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21.
This paper deals with the development of new synthesis techniques for functional materials such as Yttria Stabilized Zirconia (YSZ) used in the field of thermal barriers coatings. Currently, Thermal Barrier Coatings (TBCs) are manufactured by dry route technologies (EB-PVD or plasma spray) but such methods are directional and often require costly investments and complicated operations. We have carried out significant work aimed at developing sol-gel routes, which are nondirectional methods, to prepare, by suitable chemical modifications, nanocrystalline materials with a controlled morphology. The main advantage of this method is to decrease the crystallization temperature, much lower than the conventional processes, allowing the synthesis of reactive powders with nanometric particles size. In this paper, the formulation of an alkoxide sol has been optimized in order to obtain homogeneous YSZ films. Nature and quantity of binders have been studied. Superalloys have been then immersed in the sol and withdrawn at several controlled rates before being annealed at different temperatures. The films microstructures have been investigated using scanning electron microscopy. It appears that the combination of a slower withdrawal speed (17 cm/min) with a 3 wt.% content of DBP allows to obtain the most homogeneous and the thicker coatings. Moreover, SEM-FEG observations have shown that the deposit is present all over the rough surface of the substrate and is composed of two morphologies: a YSZ thin covering film and a thicker discontinuous layer duplicating the substrate topography. 相似文献
22.
溶胶-凝胶法制备疏水型SiO-2气凝胶 总被引:2,自引:0,他引:2
以正硅酸乙酯 (TEOS)为硅源 ,用三甲基氯硅烷 (TMCS)为疏水试剂 ,通过溶胶 凝胶法在室温下制备出疏水型SiO2 气凝胶。用傅立叶变温红外 (FT IR)、扫描电镜 (SEM)、透射电镜 (TEM)和吸水性能对疏水型SiO2气凝胶的结构和性能进行了研究 相似文献
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TiO2 andCeO2 aresemiconductormaterials .TiO2hasthepropertiesofphoto catalysis[1] whileCeO2 hastheabilityofoxygenstorageandcanpromotethedispersionofprecionsmetalsonthesupporter[2 ] .CeO2 TiO2 com plexcompoundwasusedascatalystandspecialfunction almaterial[3~ 5] .ThetraditionalsynthesisofCeO2 TiO2complexcompoundisbyceramicmethodthatusesoxidesasrawmaterialsanditiscalcinedabove 130 0℃[6~ 8] .However ,thestructureandmicrostructureofthecomplexcompoundarenotsuitableforcatalystandfunctionalm… 相似文献
25.
Sol-gel methods offer many advantages over conventional slip-casting, including the ability to produce ceramic membranes. They are purer, more homogeneous, more reactive and contain a wider variety of compositions. We produced ormosil sol using sol-gel process under different molecular weight of polymer species [polyethylene glycol (PEG) ] in total system [Tetraethyl ortho silicate(TEOS)-polyethylene glycol (PEG)]. The properties of as-prepared ormosil sol such as,viscosity, gelation time were characterized. Also, the ceramic membrane was prepared by dip-coating with synthetic sol and its micro-structure was observed by scanning electron microscopy. The permeability and rejection efficiency of membrane for oil/water emulsion were evaluated as cross-flow apparatus. The ormosil sol coated Membrane is easily formed by steric effect of polymer and it improves flux efficiency because infiltration into porous support decreased. Its flux efficiency is elevated about 200(1/m2·h) compared with colloidal sol coated membrane at point of five minutes from starting test. 相似文献
26.
溶胶-凝胶生物玻璃多孔材料显微结构和生物活性的扫描电镜及红外光谱分析 总被引:13,自引:0,他引:13
本文利用溶胶.凝胶法制备了CaO-P2O5-SiO,系统生物活性玻璃,并以其为原料制备了用于骨修复及骨组织工程支架的块状生物活性材料。利用体外实验方法(invitro)结合x射线衍射(XRD)、扫描电子显微镜(SEM)和傅立叶变换红外光谱分析(FTIR)技术对不同烧结工艺制备的材料结构、晶相和生物活性的影响进行了分析研究。研究表明,经800℃和1100℃烧结5min的两种材料均有硅磷酸钙Ca5(PO4)2SjO4微晶相析出。烧结温度越高,析出微晶相的体积比例越大,材料的生物活性则越低。在模拟生理溶液中碳酸羟基磷灰石(HCA)只在烧结体中的玻璃颗粒表面形成,而在其硅磷酸钙Ca5(PO4)2SiO4微晶相表面未发现HCA形成。 相似文献
27.
CoFe2O4超细微粒催化剂的制备,性能与表征 总被引:20,自引:1,他引:19
用溶胶-凝胶法制备了钴铁复合氧化物超细微粒催化剂,用TG-DTA、TEM、XRD等手段考察了加入聚乙二醇200对其粉体特性及催化性能的影响,结果表明,添加金属量3%的聚乙二醇200,可显著改善粒子团聚,得到平均粒径为30nm、分散均匀的超细粒子,在350℃下焙烧2h,可得到前驱体分解完全,非完整晶态的CoFe2O4,其对对甲酚催化氧化制取对羟基苯甲醛的性能较好。 相似文献
28.
以乙醇为溶剂,正硅酸乙酯(TEOS,tetraethoxysilane)在氢氧化铵催化下水解缩聚为纳米尺度的无定型SiO2溶胶颗粒,二甲基二乙氧基硅烷(DDS,dimethyldiethoxysilane)在盐酸催化下水解缩聚为线状聚二甲基硅氧链.用混合溶胶在玻璃基片上旋转镀膜,然后于80℃空气气氛下热处理.实验证明通过DDS将疏水的双甲基链引入镀膜胶体,使膜兼具疏水性和减反射性能.利用激光散射粒度分析仪和电子显微镜研究了溶胶颗粒的粒度变化和聚集情况等溶胶微结构,用物理吸附仪研究了膜的孔结构,考察了热处理前后膜的疏水性和透射谱,得到了溶胶微结构与膜性能之间的关联. 相似文献
29.
Polyurethane acrylate anionomer (PUAA)/silica composite gels were prepared by the sol‐gel reaction of tetraethoxysilane (TEOS) and methacryloxypropyl trimethoxysilane (MPTS) incorporated to PUAA gels by using a swelling method. The formation and structure of composites were confirmed by FTIR, X‐ray diffraction, and SEM. As a result, we found that silica components in composites are located within the ionic domains of their gels and interacted with PUAA via hydrogen bonding. This drastically enhanced the mechanical properties of the composites. Mechanical properties are also improved by MPTS, because MPTS improves the dispersibility and adhesion of silica components in PUAA/silica composite gels. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2327–2334, 2002 相似文献
30.