Synthesis of Monodispersed Al2O3 and Pt-Al2O3 Hollow Microspheres by Implantation of Precursor

• Main Authors: Wei-Te Li, 李維特
• Other Authors: Wenjea J. Tseng
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/26815364949011611817

碩士 === 國立中興大學 === 材料科學與工程學系所 === 97 === This research uses C2Cl4 as a reactive solvent, AlCl3 as a precursor for Al2O3, and organic microspheres as a template in a way that the AlCl3 is implanted into surface of organic cores to form a core-shell structure. Al2O3 microspheres with hollow interiors are formed after thermal pyrolysis to remove the organic core. In addition, this research also uses C2Cl4 as a reactive solvent, AlCl3 and H2PtCl6．nH2O as precursors for synthesis of Pt-Al2O3 composite hollow particles. Two processes (processes I and II) have been used for the synthesis, and Pt-Al2O3 hollow microspheres are formed after thermal pyrolysis which removes the organic core. From the depth profile of ESCA analysis, the precursors used in the process are located beneath the surface of organic cores by an implantation of Al or Pt ions. The reaction temperature, calcination temperature and calcination time have been changed to examine the microstructure, phase transformation, and specific surface area of the hollow microspheres by TEM, FESEM, XRD, Raman and BET. The loading amount of Pt element is analyzed by ICP. From TEM analysis, the shell thickness of the Al2O3 hollow microspheres increases with the increasing reaction temperature. When the reaction temperature is held at 75oC, pores on the shell appear to decrease with the increasing calcination time, presumably caused by grain growth of α-Al2O3. From TEM and ICP results, at 1100oC, Pt loading is lower in the Process I Pt/α-Al2O3 and Pt particle size is smaller and disperses more uniform in alumina matrix. The Pt particle size is about 5nm. On the other hand, the Pt loading is higher for the Process II Pt/α-Al2O3, but the Pt particle size is larger (about 40~180nm). From Raman analyses, at 1000oC, αphase and θ phase Al2O3 are formed in the Process I Pt-Al2O3 and at 1100oC, the crystalline phase is completely transformed intoαphase. But after calcination at 1000oC, onlyαphase is formed in the Process II Pt-Al2O3. At 1100oC, the θphase is formed and theαphase is completely formed at 1200oC. From XRD results, only α-Al2O3 phase is found, but for the Process I Pt-Al2O3, the complete formation of α-Al2O3 phase occurs at 1100oC. On the other hand,αphase is formed at 1200oC for the Process II. Key word：Pt, Al2O3, organic microsphere, core-shell structure