions. Various effective parameters on the method were investigated. In this research, the results show the mean particle size and surface area of prepared colloidal silica are influenced by formation temperature, titration rate, silicic acid and alkaline solutions concentration. Low titration rate of slicic acid, high formation temperature and low concentration of silicic acid and alkaline solution would help the particle growth to form the larger particle size of colloidal silica.

Os cimentos de aluminatos de cálcio (CAC) são os ligantes hidráulicos mais utilizados em concretos refratários. No entanto, a presença de CaO em sua composição pode limitar seu uso em elevadas temperaturas nos sistemas Al2O3-SiO2 e Al2O3-MgO. Como importante alternativa ao uso do CAC, destaca-se a sílica coloidal, que proporciona, dentre outras vantagens, maior velocidade de secagem e reatividade ao sistema. Estudos anteriores dos autores deste trabalho indicaram que a adição de microssílica e alumina hidratável podem otimizar o desempenho de concretos contendo sílica coloidal como agente ligante. No entanto, investigações sobre esses sistemas em elevadas temperaturas de trabalho são escassas na literatura. Neste trabalho, o comportamento em diferentes temperaturas de sistemas contendo sílica coloidal foi avaliado quanto à retração linear após queima, porosidade aparente, resistência mecânica a frio e a quente. Como referência, foi utilizada uma formulação de concreto contendo cimento de aluminato de cálcio como agente ligante.Calcium aluminate cements (CAC) are the most used hydraulic binders in refractory castables. However the presence of CaO in the castable composition reduces the refractoriness in the Al2O3-SiO2 and Al2O3-MgO systems. In this context, colloidal silica has been pointed out as an important alternative for the CAC use because promotes, among another advantages, easier drying behavior and higher reactivity to the system. Previous works of the authors have indicated that the microsilica and hydratable alumina addition to colloidal silica containing castables can optimize their performance. Nevertheless, researches in these systems at high working temperatures (above 350 ºC) are scarce in the literature. In this work, the colloidal silica bonded castables behaviors at different working temperature were analyzed through the fired linear shrinkage, apparent porosity, mechanical strength and hot modulus of rupture. The obtained results were compared to the CAC containing castable compositions.

Sílica coloidal e alumina hidratável destacam-se como importantes alternativas à substituição do cimento de aluminato de cálcio como agentes ligantes para concretos refratários aluminosos. Baseando-se nas vantagens e desvantagens destes agentes ligantes isentos de CaO, é razoável supor que a combinação de ambos poderia maximizar os benefícios e reduzir os aspectos negativos observados quando estes são individualmente aplicados. A elevada permeabilidade devido à presença de sílica coloidal poderia reduzir os riscos de explosão durante a secagem das composições ligadas por alumina hidratável. Em paralelo, a porosidade total do sistema contendo sílica coloidal poderia ser diminuída devido à presença de alumina hidratável. Neste trabalho, o desempenho de concretos refratários aluminosos contendo sílica coloidal e alumina hidratável como sistema ligante foram avaliados quanto ao comportamento de mistura, permeabilidade, porosidade aparente, resistência mecânica e perfil de secagem.Colloidal silica and hydratable alumina can be pointed out as important substitutes to the calcium aluminate cements as calcium-free binders for refractory castables. Based on the advantages and drawbacks of these binders, it is reasonable to consider that their combination could maximize the advantages and reduce the negative aspects observed when they are individually used. The high permeability level generated by the colloidal silica would reduce the risks of explosive spalling of hydratable alumina containing castables during first heat-up. Additionally, the total porosity of the colloidal silica containing systems could be decreased due to the hydration of the HA. In the present work, colloidal silica and hydratable alumina were combined in a new calcium-free binding system. Their rheological behavior, permeability level, apparent porosity, mechanical strength and drying rate profile were compared with the performance of each binder individually.

Flexible and transparent conducting electrodes are essential for future electronic devices. In this study, we successfully fabricated a highly-interconnected metal-mesh structure (MMS) using a self-formable cracked template. The template—fabricated from colloidal silica—can be easily formed and removed, presenting a simple and cost-effective way to construct a randomly and uniformly networked MMS. The structure of the MMS can be controlled by varying the spin-coating speed during the coating of the template solution or by stacking of metal-mesh layers. Through these techniques, the optical transparency and sheet resistance of the MMS can be designed for a specific purpose. A double-layered Al MMS showed high optical transparency (~80%) in the visible region, low sheet resistance (~20 Ω/sq), and good flexibility under bending test compared with a single-layered MMS, because of its highly-interconnected wire structure. Additionally, we identified the applicability of the MMS in the case of practical devices by applying it to electrodes of thin-film transistors (TFTs). The TFTs with MMS electrodes showed comparable electrical characteristics to those with conventional film-type electrodes. The cracked template can be used for the fabrication of a mesh structure consisting of any material, so it can be used for not only transparent electrodes, but also various applications such as solar cells, sensors, etc.

Cembinder, Eka EXP36, and MEYCO MP320 are three colloidal silica materials that have been proposed for post-excavation grouting of deep tunnels in a radioactive waste repository. In this study, samples of these colloidal silicas were tested for their particle size distribution, gel induction time (tG), gel time (TG), and physical erosion, under mildly saline groundwater flow conditions. In order to achieve a desired gel time range, from 15 to 50 min, it is recommended that the colloidal silica is mixed with a NaCl accelerator at a 5:1 volume ratio. At 20 °C, the concentration range for the NaCl solution should be 1.5 to 1.7 M for MEYCO, 1.23 to 1.38 M for Eka EXP36, and 1.3 to 1.47 M for Cembinder. The physical erosion of the set silicas remained steady during a 10 h flow cell experiment, when grouts were subjected to 0.05 M NaCl at a superficial velocity of 2.2 × 10−5 m/s. For these test conditions, the results show that MEYCO has the highest average erosion rate (0.85 mg/h) of the three grout materials, as well as the greatest variability in this rate. Cembinder performed best with the lowest silica removal rate. Extrapolation of the measured erosion rates suggests that grout fracture dilation would not be significant under natural quiescent groundwater flow conditions, but would be high if there was hydraulic communication between the geosphere and the repository.

Two different samples of monodisperse Stöber silica particles were examined in the analytical transmission electron microscope, using different imaging modes: bright-field, dark-field, energy-loss and elemental distribution maps. The particles (effective diameters = 141 and 36 nm) are formed by domains of variable O/Si ratio, which is consistent with a variable degree of hydration, and they coexist with particles with a high O/Si ratio measuring a few nanometers only, which appear dispersed in the picture background. Bright-field and energy-loss images of the larger particles show a core-and-shell morphology, and the shells have a higher amount of high-O/Si domains as well as contaminating carbon compounds. On the other hand, the smaller particles (effective diameter = 36 nm) are also formed by distinct domains, but their morphology is neither spherical or core-and-shell. The mechanisms for particle formation presented in the literature are discussed, considering the present findings.

Sol-gel process is a suitable method for the production of glass-like coatings onto metals, acting as barrier against oxidation and providing an increased resistance to corrosion. Hybrid and inorganic coatings of different compositions have been used for coating several metals by using techniques like dipping, spin-coating and spraying. Although these methods lead to good properties the final coatings are restricted by the thin thickness (up to 2 μm), thus limiting the application range. Electrophoretic deposition (EPD) is considered a highly versatile technique for producing homogeneous thicker coatings. The aim of this work deals with the preparation of coatings onto metals by EPD from hybrid silica sols (TEOS, MTES) and from colloidal silica suspensions where the hybrid sols constitute the suspending medium. Both the solutions and the suspensions have been studied in terms of viscosity, density and conductivity. Furthermore, the physical parameters associated to EPD, such as deposition time and current density, have been also studied, taking into account the additional contribution to the layer formed by EPD occurring by dipping during withdrawal. The coatings obtained by dipping and by EPD have been characterised by perfilometry and optical microscopy.El proceso sol-gel es un método de gran interés para la producción de películas vítreas sobre metales, que actúan como barrera protectora frente a la oxidación y aumentan su resistencia a la corrosión. Se han obtenido recubrimientos inorgánicos e híbridos de distintas composiciones sobre distintos metales usando técnicas como inmersión, centrifugado y pulverización. Aunque estos métodos proporcionan recubrimientos con buenas propiedades los espesores obtenidos son bajos (inferiores a 2 mm), lo que limita sus posibilidades de aplicación. La deposición electroforética (EPD) se perfila como una técnica de gran versatilidad para la obtención de recubrimientos homogéneos de mayor espesor. El objetivo de este trabajo es la preparación de recubrimientos sobre metal por EPD a partir de soluciones híbridas de SiO2 (TEOS, MTES) y de suspensiones coloidales de SiO2 en las que las propias soluciones híbridas actúan como medio de dispersión. Tanto las soluciones como las suspensiones se han estudiado mediante medidas de viscosidad, densidad y conductividad. Asimismo, se han estudiado los parámetros físicos asociados a la EPD, tales como el tiempo de deposición y la densidad de corriente, teniendo en cuenta el efecto adicional de formación de capa por inmersión durante la extracción. Los recubrimientos se han caracterizado mediante perfilometría y microscopía óptica, comparando las capas depositadas por inmersión y las obtenidas por EPD.