• Applied Microscopy
• /
• 제32권4호
• /
• pp.311-317
• /
• 2002

입자 크기에 따라 상전이 경로가 달라지며 매우 큰 응집체로 존재하는 gibbsite 분말과 같은 재료의 정량적인 전이 구조 분석의 전제로서 입자 크기가 선택적인 TEM 시편의 준비가 절실히 요구된다. 입자 크기 선택성을 실현한 TEM 시편 준비의 방법론을 확립하기 위한 방안으로서 본 실험이 전개되었다. 약 1 wt%의 gibbsite 원료 분말을 에탄올 용매에 혼합 한 뒤, ball-milling에 의해 조분쇄 처리를 하고 증류수에 1 : 19의 비로 희석된 분산 조제, Darvan C, 0.25 vol%의 첨가와 함께 ultrasonic 처리를 하여 gibbsite suspension을 만들었다. 제조된 gibbsite suspension의 누적 농도 변화 관찰에 의한 침강 시간의 조정 후 정적 침강 분리에 의해 nm 크기별로 분리된 TEM 시편을 만들 수가 있었다. 시편의 전체적인 양상은 SEM으로 관찰하였고 개개 입자들의 morphology 는 TEM으로 분석하였다. 또한, 공정 과정 중의 상변화 가능성을 검토하기 위해 XRD 분석을 실시하였다.

• 한국결정성장학회지
• /
• 제22권6호
• /
• pp.286-290
• /
• 2012

알루미늄 에칭 폐액으로부터 boehmite(AlOOH) 분말을 합성하였다. 폐액에서 침전되어 있는 결정상은 gibbsite ($Al(OH)_3$)였으며, 산을 이용하여 pH를 조절한 결과 pH가 7~8 영역에서 boehmite 결정상이 얻어졌다. 침전 분말에 남아 있는 Na 이온을 제거하고자 세척공정을 진행하여 boehmite 분말을 얻었다. 합성한 분말의 평균입경은 약 40 nm이었다. 또한 열처리 온도가 증가함에 따라 boehmite는 ${\gamma}-Al_2O_3$와 ${\delta}-Al_2O_3$, ${\Theta}-Al_2O_3$를 거쳐 ${\alpha}-Al_2O_3$ 결정상으로 상전이가 일어났다.

• 한국세라믹학회지
• /
• 제35권10호
• /
• pp.1085-1093
• /
• 1998

Amorphous alumina powder prepared by the fast calcination of aluminum trihydroxide(Al(OH)3 gibbsite) for 0.5 second at 580$^{\circ}C$ was investigated rehydration propeties. Phase composition crystal size and mor-phology surface area pore volume and pore size distribution of pesudo-boehmite and bayerite crystals changed with temperature time water/alumina ratio and particle size when amorphous alumina rehydrated with water. Phase compositions were examined with XRD and DTA and crystal sized morphologies were investigaed with SEM and TEM. Also rehydration properties of amorphous alumina were in-vestigated by measuring the surface area pore volume and pore size distribution.

• 한국분말재료학회지
• /
• 제12권2호
• /
• pp.122-130
• /
• 2005

Layered silicate was synthesized at hydrothermal condition from silica adding to various materials. Nano-clay was synthesized by intercaltion of various amine compounds into synthetic layered silicate. The products were analysed by XRD, SEM, and FT-IR in order to examine the condition of synthesis and intercalation. From the results, it was confirmed that kaolinite was synthesized from precipitated silica and gibbsite at $220^{\circ}C$ during 10 days, and hetorite was synthesized from silica sol at $100^{\circ}C$ during 48 h. Na-Magadiite was synthesized from silica gel at $150^{\circ}C$ during 72 h, and Na-kenyaite was synthesized from silica gel at $160^{\circ}C$ during 84 h. Nano-clay was prepared using synthetic layered silicate intercalated with various amine compounds. Kenyaite was easily intercalated by various organic compounds, and has the highest basal-spacing value among other layered silicates. Basal-spacing was changed according to the length of alkyl chain of amine comopounds. Polymer can be easily intercalated by dispersion with large space of interlayer. Finally, epoxy/nano-clay nanocomposite can be easily prepared.

• 한국세라믹학회지
• /
• 제25권2호
• /
• pp.111-116
• /
• 1988

Aluminum hydrates were prepared by precipitation method using Al2(SO4)3$.$18H2O as a starting material and NH4OH as precipitation agent. The phases of aluminum hydrate were changed from amorphous aluminum hydrate to pseudo-boehmite of AlOOH form and bayerite, gibbsite, hydragillite and norstrandite of Al(OH)3 form with increasing pH. As pH increased, agglomeration phenomena were reduced. Aluminum hydrates of AlOOH and Al(OH)3 form represented dehydration of structural water near 175$^{\circ}C$ and 385$^{\circ}C$, and 280$^{\circ}C$, respectively. As the ratio of Al(OH)3 to AlOOH increased, specific surface area was reduced.