【作者】 李强；

【导师】 王麟生；

【作者基本信息】 华东师范大学 ， 无机化学， 2007， 硕士

【摘要】 金属纳米氧化物是一类具有广泛用途的纳米材料,由于其本身具有量子尺寸效应,小尺寸效应,表面效应,宏观量子隧道效应等,使其具有明显优于本体材料的性能,本文介绍了纳米氧化镁、氧化镍、氧化铈的国内外研究现状;分析了溶胶凝胶法的分类、原理以及优缺点;分别以主族金属Mg,过渡金属Ni,稀土金属Ce为代表,使用溶胶凝胶法制备了上述金属元素的纳米氧化物,对其结构和组成进行了表征,对反应条件进行了改进和优化,并对其某些方面的应用进行了研究。以苹果酸和硝酸镁为原料,采用溶胶-凝胶法(sol-gel)制备了氧化镁纳米晶。根据制备条件的不同,粒径可在7-20nm之间。采用傅立叶红外光谱(FT-IR)、热分析(TG-DTA)、X射线衍射(XRD)、透射电子显微镜(TEM)对凝胶的组成和热分解过程,凝胶和样品的物相组成以及样品的形貌、粒径大小、分布情况进行了分析;考察了原料配比、煅烧温度和时间、溶液初始pH值、乙醇用量对样品形貌和粒径的影响。结果表明,硝酸镁与苹果酸的摩尔比为1:1.5,煅烧温度在500～700℃,煅烧时间为3h,溶液初始pH值在3-7,V乙酣:V水为1:4时为最佳反应条件;纳米氧化镁的生成可能与NH4NO3的存在有较大关系,NH4NO。的存在有利于粒子间的细化,减小了粒子间的团聚;纳米氧化镁在紫外区有较大的吸光度,紫外可见光谱(UV-Vis)表明,纳米氧化镁的紫外屏蔽性能优于普通的氧化镁粉体,铕离子的掺入能明显提高纳米氧化镁的紫外屏蔽性,并对其原因进行了分析。以碱式碳酸镍和苹果酸为原料,蒸馏水为溶剂,通过溶胶凝胶法制备了纳米氧化镍;并采用热重差热分析(TG-DTA),X射线粉末衍射(XRD),傅立叶红外光谱(FT-IR)以及透射电子显微镜(TEM)对其反应过程和样品的粒径、形貌进行了分析。结果表明,由碱式碳酸镍和苹果酸反应得到的前驱体主要是由苹果酸镍和残留苹果酸组成;前驱体在400℃煅烧1h可完全转化为纳米氧化镍。所得纳米氧化镍属立方结构,由谢乐公式可知其平均粒径为14nm。而且分布均匀,无明显团聚现象,随着温度的升高所得样品的粒径增大。随苹果酸量的增加,纳米氧化镍的粒径呈先增大后减小的趋势,并且粒子问团聚程度增加;溶剂体积增加时,粒径逐渐减小;随煅烧时间的延长粒径逐渐增大,但无明显团聚产生。与其他方法相比,该法简单,原料廉价,所以在大规模的工业化生产中很有发展潜力。此外,对反应中金属镍形成的机理进行了探讨。以苹果酸做为还原剂,硝酸铈为氧化剂,采用自蔓延燃烧法(auto-combustion)成功制备了氧化铈纳米晶。前驱体通过在200℃左右燃烧得到疏松的纳米氧化铈粉末,利用IR、TG-DTA、XRD、TEM对前驱体和样品进行了分析,并对苹果酸与硝酸铈的配比对反应的影响进行了研究,当两者的摩尔比从3降到1后,燃烧速率明显增加,粒径从8.5nnm增加到24.7nm。并用IR和TG-DTA对自燃烧的机理进行了分析。随溶液初始pH的增加粒径减小,粒子的分散性增强;此外,纳米氧化铈的紫外屏蔽性明显优于普通氧化铈,原料配比不同所得样品在整个紫外可见区的吸光度不同。研究了所得样品对高氯酸铵(AP)热分解的影响,并与本体的氧化铈进行了比较。结果表明,纳米氧化铈对AP的热分解具有明显的催化活性,添加纳米氧化铈后AP的分解终止温度降低了46℃,高温分解温度降低了48℃,并且提高了AP的分解速率。催化性能明显优于本体氧化铈,并对氧化铈的催化机理进行了分析。更多还原

【Abstract】 Nano-metal oxides are one kind of very useful nanomaterials. Because of the quantum size effect, small size effect, surface effect and macro-quantum tunnel effect, it’s property is obviously superior to the counterpart bulk materials. In this dissertation, the research situation of the nano-magnesia, nano-nickel oxide and nano-ceria are introduced, and the classification, theory, advantage and drawback of the sol-gel method are analyzed. Using Mg, Ni, Ce as the delegate of mainly group element, transition metal element and rare earth element respectively, the corresponding nano-metal oxides were prepared by sol-gel method. The structure and composition of the as-prepared nano-oxides were characterized. And the reactive condition was improved and optimized. Their some application was analyzed.The magnesium oxide nanocrystallites were prepared by sol-gel method, using malic acid and magnesium nitrate as raw materials. On different prepared conditions, the particle size can change from 7nm to 20nm. FI-IR,TG-DTA,XRD and TEM were used to investigate the composition, decomposition processing of the gel and the phase of the gel and sample, the morphology, particle size and particulate distribution of the sample. The influence of ratio of the raw materials, calcined temperature and time ,the initial pH value and the amount of ethanol on the particle size and morphology of the sample was analyzed. The results show that the mole ratio of Mg²⁺ to malic acid being 1:1.5 ,calcined temperature at 500～700°C,calcined time for 3h,the initial pH value being 3-7 and the volume ratio of ethanol to water being 1:4 were best condition. The production of the nano-magnesia may be related with the exist of ammonium nitrate, and it was used to decrease the particle size and agglomeration. UV-Vis Spectra show that UV-shielding capacity of the nanosized magnesium oxide was superior to normal magnesium oxide. Doped Eu²⁺ can obviously increase the UV-shielding capacity of the nanosized magnesium oxide, and the reason was analyzed.NiO nanoparticles have been successfully prepared by calcining malate gel, using basic nickel carbonate （BNC） and malic acid as the raw materials and H₂O as the solvent. The reaction was studied by TG-DTA, XRD and FT-IR. The particle size and morphology of NiO nanoparticles was characterized by TEM. The results show that nickel malate could be formed by the reaction of BNC and malic acid. the gel was composed of nickel malate and residual malic acid. the precursor can translate into NiO nanoparticles completely at 400°C under the air, and the as-prepared sample has cubic crystal structure with about 14 nm of average diameter by the Scherrer formula. The NiO calcined at 400°C for 1 h was of narrow particle size distribution, weak agglomeration and small particle size. The particle size of NiO increased with the increasing of temperature. With the increase of malic acid, the degree of the agglomeration was increased. the particle size decreased with the increase of the solvent. With the increase of the calcined time, the particle size increased gradually and no obvious agglomeration was found. Compared with other methods, the developed method is simple and the raw materials was inexpensive, so that it has potential for further scale-up application in industry. Furthermore, the reason for the metallic nickel formation in the course of the preparation was explained.The nanocrystalline ceria powders have been synthesized by the combustion technique, using malic acid as the reductant （fuel） and cerium nitrate as the oxidant. The auto-combustion （at about 220°C） of the precursor containing cerium nitrate and malic acid resulted in loose nanoceria powders. The precursor and as-burnt powders were investigated with infrared （IR） spectra, thermal analysis, X-ray diffraction and transmission electron microscopy. The experiments showed that the particle size is uniform. The influence of the molar ratio of malic acid to cerium nitrate （M/C value） was investigated. As M/C values are decreased from 3 to 1, the combustion rate is increased significantly, and the crystallite size is increased from 8.5 nm to 24.7 nm. The combustion reaction mechanism was analyzed with IR spectra and thermal analysis techniques. The UV-shielding capacity of the as-burnt ceria is superior to bulk ceria. The absorption of the as-burnt ceria in UV field is related with the molar ratio of the raw materials. The influence of the as-burnt ceria on the thermal decomposition of ammonium perchlorate （AP） were investigated and compared with bulk ceria. The results show that the as-burnt ceria has high catalytic activity on the thermal decompostion of AP. The end temperature of decomposition of AP reduce 46 °C, and the higher temperature decomposition reduce 48°C. The decomposing rate of AP is enhanced. The catalytic behavior of the as-burnt ceria is superior to bulk ceria. The catalytic mechanism of ceria was analyzed.更多还原