【作者】 徐琴琴；

【导师】 银建中；

【作者基本信息】 大连理工大学 ， 安全技术及工程， 2007， 硕士

【摘要】 纳米复合材料是当前材料领域研究的热点，在介孔材料的纳米孔道限制空间内制备金属纳米粒子为纳米复合材料的制备提供了一种新的有效的途径。本文以纳米复合材料制备为研究背景，基于超临界流体的特殊物化性质，选择超临界流体沉积技术为手段，研究在SBA-15介孔分子筛孔道中担载纳米金属粒子的可行性、操作条件、沉积机理以及超临界吸附模型。主要工作和结果如下：（1）以有机金属化合物Cu（acac）₂为前驱物，用超临界流体沉积法（SFD），在压力25MPa左右，温度50℃条件下将Cu（acac）₂沉积到介孔分子筛SBA-15的孔道中。反应完成后，用氢气对前驱物进行还原，得到Cu／SBA-15复合材料。TEM表征发现，所得到的复合材料中Cu以纳米颗粒形态存在，高度分散在SBA-15的孔道内，平均尺寸4.7nm，尺寸分布3.3-6.0nm。（2）为了降低SFD法制备纳米复合材料的成本，开发廉价前驱物和改进沉积工艺（缩短反应时间）是有效途径。因此，本文设想以廉价的无机金属化合物替代价格昂贵的有机金属化合物，通过在超临界二氧化碳中添加合适的共溶剂克服无机盐在超临界二氧化碳中不能溶解的难题，从而使无机盐SFD法制备纳米复合材料成为可能。为此，选择Cu（NO₃）₂为前驱物，用超临界二氧化碳做溶剂，乙醇为共溶剂，在压力20-26MPa，温度50℃条件下将Cu（NO₃）₂沉积到SBA-15介孔分子筛的孔道中。反应完成后，用氢气对前驱物进行还原，得到Cu／SBA-15纳米线和纳米颗粒复合材料。用TEM、XRD和ICP对所得Cu／SBA-15复合材料进行表征。结果表明：●在SBA-15孔道内部填充了Cu纳米线和高度分散的Cu纳米颗粒；●Cu纳米线平均直径为5.5-6nm，长度为几纳米到几微米；●纳米线沿孔道生长，能够随着孔道发生弯曲；●Cu纳米粒子的平均尺寸为4-5nm，尺寸分布窄；●所得复合材料中Cu含量可达7.97wt％。同Cu（acac）₂为前驱物制备的Cu／SBA-15相比，纳米粒子的尺寸、尺寸分布、分散度相差无几，但沉积时间大大缩短，前驱物价格显著降低。（3）纳米复合材料的金属负载量对纳米相形貌，纳米颗粒尺寸和尺寸分布等有很大的影响。为了考察操作条件对所得纳米复合材料金属负载量的影响，本文对前驱物在超临界二氧化碳环境中，吸附到SBA-15上的热力学平衡过程用Langmuir模型、Freundlich模型进行了关联，发现这两个经典吸附模型可以较好的关联超临界流体沉积法中的吸附过程。（4）实验结果表明，超临界流体沉积法是制备金属纳米复合材料的有效方法。选择合适的共溶剂可以用超临界二氧化碳溶解无机金属化合物，并可以通过控制反应条件，控制所得纳米复合材料中纳米相的形貌。时间长短和前驱物浓度是影响纳米相形貌的重要因素，当前驱物浓度以及前驱物与载体质量比一定时，纳米相形貌特征可以根据时间长短分为四个阶段：时间短形成小颗粒，增长时间形成纳米线，之后再增长时间纳米线断裂，所得复合材料中纳米短线和纳米颗粒共存，时间足够长纳米相结构全部为大颗粒。更多还原

【Abstract】 Nano-composites are the focus of many researches in material fields. Limiting of metallic nanoparticles into confined space of mesoporous material has been proved to be a novel and effective approach for the preparation of nanocomposites.The feasibility, experiment parameters, mechanism and the model of supercritical adsorption were investigated about preparing supported metal nanoparticles and nanowires into the channels of mesoporous material SBA-15 via Supercritical Fluid Deposition （SFD） method. The main experiments and results are as follows:（1） Organic metallic compound Cu（acac）₂ was deposited into the channels of mesporous SBA-15 using SFD method at the pressure of about 25MPa,temperature of 50℃, followed by calcinations and hydrogen reduction. Highly dispersed Cu nanoparticles with an average particle size of 4.7nm are found to be supported onto the channels of SBA-15 by TEM analysis. And the particles have a size distribution from3.3nm to 6.0nm.（2） To reduce the cost of preparation of nano-composites,developing a cheap precursor and making a short deposition time are supposed to be an effective way. Inorganic Cu（NO₃）₂ was deposited into the channels of mesporous SBA-15 using SFD method with ethanol as co-solvent at the pressure of 20-26MPa,temperature of 50℃.Supported Cu nanowires and nanoparticles were obtained after calcinations and hydrogen reduction of Cu（NO₃）₂/SBA-15. The Cu/SBA-15 composites were characterized by means of TEM, XRD and ICP. The Cu content of the composites is as high as 7.97%. Cu nanowires with the mean diameter 5.5-6nm were found filling the channels of SBA-15 and their lengths varied from several nanometers to several micrometers. What’s more, the nanowires grew and curved along the channels. Highly dispersed Cu nanoparticles with the mean particle size of 4-5nm.The particles size ,size distribution and the metal content of the nano-composites prepared using Cu（NO₃）₂ have no distinct differences with those prepared using Cu（acac）₂, but as far as the deposition time is concerned, the former（Cu（NO₃）₂） is much shorter than the latter（Cu（acac）₂）.（3） To discuss the metal loading of the nano-composites, adsorption of the precursor to the substrate from SCCO₂ was studied and Langmuir model and Freundlich model were used to fit the adsorption equilibrium data. The two traditional adsorption models can fit the adsorption process during SFD method well.（4） The morphology of Cu in the composites was controllable by changing the experiment conditions. Mechanism model of the nanowires or nanoparticles growing during SFD process are put forward based on the experiment result. The precursor concentration and deposition time influence the morphology of the nano-phase a lot. When the precursor concentration and the ratio of precursor to substrate are fixed, the formation of the nano-phase can be divided into four stages based on the deposition time. The first stage small nano-particles are formed, during the second stage nanowires appear and small nanoparticles vanish, nanowires break during the third stage and big nanoparticles as well as short nanowires appear. Finally when the deposition time is very long, all nanowires disappear and big nanoparticles are found instead.更多还原