• Korean Journal of Crystallography
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• v.14 no.2
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• pp.110-114
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• 2003

LiAl/sub 0.24/Mn/sub 1.76/O/sub 4-y/S/sub y/ (y=0, 0.02) were synthesized by the sol-gel method. Both structures were refined by Rietveld method, its structure refined as a cubic spinel, space group Fd-3m, a=8.17937(30) Å and 8.18331(19) Å respectively. Though it has been made a charge/discharge experiment above 20 times, there was no change of 3 V/4 V capacity degradation. It was considered that the volume change of MnO/sub 6/ octahedron induced by sulfur substitution plays a key role in keeping the 3 V/4 V capacity. The refined composition of the compound could be confirmed with the ICP analysis.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.323-330
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• 1998

Mixed oxide compounds of potential usefulness for fibre coatings (hexagonal celsian, $BaAl_2Si_2O_8$ and lanthanum hexaluminate, $LaAl_{11}O_{18}$) or for matrix materials (yttrium aluminium garnet, $Y_3Al_5O_{12}$) were prepared by hybrid sol-gel synthesis and their thermal crystallisation was monitored by thermal analysis, X-ray diffraction and multinuclear solid state MAS NMR. All the gels convert to the crystalline phase below about $12200^{\circ}C$, via amorphous intermediates in which the Al shows and NMR resonance at 36-38 ppm sometimes ascribed to Al in 5-fold coordination. Additional information about the structural changes during thermal treatment was provided by $^{29}Si$, $^{137}Ba$ and $^{89}Y$ MAS NMR spectroscopy, showing that the feldspar framework of celsian begins to be established by about $500^{\circ}C$ but the Ba is still moving into its polyhedral lattice sites about $400^{\circ}C$ after the sluggish onset of crystallization. Lanthanum hexaluminate and YAG crystallise sharply at 1230 and $930^{\circ}C$ respectively, the former via $\gamma-Al_2O_3$, the latter via $YAlO_3$. Yttrium moves into the garnet lattice sites less than $100^{\circ}C$ after crystallisation.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2191-2197
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• 2018

To remove tar and produce environment-friendly $H_2$, one of the promising routes is the sorption-enhanced steam reforming (SESR) process, in which the $CO_2$ sorbent is a key element. We prepared the $CO_2$ sorbents with $Ca_{12}Al_{14}O_{33}$ as carrier with various methods. Their characterizations were examined, and the sample prepared by solgel (SG) method showed the strongest CaO and $Ca_{12}Al_{14}O_{33}$ phases and the most excellent pore structure among all the samples. Then, a thermogravimetric experiment was conducted, and the results showed that the sample prepared by sol-gel (SG) method had the best $CO_2$ adsorption capacity and excellent long-term cyclic stability. Finally, the sorbent was used into the steam reforming experiments of tar. Under the action of the sorbent, the reforming reaction was enhanced in-situ, with the $H_2$ yield and concentration improved obviously, and especially, $H_2$ concentration can reach over 98.85%.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.1-7
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• 2017

Particle reinforced composites are materials that have enhanced physical properties by adding particle reinforcements to polymer materials and have been applied to a wide range of fields such as the aerospace, bio-technology and automative industry. In this study, particle reinforced composites were prepared by mixing $SiC/Al_2O_3$ to the vinyl ester as the thermoset resin. The purpose of this study is to evaluate mechanical properties and fracture behavior by the tensile test and single edge notch specimen according to the addition ratio of reinforcement. Addition of 1 and 2 wt% of the particle reinforcement to the vinyl-ester resin was effective for the strength improvement. However, when it was more than 3 wt%, its strength was decreased. Also the highest elastic modulus obtained as 3.19 GPa was found at the 2 wt% addition of reinforcement. Futhermore the fracture toughness was evaluated by the energy release rate and the maximum critical energy release rate was obtained when 1 wt% reinforcement. The results show that the limit of adding of $SiC/Al_2O_3$ for improvement of the mechanical and fracture performance is 2 wt% reinforcement particles.

• Korean Journal of Materials Research
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• v.12 no.3
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• pp.205-210
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• 2002

The HPS(High Porosity Support, 39.3%) and the LPS( Low Porosity Support, 18.7%) were fabricated to investigate the phase transformation and the chance of microstructure with porosity of alumina support. Alumina sol was made using aluminum tri-sec $butoxide(ATSB,\; Al(O-Bu)_3)$, the membrane on porous support with different porosity and the membrane without support were fabricated. The $\theta$-to ${\alpha}-A1_2O_3$ phase transformation in the membranes was investigated using thin film X-ray diffraction (XRD), and the change of microstructure was observed using scanning electron microscopy(SEM). XRD patterns showed that the membrane on LPS and HPS had 10$0^{\circ}C$, 5$0^{\circ}C$ higher $\theta$-to ${\alpha}-A1_2O_3$ transformation temperature compared to the unsupported membrane. A similar effect was also observed in microstructure of the membranes, theoritical temperature difference were 97$^{\circ}C$ and 44$^{\circ}C$ by Crapeyron equation.

• Proceedings of the Membrane Society of Korea Conference
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• 1992.04a
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• pp.60-60
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• 1992

알루미나 분리막이 세라믹 분리막의 연구개발 초기단계부터 많은 사람들에 의해 연구되어온 반면, TiO$_2$ 및 ZrO$_2$ 분리막에 관한 연구는 상대적으로 관심이 적었고 따라서 그 내화학성및 투과특성의 우수함이 밝혀진 것도 최근의 일이다. TiO$_2$ 및 ZrO$_2$ UF 분리막의 제조방법으로는 $Al_2O_3$ 의 경우와 마찬가지로 대부분 졸-겔 공정이 이용되고 있다.

• Journal of the Korean Ceramic Society
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• v.28 no.11
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• pp.865-872
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• 1991

LAS (lithium aluminosilicate) sol was synthesized using the hydrolysis-condensation reaction of TEOS, chelated Al(OBus)3 and LiNO3 with H2O in alcohol (ethanol+2-propanol) medium. Lowering Li content by a factor of 1/2 significantly enhanced densification and retarded the crystallization of LAS gel by ~30$0^{\circ}C$. Dense LAS specimen with essentially pore-free microstructure was obtained by sintering the sol-gel derived gel at 80$0^{\circ}C$ for 4 h and annealing at 120$0^{\circ}C$ for 2 h. Similary, a mixed colloidal processing was attempted as a convenient, alternative route for the fabrication of dense LAS sintered body. The $\beta$-spodumene seeding (~0.8 ${\mu}{\textrm}{m}$) in the sol-gel derived LAS modified the sequence of phase transformations and lowered the temperature of crystallization by ~12$0^{\circ}C$. Combining the epitaxial seeding with the sol-gel process, we could lower the crystallization temperature to the sintering temperature range (~80$0^{\circ}C$) and, demonstrate a possibility of making the viscous sintering/crystallization as a continuous as a continuous unit process.

• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.209-214
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• 2007

Sr hexaaluminate($Sr_{1-x}La_xMnAl_{11}O_{19-\alpha}$) were prepared by sol-gel method of metal alkoxide with 1-butanol or ethylene glycol as a solvent. The physical properties of prepared hexaaluminates were examined by TG/DTA, XRD and $N_2$ adsorption. When ethylene glycol was used as a solvent, the decomposition reaction and dehydroxylation reaction was observed above $400^{\circ}C$ and the temperature of the formation of a crystal structure of hexaaluminate was also increased resulting in small specific surface area and low catalytic activity of methane compared to Sr-hexaaluminate with 1-butanol.

• Applied Chemistry for Engineering
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• v.21 no.3
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• pp.333-336
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• 2010

Fe/$Al_2O_3$ granules with various compositions were prepared by combining sol-gel with oil drop method for Fishcer-Tropsh reaction to produce light olefin from synthesis gas. The granules was characterized and employed as a catalyst in the reaction. The surface area of granules was decreased with increasing Fe concentration. Especially, granule with 1.5 of Al/Fe ratios showed the highest CO conversion. However, the olefin selectivity was hardly affected by Al/Fe ratio. K concentration of granule gave a significant effect on catalytic performance. Initial CO conversion and olefin selectivity were increased with K concentration. However, the catalyst with higher K concentration was deactivated rapidly.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.585-592
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• 1988

Aluminum sec-butoxide was synthesized from aluminum foil and alcohol. The characteristics of the alumina powder prepared from the synthesized alkoxide by the Yoldas method were studied. As a result of measuring the synthesized aluminum sec-butoxide by GC, the purity of the synthesized alkoxide was 98.7% on the basis of commercial alkoxide and the yield was 78.5%. A127-MASNMR analysis shows that powders dried at 9$0^{\circ}C$ and $\alpha$-Al2O3 have 6-cordinated structure and ${\gamma}$-Al2O3 has 4-coordinated structure. The characteristics of alumina powder prepared from the synthisized alkoxide showed the same characteristics with the alumina powder prepared from the commercial alkoxide.