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TGA를 이용한 침상형 Goethite의 탈수 및 환원 기구에 관한 연구

A Study on the Dehydration and Reduction Kinetics of Acicular Goethite by TGA Method

김영호 고재천 이정민

Kim Y Koh J Lee J

HWAHAK KONGHAK, June 1989, 27(3), 278-285(8), NONE

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Abstract

열천칭 방법(Thermogravimetric Analysis)에 의해 침상형 goethite로부터 고밀도 자기기록용 α-Fe를 얻기 위한 탈수 및 환원반응 기구를 관찰하였다.
실험결과 탈수 및 환원반응 경로를 알 수 있었으며, 각 반응기구의 차수, 활성화에너지 및 빈도인자계수를 구하였다. 실험은 상온에서 500℃까지 일정속도로 가열하는 승온방식에 의하였으며 수소농도를 바꾸어 가며 행하였다.
결과로 goethite로부터의 α-Fe 전환은 탈수반응을 거쳐 α-Fe₂O₃ 및 α-Fe₃O₄ 의 중간단계를 거치는 환원반응임을 확인하였으며, 환원단계인 α-Fe₃O₄에서 α-Fe 전환반응은 수소의 농도에 큰 영향을 받았다. 그때의 반응치수는 수소에 대하여 2.60 차이고 α-Fe₃O₄ 에 대하여는 0.1차이었으며, 빈도인자계수 및 활성화에너지는 각각 2.76×10¹⁴ 및 50kcal/gmol이었다.
또 goethite의 탈수반응에서 반응치수는 goethite에 대하여 0.46이었으며 빈도인자계수 및 활성에너지는 5.10×10⁹ 및 26.2kcal/gmol이었다.

Kinetics of goethite dehydration and reductions were studied by TGA(thermogravimetric analysis)method. The mechanism for dehydration and reduction of goethite were elucidated. Also, reaction orders, activation energies and frequency factors were obtained in each step. Experiments were done between ambient temp. and 500℃, and the heating rate was kept as 1℃/min. Consequently, α-Fe₃O₄ and α-Fe₃O₄ were obviously appeared as interme-diates in overall reaction phat. And reduction of α-Fe₃O₄ was 2.60 and 1.0, respectively. Also, the frequency fac-tor and activation energy were 2.76×10¹⁴ and 50kcal/gmol, respectively. In the goethite dehydration step, reaction order, frequency factor and activation energy were 0.46, 5.1×10⁹ and 26.2kcal/gmol, respectively.

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