• 대한화학회지
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• 제33권2호
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• pp.263-270
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• 1989

금속알루미늄 조각과 alcohols을 반응시켜 Al-alkoxides를 합성하였으며 이것을 가수분해하여 얻은 Al-hydroxides와 시약 AlCl3로부터 얻은 Al-hydroxides를 여러 온도에서 소성하여 여러 상의 고순도 $Al_2O_3$를 제조하였다. 제조한 ${\gamma}$와 ${\eta}$상 알루미나의 촉매적 특성을 알아보았고, $Al(OH)_3$로부터 ${\alpha}-Al_2O_3$의 생성과정을 속도론적으로 고찰하였다.

• The Korean Journal of Ceramics
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• 제1권3호
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• pp.137-142
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• 1995

Monodispersed $Al_2O_3-TiO_2$ Powder was prepared by metal-alkoxide hydrolsis. A homogeneous nucleation/growth occurred in the solutions containing ethanol, butanol and acetonitrile, and resulted in spherical, submicrometer-sized powder. The titania and the alumina crystals were formed at $800^{\circ}C$ and $1000^{\circ}C$, respectively. These crystala were subsequently reacted each other beyond $1320^{\circ}C$ and formed $Al_2TiO_5$. The relative densities of sintered bodies prepared with as-received powder were examined at the temperature range of 1300-$1500^{\circ}C$ and they were about 79% at $1300^{\circ}C$. The formation of aluminum titanata decreased the relative density at the temperature range of 1300-$1450^{\circ}C$, and at above $1450^{\circ}C$, the relative density started to increase again. It was observed that $\alpha-Al_2O_3$-doped aluminum titanate was more stable than pure aluminum titante at $1200^{\circ}C$.

• 한국세라믹학회지
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• 제44권6호
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• pp.325-330
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• 2007

High porous AlO(OH) gel is used in precursor of ceramic material, coating material and porous catalyst. For use of these, not only physiochemical control for particle morphology, pore characteristic and peptization but also studies of synthetic method for preparation of high porous AlO(OH) gel were required. In this study, high porous AlO(OH) gel was prepared through the aging and filtration process of aluminum hydroxides gel precipitated by the hydrolysis reaction of $Na_2CO_3$ solution and $Al_2(SO_4)_3$ and $Na_2SO_4$ mixed solution. In this process, optimum synthetic condition of AlO(OH) gel having excellent pore volume as studying the effect of hydrolysis pH on gel precipitates has been studied. Hydrolysis pH brought about numerous changes on crystal morphology, surface area, pore volume and pore size. Physiochemical properties of gel were investigated as using XRD, TEM, TG/DTA, FT-IR and $N_2$ BET method.

• 한국세라믹학회지
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• 제41권11호
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• pp.864-871
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• 2004

폐 염화알루미늄(AlCl$_3$) 수용액과 수산화나트륨(NaOH) 용액의 가수분해 반응에 의해 무정형의 수산화알루미늄 겔을 석출시키고, 이를 숙성하여 다공성 유사베마이트(pseudo-boehmite) 겔을 제조하였다 pH를 7.6～11.6 범위로 조절하고 반응온도를 60～10$0^{\circ}C$로 변화시켜 2～24시간 숙성시켰을 때, 겔 침전물의 결정변화, 적외선흡수스펙트럼의 변화, 비표면적 및 기공구조의 변화를 조사하여 최대 기공부피를 갖는 유사베마이트 겔의 제조조건을 확립하였다. pH 7.6～9.6 범위에서 석출된 겔 침전물로부터 250～357 $m^2$/g 정도의 비표면적과 0.4～0.74 cc/g의 기공부피 그리고 58～l14$\AA$의 평균기공크기를 갖는 다공성 유사베마이트가 제조되었으며, pH 10.6～11.6 범위에서 석출된 겔 침전물로부터는 기공이 거의 없는 베이어라이트(bayerite)가 제조되었다.

• 한국세라믹학회지
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• 제29권8호
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• pp.667-673
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• 1992

The alumina-zirconia composite powders of core particle ZrO2 coated with Al2O3 were prepared by the hydrolysis-deposition of the mixed aluminum salt solution of Al2(SO4)3-Al(NO3)3-Urea. The effects of hydrolysis reaction and coating parameters on characteristics of coated powders and composites were also investigated. The degree of coating could be estimated from the ratio of tetra-/mono-ZrO2 present at the room temperature after heat-treating coated powders at 120$0^{\circ}C$ and the result of TEM observations. When the content of ZrO2 in the dispersed coating system, the coating time, and the volume ratio of water/solution were 50 mg/g, 180 min, and 5, respectively the coating efficiency was maximum (the ratio of tetra-/mono-ZrO2 was 87/13). The relative densities of coated Al2O3-ZrO2 composites sintered at 1$650^{\circ}C$ for 4 hrs were about 91~98% and the maximum ratio of tetra-/mono-ZrO2 in Al2O3-20wt% ZrO2 composites was 62/38.

• 한국세라믹학회지
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• 제31권8호
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• pp.893-901
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• 1994

In this study, AlN powder of fine particle size and of high purity was synthesized by the carbothermal reduction-nitridation of monodisperse, spherical Al(OH)3 which had been prepared by sol-gel method using Al(O-sec-C4H9)3 as the starting material. Depending on the mixing order and kinds of reducing agents, the optimum condition for the preparation of AlN was determined as follows. AlN single-phase was produced by the carbothermal reduction-nitridation of (1) Benzene-washed Al(OH)3 and the reducing agent, carbon, which was mixed in a ball mill: for 5 hours at 140$0^{\circ}C$ under NH3 atmosphere; (2) The mixture prepared by hydrolysis of alkoxide solution into which carbon had been dispersed beforehand: for 5 hours at 135$0^{\circ}C$ ; (3) Al(OH)3 Poly(furfuryl alcohol) composite powder: for 2.5 hours at 135$0^{\circ}C$; (4) The mixture of Al(OH)3 and polyacrylonitrile: for 5 hours at 140$0^{\circ}C$. Addition of CaF2 increased the nitridation rate when carbon or polyacrylonitrile was used as the reducing agent; but it had no effect on the nitridation rate when furfuryl alcohol was used as the reducing agent.

• 한국세라믹학회지
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• 제26권1호
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• pp.100-108
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• 1989

Aluminum hydroxides were prepared by the alkoxide hydrolysis method using Al-isopropoxide as a starting material and NH4OH as a catalytic agent. When Al-isopropoxide was hydrolyzed in a H2O-NH3 system, only Al(OH)3 was obtained over all pH values. However, AlOOH was formed besides Al(OH)3 when Al-isopropoxide was hydrolyzed in a H2O-NH3-isopropyl alcohol system. The AlOOH/Al(OH)3 ratio was increased as the isopropyl alcohol content was increased. The hydroxides, Al(OH)3 and AlOOH, obtained in this study and the commerical products, $\alpha$-Al2O3 and AlOOH were subjected to the carbothermal reduction and nitridation reaction to product AlN powder, using carbon black as a reducing agent under N2 atmosphere at various temperatures. AlN was synthesized from the obtained Al(OH)3 and the commercial AlOOH at 145$0^{\circ}C$, however, synthesized from the obtained AlOOH and the commercial alpha-alumina at 135$0^{\circ}C$. The temperature difference is assumed to be attributed to the reactivity of those powders. AlN powder prepared from the Al-isopropoxide was observed to have the narrower particle size distribution than that prepared from the commercial $\alpha$-Al2O3 or AlOOH.

• Journal of Pharmaceutical Investigation
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• 제34권3호
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• pp.193-199
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• 2004

The decreasing effect of wrinkle on the pressure sensitive adhesive hydrogel patches containing ulmi cortex extract and sorbitol as the drug for anti-wrinkle were investigated. In this study, hydrogels were prepared by the crosslinking reaction of acrylic polymers and aluminum ions produced by L(+)-tartaric acid hydrolysis of the dihydroxy aluminum aminoacetates. The inhibition concentration of ulmi cortex extract on the collagenase exhibited at 0.01%. Furthermore, the moisturizing effect of hydrogel patches formulated with sorbitol was higher than that without it. In vivo animal test in hairless mouse showed that the ulmi cortex-loaded hydrogel patches had about 31.2% of anti-wrinkle effect compared to blank (before attaching the patches). Human test showed that only 33% of subjects showed the decreasing of wrinkle during 8 weeks. In conclusion, the model pressure sensitive adhesive hydrogel patches in this study would be pharmaceutically applicable for the wrinkle treatment on the facial skin.

• Bulletin of the Korean Chemical Society
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• 제33권6호
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• pp.1962-1966
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• 2012

Boehmite sols have been prepared by crystallization of amorphous aluminum hydroxide gel obtained by hydrolysis and peptization of aluminum using acetic acid. The size of the boehmite crystallites could be controlled by Al molar concentration in amorphous gel by means of controlling grain growth at nucleation stage. The size of boehmite increases as a function of Al molar concentration. With increasing boehmite crystallite size, the $d_{(020)}$ spacing and the specific surface area decreases, whereas the pore volume increases along with pore size. Especially, the pore size of the boehmite sol particles is comparable to the crystallite size along the b axis, suggesting that the fibril thickness along the b axis among the crystallite dimensions of the boehmite contributes to the pore size. Therefore, the physical properties of boehmite sols can be determined by the crystallite size controlled as a function of initial Al concentration.

• 한국세라믹학회지
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• 제43권9호
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• pp.575-581
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• 2006

To precipitate the complex gel of flux and aluminum hydroxides gel, aqueous solution of the mixture of $Na_2CO_3\;and\;Na_2PO_4{\cdot}12H_2O$ was added with stirring in aqueous solution of the mixture of $Al_2(SO_4)_3{\cdot}14{\sim}18H_2O,\;Na_2SO_4$, and then the complex gel was aged in $0{\sim}30h\;at\;90^{\circ}C$. As aging time passed, the aluminum hydroxides was grown into the acicular AlO(OH) gel. Also, aging time had an effect on physical properties of the AlO(OH) gel and on crystal growth of the flaky ${\alpha}-Al_2O_3$ prepared by molten-salt precipitation. In this study, the complex gel was crystallized in temperature range of $400{\sim}1,200^{\circ}C$ after drying at $110^{\circ}C$, and then it was investigated to effect of aging time on precipitation temperature, size, thickness, morphology and particle size distribution of the flaky ${\alpha}-Al_2O_3$ crystal. As aging time passed, the flaky a${\alpha}-Al_2O_3$ crystal showed a tendency toward an increase in size and thickness as result from an increase in BET surface area and pore volume of the acicular AlO(OH) gel.