Al2 O3 hollow microspheres without noticeable aggregation have been prepared via a facile templating route with urea-mediated precipitation. The precipitation process is different from the surfaceadsorption method whi...Al2 O3 hollow microspheres without noticeable aggregation have been prepared via a facile templating route with urea-mediated precipitation. The precipitation process is different from the surfaceadsorption method which is confined to the adsorption capacity of the template surface. TEM and SEM images indicate that most of these Al2 O3 hollow microspheres with shell thickness of tens of nanometers and diameters in a narrow range of 100-200 nm consist of a shell of closely packed nanoparticles. The optimal amount of H2 O and EtOH are 40 and 120 m L, respectively. The specific surface area, average pore size and pore volume of the Al2 O3 hollow microspheres（calcinated at 600 ℃） are 328.52 m2/g, 17.496 nm and 1.985 cm3/g, respectively. As the calcination temperature increases from 600 to 1 100 ℃, the phase composition changes from γ-Al2 O3 to θ-Al2 O3 and a-Al2 O3, and the surface morphology appears to change from a relatively rough surface formed by nanoparticles to a smooth surface formed by lamellar, which lead to the closure of pore channels and the reduction of specific surface.展开更多
Al2O3-ZrO2 microspheres were prepared by internal gelation method.The effects of Al3+on the stability of solution and performance of gel spheres were studied.Al3+had a great influence on the stability of the solutions...Al2O3-ZrO2 microspheres were prepared by internal gelation method.The effects of Al3+on the stability of solution and performance of gel spheres were studied.Al3+had a great influence on the stability of the solutions,and the more of the amount of Al3+,the shorter of the stabilization time.Because Al3+did not copolymerize with Zr4+during the sol-gel transformation,the strength of gel sphere added with Al3+was low and deformed easily as it was squeezed.The results of our experiments well verify Glasser team’s speculation and conclusions.At the same time,based on the experimental results,we prepared Al2O3-ZrO2 composite microspheres with higher content of Al2O3 by controlling the pH of the solution.The change curve of viscosity with time and the stabilization time of the solution with different Al3+dosage were given,which could provide references for industrial mass production.Samples without hydrothermal treatment cracked severely,while the samples hydrothermally treated kept structural integrity with no cracks after calcined.Al2O3-ZrO2 microspheres with no segregation and phase separation were prepared and alumina evenly distributed in the zirconia matrix.When the content of Al2O3 was low,the tetragonal phase was stable.And the cubic phase was obtained when the content of Al2O3 was more.展开更多
文摘Al2 O3 hollow microspheres without noticeable aggregation have been prepared via a facile templating route with urea-mediated precipitation. The precipitation process is different from the surfaceadsorption method which is confined to the adsorption capacity of the template surface. TEM and SEM images indicate that most of these Al2 O3 hollow microspheres with shell thickness of tens of nanometers and diameters in a narrow range of 100-200 nm consist of a shell of closely packed nanoparticles. The optimal amount of H2 O and EtOH are 40 and 120 m L, respectively. The specific surface area, average pore size and pore volume of the Al2 O3 hollow microspheres（calcinated at 600 ℃） are 328.52 m2/g, 17.496 nm and 1.985 cm3/g, respectively. As the calcination temperature increases from 600 to 1 100 ℃, the phase composition changes from γ-Al2 O3 to θ-Al2 O3 and a-Al2 O3, and the surface morphology appears to change from a relatively rough surface formed by nanoparticles to a smooth surface formed by lamellar, which lead to the closure of pore channels and the reduction of specific surface.
基金Funded by National Natural Science Foundation of China(No.91326203)。
文摘Al2O3-ZrO2 microspheres were prepared by internal gelation method.The effects of Al3+on the stability of solution and performance of gel spheres were studied.Al3+had a great influence on the stability of the solutions,and the more of the amount of Al3+,the shorter of the stabilization time.Because Al3+did not copolymerize with Zr4+during the sol-gel transformation,the strength of gel sphere added with Al3+was low and deformed easily as it was squeezed.The results of our experiments well verify Glasser team’s speculation and conclusions.At the same time,based on the experimental results,we prepared Al2O3-ZrO2 composite microspheres with higher content of Al2O3 by controlling the pH of the solution.The change curve of viscosity with time and the stabilization time of the solution with different Al3+dosage were given,which could provide references for industrial mass production.Samples without hydrothermal treatment cracked severely,while the samples hydrothermally treated kept structural integrity with no cracks after calcined.Al2O3-ZrO2 microspheres with no segregation and phase separation were prepared and alumina evenly distributed in the zirconia matrix.When the content of Al2O3 was low,the tetragonal phase was stable.And the cubic phase was obtained when the content of Al2O3 was more.
