Mesoporous poly(styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis was achieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydrid...Mesoporous poly(styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis was achieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydride copolymer in the presence of 3-aminopropyl triethoxysilane (APTES) as a coupling agent and citric acid as a nonsurfactant template or pore-forming agent, followed by ethanol extraction. Characterization results from nitrogen sorption isotherms and powder X-ray diffraction indicate that polymer-modified mesoporous materials with large specific surface areas (e.g. 900 m(2)/g) and pore volumes (e.g. 0.6 cm(3)/g) could be prepared. As the citric acid concentration is increased, the specific surface areas, pore volumes and pore diameters of the hybrid materials increase.展开更多
To obtain homogenous layered oxide Li（Co1/3Ni1/3Mn1/3）O2 as a lithium insertion positive electrode material, the sol-gel process using citric acid as a chelating agent was applied. The material Li（Co1/3Ni1/3Mn1/3）...To obtain homogenous layered oxide Li（Co1/3Ni1/3Mn1/3）O2 as a lithium insertion positive electrode material, the sol-gel process using citric acid as a chelating agent was applied. The material Li（Co1/3Ni1/3Mn1/3）O2 was synthesized at different calcination temperatures. XRD experiment indicated that the layered Li（Co1/3Ni1/3Mn1/3）O2 material could be synthesized at a lower temperature of 800℃, and the oxidation state of Co, Ni, and Mn in the cathode confirmed by XPS were ＋3, ＋2, and ＋4, respectively. SEM observations showed that the synthesized material could form homogenous particle morphology with the particle size of about 200 nm. In spite of different calcination temperatures, the charge-discharge curves of all the samples for the initial cycle were similar, and the cathode synthesized at 900℃ showed a small irreversible capacity loss of 11.24% and a high discharge capacity of 212.2 mAh·g^-1 in the voltage range of 2.9-4.6 V.展开更多
CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared s...CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.展开更多
Nanosized nickel oxide powders were prepared by thermal decomposition of the nickel citrate gel precursors. The thermal decomposition and powder materials derived from calcination of these gel precursors with various ...Nanosized nickel oxide powders were prepared by thermal decomposition of the nickel citrate gel precursors. The thermal decomposition and powder materials derived from calcination of these gel precursors with various ratios of citric acid （CA） to nickel at different temperatures and times were characterized by thermal analysis （TG/DTA）, scanning electron microscopy （SEM）, x-ray diffraction （XRD）, and measurement of specific surface area （BET） with porosity analyses. The optimized processing conditions of calcination temperature 400℃ for 1 hour with the CA/Ni ratio of 1.2, were determined to produce the nanosized nickel oxide pow- ders with a high specific surface area of 181 m^2/g, nanometer particle sizes of 15-25 nm, micro-pore diameter distribution between 4-10 nm. The capacitance characteristics of the nanosized nickel oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） exhibiting both a double-layer capacitance and a faradaic pseudocapacitance. The nanosized nickel oxide electrode shows a high cyclic stability and is promising for high performance electrochemical capacitors.展开更多
The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry an...The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry analysis. The expe rimental results show that phase transformation reactions of FeCO 3, Fe 2O 3 and BaFe 2O 4, barium hexaferrite and γ-Fe 2O 3 take place in the heat tr eatment of gel. While the doping lanthanide ion replace barium ion, an equivalen t quantity of Fe 3+ are reduced to Fe 2+ to maintain the charge equili brium.展开更多
Structural strengthening of the nano porous silica films has been reported. The films were prepared with a base/acid two-step catalyzed TEOS-based sol-gel processing and dip-coating, and then baked in the mixed gas of...Structural strengthening of the nano porous silica films has been reported. The films were prepared with a base/acid two-step catalyzed TEOS-based sol-gel processing and dip-coating, and then baked in the mixed gas of ammonia and water vapor. The silica films were characterized with TEM, AFM, FTIR, spectrophotometer, ellipsometer, and abrasion test, respectively. The experimental results have shown that the films have a nanostructure with a low refractive index and can form an excellent scratch-resistant broadband anti-reflectance. The two-step catalysis noticeably strengthens the films, and the mixed gas treatment further improves mechanical strength of the silica network. Finally the strengthening mechanism has been discussed.展开更多
A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of an alkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4 ' -hydroxy azobenzene was covalen...A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of an alkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4 ' -hydroxy azobenzene was covalently bonded to the triethoxysilane derivative, i.e, gamma -isocyanatopropyl triethoxysilane. The preparation process and properties of the sol-gel derived NLO polymer were studied and characterized by SEM, FTIR,H-1-NMR, UV-Vis, DSC and second harmonic generation (SHG) measurement. The results indicated that the chemical bonding of the chromophores to the inorganic SiO2 networks induces low dipole alignment relaxation and preferable orientational stability. The SHG measurements also showed that the bonded polymer film containing 75 wt% of the akoxysilane dye has a high electro-optic coefficient (r(33)) of 7.1 pm/V at 1.1 mum wavelength, and exhibit good SHG stability, the r(33) values can maintain about 92.7% of its initial value at room temperature for 90 days, and can maintain about 59.3% at 100 degreesC for 300 min.展开更多
Hafnium oxide thin films （HOTFs） were successfully deposited onto amorphous glasses using chemical bath deposition, successive ionic layer absorption and reaction （SILAR）, and sol-gel methods. The same reactive pr...Hafnium oxide thin films （HOTFs） were successfully deposited onto amorphous glasses using chemical bath deposition, successive ionic layer absorption and reaction （SILAR）, and sol-gel methods. The same reactive precursors were used for all of the methods, and all of the films were annealed at 300℃ in an oven （ambient conditions）. After this step, the optical and structural properties of the films produced by using the three different methods were compared. The structures of the films were analyzed by X-ray diffTaction （XRD）. The optical properties are investigated using the ultraviolet-visible （UV-VIS） spectroscopic technique. The film thickness was measured via atomic force microscopy （AFM） in the tapping mode. The surface properties and elemental ratios of the films were investigated and measured by scanning electron microscopy and energy-dispersive X-ray spectroscopy （EDX）. The lowest transmittance and the highest reflectance values were observed for the films produced using the SILAR method. In addition, the most intense characteristic XRD peak was observed in the diffraction pattern of the film produced using the SILAR method, and the greatest thickness and average grain size were calculated for the film produced using the SILAR method. The films produced using SILAR method contained fewer cracks than those produced using the other methods. In conclusion, the SILAR method was observed to be the best method for the production of HOTFs.展开更多
Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H2O and catalyst. All poled polymer network films possess high second-...Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H2O and catalyst. All poled polymer network films possess high second-order nonlinear optical coefficients (d(33)) Of 10(-7)similar to 10(-8) esu. The investigation of NLO temporal stability at room temperature and elevated temperature (120 degreesC) indicated that these films exhibit high d(33) stability because the orientation of the chromophores are locked in the phenoxysilicon organic/inorganic networks.展开更多
Nanosized Ni-Mn oxide powders have been successfully citrate gel precursors. The powder materials derived from prepared by thermal decomposition of the Ni-Mn calcination of the gel precursors with various molar ratios...Nanosized Ni-Mn oxide powders have been successfully citrate gel precursors. The powder materials derived from prepared by thermal decomposition of the Ni-Mn calcination of the gel precursors with various molar ratios of nickel and manganese at different temperatures and time were characterized using thermal analysis （TG-DSC）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Brunauer-Emmet-Teller （BET）. The optimized processing conditions of calcination at 400℃ for 1 h with Ni/Mn molar ratio 6 were proved to produce the nanosized Ni-Mn oxide powders with a high specific surface area of 109.62 m^2/g and nanometer particle sizes of 15-30 nm. The capacitance characteristics of the nanosized Ni-Mn oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） and exhibited both a doublelayer capacitance and a Faradaic capacitance which could be attributed to the electrode consisting of Ni-Mn oxides and residual carbons from the organic gel thermal decomposition. A specific capacitance of 194.8 F/g was obtained for the electrode at the sweep rate of 10 mV/s in 4 mol/L KOH electrolyte and the capacitor showed quite high cyclic stability and is promising for advanced electrochemical capacitors.展开更多
The supported membranes of Al 2O 3 and its modification membranes were prepared.Al 2O 3,Al 2O 3 SiO 2 TiO 2 and Al 2O 3 SiO 2 TiO 2 ZrO 2 membranes were mamufatured by the slip casting process using...The supported membranes of Al 2O 3 and its modification membranes were prepared.Al 2O 3,Al 2O 3 SiO 2 TiO 2 and Al 2O 3 SiO 2 TiO 2 ZrO 2 membranes were mamufatured by the slip casting process using mixing boehmite,silicate,titania and zirconia sols under proper conditions,then the composite membrane was prepared.The structure and characteristics of the membrane were determined by XRD,SEM and AFM measurement.The conditions of preparation of the membrane are discussed.The thickness of the layer is about 1-2μm,the diameter of an average pore is 200-300nm and has a narrow pore distribution without crack forming.By changing the ratios of Al∶Si∶Ti∶Zr(mol),variations of surface pore size of Al 2O 3 SiO 2 TiO 2 ZrO 2 membrane can be gained.展开更多
Hydroxyapatite/alumina nanocrystalline composite powders needed for various biomedical applications were successfully synthe- sized by sol-gel process. Structural and morphological investigations of the prepared compo...Hydroxyapatite/alumina nanocrystalline composite powders needed for various biomedical applications were successfully synthe- sized by sol-gel process. Structural and morphological investigations of the prepared composite powders were performed using X-ray dif- fractometer （XRD）, scanning electron microscopy （SEM）, X＇Pert HighScore software, and Clemex Vision image analysis software. The re- suits show that the crystallite size of the obtained composite powders is in the range of 25 to 90 nm. SEM evaluation shows that the obtained composite powders have a porous structure, which is very useful for biomedical applications. The spherical nanoparticles in the range of 60 to 800 nm are embedded in the agglomerated clusters of the prepared composite powders.展开更多
Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network...Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network in the resin and thus influenced the rheological behavior greatly. However, the nano silica did not show a significant influence on the mechanical properties of the cured resins.展开更多
An effective and reproducible preparation of silica sol nanospheres via a modified sol-gel process has been described. Monodisperse and stable silica sol nanospheres with uniformsize were successfully obtained through...An effective and reproducible preparation of silica sol nanospheres via a modified sol-gel process has been described. Monodisperse and stable silica sol nanospheres with uniformsize were successfully obtained through the optimized synthesis in which the mixture of tetraethyl orthosilicate （TEOS） and ethanol was followed by the addition of water and ammonium hydroxide （NH3） separately, and the size of silica sol spheres was strictly controlled in the range of 25-119 nm with a narrow size distribution by fine adjustment of several reaction parameters. Results showed that in the presence of low concentration of TEOS, spheres size rose first and reached maximum when H2O concentration was up to 66 g/L. However, the diameter of silica sol spheres decreased above 66 g/L of H2O concentration. Furthermore, it was also found that the size and size distribution of silica sol nanospheres were affected by NH3 concentration. As NH3 concentration increased from 15 to 35 g/L, the diameter declined from 83 to 64 nm. Nevertheless, higher NH3 concentration would result in relatively broad size distribution, and gelation occurred when NH3 concentration reached 44 g/L. In addition, the effect of the different feed rates ofNH3 on the size growth of silica sol nanospheres was also discussed.展开更多
The nanocrystalline TiO_2 powder were prepared by improved sol-gel method at low temperature under ambient pressure. The prepared TiO_2 powder was characterized by X-ray diffraction (XRD), transmission electron micros...The nanocrystalline TiO_2 powder were prepared by improved sol-gel method at low temperature under ambient pressure. The prepared TiO_2 powder was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM). It is found that the yield of anatase TiO_2 significantly increases with the reduction of pH by increasing the nucleation rate of anatase. There is an optimum amount of water in sol for the formation of anatase by combining two effects on the concentration of Ti(OH)_4 in gels. Increasing in reaction temperature also benefit to the nucleation of anatase of TiO_2.展开更多
Lead-free （Na0.sK0.5）Nb03 （NKN） thin films were fabricated by spin coating on Pt/Ti/SiO2/Si substrates by a diol-based sol-gel process. Na-acetate, K-acetate, Nb-pentaethoxide and 1,3 propanediol were used to prep...Lead-free （Na0.sK0.5）Nb03 （NKN） thin films were fabricated by spin coating on Pt/Ti/SiO2/Si substrates by a diol-based sol-gel process. Na-acetate, K-acetate, Nb-pentaethoxide and 1,3 propanediol were used to prepare the NKN precursor solution. Thermal analysis showed two characteristic temperatures of 360 and 600℃. Based on these temperatures, a heat treatment program with pyrolysis at 360℃ and calcination at 600℃ after every layer was used. To avoid inhomogeneities and secondary phases, an excess of sodium and potassium was necessary. To evaluate the proper excess amount of sodium and potassium secondary ion mass spectrometry （SIMS） lateral element maps and X-ray diffraction （XRD） patterns were recorded. An excess amount of 20% led to homogeneous distribution of the elements and to single phase perovskite NKN films with random crystal orientation. Scanning electron microscopy （SEMI images showed a pore free surface with 100 nm grains. The leakage current measurements showed a current of lx10-3 A/cm2 at 150 kV/cm.展开更多
Electrical transport and thermoelectric properties of Ni-doped YCOl-xNixO3 （0 ≤ x ≤0.07）, prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that wit...Electrical transport and thermoelectric properties of Ni-doped YCOl-xNixO3 （0 ≤ x ≤0.07）, prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that with the increase of Ni doping content, the values of DC resistivity of YCo 1-xNixO3 decrease, but carder concentration increases. The temperature dependences of the resistivity for YCOl-xNixO3 are found to follow a relation of lnp o, lIT in a low-temperature range （LTR） （T 〈- 304 K for x = 0; - 230 K 〈 T 〈- 500 K for x = 0.02, 0.05, and 0.07） and high-temperature range （HTR） （T 〉-655 K for all compounds）, respectively. The estimated apparent activation energies for conduction Eal in LRT and Ea2 in HTR are both found to decrease monotonically with doping content increasing. At very low temperatures （T 〈-230 K）, Mott＇s law is observed for YCOl-xNixO3 （x≥ 0.02）, indicating that considerable localized states form in the heavy doping compounds. Although the Seebeck coefficient of the compound decreases after Ni doping, the power factor of YCOl-xNixO3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo0.98Ni0.0203, indicating that the high-temperature thermoelectric property of YCoO3 can be improved by partial substitution of Ni for Co.展开更多
The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymeri...The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.展开更多
Bi-substituted dysprosium iron garnet films were prepared by sol-gel process, and were annealed for crystallization. The crystallographic structures of garnet films annealed at different temperatures were analyzed by ...Bi-substituted dysprosium iron garnet films were prepared by sol-gel process, and were annealed for crystallization. The crystallographic structures of garnet films annealed at different temperatures were analyzed by XRD, the film annealed at 650℃ was polycrystalline garnet with no preferred orientation and no impurity crystalline phase. Magnetic and magneto-optical properties were investigated, the film had magnetic anisotropy perpendicular to the film plane, and exhibited strong coercivity of 1100-1600 Oe and high squareness. These films had large figures of merit applicable to magneto-optic storage, with 2 deg. at λ=430 nm and 1.5 deg. at λ=520 nm respectively.展开更多
Mn substitution compounds YCOl-xMnxO3 （0 ≤ x ≤ 0.2） are synthesized by using the sol-gel process. Electrical transport properties of YCo1-xMnxO3 are investigated in the temperature range from 200 K to 780 K. The e...Mn substitution compounds YCOl-xMnxO3 （0 ≤ x ≤ 0.2） are synthesized by using the sol-gel process. Electrical transport properties of YCo1-xMnxO3 are investigated in the temperature range from 200 K to 780 K. The experimental results show that after Mn substitution the electrical resistivity of YCo1-xMnxO3 first increases, then decreases, which is due to the electrons introduced by Mn doping. The sign of Seebeck coefficient for YCo1-xMnxO3 （x ≠ 0） is positive or negative, which is also proved by the Hall coefficient measurement. Moreover, at about room temperature, the Seebeck coefficient of YCO1-xMnxO3 with 1% doping Mn content becomes a negative value, whose absolute value is maximum; furthermore, the absolute value gradually decreases with increasing the Mn substitution content, which can be explained by the double carder model.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 29874002) and the Outstanding Young Scientist Award from National Natural Science Foundation of China (No. 29825504)
文摘Mesoporous poly(styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis was achieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydride copolymer in the presence of 3-aminopropyl triethoxysilane (APTES) as a coupling agent and citric acid as a nonsurfactant template or pore-forming agent, followed by ethanol extraction. Characterization results from nitrogen sorption isotherms and powder X-ray diffraction indicate that polymer-modified mesoporous materials with large specific surface areas (e.g. 900 m(2)/g) and pore volumes (e.g. 0.6 cm(3)/g) could be prepared. As the citric acid concentration is increased, the specific surface areas, pore volumes and pore diameters of the hybrid materials increase.
基金The authors would like to thank the financial support of the Major State Basic Research Development Program of China (No.2002CB613303)the National Natural Science Foundation of China (No.20371038)the Foundation for Innovative Research Team of Hubei Province of China(No.2005ABC004).
文摘To obtain homogenous layered oxide Li（Co1/3Ni1/3Mn1/3）O2 as a lithium insertion positive electrode material, the sol-gel process using citric acid as a chelating agent was applied. The material Li（Co1/3Ni1/3Mn1/3）O2 was synthesized at different calcination temperatures. XRD experiment indicated that the layered Li（Co1/3Ni1/3Mn1/3）O2 material could be synthesized at a lower temperature of 800℃, and the oxidation state of Co, Ni, and Mn in the cathode confirmed by XPS were ＋3, ＋2, and ＋4, respectively. SEM observations showed that the synthesized material could form homogenous particle morphology with the particle size of about 200 nm. In spite of different calcination temperatures, the charge-discharge curves of all the samples for the initial cycle were similar, and the cathode synthesized at 900℃ showed a small irreversible capacity loss of 11.24% and a high discharge capacity of 212.2 mAh·g^-1 in the voltage range of 2.9-4.6 V.
基金supported by the National Natural Science Foundation of China (NO. 20976013, 21006057)
文摘CeO2-promoted Ni/Al2O3-ZrO2 （Ni/Al2O3-ZrO2-CeO2） catalysts were prepared by a direct sol-gel process with citric acid as gelling agent. The catalysts used for the methane reforming with CO2 was studied by infrared spectroscopy （IR）, thermal gravimetric analysis （TGA）, microscopic analysis, X-ray diffraction （XRD） and temperature-programmed reduction （TPR）. The catalytic performance for CO2 reforming of methane to synthesis gas was investigated in a continuous-flow micro-reactor under atmospheric pressure. TGA, IR, XRD and microscopic analysis show that the catalysts prepared by the direct sol-gel process consist of Ni particles with a nanostructure of around 5 nm and an amorphous-phase composite oxide support. There exists a chemical interaction between metallic Ni particles and supports, which makes metallic Ni well dispersed, highly active and stable. The addition of CeO2 effectively improves the dispersion and the stability of Ni particles of the prepared catalysts, and enhances the adsorption of CO2 on the surface of catalysts. The catalytic tests for methane reforming with CO2 to synthesis gas show that the Ni/Al2O3-ZrO2-CeO2 catalysts show excellent activity and stability compared with the Ni/Al2O3 catalyst. The excellent catalytic activity and stability of the Ni/Al2O3-ZrO2-CeO2 are attributed to the highly, uniformly and stably dispersed small metallic Ni particles, the high reducibility of the Ni oxides and the interaction between metallic Ni particles and the composite oxide supports.
基金the National Natural Science Foundation of China(No.50134020)
文摘Nanosized nickel oxide powders were prepared by thermal decomposition of the nickel citrate gel precursors. The thermal decomposition and powder materials derived from calcination of these gel precursors with various ratios of citric acid （CA） to nickel at different temperatures and times were characterized by thermal analysis （TG/DTA）, scanning electron microscopy （SEM）, x-ray diffraction （XRD）, and measurement of specific surface area （BET） with porosity analyses. The optimized processing conditions of calcination temperature 400℃ for 1 hour with the CA/Ni ratio of 1.2, were determined to produce the nanosized nickel oxide pow- ders with a high specific surface area of 181 m^2/g, nanometer particle sizes of 15-25 nm, micro-pore diameter distribution between 4-10 nm. The capacitance characteristics of the nanosized nickel oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） exhibiting both a double-layer capacitance and a faradaic pseudocapacitance. The nanosized nickel oxide electrode shows a high cyclic stability and is promising for high performance electrochemical capacitors.
文摘The phase-transformation in sol-gel preparation of barium hexaferrite and the formation of barium hexaferrite doped with La 3+ were studied by chemical p hase analysis, X-ray diffraction and infrared spectrometry analysis. The expe rimental results show that phase transformation reactions of FeCO 3, Fe 2O 3 and BaFe 2O 4, barium hexaferrite and γ-Fe 2O 3 take place in the heat tr eatment of gel. While the doping lanthanide ion replace barium ion, an equivalen t quantity of Fe 3+ are reduced to Fe 2+ to maintain the charge equili brium.
基金the National Natural Science Foundation of China(No:69978017,20133040)Shanghai Key Subject Programme,Chinese Foundation of High Technology(2002AA842052)Shanghai Natural Science Foundation(02ZE14101)as well as Shanghai Nanotechnology Promotion Center(0159um039).
文摘Structural strengthening of the nano porous silica films has been reported. The films were prepared with a base/acid two-step catalyzed TEOS-based sol-gel processing and dip-coating, and then baked in the mixed gas of ammonia and water vapor. The silica films were characterized with TEM, AFM, FTIR, spectrophotometer, ellipsometer, and abrasion test, respectively. The experimental results have shown that the films have a nanostructure with a low refractive index and can form an excellent scratch-resistant broadband anti-reflectance. The two-step catalysis noticeably strengthens the films, and the mixed gas treatment further improves mechanical strength of the silica network. Finally the strengthening mechanism has been discussed.
基金This work was supported by the Postdoctoral Science Foundation of Guangdong Province (No. 9644) and the Natural Science Fund of Guangdong Province(No. 990629).
文摘A new organic/inorganic hybrid nonlinear optical (NLO) material was developed by the sol-gel process of an alkoxysilane dye with tetraethoxysilane. A NLO moiety based on 4-nitro-4 ' -hydroxy azobenzene was covalently bonded to the triethoxysilane derivative, i.e, gamma -isocyanatopropyl triethoxysilane. The preparation process and properties of the sol-gel derived NLO polymer were studied and characterized by SEM, FTIR,H-1-NMR, UV-Vis, DSC and second harmonic generation (SHG) measurement. The results indicated that the chemical bonding of the chromophores to the inorganic SiO2 networks induces low dipole alignment relaxation and preferable orientational stability. The SHG measurements also showed that the bonded polymer film containing 75 wt% of the akoxysilane dye has a high electro-optic coefficient (r(33)) of 7.1 pm/V at 1.1 mum wavelength, and exhibit good SHG stability, the r(33) values can maintain about 92.7% of its initial value at room temperature for 90 days, and can maintain about 59.3% at 100 degreesC for 300 min.
文摘Hafnium oxide thin films （HOTFs） were successfully deposited onto amorphous glasses using chemical bath deposition, successive ionic layer absorption and reaction （SILAR）, and sol-gel methods. The same reactive precursors were used for all of the methods, and all of the films were annealed at 300℃ in an oven （ambient conditions）. After this step, the optical and structural properties of the films produced by using the three different methods were compared. The structures of the films were analyzed by X-ray diffTaction （XRD）. The optical properties are investigated using the ultraviolet-visible （UV-VIS） spectroscopic technique. The film thickness was measured via atomic force microscopy （AFM） in the tapping mode. The surface properties and elemental ratios of the films were investigated and measured by scanning electron microscopy and energy-dispersive X-ray spectroscopy （EDX）. The lowest transmittance and the highest reflectance values were observed for the films produced using the SILAR method. In addition, the most intense characteristic XRD peak was observed in the diffraction pattern of the film produced using the SILAR method, and the greatest thickness and average grain size were calculated for the film produced using the SILAR method. The films produced using SILAR method contained fewer cracks than those produced using the other methods. In conclusion, the SILAR method was observed to be the best method for the production of HOTFs.
文摘Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H2O and catalyst. All poled polymer network films possess high second-order nonlinear optical coefficients (d(33)) Of 10(-7)similar to 10(-8) esu. The investigation of NLO temporal stability at room temperature and elevated temperature (120 degreesC) indicated that these films exhibit high d(33) stability because the orientation of the chromophores are locked in the phenoxysilicon organic/inorganic networks.
基金This work was supported by the National Natural Science Foundation of China under Grant No.50134020.
文摘Nanosized Ni-Mn oxide powders have been successfully citrate gel precursors. The powder materials derived from prepared by thermal decomposition of the Ni-Mn calcination of the gel precursors with various molar ratios of nickel and manganese at different temperatures and time were characterized using thermal analysis （TG-DSC）, scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Brunauer-Emmet-Teller （BET）. The optimized processing conditions of calcination at 400℃ for 1 h with Ni/Mn molar ratio 6 were proved to produce the nanosized Ni-Mn oxide powders with a high specific surface area of 109.62 m^2/g and nanometer particle sizes of 15-30 nm. The capacitance characteristics of the nanosized Ni-Mn oxide electrode in various concentrations of KOH solutions were studied by the cyclic voltammetry （CV） and exhibited both a doublelayer capacitance and a Faradaic capacitance which could be attributed to the electrode consisting of Ni-Mn oxides and residual carbons from the organic gel thermal decomposition. A specific capacitance of 194.8 F/g was obtained for the electrode at the sweep rate of 10 mV/s in 4 mol/L KOH electrolyte and the capacitor showed quite high cyclic stability and is promising for advanced electrochemical capacitors.
基金Project cooperated with College of Environment Engineering,Huazhong University of Technology
文摘The supported membranes of Al 2O 3 and its modification membranes were prepared.Al 2O 3,Al 2O 3 SiO 2 TiO 2 and Al 2O 3 SiO 2 TiO 2 ZrO 2 membranes were mamufatured by the slip casting process using mixing boehmite,silicate,titania and zirconia sols under proper conditions,then the composite membrane was prepared.The structure and characteristics of the membrane were determined by XRD,SEM and AFM measurement.The conditions of preparation of the membrane are discussed.The thickness of the layer is about 1-2μm,the diameter of an average pore is 200-300nm and has a narrow pore distribution without crack forming.By changing the ratios of Al∶Si∶Ti∶Zr(mol),variations of surface pore size of Al 2O 3 SiO 2 TiO 2 ZrO 2 membrane can be gained.
文摘Hydroxyapatite/alumina nanocrystalline composite powders needed for various biomedical applications were successfully synthe- sized by sol-gel process. Structural and morphological investigations of the prepared composite powders were performed using X-ray dif- fractometer （XRD）, scanning electron microscopy （SEM）, X＇Pert HighScore software, and Clemex Vision image analysis software. The re- suits show that the crystallite size of the obtained composite powders is in the range of 25 to 90 nm. SEM evaluation shows that the obtained composite powders have a porous structure, which is very useful for biomedical applications. The spherical nanoparticles in the range of 60 to 800 nm are embedded in the agglomerated clusters of the prepared composite powders.
基金This work was supported by the Ford-China Research and Development Fund (No.9415311).
文摘Nano silica-modified epoxy resins were synthesized by the sol-gel process, The materials have the morphological structure of nano particales dispersed in the epoxy matrix. The dispersed phase formed a physical network in the resin and thus influenced the rheological behavior greatly. However, the nano silica did not show a significant influence on the mechanical properties of the cured resins.
基金Funded by the Guangdong Well-Silicasol Company Limited,China
文摘An effective and reproducible preparation of silica sol nanospheres via a modified sol-gel process has been described. Monodisperse and stable silica sol nanospheres with uniformsize were successfully obtained through the optimized synthesis in which the mixture of tetraethyl orthosilicate （TEOS） and ethanol was followed by the addition of water and ammonium hydroxide （NH3） separately, and the size of silica sol spheres was strictly controlled in the range of 25-119 nm with a narrow size distribution by fine adjustment of several reaction parameters. Results showed that in the presence of low concentration of TEOS, spheres size rose first and reached maximum when H2O concentration was up to 66 g/L. However, the diameter of silica sol spheres decreased above 66 g/L of H2O concentration. Furthermore, it was also found that the size and size distribution of silica sol nanospheres were affected by NH3 concentration. As NH3 concentration increased from 15 to 35 g/L, the diameter declined from 83 to 64 nm. Nevertheless, higher NH3 concentration would result in relatively broad size distribution, and gelation occurred when NH3 concentration reached 44 g/L. In addition, the effect of the different feed rates ofNH3 on the size growth of silica sol nanospheres was also discussed.
文摘The nanocrystalline TiO_2 powder were prepared by improved sol-gel method at low temperature under ambient pressure. The prepared TiO_2 powder was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM). It is found that the yield of anatase TiO_2 significantly increases with the reduction of pH by increasing the nucleation rate of anatase. There is an optimum amount of water in sol for the formation of anatase by combining two effects on the concentration of Ti(OH)_4 in gels. Increasing in reaction temperature also benefit to the nucleation of anatase of TiO_2.
基金supported by LOEWE-Zentrum AdRIA for financial and Claudia Fasel for the thermal analysis
文摘Lead-free （Na0.sK0.5）Nb03 （NKN） thin films were fabricated by spin coating on Pt/Ti/SiO2/Si substrates by a diol-based sol-gel process. Na-acetate, K-acetate, Nb-pentaethoxide and 1,3 propanediol were used to prepare the NKN precursor solution. Thermal analysis showed two characteristic temperatures of 360 and 600℃. Based on these temperatures, a heat treatment program with pyrolysis at 360℃ and calcination at 600℃ after every layer was used. To avoid inhomogeneities and secondary phases, an excess of sodium and potassium was necessary. To evaluate the proper excess amount of sodium and potassium secondary ion mass spectrometry （SIMS） lateral element maps and X-ray diffraction （XRD） patterns were recorded. An excess amount of 20% led to homogeneous distribution of the elements and to single phase perovskite NKN films with random crystal orientation. Scanning electron microscopy （SEMI images showed a pore free surface with 100 nm grains. The leakage current measurements showed a current of lx10-3 A/cm2 at 150 kV/cm.
基金Project supported by the Key Laboratory of Novel Thin Film Solar Cells, Chinese Academy of Sciences (Grant No. KF201101)the Key Science Foundation of Higher Education Institutions of Anhui Province, China (Grant Nos. KJ2011A053 and KJ2012Z034)the National Natural Science Foundation of China(Grant Nos. 51202005, 11204005, and 41075027)
文摘Electrical transport and thermoelectric properties of Ni-doped YCOl-xNixO3 （0 ≤ x ≤0.07）, prepared by using the sol-gel process, are investigated in a temperature range from 100 to 780 K. The results show that with the increase of Ni doping content, the values of DC resistivity of YCo 1-xNixO3 decrease, but carder concentration increases. The temperature dependences of the resistivity for YCOl-xNixO3 are found to follow a relation of lnp o, lIT in a low-temperature range （LTR） （T 〈- 304 K for x = 0; - 230 K 〈 T 〈- 500 K for x = 0.02, 0.05, and 0.07） and high-temperature range （HTR） （T 〉-655 K for all compounds）, respectively. The estimated apparent activation energies for conduction Eal in LRT and Ea2 in HTR are both found to decrease monotonically with doping content increasing. At very low temperatures （T 〈-230 K）, Mott＇s law is observed for YCOl-xNixO3 （x≥ 0.02）, indicating that considerable localized states form in the heavy doping compounds. Although the Seebeck coefficient of the compound decreases after Ni doping, the power factor of YCOl-xNixO3 is enhanced remarkably in a temperature range from 300 to 740 K, i.e., a 6-fold increase is achieved at 500 K for YCo0.98Ni0.0203, indicating that the high-temperature thermoelectric property of YCoO3 can be improved by partial substitution of Ni for Co.
文摘The ultrafine powders of YBa2Cu3O7-x with the size of 100nm were synthesized by Sol-Gel process using cit-rate as complex and ammonium hydroxide to adjust pH of solu-tion. The process of Sol formation and Gel polymerization of YBa2Cu3O7-x in the Sol-Gel synthetic reaction has bee studied. The particle size ,pruity, sintering activity and superconducting properties of YBa2Cu3O7-x prepared by Sol-Gel method are better than by solid state reaction.
文摘Bi-substituted dysprosium iron garnet films were prepared by sol-gel process, and were annealed for crystallization. The crystallographic structures of garnet films annealed at different temperatures were analyzed by XRD, the film annealed at 650℃ was polycrystalline garnet with no preferred orientation and no impurity crystalline phase. Magnetic and magneto-optical properties were investigated, the film had magnetic anisotropy perpendicular to the film plane, and exhibited strong coercivity of 1100-1600 Oe and high squareness. These films had large figures of merit applicable to magneto-optic storage, with 2 deg. at λ=430 nm and 1.5 deg. at λ=520 nm respectively.
基金Project supported by the Anhui Provincial Science Key Foundation of Higher Education Institutions,China(Grant No.KJ2011A053)the National Natural Science Foundation of China(Grant No.51202005)
文摘Mn substitution compounds YCOl-xMnxO3 （0 ≤ x ≤ 0.2） are synthesized by using the sol-gel process. Electrical transport properties of YCo1-xMnxO3 are investigated in the temperature range from 200 K to 780 K. The experimental results show that after Mn substitution the electrical resistivity of YCo1-xMnxO3 first increases, then decreases, which is due to the electrons introduced by Mn doping. The sign of Seebeck coefficient for YCo1-xMnxO3 （x ≠ 0） is positive or negative, which is also proved by the Hall coefficient measurement. Moreover, at about room temperature, the Seebeck coefficient of YCO1-xMnxO3 with 1% doping Mn content becomes a negative value, whose absolute value is maximum; furthermore, the absolute value gradually decreases with increasing the Mn substitution content, which can be explained by the double carder model.
