• 한국세라믹학회지
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• 제28권7호
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• pp.568-576
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• 1991

The powder characterization and sintering behavior of alkoxide-derived alumina powders prepared by esterification were investigated. The dried powders were calcined at 700$^{\circ}C$, 900$^{\circ}C$, 1080$^{\circ}C$, 1170$^{\circ}C$ for 1 h. and the resulting crystalline forms were amorphous, {{{{ gamma }} phase, {{{{ theta }}+{{{{ alpha }} phase, and {{{{ alpha }} phase, respectively. The sinterability was best in the case of being calcined at 1170$^{\circ}C$. It was most effective to disperse sintering additive in the initial stage from which acetate was formed. At 1600$^{\circ}C$ for 4 h, 98.5% of relative density was obtained when MgO and Fe2O3 were simultaneously doped, and dense sintered body whose density was near theoretical value was obtained when heating schedule was controlled.

• 한국응용과학기술학회지
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• 제16권2호
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• pp.163-170
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• 1999

Spherical alumina powders were prepared by the controlled hydrolysis of aluminum iso-propoxide in a solution consisting of n-octyl alcohol and acetonitrile. As aluminum alkoxide's concentration increased, the particle size was increased and size distribution was more broad. As-prepared particle morphology was not spherical when acetonitrile volume fraction was increased over than 60%. As-prepared amorphous powders crystallized to ${\gamma}$-alumina at $1000^{\circ}C$ and converted to ${\alpha}$-alumina at $1150^{\circ}C$. The particle morphology was retain after crystallization ${\alpha}$-alumina. When aluminum iso-propoxide was used as aluminum source, the optimum preparation condition of spherical alumina was 0.1M AIP, 0.2M H2O, $0.1g/{\ell}$ HPC with a volume fraction (1/1) of the n-octyl alcohol/acetonitrile, 10min of reaction time and 30min of aging time.

• 한국세라믹학회지
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• 제26권3호
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• pp.445-451
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• 1989

Hydrolysis of aluminum isopropoxide with excess water in the presence of excess isopropyl alcohol resulted in the formation of boehmite in independence of temperature of hydrolysis and aging. Stoichiometric and substoichiometric amount of water hydrolyzed aluminum isopropoxide to pseudo-boehmite and amorphous one, respectively. $\alpha$-Al2O3 with 0.3${\mu}{\textrm}{m}$ in median size was produced by calcination of boehmite, bseudo-boehmite and amorphous boehmite at 125$0^{\circ}C$, 120$0^{\circ}C$, and 115$0^{\circ}C$ for one hour, respectively. Singnificant reduction in particle size was found during transition from $\theta$-Al2O3 to $\alpha$-Al2O3. $\alpha$-Al2O3 produced in this study was relatively uniform spherical and its purity was found to be over 99.9%.

• 한국세라믹학회지
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• 제28권2호
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• pp.153-159
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• 1991

Polymeric alumina sol and polymeric silica sol were synthesized from aluminum sec-butoxide and tetraethyl orthosilicate, respectively as starting materials. A clear mullite sol was obtained by mixing these sols. When the mullite sol had a proper viscosity which was dependent on drying time, the fibers were fabricated by spinning. The optimum viscosity for fabrication of mullite fibers was 103-104 cps, and the fibers with various sizeswere made using the sols. The mullite was a major phase of the calcined fibers and the diameters of the fibers were about 50$\mu\textrm{m}$.

• 한국세라믹학회지
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• 제33권10호
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• pp.1147-1155
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• 1996

• 자원리싸이클링
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• 제28권1호
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• pp.15-22
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• 2019

습식법으로 고순도 알루미나를 제조할 수 있는 알콕사이드 가수분해법, 암모늄 명반의 열분해법, 암모늄 알루미늄탄산염(AACH) 열분해법을 소개하였다. 상기 세 공정으로 알루미나 제조시 용액의 pH, 온도와 불순물이 알루미나의 상전이와 고순도에 미치는 영향을 조사했다. 알콕사이드와 암모늄 명반의 열분해법으로는 ${\alpha}$와 ${\gamma}$알루미나의 제조가 가능하다. 그러나 AACH 열분해법으로는 ${\gamma}$알루미나 제조는 어렵다.

• 한국세라믹학회지
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• 제28권1호
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• pp.60-66
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• 1991

The polymeric alumina sol was prepared by partial hydrolysis of aluminum sec-butoxide reacted with acetylacetone and its characteristics was investigated. The effects of alcohol solvent, acetylacetone, and acid concentration to the sol were investigated. FT-IR and Al27-MASNMR were used to study hydrolysis and polymerization reaction of aluminum complex. Synthesized sol showed the characteristics of polymeric alumina sol. To make a clear polymeric alumina sol, the optimum contents of acetylacetone, H2O and alcohol solvent were 0.4-0.6 mole, 0.25-1.25 mole, 3-5 mole per one mole alkoxide respectively. As a result of the Al27-MASNMR analysis, it was noted that hexa-penta-coordinated Al were main structure.

• Bulletin of the Korean Chemical Society
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• 제35권9호
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• pp.2758-2764
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• 2014

We demonstrated the synthesis of organic carbonates using alkyl/aryl 4,5-dichloro-6-oxopyridazine-1(6H)-carboxylates and alcohol in the presence of aluminum chloride. Alkyl/aryl 4,5-dichloro-6-oxopyridazine-1(6H)-carboxylates were reacted with alcohol in the presence of $AlCl_3$ in toluene at room temperature to afford the corresponding unsymmetric and symmetric organic carbonates in good to excellent yields. These are efficient and convenient processes. Alkyl/aryl 4,5-dichloro-6-oxopyridazine-1(6H)-carboxylates are solid, stable and non-toxic $CO_2/CO_2R$(Ar) source. It is noteworthy that the reaction is carry out under an ambient and acidic conditions, the easy-to prepare and readily available starting materials and the quantitative isolation of reusable 4,5-dichloropyridazin-3(2H)-one.

• 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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• 제33권10호
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• pp.1138-1146
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• 1996

Al2TiO5 powder was prepared by the sol-gel processing from th metal alkoxides ; aluminium sec-butoxide (Al(OC4H9)3 and tetraethyl orthotitanate (Ti(OC2H5)4) The particles of Al2TiO5 produced from alkoxides were measured to be below $1.5mutextrm{m}$ and mre than 90% weere below 1 ${\mu}{\textrm}{m}$ however those from commercial alumina and titania were over 0.5-7${\mu}{\textrm}{m}$ and only 60% were below 1${\mu}{\textrm}{m}$ and 90% were below 2.5${\mu}{\textrm}{m}$ Therefore Al2TiO5 powder produced from alkoxides had the narrower distributionin size than that produced from the commercial alumina and titania powders. The addition of mullite or Al2O3 powder to the prepared aluminum titanate inhibited the grain growth and this resulted in decreased and increase in density.