This study focused on the development and characterization of TiO<sub>2</sub>-PES composite fibers with varying TiO<sub>2</sub> loading amounts using a phase inversion process. The resulting co...This study focused on the development and characterization of TiO<sub>2</sub>-PES composite fibers with varying TiO<sub>2</sub> loading amounts using a phase inversion process. The resulting composite fibers exhibited a sponge-like structure with embedded TiO<sub>2</sub> nanoparticles within a polymer matrix. Their photocatalytic performance for ammonia removal from aqueous solutions under UV-A light exposure was thoroughly investigated. The findings revealed that PeTi8 composite fibers displayed superior adsorption capacity compared to other samples. Moreover, the study explored the impact of pH, light intensity, and catalyst dosage on the photocatalytic degradation of ammonia. Adsorption equilibrium isotherms closely followed the Langmuir model, with the results indicating a correlation between qm values of 2.49 mg/g and the porous structure of the adsorbents. The research underscored the efficacy of TiO<sub>2</sub> composite fibers in the photocatalytic removal of aqueous under UV-A light. Notably, increasing the distance between the photocatalyst and the light source resulted in de-creased hydroxyl radical concentration, influencing photocatalytic efficiency. These findings contribute to our understanding of TiO<sub>2</sub> composite fibers as promising photocatalysts for ammonia removal in water treatment applications.展开更多
Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Al...Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.展开更多
An ambient pressure synthesis of SiO2/TiO2 binary aerogel was prepared through the low-cost precursors of titanium tetrachloride（TiCl4） and sodium silicate（Na2O·nSiO2）.After gelation,solvent exchange and surf...An ambient pressure synthesis of SiO2/TiO2 binary aerogel was prepared through the low-cost precursors of titanium tetrachloride（TiCl4） and sodium silicate（Na2O·nSiO2）.After gelation,solvent exchange and surface modification were performed simultaneously and the modified gel was finally dried under ambient pressure.Microstructural analyses by transmission electron microscope（TEM） indicate that fabricated SiO2/TiO2 aerogel composite shows similar sponge-like nanostructure as silica aerogel,and the Brunauer-EmmettTeller（BET） analysis shows that the specific surface area of the composite reaches 605 m^2/g,and the average pore size is 9.7 nm.Such binary aerogel exhibits significant photocatalytic performance in this paper for treating model pollutant of methyl orange（MO）,and the decolorizing efficiency of MO is detected as 84.9%after 210 mins exposure to UV light irradiation.Degraded gel suspends in the water so as to separate from solution for reuse,and after 4 times recycling,70%degradation efficiency can be easily reached when composite catalyzed system is exposed for 210 mins under UV irradiation.展开更多
The uniform transparent TiO2/SiO2 photocatalytic composite thin films are prepared by sol-gel method on the soda lime glass substrates, and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), transmissi...The uniform transparent TiO2/SiO2 photocatalytic composite thin films are prepared by sol-gel method on the soda lime glass substrates, and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), BET surface area, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that the addition of SiO2 to TiO2 thin films can suppress the grain growth of TiO2 crystal, increase the hydroxyl content on the surface of TiO2 films, lower the contact angle for water on TiO, films and enhance the hydrophilic property of TiO2 films. The super-hydrophilic TiO2/SiO2 photocatalytic composite thin films with the contact angle of 0((o) under bar) are obtained by the addition of 10%-20% SiO2 in mole fraction.展开更多
Hollow B–SiO2@TiO2 composites were prepared by the wet chemical deposition method starting from TiCl4 and hollow B–SiO2 microspheres.TiO2 layers composed of anatase TiO2 nanoparticles were coated on the surfaces of ...Hollow B–SiO2@TiO2 composites were prepared by the wet chemical deposition method starting from TiCl4 and hollow B–SiO2 microspheres.TiO2 layers composed of anatase TiO2 nanoparticles were coated on the surfaces of the hollow B–SiO2 microspheres probably through the formation of Ti—O—Si and Ti—O—B bonds.A great number of—OH groups were also present at the TiO2 coating layers.The presence of Ti—O—Si bonds and Ti—O—B bonds resulted in the formation of defects in the TiO2 coating layers,which decreased the band gap of the TiO2 coating layers to ca.3.0 eV and endowed the TiO2 coating layers with visible light absorption performance.The buoyancy hollow B–SiO2@TiO2 composites exhibited high photocatalytic activities for the degradation of ammonia-nitrogen and green algae.The conversion of ammonia-nitrogen reached 65%when the degradation of ammonia-nitrogen(43 mg·L-1 at pH value of 8)was catalyzed by the B–SiO2@TiO2(100:10)composite under the simulated solar light irradiation at 35°C for 660 min.The green algae(5 mg·L-1)were almost completely degraded over the B–SiO@TiO2(100:20)photocatalyst under the visible light irradiation at 35°C for 510 min.展开更多
A NiP/TiO2 composite film on carbon steel was prepared by electroless plating and sol-gel composite process. An artificial neural network was applied to optimize the prepared condition of the composite film. Corrosion...A NiP/TiO2 composite film on carbon steel was prepared by electroless plating and sol-gel composite process. An artificial neural network was applied to optimize the prepared condition of the composite film. Corrosion behavior of the NiP/TiO2 composite film was investigated by polarization resistance measurement, anode polarization, ESEM （environmental scanning electron microscopy） and EIS （electrochemical impedance spectroscopy） measurements. Results showed that the NiP/ TiO2 composite film has a good corrosion resistance in 0.5mol/L H2SO4 solution. The element valence of the composite film was characterized by XPS （X-ray photoelectron spectroscopy） spectrum, and an anticorrosion mechanism of the composite film was discussed.展开更多
A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process ...A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra （EDS） result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction （XRD） results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope （SEM）. As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.展开更多
Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships amon...Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships among the important electrical parameters of the samples with different thickness SiO2-Si3N4 films,such as threshold voltage,breakdown voltage,and on-state resistance in accumulated dose,are discussed.The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose.However,the relationships between the threshold voltages of the samples and the accumulated dose are more complex,and not only positively drift,but also negatively drift.At the end of the total dose experiment,we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies.We find that the samples with appropriate thickness ratio SiO2-Si3N4 films have a good radiation-hardening ability.This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2-Si3N4 films.展开更多
The micro/nano-scale indentation tests were performed to explore the performance of bisphenol-α-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin composites. The effect of the fi...The micro/nano-scale indentation tests were performed to explore the performance of bisphenol-α-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin composites. The effect of the filling content of nano-SiO2 particles on the mechanical properties of the dental composites was studied as well. The experimental results showed that the incorporation of the nano-SiO2 particles at low concentrations (up to 10 wt.%) can apparently increase the hardness and elastic modulus of the dental rein composites. The plasticity index indicates a best elastic recovery capability at a proper amount (4 wt.%) of the nanoparticles. Combined with the infrared spectrum, the mechanical enhancement mechanisms of the dental resin composites were analyzed.展开更多
Three-dimensional （3D） five-directional braided （SiO2）/SiO2 composites were prepared by silicasol-infiltration-sintering （SIS） method. The flexural properties and microstructures were studied. The flexural stren...Three-dimensional （3D） five-directional braided （SiO2）/SiO2 composites were prepared by silicasol-infiltration-sintering （SIS） method. The flexural properties and microstructures were studied. The flexural strength and flexural elastic modulus were found to be 73 MPa and 12 GPa, respectively. The results of stress vs deflection curve and SEM examinations revealed that the fracture mechanism of 3D, five-directional braided （SiO2）/SiO2 composite was a mixture mode of ductile and brittle. The ductile mode was attributed to the weak bonding strength of fiber/matrix at low temperature. The brittle fracture might be caused by the propagation of micro defect or crack, which existed in the as-prepared composites for the ten-cycle process.展开更多
Silica( SiO_2) based aerogel/xerogel materials have been received ever-growing attentions for versatile applications. However,the widespread applications are narrowed by the inert properties,fragile and brittle nature...Silica( SiO_2) based aerogel/xerogel materials have been received ever-growing attentions for versatile applications. However,the widespread applications are narrowed by the inert properties,fragile and brittle natureof silica materials and cumbersome preparation processes. In this paper,titania( TiO_2) was introduced into SiO_2 matrix to form photocatalytic hybrid gels. The TiO_2/SiO_2 composites were then reinforced by the impregnation of various fibrillary reinforcements,such as glass,mullite mineral and ceramic fibers. The properties of the composites were studied systematically in terms of fiberstability,microstructure,chemical interaction and thermal conductivity. The final xerogel composites displayed improved monolithic geometry,satisfied thermal conductivity(0. 09-0. 25 W·m^(-1)·K^(-1)) and optimized photocatalytic performance(85% removal of model pollutant of methyl orange( Mo)),which could be expected to be a feasible route to multi-functional building facades in the future.展开更多
Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liqu...Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liquid silicon infiltration（LSI） process.The results indicated that C/C-SiC composites present a better ablation resistance than C/C composites without doped SiC.The doped SiC and the ablation products SiO2 derived from it play key roles in ablation process.Bulk quantities of SiO2 nanowires with diameter of 80 nm-150 nm and length of tens microns were observed on the surface of specimens after ablation.The growth mechanism of the SiO_2 nanowires was interpreted with a developed vapor-liquid-solid（VLS） driven by the temperature gradient.展开更多
文摘This study focused on the development and characterization of TiO<sub>2</sub>-PES composite fibers with varying TiO<sub>2</sub> loading amounts using a phase inversion process. The resulting composite fibers exhibited a sponge-like structure with embedded TiO<sub>2</sub> nanoparticles within a polymer matrix. Their photocatalytic performance for ammonia removal from aqueous solutions under UV-A light exposure was thoroughly investigated. The findings revealed that PeTi8 composite fibers displayed superior adsorption capacity compared to other samples. Moreover, the study explored the impact of pH, light intensity, and catalyst dosage on the photocatalytic degradation of ammonia. Adsorption equilibrium isotherms closely followed the Langmuir model, with the results indicating a correlation between qm values of 2.49 mg/g and the porous structure of the adsorbents. The research underscored the efficacy of TiO<sub>2</sub> composite fibers in the photocatalytic removal of aqueous under UV-A light. Notably, increasing the distance between the photocatalyst and the light source resulted in de-creased hydroxyl radical concentration, influencing photocatalytic efficiency. These findings contribute to our understanding of TiO<sub>2</sub> composite fibers as promising photocatalysts for ammonia removal in water treatment applications.
文摘Al_(2)O_(3)–SiO_(2)sols were synthesized by using aluminum chloride hex hydrate and tetraethoxysilane(TEOS)as precursors,deionized water and ethanol mixture as the solvent,and propylene oxide as the coagulant aids.Alumina coatings were prepared on the surfaces of hollow quartz filament fiber,then a new lightweight and thermal insulating material were successfully prepared by impregnatingAl_(2)O_(3)–SiO_(2)sol into a needle fabric made by coated hollow quartz filament fiber.The coated quartz fiber,aerogels and composites were characterized by Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),energy dispersive spectroscopy(EDS),nitrogen adsorption-desorption(BET),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and tensile tests.The effects of different fiber and calcination temperatures on the microstructures and properties ofAl_(2)O_(3)–SiO_(2)composite aerogels were investigated.The test results indicate that the mechanical properties of the aerogels are improved by introducing quartz filament fabrics and the introduction of alumina coating improves the thermal stability of the material.Compared to other fibers,Al_(2)O_(3)-coated hollow quartz fiber has significant advantages as reinforcement for composite,and their tensile strength is well retained after high temperature heat treatment.
基金Funded by the National Natural Science Foundation of China(NSFC)(Nos.51278073,51308079 and 51408073)
文摘An ambient pressure synthesis of SiO2/TiO2 binary aerogel was prepared through the low-cost precursors of titanium tetrachloride（TiCl4） and sodium silicate（Na2O·nSiO2）.After gelation,solvent exchange and surface modification were performed simultaneously and the modified gel was finally dried under ambient pressure.Microstructural analyses by transmission electron microscope（TEM） indicate that fabricated SiO2/TiO2 aerogel composite shows similar sponge-like nanostructure as silica aerogel,and the Brunauer-EmmettTeller（BET） analysis shows that the specific surface area of the composite reaches 605 m^2/g,and the average pore size is 9.7 nm.Such binary aerogel exhibits significant photocatalytic performance in this paper for treating model pollutant of methyl orange（MO）,and the decolorizing efficiency of MO is detected as 84.9%after 210 mins exposure to UV light irradiation.Degraded gel suspends in the water so as to separate from solution for reuse,and after 4 times recycling,70%degradation efficiency can be easily reached when composite catalyzed system is exposed for 210 mins under UV irradiation.
基金This work was financially supported by the Foundation for University Key Teachers by the Ministry of Education, theKey Resear
文摘The uniform transparent TiO2/SiO2 photocatalytic composite thin films are prepared by sol-gel method on the soda lime glass substrates, and characterized by UV-visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), BET surface area, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS). It was found that the addition of SiO2 to TiO2 thin films can suppress the grain growth of TiO2 crystal, increase the hydroxyl content on the surface of TiO2 films, lower the contact angle for water on TiO, films and enhance the hydrophilic property of TiO2 films. The super-hydrophilic TiO2/SiO2 photocatalytic composite thin films with the contact angle of 0((o) under bar) are obtained by the addition of 10%-20% SiO2 in mole fraction.
基金Supported by the National Natural Science Foundation of China(21506078).
文摘Hollow B–SiO2@TiO2 composites were prepared by the wet chemical deposition method starting from TiCl4 and hollow B–SiO2 microspheres.TiO2 layers composed of anatase TiO2 nanoparticles were coated on the surfaces of the hollow B–SiO2 microspheres probably through the formation of Ti—O—Si and Ti—O—B bonds.A great number of—OH groups were also present at the TiO2 coating layers.The presence of Ti—O—Si bonds and Ti—O—B bonds resulted in the formation of defects in the TiO2 coating layers,which decreased the band gap of the TiO2 coating layers to ca.3.0 eV and endowed the TiO2 coating layers with visible light absorption performance.The buoyancy hollow B–SiO2@TiO2 composites exhibited high photocatalytic activities for the degradation of ammonia-nitrogen and green algae.The conversion of ammonia-nitrogen reached 65%when the degradation of ammonia-nitrogen(43 mg·L-1 at pH value of 8)was catalyzed by the B–SiO2@TiO2(100:10)composite under the simulated solar light irradiation at 35°C for 660 min.The green algae(5 mg·L-1)were almost completely degraded over the B–SiO@TiO2(100:20)photocatalyst under the visible light irradiation at 35°C for 510 min.
文摘A NiP/TiO2 composite film on carbon steel was prepared by electroless plating and sol-gel composite process. An artificial neural network was applied to optimize the prepared condition of the composite film. Corrosion behavior of the NiP/TiO2 composite film was investigated by polarization resistance measurement, anode polarization, ESEM （environmental scanning electron microscopy） and EIS （electrochemical impedance spectroscopy） measurements. Results showed that the NiP/ TiO2 composite film has a good corrosion resistance in 0.5mol/L H2SO4 solution. The element valence of the composite film was characterized by XPS （X-ray photoelectron spectroscopy） spectrum, and an anticorrosion mechanism of the composite film was discussed.
基金This study was financially supported by the Key Foundation of National Science in China (No. 90405015), the National Elitist Youth Foundation of China (No. 50425208the Doctorate Foundation of Northwestern Polytechnical University (CX200505).
文摘A silicon dioxide fiber-reinforced silicon nitride matrix （SiOJSi3N4） composite used for radomes was prepared by chemical vapor infiltration （CVI） process using the SiCl4-NH3-H2 system. The effects of the process conditions, including infiltration temperature, infiltration time, and gas flux were investigated. The energy dispersion spectra （EDS） result showed that the main elements of this composite contained Si, N, and O. The X-ray diffraction （XRD） results indicated that phases of the composite before and after treatment at 1350℃ were all amorphous. A little fiber pull-out was observed on the cross section of the composite by scan electron microscope （SEM）. As a result, the composite exhibited good thermal stability, but an appropriate interface was necessary between the fiber and the matrix.
文摘Total dose effects and single event effects on radiation-hardened power vertical double-diffusion metal oxide semiconductor（VDMOS） devices with composite SiO2-Si3N4 film gates are investigated.The relationships among the important electrical parameters of the samples with different thickness SiO2-Si3N4 films,such as threshold voltage,breakdown voltage,and on-state resistance in accumulated dose,are discussed.The total dose experiment results show that the breakdown voltage and the on-state resistance barely change with the accumulated dose.However,the relationships between the threshold voltages of the samples and the accumulated dose are more complex,and not only positively drift,but also negatively drift.At the end of the total dose experiment,we select the group of samples which have the smaller threshold voltage shift to carry out the single event effect studies.We find that the samples with appropriate thickness ratio SiO2-Si3N4 films have a good radiation-hardening ability.This method may be useful in solving both the SEGR and the total dose problems with the composite SiO2-Si3N4 films.
文摘The micro/nano-scale indentation tests were performed to explore the performance of bisphenol-α-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) dental resin composites. The effect of the filling content of nano-SiO2 particles on the mechanical properties of the dental composites was studied as well. The experimental results showed that the incorporation of the nano-SiO2 particles at low concentrations (up to 10 wt.%) can apparently increase the hardness and elastic modulus of the dental rein composites. The plasticity index indicates a best elastic recovery capability at a proper amount (4 wt.%) of the nanoparticles. Combined with the infrared spectrum, the mechanical enhancement mechanisms of the dental resin composites were analyzed.
基金Funded by the Basic Research Project of Science and Technology of Jiangsu Province(No.BK2009002)the National Natural ScienceFoundation of China(No.61176062)the Fundamental Research Funds for the Central Universities(No.NS2013061)
文摘Three-dimensional （3D） five-directional braided （SiO2）/SiO2 composites were prepared by silicasol-infiltration-sintering （SIS） method. The flexural properties and microstructures were studied. The flexural strength and flexural elastic modulus were found to be 73 MPa and 12 GPa, respectively. The results of stress vs deflection curve and SEM examinations revealed that the fracture mechanism of 3D, five-directional braided （SiO2）/SiO2 composite was a mixture mode of ductile and brittle. The ductile mode was attributed to the weak bonding strength of fiber/matrix at low temperature. The brittle fracture might be caused by the propagation of micro defect or crack, which existed in the as-prepared composites for the ten-cycle process.
基金National Natural Science Foundations of China(Nos.51308079,51408073,51678080,51678081)
文摘Silica( SiO_2) based aerogel/xerogel materials have been received ever-growing attentions for versatile applications. However,the widespread applications are narrowed by the inert properties,fragile and brittle natureof silica materials and cumbersome preparation processes. In this paper,titania( TiO_2) was introduced into SiO_2 matrix to form photocatalytic hybrid gels. The TiO_2/SiO_2 composites were then reinforced by the impregnation of various fibrillary reinforcements,such as glass,mullite mineral and ceramic fibers. The properties of the composites were studied systematically in terms of fiberstability,microstructure,chemical interaction and thermal conductivity. The final xerogel composites displayed improved monolithic geometry,satisfied thermal conductivity(0. 09-0. 25 W·m^(-1)·K^(-1)) and optimized photocatalytic performance(85% removal of model pollutant of methyl orange( Mo)),which could be expected to be a feasible route to multi-functional building facades in the future.
基金supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110006110025)the National Natural Science Foundation of China(Grant No.U1134102)
文摘Ablation under oxyacetylene torch with heat flux of 4186.8（10%kW/m2 for 20 s was performed to evaluate the ablation resistance of C/C-SiC composites fabricated by chemical vapor infiltration（CVI） combined with liquid silicon infiltration（LSI） process.The results indicated that C/C-SiC composites present a better ablation resistance than C/C composites without doped SiC.The doped SiC and the ablation products SiO2 derived from it play key roles in ablation process.Bulk quantities of SiO2 nanowires with diameter of 80 nm-150 nm and length of tens microns were observed on the surface of specimens after ablation.The growth mechanism of the SiO_2 nanowires was interpreted with a developed vapor-liquid-solid（VLS） driven by the temperature gradient.
