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Sol-Gel-SCFD法制备纳米莫来石 总被引:9,自引:0,他引:9
以AIP(Aluminum-isopropoxde)和 TEOS(Tetraethyl Orthosilicate)为主要原料,采用Sol-Gel-SCFD(超临界流体干燥)技术制备了n(Al2O3):n(SiO2)=3:2的Al2O3-SiO2二元纳米气凝胶,通过中温煅烧,获得了纳米级莫来石.用热重-差示扫描热量计(TG-DSC)、透射电子显微镜(TEM)、X射线衍射仪(XRD)和物理吸附分析仪(Autosorb)等手段对二元纳米气凝胶和纳米莫来石进行了分析和研究.TG-DSC研究表明,在煅烧过程中,气凝胶的大部分失重(15.98%)在700℃左右已完成,DSC曲线上在445和 1015℃存在的两个放热峰是由于二元凝胶中的Si-O-Al-O结构重整和莫来石化所致,而在805℃处小的吸热峰是由体系中结构水分解所致;借助于 TG-DSC、XRD和 TEM分析手段,可以确定在纳米Al2O3-SiO2二元材料内,莫来石的开始形成温度为1015℃左右.XRD分析表明,完全转变成莫来石温度在1100~1200℃之间,1200℃可得晶粒发育良好的纳米级莫来石;TEM和物理吸附分析仪测试结果表明,1100和1200℃所得纳米莫来石的微粒大小分别为30和50nm左右, 比表面积分别为138.91和95.81m2/g. 相似文献
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纳米多孔二氧化硅薄膜的制备及性能 总被引:5,自引:0,他引:5
以N(C_8H_(15))_4~+OH~-为催化剂,用正硅酸乙脂(TEOS)溶胶-凝胶工艺制备出纳米多孔二氧化硅薄膜。体系的H_2O/TEOS>25,强碱催化使二氧化硅的溶解度增大并使二氧化硅胶粒带负电荷,抑制了二氧化硅的聚合。丙三醇与TEOS的水解中间体Si(OC_2H_5)_4-x(OH)_x及二氧化硅胶粒Si_xO_y(OH)_z~(+n)表面Si-OH形成氢键,抑制了二氧化硅的聚沉。聚乙烯醇(PVA)使粒状二氧化硅溶胶具有网状结构,易于成膜。薄膜由致密结构转化为均匀纳米多孔结构是构成薄膜的二氧化硅胶粒在热处理时聚集和塑性形变的结果。多孔二氧化硅薄膜的折射率为1.27~1.42,介电常数为1.578~2.016,热导率为0.2W/(m·K)。 相似文献
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以正硅酸乙酯(TEOS)为先驱体,采用溶胶-凝胶法,结合旋转涂胶和超临界干燥等工艺,在硅片上制备了纳米多孔SiO2薄膜。XRD和AFM表明该SiO2薄膜为无定形态,具有多孔网络结构,表面均匀平整,其SiO2基本粒子和孔隙的直径为30~40nm。利用椭偏光谱仪测量了SiO2薄膜在波长245~1650nm的椭偏光谱,采用Si/cauchy/rough结构模型对该光谱进行了拟合,获得了SiO2薄膜的厚度和光学常数。SiO2薄膜的厚度为500~1100nm;折射率为1.13~1.21;孔隙率为56%~70%;介电常数为1.9~2.3。 相似文献
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聚乙二醇对纳米多孔二氧化硅薄膜性能的影响 总被引:9,自引:0,他引:9
以聚乙二醇(PEG)为添加剂,正硅酸乙酯(TEOS)为先驱体,采用溶胶-凝胶法、结合 旋转涂胶和超临界干燥等工艺在硅片上制备了纳米多孔SiO2薄膜.利用FTIR、TG-DTA、 AFM和椭偏仪研究了该SiO2薄膜的性能.与未加.PEG的SiO2薄膜相比,加入PEG得到 的SiO2薄膜表面粗糙度增大,但孔隙率较高,介电常数可降至2.0以下.PEG参与并修饰了 TEOS的溶胶-凝胶过程.加入PEG制备的SiO2薄膜因含有Si-OH基团而呈亲水性,该薄 膜经三甲基氯硅烷(TMCS)修饰后为疏水性. 相似文献
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多孔TiO2光催化纳米薄膜的制备和微观结构研究 总被引:14,自引:0,他引:14
锐钛矿型多孔TiO2纳米薄膜可以从含聚乙二醇(PEG)的钛酸盐溶胶前驱体中通过溶胶-凝胶法制备.涂层的形貌,如孔的大小和孔的分布可以通过聚乙二醇的加入量和分子量来控制.当聚乙二醇的加入量和分子量越大,聚乙二醇热分解后在薄膜中产生的气孔就越多和孔径越大.随着TiO2薄膜中气孔孔径和数量的增加,光的散射增强,薄膜的透光率减小.通过扫描电镜(SEM)和重量法测定了薄膜的厚度,每镀一次薄膜的厚度增加约为0.08μm.通过X射线光电子能谱(XPS)和红外光谱(IR)确定了多孔TiO2纳米薄膜中元素的化学组成和表面羟基含量.实验结果表明:薄膜中除含有Ti、O元素外,还有一定量来自有机前驱物中未完全燃烧的碳和少量从玻璃表面扩散到薄膜中的Na和Ca元素;同时发现薄膜表面的羟基含量随聚乙二醇的加入量的增加而增加 相似文献
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采用溶胶-凝胶法、分子模板法及旋转涂覆法在硅衬底上制备掺杂TiO2的SiO2薄膜,并采用差热分析(DSC-TGA)、红外吸收光谱(FTIR)、X射线衍射、小角衍射(SAXS)、原子力显微镜(AFM)、台阶仪(Atomic-Profiler)以及纸擦拭法(paper-wiping method)和胶带剥离法(adhesive tpe-stripping method)对薄膜的性能进行了分析与表征,结果表明,薄膜的最佳热处理温度为400℃,所制备的掺杂TiO2的SiO2薄膜为多孔结构的无定形态,具有较好的机械性能,平均孔径随着膜层的增加而减小,一层膜和两层膜的平均孔径分别为87.4nm和62.8nm,厚度分别为538.7nm和1032.3nm。 相似文献
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碱催化多孔二氧化硅薄膜的制备和性能表征 总被引:8,自引:0,他引:8
以水为介质,NH3·H2O为催化剂,丙三醇(C3H5(OH)3和聚乙烯醇(PVA)为添加剂,正硅酸乙脂(TEOS)溶胶 凝胶工艺可制备纳米多孔二氧化硅薄膜。体系的H2O/TEOS>15,TEOS的水解 聚合过程可通过添加剂效应,pH效应等控制。碱催化会使二氧化硅的溶解度增大,也能使二氧化硅胶粒带负电荷,抑制了二氧化硅胶粒之间的聚合长大,而丙三醇与TEOS的水解中间Si(OR)4-x(OH)x结合,抑制其与二氧化硅胶粒的聚合。聚乙烯醇(PVA)能使二氧化硅溶胶具有网状结构,使二氧化硅溶胶易于成膜。该工艺制备的多孔二氧化硅薄膜具有纳米多孔结构。其Vicker硬度在600~800N/mm2,热导率<0.2W·m-1K-1。 相似文献
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Weiwei Yan Liyi Shi Shuai Yuan Yin Zhao Jianhui Fang Jian Zhao 《Materials Letters》2010,64(10):1208-1097
Nanoporous silica colloids were prepared by a convenient single-step sol-gel process. In this approach, acidic aluminum nitrate (Al(NO3)3) solution was added to the ethanol solution of tetraethoxy orthosilicate (TEOS). In the preliminary stage, alumina/silica core-shell particles were formed. Then the Al2O3 cores were dissolved subsequently with the decrease of pH value, and the nanoporous silica was formed. The porous silica particles were characterized by transmission electron microscopy (TEM). The formation mechanism of the porous silica was discussed. 相似文献
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A water soluble porogen, e.g., poly(amido amine) dendrimer, has been used as a structure-directing agent to introduce porosity of nanometer scale in silica-based nanocomposite materials. Hydrothermal synthesis was carried out at different elevated temperatures (343-413 K) in a closed teflon-lined stainless steel autoclave under autogenerated pressure. The synthesis time varied from 2 to 6 days, depending upon pH, synthesis temperature, concentration of porogen, etc. X-ray diffraction, transmission and scanning electron microscopic analyses, as well as infrared absorption spectroscopic measurements, were carried out to characterize these materials. Mostly disordered mesostructures were observed. The porous silica particles with sphere-like morphology varied from 30 to 200 nm in size were prepared depending upon the conditions of preparation. The structure and nanoporosity were preserved after the removal of structure-directing porogen through calcination at 823 K. The pore size was in the range of the dendrimer molecule as a template, indicating the structure-directing role of the terminal amino groups in the dendrimer molecule for the synthesis of nanoporous silica, since the nanoporous silica could be prepared by the hydrogen bonding or electrostatic interaction of dendrimer amino groups and tetraethyl orthosilicate. 相似文献
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AbstractNanoporous silica cryogels with a high specific surface area of 1095 m2 g?1 were fabricated using tert-butyl alcohol as a reaction solvent, via a cost-effective sol–gel process followed by vacuum freeze drying. The total time of cryogel production was reduced markedly to one day. The molar ratio of solvent/precursor, which was varied from 5 to 13, significantly affected the porous structure and thermal insulating properties of the cryogels. The silica cryogels with low densities in the range of 0.08–0.18 g cm?3 and thermal conductivities as low as 6.7 mW (m·K)?1 at 100 Pa and 28.3 mW (m·K)?1 at 105 Pa were obtained using this new technique. 相似文献
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Nanoporous silica cryogels with a high specific surface area of 1095 m2 g−1 were fabricated using tert-butyl alcohol as a reaction solvent, via a cost-effective sol–gel process followed by vacuum freeze drying. The total time of cryogel production was reduced markedly to one day. The molar ratio of solvent/precursor, which was varied from 5 to 13, significantly affected the porous structure and thermal insulating properties of the cryogels. The silica cryogels with low densities in the range of 0.08–0.18 g cm−3 and thermal conductivities as low as 6.7 mW (m·K)−1 at 100 Pa and 28.3 mW (m·K)−1 at 105 Pa were obtained using this new technique. 相似文献
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Abbruzzetti S Viappiani C Bruno S Bettati S Bonaccio M Mozzarelli A 《Journal of nanoscience and nanotechnology》2001,1(4):407-415
Myoglobin and hemoglobin were encapsulated in wet, nanoporous silica gels. A rigorous evaluation of the effect of the encapsulation on protein dynamics and function was carried out by measuring the kinetics of carbon monoxide rebinding after nanosecond laser flash-photolysis with transient absorption detection, and the oxygen affinity with absorption microspectrophotometry. The time course of carbon monoxide binding to myoglobin evidenced a strongly enhanced geminate recombination and a faster bimolecular rebinding with respect to solution, whereas T and R quaternary states of hemoglobin exhibited a geminate phase and a bimolecular binding rate very similar to those observed in solution. Oxygen affinity of T-state hemoglobin was found to be close to that observed for the binding of the first oxygen to T-state hemoglobin in solution. Results indicate that some conformational transitions are kinetically restricted, allowing to isolate distinct tertiary and quaternary states. This opens the way to their detailed functional characterization and application to biodevices. 相似文献
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Yu HC Kumar SV Cho SY Kudo K Takayama T Oh JM Jung H Kim JG Chung CM 《Journal of nanoscience and nanotechnology》2011,11(7):6141-6147
Fully aliphatic polyimides (APIs) were prepared from rel-(1'R,3S5'S)-spiro[furan-3(2H),6'-[3]oxabicyclo[3.2.1]octane]-2,2',4',5(4H)-tetrone (DAn) as unsymmetrical spiro dianhydride, and either cis-trans-1,4-diaminocyclohexane (mix-DACH) or trans-1,4-diaminocyclohexane (trans-DACH) as diamine. Structure of all prepared monomers and polymers was confirmed via 1H-NMR and FT-IR. The solubility, optical transparency, and thermal properties of the full APIs were investigated. The solubility and decomposition temperature of the full APIs were found to be correlated with their intermolecular regularity confirmed via wide-angle X-ray diffraction (WAXD). Triblock copolyimides were synthesized through the incorporation of a thermally labile polymer, poly(propylene glycol) (PPG), into the full APIs, and their thermal properties were studied via thermogravimetric analysis (TGA). Nanoporous thin films of the full APIs were prepared via thermolysis of the labile block in the copolyimide films. Phase separation and nanopore formation in the copolymer films were confirmed via atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Nanoporous pores were successfully prepared inside the films. 相似文献