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졸-겔법에 의한 다공성 알루미나 미분체 제조에 관한 연구: II. 물과 알콕시드의 비가 알루미나 미분체의 결정화 공정에 미치는 영향
Synthesis of Porous Al2O3 Particles by Sol-Gel Method: II. The Effect of [H2O]/[Al-alkoxide] on the Crystallization Mechanism of As-prepared Particles
Un-Yeon Hwang†
Sung-won Lee
Jung-Woon Lee
Hyung-Sang Park
Kee-Kahb Koo
Seung-Joon Yoo1
Ho-sung Yoon2
Yong-Ryul Kim3
서강대학교 화학공학과, 서울 121-742 1서남대학교 환경화학공학부, 남원 590-711 2한국자원연구소 자원활용 소재연구부, 대전 305-350 3대진대학교 화학공학과, 포천 487-711
Department of Chemical Engineering, Sogang University, Seoul 121-742, Korea 1Faculty of Environmental and Chemical Engineering, Seonam University, Namwon 590-711, Korea 2Division of Mineral Utilization and Materials, Korea Institute of Geology, Mining & Materials, Taejon 305-350, Korea 3Department of Chemical Engineering, Daejin University, Pocheon 487-711, Korea
hspark@ccs.sogang.ac.kr
HWAHAK KONGHAK, April 2001, 39(2), 206-212(7), NONE
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Abstract
알루미늄 알콕시드의 반응속도를 제어하기 위한 혼합용매와 입자제조 과정에서의 응집을 방지하기 위한 분산제로 HPC를 첨가하는 방법에 의하여 구형의 다공성 알루미나 미분체를 제조하였으며, XRD, FR-IR 및 TG-DTA 분석을 통하여 공정변수로 선정한 물과 알루미늄 알콕시드의 비가 제조된 미분체의 결정화 공정에 미치는 영향에 대하여 고찰하였다. 축중합 반응에 첨가된 물과 Al-알콕시드의 비는 제조된 미분체 및 하소 공정을 거친 미분체의 결정구조에 영향을 미침을 알 수 있었다. [H2O]/[ASB]의 비가 증가할수록 제조된 미분체는 비정질의 Al(OH)3로부터 점진적으로 AlO(OH)의 화학조성을 갖는 의사-보헤마이트로 결정성이 바뀌었다. 그리고 건조 공정을 거친 미분체의 결정성이 좋을수록 δ-와 θ-Al2O3는 저온에서 생성되었으나, α-Al2O3는 고온에서 생성되었다. 이와 같은 결과는 Al(3+)이온의 결정내에서의 배위체 변화와 관계됨을 알 수 있었다. 그리고 [H2O]/[ASB]=2의 조건에서 제조된 입자는 다른 시료와 달리 600 ℃에서 η-Al2O3로 1,100 ℃에서 α-Al2O3로 상전이 되었다.
Spherical porous alumina particles were prepared by mixed solvent to control the reaction rate of Al-alkoxide and the particle shape with hydroxy-propyl cellulose(HPC). HPC was used as a dispersant to prevent aggregation during the formation of particles. The effect of [H2O]/[ASB] ratio on the crystallization reactions of as-prepared particles was studied by XRD, FT-IR, and TG-DTA analysis. The mole ratio of water and Al-alkoxide added in the condensation reaction had an important effect on the crystal structure of as-prepared particles and the calcined particles. As the [H2O]/[ASB] ratio increase, the crystal structure of as-prepared particles was continuously varied from amorphous Al(OH)3 to pseudo-boehmite with chemical composition of AlO(OH). The samples which have higher crystallinite after drying process were transformed into the δ-and θ-Al2O3 at lower calcination temperature, but these sample were transformed into α-Al2O3 at higher calcination temperature. This result was thought to be the transformation of the coordination number of Al(3+) ion in the crystal structure. The particles prepared by [H2O]/[ASB]=2 condition crystallized to α-Al2O3 at 600℃ and converted to η-Al2O3 at 1,100℃ without intermediate phases.
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