纳米α-氧化铝的制备及其改性

【作者】 尹良果；

【导师】 黄可龙；

【作者基本信息】 中南大学 ， 应用化学， 2007， 硕士

【摘要】 本文介绍了纳米氧化铝的性质、用途、国内外研究现状及制备方法。讨论了沉淀法制备粉体的理论基础，着重对前躯体制备过程中的防团聚机理进行了深入的理论分析。采用反相微乳液体系制备出了纳米氧化铝并探讨了反相微乳液法的形成机理。最后论述了对纳米氧化铝进行表面改性的必要性和可行性。本文以Al（NO₃）₃·9H₂O和氨水为原料，采用直接沉淀法制备出了氢氧化铝干凝胶经过高温煅烧合成纳米级的α-Al₂O₃粉末，借助于TG／DTA和X射线衍射等手段研究了在不同Al（OH）₃干凝胶样品的煅烧过程中亚稳态Al₂O₃的相变过程。着重研究了干凝胶中残留的NH₄NO₃和制备过程中添加的α-Al₂O₃籽晶对Al₂O₃相变的影响并分析了两者降低Al₂O₃相变温度的机理。采用聚乙二醇辛基苯基醚／正丁醇／环己烷／水溶液形成的体系，用反相微乳液法合成了Al₂O₃纳米粒子。水相／表面活性剂摩尔比ω₀和煅烧温度以及煅烧时升温速率对Al₂O₃颗粒的大小、形貌和晶相有重要的影响。研究表明，减小ω₀和适当降低煅烧温度都能有效地控制颗粒的粒径，同时，煅烧时以较慢的速率2℃／min升温，更有利于生成的氧化铝向稳定的α晶相转变。采用丙烯酸化学改性和三乙醇胺机械改性两种方法对制得的纳米氧化铝进行改性。采用正交试验设计方法确定了丙烯酸化学改性的最优化的条件：改性剂浓度为3.5g/L、改性温度40℃、改性pH=5、改性时间为40min。用此最佳工艺条件优化改性，测得改性后粉体的亲油化度为0.507。通过红外光谱图可知，在改性后的纳米氧化铝粉体中，丙烯酸和三乙醇胺均与Al₂O₃发生了键合；且从TEM图中可以看出，改性后的Al₂O₃在有机溶剂乙醇中具有更好的分散性。更多还原

【Abstract】 The properties, applications and research situation, and preparationmethod of nanosized alumina at home and abroad has been presented inthis paper. The theoretical foundation of nanosized particles ofprecipitation reaction was reviewed, especially theoretical analysis ofpreventing agglomeration mechanism in preparing nanosized particleswas focused on. Al₂O₃ nanoparticles also have been prepared by reversemicroemulsion and the formation mechanism has been discussed. Inaddition, the necessity and possibility of surface modification ofnanosized Al₂O₃ has been discussed.α-Al₂O₃ nanocrystalline powders were synthesized by calcining thedry Al（OH）₃ gels prepared from aluminum nitrate and ammonia solutionusing precipitation method, and the transformation of metastables Al₂O₃in the process of calcining different dry Al（OH）₃ gels were studied byTG/DTA and XRD curves. Especially studied the effect of the leftNH₄NO₃ and the addedα-Al₂O₃ crystal to the phase change of Al₂O₃, andthe mechanism was dicussed too.Al₂O₃ nanoparticles have been prepared by polyethylene glycoloctylphenyl ether （Triton X-100）/n-butyl alcohol/cyclohexane/waterreverse microemulsion, molar ratio of water to surfacant （ω₀）, calcinationtemperature and heating rates play important roles on the structures andmorphologies of Al₂O₃ nanoparticles. The results show that the obtainedAl₂O₃ powder has no obvious agglomeration, narrow particle sizedistribution under the condition ofω₀=10, T=1150℃, and heating rate of2℃/min is propitious to the phase change of a stableα-Al₂O₃.The modifications of the nanosized Al₂O₃ were carried among thecrylic acid chemical modification and triethanolmine mechanicalmodification. We used orthogonal experiment to confirm the optimalcondition of crylic acid modification: the concentration of modifier is3.5g/L, the modification temperature is 40℃, the pH value is 5, and themodification time is 40min. Modification under this optimal and theoleophilic degree is about 0.507. Through the FT-IR curves of the modified Al₂O₃, new bonds were produces between the modifier andAl₂O₃, and the modified Al₂O₃ dispersed well in ethanol seen from theTEM figures.更多还原