Sol-gel法制备NiZnCu铁氧体性能的研究

采用溶胶-凝胶自燃法制备了Ni0.4Zn0.4Cu0.2Fe2O4铁氧体,使用HP4191A阻抗分析仪测试了材料高频磁谱;结合快速热处理(RTP)工艺制备了Ni0.4Zn0.4Cu0.2Fe2O4磁性薄膜,使用AFM、XRD、AGM系统地研究了制备工艺对薄膜样品表面形貌、晶相结构和准静态磁性的影响。测试结果表明:Ni0.4Zn0.4Cu0.2Fe2O4可适用于射频领域,截止频率fr在1GHz以上,1GHz处起始磁导率μ′=5.3,μ″=3.45;sol-gel法制备磁性薄膜最佳晶化温度为600℃左右,在此温度下制备的薄膜晶粒大小为13nm左右,饱和磁化强度Ms=2.29×105A/m,矫顽力Hc=1.24×103A/m。     

Second-order nonlinear optical properties of cross-linked silica films prepared through sol-gel process

In this paper, second-order NLO chromophores containing two reactive sites have been synthesized and characterized by ¹H NMR, FTIR and elemental analysis. The transparent films have silica network of matrix and covalently bonded chromophore of NLO segment were then fabricated via sol-gel process. The SHG coefficients (d₃₃) of the poled films were calculated to be around 50 pm/V by in situ second harmonic generation (SHG) measurement. The thermal stability of the NLO coefficient was investigated by the depoling experiment and temporal decay test, showing that the cross-linked films had a good thermal stability up to 160 °C.     

Iron oxide in a silica matrix prepared by the sol-gel method

Fe_xO_y-SiO₂ nanocomposites were prepared by sol-gel method by using two SiO₂ sources and Fe(SO₄)₂·7H₂O as raw materials. The amorphous gels were thermally treated up to 1000 °C. The initial gel and the thermally treated samples were characterized by thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA) and infrared spectroscopy. The presence of hematite was confirmed by the obtained Mössbauer spectra which showed the characteristic sextet. The total amount and the size distributions of the hematite nanoparticles can be controlled via the initial precursors and subsequent by annealing conditions.     

溶胶-凝胶法有机-无机杂化材料的制备及应用研究进展

介绍了溶胶-凝胶法制备有机-无机杂化材料的原理、分类和制备方法,对杂化材料性能研究的表征手段和应用领域进行了简要的论述,这类性能优异的新材料在未来的高科技领域,具有广阔的应用与开发前景。     

Crystal modulation of tungsten oxide gels and films prepared by the sol-gel process using 2,4-pentanedione as an organic ligand

Tungsten oxide gels and films were prepared by the sol-gel process using 2,4-pentanedione (PTN) as an organic ligand. WO₃ powders were obtained by peeling the films from the quartz glass substrates. The crystal structure of both the gels prepared with and without PTN and fired at 700 °C was monoclinic. WO₃ powders peeled from film samples prepared both with and without PTN showed only the monoclinic crystal structure, whereas the crystal phases of both types of films were cubic and a mixture of cubic and monoclinic crystals, respectively. These results indicate that the cubic crystals of the WO₃ in the films were transformed to the monoclinic crystals of the powders after the films were peeled from the quartz glass substrates. It is concluded that the cubic crystals in the films are transformed to stable monoclinic crystals by the peeling process, whereas PTN and the quartz glass substrate can control the crystal phase of WO₃ films selectively to form the cubic structure.     

Fabrication and characterisation of neodymium-doped silica glass by sol-gel process

 Neodymium-doped silica glass possesses many properties ideal for high-power laser applications. These include low thermal expansion coefficient, high temperature stability, and low nonlinear index of refraction. For the first time, the sol-gel process has been successfully employed to prepare highly doped neodymia silica glass, up to 5wt% Nd for homogeneous dopant distribution. The optical characteristics of the silica glass and its in-process gel, including the UV/VIS absorption spectra, infrared absorption spectra, fluorescence emission spectrum and the fluorescence lifetime, are measured and analyzed. The structure of the sample is also characterized by means of XRD and SEM. A porous gel is observed to have formed when the heat treatment temperature reaches 300^oC. Wavelength shifts in the absorption peak corresponding to the ⁴I_9/2 to ⁴F_5/2 transition have been observed during the densification process and for different Nd weig ht contents. The FTIR spectra have shown that high temperature heat treatment can greatly reduce the amount of OH groups and organic residue in the silica. We have also shown that a high OH content contributes to weak fluorescence intensity and short fluorescence lifetimes. Received: 3 March 1997 / Accepted: 27 May 1997     

溶胶-凝胶法制备镁蔷薇辉石的体外生物活性研究

用溶胶-凝胶法制备出纯相镁蔷薇辉石(Ca3MgSi2O8)粉体,并在10MPa的轴向压力下,将其压制成尺寸为Ф10mm×5mm的圆柱状块体,通过模拟体液浸泡对其体外生物活性进行研究.用X射线衍射(XRD)及扫描电镜(SEM)分别对粉体以及浸泡后形成的羟基磷灰石(Hap)的物相和表面形貌进行表征.结果表明:在约1400℃的煅烧温度下可以得到纯相镁蔷薇辉石粉体,其粒径约为1～3μm;圆柱状镁蔷薇辉石在模拟体液浸泡7d后就能明显检测到表面有羟基磷灰石生成,浸泡14d后呈结晶较好的蠕虫状结构.因此,溶胶-凝胶法合成的镁蔷薇辉石具有良好的诱导羟基磷灰石形成能力和体外生物活性.     

Comparison of some properties of neodymium-doped silica glasses prepared by sol-gel and melting

Samples with 10Nd₂O₃·5CaO·17Al₂O₃·68SiO₂ composition (mol %) were prepared by the sol-gel method and by melting. The structure of the samples was investigated by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, a.c. susceptibility measurements and electron spin resonance. The gel-derived sample heat-treated between 250 and 700°C is amorphous and has a granular microstructure. In the samples heat-treated at 800, 900 and 1000°C we detected by X-ray diffraction AlNdO₃ crystalline particles. The melted sample was amorphous and the micrograph shows a glass matrix containing particles. The infrared measurements show structural changes produced by the heat-treatment of the gel samples. The magnetic susceptibility data indicates that neodymium oxide is present in these samples as Nd³⁺-O-Nd³⁺ aggregates with an antiferromagnetic interaction.     

Preparation of silica particles by sol-gel process in reverse suspension

Sol-gel process of silicon alkoxide was performed in reverse suspension to limit the sites of hydrolysis and dehydration-condensation of alkoxide to the inside of the dispersed droplets and to prepare silica particles of tens m in diameter. Acetic acid aqueous solution was used as a dispersed phase, and hexane as a continuous phase. The dispersed phase was poured into the continuous phase, in which silicon alkoxide has dissolved, with stirring to form a reverse suspension. Silica particles of 67 m in mean diameter were obtained by calcining the gel particles produced. Effects of pH of the dispersed phase and concentration of dispersion stabiliser on the characteristics of the silica particles were discussed. The formation mechanism of the gel particle was inferred with applying Jander's model, which is often used to analyse solid phase reaction of particles.     

Chemically L-phenylalaninamide-modified monolithic silica column prepared by a sol-gel process for enantioseparation of dansyl amino acids by ligand exchange-capillary electrochromatography

A new type of chiral monolithic column was successfully developed for the enantioseparation of dansyl amino acids by ligand exchange-capillary electrochromatography (LE-CEC) in this work. The monolithic column matrix was prepared by a sol-gel process and then chemically modified with the spacer (3-glycidoxypropyl)trimethoxysilane and the chiral selector L-phenylalaninamide. After being conditioned with Cu(II) aqueous solution, the ligand exchange-chiral stationary phase (LE-CSP) possesses positive charges. When the external electric field was applied in CEC, electroosmotic flow (EOF) was generated on the surface of LE-CSP in the direction from the cathode to the anode. The EOF was found to be dependent on the applied electric field strength and the composition of the mobile phase. With the increase of pH of the mobile phase, the EOF showed a tendency to decrease. Scanning electron microscopy showed that the chiral monolithic column has a continuous skeleton and large through-pore structure. The separation efficiency (theoretic plate numbers) for the separation of Dns-DL-Leu reached up to 9.0 x 10(4) plates m(-1) for the D-enantiomer and 6.6 x 10(4) plates m(-1) for the L-enantiomer, by using pH 5.5, acetonitrile/0.50 mM Cu(Ac)2-50 mM NH4Ac (7:3) as mobile phase. The reproducibility and lifetime were satisfactory. CEC was carried out with conventional capillary electrophoresis equipment without pressurizing the ends of the capillary. No bubble was formed during the operation, after degassing the mobile phase and conditioning the column.     

Thermo-luminescence induced by gamma irradiation in sol-gel prepared zirconia–silica materials

Zirconia–silica materials prepared by the sol-gel method at different compositions were gamma irradiated with a dosage of 40 Krads for different irradiation periods. The thermoluminescent (TL) emission was studied as a function of the zirconia for temperatures from 100 to 300 °C. Pure zirconia produces a strong TL signal, followed by 50% zirconia sample, while pure silica and the 5% zirconia sample show a weak TL signal. This means that there exists a self-inhibited process possible due, on the one hand to the segregation effects of both components, and on the other to the stabilization of either tetragonal or monoclinic zirconia phases. This effect opens the possibility to control the TL signal in a wide range of dosages allowing to use this system as a wide range dosimeter. Received: 2 February 2000 / Reviewed and accepted: 10 June 2000     

Composite formation of Thiol-capped Au nanoparticles and mesoporous silica prepared by a sol-gel method

We have previously reported the fabrication of a nanocomposite from dodecanethiol-capped Au nanoparticles (average diameter 2.6 nm) and a silica aerogel. It was found that the Au particles were efficiently adsorbed on a silica wet-gel in organic solvents. In this paper, surface analysis of the silica surface and evaluation of adsorption rates for various solvents, performed to elucidate the nature of the interaction between the capped nanoparticles and the silica gel, are described. These observations indicate that dipole-induced dipole interaction between OH groups on the silica surface and metal cores of the nanoparticles is probably important for the adsorption. It was demonstrated that, by changing the solvent polarity, spatial distribution of the nanoparticles inside the gel can be controlled.     

溶胶-凝胶法制备连续莫来石纤维先驱凝胶DSC-TG-MS分析

以正硅酸乙酯(TEOS)、异丙醇铝(AIP)和硝酸铝(AN)等为原料,用溶胶-凝胶(sol-gel)法制备连续莫来石纤维.利用热分析与质谱联用(DSC-TG-MS)分析研究了莫来石纤维先驱凝胶在热处理过程中的化学反应、物相变化.     

ZnO thin films prepared by a single step sol-gel process

ZnO thin films were prepared on fused silica from a single spin-coating deposition of a sol-gel prepared with anhydrous zinc acetate [Zn(C₂H₃O₂)₂], monoethanolamine [H₂NC₂H₄OH ] and isopropanol. Crystallization annealing was performed over the range 500 to 650 °C. X-ray analysis showed that thin films were preferentially orientated along the [002] c-axis direction of the crystal. The films had a transparency of greater than 85% in the visible region for sol-gels with a zinc content of up to 0.7 M and exhibited absorption edges at ∼ 378 nm. The optical band-gap energy was evaluated to be 3.298-3.306 eV. Photoluminescence showed a strong emission centered at ca. 380 nm along with a broad yellow-orange emission centered at ca. 610 nm. Single step sol-gel thin film deposition in the film thickness range from 80 nm to 350 nm was demonstrated. The effect of sol-gel zinc concentration, film thickness and crystallization temperature on film microstructure, morphology and optical transparency is detailed. A process window for single spin coating deposition of c-axis oriented ZnO discussed.     

Alcohol sensing of tin oxide thin film prepared by sol-gel process

The present paper describes the alcohol sensing characteristics of spin coated SnO₂ thin film deposited by using sol-gel process. The sensitivity of the film was measured at different temperatures and different concentrations of alcohol at ppm level. Alcohol detection result shows peak sensitivity at 623 K. The variation of sensitivity and ethanol concentration has shown a linear relationship up to 1150 ppm and after that it saturates. The response time measurement of the sensor was also observed and it was found that the response time is 30 sec. The results obtained favour the sol-gel process as a low cost method for the preparation of thin films with a high sensing characteristic.