Nanosilica Sol Research Articles

Flame retardancy improvement of modified cotton fabric by nano silica sol coating

Cotton fabric was coated by silica sol at different times using dip-coating method. Nano silica coated fabrics were characterized by XRD, FTIR, SEM, EDX, TGA. From SEM result, it showed that fabric surface was coated by nanosilica particles of 20-30 nm size. Nano silica coated fabrics showed the improvement not only flame retardancy (LOI increased from 18.4 to 30.8) but also the tear strength. Tear strength increased from 23 N/mm (cotton fabric) to 29.9 N/mm (fabric coated nanosilica at 3 times).

Гидротермальный нанокремнезем в сельскохозяйственном растениеводстве и биотехнологии

Experiments on application of hydrothermal nanosilica to increase productivity agricultural plants were carried out. Nanosilica sol was produced by ultrafiltration membrane concentration of orthosilicic acid polymers of hydrothermal solution to SiO2 content 10–20 mas. %. Plants treatment was done by diluted sol with SiO2 content in the range 0.0001–0.2 mas. %. Treatment of seeds ore upground parts of plants once ore twice was applied. SiO2 consumption was about 10–20 g per hectare. Experiments with wide range of plants was done, including potatoes, cabbage, vegetable marrow, onion, mustard, amaranth, tomato, sugar, wheat, beet and radish. Besides productivity biochemical and biometric parameters were changed: plants height, quantity, length, wide of leafs and others. For example, in upground mass of amaranth was detected decreasing of cellular tissue content and increasing grease, total saccharin content with constant content of carotene and protein. In amaranth seeds increasing of oil, squalene, starch, protein, vitamin C content was detected.

An investigation on the influence of nano silica morphology on the characteristics of cement composites

Nanosilica is produced with various methods and each product has particular applications in the industry. The differences between the nanosilicas are mainly attributed to their morphology. For instance, some types of nanosilicas such as nanosilica gels have large agglomerates, while some others like nanosilica sols may be produced in the monodispersed form. The main objective of this article is investigating the differences between the influences of agglomeration state of nanosilica, as an aspect of morphology, on the characteristics of cement composites. Among the nanosilica types, nanosilica gel has been scarcely investigated in the cement based materials researches. Thus, a simple method for production of nanosilica gel is presented. Then, the characteristics of cement mixtures containing this material have been compared with those incorporating a monodispersed nanosilica sol and silica fume. The properties investigated in this study include shrinkage measurements, compressive strength, water sorptivity, cement hydration, flow ability, setting times and rapid chloride migration coefficient. The results indicate that, despite the agglomeration state, at early ages, nanosilica gel outperformed the silica sol and silica fume in improving the characteristics such as compressive strength. It confirms that the monodispersed form of nanosilica sol could not provide higher levels of nucleation centers in the mixture; in other words, coagulation of nano particles is inevitable in the environment of cement-based materials. Likewise, at long term, nanosilica gel incorporated concretes had improved durability in terms of chloride penetration and water sorptivity compared to those with monodispersed nanosilica sol.

Gelation process of nanosilica sol and its mechanism: Molecular dynamics simulation

The spontaneous gelation tendency of nanosilica sol (NSS) greatly affects its application as a raw material in chemical production. Therefore, disclosing the gelation process and mechanism of NSS plays a vital role in effectively regulating the gelation process. Herein, we bring deep insight into the gelation process of NSS which mainly includes four stages: Short silicon oxide chains (Si–O chains) are formed on the surface of nanosilica particles. Si–O chains gradually grow into the solution. Si–O chains are intertwined and connected to the surface of the nanosilica particles. The 3D network gel structure is formed by using Si–O chains as a skeleton. The effect of silanol ionization on the gelation process and its mechanism was further explored. According to our results, appropriately increasing the ionization degree of silanol groups on silica surface or decreasing the ionization degree of silicic acids will greatly decrease the gelation process of NSS.

Nanoindentation of cement stone samples

The preliminary results of the studied cement samples were obtained by the nanoindentation method. It was revealed that the elastic modulus M increases in samples that contain a complex additive containing nanosized particles. The effect is also observed with the introduction of an additive containing only one type of nanoparticles (nanosilica sol SiO2 or carbon nanomaterial MCNT). The selection of the parameters of the nanoindentation method, which ensured the obtaining of the final consistent results, was performed. These results are presented by histograms of the distribution of nanoindentation points in modulus of elasticity M and hardness H and distributions in M and H in the horizontal XY plane perpendicular to the motion of the nanoindentor. The results obtained indicate that there is a change in the nanostructure of the C – S – H gel, which is compared with an increase in strength, Young’s moduli and shear, upon the introduction of SiO2 nanoparticles and MCNT nanoparticles.

The influence of nano-silica sol on the performance of iron chromium black for the building energy-saving coating

The influence of nano-silica sol on the performance of iron chromium black for the building energy-saving coating

High‐Strength, Rapidly Self‐Recoverable, and Antifatigue Nano‐SiO2/Poly(Acrylamide–Lauryl Methacrylate) Composite Hydrogels

AbstractCreating load‐bearing hydrogels with superior mechanical strength and toughness is of vital importance for promoting the development of polymer hydrogels toward practical applications. Herein, a type of composite hydrogel is facilely fabricated employing simple and effective UV irradiation one‐pot method by introducing cheap and available nanosilica sol into hydrophobic association poly(acrylamide–lauryl methacrylate) (HAPAM gels). Composite hydrogels exhibit enhanced mechanical strength (compression stress reaching 4.4 MPa) and toughness (compression hysteresis energy achieved is 151.15 kJ m−3) compared to HAPAM gels. Composite hydrogels also demonstrate rapid self‐recovery behavior (95.91% stress recovery and 92.19% hysteresis energy recovery after restoration for 15 min, respectively) and favorable fatigue‐resistant ability without the help of external stimuli at room temperature based on the cyclic loading–unloading compression measurements. The simple and effective design strategy may help the development of hydrogel materials toward practical applications for soft sensors, tissue engineering, and actuators.

Behavior of Colloidal Nanosilica in an Ultrahigh Performance Concrete Environment Using Dynamic Light Scattering.

The dispersion quality of nanosilica (NS) is an essential parameter to influence and control the material characteristics of nanosilica-enhanced concrete. In this research, the dispersion quality of colloidal nanosilica in simulated concrete environments was investigated using dynamic light scattering. A concrete environment was simulated by creating a synthetic pore solution that mimicked the ionic concentration and pH value of ultrahigh-performance concrete in the fluid state. Four colloidal nanosilica samples were used, ranging in particle sizes from 5 to 75 nm, with differing solid contents and stabilizing ions. It was found that the sodium stabilized 20 nm NS sol remains dispersed at a solid concentration of 2 wt % through a variety of pH values with the inclusion of potassium ions. Calcium ions are a major contributor to the agglomeration of NS sols and only small concentrations of calcium ions can drastically affect the dispersion quality.

Experimental research on rheological and mechanical properties of nano silica sol grout

Nano silica sol (NSS) grouting is an effective method to improve water blocking capacity of rock fracture and fine sand. However, the mechanical and rheological properties of NSS grout remain poorly investigated. We study the properties by (1) measuring gelling time of NSS grout with a different accelerator dosage, (2) measuring shear strength of NSS with fall-cone test, (3) measuring the permeability coefficient of NSS, (4) measuring uniaxial compressive strength (UCS) of NSS mortar with different accelerator dosage and different curing conditions, and (5) conducting scanning electron microscopy (SEM) tests on NSS mortars at the sample age of 28 days. A new parameter R is introduced to represent the amount-of-substance concentration ratio of silicon dioxide (SiO2) and calcium chloride (CaCl2) in the mixture of NSS grout and the accelerator solution. It is proven that the gelling time of NSS grout increases exponentially with the increase of R. The equation of real-time viscosity and permeability length is derived. The strength development of NSS and the stress–strain relationship of NSS mortar is observed. The corresponding relationship between the micromorphology and macro-mechanical properties of NSS mortar is revealed. Furthermore, the non-monotonicity of experimental data is discussed and a possible reason is given.

Determination of growth kinetics and size dependent structural, morphological, optical characteristics of sol-gel derived silica nanoparticles in silica matrix

Abstract Nanocomposite silica thin films made using the sol-gel method were studied. The nano-silica films were prepared using a mixture of tetraethyl orthosilicate (TEOS), deionized water, ethanol, and ammonia solution. To control the growth of the particles inside the film, the nanocomposite silica film was prepared using a mixture of the nano-silica sol and the silica sol. The change in the particle size with the heat treatment temperature ranging from 450 °C to 1100 °C was investigated. X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), NKD (refractive index-N, extinction coefficient-K, and thickness-D) and ultraviolet-visible (UV-Vis) spectrophotometry were used for characterization purposes. The XRD studies showed that the nano-silica thin films were amorphous at all annealing temperatures except for 1100 °C. The_-cristobalite crystal structure formed at the annealing temperature of 1100 °C. Optical parameters, such as refractive indices and extinction coefficients, were obtained using the NKD analyzer with respect to the annealing temperature of the films. The activation energy and enthalpy of the nanocomposite silica film were evaluated as 22.3 kJ/mol and 14.7 kJ/mol, respectively. The cut-off wavelength values were calculated by means of extrapolation of the absorbance spectra estimated using the UV-Vis spectroscopy measurements. A red shift in the absorption threshold of the nanocomposite silica films indicated that the size of the silica nanoparticles increased with an increase of the annealing temperatures from 450 °C to 900 °C, and this confirms the quantum confinement effect in the nanoparticles.

Synergistic Effects and Mechanism of Modified Silica Sol Flame Retardant Systems on Silk Fabric.

The nano-silica sol was prepared by sol-gel method, and the boric acid, urea, cyanoguanidine, melamine cyanurate (MCA), 1-hydroxyethane 1,1-diphosphonic acid (HEDP), and 6H-dibenz (C,E) (1,2) oxaphosphorin-6-oxide (DOPO) were added to the silica sol to modify the flame retardant through physical doping and chemical bonding. According to the formula proposed by Lewin, the calculation of flammability parameters were obtained by the limiting oxygen index meter, the micro calorimeter, the vertical burner, and the thermogravimetric analyzer proved that there was a synergistic or additive effect between the B/N/P flame retardant and the silica sol. Fourier transform infrared (FT-IR) spectrum, scanning electron microscopy, and pyrolysis gas chromatography-mass spectrometry were used to characterize the morphology, structure, and pyrolysis products of treated silk fabric and residues after combustion. The results show that the flame retardancy of silica-boron sol is mainly caused by endothermic reaction and melt covering reaction. Silicon-nitrogen sol acts as a flame retardant through endothermic reaction, release of gases, and melting coverage. Silicon-phosphorus sol achieves flame retardancy by forming an acid to promote formation of a carbon layer and melting coverage. Silica sol and other flame retardants show excellent flame retardanty after compounding, and have certain complementarity, which can balance the dosage, performance, and cost of flame retardants, and is more suitable for industrial development.

Evaluation of variable pressure dead-end ultrafiltration behaviors of nanocolloids based on filter cake properties

Variable pressure dead-end ultrafiltration experiments including constant rate filtration experiments were performed for nanocolloids such as protein solutions of bovine serum albumin (BSA), lysozyme and myoglobin, and nano-silica sol. The relationships for representing the dependences of average specific cake resistance and average cake porosity on the pressure drop across the filter cake necessary for the evaluation of these filtration behaviors were determined from the temporal flux decline data obtained in a step-up pressure dead-end ultrafiltration experiment using a filter with an abrupt reduction in the effective filtration area. In case of a relatively high colloid concentration, it was necessary to acquire the porosity data for evaluation of ultrafiltration behaviors based on the compressible cake filtration model. The filtration behaviors were successfully evaluated even in a relatively high pressure rising rate. Moreover, the pressure variation calculated based on the constant rate filtration equation enabled us to maintain a constant filtration rate in dead-end ultrafiltration.

Efficient solid reducing agent CaO/SiO2 hybrid composite for hydrogen fluoride elimination

An advanced solid reducing agent, i.e., a CaO/SiO2 composite has been optimized to improve the hydrogen fluoride (HF; a green house gas) elimination in semiconductor-based industrial applications. To avoid the Ca(OH)2 formation and enhance the HF removal efficiency of CaO, the hydrophobic properties of silica (SiO2) have used as a catalyst materials to enhance the stability of CaO/SiO2 solid reducing agent in the present investigation. The novel composite structure based on CaO/SiO2 was prepared using various concentrations of hydrophobic nano-silica sol and Ca(OH)2. The composite was characterized by contact angle goniometry, thermogravimetry analysis, and scanning electron microscopy. The water contact angle of the CaO/SiO2 composites significantly increased with increasing SiO2 content. In particular, angles of 61.6°, 73.7°, 84.8°, and 84.9° were obtained for SiO2 concentrations of 20, 40, 60, and 80 wt.%, respectively. These results suggest that the hydrophobic nature of the composites was improved with the addition of 60 and 80 wt.% of SiO2. Moreover, the surface properties were measured using the nitrogen Brunauer–Emmett–Teller method for obtaining the weight ratios (wt.%) and calcinations times. The determined specific surface areas (SSAs) were 16.19, 27.25, 32.86, and 40.56 m2/g for 80:20, 60:40, 40:60, and 20:80 CaO/SiO2 composites, respectively. From the water contact angle and SSA analysis, the optimum hydrophobic nature of CaO/SiO2 composites for HF removal was achieved at a weight ratio of 40:60 (Ca(OH)2/SiO2) at the calcination temperature of 650 °C. The perfluorinated compound (PFC) removal rate is 80 and 88% for a common regenerative catalytic system (RCS) catalyst and the CaO/SiO2 reaction-enhanced (RE)-RCS catalyst, respectively. In addition, higher amount of HF elimination is successfully achieved using CaO/SiO2 solid reducing agent. During the RE-RCS process, SiO2 acts as a catalyst to prevent the formation of Ca(OH)2 when CaO is exposed to water.

Long-Term Mechanical Behavior of Nano Silica Sol Grouting.

The longevity of grouting has a significant effect on the safe and sustainable operation of many engineering projects. A 500-day experiment was carried out to study the long-term mechanical behavior of nano silica sol grouting. The nano silica sol was activated with different proportions of a NaCl catalyst and cured under fluctuating temperature and humidity conditions. The mechanical parameters of the grout samples were tested using an electrohydraulic uniaxial compression tester and an improved Vicat instrument. Scanning electron microscope, X-ray diffraction, and ultrasonic velocity tests were carried out to analyze the strength change micro-mechanism. Tests showed that as the catalyst dosage in the grout mix is decreased, the curves on the graphs showing changes in the weight and geometric parameters of the samples over time could be divided into three stages, a shrinkage stage, a stable stage, and a second shrinkage stage. The catalyst improved the stability of the samples and reduced moisture loss. Temperature rise was also a driving force for moisture loss. Uniaxial compressive stress-strain curves for all of the samples were elastoplastic. The curves for uniaxial compression strength and secant modulus plotted against time could be divided into three stages. Sample brittleness increased with time and the brittleness index increased with higher catalyst dosages in the latter part of the curing time. Plastic strength-time curves exhibit allometric scaling. Curing conditions mainly affect the compactness, and then affect the strength.

Can nanosilica sol prevent oil well cement from strength retrogression under high temperature?

Under high temperature, the compressive strength of cement will decrease with curing time, which is called strength retrogression. It is a great challenge to prevent strength retrogression, especially for cementing deep and thermal wells. In the past, cementing crew tend to improve the compressive strength of cement under high temperature by the addition of 35%–40% silica flour (SF). Nanosilica (NS) and silica flour have the same chemical composition, i.e., SiO2. But NS possesses smaller particle size and larger specific surface area, which can have some special properties that SF does not have. In this paper, we investigated the effect of nanosilica sol (NSS) on the oil well cement under high temperature and revealed its mechanism through experiments. The results indicate that NSS can prevent cement stone from strength retrogression under high temperature, though it is unable to improve the compressive strength. With high addition, NSS can react with Ca(OH)2 (i.e., pozzolanic reaction), but the reaction product C3S2H4 has a honeycomb and loose structure. Besides, after adding 6–8% NSS, the compressive strength of cement containing 35% SF will be further improved. This is because the nanosilica particles are able to fill in the pores of the spatial structure formed by the cement hydration products, which makes a more compact and dense structure. This study lays a foundation for the application of nanosilica and other nanomaterials as cement additives, and also provides a new perspective for high-temperature well cementing design.

Study on the preparation and properties of UV curable polyurethane materials modified by organic silicon

In this paper, polyester polyol, toluene diisocyanate (TDI) and hydroxyethyl acrylate (HEA) were taken as the raw materials to synthesize polyurethane acrylate. UV curable organic silicon nano sol was synthesized by γ-methacryloxypropyltrime-thoxysilane. The UV curable polyurethane materials modified by organic silicon were prepared based on the UV curable organic silicon nano sol and synthesized polyurethane acrylate. This paper studies on the mechanical properties of organic silicon modified UV curable polyurethane materials and puts forward the micro model that inorganic phase is bonded to the resin in the form of chemical bonds. The results show that the heat resistance and mechanical properties of hybrid materials are improved with the increase of the nano silica sol’s contents , the abrasion resistance of hybrid coatings is also improved and the silica nano particles are well dispersed in the organic phase.

Compression and expansion properties of filter cake accompanied with step change in applied pressure in membrane filtration

Abstract In order to well elucidate the true nature of filter cake formed in membrane filtration of aqueous colloids, the transient flux decline behaviors accompanied with step-up and step-down changes in the applied filtration pressure during the course of constant pressure filtration were investigated by carrying out both microfiltration experiments of kaolin slurry and ultrafiltration experiments of nanosilica sol under various experimental conditions. When the applied pressure was increased stepwise, for each colloid the plot of the reciprocal filtration rate vs. the filtrate volume per unit membrane area referred to as the Ruth plot tends to approach a linear relationship obtained in constant pressure filtration conducted under the increased pressure condition from the beginning of filtration, after a transient period when the preformed cake under the initial pressure was compressed. In contrast, in the case of the step-down change in the applied pressure, when the volume of the preformed cake is adequate, the plot after a transient period tends to approach a higher straight line parallel to a linear relationship for constant pressure filtration conducted under the decreased pressure condition from the beginning. Such flux decay behaviors were well described by the expression having two constants: one is the constant representing the final filterability for the preformed filter cake, and the other is the rate constant describing the change rate in the structure of preformed cake resulting from a pressure jump. Moreover, the influence of experimental conditions on the cake reversibility and the rate constant was revealed both for kaolin slurry and for nanosilica sol.

Durable polyorganosiloxane superhydrophobic films with a hierarchical structure by sol-gel and heat treatment method

For a surface to be superhydrophobic a combination of surface roughness and low surface energy is required. In this study, polyorganosiloxane superhydrophobic surfaces were fabricated using a sol-gel and heat treatment process followed by coating with a nanosilica (SiO2) sol and organosiloxane 1, 1, 1, 3, 5, 5, 5-heptamethyl-3-[2-(trimethoxysilyl)ethyl]-trisiloxane (β-HPEOs). The nano-structure was superimposed using self-assembled, surface-modified silica nanoparticles, forming two-dimensional hierarchical structures. The water contact angle (WCA) of polyorganosiloxane superhydrophobic surface was 143.7±0.6°, which was further increased to 156.7±1.1° with water angle hysteresis of 2.5±0.6° by superimposing nanoparticles using a heat treatment process. An analytical characterization of the surface revealed that the nano-silica and polyorganosiloxane formed a micro/nano structure on the films and the wetting behaviour of the films changed from hydrophilic to superhydrophobic. The WCA of these films were 143.7±0.6° and at heat treatment temperatures of less than 400°C, the WCA increased from 144.5±0.7° to 156.7±1.1°. The prepared superhydrophobic films were stable even after heat treatment at 430°C for 30min and their superhydrophobicity was durable for more than 120days. The effects of heat treatment process on the surface chemistry structure, wettability and morphology of the polyorganosiloxane superhydrophobic films were investigated in detail. The results indicated that the stability of the chemical structure was required to yield a thermally-stable superhydrophobic surface.

STUDY OF MULTIFUNCTIONAL NANOCOATED COLD PLASMA TREATED POLYESTER COTTON BLENDED CURTAINS

Over the past decade, considerable progress has been made in the applications of TiO2nanoparticles to get the multifunctional textiles. This paper presents the consequences of pretreatment of polyester fabric using cold plasma in the presence of oxygen — which might be beneficial for bonding nanoparticles over the polyester cotton blended curtains. Moreover, this paper presents the primary technique for suspending titanium dioxide (TiO2) nanoparticles into nanosilica sol for nanocoating of polyester cotton blended curtains. In addition, the detailed characterization of nanocoating has been made using Field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD); and the consequences of nanocoating with and without plasma treatment for enhancing the different properties i.e. antistatic, anti UV and antibacterial property are discussed. Furthermore, the consequences of nanocoating with and without plasma treatment on the mechanical properties have also been discussed.

Study of Nano-Titania Addition on Mechanical Strength of Mullite-Bonded Alumina-Silicon Carbide Nano-Composites

In this study, the effect of nano-titania addition on the mechanical strength of mullite-bonded alumina-siliconcarbide nano-composites was investigated. To this end, the gel-casting process via nano-silica sol was used for shaping the nano-composite. * تابتاکم لوئسم ، پ یکینورتکلا تس : sasan.otroj@gmail.com