无机盐和有机醇盐制备Al2O3干凝胶

分别以廉价的硝酸铝无机盐常压干燥法和异丙醇铝有机醇盐作为铝源,采用溶胶-凝胶法制备了结构完整的SiO2-Al2O3干凝胶和纯Al2O3干凝胶.利用热重差热分析、Fourier转换红外吸收谱、氮气吸附和电子显微镜等实验手段,对比研究了曲种制备方法对材料性能的影响.结果表明:由无机盐制备的SiO2-Al2O3干凝胶是以SiO2构成网络骨架,形成一定数量的Si-O-Al键,并保持了干凝胶纳米多孔的特点;而有机醇盐制备的Al2O3干凝胶孔隙分布更为均匀.采用两种不同铝源制备的干凝胶,均是纳米颗粒组成的多孔结构,并均具有较高的比表面积和较窄的孔径分布.     

In3+离子在多孔SiO2干凝胶中的发光

采用常规的Sol-gel工艺合成了In^3 掺杂的多孔SiO2干凝胶，In^3 离子作为间隙离子存在于SiO2网络中，展示了一种新颖的发光现象，改变了多孔SiO2干凝胶的发射光谱。这种掺杂的多孔SiO2干凝胶的激发和发射光谱均由2个带组成，短波长的发光峰在440nm(λex=380nm），其相对荧光强度约是未掺杂的多孔SiO2干凝胶的4倍；长波长的发光峰（In^3 离子在多孔SiO2干凝胶的特征发射）在600nm(λex=476nm），其相对荧光强度约是In^3 掺杂ZnS纳米晶的10倍。由此可以看出：掺杂的多孔SiO2干凝胶是一种高效的发光材料。     

利用原子力显微镜研究聚酰亚胺／纳米SiO2复合材料

通过均苯四甲酸二酐与4，4’-二氨基二苯基醚缩聚反应制备了聚酰胺酸（PAA）。采用溶胶-凝胶法和超声波机械共混法制备了不同纳米SiO2含量的PAA／纳米SiO2共混胶液，经高温亚胺化得到聚酰亚胺（PI）／纳米SiO2复合材料。利用原子力显微镜（AFM）对PI／纳米SiO2复合材料与杜邦公司的KAPTON耐电晕复合材料及其电晕试验后的复合材料进行了表面形貌、结构和性能比较。结果表明，溶胶-凝胶法和超声波机械共混法制备的PI薄膜中的无机相是无定形的，而KAPTON薄膜中的无机相是缨束状的，具有取向的微观结构。超声波机械共混法具有很好的分散作用，而其有机相与无机相之间结合力较溶胶-凝胶法弱。     

超低介电常数聚芳酯薄膜的制备及其性能研究

为制备超低介电常数的聚芳酯薄膜，以双酚A(BPA)、对苯二甲酰氯(TPC)和间苯二甲酰氯(IPC)为单体用界面聚合法合成无定形聚芳酯(a-PAR);并采用相分离法制备多孔聚芳酯薄膜；采用扫描电子显微镜、差示扫描量热仪和万能材料试验机等探讨了凝固浴组成对多孔膜结构及其性能的影响。结果表明多孔膜的孔隙率随凝固浴中水含量的上升而提高，其介电常数发生显著下降(最低可达1.27),同时伴随着薄膜力学性能的下降。控制凝固浴组成可调节聚芳酯薄膜的孔隙率，从而制备具有一定力学强度的超低介电常数聚芳酯薄膜。当凝固浴中水含量为20%时，薄膜的拉伸强度为13.0 MPa,弹性模量为0.29 GPa,玻璃化转变温度为198.1℃,介电常数为1.51,综合性能最佳。     

浙江华晶650吨电子氟化学品项目进展

厦门大学材料学院日前研制出纳米多孔超轻质高效隔热SiO2气凝胶材料。该材料阻燃性好，高温使用不分解，可有效解决传统保温隔热材料不能解决的问题。SiO2气凝胶可以制备成粒状、粉末状、板状以及柔性薄膜等。该材料用于太阳能热水器的储水箱、管道和集热器上，可将现有太阳能热水器集热效率提高1倍以上，而热损失将降至现有水平的30％。该材料具有极高的孔隙率、比表面积，极低的密度、声传播速度、介电常数等优异性能。     

厦大研制高效隔热纳米多孔SiO2气凝胶

厦门大学材料学院日前研制出纳米多孔超轻质高效隔热SiO2气凝胶材料。该材料阻燃性好，高温使用不分解，可有效解决传统保温隔热材料不能解决的问题。SiO2气凝胶可以制备成粒状、粉末状、板状以及柔性薄膜等。该材料用于太阳能热水器的储水箱、管道和集热器上，可将现有太阳能热水器集热效率提高1倍以上，而热损失将降至现有水平的30％。该材料具有极高的孔隙率、比表面积，极低的密度、声传播速度、介电常数等优异性能。     

纳米多孔二氧化钛薄膜的制备及其亲水性能的研究

分别采用溶胶-凝胶法,水热合成法,热雾喷解法制备了纳米多孔TiO2薄膜。以X射线衍射,扫描电镜等方法分析了不同制备方法所得薄膜结构与形貌。通过比较不同方法制备的TiO2薄膜的亲水性能,得知溶胶—凝胶法制备的薄膜和玻璃载体结合最紧,而且表面平整。热雾喷解法制备的薄膜具有最大的比表面积,其亲水性能也最好。同时表明,纳米多孔TiO2薄膜在紫外光照射以后,具有比一般薄膜更持久的亲水型。     

太阳能电池用减反射膜的制备及性能

采用溶胶-凝胶法制备出纳米多孔SiO2减反射薄膜样品,考察了薄膜制备工艺对其透过率的影响,并用紫外-可见分光光度计对薄膜的光学特性进行表征。研究结果表明,乙醇-盐酸溶液滴入乙醇-正硅酸乙酯溶液、陈化4天、正硅酸乙酯∶乙醇∶水摩尔比为1∶20∶4,单层SiO2膜具有较好的减反射效果,最大透过率可提高4%。     

TiO2纳米晶多孔薄膜太阳能电池的制备

利用溶胶-凝胶法制备TiO2纳米晶多孔薄膜，采用天然染料作为光敏化剂，采用I^-和I^3-作为电解质来制备太阳能电池。     

Ba(Zr0.3Ti0.7)O3薄膜的结构及性能

用溶胶-凝胶法分别在Pt/Ti/SiO2/Si和LaNiO3/Pt/Ti/SiO2/Si衬底上制备了锆钛酸钡[Ba(Zr0.3Ti0.7)O3,BZT]薄膜.相结构及介电性能研究表明:衬底和薄膜厚度对BZT薄膜性能具有显著影响.制备在LaNiO3/Pt/Ti/SiO2/Si衬底上的BZT薄膜具有(100)面的择优取向,其介电常数及介电损耗则随着薄膜厚度的增加而降低.对制备在Pt/Ti/SiO2/Si衬底上的BZT薄膜,在薄膜厚度低于500nm时,其介电常数随薄膜厚度增加而增加,大于500nm时又有所减小.     

Structure and dielectric properties of polyimide/silica nanocomposite nanofoam prepared by solid‐state foaming

In this article, polyimide (PI)/silica nanocomposite nanofoams were prepared by solid‐state foaming using supercritical CO₂ as foaming agent. To control the cell size and morphology of the PI/silica foam, the silica nanoparticles as nucleating agent were in situ formation from TEOS via sol‐gel process, which make the silica nanoparticles homogeneously dispersed in PI matrix. The resulting PI/silica nanocomposite nanofoams were characterized by scanning electron microscopy (SEM), the image analysis system attached to the SEM and dielectric properties measurements. In PI/silica nanocomposite nanofoams, one type of novel morphology was shown that each cell contained one silica nanoparticle and many smaller holes about 20–50 nm uniformly located in the cell wall. This special structure could visually prove that the nucleation sites during foaming were formed on the surface of nucleating agents. Compared with those of neat PI foam, the cell size of PI/silica nanocomposite nanofoams was smaller and its distribution was narrower. The dielectric constant of PI/silica nanocomposite nanofoams was decreased because of the incorporation of the air voids into the PI/silica nanofoams. While the porosity of PI/silica nanocomposite nanofoam film was 0.45, the dielectric constant of the film (at 1 MHz) was reduced from 3.8 to about 2.6. Furthermore, the dielectric constant of PI/silica nanofoam films remained stable across the frequency range of 1×10²～1×10⁷ H_Z. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42355.     

Preparation of microstructure compatible porous supports by sol–gel synthesis for catalyst coatings

To enhance the inner surface of microchannel reactors, porous metal oxide coatings based on alumina, silica, and titanium oxide have been developed as support for catalytically active components. The oxides were made by the sol–gel process. Thin film coating was accomplished by dip coating using an Fe-based alloy as support. The influence of the sol composition, sol viscosity, and thermal treatment procedure on the surface enhancement factor and the porosity of the coating was investigated. The resulting surface enhancement factor reached 800 m²/m².     

Structural and Mechanical Properties of Nanoporous Silica

Nanoporous silica systems with porosity between 30% and 70% were developed using two Molecular Dynamics (MD) simulation protocols to obtain structures with dissimilar pore morphologies. Short‐ and medium‐range structural characteristics including bond angle distributions and pair distribution functions were analyzed and found to be consistent with experimental results. Surface area to volume ratio and pore microstructures were characterized and compared with experimental observations. Mechanical properties including elastic, shear, and bulk moduli of these nanoporous silica systems were calculated and their change as a function of porosity was compared with experimental data and theoretical models. It was found that the elastic modulus of porous silica with 50% porosity is 5–14 GPa which is consistent with experimental results. The elastic moduli–porosity relationship was fitted by exponential and power functions, and analysis of coefficients was performed to obtain microstructure characteristics of the simulated nanoporous silica structures. This works confirms that two distinct nanoporous silica microstructures are generated with MD simulations which result in variations in mechanical properties and highlight the importance of selecting a nanoporous silica simulation method which approximates experimental systems.     

Dependence of the dielectric constant on the fluorine content and porosity of polyimides

The trend toward miniaturization in integrated circuit fabrication demands good interlayer dielectric materials. This need can be met by polyimide (PI), which has extreme thermal and chemical stability and, most importantly, a low dielectric constant. Four porous PIs with symmetrically substituted fluorine contents were synthesized. Different porosity levels were achieved with a sol–gel technique through the incorporation of 10 or 20% tetraethyl orthosilicate into the polymer matrix and then acid etching. Their dielectric constants were correlated with the fluorine contents and porosity levels. High porosity levels and higher fluorine contents induced substantial decreases in the PI dielectric constants (2.4–2.7). The resultant values were within the applicable range for dielectric materials in integrated circuits. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A non-sintering fabrication method for porous Si3N4 ceramics via sol hydrothermal process

A non-sintering fabrication method for porous Si₃N₄ ceramics with high porosity and high mechanical strength was proposed. Strength of the porous ceramics can be obtained by silica sol mass transfer process in hydrothermal conditions rather than a traditionally controlled high temperature sintering process. Under hydrothermal circumstances, silica sol is continuously transferred to the necks of Si₄N₃ powder compact, depositing there and thus consolidating the ceramic skeleton. The key of the method to obtain homogeneous microstructure and mechanical strength is how to keep the silica sol from gelatin during hydrothermal procedure. The stabilization of silica sol and its affecting factors were studied. The results indicated that ultrasonic treatment makes alkali-catalyzed silica sol remain stable even in 200?℃ hydrothermal condition, which insures consecutive silica transportation. The effect of hydrothermal time on open porosity/mechanical strength of the porous Si₄N₃ ceramics were also thoroughly investigated. The porous Si₄N₃ ceramics with open porosity above 42% and flexural strength of 45?MPa were obtained without any high temperature sintering process. This method can be widely employed for the preparation of other porous ceramics as well.     

有序介孔二氧化硅薄膜的制备及性能

以十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯为无机前驱体,在酸性条件下,采用溶胶-凝胶技术,用蒸发诱导自组装(EISA)工艺制备了二氧化硅透明介孔薄膜. 透射电子显微镜图显示热处理后的薄膜具有高度有序的六方相结构孔道;由椭偏仪测得热处理后薄膜的折射率低至1.18,厚度在180 nm左右;阻抗分析仪测得薄膜的介电常数为2.14. 薄膜经过六甲基二硅胺烷(HMDS)表面修饰后具有良好的疏水性能和热稳定性,作为低介电材料能更好满足工业需求.     

Nanoporous titania interlayer as reservoir of corrosion inhibitors for coatings with self-healing ability

Active corrosion protection of AA2024-T3 alloy has been provided by an environmental-friendly, well adhering pre-treatment system consisting of an inhibitor-loaded titanium oxide porous layer and a sol–gel based thin hybrid film. A novel approach aimed at developing a nanoporous reservoir for storing of corrosion inhibitors on the metal/coating interface has been proposed. The nanostructured porous TiO₂ interlayer was prepared on the aluminium alloy surface by controllable hydrolysis of titanium alkoxide in the presence of template agent. The morphology and the structure of the TiO₂ film were characterized with TEM, EDS, SEM, and AFM techniques. Different ways of loading of the inhibitor in the pre-treatment coating were discussed. In contrast to direct embedding of the inhibitors into the sol–gel matrix, the use of the porous reservoir eliminates the negative effect of the inhibitor on the stability of the hybrid sol–gel matrix. TiO₂/inhibitor/sol–gel systems show enhanced corrosion protection and self-healing ability confirmed by EIS and SVET measurements.     

Effect of sol infiltrations on electrical properties of PZT

Abstract

Thin PZT films with a thickness of approximately 1 μm can readily be fabricated using a layered sol-gel deposition technique. The maximum thickness obtainable is limited by the time taken and the tendency of the films to crack and spall when many layers are deposited. Thicker layers may be obtained by depositing a powder-sol slurry whereby a PZT powder is mixed with a sol of approximately the same composition. Using this layered slurry deposition technique it is possible to obtain films with a thickness in excess of 20 μm. The resulting films, however, are often porous, leading to poor properties and making subsequent patterning difficult. A technique for increasing the density of such films through the use of controlled heat treatments and sol infiltration is presented. It is shown that with increased levels of sol infiltration the density and dielectric constant of the films are maximised. Measurements of piezoelectric properties indicate that sol infiltrations have no significant effect on d₃₃. A sample with approximately 10% closed porosity was obtained following four infiltration steps per layer. This resulted in a maximum dielectric constant of approximately 700 and a d₃₃ of 70 pC N ^-1 (poling conditions: 8 V μm ^-1 for 5 min at 200°C). Examination of cross-sections of the films produced shows that for intermediate levels of sol infiltration (typically between 1 and 3) a density gradient is obtained with higher densities observed nearer the base of the film. It is postulated that the observed density gradient is a result of continued infiltration from the upper layers when further layers of slurry are deposited. The effects of changing process variables such as the number of infiltration steps and firing temperature on film structure and properties are discussed.     

Synthesis of hierarchically nanoporous silica films for controlled drug loading and release

Films with well-controlled porous structures provide many exciting application opportunities in chemistry and biology. Here we report the synthesis of a highly uniform, hierarchically nanoporous silica film structure, and its application in drug loading and release for antibacterial surface coating. Templated by both sub-micron poly-styrene (PS) particles and a triblock copolymer (F127), this hierarchically nanoporous film has two distinct pore sizes of 200 nm and 7 nm. The 7-nm mesopores provide high surface area and thus high adsorption capacity for drug molecules, and the 200-nm macropores facilitate the adsorption rate of drug molecules, especially for molecules with comparable sizes to mesopores. Fluorescence measurement of rhodamine release demonstrates that this hierarchically porous film has a higher adsorption capacity, efficiency and much longer molecule releasing time window than both the inverse opal film and the mesoporous film. When loaded with Ampicillin, this hierarchically porous film shows over 8 times longer of inhibition of E. coli growth than both the inverse opal film and the mesoporous film. This simple and versatile process allows for fabrication of a variety of surface-coated, hierarchically nanoporous films with different chemical compositions and applications.     

New approach for the preparation of nanoporous polyorganosilicate low‐k films

The distribution of pores and the mechanical properties of materials are the key factors in preparing satisfactory low‐k films. In the present study, a kind of silsesquioxane‐polyethylene glycol (SSQ‐PEG) was synthesized and used as a template to make the distribution of pores more even in the low‐k films. The crosslinking density of films could be adjusted by the sol‐gel of tetramethoxysilane/dimethoxydimethylsilane with various proportions. The porosity of films could also be adjusted with different proportions of pendant PEG chains introduced. A dielectric constant as low as 2.1 had been achieved for nanoporous polyorganosilicate films with good tenacity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1238–1243, 2007