【作者】 吕杰；

【导师】 宋武林；

【作者基本信息】 华中科技大学 ， 材料学， 2009， 硕士

【摘要】 本文以电爆炸丝法制备的含有高活性铝含量的纳米铝粉作为研究对象,采用气体容量法测量了纳米铝粉中的活性铝含量,分析铝粉反应不完全可能存在的原因。并在传统的滴定法测量纳米铝粉活性含量的基础上,对锰滴法及铈滴法等实验方法进行改进,探讨体系中酸度、时间等各因素的影响,从而分别以最佳的反应体系进行反应测量活性铝含量。最后分别采用氧化模型理论计算和Rietveld结构精修的方法计算了纳米铝粉中活性铝的含量。实验中采用TEM、HRTEM、XRD等手段对纳米铝粉进行了物性表征,电爆法制备纳米铝粉为球形颗粒,粒径大约在20-130nm范围内呈正态分布,具有明显的核壳结构,表面Al2O3壳层厚度大约在3nm左右。气体容量法测得纳米铝粉中活性铝含量只有75.75%,由TEM及SEAD分析得知纳米铝粉始终反应不完全,这可能与溶液中离子的溶剂化作用有关,离子间相互作用形成离子氛从而限制了离子的行动,使得溶液中OH-不能充分与内部金属铝接触而反应不完全。锰滴法中,采用无水乙醇作为溶剂,有效抑制了纳米铝粉与水的反应。同时采用硝酸铁作为氧化剂,在纳米铝粉约50mg左右时,在搅拌反应2h后加入0.1mol/L的硝酸28mL继续反应约24h,测得纳米铝粉中单质铝含量达到最高,约94.45%。并通过实验讨论了体系中少量水的存在是必要的,还对酸度、时间等各因素的影响进行了深入的分析。铈滴法中硫酸高铈溶液的酸度大小对活性铝含量的测量有影响,当酸的浓度为0.15mol/L时,测得的活性铝含量最高为87.70%。纳米铝粉在低温下慢氧化到一定程度会达到饱和状态,氧化层达到一定厚度停止生长。对此种核壳结构模型,由HRTEM表征结果设表面Al2O3壳层厚度为3nm,采用数学积分的方法计算内核金属铝的质量分数,得到金属铝的含量为78.79%。由于部分粒径较小的颗粒有可能已全部为氧化铝,因此此方法是一种近似计算。对纳米铝粉在X射线衍射仪上进行步进扫描收集数据,采用Fullprof程序对样品参数进行Rietveld结构精修,得到电爆炸法的纳米铝粉中含有杂质镁,金属单质铝的含量为90.44%。最后,对几种测量活性铝含量方法的优劣进行了综合评价和分析,选择以Rietveld精修的方法来作为较为准确的测定纳米铝粉中活性铝含量的测量方法。更多还原

【Abstract】 The aluminum nanoparticles prepared by electrical explosion of wire (EEW) were studied. In the volumetric method, the phenomenon of the incomplete reaction between aluminum and NaOH solution was probably relevant to the ion solvation. Besides, on the basis of traditional titrimetric methods of determining the metallic aluminum content in the aluminum nanoparticles, in this article Permanganatometric and Cerimetric methods were improved, the effect factors of acid degree, reaction time and so on in the system were also discussed, then the content of metal aluminum was determined by the optimal system. Finally the metal oxidation model and Rietveld refinement were used to calculate the metallic aluminum content.In this work, the characterizations of aluminum was tested by TEM、HRTEM、XRD and the results indicated that the aluminum powders by EEW with the sphere shape showed gaussian distribution in a diameter range from 20nm to 130nm. Besides, the aluminum nanoparticles showed a core-shell structure and the Al2O3 cell thickness was 3nm or so.With the volumetric method the metal aluminum content was only about 75.75%, and the reaction between aluminum nanopowders and NaOH solution was incomplete due to the ion salvation.In the Permanganatometric method, ethanol was used as nonaqueous solvent to prevent the reaction between aluminum nanoparticles and water at room temperature. Besides, Fe(NO3)3 as oxidizing agent. The contrast results illustrated that the content can reach the highest when the aluminum powders were 50mg or so, and the concentration and volume of HNO3 were 0.1mol/L and 28mL, the reaction time was 24h. More over, the mechanism of effect factors were discussed.The concentration of sulphuric acid in the ceric sulfate solution had an effect on the metal content in the cerimetric method and it could reach 87.70% when the H2SO4 concentration was 0.15mol/L.The oxidation of aluminum nanoparticles at low temperature could be saturated to a certain extent and the oxide layer stopped growing. For this core-shell structure, the thickness of the oxide layer was assumed 3nm from the HRTEM result. Then the metal content calculated with the method of Mathematics with Calculus was 78.79%. However, this method was also an estimation for some of the nanoparticles may be oxidized completely.The Rietveld refinement was used to calculate the content of metal aluminum phase. The powder diffraction data was collected using X-Ray Diffractomer with step scanning. Then the fullprof program was used to refine the structural parameters and the result showed that the metallic content was 90.44%, while the impurity Mg was detectived with a content of 0.21% in the aluminum nanopowders by EEW.Finally, there was a comprehensive comparison and analysis among these methods to determined the metallic content in the aluminum nanopowders, and the Rietveld refinement was set as a standard to determined more precise.更多还原