微波辅助sol-gel法合成Bi_(0.5)Na_(0.5)TiO_(3)粉体及其压电性能研究

采用微波辅助溶胶-凝胶(sol-gel)法制备Bi_(0.5)Na_(0.5)TiO_(3)(BNT)粉体,通过DSC/TG,XRD,SEM,FT-IR等表征方法,分析BNT的反应历程,煅烧温度对BNT成分、晶粒尺寸和压电性能的影响.结果表明,当微波煅烧温度为650℃时,可合成出高纯度BNT粉体(30~120 nm),其居里温度为394℃,d_(33)=7.5 pC/N,ε_(r)=535.58,tanδ=0.29.对比传统马弗炉煅烧sol-gel法,微波辅助sol-gel法有利于提高BNT的介电性能和居里温度,降低介质损耗.

Development of Modified Glasses by Transparent, Functional Hybrid Sol-Gel Nano-Ceramic Coatings, a Comparative Study

This paper concentrates on the development of glasses with self-cleaning surfaces exhibiting high water contact angles. In this study, we prepared super-hydrophobic nano-ceramic coated glass based on titania & silica using simple sol-gel & dip coating methods and studied the best composition of the coatings by altering ratios of titanium tetraisopropoxide (TTIP)/tetraethyl orthosilicate (TEOS) with different homogenizing agents. We characterized the coatings by surface roughness measurement, percentage of optical transmission, static contact angle, near-infrared (NIR) transmission, and diffuse reflectance. The fabrication of coatings on glass substrates played an important role in increasing the water contact angle of about 95° and visible & NIR transmission of about 90%. We compared our modified glass substrate with commercial low emissivity (Low E) glass using X-ray diffraction (XRD) analysis, which showed pure amorphous surface claiming excellent wettability and thus the prepared glass substrate could have a variety of applications in different fields.

Fabrication and Characterization of LiFePO4 Nanotubes by a Sol-gel-AAO Template Process

采用溶胶凝胶法在氧化铝模板中成功的制备了LiFePO4一维纳米管阵列．扫描电子显微镜和透射电子显微镜表征结果表明所制备的LiFePO4纳米管具有单分散性,互相平行,高度有序。综合选区电子衍射、X射线衍射以及X光线能谱表征结果,所制备的LiFePO4纳米管为单一的橄榄石型结构．这种在室温和温和条件下合成的一维LiFePO4纳米管,可以做为新型的锂离子电池正极材料．

SYNTHESIS OF MESOPOROUS POLY(STYRENE-co-MALEIC ANHYDRIDE)/SILICA HYBRID MATERIALS VIA A NONSURFACTANT-TEMPLATED SOL-GEL PROCESS

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.

Preparation of layered oxide Li(Co_(1/3)Ni_(1/3)Mn_(1/3))O_2 via the sol-gel process

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.

Synthesis and Characterization of Cerium-Doped Lutetium Aluminum Garnet Phosphors by Nitrate-citrate Sol-Gel Combustion Process

Nanosized cerium-doped lutetium aluminum garnet （LuAG：Ce） phosphors were prepared by nitrate-citrate solgel combustion process using 1：1 ratio of the citrate：nitrate. The prepared LuAG：Ce phosphors were characterized by XRD, TEM, photoluminescence and radioluminescence spectra excited by UV and X-ray, respectively. The purified crystalline phase of LuAG：Ce was obtained at 900 ℃ by directly crystallizing from amorphous materials. The resultant Lu- AG：Ce phosphors were uniform and had good dispersivity with an average particle size of about 30 urn. Both photoluminescence and radioluminescence were well-known Ce^3＋ emissions located in the range of 470 -600 nm consisting of two emission bands because of the transition from the lowest 5d excited state （2D） to the 4f ground state of Ce^3＋, which matched well with the sensitivity curve of the Si-photodiode. There was a little red shift for the emission components from the UV-excited emission spectrum to the X-ray-excited emission spectrum. The fast scintillation decay component of 26 ns satisfies the requirements of fast scintillators.

Methane reforming with CO_2 to syngas over CeO_2-promoted Ni/Al_2O_3-ZrO_2 catalysts prepared via a direct sol-gel process

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.

Mechanism of Phase Transformation and Formation of Barium Hexafer rite Doped with Rare-Earths in Sol-Gel Process

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.

Preparation and characterization of BaMgAl_(10)O_(17)∶Eu phosphor coated with MgF_2 by sol-gel process

In order to prevent BaMgAl10O17∶Eu （BAM） phosphor from thermal degradation, MgF2-coatings on the surface of BAM were prepared by a sol-gel process. The coatings were characterized by X-ray photoelectron spectroscopy and scanning electron microscopy. The results indicate that BAM is successfully coated with homogenous, close MgF2 coatings. The photoluminescence and anti-thermal degradation properties of coated BAM were investigated under 254 and 147 nm excitations. The optimum anti-thermal degradation properties are obtained at the mass ratio of MgF2 to BAM 0.2% under 254 nm excitation and 0.5% under 147 nm excitation, respectively. It is considered that trace MgO formed after baked would cause different optimum coating thicknesses under 254 and 147 nm excitations.

Microstructure and electrical properties of La_2 O_3-doped ZnO-based varistor thin films by sol-gel process

Microstructure and electrical properties of La2 O3-doped ZnO-Bi2 O3 thin films prepared by sol–gel process have been investigated.X-ray diffraction shows that most diffraction peaks of ZnO are equal,and the crystals of ZnO grow well.Scanning electron microscopy and atomic force microscopy results indicate that the samples have a good structure and lower surface roughness.The nonlinear V–I characteristics of the films show that La2 O3 develops the electrical properties largely and the best doped content is 0.3% lanthanum ion,with the leakage current of 0.25 mA,the threshold field of 150 V/mm and the nonlinear coefficient of 4.0 in detail.

Production of HfO_2 thin films using different methods: chemical bath deposition, SILAR and sol–gel process

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.

SYNTHESIS AND OPTICAL PROPERTIES OF A NOVEL ORGANIC/INORGANIC HYBRID NONLINEAR OPTICAL POLYMER VIA SOL-GEL PROCESS

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.

PREPARATION AND SECOND-ORDER OPTICAL NONLINEARITY OF NOVEL PHENOXYSILICON NETWORKS BY SOL-GEL PROCESS

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.

Structure and Luminescence Properties of Eu^(3+) Doped SiO_2 Glass Synthesized by Sol-Gel Process

Under different annealing temperatures, Eu 3+ doped SiO 2 gel and glass were prepared by sol gel method, and the structure and luminescent properties were studied with excitation spectra, emission spectra, IR and DTA TG. The results show that the fluorescent intensity tends to get stable when concentration of Eu 3+ doped is above 1 86 % (mass fraction) most water absorbed by the gel was removed at 300 ℃, and that the emission spectrum of Eu 3+ , with peaks at 614, 588, 577 nm, is due to 5D 0→ 7F 2, 5D 0→ 7F 1, 5D 0→ 7F 0 transitions, and the excitation peaks at 318, 362, 380, 393, 412 and 462 nm were observed. These results illustrate that the temperature range of 300～500 ℃ is critical for the structure conversion from gel to glass, and the fluorescence is strongly quenched by water.

Growth of TiO_2 Nanorods by Sol-gel Template Process

In this work, TiO2 nanorods with uniform diameter of about 100 nm and a length of several micrometers were successfully prepared by the sol-gel template method. Also the influence of molar ratios of precursor on the morphology and structure of TiO2 nanorods has been investigated. The prepared samples were characterized by Fourier transform infrared spectroscopy （FTIR）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The XRD results indicated that the TiO2 nanorods were crystallized in the anatase and rutile phases, after annealing to 400-700℃ up to 2 h.

Preparations of TiO_2 film coated on foam nickel substrate by sol-gel processes and its photocatalytic activity for degradation of acetaldehyde

Anatase TiO2 films were successfully prepared on foam nickel substrates by sol-gel technique using tetrabutyl titanate as precursor. The characteristics of the TiO2 films were investigated by XPS, XRD, FE-SEM, TEM and UV-Vis absorption spectra. The photocatalytic activities of TiO2 films were investigated by photocatalytic degradation reactions of gaseous acetaldehyde, an indoor pollutant, under ultraviolet light irradiation. It was found that Ni^2＋ doping into TiO2 films due to the foam nickel substrates resulted in the extension of absorption edges of TiO2 films from UV region to visible light region. The pre-heating for foam nickel substrates resulted in the formation of NiO layer, which prevented effectively the injection of photogenerated electrons from TiO2 films to metal nickel. The TiO2 films displayed high photocatalytic activity for the degradation of acetaldehyde, and were enhanced by calcining the substrates and coating TiO2 films repeatedly. The high activity was mainly attributed to the improvement of the characteristics of substrate surface and the increase of active sites on photocatalyst.

Luminescent Properties of Y_2O_3∶Eu Nanocrystalls Synthesized by EDTA Complexing Sol-Gel Process

Y 2O 3: Eu nanocrystals were synthesized by EDTA complexing sol gel process at a relatively low temperature, in which ethylen diamine tetraacetic acid (EDTA) and polyethylene glycol (PEG) were used as the chelating agent and polymerization agent respectively. Formation process of Y 2O 3:Eu and structure characterization were carried out by TG DTA, XRD, SEM/EDX. The results show that pure cubic phase Y 2O 3: Eu nanocrystalsere is produced after the precursor calcinated at 600 ℃ for 2 h, and the crystallinity increases with increasing calcination temperature. The nanoparticles of the Y 2O 3: Eu are basically spherical in shape. The mean particle size increases from about 30 to 70 nm when the calcination temperature increases from 600 to 1000 ℃. The luminescent properties of phosphor were analyzed by measuring the excitation and emission spectra. The main emission peak of the sample is around 612 nm, resulting in a red emission. The emission intensity increases with the calcination temperature. Compared with microsized Y 2O 3: Eu phosphors prepared by a conventional method, nanosized Y 2O 3: Eu synthesized by the present work, gives and a clear red shift in the emission spectrum. Moreover, the quenching concentration of Eu is raised.

Preparation of LiTi_2(PO_4)_3 by the Sol-gel Method and Investigation of Its Formation Process

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Preparation Process of Plumbagin Nanomicelle In-situ Gel

[Objectives]To prepare plumbagin nanomicelle(PLB-N)in-situ gel,and optimize the formulation and process.[Methods]PLB-N was prepared by self-assembly method,and the optimal formulation of PLB-N in-situ gel was determined by orthogonal experiment design and single factor method.[Results]The optimal preparation process for PLB-N was a drug to lipid ratio of 1:3,a Tween 80 content of 5%,an ethanol content of 7.5%of the hydration medium,a magnetic stirring speed of 2200 rpm,a stirring time of 30 min,and an ultrasound time of 10 min.The optimal formulation of PLB-N in-situ gel was 22%of poloxamer 407,6%of poloxamer 188,and 1:1 of PLB-N to water.The encapsulation efficiency of PLB-N prepared with the optimal formula was(95.8%±0.4%),and the average particle size was(75.19±1.14)nm,and the Zeta potential was(-20.73±1.19)mv.[Conclusions]PLB-N in-situ gel had stable and reliable preparation process,uniform content,and broad application prospects.