Nano SiO2 Research Articles

Study on improving the efficiency of crystalline silicon photovoltaic module with down-conversion chlorophyll film

Crystalline silicon (c-Si) solar cells cannot make full use of solar energy at present, especially the short wavelength (300–500 nm) energy. Owing to the inherent problem, c-Si photovoltaic (PV) modules are still facing the trouble of low PV conversion efficiency. Applying spectral down-conversion (DC) materials to transform underutilized solar spectrum is an effective way to improve the problem. In this study, inspired by chlorophyll (Chl) fluorescence phenomenon, Chl film were specially prepared by encapsulating Chl with oxygen insulating material as spectral DC material. Then, to enhance Chl stability, nano SiO2 was added to the film-forming solution. The spectroscopic properties of the Chl films were analyzed, and the output power characteristics of the PV modules coated with the Chl films were inspected. The experimental results indicate that the prepared Chl film has good spectral conversion performance, and can convert light of about 400 nm into about 670–680 nm which is suitable for PV modules. After being exposed outdoors for about 30 days, the maximum power of the PV module coated by the Chl film with SiO2 is still improved by 9.2%. Since the Chl can be obtained from nature by an economical way, the Chl film is a promising material to improve the power generation efficiency of c-Si PV modules.

Effect of micron-scale pores increased by nano-SiO2 sol modification on the strength of cement mortar

Abstract A study was conducted through quantitative calculations on the correlation between the micron-scale pores and the strength of nano-SiO2 (NS) sol reinforced cement mortar. The strength, pore structure, and microstructure of NS sol modified mortar were investigated, and the mortars were made equivalent to a two-phase material comprised of pores and mortar matrix; the model was applied to conduct a quantitative analysis of the correlation between pores and the strength. According to the research results, the modification made to the mortar using the NS sol led to significantly increased early strength and the level of porosity was also increased. Furthermore, the addition of NS caused a change to the C–S–H gel morphology of cement hydration products. As revealed by the results of quantitative analysis, the addition of 1.5 and 3% NS improved the mortar matrix strength by 29.3 and 56.6%, respectively. Moreover, the ratio between the mortar strength (f c) and matrix strength index (K) exhibited a nonlinear correlation with the porosity negatively. It was thus inferred that the increase in mortar porosity inhibited the improvement of mortar strength under the influence of NS sol.

24.4% industrial tunnel oxide passivated contact solar cells with ozone-gas oxidation Nano SiOx and tube PECVD prepared in-situ doped polysilicon

Ozone-gas oxidation (OGO) technology, capable of integrating into tube plasma-enhanced chemical vapor deposition (PECVD) technology, is developed to prepare the Nano SiO x layer for tunnel oxide passivated contact (TOPCon) solar cells in this work. The effects of gas flow, oxidation temperature, and annealing temperature on passivation quality are investigated. The X-ray photoelectron spectroscopy (XPS) indicates that OGO SiO x possesses a Si 4+ proportion of about 20%, higher than the nitric acid oxidized (NAOS) SiO x and plasma-assisted N 2 O oxidation (PANO) SiO x . The implied open-circuit voltage ( iV oc ) of the hydrogenated lifetime sample is promoted to more than 740 mV with the highest value of 748 mV, corresponding to a lowest single-sided saturation current density ( J 0,s ) of 3.1 fA/cm 2 . The contact resistivity extracted from the Cox-Strack method is < 9 mΩ cm 2 as the annealing temperature is more than 840 °C. Finally, we prepared the large-sized TOPCon solar cells with an average efficiency of 24.37% and a maximum efficiency of 24.41%, respectively. The above work shows that the tube PECVD technology integrated with ozone gas oxidation has the potential for the mass-production TOPCon industry. • Ozone-gas oxidation (OGO) technology is integrated into tube PECVD technology. • OGO SiO x and P-doped a-Si:H can be prepared by the same graphite-boat carrier. • OGO SiO x shows a high proportion of Si 4+ without ion bombardment. • The highest iV oc of 748 mV corresponding to the lowest J 0,s of 3.1 fA/cm 2 . • Average efficiency of 158.75 mm TOPCon cells reaches ∼24.4%.

Heat Stability and Icing Delay on Superhydrophobic Coatings in Facile One Step.

Superhydrophobic coatings are limited to poor durability and a tedious preparation process. In this work, an efficient, eco-friendly, and cost-effective sol-gel method is developed for preparing superhydrophobic surfaces using an all-in-one suspension composed of methyltrimethoxysilane (MTMS), nano silicon dioxide (SiO2) particles, and micron zinc oxide (ZnO) particles. Superhydrophobic coatings with a contact angle (CA) up to 153.9° and a sliding angle (SA) of about 3.0° are prepared on Q235 steel substrates using MTMS 5 mL, 0.8 g of nano SiO2, and 0.2 g of micron ZnO. The morphology of the superhydrophobic coating is characterized by scanning electron microscopy (SEM), and the surface is covered with a micro- and nano-scaled hierarchical rough structure. A series of tests are conducted, including long-term stability tests and thermostability tests. The CAs are all above 150°, and the SAs are below 6.3°, indicating the excellent static stability of the prepared superhydrophobic coatings. Moreover, the CA of the superhydrophobic coating remains above 152° after 120 h of UV exposure, and the time for a water droplet to freeze on the surface of the superhydrophobic coating is 18 times of the bare Q235 steel, indicating that the superhydrophobic coating exhibits good resistance to UV radiation and icing-delay properties.

Functionalized nano-SiO2 for improving the cycling stability of 4.6V high voltage LiCoO2 cathodes

In order to elevate the high voltage resistance and stability of LiCoO2 cathodes, its application potentialis further excavated. In this paper, the functionalization of nano SiO2(PDA@SiO2) was realized by using the self polymerization coating characteristics of dopamine. Its functionalization with the fumed SiO2 nano-particle center allows even 2% PDA@SiO2 to be uniformly coated onto a LiCoO2 cathode via rotary steaming. It is demonstrated by scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS) that the functional nano-coating is distributed homogeneously on the surface of LiCoO2 particles. The close interaction between nano PDA@SiO2 coating and LiCoO2 particles is emerged, which avoids the agglomeration of nano SiO2 and enhances the function of solid superacid formed by fumed SiO2. The X-ray photoelectron spectroscopy (XPS) shows that less undesired side products are deposited on the surface of LiCoO2, and X-ray diffraction (XRD) and SEM indicate that the lattice expansion and irreversible phase transformation of crystal structure are effectively inhibited. The interface stability and ionic conductivity of LiCoO2 cathodes at high voltage are elevated substantially. Thus, the cycle stability of LiCoO2 cathodes during charge and discharge at 4.6 V high voltage is significantly improved. At room temperature, the modified LiCoO2 cathode with functionalized nano-SiO2 achieved a reversible capacity of around 190 mAh g−1 with the capacity retention of 78% after 200 cycles at 1C, along with a relatively high cyclability of 68% capacity retention after 100 cycles at 1C and 50°C.

A novel lithium ion-imprinted membrane with robust adsorption capacity and anti-fouling property based on the uniform multilayered interlayer

Effective modification strategies contribute to high adsorption capacity, separation efficiency and anti-fouling properties of ion-imprinted membranes. The design of a homogeneous and hydrophilic interlayer between the substrate membrane and ion-imprinted layer is crucial factor for the excellent performance of ion-imprinted membranes. In this study, a novel multilayered interlayer (SiO2@SP-PDA) was developed and uniformly coated on the substrate surface (PVDF membrane). The polydopamine (PDA) prepared via oxidation of sodium periodate (SP-PDA) increases the uniformity of SiO2@SP-PDA modification, which reduces the agglomeration of the ion-imprinted layer, and thereby boosts the adsorption capacity to 231.77 mg·g−1. The prepared ion-imprinted membrane (SiO2@SP-PDA-IIM) exhibits a favorable anti-fouling property due to the incremental hydrophilicity and the presence of SiO2 nano interlayer. Based on the XDLVO theory, it can be deduced that the SiO2 modification increases the membrane surface electron donor tension (γ−), which plays an essential role in enhancing the anti-fouling property of SiO2@SP-PDA-IIM. In this paper, the design of multilayered structure is of great significance to make the ion-imprinted membrane be a potential candidate for Li+ efficient separation in natural water.

Influencing factors analysis and optimized prediction model for rheology and flowability of nano-SiO2 and PVA fiber reinforced alkali-activated composites

Alkali-activated composites (AAC) has real potential as a repair material of defective concrete structures by virtue of fast setting, high strength, and recyclability. Understanding the workability of AAC is the key to realize this environmental technology as a new repair material. In this work, the effects of water-reducing admixture, nano-SiO2 (NS), and polyvinyl alcohol (PVA) fiber contents on the rheology and the flowability of AAC were investigated through the impeller-rheometer and L-box tests respectively. Based on the results of rheology and flowability, the least squares support vector regression (LS-SVR) method was used for the multi-output prediction of the rheological parameters of AAC. The test results indicate that the fresh mixtures can be regarded as a Bingham fluid, and the proper NS and water-reducing admixture contents can promote the rheology and the flowability of the mixtures, while excessive PVA fiber and NS have negative influence on the workability. The predicted results exhibit that the predicted rheological parameters of mixtures are concordant with the experimental values (the correlation coefficients of static yield stress, dynamic yield stress and plastic viscosity are 0.990, 0.963 and 0.976, respectively). Consequently, the LS-SVR method can be applied for the inverse analysis of the rheological parameters of AAC.

Properties and Simulating Research of Epoxy Resin/Micron-SiC/Nano-SiO2 Composite

The dielectric behavior of insulations is a key factor affecting the development of anti-corona materials for generators. Epoxy resin (EP), as the matrix, is blended with inorganic fillers of micron SiC and nano SiO2 to investigate the effect of micro and nano doping on the conductivity and breakdown mechanism of the composites. Using experimental and simulation analysis, it is found that the effect of nano-SiO2 doping concentration on the conductivity is related to the dispersion of SiC particles. The lower concentration of SiO2 could decrease the conductivity of the composites. The conductivity increases with raising the nano-SiO2 doping concentration to a critical value. Meanwhile, the breakdown field strength of the composites decreases with the rising content of SiC in constant SiO2 and increases with more SiO2 when mixed with invariable SiC. When an equivalent electric field is applied to the samples, the electric field at the interface of micron particles is much stronger than the average field of the dielectric, close to the critical electric field of the tunneling effect. The density of the homopolar space charge bound to the surface of the stator bar elevates as the concentration of filled nanoparticles increases, by which a more effective Coulomb potential shield can be built to inhibit the further injection of carriers from the electrode to the interior of the anti-corona layer, thus reducing the space charge accumulation in the anti-corona layer as well as increasing the breakdown field strength of the dielectric.

Effect of Nanosilica and Multiwalled Carbon Nanotubes on the Mechanical and Impact Performance of Unidirectional Kevlar/Epoxy Based Composites

The introduction of numerous nanoparticles into nanotechnology in recent years has opened the door for the incorporation of nanoparticles into polymeric-based composite materials for mechanical improvement. Composite materials are becoming a promising substitute material in the fabrication of numerous components due to their high weight-to-strength ratio and mechanical characteristics such as tensile Strength, flexural Strength, interlaminar shear strength, and impact strength. This research aims to determine the effect of a combined mixture of silica and multiwalled carbon nanotube particles (MWCNT) on the mechanical and impact properties of unidirectional Kevlar (UD)/epoxy composites for use in defence and aerospace applications. The addition of these Nanofillers results in high-performance reinforcement and the formation of hybrid composites with improved properties due to their use. The addition of specific nanomaterials can further enhance these characteristics, dependent on the concentration at which they are introduced into the solution. The most challenging aspects of incorporating nanomaterials into matrix materials are ensuring uniform mixing of the nanomaterials with the matrix material and increasing the viscosity of the matrix material when the nanomaterials are introduced into the matrix. Using different weight percentages, it is possible to determine the optimal ratio of nanofiller for predicting the enhanced mechanical properties of nano-composites. Preparation of the composite with different weight percentages (1 percent and 3 percent) of Nano SiO2 particles mixed with 0.25 percent MWCNT and 6 layers of the UD Kevlar fibre was accomplished using an ultrasonic vibration-assisted hand layup process. Tensile tests, Charpy impact tests, and interlaminar shear strength tests evaluated the material's mechanical properties. Experimental results revealed that tensile strength and impact strength increased by up to 80 percent and 50 percent, respectively, compared to the neat specimens. The ILSS test demonstrates a 271 percent improvement in shear strength at 3 percent and 0.25 MWCNT. The overall results determined that the combination of 3 percent SiO2 and 0.25 percent MWCNT provided the most enhanced mechanical properties while also being the most optimized. This study's findings indicate that applying a nano-silica and MWCNT mixture of Nanofillers to Kevlar fabrics is a promising method for improving a Kevlar-based hybrid composite's mechanical and impact energy absorption laminate.

Understanding the Lightning Impulse Discharge Characteristics of Nano Silica Modified Sunflower Oil for High-Voltage Insulation Applications

Vegetable oils with nanotechnology added to them are a possible replacement for mineral oils in power transformer applications today. Because of the size and production cost reductions as well as the oil's high level of biodegradability, this could result in an increase in the dielectric strength of insulating fluid. Since transformers are mainly used for outdoor applications, understanding the capability of insulating fluid to withstand lightning discharge is a vital issue. This study used experimental analysis to compare the lightning discharge performance of pure sunflower oil and sunflower oil modified with SiO2 (Nano) at various weight-per-volume concentrations of 0.01 %, 0.05 %, and 0.1 %. This experimental work was conducted with 1.2/50 µs of standard lightning impulse voltage with positive polarity. The result illustrated that the nano-modified sunflower oil had greater lightning impulse withstand strength than the pure sunflower oil.

The effects of silanized rubber and nano-SiO2 on microstructure and frost resistance characteristics of concrete using response surface methodology (RSM)

Waste rubber powder can be used to enhance the frost resistance of cement concrete. Conventionally, only the rubber powder is directly mixed into concrete, but its mechanical properties are reduced significantly. However, mixing modified rubber, nanometer materials, lime ash, and cement concrete can improve the frost resistance and compressive strength of concrete at the same time. The main objective of this paper is to evaluate the potentiality of utilizing silanized rubber (SR) powder and nano-SiO2 (NS) to develop frost-resistant concretes. Determination of the frost-resistant effect of concrete mixture incorporated with SR and NS on the pore structure and mechanical characteristics was performed by response surface methodology (RSM). Results of scanning electron microscopy (SEM) tests along with Fourier transform infrared spectroscopy (FT-IR) are reported to evaluate the effect of frost resistance from microstructure. Results of the conducted tests show that the combination of SR and NS has a synergistic effect, which makes the distribution of voids in concrete more uniform, and the damage of mass loss rate and relative dynamic modulus of elastic (RDME) after a freeze–thaw cycle is lower. At the optimum content of designed concrete, there is a high correlation between frost resistance and void structure.

Nano and mesoscopic SiO2 and ZnO powders to modulate hydration, hardening and antibacterial properties of portland cements

In this study we have utilized silica nano powder (SP) and ZnO mesoscopic powder (ZP), obtained by a sol-gel method, to improve cements. SP and ZP were mixed in various amounts with portland cements and their influence on the hydration-hardening processes and the antibacterial properties of the resulting cement was further assessed.The obtained results demonstrated that cement-based materials could be improved in terms of antimicrobial efficiency when modified with bioactive ZP, as demonstrated in Gram-positive and Gram-negative opportunistic bacteria, but also in yeasts.The addition of ZP to portland cement and pastes, determined an important delay of the portland cement hydration and hardening processes, as resulted from the XRD, FTIR, TG-DTA analyses and compressive strength test performed on mortars hardened up to one year. Silica nano powder had an opposite effect i.e. for an adequate dosage improved the mechanical strengths of portland cement mortar due to physical and chemical effects determined on cement hydration and hardening processes. These results highlight the role of ZP in improving key features of cements which could be further exploited to obtain smart materials, such as self-cleaning and antibacterial portland cements.

Reinforcement of ultra-low dosage of polycarboxylate ether (PCE) grafted nano-silica sol to the mechanical and durable properties of cement mortar

How good dispersion of nano-SiO2 (NS) plays a great influence on how strong reinforcing efficiency to cement-based materials. In this study, a novel nanohybrid of polycarboxylate ether (PCE) grafted nano-silica sol (PCE@NSS) was prepared by sol–gel methods to chemically adsorb PCE onto NSS. The developed nanohybrid showed a higher ultraviolet–visible (UV–Vis) absorbance and slower sedimentation in alkaline solutions, indicating the better dispersion and stability of PCE@NSS than that of untreated NSS. By this way, only 0.05 wt.% addition of PCE@NSS was helpful to refine the capillary pore size and reduce the total porosity of cement mortar, which in turn improved the compressive and flexural strength of cement mortar by 18.34% and 10.5% at 28 days, respectively. In addition, a reinforcing index (R index) with the ratio of strength enhancement % to dosage % was proposed, indicating that the R index of PCE@NSS showed 10 times higher than that of other NS-based nanomaterials reported in literatures, addressing the highly reinforcing efficiency of PCE@NSS to cement mortar. Furthermore, water absorption coefficient of cement mortar was therefore reduced by 12.7% with 0.2 wt.% addition of PCE@NSS. In conclusion, such an ultra-low dosage of PCE@NSS with better dispersion and stability exhibited great potential to reinforce cement-based materials with highly efficiency, lower cost and reduced carbon emissions.

Mechanical properties and microstructure of nano-SiO2 and basalt-fiber-reinforced recycled aggregate concrete

Abstract In this study, nano-SiO2 (NS) and basalt fiber (BF) were used to improve the quality of recycled aggregate concrete (RAC). The crushing value, water absorption, and apparent density of NS-modified recycled coarse aggregate (RA) were determined, and the effects of BF with different contents and lengths on the slump, compressive strength, splitting tensile strength, and flexural strength of RAC and BF-reinforced RAC containing NS-modified RA were analyzed. Finally, the filling effect of NS, the toughening and crack resistance mechanism of BF, and the micro-composite effect between NS and BF were analyzed based on scanning electron microscope (SEM) and energy-dispersive detector (EDS) measurement. The results show that the optimum modified concentration of NS solution is 2%, the content of BF is the main factor affecting the mechanical properties of concrete, and the optimum length and content of BF are 12 mm and 0.2%, respectively. For BF-reinforced RAC containing NS-modified RA, the 28 day compressive strength, splitting tensile strength, and flexural strength of RAC increase by 34.28, 40.55 and 54.5%, respectively. Based on SEM and EDS measuring, NS can react with Ca(OH)2 crystal to form flocculent C–S–H gel, which makes RAC compact and enhances the bonding properties of the interfacial transition zone (ITZ) between BF and the matrix.

Mechanical Properties of Nano-SiO2 Reinforced Geopolymer Concrete under the Coupling Effect of a Wet-Thermal and Chloride Salt Environment.

In this study, the mechanical behaviors of nano-SiO2 reinforced geopolymer concrete (NS-GPC) under the coupling effect of a wet–thermal and chloride salt environment were investigated through a series of basic experiments, and a simulation on the coupling effect of a wet–thermal and chloride salt environment and SEM test were also included. During the experiments for the coupling effect of the wet–thermal and chloride salt environment, an environment simulation test chamber was utilized to simulate the wet–thermal and chloride salt environment, in which the parameters of relative humidity, temperature, mass fraction of NaCl solution and action time were set as 100%, 45 °C, 5% and 60 d, respectively. The content of nano-SiO2 (NS) particles added in geopolymer concrete (GPC) were 0, 0.5%, 1.0%, 1.5% and 2.0%. The result indicated that the mechanical properties of NS reinforced GPC decreased under the coupling effect of the wet–thermal and chloride salt environment compared to the control group in the natural environment. When the NS content was 1.5%, the cube and splitting tensile strength, elastic modulus and impact toughness of GPC under the coupling environment of wet–thermal and chloride salt were decreased by 9.7%, 9.8%, 19.2% and 44.4%, respectively, relative to that of the GPC under the natural environment. The addition of NS improved the mechanical properties of GPC under the coupling effect of the wet–thermal and chloride salt environment. Compared to the control group without NS, the maximum increment in cube compressive strength, splitting tensile strength and elastic modulus of NS–GPC under the coupling effect of the wet–thermal and chloride salt environment due to the incorporation of NS reached 25.8%, 9.6% and 17.2%, respectively. Specifically, 1.5% content of NS increased the impact toughness, impact numbers of initial crack and the ultimate failure of GPC by 122.3%, 109% and 109.5%, respectively.

The influence of hydrogen bond and electrostatic interaction on the mechanical properties of the WPU/modified SiO2 nanocomposites

A variety of nano SiO2 microspheres with negative charge or positive charge were prepared by hydrochloric acid treatment or/and γ-mercaptopropyltrimethoxysilane modification respectively. The obtained modified SiO2 with different content of -OH or -SH and different charges were physically introduced into water-borne polyurethane (WPU) dispersion to fabricate the WPU/modified SiO2 nanocomposites with interfacial interaction of hydrogen bond and electrostatic interaction. The influence of interfacial interaction (hydrogen bond and electrostatic interaction) between WPU and modified SiO2 on the interface structure and mechanical properties of the WPU/modified SiO2 nanocomposites were investigated. The results showed that when both hydrogen bond and electrostatic interaction were present between WPU and modified SiO2, the microstructure and the tensile strength of the WPU/modified SiO2 nanocomposite were mainly affected by the electrostatic interaction, while the elongation at break was mainly affected by the hydrogen bond interaction. Overall, a methodology of the combination of molecular dynamics simulation and experiment study was established to reveal the influence of surface characteristic of SiO2 on the interface interaction and mechanical properties of the WPU/modified SiO2 nanocomposites.

Zeolite Containing Mortars Reinforced with Graphene Oxide Synthesized by Hydrolysis of Tetraethyl Orthosilicate

In the last decade, the use of nanomaterials such as graphene oxide (GO) with their noticeable potential for reinforcing cement derivatives has been considered. Unfortunately, the poor dispersion of graphene oxide in cement matrix due to the high alkalinity of the environment has disrupted the final performance of cementitious composites. In this study, GO was modified in a synthesis process with tetraethyl orthosilicate (TEOS) and was coated with Nano-SiO2 (NS) particles, and NS and GO (NS&GO) nanohybrid was prepared. The dispersion behavior of NS&GO nanohybrid was examined by Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and a map analysis. Also, natural zeolite with high pozzolanic activity was used in order to reduce the alkalinity of the cement environment. In order to compare single and hybrid effects of NS&GO, eight mortar mixtures were considered, and their mechanical, durability, and transfer properties were evaluated. The results showed that the mortar which contained NS&GO nanohybrid and 15% zeolite (by mass of cement) had the best results. These results indicate that the formation of covalent bonds between the silica coating and the carboxylate groups of GO reduces the agglomeration of GO nanosheets. Also, zeolite prevents the formation of O─ Ca─ O bonds by consuming portlandite and reducing Ca+2 ions in the cement environment. Finally, NS&GO nanohybrid through nucleation performance and zeolite through pozzolanic properties improved the durability properties of mortars.

Hybrid nanoparticles based on novel Schiff Base for durable flame retardant and antibacterial properties

A large amount of cellulose is produced by photosynthesis every year, and cellulose products are widely used in daily life. However, flammability and easy to breed bacteria of cellulose has hidden risk of fire and public health during using, and the materials that can endow cellulose with flame retardancy and antibacterial properties is still lacking. Herein, novel hybrid nanoparticle (SiDP) based on inorganic nano SiO 2 , Schiff base and quaternary ammonium salt was developed to synchronize these two properties. Wherein the thermal stability of nano SiO 2 and the cross-linking structure of Schiff base played as synergistic flame retardant for the nanoparticle while quaternary ammonium salt of N, N′-dimethyl-N-(3-(trimethoxy silyl) propyl) octadecan-1-aminium chloride (DMOAC) was introduced to provide antibacterial property. The results demonstrated that the modified cotton fabrics were significantly out-performing of flame retardancy and antibacterial properties. Wherein LOI increased to 27.6%, the peak of heat release rate (pHRR) reduced by 34.2%, and capability of self-extinguishing was achieved. The antibacterial of SiDP and modified cotton fabrics were substantiated up to 99.9% against the Staphylococcus aureus and Escherichia coli. More excitingly, low toxicity of SiDP was confirmed via MTS assay by L929 fibroblast cells. The anti-infection in-vivo model was constructed and confirmed SiDP had a positive prevention of infection based on the wound healing rate of 91.1% after 14 days' treatment. The flame retardancy, antibacterial and biocompatibility of SiDP indicated it was an ideal candidate of nanomaterials in cellulose modification.

The effects of Nano SiO 2 and Silica Fume on the properties of concrete

The effects of Nano SiO 2 and Silica Fume on the properties of concrete

GGBS hydration acceleration evidence in supersulfated cement by nanoSiO2

Supersulfated cement (SSC) is a potential low-carbon cementitious binder, but its sluggish property-gain feature owing to GGBS's weak reactivity has significantly limited its application. For the first time, the dissolution of GGBS and the precipitation of hydrates in SSC are controlled by the unique physicochemical features of nanoSiO2 (NS). SSC's hydration and hardening properties with 0%–3% NS were systematically investigated. The results showed that NS enhances the strength of SSC at both early and late ages, and the strength of SSC mortar can be doubled by 3% NS at 90 days. It continuously increases the reaction rate of SSC, resulting in a rise in the gel phase content, a decrease in gypsum consumption, and a reduction in the formation of ettringite of varying morphology. NS increases the reaction degree of GGBS, forming more C-(A)-S-H gel and significantly compacting the microstructure of SSC. The controlling variables leading to the continuous growth of macro-property gain of SSC have been identified as the reduction of calcium ions in SSC by NS and the concomitant enhancement of GGBS dissolution. This work demonstrated a viable method of dealing with issues related to the production and utilization of SSC.