Laminated elastomeric bearings used in seismic isolation rely on the mechanical properties of their constituent elastomers to ensure effective performance.However,despite their resistance to temperature fluctuations a...Laminated elastomeric bearings used in seismic isolation rely on the mechanical properties of their constituent elastomers to ensure effective performance.However,despite their resistance to temperature fluctuations and environmental aggressors,silicone elastomers exhibit relatively low stiffness,limiting their direct applicability in seismic isolation.This study investigates the effect of fumed silica as a reinforcing filler to enhance the mechanical properties of laminated silicone elastomeric bearings.Elastomeric samples were fabricated with varying fumed silica proportions and subjected to Shore A hardness,uniaxial tensile,and lap shear tests to assess the influence of filler content.Additionally,quasi-static tests were conducted on reduced-scale bearing prototypes under combined vertical compression and cyclic horizontal shear to evaluate their seismic isolation performance.The results demonstrate that fumed silica reinforcement significantly increases stiffness,as evidenced by higher Shore A hardness values.However,a trade-off was observed in tensile properties,with reductions in tensile strength and elongation at break.Despite this,the equivalent elastic modulus did not show substantial variation up to large deformations,indicating that stiffness is preserved under most working conditions.Lap shear tests showed that fumed silica improves shear resistance,while quasi-static tests revealed inelastic behavior with small increases in equivalent shear coefficients but no substantial loss in damping ratios.These findings suggest that fumed silica reinforcement enhances silicone elastomers’stiffness and shear resistance while maintaining moderate damping properties,making it a promising approach for improving the mechanical performance of elastomeric bearings in seismic isolation applications.展开更多
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 thickeni...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.展开更多
In this work, four samples containing different contents of fumed SiO_2 were prepared to improve the pore size distribution and various properties of b nucleated isotatic polypropylene（b-i PP） biaxial membrane used ...In this work, four samples containing different contents of fumed SiO_2 were prepared to improve the pore size distribution and various properties of b nucleated isotatic polypropylene（b-i PP） biaxial membrane used for lithium-ion battery separator. The wide-angle X-ray diffraction（WAXD） and differential scanning calorimetry（DSC） results show that the fumed SiO_2 promotes the formation of b-crystal slightly and narrows down the thickness distribution of b-lamellae; meanwhile, evenly distributed SiO_2 within b-i PP can be inspected by scanning electron microscopy（SEM）. Moreover, further detailed characterization of morphological evolutions during biaxial stretching by tensile testing and SEM manifests that SiO_2 can strengthen b-i PP and make the samples deform more homogeneously, resulting in a gradually elaborate and finer oriented microfibril structure after longitudinal stretching, in which more uniform defects distribute between fibrils and restrain the formation of coarse fibrils effectively. Therefore, more superior microporous structure emerges with the addition of SiO_2, accompanied by narrower pore size distribution and better connectivity between microvoids, which is confirmed by mercury porosimeter and diminished Gurley value. Moreover, the lower thermal shrinkage, decreased shrinkage rate and suppressed porosity reduction indicate that fumed SiO_2 improves thermal and dimensional stability of membrane dramatically. Furthermore, due to the excellent wettability of SiO_2 with electrolyte, the microporous membranes doped with SiO_2 have higher electrolyte uptake, even after heat treatment at elevated temperature.展开更多
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 distri...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.展开更多
Polystyrene coated silica（SiO_2@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxys...Polystyrene coated silica（SiO_2@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO_2 nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO_2@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO_2 and silane modified SiO_2 nanoparticles.Suspensions of the untreated and the silane modified SiO_2 exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO_2 at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.展开更多
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 unifo...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.展开更多
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 ...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.展开更多
Effect of the concentration ratios of organosiloxane/initiator and treatment temperature on the characteristics of hydrophobic products obtained by modification of surface of fumed silica with poly(methylphenylsiloxan...Effect of the concentration ratios of organosiloxane/initiator and treatment temperature on the characteristics of hydrophobic products obtained by modification of surface of fumed silica with poly(methylphenylsiloxane) (PMPS) in the presence of dimethyl carbonate has been studied. Morphology, particle size, surface area and coating microstructure of modified silicas were analyzed by methods of transmission electron and atomic force microscopies, nitrogen adsorption-desorption data. Carbon contents in the grafted modifying layer of organosilicas were determined using IR spectroscopy and elemental analysis. Hydrophilic-hydrophobic properties of surface of the obtained modified silicas were estimated by measurements of contact angles of wetting. It was shown that modification of pyrogenic silicas with mixtures of poly(methylphenylsiloxane) and dimethyl carbonate allows to obtain the homogeneous hydrophobic products and serve their nanodispersity.展开更多
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 rheo...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.展开更多
Rheological experiments under steady and oscillatory shear were conducted for fumed silica suspen- sions in polyethylene glycol. Under steady shear the shear-thinning and thickening response were exhibited and the flo...Rheological experiments under steady and oscillatory shear were conducted for fumed silica suspen- sions in polyethylene glycol. Under steady shear the shear-thinning and thickening response were exhibited and the flow exponent N was determined. With the increase of concentration the flow exponent N showed a rapid increase, and it increased dramatically when the discontinuous shear-thickening took place. Oscillatory shear experiments were conducted at constant frequency and constant amplitude strain, respectively. The shear-thinning and the discontinuous shear-thickening behavior were observed under different constant frequencies from 10 to 80 rad/s. The correlation between complex modulus (G*) and sweep frequency (ω) was illuminated at γ =750%. It was found that the correlation between G* and ω could be fitted by equation: G*∝ωn. The indexes in shear-thinning region and shear-thickening were determined. The indexes were similar to some extent at shear-thinning region and increased dramati- cally to a much higher value when the shear-thickening occurred,especially at higher weight fractions. The behaviors can be qualitatively explained as follows: the shear-thinning owes to decrease of viscos- ity, which results from disruption of the aggregates; the cluster theory attributes the shear-thickening to the formation of metastable, flow induced clusters, which block the system.展开更多
Lithium-ion batteries are used extensively in civil,military,and aerospace applications because of their high energy and power density.However,in practical applications,these batteries may encounter extreme cases char...Lithium-ion batteries are used extensively in civil,military,and aerospace applications because of their high energy and power density.However,in practical applications,these batteries may encounter extreme cases characterized by transient high impacts,which impose stringent requirements on their safety and reliability.In recent years,the failure mechanism associated with the short-circuiting of lithium-ion-battery separators under high dynamic impacts has been investigated thoroughly.Based on the separator impact failure mechanism,we prepared a porous polymer polyvinylidene fluoride(PVDF)separator by doping gas-phase SiO_(2)(fumed silica)additive.The gas-phase SiO_(2)has a unique three-dimensional cluster structure,which is impact resistant.The impact resistance of the battery separator was tested using a highdynamic-impact system.The voltage drop of the battery with 3%SiO_(2)content was 33.04%of that of the original PVDF battery.Material characterization of the separator was further explored by scanning electron microscope,static compression,and pore-size adsorption tests.The SiO_(2)with a special cluster structure was distributed uniformly on the surface of the separator and embedded in the inner walls of the pores.Under static compression,the current of the SiO_(2)-PVDF separator with 3%content rose at a lower rate than that of the PVDF separator,with a minimum current of 1.04 mA.After adding SiO_(2),the separator pore size increased from 5 to 20 nm.Also,we used COMSOL to conduct impact simulations of different separators.The calculation results showed that the deformation(9.98%)and internal electrode current(0.018 A)of the SiO_(2)-PVDF lithium-ion battery were lower than the deformation(23.09%)and internal electrode current(0.049 A)of the PVDF lithium-ion battery.The SiO_(2)-doped composite polymer separator with a special cluster structure plays a crucial role in enhancing the impact resistance of lithium-ion batteries.展开更多
In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calc...In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36%Zn,>99%Pb and>99%Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS,PbS and Cu 2 S,under sufficient sulfur partial pressure,low oxygen partial pressure and 400-1000℃.Sulfidation roasting experiments show that the sulfidation rate of Cu,Pb and Zn reach 81.43%,88.25% and 92.31%,respectively,under the roasting conditions of material mass ratio of 30 g:10 g,carbon dosage of 3.75 g,roasting temperature of 800℃ for 3 h.E−pH plots show that ZnS,PbS and Cu_(2)S can be enriched in the leaching residue,under leaching conditions at 25℃,pH<4 and-0.4 V<φ(E)<0.04 V.The leaching experiments showed that the sulfide is retained in the leaching residue,while the leaching rates of Cu,Pb and Zn are 1.94%,2.05% and 1.51%,respectively,under the conditions of 25℃,C_(HCl) of 0.5 mol/L,L/S of 5 mL/g,stirring rate of 300 r/min,and stirring time of 30 min.This study provides a new approach for the synergistic disposal of gypsum residue and zinc containing fume.展开更多
Soil cement bentonite(SCB)is a common material for constructing vertical cutoff walls to prevent groundwater migration at contaminated industrial sites.However,site contaminants can degrade the durability of the cutof...Soil cement bentonite(SCB)is a common material for constructing vertical cutoff walls to prevent groundwater migration at contaminated industrial sites.However,site contaminants can degrade the durability of the cutoff wall.To enhance its performance,this study developed a silica fume-SCB(SSCB).The macroscopic and microscopic properties of SSCB were assessed by unconfined compressive strength test,variable head permeability test,X-ray diffraction(XRD),scanning electron microscopy(SEM)and nuclear magnetic resonance(NMR)spectroscopy.The correlation between its multi-scale properties was analyzed based on pore characteristics.The results indicate that increasing the silica fume substitution ratio improved SSCB strength,especially in the middle and late curing stages.Moreover,increasing the substitution ratio decreased SSCB permeability coefficient,with a more pronounced effect in earlier curing stages.Silica fume addition also refined SSCB pore structure and reduced its porosity.The fractal dimension was used to quantify SSCB pore structure complexity.Increasing silica fume content reduced small pore fractal dimension in SSCB.Concurrently,SSCB strength increased and SSCB permeability coefficient decreased.The findings of this research will demonstrate the great potential of SSCB backfill for practical applications.展开更多
Development of sustainable construction materials has been the focus of research efforts worldwide in recent years.Concrete is a major construction material;hence,finding alternatives to ordinary Portland cement is of...Development of sustainable construction materials has been the focus of research efforts worldwide in recent years.Concrete is a major construction material;hence,finding alternatives to ordinary Portland cement is of extreme importance due to the high levels of carbon dioxide emissions associated with its manufacturing process.This study investigates the geopolymerization process.Specimens with,two different water/binder weight ratios,0.30 and 0.35,were monitored using acoustic emission.Results show that there is a significant difference in the acquisition data between the two different water/binder weight ratios.In addition,acoustic emission can be used to beneficially monitor and investigate the early geopolymerization process.The acoustic emission data were processed through pattern recognition.Two clusters were identified,assigned to a specific mechanism depending on their characteristics.SEM observations were coincided with pattern recognition findings.展开更多
Objectives To characterize fine particulate matter(PM_(2.5))-bound polycyclic aromatic hydrocarbons(PAHs)emitted from different cooking fumes and their exposure routes and assess their health-associated impact to prov...Objectives To characterize fine particulate matter(PM_(2.5))-bound polycyclic aromatic hydrocarbons(PAHs)emitted from different cooking fumes and their exposure routes and assess their health-associated impact to provide a reference for health risk prevention from PAH exposure across different age and sex groups.Methods Sixteen PM_(2.5)-bound PAHs emitted from 11 cooking styles were analyzed using GC-MS/MS.The health hazards of these PAHs in the Handan City population(stratified by age and sex)were predicted using the incremental lifetime cancer risk(ILCR)model.The respiratory deposition doses(RDDs)of the PAHs in children and adults were calculated using the PM_(2.5)deposition rates in the upper airway,tracheobronchial,and alveolar regions.Results The total concentrations of PM_(2.5)-bound PAHs ranged from 61.10 to 403.80 ng/m3.Regardless of cooking styles,the ILCRtotal values for adults(1.23×10^(-6)to 3.70×10^(-6))and older adults(1.28×10^(-6)to 3.88×10^(-6))exceeded the acceptable limit of 1.00×10^(-6).With increasing age,the ILCRtotal value first declined and then increased,varying substantially among the population groups.Cancer risk exhibited particularly high sensitivity to short exposure to barbecue-derived PAHs under equivalent body weights.Furthermore,barbecue,Sichuan and Hunan cuisine,Chinese cuisine,and Chinese fast food were associated with higher RDDs for both adults and children.Conclusion ILCRtotal values exceeded the acceptable limit for both females and males of adults,with all cooking styles showing a potentially high cancer risk.Our findings serve as an important reference for refining regulatory strategies related to catering emissions and mitigating health risks associated with cooking styles.展开更多
Microwave was applied to roasting the zinc oxide fume obtained from fuming furnace for the removal of F and Cl. The effects of important parameters, such as roasting temperature, holding time and stirring speed, were ...Microwave was applied to roasting the zinc oxide fume obtained from fuming furnace for the removal of F and Cl. The effects of important parameters, such as roasting temperature, holding time and stirring speed, were investigated and the process conditions were optimized using response surface methodology (RSM). The results show that the effects of roasting temperature and holding time on the removal rate of F and Cl are the most significant, and the effect of stirring speed is the second. The defluorination rate reaches 92.6% while the dechlorination rate reaches 90.2%, under the process conditions of roasting temperature of 700 °C, holding time of 80 min and stirring speed of 120 r/min. The results indicate that the removal of F and Cl from fuming furnace production of zinc oxide fumes using microwave roasting process is feasible and reliable.展开更多
Cooking fumes （CFs） are mixtures of many toxic components, such as aldehydes, heterocyclic amines, polycyclic aromatic hydrocarbons, fat aerosols and particulate matters. CFs exposure has been proven to be associate...Cooking fumes （CFs） are mixtures of many toxic components, such as aldehydes, heterocyclic amines, polycyclic aromatic hydrocarbons, fat aerosols and particulate matters. CFs exposure has been proven to be associated with many diseases. Lung cancer takes the leading place among the diseases being reported caused by CFs exposure. Molecular and biochemical studies have found that CFs exposure may lead to lung cancer by gene damage, formation of reactive oxygen species, blockage of related proteins’ function, and even cell death. However, reviews about the mechanisms of how CFs exposure leads to lung cancer are still lacking. Elucidation of the mechanisms of lung cancer caused by CFs exposure may provide a new insight into the prevention of lung cancer caused by CFs exposure, as well as laying the foundation for the toxicity study of CFs. In this minor review, the mechanisms of how CFs exposure leads to lung cancer were summarized and discussed.展开更多
The purpose of this study was to prepare the oleanolic acid–phospholipid complex (OAPC) and then solidify it employing fumed silica by simple solvent evaporation technique to improve dissolution rate of oleanolic aci...The purpose of this study was to prepare the oleanolic acid–phospholipid complex (OAPC) and then solidify it employing fumed silica by simple solvent evaporation technique to improve dissolution rate of oleanolic acid and oleanolic acid–phospholipid complex. The process of OA-PC was optimized and the type and proportion of fumed silica were studied by dissolution text. The structures of the phospholipid complex and solidified powder were also characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscope. In the dissolution tests, OA from solidified powder was further released compared with that from pure OA and OA-PC in different kinds of dissolution media. These results suggest that the method of preparing solidified powder of oleanolic acid–phospholipid complex is suitable for enhancing the dissolution rate of OA and OA-PC.展开更多
The main objective of this research is to conduct a comprehensive study for enhancing the aqueous solubility of poorly water soluble gliclazide using hydrophilic fumed silica particles (Aerosil®380) and evalu...The main objective of this research is to conduct a comprehensive study for enhancing the aqueous solubility of poorly water soluble gliclazide using hydrophilic fumed silica particles (Aerosil®380) and evaluating the influence of silica on drug release profile and pharmacological activity on alloxan induced diabetic rats. Solid dispersions (SD’s) of gliclazide were prepared using solvent evaporation method. The dissolution profiles and solid state characterization of the SD’s prepared were all evaluated. The dissolution rate of gliclazide in the SD’s with fumed silica (weight ratio, 1:1) was approximately 38%, which is about 10 fold higher than that of the pure drug after 30 min. After forming the SD’s, gliclazide changed into an amorphous state, which can infer from differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Fourier transform infrared spectroscopy (FTIR) also revealed the formation of weak hydrogen bonding through the interactions between the secondary amine groups of gliclazide and silanol groups of silica particles in the SD’s. The rapid dissolution rate from the SD’s might be attributed to the amorphization of drug, improved specific surface area and wettability than the original drug crystals. Further, we investigated the antidiabetic effects of SD’s of gliclazide in alloxan induced diabetic rats. The SD’s of gliclazide decrease the blood glucose level 64% whereas the conventional gliclazide decreases only 37% in diabetic rats. Lipid profiles, kidney and liver functions are remarkably improved in diabetic rat treated with SD’s of gliclazide than that of conventional gliclazide. These results suggest that SD’s of gliclazide have much more bioavailability and hence are more pharmacologically active than that of conventional gliclazide form.展开更多
文摘Laminated elastomeric bearings used in seismic isolation rely on the mechanical properties of their constituent elastomers to ensure effective performance.However,despite their resistance to temperature fluctuations and environmental aggressors,silicone elastomers exhibit relatively low stiffness,limiting their direct applicability in seismic isolation.This study investigates the effect of fumed silica as a reinforcing filler to enhance the mechanical properties of laminated silicone elastomeric bearings.Elastomeric samples were fabricated with varying fumed silica proportions and subjected to Shore A hardness,uniaxial tensile,and lap shear tests to assess the influence of filler content.Additionally,quasi-static tests were conducted on reduced-scale bearing prototypes under combined vertical compression and cyclic horizontal shear to evaluate their seismic isolation performance.The results demonstrate that fumed silica reinforcement significantly increases stiffness,as evidenced by higher Shore A hardness values.However,a trade-off was observed in tensile properties,with reductions in tensile strength and elongation at break.Despite this,the equivalent elastic modulus did not show substantial variation up to large deformations,indicating that stiffness is preserved under most working conditions.Lap shear tests showed that fumed silica improves shear resistance,while quasi-static tests revealed inelastic behavior with small increases in equivalent shear coefficients but no substantial loss in damping ratios.These findings suggest that fumed silica reinforcement enhances silicone elastomers’stiffness and shear resistance while maintaining moderate damping properties,making it a promising approach for improving the mechanical performance of elastomeric bearings in seismic isolation applications.
文摘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.
基金financially supported by the National Natural Science Foundation of China (No. 51421061)
文摘In this work, four samples containing different contents of fumed SiO_2 were prepared to improve the pore size distribution and various properties of b nucleated isotatic polypropylene（b-i PP） biaxial membrane used for lithium-ion battery separator. The wide-angle X-ray diffraction（WAXD） and differential scanning calorimetry（DSC） results show that the fumed SiO_2 promotes the formation of b-crystal slightly and narrows down the thickness distribution of b-lamellae; meanwhile, evenly distributed SiO_2 within b-i PP can be inspected by scanning electron microscopy（SEM）. Moreover, further detailed characterization of morphological evolutions during biaxial stretching by tensile testing and SEM manifests that SiO_2 can strengthen b-i PP and make the samples deform more homogeneously, resulting in a gradually elaborate and finer oriented microfibril structure after longitudinal stretching, in which more uniform defects distribute between fibrils and restrain the formation of coarse fibrils effectively. Therefore, more superior microporous structure emerges with the addition of SiO_2, accompanied by narrower pore size distribution and better connectivity between microvoids, which is confirmed by mercury porosimeter and diminished Gurley value. Moreover, the lower thermal shrinkage, decreased shrinkage rate and suppressed porosity reduction indicate that fumed SiO_2 improves thermal and dimensional stability of membrane dramatically. Furthermore, due to the excellent wettability of SiO_2 with electrolyte, the microporous membranes doped with SiO_2 have higher electrolyte uptake, even after heat treatment at elevated temperature.
基金the National Natural Science Foundation of China(No.51803130)China Postdoctoral Science Foundation(No.2018M640915)+1 种基金Sichuan Science and Technology Program(No.2019JDRC010)Fundamental Research Funds for Central Universities.
文摘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.
基金supported by the National Natural Science Foundation of China(No.51073136)the Fundamental Research Funds for the Central Universities of China(No.2010QNA4011)
文摘Polystyrene coated silica（SiO_2@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO_2 nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO_2@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO_2 and silane modified SiO_2 nanoparticles.Suspensions of the untreated and the silane modified SiO_2 exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO_2 at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.
基金Supported by National Science Fund for Talent Training in Basic Science ( J0830310)the Fundamental Research Funds for the Central Universities (017)
文摘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.
基金supported by the National Research Fund for Fundamental Key Projects(No.2010CB934700)the National Natural Science Foundation of China(No.51003004)the Fundamental Research Funds for the Central Universities
文摘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.
文摘Effect of the concentration ratios of organosiloxane/initiator and treatment temperature on the characteristics of hydrophobic products obtained by modification of surface of fumed silica with poly(methylphenylsiloxane) (PMPS) in the presence of dimethyl carbonate has been studied. Morphology, particle size, surface area and coating microstructure of modified silicas were analyzed by methods of transmission electron and atomic force microscopies, nitrogen adsorption-desorption data. Carbon contents in the grafted modifying layer of organosilicas were determined using IR spectroscopy and elemental analysis. Hydrophilic-hydrophobic properties of surface of the obtained modified silicas were estimated by measurements of contact angles of wetting. It was shown that modification of pyrogenic silicas with mixtures of poly(methylphenylsiloxane) and dimethyl carbonate allows to obtain the homogeneous hydrophobic products and serve their nanodispersity.
基金the Grant Agency CR for the financial support of Grant Project(No.17-26808S)the support of the Ministry of Education,Youth and Sports of the Czech Republic-Programme NPU I(No.LO1504)
文摘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.
基金Supported by the National Natural Science Foundation of China (Grant No. 50774096, 50604017)
文摘Rheological experiments under steady and oscillatory shear were conducted for fumed silica suspen- sions in polyethylene glycol. Under steady shear the shear-thinning and thickening response were exhibited and the flow exponent N was determined. With the increase of concentration the flow exponent N showed a rapid increase, and it increased dramatically when the discontinuous shear-thickening took place. Oscillatory shear experiments were conducted at constant frequency and constant amplitude strain, respectively. The shear-thinning and the discontinuous shear-thickening behavior were observed under different constant frequencies from 10 to 80 rad/s. The correlation between complex modulus (G*) and sweep frequency (ω) was illuminated at γ =750%. It was found that the correlation between G* and ω could be fitted by equation: G*∝ωn. The indexes in shear-thinning region and shear-thickening were determined. The indexes were similar to some extent at shear-thinning region and increased dramati- cally to a much higher value when the shear-thickening occurred,especially at higher weight fractions. The behaviors can be qualitatively explained as follows: the shear-thinning owes to decrease of viscos- ity, which results from disruption of the aggregates; the cluster theory attributes the shear-thickening to the formation of metastable, flow induced clusters, which block the system.
基金supported by the Young Elite Scientists Sponsorship Program by CAST(Grant No.2023QNRC001).
文摘Lithium-ion batteries are used extensively in civil,military,and aerospace applications because of their high energy and power density.However,in practical applications,these batteries may encounter extreme cases characterized by transient high impacts,which impose stringent requirements on their safety and reliability.In recent years,the failure mechanism associated with the short-circuiting of lithium-ion-battery separators under high dynamic impacts has been investigated thoroughly.Based on the separator impact failure mechanism,we prepared a porous polymer polyvinylidene fluoride(PVDF)separator by doping gas-phase SiO_(2)(fumed silica)additive.The gas-phase SiO_(2)has a unique three-dimensional cluster structure,which is impact resistant.The impact resistance of the battery separator was tested using a highdynamic-impact system.The voltage drop of the battery with 3%SiO_(2)content was 33.04%of that of the original PVDF battery.Material characterization of the separator was further explored by scanning electron microscope,static compression,and pore-size adsorption tests.The SiO_(2)with a special cluster structure was distributed uniformly on the surface of the separator and embedded in the inner walls of the pores.Under static compression,the current of the SiO_(2)-PVDF separator with 3%content rose at a lower rate than that of the PVDF separator,with a minimum current of 1.04 mA.After adding SiO_(2),the separator pore size increased from 5 to 20 nm.Also,we used COMSOL to conduct impact simulations of different separators.The calculation results showed that the deformation(9.98%)and internal electrode current(0.018 A)of the SiO_(2)-PVDF lithium-ion battery were lower than the deformation(23.09%)and internal electrode current(0.049 A)of the PVDF lithium-ion battery.The SiO_(2)-doped composite polymer separator with a special cluster structure plays a crucial role in enhancing the impact resistance of lithium-ion batteries.
基金Projects(52174269,52374293)supported by the National Natural Science Foundation of ChinaProject(2022RC1123)supported by the Science and Technology Innovation Program of Hunan Province,China。
文摘In this study,a synergistic sulfidation-acid leaching process was proposed to recover valuable metals from gypsum residue and zinc-containing fume.The equilibrium phase composition of the sulfidation reaction and calculations of the thermodynamic stability region show that 89.36%Zn,>99%Pb and>99%Cu of gypsum residue and zinc-containing fume can be sulfured to ZnS,PbS and Cu 2 S,under sufficient sulfur partial pressure,low oxygen partial pressure and 400-1000℃.Sulfidation roasting experiments show that the sulfidation rate of Cu,Pb and Zn reach 81.43%,88.25% and 92.31%,respectively,under the roasting conditions of material mass ratio of 30 g:10 g,carbon dosage of 3.75 g,roasting temperature of 800℃ for 3 h.E−pH plots show that ZnS,PbS and Cu_(2)S can be enriched in the leaching residue,under leaching conditions at 25℃,pH<4 and-0.4 V<φ(E)<0.04 V.The leaching experiments showed that the sulfide is retained in the leaching residue,while the leaching rates of Cu,Pb and Zn are 1.94%,2.05% and 1.51%,respectively,under the conditions of 25℃,C_(HCl) of 0.5 mol/L,L/S of 5 mL/g,stirring rate of 300 r/min,and stirring time of 30 min.This study provides a new approach for the synergistic disposal of gypsum residue and zinc containing fume.
基金Project(2019YFC1803601)supported by the National Key Research and Development Program of ChinaProject(52274182)supported by the National Natural Science Foundation of China+1 种基金Project(2021zzts0274)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(CX20210295)supported by the Postgraduate Scientific Research Innovation Project of Hunan Province,China。
文摘Soil cement bentonite(SCB)is a common material for constructing vertical cutoff walls to prevent groundwater migration at contaminated industrial sites.However,site contaminants can degrade the durability of the cutoff wall.To enhance its performance,this study developed a silica fume-SCB(SSCB).The macroscopic and microscopic properties of SSCB were assessed by unconfined compressive strength test,variable head permeability test,X-ray diffraction(XRD),scanning electron microscopy(SEM)and nuclear magnetic resonance(NMR)spectroscopy.The correlation between its multi-scale properties was analyzed based on pore characteristics.The results indicate that increasing the silica fume substitution ratio improved SSCB strength,especially in the middle and late curing stages.Moreover,increasing the substitution ratio decreased SSCB permeability coefficient,with a more pronounced effect in earlier curing stages.Silica fume addition also refined SSCB pore structure and reduced its porosity.The fractal dimension was used to quantify SSCB pore structure complexity.Increasing silica fume content reduced small pore fractal dimension in SSCB.Concurrently,SSCB strength increased and SSCB permeability coefficient decreased.The findings of this research will demonstrate the great potential of SSCB backfill for practical applications.
基金supported by the U.S.Department of Energy Office of Science,Office of Basic Energy Sciences,and Office of Biological and Environmental Research under Award Number DE-SC-00012530.
文摘Development of sustainable construction materials has been the focus of research efforts worldwide in recent years.Concrete is a major construction material;hence,finding alternatives to ordinary Portland cement is of extreme importance due to the high levels of carbon dioxide emissions associated with its manufacturing process.This study investigates the geopolymerization process.Specimens with,two different water/binder weight ratios,0.30 and 0.35,were monitored using acoustic emission.Results show that there is a significant difference in the acquisition data between the two different water/binder weight ratios.In addition,acoustic emission can be used to beneficially monitor and investigate the early geopolymerization process.The acoustic emission data were processed through pattern recognition.Two clusters were identified,assigned to a specific mechanism depending on their characteristics.SEM observations were coincided with pattern recognition findings.
基金supported by the National Natural Science Foundation of China(No.52330002)the Natural Science Foundation of Beijing Municipality(No.8232020)the First Batch of Key Disciplines on Public Health in Chongqing(YWBF2022072).
文摘Objectives To characterize fine particulate matter(PM_(2.5))-bound polycyclic aromatic hydrocarbons(PAHs)emitted from different cooking fumes and their exposure routes and assess their health-associated impact to provide a reference for health risk prevention from PAH exposure across different age and sex groups.Methods Sixteen PM_(2.5)-bound PAHs emitted from 11 cooking styles were analyzed using GC-MS/MS.The health hazards of these PAHs in the Handan City population(stratified by age and sex)were predicted using the incremental lifetime cancer risk(ILCR)model.The respiratory deposition doses(RDDs)of the PAHs in children and adults were calculated using the PM_(2.5)deposition rates in the upper airway,tracheobronchial,and alveolar regions.Results The total concentrations of PM_(2.5)-bound PAHs ranged from 61.10 to 403.80 ng/m3.Regardless of cooking styles,the ILCRtotal values for adults(1.23×10^(-6)to 3.70×10^(-6))and older adults(1.28×10^(-6)to 3.88×10^(-6))exceeded the acceptable limit of 1.00×10^(-6).With increasing age,the ILCRtotal value first declined and then increased,varying substantially among the population groups.Cancer risk exhibited particularly high sensitivity to short exposure to barbecue-derived PAHs under equivalent body weights.Furthermore,barbecue,Sichuan and Hunan cuisine,Chinese cuisine,and Chinese fast food were associated with higher RDDs for both adults and children.Conclusion ILCRtotal values exceeded the acceptable limit for both females and males of adults,with all cooking styles showing a potentially high cancer risk.Our findings serve as an important reference for refining regulatory strategies related to catering emissions and mitigating health risks associated with cooking styles.
基金Project(51104073)supported by the National Natural Science Foundation of ChinaProject(2013AA064003)supported by the High-tech Research and Development Program of China+1 种基金Project(2014CB643404)supported by the National Basic Research Program of ChinaProject(2012HB008)supported by Yunnan Province Young Academic Technology Leader Reserve Talents,China
文摘Microwave was applied to roasting the zinc oxide fume obtained from fuming furnace for the removal of F and Cl. The effects of important parameters, such as roasting temperature, holding time and stirring speed, were investigated and the process conditions were optimized using response surface methodology (RSM). The results show that the effects of roasting temperature and holding time on the removal rate of F and Cl are the most significant, and the effect of stirring speed is the second. The defluorination rate reaches 92.6% while the dechlorination rate reaches 90.2%, under the process conditions of roasting temperature of 700 °C, holding time of 80 min and stirring speed of 120 r/min. The results indicate that the removal of F and Cl from fuming furnace production of zinc oxide fumes using microwave roasting process is feasible and reliable.
基金Supported by the Development Project of Community Health Nursing Innovative Practice Model of China(CMB08883)
文摘Cooking fumes （CFs） are mixtures of many toxic components, such as aldehydes, heterocyclic amines, polycyclic aromatic hydrocarbons, fat aerosols and particulate matters. CFs exposure has been proven to be associated with many diseases. Lung cancer takes the leading place among the diseases being reported caused by CFs exposure. Molecular and biochemical studies have found that CFs exposure may lead to lung cancer by gene damage, formation of reactive oxygen species, blockage of related proteins’ function, and even cell death. However, reviews about the mechanisms of how CFs exposure leads to lung cancer are still lacking. Elucidation of the mechanisms of lung cancer caused by CFs exposure may provide a new insight into the prevention of lung cancer caused by CFs exposure, as well as laying the foundation for the toxicity study of CFs. In this minor review, the mechanisms of how CFs exposure leads to lung cancer were summarized and discussed.
文摘The purpose of this study was to prepare the oleanolic acid–phospholipid complex (OAPC) and then solidify it employing fumed silica by simple solvent evaporation technique to improve dissolution rate of oleanolic acid and oleanolic acid–phospholipid complex. The process of OA-PC was optimized and the type and proportion of fumed silica were studied by dissolution text. The structures of the phospholipid complex and solidified powder were also characterized by differential scanning calorimetry, X-ray diffraction, and scanning electron microscope. In the dissolution tests, OA from solidified powder was further released compared with that from pure OA and OA-PC in different kinds of dissolution media. These results suggest that the method of preparing solidified powder of oleanolic acid–phospholipid complex is suitable for enhancing the dissolution rate of OA and OA-PC.
文摘The main objective of this research is to conduct a comprehensive study for enhancing the aqueous solubility of poorly water soluble gliclazide using hydrophilic fumed silica particles (Aerosil®380) and evaluating the influence of silica on drug release profile and pharmacological activity on alloxan induced diabetic rats. Solid dispersions (SD’s) of gliclazide were prepared using solvent evaporation method. The dissolution profiles and solid state characterization of the SD’s prepared were all evaluated. The dissolution rate of gliclazide in the SD’s with fumed silica (weight ratio, 1:1) was approximately 38%, which is about 10 fold higher than that of the pure drug after 30 min. After forming the SD’s, gliclazide changed into an amorphous state, which can infer from differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Fourier transform infrared spectroscopy (FTIR) also revealed the formation of weak hydrogen bonding through the interactions between the secondary amine groups of gliclazide and silanol groups of silica particles in the SD’s. The rapid dissolution rate from the SD’s might be attributed to the amorphization of drug, improved specific surface area and wettability than the original drug crystals. Further, we investigated the antidiabetic effects of SD’s of gliclazide in alloxan induced diabetic rats. The SD’s of gliclazide decrease the blood glucose level 64% whereas the conventional gliclazide decreases only 37% in diabetic rats. Lipid profiles, kidney and liver functions are remarkably improved in diabetic rat treated with SD’s of gliclazide than that of conventional gliclazide. These results suggest that SD’s of gliclazide have much more bioavailability and hence are more pharmacologically active than that of conventional gliclazide form.
