Rheological behavior of fumed silica suspension in polyethylene glycol

The rheological behavior of fumed silica suspensions in polyethylene glycol(PEG) was studied at steady and oscillatory shear stress using AR 2000 stress controlled rheometer. The systems show reversible shear thickening behavior and the shear-thickening behavior can be explained by the clustering mechanism. The viscosity and the degree of shear-thickening of the systems strongly depend on the mass fraction of the silica, the molecular weigh of PEG and the frequency used in the rheological measurement. The silica volume fraction of the systems is 1.16% 3.62%, corresponding to the mass fraction of 4%9%. The shear-thickening taking place in the low volume fraction may contribute to the fractal nature of the silica. At oscillatory shear stress, when the shear stress is less than the critical stress, the storage modulus decreases significantly, meanwhile the loss modulus and the complex viscosity almost remain unchanged; when the shear stress is larger than the critical stress, the storage modulus, the loss modulus and the complex viscosity increase with the increase of shear stress. The loss modulus is larger than the storage modulus in the range of stress studied and both moduli depend on frequency.

Effect of silica fume and glass powder for enhanced impact resistance in GGBFS-based ultra high-performance geopolymer fibrous concrete:An experimental and statistical analysis

Solid waste recycling is an economically sound strategy for preserving the environment,safeguarding natural resources,and diminishing the reliance on raw material consumption.Geopolymer technology offers a significant advantage by enabling the reuse and recycling of diverse materials.This research assesses how including silica fume and glass powder enhances the impact resistance of ultra-high-performance geopolymer concrete(UHPGC).In total,18 distinct mixtures were formulated by substituting ground granulated blast furnace slag with varying proportions of silica fume and glass powder,ranging from 10%to 40%.Similarly,for each of the mixtures above,steel fibre was added at a dosage of 1.5%to address the inherent brittleness of UHPGC.The mixtures were activated by combining sodium hydroxide and sodium silicate solution to generate geopolymer binders.The specimens were subjected to drop-weight impact testing,wherein an examination was carried out to evaluate various parameters,including flowability,density at fresh and hardened state,compressive strength,impact numbers indicative of cracking and failure occurrences,ductility index,and analysis of failure modes.Additionally,the variations in the impact test outcomes were analyzed using the Weibull distribution,and the findings corresponding to survival probability were offered.Furthermore,the microstructure of UHPGC was scrutinized through scanning electron microscopy.Findings reveal that the specimens incorporating glass powder exhibited lower cracking impact number values than those utilizing silica fume,with reductions ranging from 18.63%to 34.31%.Similarly,failure impact number values decreased from 8.26%to 28.46%across glass powder contents.The maximum compressive and impact strength was recorded in UHPGC,comprising 10%silica fume with fibres.

Green synthesis of ZSM-5 using silica fume and catalytic co-cracking of lignin and plastics for production of monocyclic aromatics

ZSM-5 with hierarchical pore structure was synthesized by a simple two-step hydrothermal crystallization from silica fume without using any organic ammonium templates.The synthesized ZSM-5 were oval shaped particles with a particle size about 2.0 μm and weak acid-dominated with proper Brønsted(B)and Lewis(L)acid sites.The ZSM-5 was used for catalytic co-cracking of n-octane and guaiacol,lowdensity polyethylene(LDPE)and alkali lignin(AL)to enhance the production of benzene,toluene,ethylbenzene and xylene(BTEX).The most significant synergistic effect occurred at n-octane/guaiacol at 1:1 and LDPE/AL at 1:3,under the condition,the achieved BTEX selectivity were 24%and 33%(mass)higher than the calculated values(weighted average).The highest BTEX selectivity reached 88.5%,which was 3.7%and 54.2%higher than those from individual cracking LDPE and AL.The synthesized ZSM-5 exhibited superior catalytic performance compared to the commercial ZSM-5,indicating potential application prospect.

Effect of Sodium Tripolyphosphate and Silica Fume on Hydration of High Alumina Cement

It was found that silica fume can reduce the maximum hydration heat release rate of cement by microcalorimetry,inhibit CAH_(10),promote the generation of C_(3)AH_(6)and strätlingite C_(2)ASH_(8),or promote the conversion of CAH_(10)to C_(3)AH_(6).Sodium tripolyphosphate can retard the early hydration of cement,have a slight effect on 1 d hydration products of cement and inhibit the generation hydration products.Sodium tripolyphosphate and silica fume can promote the early hydration of cement,advance the formation of C_(2)ASH_(8)or the conversion from CAH_(10)to C_(3)AH_(6)at 1 d.

Thickening progression mechanism of silica fume-oil well cement composite system at high temperatures

This work studied the thickening progression mechanism of the silica fume-oil well cement composite system at high temperatures(110-180.C)in order to provide a theoretical guidance for the rational application of silica fume in the cementing engineering.Results showed that silica fume seldom affected the thickening progression of oil well cement slurry at 110-120.C,but when temperature reached above130.C,it would aggravate the bulging degree of thickening curves and significantly extend the thickening time,meanwhile causing the abnormal“temperature-based thickening time reversal”and“dosage-based thickening time reversal”phenomena in the range of 130-160.C and 170-180.C respectively.At 130-160.C,the thickening time of oil well cement slurry was mainly associated with the generation rate of calcium hydroxide(CH)crystal.The introduced silica fume would be attracted to the cement minerals'surface that were hydrating to produce CH and agglomerate together to form an“adsorptive barrier”to hinder further hydration of the inner cement minerals.This“adsorptive barrier”effect strengthened with the rising temperature which extended the thickening time and caused the occurrence of the“temperature-based thickening time reversal”phenomenon.At 170-180.C,the pozzolanic activity of silica fume significantly enhanced and considerable amount of C-S-H was generated,thus the“temperature-based thickening time reversal”vanished and the“dosage-based thickening time reversal”was presented.

The Influence of Carbon Nanotubes and Nano-Silica Fume on Enhancing the Damping and Mechanical Properties of Cement-Based Materials

This paper conducted experimental studies on the damping and mechanical properties of carbon nanotube-nanosilica-cement composite materials with different carbon nanotube contents. The damping and mechanical properties enhancement mechanisms were analyzed and compared through the porosity structure test, XRD analysis, and scanning electron microscope observation. The results show that the introduction of nanosilica significantly improves the dispersion of carbon nanotubes in the cement matrix. At the same time, the addition of nanosilica not only effectively reduces the critical pore size and average pore size of the cement composite material, but also exhibits good synergistic effects with carbon nanotubes, which can significantly optimize the pore structure. Finally, a rationalization suggestion for the co-doping of nanosilica and carbon nanotubes was given to achieve a significant increase in the flexural strength, compressive strength and loss factor of cement-based materials.

Improving Impact Toughness of Polylactide/Ethylene-co-vinyl-acetate Blends via Adding Fumed Silica Nanoparticles:Effects of Specific Surface Area-dependent Interfacial Selective Distribution of Silica

Adding fumed silica(Si0_(2))has been considered as an effective method for tailoring the phase morphology and performance of elastomer-toughened plastic binary blends.It has been demonstrated that the selective distribution of SiO_(2) plays a decisive role in the mechanical properties of plastic/elastomer/SiO_(2)nanocomposites,especially for the impact toughness.In this work,we aim to illuminate the role of specific surface area in controlling their selective distribution of fumed SiO_(2) and consequent mechanical properties of plastic/elastomer binary blends.Three types of SiO_(2) with different specific surface areas were incorporated into polylactide/ethylene-co-vinyl-acetate(PLA/EVA)model blends by melt blending directly.It was found that the selective distribution of SiO_(2) is largely determined by their specific surface areas,i.e.SiO_(2) nanoparticles with low specific surface area has a stronger tendency to be located at the interface between PLA matrix and EVA dispersed phase as compared to those with high specific surface area.The specific surface area-dependent interfacial selective distribution of SiO_(2) is mainly attributed to the extent of increased viscosity of EVA dispersed phase in which SiO_(2)nanoparticles are initially dispersed and resultant migration rate of SiO_(2) nanoparticles.The interfacial localized SiO_(2) nanoparticles induce an obvious enhancement in the impact toughness with strength and modulus well maintained.More importantly,in the case of the same interfacial distribution,toughening efficiency is increased with the specific surface area of SiO_(2).Therefore,this is an optimum specific surface area of SiO_(2) for the toughening.This work not only provides a novel way to manipulate the selective distribution of SiO_(2) in elastomer-toughened plastic blends toward high-performance,but also gives a deep insight into the role of interfacial localized nanoparticles in the toughening mechanism.

PREPARATION AND PROPERTIES OF FUMED SILICA/CYANATE ESTER NANOCOMPOSITES

Fumed silica/bisphenol A dicyanate ester （BADCy） nanocomposites were prepared by introducing different contents of nano-sized fumed SiO2 into the BADCy matrix. Two different average primary particle diameters of 12 and 40 nm were chosen. Dibutyltindilaurate （DBTDL） catalyst was chosen to catalyze the cyanate ester group into triazine group via cyclotrimerization reaction. The SEM micrographs indicated that the fumed SiO2 particles were homogeneously dispersed in the poly（bisphenol A dicyanate） matrix by means of ultrasonic treatment and the addition of a coupling agent. The FTIR spectroscopy shows that, not only DBTDL catalyzes the polymerization reaction but also --OH groups of the SiO2 particles surface help the catalyst for the complete polymerization of BADCy monomer. The thermal stability of the cured BADCy can be improved by adequate addition of fumed SiO2. A slight increase in the dielectric constant and dielectric loss values were identified by testing the dielectric properties of the prepared nanocomposite samples. By increasing the SiO2 content, there was a slight increasing in the thermal conductivity values of the tested samples. The obtained results proved that the fumed silica/BADCy nanocomposites had good thermal and dielectrieal properties and can be used in many applications such as in the thermal insulation field.

Preparation,Structure,and Properties of Flexible Polyurethane Foams Filled with Fumed Silica

Flexible polyurethane （PU） foams with different load-ing mass fraction （0%-2.0%） of fumed silica were synthesized by free-rising foaming method. The addition of 1.4% fumed silica makes the cells diffuse more uniform in the PU foam and the temperature of degradation occurring with a maximum weight loss rate is about 7℃ higher than that of pure PU foam. Most signifi-cantly,the sound absorption peaks of the filled PU foams shift to the low frequency region （from 997 Hz to 711 Hz） with increasing fumed silica content （0%-2.0%）. The average sound absorption coefficients of filled PU foams increase except the content of 0.35% fumed silica. The experimental results show that flexible PU foams filled with fumed silica have excellent sound absorption characteristics in low-frequency regions.

Rheology of Poly(vinyl butyral)Solution Containing Fumed Silica in Correlation with Electrospinning

The rheological properties in question are influenced by many factors, ranging from the characteristics of the given polymer or solvent to the flowing conditions. The primary focus of this study is to analyse the rheological behaviour of poly（vinyl butyral）—Mowital B 60 H—（PVB） solutions dissolved in methanol and a blend of these with fumed silica nanoparticles. The preparation of the nanofibrous web and the quality of nanofibres were correlated with the rheology of the polymer solution. It was discerned that drastically intensifying shear viscosity and the elasticity of the solution exerted a negligible effect on the formation of fibres, a finding which has rarely been discussed in the literature. The morphologies and structures of the PVB/silica nanofibrous membranes were investigated by scanning electron microscopy, thermogravimetric analysis and Fourier transform infrared spectroscopy.

Effect of Different Silica Fumes on Properties of Al_(2)O_(3)-SiC-C Castables for Iron Trough

In order to improve the performance of Al_(2)O_(3)-SiC-C castables for iron trough,samples were prepared using brown corundum,dense corundum,activated alumina micropowder,ball pitch,and silicon as main raw materials,calcium aluminate cement as the binder.Several kinds of silica fumes(93SiO_(2),96SiO_(2),and 99SiO_(2))with different particle size distributions and chemical composition were added to research the effects on the properties of castables.The results show that the sample with 99SiO_(2) fume has high water requirement for molding,but the bulk density is the lowest,the apparent porosity is the highest,the oxidation resistance is the worst,and the permanent linear change on heating is low after firing at 1 450 ℃ for 3 h.The bulk density and the apparent porosity of the sample with 93SiO_(2) fume or 96SiO_(2) fume are equivalent,the hot modulus of rupture of the sample with 93SiO_(2) fume is the lowest,and the slag resistance of the sample with 96SiO_(2) fume is the best.The comprehensive performance of the sample with 96SiO_(2) fume is the best.

On the Combination of Silica Fume and Ceramic Waste for the Sustainable Production of Mortar

The combined use of silica fume(SF)and ceramic waste(CW)for the production of mortar is studied.Sand is replaced by 5%,10%,15%and 20%of CW while a fixed 5%percentage(%wt of cement)of SF is used.The results show that the best results are obtained by using silica fume and ceramic waste sand with 15%weight of sand and 5%wt of cement.With the addition of sand ceramic waste(SCW),the mortar compressive strength and density increase,while the porosity displays an opposite trend.The experimental analysis is complemented with theoretical considerations on the matrix strength and related improvements in mechanical behavior.It is shown that the agreement between the experimental values and the estimated values is good.

Enhancing Concrete Properties Using Silica Fume:Optimized Mix Design

In the current work concrete mixes containing(7.0-33.11)weight%silica fume as fractional substitution of cement with water/cement ratio(0.42-0.48)were formulated conferring to an implemented two factorial central composite design.The samples were water cured for 7,28,56,and 90 days.The samples were tested for compressive strength and density.The experimental results approved that compressive strength and density increase with age and with rising silica fume content up to 11.9 wt.%.Response surface analysis results for samples cured for 28 days confirmed that silica fume concrete with developed compressive strength(53.42 MPa)could be prepared by incorporation of 11.9 wt.%silica fume as a substituent for cement using a 0.42 water/cement ratio.An intensification in compressive strength and density(up to 39.3%and 2.6%)respectively was recorded for silica fume concrete mixes in contrast to Portland cement concrete.Overall,the research findings revealed that silica fume concretes prepared with appropriate silica fume content and water/cement ratio exhibited superior strength and density features candidate them to be used effectively in civil engineering structural applications.

Recent research in mechanical properties of geopolymer-based ultrahigh-performance concrete:A review

Due to the growing need for sustainable and ultra-high-strength construction materials,scientists have created an innovative ultra-high-performance concrete called Geopolymer based ultra-highperformance concrete(GUHPC).Besides,in the last few decades,there have been a lot of explosions and ballistic attacks around the world,which have killed many civilians and fighters in border areas.In this context,this article reviews the fresh state and mechanical properties of GUHPC.Firstly,the ingredients of GUHPC and fresh properties such as setting time and flowability are briefly covered.Secondly,the review of compressive strength,flexure strength,tensile strength and modulus of elasticity of fibrous GUHPC.Thirdly,the blast and projectile impact resistance performance was reviewed.Finally,the microstructural characteristics were reviewed using the scanning electron microscope and X-ray Powder Diffraction.The review outcome reveals that the mechanical properties were increased when 30%silica fume was added to a higher dose of steel fibre to improve the microstructure of GUHPC.It is hypothesized that the brittleness of GUHPC was mitigated by adding 1.5%steel fibre reinforcement,which played a role in the decrease of contact explosion cratering and spalling.Removing the need for cement in GUHPC was a key factor in the review,indicating a promising potential for lowering carbon emissions.However,GUHPC research is still in its early stages,so more study is required before its full potential can be utilized.

Performance evaluation of nano-silica and silica fume on enhancing acid resistance of cement-based composites for underground structures

This study aims to evaluate the performance of silica fume(SF)and nano-silica(NS)on enhancing the sulfuric acid resistance of mortar mixtures.The NS and SF were added as substitutions for cement at various dosages.The cured samples were immersed in the sulfuric acid solution with a pH of 2 for 75 d.A compressive strength test and absorption and voids tests were conducted before sulfuric acid immersion.It was found that the addition of SF and NS reduced the volume of permeable voids and increased compressive strength.A thermo-gravimetric analysis was carried out to investigate the hydration of mixtures.The mixtures with SF showed a higher level of pozzolanic reaction compared with mixtures with NS.After the 75 d of immersion,the mixtures with 5%SF and 1%NS showed the best resistance against sulfuric acid because they showed the lowest mass change and length change.

A Comparative Study on the Pozzolanic Activity between Nano-SiO_2 and Silica Fume

The pozzolanic activity of nano-SiO2 and silica fume was comparatirely stndied by X-ray diffraction （ XRD ） , differential scanning calorimetry （DSC）, scanning electron micrascopy （SEM） and the compressive , bond and bending streugths of hardened paste and concrete were also measured. Results indicate that the compressive strength development of the paste made from Ca（OH）2 and nano-SiO2, the reaction rate of Ca（ OH）2 with nano- SiO2 and the velocity of C-S-H gel formation from Ca （ OH）2 with nano-SiO2 showed marked increases over those of Ca（ OH）2 with silica fume. Furthermore, the bond strength at the interface between aggregate and hardened cement paste, and the bending strength of concrete incorporated with 3% .NS increased more than those with SF, especially at early ages. To sum up, the pozzolanic activity of nano-SiO2 was much greater than that of silica fume. The results suggest that with a small amount of nano-SiO2, the Ca（ OH）2 crystal at the interface between hardened cement paste and aggregate at early ages may be effectively absorbed in high performance concrete.

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete （SCGC） was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid （W/Gs） ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

Influence of Fly Ash and Silica Fume on Water-resistant Property of Magnesium Oxychloride Cement

By incorporation of fly ash or silica fume into magnesium oxychloride （MOC） cement, a high water resistance material can be formed for successful industrial applications. The influences of fly ash and silica fume on water-resistant property were investigated by SEM and EDS. It is found that the incorporation of fly ash or silica fume can improve the water-resistance of the MOC. The improvement of the water resistance of the MOC incorporated with fly ash or silica fume may be attributed to the alumino-silicate 5·1·8 gel or silicate 5·1·8 gel.

Analysis of the Damping Behavior and Microstructure of Cement Matrix with Silane-treated Silica Fume

The surface treatment of silca fume with silane coupling agent prior w incorporation in a cement mortar resulted in composites exhibiting increuses in loss tangent by 5%-200% and storage modulus by 10%-20% , relative to the value obtained by using as-received silica fume. The scanning electron microscopy （SEM） images iindicate that there is a morphological difference in the cement paste with treated and as-received silica fume, The, X-ray diffraction （XRD）, infrared （IR） spectrum analyses and mercury intrusion porosimetry （ MIP ） have provided evidence to understand the reaction mechanism between treated silica .fume and the hydrate product of cement. This has led to the establishment of an initial microscopic model describing the damping behavior of cement matrix.

Selective removal of heavy metal ions from aqueous solutions with surface functionalized silica nanoparticles by different functional groups

The industrial silica fume pretreated by nitric acid at 80 °C was re-used in this work. Then, the obtained silica nanoparticles were surface functionalized by silane coupling agents, such as(3-Mercaptopropyl) triethoxysilane(MPTES) and(3-Amincpropyl) trithoxysilane(APTES). Some further modifications were studied by chloroaceetyl choride and 1,8-Diaminoaphalene for amino modified silica. The surface functionalized silica nanoparticles were characterized by Fourier transform infrared(FI-IR) and X-ray photoelectron spectroscopy(XPS). The prepared adsorbent of surface functionalized silica nanoparticles with differential function groups were investigated in the selective adsorption about Pb2+, Cu2+, Hg2+, Cd2+ and Zn2+ions in aqueous solutions. The results show that the(3-Mercaptopropyl) triethoxysilane functionalized silica nanoparticles(SiO2-MPTES) play an important role in the selective adsorption of Cu2+ and Hg2+, the(3-Amincpropyl) trithoxysilane(APTES) functionalized silica nanoparticles(SiO2-APTES) exhibited maximum removal efficiency towards Pb2+ and Hg2+, the 1,8-Diaminoaphalene functionalized silica nanoparticles was excellent for removal of Hg2+ at room temperature, respectively.