PS/SiO2 particles with core-shell structure were synthesized by coating silica on surface of polystyrene(PS) colloidal particles.The reaction parameters,such as initial tetraethyl orthosilicate(TEOS) concentration,wat...PS/SiO2 particles with core-shell structure were synthesized by coating silica on surface of polystyrene(PS) colloidal particles.The reaction parameters,such as initial tetraethyl orthosilicate(TEOS) concentration,water concentration and reaction temperature,have been investigated to control the thickness of silica shells.The shell thickness was prepositional to the square root of the initial concentration of TEOS and first increased with increasing water concentration,reached a maximum at about 2.0 mol/L and then started decreasing beyond that concentration.It was also found that the shell thickness decreased firstly with the reaction temperature added,then tended to a constant.The so-synthesized PS/SiO2 core-shell particles were directly crystallized into 3-D ordered thin film,then sintered at 570℃ into the ordered macroporous thin film.Compared with the conditional method,the present approach avoids repeatedly filling the precursor in the templetes and save time more.展开更多
In this study, novel core-shell SiO<sub>2</sub>-coated iron nanoparticles (SiO<sub>2</sub>-nZVI) were synthesized using a one-step Stoeber method. The Malachite green degradation abilities of t...In this study, novel core-shell SiO<sub>2</sub>-coated iron nanoparticles (SiO<sub>2</sub>-nZVI) were synthesized using a one-step Stoeber method. The Malachite green degradation abilities of the nanoparticles were investigated. The effects of ethanol/distilled water volume ratio, presence and absence of PEG, tetraethyl orthosilicate (TEOS) dosage, and hydrolysis time used in the nanoparticles preparation process were investigated. The results indicated that the SiO<sub>2</sub>-coated iron nanoparticles had the highest reduction activity when the particles synthesized with ethanol/H<sub>2</sub>O ratio of 2:1, PEG of 0.15 ml, TEOS of 0.5 ml and the reaction time was 4 h. The SiO<sub>2</sub>-nZVI nanoparticles were characterized using Transmission Electron Microscopy (TEM), Energy Dispersive Spectrometry (EDS) and powder X-Ray Diffraction (XRD). The results showed that the average particles diameter of the SiO<sub>2</sub>-nZVI was 20 - 30 nm. The thickness of the outside SiO<sub>2</sub> film is consistent and approximately 10 nm. The results indicated that the nanoparticles coated completely with a transparent SiO<sub>2</sub>-film. Such nanoparticles could have wide applications in dye decolorization.展开更多
Ni-Re/SiO2 catalysts with controllable Ni particle sizes(4.5–18.0 nm)were synthesized to investigate the effects of the particle size on the amination of monoethanolamine(MEA).The catalysts were characterized by vari...Ni-Re/SiO2 catalysts with controllable Ni particle sizes(4.5–18.0 nm)were synthesized to investigate the effects of the particle size on the amination of monoethanolamine(MEA).The catalysts were characterized by various techniques and evaluated for the amination reaction in a trickle bed reactor at 170℃,8.0 MPa,and 0.5 h^-1 liquid hourly space velocity of MEA(LHSVMEA)in NH3/H2 atmosphere.The Ni-Re/SiO2 catalyst with the lowest Ni particle size(4.5 nm)exhibited the highest yield(66.4%)of the desired amines(ethylenediamine(EDA)and piperazine(PIP)).The results of the analysis show that the turnover frequency of MEA increased slightly(from 193 to 253 h^-1)as the Ni particle sizes of the Ni-Re/SiO2 catalysts increased from 4.5 to 18.0 nm.Moreover,the product distribution could be adjusted by varying the Ni particle size.The ratio of primary to secondary amines increased from 1.0 to 2.0 upon increasing the Ni particle size from 4.5 to 18.0 nm.Further analyses reveal that the Ni particle size influenced the electronic properties of surface Ni,which in turn affected the adsorption of MEA and the reaction pathway of MEA amination.Compared to those of small Ni particles,large particles possessed a higher proportion of high-coordinated terrace Ni sites and a higher surface electron density,which favored the amination of MEA and NH3 to form EDA.展开更多
The β-SiC/SiO2 core-shell nanowires with the 'stem-and-node' structure were synthesized in the presence of cerium oxide by the carbothermal reduction of the starch-SiO2 hybrids gel.The samples were characteri...The β-SiC/SiO2 core-shell nanowires with the 'stem-and-node' structure were synthesized in the presence of cerium oxide by the carbothermal reduction of the starch-SiO2 hybrids gel.The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM) and energy-dispersed X-ray(EDX).The results showed that the nanowires consisted of a 20-35 nm diameter crystalline β-SiC core wrapped with a 2-5 n...展开更多
The dynamic viscoelastic behavior of polysiloxanes filled with ultrafine SiO 2 has become ever-lasting important due to its unique properties. In present article, the influence of SiO 2 treated with silane coupling ag...The dynamic viscoelastic behavior of polysiloxanes filled with ultrafine SiO 2 has become ever-lasting important due to its unique properties. In present article, the influence of SiO 2 treated with silane coupling agent bis(3-triethoxysilyl)tetrasulfane(TESPT) on dynamic viscoelastic properties of uncured polymethylvinylsiloxane(PMVS)/ultra fine-silica(SiO 2) composites was investigated by using an advanced rheometric expansion system(ARES) under the conditions of temperature 25 ℃, strain(γ) from 0.01% to 100% and frequency(ω) from 0.01 to 100 rad/s. The results reveal that the treated SiO 2 particles leads to the frequency-dependent storage modulus(G′) which approaches linear viscoelastic behavior in the lower frequency region. Based on an examination of the dynamic viscoelastic behavior and TEM observation, we owe these characteristics to improved dispersion of SiO 2 particles in the polymer matrix due to their surface-treatment as compared with the untreated case. On the other hand, dynamic viscoelastic behavior sensitively reflects the dispersion of SiO 2 particles with diameters from 100 to 500 nm, which further evidence the promotion of filler dispersion induced by the incorporation of TESPT.展开更多
基金Supported by the National Natural Science Foundation of China(No.:20221603)
文摘PS/SiO2 particles with core-shell structure were synthesized by coating silica on surface of polystyrene(PS) colloidal particles.The reaction parameters,such as initial tetraethyl orthosilicate(TEOS) concentration,water concentration and reaction temperature,have been investigated to control the thickness of silica shells.The shell thickness was prepositional to the square root of the initial concentration of TEOS and first increased with increasing water concentration,reached a maximum at about 2.0 mol/L and then started decreasing beyond that concentration.It was also found that the shell thickness decreased firstly with the reaction temperature added,then tended to a constant.The so-synthesized PS/SiO2 core-shell particles were directly crystallized into 3-D ordered thin film,then sintered at 570℃ into the ordered macroporous thin film.Compared with the conditional method,the present approach avoids repeatedly filling the precursor in the templetes and save time more.
文摘In this study, novel core-shell SiO<sub>2</sub>-coated iron nanoparticles (SiO<sub>2</sub>-nZVI) were synthesized using a one-step Stoeber method. The Malachite green degradation abilities of the nanoparticles were investigated. The effects of ethanol/distilled water volume ratio, presence and absence of PEG, tetraethyl orthosilicate (TEOS) dosage, and hydrolysis time used in the nanoparticles preparation process were investigated. The results indicated that the SiO<sub>2</sub>-coated iron nanoparticles had the highest reduction activity when the particles synthesized with ethanol/H<sub>2</sub>O ratio of 2:1, PEG of 0.15 ml, TEOS of 0.5 ml and the reaction time was 4 h. The SiO<sub>2</sub>-nZVI nanoparticles were characterized using Transmission Electron Microscopy (TEM), Energy Dispersive Spectrometry (EDS) and powder X-Ray Diffraction (XRD). The results showed that the average particles diameter of the SiO<sub>2</sub>-nZVI was 20 - 30 nm. The thickness of the outside SiO<sub>2</sub> film is consistent and approximately 10 nm. The results indicated that the nanoparticles coated completely with a transparent SiO<sub>2</sub>-film. Such nanoparticles could have wide applications in dye decolorization.
基金supported by the National Natural Science Foundation of China(21273227)Strategic Priority Research Program of Chinese Academy of Sciences(XDB17000000)~~
文摘Ni-Re/SiO2 catalysts with controllable Ni particle sizes(4.5–18.0 nm)were synthesized to investigate the effects of the particle size on the amination of monoethanolamine(MEA).The catalysts were characterized by various techniques and evaluated for the amination reaction in a trickle bed reactor at 170℃,8.0 MPa,and 0.5 h^-1 liquid hourly space velocity of MEA(LHSVMEA)in NH3/H2 atmosphere.The Ni-Re/SiO2 catalyst with the lowest Ni particle size(4.5 nm)exhibited the highest yield(66.4%)of the desired amines(ethylenediamine(EDA)and piperazine(PIP)).The results of the analysis show that the turnover frequency of MEA increased slightly(from 193 to 253 h^-1)as the Ni particle sizes of the Ni-Re/SiO2 catalysts increased from 4.5 to 18.0 nm.Moreover,the product distribution could be adjusted by varying the Ni particle size.The ratio of primary to secondary amines increased from 1.0 to 2.0 upon increasing the Ni particle size from 4.5 to 18.0 nm.Further analyses reveal that the Ni particle size influenced the electronic properties of surface Ni,which in turn affected the adsorption of MEA and the reaction pathway of MEA amination.Compared to those of small Ni particles,large particles possessed a higher proportion of high-coordinated terrace Ni sites and a higher surface electron density,which favored the amination of MEA and NH3 to form EDA.
基金supported by the National Key Technology R&D Program (2007BEA08B01)the Natural Science Foundation of Fujian Province of China (E0710004)Joint Research Program of Fuzhou University (DH-548)
文摘The β-SiC/SiO2 core-shell nanowires with the 'stem-and-node' structure were synthesized in the presence of cerium oxide by the carbothermal reduction of the starch-SiO2 hybrids gel.The samples were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM) and energy-dispersed X-ray(EDX).The results showed that the nanowires consisted of a 20-35 nm diameter crystalline β-SiC core wrapped with a 2-5 n...
文摘The dynamic viscoelastic behavior of polysiloxanes filled with ultrafine SiO 2 has become ever-lasting important due to its unique properties. In present article, the influence of SiO 2 treated with silane coupling agent bis(3-triethoxysilyl)tetrasulfane(TESPT) on dynamic viscoelastic properties of uncured polymethylvinylsiloxane(PMVS)/ultra fine-silica(SiO 2) composites was investigated by using an advanced rheometric expansion system(ARES) under the conditions of temperature 25 ℃, strain(γ) from 0.01% to 100% and frequency(ω) from 0.01 to 100 rad/s. The results reveal that the treated SiO 2 particles leads to the frequency-dependent storage modulus(G′) which approaches linear viscoelastic behavior in the lower frequency region. Based on an examination of the dynamic viscoelastic behavior and TEM observation, we owe these characteristics to improved dispersion of SiO 2 particles in the polymer matrix due to their surface-treatment as compared with the untreated case. On the other hand, dynamic viscoelastic behavior sensitively reflects the dispersion of SiO 2 particles with diameters from 100 to 500 nm, which further evidence the promotion of filler dispersion induced by the incorporation of TESPT.
