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The significant progress of non-precious metal cathodic electrocatalytic materials is impressive in electrochemical energy conversion application. Here, iron and nitrogen co-doped porous carbon spheres (Fe/N-PCS) have been designed via 3-aminophenol/formaldehyde (APF) resin spheres as carbon precursor, ferric nitrate as iron source, colloidal silica as template and tetramethylguanidine as catalyst by the improved Stober method. Fe/N-PCS possesses uniform spherical morphology, abundant mesoporous shape and high surface area and exhibits higher oxygen reduction reaction (ORR) electrocatalytic activity (E1/2, 0.838 V vs. RHE) compared with the Pt/C (E1/2, 0.827 V vs. RHE) in alkaline media. In addition, the methanol tolerance and catalytic stability of Fe/N-PCS are greater than commercial Pt/C catalyst. The outstanding ORR behavior of Fe/N-PCS mainly benefits from the iron and nitrogen elements synergistic effect, pyridinic N and the spherical porous structure enabling plenty of active sites exposed. This method is prospective for preparation of highly efficient cathodic ORR electrocatalyst.

This work describes an effective method for the preparation of open-cell ceramic foams for their further use as catalyst supports. The polyurethane sponge replica technique was applied using a ceramic suspension based on a mixture of α-alumina, magnesia and titania and polyvinyl alcohol solution as a liquid component. The polyurethane sponge was etched with NaOH and covered with colloidal silica to obtain better adhesion of the slurry to the walls of the polymeric material onto it. The surface area of the ceramic carrier was increased by adding a layer of γ-alumina. Deposition of an active catalytic phase (Pt) was done by impregnation. Properties of the carriers and the final catalyst were investigated by a number of physico-chemical methods such as TEM, SEM, XRD and computer tomography. Hydrogenation of ethyl benzoylformate was performed to elucidate the catalytic properties of foam catalysts illustrating their applicability.

Hierarchical porous carbon (HPC) was prepared using colloidal silica of different sizes as a template, and used as a support for Pt nanoparticles. The Pt dispersion varied with the pore size and structure of the HPC supports. However, the measured Pt dispersions (70%–76%) suggested that this characteristic was not affected by the pore size distribution above a certain size. The activities of the prepared Pt/HPC catalysts for furfural hydrogenation were then investigated. The HPC supports with large pores allowed for greater contact between the Pt nanoparticles and reactants due to the high mass transfer rate, resulting in the highest furfural conversion and 1-pentanol selectivity. In contrast, the HPC supports with small pores exhibited higher furfuryl alcohol selectivities. The effect of the solvent on furfural hydrogenation was also investigated, and it was found that the solubility of H2 in the solvent affected the furfural conversion and product selectivity.

High-specific-surface-area ceramic catalyst carriers with hierarchical pores are conducive to catalytic reactions and filtration processes in the chemical engineering industry. However, conventional processes have difficulty manufacturing porous ceramics with extremely intricate structures. Herein, a novel method was proposed to fabricate alumina ceramic catalyst carriers with a high specific surface area (SSA) and hierarchical porosity by powder bed fusion (PBF) using micromesoporous γ-alumina as a pore-forming powder and an impregnation process of colloidal silica. Hierarchical porosity adjustable on the nm (6.03–32.37 nm), μm (24–30 μm), and mm (0.5~4.4 mm) scales was obtained by adopting and adjusting the PBF, impregnation process on preforms and postsintering process. The impacts of SiO2 content and post sintering temperatures on mechanical properties, pore characteristics, and SSA have been scientifically researched. The PBF-formed alumina ceramics possessed a crush strength of 45.88 ± 3.79 N/cm, high SSA of 56.324 m2/g, and porosity of 72.88 ± 3.37 % with multimodal distributions at 12.24 nm, 32.37 nm, and 24.18 μm. The improvement of SSA was mainly attributed to the use of micromesoporous γ-alumina and an impregnation process to reduce 3D-printing defects to obtain the hierarchical porosity (nm ~ μm scales) and required strength at a lower sintering temperature. Monolithic catalyst carriers with controllable porous structures have been manufactured to facilitate industrial recycling and improve efficiency.

Ceramic shell moulds for investment casting of shrouded low-pressure turbine (LPT) blades were prepared by using colloidal silica binder and partial substitution of the zircon filler with fine alumina. Among the two ceramic slurry systems designed, the first slurry system comprised of polymer-free colloidal silica binder, and the second slurry system comprised of polymer-containing colloidal silica binder. The samples prepared from the first slurry system showed higher fired residual strength and self-load sag values (lesser sag resistance). The casting of shrouded LPT blades was carried out at 1525 °C and 1550 °C using CM247LC superalloy. Ceramic shell moulds prepared from the second slurry system, containing 30 wt% of fine alumina filler, yielded aeronautical grade casting (at 1550 °C) of blades with required dimensional accuracy and average surface roughness. Microstructural analysis of the cut surfaces of self-load sag tested samples was carried out to understand the effect of fine alumina substitution on shell characteristics.

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

In this paper, super-hydrophilic coatings were generated on glass substrates via dipping method using colloidal silica with different morphologies as the main raw materials. The coatings were characterized by transmission electron microscope (TEM), field emission scanning electron microscope (FE-SEM), water contact angle (WCA) analyzer, and atomic force microscope (AFM). The hardness, adhesion, self-cleaning and antifogging properties of the coatings were examined. It has been found that the hydrophilicity of the coating can be significantly improved by using dendritic silica nanoparticles, and the comprehensive performance of the coating is optimum when the branch length of dendritic silica nanoparticles is about 60 nm. The coatings show super-hydrophilicity (CA, 1.7°), and high transmittance (the maximum light transmittance of the coating on glass is increased by 2.2%). Moreover, the coating is very effective in eliminating fog and dirt. The hardness and the adhesion of the coating can be reached 9H and grade 0, respectively, indicating that the coatings have a good mechanical performance, which is essential for its application.

Ru nanoparticles supported on SiO2 microspheres (Ru/SiO2-GUS) were prepared by the glucose-urea-metallic salt method and applied in the decomposition of ammonia. In the glucose-urea-metallic salt method, glucose as the carbon template plays a significant role in the formation of diffusion-beneficial structural properties of Ru/SiO2-GUS, and also induceds the modification of the electronic state of Ru. Ru/SiO2-GUS exhibited higher catalytic activity compared with the catalyst prepared with the impregnation method. The catalytic performance of Ru/SiO2-GUS was further enhanced with the addition of either K or Cs——the addition order and amount strongly affecting the catalytic performance. When the ratio of K/Cs to Ru is 2, the alkali metal (KOH/CsOH) solution is added in the homogeneous solution of glucose, urea, RuCl3 and the colloidal silica, the promotion effect of K/Cs is the strongest, particularly under lower reaction temperatures. However, the promotion effects of K and Cs are different as reveled by the combined results of H2-TPR, XPS and NH3-TPSR. More NH3 can be absorbed on K–Ru/SiO2-GUS and the electron density of Ru decreased. By contrast, more metallic Ru formed on Cs–Ru/SiO2-GUS, facilitating N2 recombination.

The performance of chemical mechanical polishing (CMP) was determined by the morphological characteristics of the abrasive particle. In this study, the shape of the aggregate of fumed silica was confirmed by a method of characterizing the morphology of the particles using transmission electron microscopy (TEM). Each aggregate was classified into four types—linear, branched, ellipsoidal, and spheroidal—and the shape distribution of a fumed-silica slurry was investigated with different specific surface areas. The CMP performance of fumed silica slurries at 90 m2/g with numerous linear-shaped aggregates and 400 m2/g with the highest portion of spheroidal aggregates were compared to that of colloidal silica slurry. A model for the effects of bumpy abrasives on CMP explained the reason for this result by using penetration depth and MRR with various numbers of contact bumps. Furthermore, a mixture of spherical and non-spherical abrasives in a ratio of 4:1 exhibited an improved CMP performance.

A fundamental understanding of the drying behavior of droplets containing solids or solutes is important for various industrial applications. However, droplets are typically highly polydisperse and time-resolved imaging data of the process dynamics are often lacking, which makes it difficult to interpret the effects of different drying parameters. Here, the controlled drying of monodisperse emulsion droplets containing colloidal silica nanoparticles and their subsequent assembly into mesoporous silica microspheres (MSMs) is investigated using an optical microscope outfitted with a heating and vacuum stage. Quantitative imaging results on droplet shrinkage and observed contrast are compared with a theoretical mass-transfer model that is based on the droplet number density, solvent characteristics and temperature. The results presented here provide key insights in the time-resolved formation of MSMs and will enable an optimized direct synthesis of monodisperse MSMs for separation applications and beyond.

The investment casting process was adopted to cast a low-pressure turbine rotor (LPTR) blisk. The casting was carried out in vacuum at 1525 °C by using BZL12Y superalloy. Ceramic shell moulds for the casting were prepared by two different fillers (mullite and zircon), two types of colloidal silica binders (polymer-free binder-A and polymer-containing binder-B) and cobalt aluminate solution. The shell specimens having binder B showed improved green strength and self-load sag resistance in comparison to their counterparts having binder-A. Samples prepared from the slurry compositions having binder-A showed higher residual fired strength than the samples prepared from slurry compositions having binder-B. Defect-free castings of LPTR blisks with fine equiaxed grains were obtained by using ceramic shell moulds containing binder-B and cobalt aluminate solution. The LPTR blisks cast from the ceramic shell moulds having binder-A showed hot tear defect along-with coarse grains. Irrespective of the filler, the LPTR blisk cast by using ceramic shell moulds and cobalt aluminate showed fine grains. The average surface roughness values of LPTR blisks cast from ceramic shell moulds, having binder-B and binder-A, were observed to be in the acceptable range even though castings with binder-A showed marginally lower surface roughness.

Colloidal silica particles have received a widespread interest because of their potential applications in adsorption, ceramics, catalysis, drug delivery and more. Among many approaches towards fabrication of these colloidal particles, Stöber, Fink and Bohn (SFB) method, known as Stöber synthesis is an effective sol-gel strategy for production of uniform, monodispersed silica particles with highly tailorable size and surface properties. This review, after a brief introduction showing the importance of colloidal chemistry, is focused on the Stöber synthesis of silica spheres including discussion of the key factors affecting their particle size, porosity and surface properties. Next, further developments of this method are presented toward fabrication of polymer, carbon, and composite spheres.

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

Polymer insulation is an integral part of electrical equipment. For an electrical insulation system, electrical, mechanical and thermal properties of polymer play a critical role in performance of insulation. Therefore, for reliable insulation system it is imperative to enhance and upgrade the insulating materials properties. In this context nanodielectrics materials can play a crucial role for next generation of insulating materials. Development of nanodielectrics materials with enhanced properties is a complex interplay between filler particle size, its functionalization and uniform dispersion in polymer matrix. In this paper, we report preparation of epoxy nanocomposites with silica particles having varying size and functionality. The epoxy nanocomposite composites were evaluated for their dielectric strength, dielectric dissipation and water absorption and impact properties. Our results shows improvement in dielectric and impact properties for epoxy nanocomposites with functionalized fumed silica nano-particles. Addition of colloidal silica did not show noticeable improvement in dielectric and mechanical properties. Our results for epoxy nanocomposite shows that enhancement of epoxy nanocomposite properties are function of particles size and chemical functionality of filler particles.

Zircon (ZrO2.SiO2) powder filler and colloidal silica binder were used to prepare the ceramic shell moulds for investment casting of shrouded low-pressure turbine blades (LPTB). Ceramic slurries were prepared by using two types of colloidal silica binders (polymer-free binder A and polymer-containing binder B). The samples prepared from binder B showed lesser self-load sag values than those developed from binder A. Ceramic shell moulds made from an optimized slurry composition (having binder A) yielded aeronautical grade casting of blades at 1500 °C with required dimensional accuracy and average surface roughness (Ra). The blades cast from shell moulds (having binder B) showed dimensional accuracy at 1500 °C as well as at 1525 °C. The Ra values of blades cast at 1500 °C and 1525 °C by using shell system with binder B were observed to be higher than those cast from shell system having binder A.

Traditional mobile phone backplane materials are difficult to meet the requirements of the 5G era, and zirconia ceramic is one of the most promising backplane materials. However, its precision machining is difficult due to the hard and brittle nature. In this work, a novel popcorn-like colloidal silica was prepared by the self-assembly growth of nanoparticles for chemical mechanical polishing of the yttria-stabilized tetragonal zirconia ceramic sheets. The surface of the popcorn-like colloidal silica particles has a noticeably uneven shape, and the particle size distribution is uniform. The chemical mechanical polishing results show that the material removal rate of the prepared popcorn-like colloidal silica is increased by about 50% compared with the spherical colloidal silica, and the surface morphology is also obtained improvement. In the process of chemical mechanical polishing, the particles form multi-point contact with the ceramic sheet, resulting in an increase in the coefficient of friction, which is beneficial to the tribochemical reaction. In addition, multi-point contact can distribute the load, make the indentation shallower, and help reduce mechanical scratches. In general, the expected results are expected to provide experimental basis for the optimization of the structure of chemical mechanical polishing abrasive particles.

Hydrogen absorbing materials, such as metal hydrides, present a possible solution for hydrogen storage. During the absorption process these materials swell, which can put the mechanical integrity of its container at risk. One possibility is to increase the flowability of the absorbing material, usually a fine cohesive powder, so that it can rearrange within its container during the swelling stage. In this work, we study if this rearrangement could be improved by the addition of Aerosil, a type of colloidal silica widely used as glidant agent. The walls of a stainless steel reactor are instrumented with strain gauges to measure the accumulation of stresses due to hydrogen absorption-desorption cycles. We explore the container filled with pure LaNi5 absorbing material previously activated, so as with different Aerosil-added proportions. Results show that Aerosil allows avoiding stress build-up, for all glidant concentrations used in present study.

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

In this work, diphasic mullite (3Al2O3·2SiO2) nanofibers with good homogeneity were prepared by electrospinning method. Aluminum nitrate (AN) and aluminum isopropoxide (AIP) were used as alumina sources, commercial colloidal silica as silica source, and polyvinyl alcohol (PVA) as polymer additive. Precursor nanofibers with continuous and uniform structures were acquired at mass ratio of PVA to precursor sol from 0.06 to 0.09. γ-Al2O3 phase was obtained at 878 °C and mullite phase formed at 1322 °C upon heating of the precursor under air atmosphere. Calcined samples suggested mullite as dominant phase at 1300 °C and amorphous SiO2 could even exist at 1400 °C. As-prepared nanofibers possessed continuous structures with subequal average diameters at 900–1200 °C. However, such morphological characteristics were lost at temperatures above 1300 °C due to rapid growth of crystal grains. Al and Si elements were uniformly distributed in fibers and mixed at nanoscale, confirming homogeneity and diphasic features of nanofibers.

Fouling phenomenon is considered among the major reasons that cause significant increase of operating cost of desalination plants equipped with reverse osmosis (RO) membranes. This phenomenon is studied in the present work in the case of RO polyamide aromatic membranes using model seawater containing inorganic salts and colloidal compounds. Different solubility conditions of CaCO3 and CaSO4 were applied to study RO performances with and without colloid presence. During experiments, the membrane permeate fluxes were continuously monitored. Moreover, studies of chemical composition, structure, and morphology of the materials deposited on the membrane surface were conducted using energy dispersive microanalysis (EDS) X-ray diffraction and scanning electronic microscopy (SEM). Results show that in conditions of calcium carbonate oversaturation there is a reduction in the permeate flow of 11.2% due to fouling of the membrane by the precipitation of this compound. While in the same conditions of calcium sulphate oversaturation the reduction of the flow is 5%, so we can conclude that in conditions of oversaturation of both salts, calcium carbonate produces a greater fouling of the membrane that in its view causes greater decrease in the flow of permeate. All this based on the results of the test with both salts in oversaturated conditions. Resulting in the formation of calcite and gypsum crystals onto the membranes as XRD analyses stated. Additional presence of colloidal silica in those conditions intensifies strongly the fouling, leading until to 24.1% of permeate flux decrease.

Shear thickening fluids (STF) have the unique property of increased energy dissipation combined with increased elastic modulus making it ideal for shock absorption applications. The study investigates the effect of particle size and concentration of colloidal silica on the rheological parameters of STF. The particle size of colloidal silica ranged from 100 to 750 nm. Intended for the ballistic performance of STF, the present work also studies the ballistic performance of STF which is a suspension made up of silica of different colloidal particle concentrations in polyethylene glycol (PEG).

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

The rheological behavior of low-calcium fly ash suspensions in activating solutions of colloidal silica and alkali hydroxide is investigated. The study is aimed at relating the rheological behavior of alkali-silicate activated low-calcium fly ash (AAF) suspensions with Portland cement paste suspensions. The yield stress and the viscosity of the AAF suspensions increase with the alkalinity of the colloidal solution, which is due to changes in the surface charges on fly ash particles with the change in the ionic medium. Increasing the alkalinity results in a less negative zeta potential of fly ash in the alkaline solution of colloidal silica and an increase in the yield srtess of the AAF suspension. The thixotropic behavior in AAF suspensions is associated with structure breakdown to a finely dispersed suspension of particles produced by shearing. Energy measurements indicate a very slow change in the internal particle structure with age at room temperature. A comparison of AAF suspensions is presented with suspensions of Portland cement in water, which are proportioned for similar physical flow characteristics and yield stress. AAF suspensions have a larger solid fraction than the cement suspensions in water of comparable yield stress. The zeta potential of cement particles in water is less negative when compared to fly ash in alkaline-silicate solutions. The AAF suspensions of comparable yield stress exhibit a significantly higher viscosity than the cement suspensions in water. Cement paste and AAF suspensions exhibit a rate dependent yield response. Cement paste suspensions exhibit a threshold strain rate for minimum yield stress. In AAF suspensions there is a continuous decrease in the yield stress at lower strain rates. The thixotropic behavior in cement paste is influenced by chemical ageing which produces a rapid recovery of yield stress. In comparison, there is very little ageing at room temperature in the AAF suspensions and a very slow recovery of yield stress after shearing.

Cost-effective porous alumina-mullite ceramic membrane supports were prepared from mixtures of different alumina/silica (Al2O3/SiO2) ratios of coarse α-alumina micro-powder and colloidal silica (CS). The effects of sintering temperature, Al2O3/SiO2 ratio and cornstarch content on the crystalline phase evolution, microstructures, porosity, bending strength, pore size distribution and permeance of the ceramic membrane supports were systematically investigated. The results showed that the increase in sintering temperature was beneficial to the mullite formation and the bending strength. However, it was adverse to the improvement of porosity and the pore size distribution which have positive correlation with the permeance of the supports. The increases in Al2O3/SiO2 ratio and cornstarch were favourable to the mullite formation, improvement of porosity, pore size distribution and morphology of the supports, but were unfavourable to the bending strength. A high-performance porous alumina-mullite ceramic support with suitable porosity (50.5%) and pore size (3.1 μm), sufficient mechanical strength (49.7 MPa) and high permeances was successfully synthesized by optimizing the sintering temperature, Al2O3/SiO2 ratio and cornstarch content. Moreover, the proposed simple method shows much potential for the preparation of high-performance porous alumina-mullite ceramic membrane supports.

Summary Lithium-oxygen (Li-O2) batteries are promising next-generation batteries owing to their ultrahigh theoretical energy density. However, Li metal anodes in Li-O2 batteries are still plagued by uncontrollable dendrite growth and serious parasitic reactions. Herein, we report an electrolyte regulation strategy via in situ coupling of CF3SO3− and hydrophobic silica colloidal nanoparticle through electrostatic interaction. With the assistance of the seed crystal effect and the solid-like rheological properties, 10 wt % hydrophobic silica colloid electrolyte (HSCE) enables the dendrite-free morphology of Li deposition and helps form a stable solid-electrolyte interface, which can reduce the impedance by about 45-fold after long-term cycling. Moreover, 10 wt % HSCE with a lower diffusion coefficient can achieve a 980-fold better anticorrosion effect than 0 wt % HSCE. Consequently, the 10 wt % HSCE batteries exhibit a stable plating/stripping process (30 mV in overpotential up to 700 h) and a good anodic cycle life in Li-O2 batteries (550 cycles).

Transparent hybrid coatings were prepared from methyltrimethoxysilane (MTMS) and colloidal silica nanoparticles (SiO2) by a sol-gel process. Influences of colloidal silica content and aging time on the surface morphology, surface composition, and the properties such as transparency, water contact angles (WCA), and pencil hardness, of the hybrid coatings were systematically investigated. Coatings with WCA as high as 110–120° and pencil hardness of 4–5 H could be achieved at appropriate colloidal silica content and aging time. The dust removal performance of the hybrid coatings was examined by vertical tilting of the dust-deposited coatings using volcanic ash as the standard dust. When the WCA was over about 100°, the hybrid coatings exhibited excellent dust removal performance under gravity, regardless of the quantity of the dust deposited. Oxygen plasma etching experiments and the dust removal tests in dry chamber indicated that the nanometer-scale surface roughness could endow the hybrid coatings with the good dust removal performance. The hydrophobic methyl groups can further enhance the dust removal performance. The hybrid coating with MTMS/SiO2 mass ratio of 1.3:1 was cast on the coverslips of the solar cell for Mars, and undergone two durability series tests, i.e. thermal shock/humidity series (THS) test and high-low temperature cycle/electron beam radiation/vacuum ultraviolet radiation series (HEVS) test. The anti-dust coverslips showed good durability in HEVS tests and dust removal percentage of 75.8% after HEVS test, implying its good service life on Mars.

Magnesia gunning materials are widely used in the steel making process due to their high refractoriness and excellent corrosion resistance to alkaline slag. However, hydration of magnesia is still a key issue that needs to be settled in magnesia gunning materials. The citric acid can significantly inhibit hydration rate of magnesia in aqueous suspensions. In this paper, the performance of different citric acid contents on magnesia suspensions was evaluated by zeta potential and conductivity measurements, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. And physical properties of magnesia gunning materials containing different citric acid contents were also obtained. The results showed that the citric acid, in the magnesia suspension, led to the formation of a complex structure layer, which was made of MgOH+ and Cit(n−) (n = 3, 2 or 1), thereby inhibiting the dissolution process of magnesia. However, this was only effective at low levels. When the content of citric acid in the suspensions was increased to 3 wt %, the magnesia still underwent significant dissolution due to a decrease in the formation of the [nMgOH+·Cit(n−)] (n = 3, 2 or 1) complexes. Moreover, the FTIR spectra suggested that the [nMgOH+·Cit(n−)] (n = 3, 2 or 1) complexes was unidentate coordination. In magnesia gunning materials, although the protective layer decomposed at about 500 °C, the decrease in sample strength was less than that caused by magnesia hydration. The optimal amount of citric acid in the magnesia gunning materials was 0.18 wt %.

Geometry greatly affects performances in adsorption and catalytic reactions. Since the crystal structure of zeolite collapses at high temperature, it is difficult to synthesize hollow fibers from only zeolite by sintering. In this study, we synthesized zeolite hollow fibers using colloidal silica, which has excellent heat and chemical resistance, as an inorganic binder. The zeolite hollow fiber precursor was immersed in a colloidal silica aqueous solution and calcined at 600 °C. Additional silica coating significantly improves the mechanical robustness by increasing the fracture load by up to 200%, while the zeolite content, specific surface area/pore volume reduced slightly. These results show that colloidal silica functions as an effective inorganic binder without blocking the pores of the zeolite. The cadmium adsorption showed that for a 100-ppm Cd2+ solution, the breakthrough time at C/C0 = 0.05 was effectively extended by 20% (112 min) and 65% (153 min) for conventional hollow fiber and 3-channel designs, respectively, compared to the powder counterpart (93 min).

Silver nanoparticles exhibit beneficial bactericidal and fungicidal properties that make them an object of interest for pharmaceutical, cosmetics and agricultural industries. However, commonly used methods for obtaining nanosilver particles use synthetic polymers and toxic compounds that are harmful to the environment. Currently for the nanoparticles synthesis, natural reagents and inter substances such as plant extracts and silica are often applied. This work describes two approaches for silver nanoparticles on colloidal silica carrier preparation by chemical reduction using NaBH4 as a reductor and Rhodiola rosea extract as a stabilizing-reducing agent. Extract properties were determined by total phenolic compounds content by Folin–Ciocalteau reaction and total antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl reagent. The impact of various parameters on synthesis efficiency such as: time, temperature, silver and stabilizer concentrations as well as the amount of colloidal silica has been investigated. Physicochemical characteristics of selected nanosilver suspension was specified by instrumental methods such as: scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and dynamic light scattering (DLS). Moreover, stability of obtained products was monitored and described using UV–Vis spectrophotometry. Refereed/Peer-reviewed

The development of a variety of methodologies has been studied in order to obtain good dispersed nanoparticles in the medium without seriously affecting the magnetic and rheological properties of them. One of the areas of application that needs a material with controlled particle size and good stability is that of biomedical. In those applications are required to avoid the precipitation for promoting the biocompatibility and for obtaining a homogeneous nanoparticle size. In this paper Magnetite nanoparticles were synthesized by the Fast Injection Co-precipitation method. The magnetic nanoparticles were dispersed modifying their surface and, in this way, decreasing the agglomerate sizes and on the other hand favor the stability of the suspension. The surface modification was carried out by means of different coatings such as: sodium citrate, sodium metasilicate and colloidal silica from Tetraethyl Orthosilicate, obtained using the acid sol-gel process. The nanoparticles obtained were characterized by X-ray Diffraction, Vibrating Sample Magnetometer, Dynamic Light Scattering, Transmission Electron Microscope, Zeta Potential and Infrared Spectroscopy. An agglomerate size of nanoparticles around 100 and 200 nm was obtained, with good superparamagnetic properties. Also, by zeta potential measurements was found that the functional groups added by sodium metasilicate and tetraethyl orthosilicate generate repulsion among the superparamagnetic iron oxide nanoparticles increasing their zeta potential and stability of the suspensions. The main conclusion from this research is the establishment of a simple and very fast route to obtain stable and dispersed superparamagnetic nanoparticles with high stability at pH 7.4 that can be used in medical applications. This was achieved considering the difference in the isoelectric point, IEP, and of course in the net charge of both silica polymer and magnetite.

Pickering emulsions are currently receiving increased attention as a promising alternative to dispersions or surfactant stabilized emulsions in two-phase biocatalysis. In order to design a continuous membrane reactor using water-in-oil Pickering emulsions for biocatalysis, knowledge on the filterability of the Pickering emulsion is required. This can be influenced by a number of factors, e.g. type and size of stabilizing nanoparticles, applied solvent, and used membrane. In a previous application of water-in-oil Pickering emulsions for continuous biocatalysis in a membrane reactor, spherical silica particles were used to stabilize the emulsion. This resulted in densely packed filter cakes due to unbound residual particles and decreasing flux over time. Furthermore, rather large droplet sizes with small specific interfacial areas were achieved. In this work, the use of colloidal silica nanoparticle for the stabilization of bioactive Pickering emulsions was studied. The filterability of bioactive water-in-oil Pickering emulsions stabilized by spherical or colloidal silica nanoparticles was compared. Using colloidal silica nanoparticles was found to result in smaller emulsion drop sizes, higher filterability and better reproducibility of drop size distribution and flux. An increase in water volume fraction decreased the flux level, but filtration was still possible at industrially relevant fluxes. With the selected nanoparticles, continuous biocatalysis in a membrane reactor at constant flux, i.e. constant residence time, was performed twice for 30 h. Substrate and product concentrations were constant and reproducible and the enzyme was still active after 30 h. The productivity was higher than that obtained with spherical silica nanoparticles and the process duration is the longest so far reported for continuous biocatalysis in PE at industrially relevant residence times.

The novel ZSM-5 zeolite was successfully prepared by the colloidal pretreatment method and using rice husk ash (RHA) and pseudo-boehmite as raw materials of silicon and aluminum. A series of samples (ZSM-5-X) with various colloidal silica usage quantity were characterized by XRD, FTIR, SEM and nitrogen adsorption–desorption methods, and the results indicated that the method can reduce the formation of impurity crystals and increase the micropore volume. The CO 2 adsorption measurement showed that the maximum adsorption amount of the samples was 55.01 cm 3 /g (ZSM-5-25) at 0 °C and 23.08 cm 3 /g (ZSM-5-75) at 90 °C. The Langmuir, Freundlich and Sips isotherm models were used to fit gas adsorption experimental data and analyze adsorption mechanisms. The three-parameter Sips model with a heterogeneous coefficient was suitable for simulating CO 2 adsorption, and the correlation coefficient of the Langmuir model was close to 1 for fitting N 2 and O 2 adsorption. Higher CO 2 /N 2 and CO 2 /O 2 adsorption selectivity and stable adsorption–desorption regeneration performance have been demonstrated, and it indicated that the adsorbent had a promising application in the adsorption separation of CO 2 from industrial flue gas.

Cobalt nanoparticles supported on a well-defined porous structure are a promising catalyst for the Fischer-Tropsch synthesis (FTS). The catalytic efficiency of the porous catalyst depends on the properties of the support and on the properties of the active component. Methods such as wet-chemistry and flame synthesis are often limited by their variability in terms of support structure and size of the integrated active metal components. In this work, well-organised porous structures were produced using spray-drying of colloidal silica suspensions containing dissolved cobalt nitrate. This technique allows to synthesize catalyst particles with tunable specific surface area, pore size, cobalt particle size, and cobalt loading. The dried silica particles show interconnected pores, which makes it especially suitable for use as a catalyst support. Moreover, it is shown that the pore sizes and active metal particle sizes can be varied independently. In addition, the mass of cobalt oxide per silica support surface was identified as a controlling parameter for the metal oxide nanoparticle size for a given calcination temperature.

In this study, the mordenite (MOR) zeolite is synthesized using a seed-assisted and template-free method and tested for glucose dehydration to 5-hydroxymethylfurfural (5-HMF). The synthesized zeolites are characterized by using X-Ray diffraction (XRD), N2-sorption, Field Emission Scanning Electron Microscopy (FESEM), Pyridine-FTIR, 27Al NMR and Thermogravimetric analysis. The mesoporosity has been introduced in the zeolite by the aging and/or with higher SiO2/Al2O3 ratio. Colloidal silica (CS) as a precursor in combination with aging resulted in a unidirectional growth of the crystals, as evidenced by FESEM images and XRD. The MOR synthesized with CS as silica precursor under 12 h aging showed the best activity giving a 5-HMF yield of 66% (selectivity 87%) with a glucose conversion of 76% at 180 °C for 1 h. Mesoporosity and the optimum number of Lewis and Bronsted acid sites of the MOR played a key role in obtaining the best activity.

Dual hardening steels combine precipitation of both secondary hardening carbides and intermetallic phases in a martensitic matrix. Due to this combination, the carbon content necessary to achieve high hardness levels can be reduced, resulting in a decreased amount of large and embrittling carbides. In this study, the influence of different heat treatments on microstructure evolution and secondary hardness is investigated. Different metallographic preparation methods were tested in order to visualize the microstructure. Carbides were characterized using spot-pattern electron backscatter diffraction. For light optical investigations, preparation with V2A-pickle lead to the best results. Preparation with colloidal silica suspension achieved the best results for investigations by scanning electron microscopy and for carbide characterization using electron backscatter diffraction. It was found that a homogenization treatment prior to austenitization was unable to increase the amount of dissolved carbides, and thus had no effect on secondary hardness. By increasing the austenitization temperature, the amount of carbides and secondary hardness could be increased significantly.

Tungsten heavy alloys (WHA) have been widely adopted in many engineering applications due to their excellent physicochemical properties. Microstructure characterization is a very powerful method ranging from testing materials properties to detecting material failures and defects. However, the microstructure of WHA was not well characterized with the sample prepared by conventional method of etching with strong acids, bases or oxidant after polishing for the coarse surface. To solve the problem, the exact characterization of W-Ni-Fe heavy alloys microstructure was conducted using the sample prepared by optimized polishing method. A series of experiments were conducted to find the suitable polishing conditions including polishing pad, abrasive slurry and slurry pH. The results show that a smooth and clear microstructure sample was obtained by polishing with alkaline colloidal silica and IC polishing pad, which contained few defects compared with that obtained by conventional method of etching after polishing. The microstructure of W-Ni-Fe heavy alloys was analyzed by XRD, EDS tests and EPMA detection. The slipping phenomenon was observed in nanoindentation test using the prepared sample for the first time and the mechanism of satisfactory microstructure sample preparation was illustrated.

Influence of colloidal silica sol (SS) consisting of mono-dispersed nano-silica on properties and microstructure of the hardened cement-based materials was investigated as compared to the nano-silica (NS) powder with agglomerates in micron-scale through detecting the mechanical and durable properties of the hardened mortar and by using SEM observation, nano-indentation test and MIP analysis. The results showed that the strength enhancement of the mortar with SS addition revealed an overall more improvement but a higher discreteness than that with NS addition. After the calcium leaching test, it was found that the strength of the mortar with SS addition showed a clearly higher loss than that with NS addition, though the neutralization depth revealed a more reduction while incorporating SS and the residue strength still tends to increase with increasing the nano-silica addition. All these observations are resulted from the fact that the nano-particles in SS coagulate immediately once cement is mixed into water containing SS, forming loose flocs with a more open microstructure and a higher free water retention capacity than the agglomerates in NS, thus leading to a lower free water cement ratio in fresh cement paste and an overall more compact microstructure in hardened cement paste while incorporating SS. However, pozzolanic C-S-H gels from the gelled nanosilica can be observed to show a loose compaction, with nanopores and even micropores inside and also an abnormal growth of the larger CH crystals in the pozzolanic C-S-H gels but without nucleated growth of the C-S-H gels from cement hydration. The dissolution of the larger CH crystals in the coagulated gel network in the paste may leave large pores in the hardened cement mortar to cause a higher strength loss after the calcium leaching test. The MIP testing results indicated that the threshold pore size showed few differences for the HCP with and without 1.0% nano-silica addition, illustrating the permeability of the hardened cement paste may have nothing to do with the threshold pore size, but the total porosity and the micropores in the range of 100–10000 nm.

Chemical mechanical polishing has shown great prospect in a wide range of microelectronics applications due to the global planarization. For the first time, we proposed a novel branched inorganic polyelectrolyte as an effective binder to modify colloidal silica. The composite abrasives combine the advantages of both colloidal silica and polyelectrolyte, exhibiting good dispersibility, stability in water and outstanding polishing property. The results indicated that the composite abrasive could enhance the material removal rate (MRR) of sapphire wafer up to 23.76%. The optimum removal rate by composite abrasive also yielded a superior surface roughness (Ra) of 1.445 nm. The mechanism between the composite abrasives and sapphire in chemical mechanical polishing process was investigated in detail. X-ray photoelectron spectroscopy test demonstrated that a soft layer was formed on the surface of sapphire. Micro-contact model revealed that the inorganic polyelectrolyte adhered to the surface of colloidal silica could reduce the repulsion between particles and sapphire, thereby accelerating chemical-mechanical reaction rate and achieving rapid surface removal of the sapphire surface.

Here we report an economical synthesis method for high-silica (Si/Al∼17) LTA zeolites using colloidal silica and ammonium fluoride as Si and F sources, respectively. When both 1,2-dimethyl-3-(4-methylbenzyl)imidazolium and tetramethylammonium ions are used as organic structure-directing agents, the LTA crystallization was found to strongly depend on the particle size of the colloidal silica employed. However, the type of Al and F sources had little effect on the formation of this small-pore zeolite. The catalytic properties of three high-silica Cu-LTA catalysts synthesized using the same Si source (Ludox HS-40 colloidal silica) but different Al sources (aluminum hydroxide, aluminum metal, and pseudoboehmite) for the selective catalytic reduction of NOx with NH3 (NH3-SCR) are also presented. Despite the presence of a large amount of extraframework Al, all of the catalysts exhibited considerably higher activity maintenance than the current commercial Cu-SSZ-13 catalyst even after hydrothermal aging at 900 °C.

Colloidal silica has wide applications and the global demand of specialty silica is continually increasing. Therefore, it is significant to develop a synthetic method that is simple, versatile, energy-saving, ecologically benign, and easily scalable. Biomimetic synthesis of colloidal silica represents a promising strategy; however, it often requires the synthesis or extraction of specialized macromolecules. In this paper, we present a novel aqueous, one-pot, and green route for synthesis of organosilica nanoparticles. The reaction systems contain only water, an organosilane precursor, a salt, and a commonly used surfactant or amphiphilic polymer. The reaction was performed at ambient conditions without adding any additional solvent, energy, and harsh chemicals. The key findings include the novel identification of 5 salts (i.e. nitrite, fluoride, dibasic phosphate, acetate, and sulfite) that can catalyze organosilica condensation and the resulting formation of nano-colloids. Moreover, the presence of amphiphilic molecules is essential for salt catalysis at low salt concentrations and at nearly neutral pH. Solid-state NMR and in-situ ATR-FTIR studies confirmed that organosilica condensation is highly efficient under the mild reaction condition. In conclusion, the present study demonstrates that "soft" interaction between salts and surfactants (or polymers) can be utilized to construct an effective platform for synthesis of "hard" organosilica particles. The proposed method is generic and applicable to a wide range of commonly used surfactants (viz. non-ionic, anionic, cationic) and amphiphilic polymers, as well as to organosilanes with various hydrophobic functional groups (e.g. mercaptopropyl, vinyl, and methyl).

Saturation mechanisms are the cause considerable strength reduction and swelling enhancement in clayey soils. To overcome this phenomenon, stabilization of the weak layers could be useful when any chemical additives which are calcium based are added. In the presence of considerable amounts of sulfate ions, the conventional additive like lime leads to large heaving due to swelling. This paper presents the changes in the amount of California Bearing Ratio (CBR) of soaked samples and swelling index of Najmabad clayey soil after being stabilized with Colloidal Silica (CS). These tests were performed at different curing times of 3, 7, and 28 days. Moreover, CBR tests were performed after Freeze-Thaw (F-T) conditions under 1, 2, 4, 8, and 12 cycles in 3 selected samples which satisfied the required degree of improvement. In addition, free swelling in all the states was measured and controlled. The results revealed fulfilling CBR criterion of samples subjected to F-T cycles and significant reduction of swelling percent in samples with 1% Nano Silica (NS) particles after 28 days curing time and 2% NS particles after 7 days curing time. Also, Scanning Electron Microscopy (SEM) revealed structural changes and an integrated network for soil improved with CS.

Amorphous systems prepared with different strategies, such as solid dispersion with colloidal particles or soluble polymers and inclusion complex, have been used for improving solubility and dissolution of poorly water soluble drugs. The purpose of this study was to obtain a deeper understanding of the impact of three different amorphous systems prepared by spray drying with silica, polyvinylpyrrolidone (PVP) or 2-hydroxypropyl-β-cyclodextrin (HPβCD) using indomethacin (IND) as a model drug. IND was spray dried with silica, PVP or HPβCD at different mass ratios, and the obtained powders were characterized with respect to colloidal silica particle redispersion, morphology, thermal properties, solid state properties and physical stability. The solubility and intrinsic dissolution rate of IND in the different powders were assessed. It was found that all the three amorphization strategies resulted in amorphous IND product. PVP showed the best stabilizing effect on amorphous IND for at least four months while silica was the worst for no more than 18 days. The solubility of IND decreased with the decrease of HPβCD or PVP ratio in the amorphous products. Samples with HPβCD showed the highest improvement in the dissolution rate at low drug loading, i.e. 15% while samples with PVP resulted in the highest improvement of dissolution rate at high drug loading, i.e. 70%. We conclude that amorphization with PVP was the best strategy for amorphous IND stabilization among all the amorphous products investigated in this project and improved IND dissolution mostly at high drug loadings. HPβCD improved IND dissolution mostly at low drug loadings. Effect of solid dispersion with silica nanoparticles on the dissolution behavior was always the least significant among the three investigated amorphization strategies.

Novel nano-composite emulsions consisting of colloidal silica particles covered with thin polyacrylate coat (PreEm) were successfully prepared with the aid of a nonionic surfactant having a low cloud point (Tcp = 40 °C). This nonionic surfactant first deposited on the surface of colloidal silica particles above its Tcp to provide the sites for adsorption and the following polymerization of acrylic monomer. Scanning transmission electron microscopy of the colloidal particles obtained after the polymerization indicated the presence of very thin coat layer of polyacrylate (c.a., 1–3 nm nm in thickness) around silica nanoparticles. These PreEm particles were readily incorporated into the ordinary acrylic emulsions (AcEm) to obtain silica/ polyacrylate mixed emulsions (PreEm/ AcEm). It was revealed that the mixed emulsions can give transparent coating films at a silica/polyacrylate ratio below 150/100 in which the colloidal particles were distributed in the polymer matrix without aggregation. This morphology was in sharp contrast with the particle aggregation morphologies shown by the films obtained from the naked colloidal silica-AcEm mixed emulsion and the conventional nanocomposite emulsion consisting of silica particles covered with thick polyacrylate coat. The PreEm/ AcEm films exhibited increased hardness with increasing the silica contents to 150%. These data supported the effectiveness of PreEm in controlling the properties of silica-polyacrylate hybrid films.

This paper proposes an integrated concrete surface treatment with surface enhancement via silicate impregnation and surface spraying with TiO2 (a photocatalyst). In this work, two types of silicate-based materials, sodium alumina silicate (SAS) and colloidal silica (COS) were used. Various tests were carried out to characterize the silicate properties and engineering performance of the impregnated concrete. In addition, the purification performance in concrete sprayed with TiO2 was investigated. Concrete impregnated with silicate and sprayed with TiO2 showed an improvement in the durability and mechanical performance because of the addition of the CSH gel and TiO2 barrier. After impregnation, the TiO2 applied by spraying retained good performance for the removal of acetaldehyde and methyl orange.

A sol-gel coating using colloidal silica on a glass surface is carried out towards improving the self-cleaning properties. The optical transmittance and hydrophobic characteristics of the resulting coating are analyzed using analytical tools. Since the sol-gel coating reduces the optical transmittance of the glass samples, due to scattering and diffusion of the incident optical radiation at the coating surface, silicon oil (Sigma-Aldrich, 10 cSt) impregnation method is introduced to improve the optical transmittance. Silicon oil has good heat transfer characteristics, stable properties over range of temperatures, and optically transparent characteristics with refractive index of 1.4034. The resulting coated surface is tested in outdoor environments to examine the dust effect on the optical transmittance of the sol-gel coated and oil impregnated glass samples. It is found that deposition of 75 nm size silica particles on the glass surface modifies the texture height of the sol-gel coating, which in turn, improves the surface hydrophobicity. Sol-gel coating results in a web-type fully connected porous structures; in which case, agglomeration of the synthesized particles is responsible for the fully connected porous texture at the coating surface. The optical transmittance remains low for the sol-gel coated glass samples because of scattering and diffusion of the incident optical radiation at the coating surface. Silicon oil impregnation improves the optical transmittance of the sol-gel coated samples. The dust particles immerse into the oil film and reduce the optical transmittance of the oil impregnated samples in outdoor environments.

We investigated the effects of polymer addition on crack formation in particulate films of colloidal silica. Two types of polyvinyl alcohol (PVA) with different degrees of saponification were compared. Partially saponified PVA (PVA-1) suppressed crack formation. In contrast, weaker suppression was observed when we used fully saponified PVA (PVA-2). Centrifugation experiments of colloid–polymer suspensions revealed that PVA-1 adsorbed on particles well whereas PVA-2 was not adsorbed effectively, suggesting that the polymer–particle interactions strongly depended on the content of polymer functional groups. In addition, we observed segregation of PVA-2 between packed particles, which contributed to a sparse packing structure. We did not observe such segregation of PVA-1 and particles were packed more tightly than for PVA-2. These results clearly showed that the affinity between polymer molecules and suspended particles affected both crack formation and packing structures. We also found that adsorption of polymer molecules did not necessarily suppress crack formation. When we added polyvinyl pyrrolidone (PVP) to silica suspensions, we observed much more cracks than in the sample without polymer even though PVP molecules adsorbed on the silica particles. We conclude that adsorption of polymer molecules on suspended particles is preferable, but does not necessarily suppress crack formation. Miscibility between polymer molecules and particles would be a key issue in crack formation and packing structure of colloid-polymer films.

We show that seven different types of commercial, biocide-free, colloidal silica products with mean particle sizes between 17 and 88 nm with 3 different surface chemistries (Na-stabilized, aluminized and silane-modified) are not toxic to the bacterium Pseudomonas putida, and the algae Raphidocelis subcapitata in the concentration range 5–500 mg/L. They are also not acutely toxic to Daphnia magna at concentrations up to 10,000 mg/L. Six silica particles are toxic to the gill cell line RTgill-W1 from Rainbow trout (Oncorhynchus mykiss), showing a clear concentration-response relationship with EC50 values between 13 and 92 mg/L. Toxicity in the fish cells decreases with increasing hydrodynamic size and is dependent on particle surface area. The average EC50 across the tested particles is 2.1 (±0.3) m2/L. Surface modifications clearly impact toxicity, with silane-modified particles showing no cytotoxicity. The reduced number of free silanol groups on the surface of the silane modified particle, in combination with an increased steric hindrance that prevents contact with the cells is a possible mechanism for the observed lack of toxicity. This is also in line with previous studies on silica nanoparticles in human toxicology. Overall, these findings show a generally low ecotoxicity of silica nanoparticles and indicate that silica particles of different sizes but identical surface chemistry could potentially be grouped into an assessment group under regulation such as REACH.

In this work, we present a comparative study on the non-isothermal crystallization kinetics for electrospun 3AB2S nanofibers prepared using colloidal silica (CS) and tetraethyl orthosilicate (TEOS) as silica sources. As-spun nanofibers with subequal mean diameters were obtained. Compared with those synthesized through CS, 3AB2S nanofibers prepared using TEOS have higher element homogeneity as a result of the simultaneous hydrolysis of Al and Si. They also show lower crystallinity, smaller mean grain size, higher crystallization temperature and higher activation energy owing to the stronger hindrance effect of uniformly distributed amorphous SiO2 on the reaction between Al2O3 and B2O3. Avrami constants values for Al4B2O9 crystallization together with TEM observations reveal an interface-controlled growth mechanism with instantaneous nucleation for both silica sources. However, those results indicate a two-dimensional grain growth when CS was used and a three-dimensional grain growth in the case of TEOS.

Semiconductor chip manufacturers use slurries of metal oxide nanoparticles (NPs) as abrasives in chemical mechanical planarization (CMP) processes on wafers containing films of III/V semiconducting materials. Assessing the toxicity of these specialized NPs is challenging not only because commercial slurries may contain undefined toxic constituents, but because CMP processes can change the physical and chemical properties of the NPs. Herein, the fresh water flea Daphnia magna (D. magna) was used to assess the effects of Ultra-Sol® 200S CMP slurry containing ~30-nm colloidal silica (c-SiO2) NPs before (pristine) and after (spent) a GaAs wafer was polished with an extreme arm-pressure of 5 psi. In the acute 96-hour toxicity assessments, both the pristine and spent slurries at 4.0 mg/mL c-SiO2 NPs had little effect on D. magna morbidity and body sizes. In the chronic 21-day toxicity assessments, neither slurry at 0.10 mg/mL c-SiO2 NPs was toxic, but both slurries lead to a modest (9–10%) increase in D. magna body sizes and a significant (~2-fold) increase in reproductive output, indicative of a positive hormetic response. Identical increases in D. magna body sizes and reproductive output were observed with a supernatant of the pristine slurry, in the absence of the c-SiO2 NPs, indicating that soluble material in the pristine supernatant contributed to the hormetic response, which suggests that the soluble material may also contribute to the hormetic response of the spent material.

Zeolite Beta has been widely utilized on large molecular systems because of its three dimensional large micropores, 12-membered ring. Controlling amount of acid and its strength of zeolites depending on the composition is very crucial to improve their catalytic performance. Incorporation of heteroatoms into the framework of zeolites is one of the effective ways to control catalytic activities. However, it is difficult to synthesize high-silica zeolite Beta with heteroatoms, which has been limiting the functions of zeolite Beta. To overcome the problem, we developed a dry gel conversion method using dealuminated zeolites; we can synthesize *BEA type ferrisilicate (Fe-Beta). In this method, it is necessary to use two silica sources; dealminated Beta and colloidal silica. The dissolving process of these silica sources by NaOH plays a significant role in the crystallization to Fe-Beta. The Fe-Beta shows higher selectivity to isobutene on acetone-to-olefins (ATO) reaction compared to Al-Beta and Fe-MFI. This is due to the acid strength weakened by substituting Al by Fe and the large diffusivity of isobutene in the large micropores of *BEA structure.