In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,H...In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,HRTEM-EDS,H2-TPR,XPS characterization,as well as catalytic activity and durability tests for the catalytic combustion of chlorobenzene(CB)were conducted to explore the relationship between the structure and catalytic performance of the catalysts.It is revealed that cuCe(6:1)/MCM-41 has the highest activity and can completely catalyze the degradation of CB at 260℃.The reasons for the high activity of the catalysts are as follows:MCM-41,a type of mesoporous material which has large pore size and large specific surface area,is suitable as a catalyst carrier.The average diameter of nano-sized CuO and CeO2 particles is about 3-5 nm and adding CeO2 improves the dispersion of active component CuO,which are highly and evenly dispersed on the surface of MCM-41.Characterization results also explain why MCM-41 supported CuO-CeO2 with appropriate proportion can highly enhance the catalytic activity.The reason is that CeO2 acting as an oxygen-rich material can improve the mobility of oxygen species through continuous redox between Ce4^+and Ce3^+,and improve the catalytic performance of CuO for CB combustion.Besides,CuCe(6:1)/MCM-41 also displays good durability for CB combustion,both in the humid condition and in the presence of benzene,making it a promising catalytic material for the elimination of chlorinated VOCs.展开更多
The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composit...The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composite were firstly subjected to a homogenization heat treatment at 450 ℃ and then an open-die forging at 450 ℃. The results indicated that the presence of reinforcing particles led to grain refinement and improvement of dynamic recrystallization. The forging process was more effective to eliminate the porosity in the cast alloy workpiece. Microhardness of the forged composite was increased by up to 80% and 16%, in comparison with those of the cast and forged alloy samples, respectively. Ultimate tensile strength and maximum tensile strain of the composite were improved by up to 45% and 23%, compared with those of the forged alloy in similar regions. These enhancements were respectively 50% and 37% in the compression test. The composite exhibited a fatigue life improvement in the region with low applied strain;however, a degradation was observed in the high applied strain region. Unlike AZ31 B samples, tensile, compressive and high cycle fatigue behaviors of the composite showed less sensitivity to the applied strain, which can be attributed to the amount of porosity in the samples before and after the hot-forging.展开更多
Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g...Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g ） = 3 Si2 N2O （ s ） ＋ N2 （ g ） . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition ： amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa （Vickers） at 1 600 ℃ .展开更多
Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitati...Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λ_(em)=600 nm exhibit two absorption bands;the first one is assigned to O^(2-)→Sm^(3+)charge transfer state(CTS) with a maximum absorption at 223 nm,and the second is due to intraconfigurational transition 4f^(5)-4f^(5) of Sm^(3+) with a maximum absorption at 407 nm.The 223 and 407 nm transitions are attributed to characteristics intra-configurational transitions of Sm^(3+).All emission spectra are dominated by reddish/orange luminescence located at 606 nm and assigned to ^(4)G_(5/2)→^(6)H_(7/2) transition.It is found that the photoluminescence intensity of samples obtained under excitation at 407 nm is 60 times smaller than that obtained under 223 nm excitation.Decay time measurements of the ^(4)G_(5/2)→^(6)H_(7/2) luminescence transition indicate that decay time of nano-sized powder is significantly shorter than bulk material one.展开更多
Sunlight-driven C-TiO2/FeTiO3 composites were synthesized with different weight fractions of FeTiO3. The as-prepared samples were characterized by UV-Visible diffuse reflectance spectroscopy, Fourier transform infrare...Sunlight-driven C-TiO2/FeTiO3 composites were synthesized with different weight fractions of FeTiO3. The as-prepared samples were characterized by UV-Visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, energy-dis- persive X-ray spectroscopy, and photoluminescence. Under sunlight irradiation, the C-TiO2/FeTiO3 photocatalysts degraded methyl orange （MO） efficiently and displayed much higher photocatalytic activity than that of pure FeTiO3 or carbon-doped titanium dioxide （C-TiO2）, and the C-TiOE/FeTiO3 photocatalyst with 10 wt% of FeTiO3 exhibited the highest photocatalytic activity. The enhancement of photocatalytic activity was mainly ascribed to the formation of a heterojunction between C-TiO2 and FeTiO3, which facilitated the transfer and separation of photogenerated electron-hole pairs. The quenching effects of different scavengers demonstrated that the reactive superoxide radicals （02-） and hydroxyl radicals （OH） played a major role in the MO degradation. The possible photocatalytic mechanism is discussed on the basis of the band structures of C-TiO2 and FeTiO3. To further enhance the photocatalytic efficiency, double-heterojunctioned CQD/C-TiO2/FeTiO3 composite was prepared by loading carbon quantum dots onto the C-TiO2/FeTiO3 surface.展开更多
以TiCl_3(3THF)为原料合成脒基钛(Ⅲ)配合物1,将其作为前驱体通过LPCVD沉积N/C-TiO_2薄膜。利用1HNMR、元素分析以及热重分析(TGA)探究配合物1的结构和热化学性质。结果表明,配合物1具有良好的热稳定性和合适的挥发性,满足CVD的要求。通...以TiCl_3(3THF)为原料合成脒基钛(Ⅲ)配合物1,将其作为前驱体通过LPCVD沉积N/C-TiO_2薄膜。利用1HNMR、元素分析以及热重分析(TGA)探究配合物1的结构和热化学性质。结果表明,配合物1具有良好的热稳定性和合适的挥发性,满足CVD的要求。通过EDS和UV-Vis吸收光谱表征了薄膜的成分及光学性能,结果表明,当沉积温度为350℃时,N/C-TiO_2薄膜的N、C质量分数最高,其禁带宽度降低为2. 82 e V,对可见光的吸收最强。与纯的二氧化钛薄膜相比,N/C-TiO_2薄膜对亚甲基蓝的降解率显著提高到90%。展开更多
A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and pr...A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, O2 temperature-programmed desorption （O2-TPD）, and inductively coupled with plasma atomic emission spectroscopy （ICP-AES） techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO （Mg/SiO2 weight ratio） shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.展开更多
The preparation of nanometer γ-Fe2O3 through an electrochemical process was studied at room temperature, using a metal iron plate as sacrificing anode and a sheet of stainless steel as cathode, in non-aqueous mediate...The preparation of nanometer γ-Fe2O3 through an electrochemical process was studied at room temperature, using a metal iron plate as sacrificing anode and a sheet of stainless steel as cathode, in non-aqueous mediate containing （Bu）4 NBr as support electrolyre and 2% （vol%） water. The powdery particles obtained were then calcined at 300 ℃. The products were characterized by IR, XRD, SEM, TEM and laser particle size analyser, indicating the fine particle is a pure nanometer γ-Fe2O3. The morphology is like coneshaped and their average size is 22.0 nm. Furthermore the VSM spectrum shows that the particle＇s coercivity （3.9 × 10^3 A/m） is rather small, presenting the excellent super-paramagnetism.展开更多
Herein,we successfully prepare highly dispersed and uniform small nano-size nickel nanoparticles embedded on core-shell carbon spheres by confined-deposition method.The mesoporous silica layer containing surfactant co...Herein,we successfully prepare highly dispersed and uniform small nano-size nickel nanoparticles embedded on core-shell carbon spheres by confined-deposition method.The mesoporous silica layer containing surfactant coated on the surface of the polymer sphere provides confined space and effectively controls the growth of nickel nanoparticles during pyrolysis.At the same time,the introduction of nickel species has an impact on structure of the obtained carbon spheres,and it can promote the deposition of carbon to realize the adjustment from hollow to core-shell and then to solid spheres.Owing to the uniform distribution of Ni nanoparticles with small size,mesoporous structure,N-doping groups,high specified surface areas,and core-shell structure,the obtained catalyst shows exciting ability for the production of CO by reduction of CO_(2)with a maximum CO Faradaic efficiency of 98%,indicating its promising prospect in electro-reduction of CO_(2).展开更多
Using a liquid-solid phase inversion method, a hybrid matrix poly（vinylidene fluoride）（PVDF） membrane was prepared with alumina（Al2O3） nanoparticle addition. Pd/Fe nanoparticles（NPs） were successfully immobili...Using a liquid-solid phase inversion method, a hybrid matrix poly（vinylidene fluoride）（PVDF） membrane was prepared with alumina（Al2O3） nanoparticle addition. Pd/Fe nanoparticles（NPs） were successfully immobilized on the Al2O3/PVDF membrane, which was characterized by Scanning Electron Microscopy（SEM） and Transmission Electron Microscopy（TEM）. The micrographs showed that the Pd/Fe NPs were dispersed homogeneously. Several important experimental parameters were optimized, including the mechanical properties, contact angle and surface area of Al2O3/PVDF composite membranes with different Al2O3 contents. At the same time, the ferrous ion concentration and the effect of hydrophilization were studied. The results showed that the modified Al2O3/PVDF membrane functioned well as a support. The Al2O3/PVDF membrane with immobilized Pd/Fe NPs exhibited high efficiency in terms of dichloroacetic acid（DCAA） dechlorination. Additionally, a reaction pathway for DCAA dechlorination by Pd/Fe NPs immobilized on the Al2O3/PVDF membrane system was proposed.展开更多
SiO2 glasses co-doped with Al3+ ions were prepared by a sol-gel method by holding 0.5% of Ce3+ ions constant and varying the Al3+ ions concentrations.Thermal stability,the structural,chemical and the optical propertie...SiO2 glasses co-doped with Al3+ ions were prepared by a sol-gel method by holding 0.5% of Ce3+ ions constant and varying the Al3+ ions concentrations.Thermal stability,the structural,chemical and the optical properties of the samples were studied by using differential scanning calorimetric(DSC),thermo gravimetric analysis(TGA),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),UV-vis spectroscopy and photoluminescence spectroscopy(PL).The DSC and TGA of samples depicted that the presence of dopant and co-dopant decreased the endothermic peak temperature and the yield respectively.SEM images showed that the particles were in the nano-range and spherical in shape.The XRD showed that all the samples were amorphous.The UV absorption measurements indicated that the presence of Al3+ ions significantly reduced the SiO2 absorption band,increased the absorbance intensity of SiO2 and decreased the transmittance as compared to the presence of the Ce3+ ions alone.The photoluminescence results displayed an optimum increase in luminescence intensity when the ratio of Al:Ce was 10:1 and further increase in aluminum content quenched the luminous intensity.展开更多
Nano-sized hexagonal magnesium hydroxide （Mg（OH）2） with good dispersibility was synthesized by a double injection-hydrothermal method, utilizing polyvinylpyrrolidone （PVP） as an additive and with optimized proce...Nano-sized hexagonal magnesium hydroxide （Mg（OH）2） with good dispersibility was synthesized by a double injection-hydrothermal method, utilizing polyvinylpyrrolidone （PVP） as an additive and with optimized processing parameters. SEM and BET analysis showed that the mean particle size and specific surface area of the Mg（OH）2 particles were 174 nm and 50.77 m^2/g, respectively. The FT-IR spectra and the XRD patterns showed that PVP was adsorbed on the surface of the Mg（OH）2 crystal, thus effectively limiting particle agglomeration and hindering crystal growth along the （1 01 ） plane. TGA showed a decrease in the decomposition temperature and an increase in the weight loss of the Mg（OH）2 particles due to addition of PV/.展开更多
Uniform nano-sized calcium hydroxide （Ca（OH）2） monocrystal powder was synthesized from calcium oxide in a surfactant solution via a digestion method by decreasing the surface tension of the reaction system to cont...Uniform nano-sized calcium hydroxide （Ca（OH）2） monocrystal powder was synthesized from calcium oxide in a surfactant solution via a digestion method by decreasing the surface tension of the reaction system to control the growth of crystalline Ca（OH）2. The Ca（OH）2 monocrystal powder samples were characterized by means of scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET）, and Fourier transform-infrared spectroscopy （FT-IR）. The NOx adsorption ability of the samples was evaluated, and the influence of various types and concentrations of surfactants on powder agglomeration and then the specific surface area in the precipitation process were studied. The specific surface area of the samples was found as high as 58 m2/g and 92 m2/g and the particle size, 300-400 nm and 200-300 nm in the presence of 10 wt% PEG600 and 0.086 mL/L SDS at a reaction time of 5 h, respectively. The product has an exceptionally strong adsorption ability for NOx, which makes it a highly promising adsorbent for emission control and air purification.展开更多
基金Project supported by the National Natural Science Foundation of China(21577094)Zhejiang Public Welfare Technology Research Project(LGG19B070003)the Foundation of Science and Technology of Shaoxing City(2018C10019)。
文摘In this paper,MCM-41 was synthesized by a soft template technique and MCM-41 supported CuO-CeO2 nano-sized catalysts with different Cu/Ce molar ratios were prepared by a deposition-precipitation method.N2 adsorption,HRTEM-EDS,H2-TPR,XPS characterization,as well as catalytic activity and durability tests for the catalytic combustion of chlorobenzene(CB)were conducted to explore the relationship between the structure and catalytic performance of the catalysts.It is revealed that cuCe(6:1)/MCM-41 has the highest activity and can completely catalyze the degradation of CB at 260℃.The reasons for the high activity of the catalysts are as follows:MCM-41,a type of mesoporous material which has large pore size and large specific surface area,is suitable as a catalyst carrier.The average diameter of nano-sized CuO and CeO2 particles is about 3-5 nm and adding CeO2 improves the dispersion of active component CuO,which are highly and evenly dispersed on the surface of MCM-41.Characterization results also explain why MCM-41 supported CuO-CeO2 with appropriate proportion can highly enhance the catalytic activity.The reason is that CeO2 acting as an oxygen-rich material can improve the mobility of oxygen species through continuous redox between Ce4^+and Ce3^+,and improve the catalytic performance of CuO for CB combustion.Besides,CuCe(6:1)/MCM-41 also displays good durability for CB combustion,both in the humid condition and in the presence of benzene,making it a promising catalytic material for the elimination of chlorinated VOCs.
文摘The effect of hot-forging process was investigated on microstructural and mechanical properties of AZ31 B alloy and AZ31 B/1.5 vol.%Al2 O3 nanocomposite under static and cycling loading. The as-cast alloy and composite were firstly subjected to a homogenization heat treatment at 450 ℃ and then an open-die forging at 450 ℃. The results indicated that the presence of reinforcing particles led to grain refinement and improvement of dynamic recrystallization. The forging process was more effective to eliminate the porosity in the cast alloy workpiece. Microhardness of the forged composite was increased by up to 80% and 16%, in comparison with those of the cast and forged alloy samples, respectively. Ultimate tensile strength and maximum tensile strain of the composite were improved by up to 45% and 23%, compared with those of the forged alloy in similar regions. These enhancements were respectively 50% and 37% in the compression test. The composite exhibited a fatigue life improvement in the region with low applied strain;however, a degradation was observed in the high applied strain region. Unlike AZ31 B samples, tensile, compressive and high cycle fatigue behaviors of the composite showed less sensitivity to the applied strain, which can be attributed to the amount of porosity in the samples before and after the hot-forging.
基金Funded by the National Science Foundation of China ( No.50375037)
文摘Si3N4-Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering （ LPS ）. The Si2 N2O phase was generated by an in-situ reaction 2 Si3 N4 （ s ） ＋ 1.5 02 （ g ） = 3 Si2 N2O （ s ） ＋ N2 （ g ） . The content of Si2 N2 O phase up to 60% in the volume was obtained at a sintering temperature of 1 650℃ and reduced when the sintering temperature increased or decreased, indicating the reaction is reversible. The mass loss, relative density and average grain size increased with increasing the sintering temperature. The average grain size was less than 500 nm when the sintering temperature was below 1 700 ℃. The sintering procedure contains a complex crystallization and a phase transition ： amorphous silicon nitride→equiaxial α- Si3 N4→ equiaxial β- Si3 N4→ rod- like Si2 N2O→ needle- like β- Si3N4 . Small round-shaped β→ Si3 N4 particles were entrapped in the Si2 N2O grains and a high density of staking faults was situated in the middle of Si2 N2O grains at a sintering temperature of 1 650 ℃. The toughness inereased from 3.5 MPa·m^1/2 at 1 600 ℃ to 7.2 MPa· m^1/2 at 1 800 ℃ . The hardness was as high as 21.5 GPa （Vickers） at 1 600 ℃ .
基金supported by Nuclear Research Center of Algiers(CRNA),Department of Laser,Luminescence Laboratory。
文摘Nanosized 1 at% Sm^(3+)doped Y_(2)O_(3)powders were prepared by an ultrasound assisted sol-gel method.Y_(2)O_(3):Sm^(3+)powders crystallize in Y_(2)O_(3)pure cubic phase and XRD analysis shows that the as-used agitation protocol affects strongly the crystallite’s shape and mean size.The recorded emission spectra under λ_(em)=600 nm exhibit two absorption bands;the first one is assigned to O^(2-)→Sm^(3+)charge transfer state(CTS) with a maximum absorption at 223 nm,and the second is due to intraconfigurational transition 4f^(5)-4f^(5) of Sm^(3+) with a maximum absorption at 407 nm.The 223 and 407 nm transitions are attributed to characteristics intra-configurational transitions of Sm^(3+).All emission spectra are dominated by reddish/orange luminescence located at 606 nm and assigned to ^(4)G_(5/2)→^(6)H_(7/2) transition.It is found that the photoluminescence intensity of samples obtained under excitation at 407 nm is 60 times smaller than that obtained under 223 nm excitation.Decay time measurements of the ^(4)G_(5/2)→^(6)H_(7/2) luminescence transition indicate that decay time of nano-sized powder is significantly shorter than bulk material one.
基金the University Grants Commission(UGC), New Delhi,India,for financial support with Ref.No.:17-06/ 2012(i)EU-V
文摘Sunlight-driven C-TiO2/FeTiO3 composites were synthesized with different weight fractions of FeTiO3. The as-prepared samples were characterized by UV-Visible diffuse reflectance spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, scanning electron microscopy, energy-dis- persive X-ray spectroscopy, and photoluminescence. Under sunlight irradiation, the C-TiO2/FeTiO3 photocatalysts degraded methyl orange （MO） efficiently and displayed much higher photocatalytic activity than that of pure FeTiO3 or carbon-doped titanium dioxide （C-TiO2）, and the C-TiOE/FeTiO3 photocatalyst with 10 wt% of FeTiO3 exhibited the highest photocatalytic activity. The enhancement of photocatalytic activity was mainly ascribed to the formation of a heterojunction between C-TiO2 and FeTiO3, which facilitated the transfer and separation of photogenerated electron-hole pairs. The quenching effects of different scavengers demonstrated that the reactive superoxide radicals （02-） and hydroxyl radicals （OH） played a major role in the MO degradation. The possible photocatalytic mechanism is discussed on the basis of the band structures of C-TiO2 and FeTiO3. To further enhance the photocatalytic efficiency, double-heterojunctioned CQD/C-TiO2/FeTiO3 composite was prepared by loading carbon quantum dots onto the C-TiO2/FeTiO3 surface.
文摘以TiCl_3(3THF)为原料合成脒基钛(Ⅲ)配合物1,将其作为前驱体通过LPCVD沉积N/C-TiO_2薄膜。利用1HNMR、元素分析以及热重分析(TGA)探究配合物1的结构和热化学性质。结果表明,配合物1具有良好的热稳定性和合适的挥发性,满足CVD的要求。通过EDS和UV-Vis吸收光谱表征了薄膜的成分及光学性能,结果表明,当沉积温度为350℃时,N/C-TiO_2薄膜的N、C质量分数最高,其禁带宽度降低为2. 82 e V,对可见光的吸收最强。与纯的二氧化钛薄膜相比,N/C-TiO_2薄膜对亚甲基蓝的降解率显著提高到90%。
基金supported by the Youth Fund Project(2002B25)of Sichuan Department of Educationthe Scientific Research Foundation for Doctor from Yibin College of China(2010B12)
文摘A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, O2 temperature-programmed desorption （O2-TPD）, and inductively coupled with plasma atomic emission spectroscopy （ICP-AES） techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO （Mg/SiO2 weight ratio） shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.
文摘The preparation of nanometer γ-Fe2O3 through an electrochemical process was studied at room temperature, using a metal iron plate as sacrificing anode and a sheet of stainless steel as cathode, in non-aqueous mediate containing （Bu）4 NBr as support electrolyre and 2% （vol%） water. The powdery particles obtained were then calcined at 300 ℃. The products were characterized by IR, XRD, SEM, TEM and laser particle size analyser, indicating the fine particle is a pure nanometer γ-Fe2O3. The morphology is like coneshaped and their average size is 22.0 nm. Furthermore the VSM spectrum shows that the particle＇s coercivity （3.9 × 10^3 A/m） is rather small, presenting the excellent super-paramagnetism.
基金financially supported by the Natural Science Foundation of Hebei(Nos.B02020208088,H2020206514 and B2021208074)S&T Program of Hebei(Nos.20544401D,20314401D,206Z4406G,21314402D,22344402D,22373709D,22284601Z and 21344601D)Tianjin Science and Technology Project(No.19YFSLQY00070)。
文摘Herein,we successfully prepare highly dispersed and uniform small nano-size nickel nanoparticles embedded on core-shell carbon spheres by confined-deposition method.The mesoporous silica layer containing surfactant coated on the surface of the polymer sphere provides confined space and effectively controls the growth of nickel nanoparticles during pyrolysis.At the same time,the introduction of nickel species has an impact on structure of the obtained carbon spheres,and it can promote the deposition of carbon to realize the adjustment from hollow to core-shell and then to solid spheres.Owing to the uniform distribution of Ni nanoparticles with small size,mesoporous structure,N-doping groups,high specified surface areas,and core-shell structure,the obtained catalyst shows exciting ability for the production of CO by reduction of CO_(2)with a maximum CO Faradaic efficiency of 98%,indicating its promising prospect in electro-reduction of CO_(2).
基金supported by the Nature Science Foundation of Heilongjiang Province (No. B201410)the Postdoctoral Foundation Project of Heilongjiang Province (No. LBH-Z13128)+3 种基金the Science and Technology Research Program of Education Bureau of Heilongjiang Province (No. 12531206)the Special Scientific Research Projects of Harbin Normal University (12XQXG02)the National Nature Science Foundation of China (No. 41030743)the National Nature Science Foundation of China (No. 42171217)
文摘Using a liquid-solid phase inversion method, a hybrid matrix poly（vinylidene fluoride）（PVDF） membrane was prepared with alumina（Al2O3） nanoparticle addition. Pd/Fe nanoparticles（NPs） were successfully immobilized on the Al2O3/PVDF membrane, which was characterized by Scanning Electron Microscopy（SEM） and Transmission Electron Microscopy（TEM）. The micrographs showed that the Pd/Fe NPs were dispersed homogeneously. Several important experimental parameters were optimized, including the mechanical properties, contact angle and surface area of Al2O3/PVDF composite membranes with different Al2O3 contents. At the same time, the ferrous ion concentration and the effect of hydrophilization were studied. The results showed that the modified Al2O3/PVDF membrane functioned well as a support. The Al2O3/PVDF membrane with immobilized Pd/Fe NPs exhibited high efficiency in terms of dichloroacetic acid（DCAA） dechlorination. Additionally, a reaction pathway for DCAA dechlorination by Pd/Fe NPs immobilized on the Al2O3/PVDF membrane system was proposed.
基金the National Research Foundation and the University of the Free Statefor financial support
文摘SiO2 glasses co-doped with Al3+ ions were prepared by a sol-gel method by holding 0.5% of Ce3+ ions constant and varying the Al3+ ions concentrations.Thermal stability,the structural,chemical and the optical properties of the samples were studied by using differential scanning calorimetric(DSC),thermo gravimetric analysis(TGA),X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),UV-vis spectroscopy and photoluminescence spectroscopy(PL).The DSC and TGA of samples depicted that the presence of dopant and co-dopant decreased the endothermic peak temperature and the yield respectively.SEM images showed that the particles were in the nano-range and spherical in shape.The XRD showed that all the samples were amorphous.The UV absorption measurements indicated that the presence of Al3+ ions significantly reduced the SiO2 absorption band,increased the absorbance intensity of SiO2 and decreased the transmittance as compared to the presence of the Ce3+ ions alone.The photoluminescence results displayed an optimum increase in luminescence intensity when the ratio of Al:Ce was 10:1 and further increase in aluminum content quenched the luminous intensity.
基金financial support of National Natural Science Foundation of China(Contract No. 21176266)
文摘Nano-sized hexagonal magnesium hydroxide （Mg（OH）2） with good dispersibility was synthesized by a double injection-hydrothermal method, utilizing polyvinylpyrrolidone （PVP） as an additive and with optimized processing parameters. SEM and BET analysis showed that the mean particle size and specific surface area of the Mg（OH）2 particles were 174 nm and 50.77 m^2/g, respectively. The FT-IR spectra and the XRD patterns showed that PVP was adsorbed on the surface of the Mg（OH）2 crystal, thus effectively limiting particle agglomeration and hindering crystal growth along the （1 01 ） plane. TGA showed a decrease in the decomposition temperature and an increase in the weight loss of the Mg（OH）2 particles due to addition of PV/.
文摘Uniform nano-sized calcium hydroxide （Ca（OH）2） monocrystal powder was synthesized from calcium oxide in a surfactant solution via a digestion method by decreasing the surface tension of the reaction system to control the growth of crystalline Ca（OH）2. The Ca（OH）2 monocrystal powder samples were characterized by means of scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, high resolution transmission electron microscopy （HRTEM）, X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET）, and Fourier transform-infrared spectroscopy （FT-IR）. The NOx adsorption ability of the samples was evaluated, and the influence of various types and concentrations of surfactants on powder agglomeration and then the specific surface area in the precipitation process were studied. The specific surface area of the samples was found as high as 58 m2/g and 92 m2/g and the particle size, 300-400 nm and 200-300 nm in the presence of 10 wt% PEG600 and 0.086 mL/L SDS at a reaction time of 5 h, respectively. The product has an exceptionally strong adsorption ability for NOx, which makes it a highly promising adsorbent for emission control and air purification.
