The Preparation Of Nanometer ¦Á-alumina And Its Modification

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.