• 한국세라믹학회지
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• 제36권4호
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• pp.410-416
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• 1999

The reactivity of three kinds of spinels which CaO-Al2O3-SiO2 slag was investigated in terms of mineral phases and microstructures. New crystal products were not formed by reaction of 12CaO.7Al2O3 in the slag with spinels and free MgO components was preferenctially dissolved into slag for MgO-rich spinel and stoichiometric spinel. Meanwhile mineral phase was changed from 12CaO.7Al2O3 to CaO.Al2O3 to CaO.2Al2O3 finally to CaO.6Al2O3 having high melting point for Al2O3 -rich spinel. The Fe-oxide component of the slag was taken up by only stoichiometric spinel grains within the spinel clinker and the trapped amount of Fe-oxide was independent of MgO content of MgO in spinel clinker the more th resistance to slag corrosion but the less resistance to slag penetration.

• 한국세라믹학회지
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• 제30권10호
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• pp.811-818
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• 1993

Al2O3/ZrO2-Spinel composites were prepared by infiltrating magnesium sulfate solution into the porous preform made from Al2O3-20wt% ZrO2 composite powders derived through an emulsion route. The microstructure and composition of the modified composites could be controlled by manipulating the presingtering temperature of the preform, infiltration time, and so on. It was found that spinel phases were concentrated near the surface than in the interior of the Al2O3/ZrO2-Spinel composites infiltrated for 6hrs, while spinel phases were uniformly distributed in the comosites infiltrated for 2 days. The relative density and fracture toughness of the composite infiltrated for 6 hrs were 98.6% and 7.2MN/m3/2, respectively.

• 한국결정성장학회지
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• 제4권3호
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• pp.325-335
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• 1994

Floating zone법으로 Spinel$(MgO.Al_2O_3)$을 성장시켰다. $MgO.Al_20_3$ spinel의 용융점은 $2135^{\circ}C$ 정도이고, 용융액으로부터 단결정을 성장시키는 방법에 있어서 매우 중용한 사항이다. Verneuil법과 RF-유도가열법을 이용한 czochralski법으로 성장시킨 경우가 보고된 바 있으나, 본 공법으로는 처음이라 사료된다. 본 연구에서는 halogen적외선 lamp를 이용한 image fur-nace에서 용융하여 아래쪽으로 하강함으로 인해 단결정을 육성시키는 floating zone법을 사용하여, $MgAl_2O_4$ spinel 단결정을 성장하였다. 또한 전이금속 이온을 doping하여 용융점의 하강 효과와 함께 적색, 녹색을 띈 단결정을 성장시켰다. 결론으로 성장계면과 용융대의 안전성에 주목하여 spinel 단결정 성장 기구를 규명하려 하였으며 성장계면이 오목함(결정쪽으로)에서 비롯되는 성장시의 양상에 대해 고찰하였다.

• The Korean Journal of Ceramics
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• 제4권4호
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• pp.363-367
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• 1998

Alumina/mica and spinel/mica composites were fabricated by sintering of compacts containing 20 mass% fluoromica ($KMg_3AlSi_3O-{10}F_2$) glass and alumina or spinel. In both composites, mica precipitated as plate-like crystals at temperatures lower than $1300^{\circ}C$ and melted at $1300^{\circ}C$ to $1400^{\circ}C$. In alumina/mica composites, alumina and glass reacted to produce spinel, and the densification progressed by the solution-precipitation of alumina. Consequently, the glass composition changed and the mica did not precipitate at temperatures higher than $1400^{\circ}C$. However, mica precipitated after a reheating process. In spinel/mica composites, the glass composition did not change. After the mica phase melted, it recrystallized during slow cooling. The relative density reached the maximum at $1500^{\circ}C$ for alumina/mica and at $1300^{\circ}C$ spinel/mica composites, and decreased at further high temperatures.

• Bulletin of the Korean Chemical Society
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• 제16권12호
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• pp.1148-1152
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• 1995

Oxidative dimerization of methane to C2-hydrocarbons was performed over lead aluminate spinel catalysts. These spinel catalysts were prepared by co-precipitation, aerogel, and sol-gel methods. The active phase of lead aluminate oxides was found to be PbAl2O4 spinel. The activities of the catalysts were strongly dependent on the preparation method as well as the composition of PbAl2O4 phase. The proper oxygen mobility of PbAl2O4 spinel oxides appeared to be important to get high catalytic activity and selectivity for C2-hydrocarbon formation.

• 한국자기학회지
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• 제15권2호
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• pp.96-99
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• 2005

Phase transition from normal- to inverse-spinel structure has been observed for $Fe_xCo_{3-x}O_4$ thin films as the Fe composition (x) increases from 0 to 2. The samples were fabricated as thin films by sol-gel method on Si(100) substrates. X-ray diffraction measurements revealed a coexistence of two phases, normal and inverse spinel, for $0.76{\le}x{\le}0.93$. The normal-spinel phase is dominant for $x{\le}0.55$ while the inverse-spinel phase for $x{\ge}l.22$. The cubic lattice constant of the inverse-spinel phase is larger than that of the normal-spinel phase. For both phases the lattice constant increases with increasing x. X-ray photoelectron spectroscopy measurements revealed that both $Fe^{2+}$ and $Fe^{3+}$ ions exist with similar strength in the x=0.93 sample. Conversion electron $M\ddot{o}ssbauer$ spectra measured on the same sample showed that $Fe^{2+}$ ions prefer the octahedral $Co^{3+}$ sites, indicating the formation of the inverse-spinel phase. Analysis on the measured optical absorption spectra for the samples by spectroscopic ellipsometry indicates the dominance of the normal spinel phase for low x in which $Fe^{3+}$ ions tend to substitute the octahedral sites.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.268-268
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• 2009

Li-Mn spinel의 고온수영 특성을 향상을 위해 졸-겔법으로 $V_2O_5$를 Li-Mn spinel 표면에 코팅을 하였다. $V_2O_5$의 코팅양은 1, 3, 5wt%로 조절하여 코팅 양에 따른 특성변화를 조사하였다. XRD분석결과 $V_2O_5$가 코팅된 Li-Mn spinel을 $400^{\circ}C$에서 열처리시 $Mn(VO_3)_2$가 생성되는 것을 확인하였다. 충방전 테스트결과, 고온에서 $V_2O_5$를 코팅한 Li-Mn spinel이 우수한 수명을 나타냈다. 하지만 코팅량이 1wt%까지는 용량의 변화가 거의 없었고, 5wt% 코팅시 현격히 용량이 감소하였다.

• 한국세라믹학회지
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• 제15권2호
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• pp.66-71
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• 1978

The cobalt blue spinel stains (main composition; CoO:$Al_2O_3$=1 : 1) in CoO-NiO-$Al_2O_$3 and $CoO-Al_2O_3-Cr_2O_3$ system were prepared by the calcination of each component oxides to be adequate for the factory. The color development, the change of the lattice constnat of the spinel and its application to colored glazes were studied. The results were summarized as follows. 1) In CoO-Al_2O_3$ spinel, the excess addition of each component hardly made any variation in lattice constantand alumina-rich spinel specimens caused the brilliant blue color fade. 2) An increase of $Ni^{2+}$ in $CoO-NiO-Al_2O_3$ system, made the lattice constnat of the $CoO-Al_2O_3$ spinel smaller, and an increase of $Cr^{3+}$ in $CoO-Al_2O_3-Cr_2O_3$, larger. 3) Glazed stains under lead glaze were colored nearly same dark blue color fade.

• 한국세라믹학회지
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• 제26권5호
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• pp.593-600
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• 1989

Fine spinel powder was prepared from the Mg-Al double alkoxide synthesized using magnesium powder, aluminum foil and sec-butyl alcohol. This powder was compared with powder prepared by mixing two commercial alkoxides. The spinelization was started at 50$0^{\circ}C$ and was almost completed at 100$0^{\circ}C$ with a good crystallinity in the double alkoxide system. In mixed alkoxide system, homogeneous spinel powder was not obtained and MgO existed as a second phase because of solubility and hydrolysis rate differences of two alkoxides. The relative density of specimen prepared by double alkoxide was 99% and specimen prepared by mixed alkoxide was 95%. The modulus of rupture of specimens prepared by double alkoxide and mixed alkoxide was 49.9kg/$\textrm{mm}^2$ and 41.6kg/$\textrm{mm}^2$, respectively.

• 한국세라믹학회지
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• 제33권2호
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• pp.235-241
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• 1996

Self-Propagating high temperature synthesis(SHS) technique was used to synthesize the spinel phase of MgAl2O from MgO and Al powder. Processing factors such as mixing time preheating temperature and ignition catalyst were varied to determine the optimum condition to form MgAl2O4 phase. The reaction products were heat treated at the temperature range of 120$0^{\circ}C$ and 150$0^{\circ}C$. to observe phase transformation of unreacted materials. Processing factors such as 48 hrs-mixing 80$0^{\circ}C$-preheating and 20wt% KNO3-ignition catalyst were effective of the formation of MgAl2O spinel. An activation energy 49.7kcal/mol. was calculated to form a MaAl2O4 spinel from unreacted materials.