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알칼리 침전제에 의해 제조된 아연 중간생성물 및 산화아연 결정화
장대환,김보람,김대원,Jang, Dae-Hwan,Kim, Bo-Ram,Kim, Dae-Weon 한국결정성장학회 2021 韓國結晶成長學會誌 Vol.31 No.6
ZnO는 출발물질인 황산아연과 알칼리 침전제인 NaOH와 Na<sub>2</sub>CO<sub>3</sub>에 의해 생성된 아연 중간생성물의 변이 거동과 결정화 조건에 따라 제조하였다. ZnO 결정화를 위해 아연 중간생성물인 Zn<sub>4</sub>(OH)<sub>6</sub>SO<sub>4</sub>·H<sub>2</sub>O, Zn<sub>5</sub>(OH)<sub>6</sub>(CO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O를 각각 400℃, 800℃에서 1시간 하소하였고, 하소 온도는 열중량 분석을 기반으로 하였다. 아연 중간생성물인 Zn<sub>4</sub>(OH)<sub>6</sub>SO<sub>4</sub>·H<sub>2</sub>O은 400℃에서 Zn<sub>4</sub>(OH)<sub>6</sub>SO<sub>4</sub>·H<sub>2</sub>O, ZnO 결정상이 혼재됨을 확인하였고, 800℃에서 완전히 열분해되어 순수한 ZnO만 형성되었다. Na<sub>2</sub>CO<sub>3</sub>와 반응하여 생성된 아연 중간생성물인 Zn<sub>5</sub>(OH)<sub>6</sub>(CO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O는 400℃ 이상에서 완전한 ZnO의 결정상을 확인하였다. Na<sub>2</sub>CO<sub>3</sub>와 반응을 통해 상대적으로 낮은 하소 온도에서 나노 입자의 ZnO를 합성할 수 있었다. ZnO was synthesized according to the transformation behavior and crystallization conditions of Zn-intermediate obtained by zinc sulfate as a precursor and NaOH, Na<sub>2</sub>CO<sub>3</sub> as a alkali agents. For ZnO crystallization, Zn<sub>4</sub>(OH)<sub>6</sub>SO<sub>4</sub>·H<sub>2</sub>O and Zn<sub>5</sub>(OH)<sub>6</sub>(CO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O as a Zn-intermediate were calcined at 400℃ and 800℃ for 1 h, respectively, based on decomposition temperature from TGA. Zn<sub>4</sub>(OH)<sub>6</sub>SO<sub>4</sub>·H<sub>2</sub>O was confirmed to have mixed Zn<sub>4</sub>(OH)<sub>6</sub>SO<sub>4</sub>·H<sub>2</sub>O and ZnO at 400℃, and was completely thermally decomposed at 800℃ to form ZnO phase. The prepared Zn<sub>5</sub>(OH)<sub>6</sub>(CO<sub>3</sub>)<sub>2</sub>·H<sub>2</sub>O as a Zn-intermediate by the reaction with Na<sub>2</sub>CO<sub>3</sub> was transformed to a complete ZnO crystallization over 400℃. Nano-sized ZnO can be synthesized at a relatively lower calcination temperature through the reaction with Na<sub>2</sub>CO<sub>3</sub>.
전기방사된 주석산화물 나노섬유의 공정 변수에 따른 직경 및 형상 제어 연구
장대환,이재은,좌용호,이영인,Jang, Dae-Hwan,Lee, Jae-Eun,Choa, Yong-Ho,Lee, Young-In 한국재료학회 2014 한국재료학회지 Vol.24 No.12
Diameter-controlled tin oxide nanofibers have been successfully prepared using electrospinning and a subsequent calcination process; their diameters, morphologies, and crystal structures have been characterized. The diameters of the as-spun nanofibers can be decreased by lowering the concentration of a polymer and a tin precursor in the electrospinning solution because of the decrease in the solution viscosity. The crystal structure of the nanofibers calcined at various temperatures from $200^{\circ}C$ to $800^{\circ}C$ has been proved to be the tetragonal rutile of tin oxide; crystallinity is improved by increasing the temperature. However, nanofibers with lower concentrations of tin precursor do not maintain their fibrous structures after calcination at high temperatures. In this study, the effect of the relationship between the precursor concentration and the calcination temperature on the diameter and the morphology of the tin oxide nanofiber has been systematically investigated and discussed.