(The) influence of metal ions on the synthesis of MeAPO-5 (Me = Co, Mg) in the presence of foreign anions = 외부 음이온이 존재할 때 금속 이온이 MeAPO-5 (Me = Co, Mg) 합성에 미치는 영향

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Metal-substituted type 5 aluminophosphate structures ; MnAPO-5, MAPO-5, CoAPO-5 have been prepared hydrothermally in a buffer solution consisting of various acid and a high concentration of template. By adding an anion before the addition of metal source, the formation of metal oxide as well as the interaction between metal ion and gel can be controlled. Using various anion, MAPO-5, MnAPO-5, and CoAPO-5 crystals with pure phase were obtained at high concentration of template and metal ion. The anion added to the reaction mixture played an important role in decreasing the interaction of the metal ions with the gel and in keeping the initial pH of the mother liquor. There was almost no change in the pH of the reaction mixture during the preparation. The most suitable pH range to synthesize single crystals of MeAPO-5 (Me = Co, Mg, Mn) was found to be around pH 5.5. The morphologies of the as-synthesized MeAPO-5 crystals were strongly dependent on the pH of the solution. The size of the crystals increased with increasing metal contents and decreased with increasing the strength of stability constant. Owing to the roles of anions, MeAPO-5 crystals were obtained at high concentrations of template and metal ion. In the case of as-synthesized CoAPO-5 samples, the aligned crystals show a slightly different absorption in UV-VIS spectra. Considering the AFI framework, this difference in adsorption seems to arise from the character of cobalt ions in framework of CoAPO-5. Ion exchanged MAPO-5 and MnAPO-5 were prepared by ion-diffusion method and characterized by means of XRD, EPR and DRS. In as-synthesized MnAPO-5, most of manganese ions was in Mn(II) state but diffuse reflectance spectrum shows some of Mn ions are present as Mn(III) in calcined MnAPO-5. The EPR spectrum of as-synthesized MnAPO-5 shows well resolved sextet hyperfine lines at g = 2.0, a g value expected from Mn(II) in octahedral or tetrahedral structure. In ion-exchanged MAPO-5 with Mn(II), shows a peak at g...
Advisors
Jhon, Mu-Shik전무식
Description
한국과학기술원 : 화학과,
Publisher
한국과학기술원
Issue Date
1996
Identifier
108919/325007 / 000925195
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학과, 1996.8, [ viii, 107 p. ]

Keywords

Synthesis; Anion; MAPO-5; CoAPO-5; Single crystal; CoAPO-5; MAPO-5; 단결정; 합성; 음이온

URI
http://hdl.handle.net/10203/31439
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=108919&flag=dissertation
Appears in Collection
CH-Theses_Ph.D.(박사논문)
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