• 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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• 제26권2호
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• pp.187-194
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• 1989

Synthesis of spinel pigment on ZnO-Fe2O3 system. The object of this research is the synthesis of new spinel pigments on the basic of ZnO-Fe2O3 system which was substituted by ZnO-Fe2O3 by MgO-Al2O3. This research was progressed by measuring the X-ray diffraction and the reflectances of the substitued ZnO-Fe2O3 group. Which was obtained by sintering at the temperature of 1,00$0^{\circ}C$, 1,10$0^{\circ}C$, 1,20$0^{\circ}C$ and 1,25$0^{\circ}C$ and them by regrinding. In order to coloring test, here basic compositions of Barium glaze, Zinc glaze, Lime glaze, Lead glaze and Talc glaze used in this experiment are obtained from the ceramic work. Adding synthetic stains in these basic glazes with 3%, mixing and glazing on the specimen. The specimens was fired at 1,28$0^{\circ}C$ in reducing and oxidizing atmosphere in the gas kiln. The results of the research as follow. 1. Many kinds of spinel pigment was produced on ZnO-Fe2O3 system that is to say, not always only spinel. 2. Spinel peak was observed strongly on the ZnO-Fe2O3 system withsubstituting by MgO-Fe2O3 and MgO-Al2O3 group(the ratio of MgO, Al2O3 being increased, observed more strongly). 3. The most effective temperature ranges was 1,20$0^{\circ}C$~1,25$0^{\circ}C$. 4. The color of spinel pigments on this system was observed by "stable YR". 5. It was yellow red in oxidizing and green in reducing atmosphere on the coloring test.ring test.

• 청정기술
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• 제20권4호
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• pp.375-382
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• 2014

금속산화물이 담지된 허니컴 형상의 플라즈마-촉매 반응기를 이용하여 아이소프로필 알코올(isopropyl alcohol, IPA) 저감 및 부산물 생성 거동에 대해 조사하였다. 허니컴 형상의 다공질 세라믹 지지체(주성분: ${\alpha}-Al_2O_3$)에 금속산화물로 산화철($Fe_2O_3$) 또는 산화구리(CuO)를 담지시킨 후, 이 촉매가 동축 원통형 전극구조 내부에 위치하도록 플라즈마-촉매 반응기를 구성하였다. 플라즈마 반응에 의한 IPA 분해속도가 매우 빨랐기 때문에 IPA 분해효율 자체는 금속산화물 담지 여부 및 금속산화물 종류에 관계없이 유사한 것으로 나타났으나, 부산물 생성거동은 촉매종류에 따라 큰 차이를 보여주었다. 아세톤, 폼알데하이드, 아세트알데하이드, 메테인, 일산화탄소 등의 유해 부산물 농도는 $Fe_2O_3/{\alpha}-Al_2O_3$ < $CuO/{\alpha}-Al_2O_3$ < ${\alpha}-Al_2O_3$ 순으로 높게 나타났다. 유량 $1L\;min^{-1}$, IPA 초기농도 5,000 ppm(산소: 10%), 방전전력 47 W의 조건에서 얻어진 $CO_2$ 선택도는 ${\alpha}-Al_2O_3$, $CuO/{\alpha}-Al_2O_3$, $Fe_2O_3/{\alpha}-Al_2O_3$에 대해 각각 40, 80, 95%로서 $Fe_2O_3/{\alpha}-Al_2O_3$가 플라즈마-촉매를 이용한 IPA의 산화에 가장 효과적인 것으로 나타났다. 플라즈마를 단독으로 사용하여 휘발성유기화합물을 분해할 경우 타르형태의 생성물이 반응기에 퇴적되는 문제점이 있으나, 플라즈마-촉매 공정에서는 이러한 현상이 관찰되지 않았으며 촉매의 활성이 그대로 유지되었다.

• 한국세라믹학회지
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• 제26권5호
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• pp.705-711
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• 1989

The glass-ceramics was prepared with the scoria(CaO-MgO-Al2O3-SiO2 system) of the locally occurring volcanic ejecta containing 10-13w/o of (FeO＋Fe2O3) by melting at 140$0^{\circ}C$ for 4 hours and thermally treated for nucleation and crystallization. The sucrose was added to the scoria to adjust the Fe2+/Fe3+ ratio during the melting process. The addition of 1-2w/o of sucrose showed the glass-ceramics body with the finest particle developed and dispersed over the entire range. It is concluded that the impurity content of iron oxide and titanium oxide play the most-influencial effect on the crystallization. When 1-2w/o of sucrose was added to the scoria, the value of Fe2+/Fe3+ ratio was 0.93-1.32 and showed the best result of crystallization. The nucleation temperature and time were calculated by the measurements of exothermic peak temperatures of DTA for quenched and thermally treated glasses. The nucleation temperature of scoria glass without the addition of sucrose was estimated as 75$0^{\circ}C$, but the addition of sucrose by 2w/o showed the nucleation temperature 6$25^{\circ}C$. The nucleation time was calculated with the same DTA curves. The nucleation times estimated were about 150min. for both of glasses without and with sucrose added. Finally, the activation energies for crystallization were calculated with the DTA data. The calculated activation energies were 143 Kcal/mole for the glass without addition of sucrose and 90Kcal/mole, 87Kcal/mole, 85Kcal/mole and 71Kcal/mole for the glasses of 1w/o, 2w/o, 3w/o and 4w/o addition respectively.

• 한국재료학회지
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• 제1권4호
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• pp.198-205
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• 1991

$Fe_2O_3,\;Al_2O_3,\;TiO_2$ 및 Si분말을 사용하여 고상반응법으로 써어미스터 소결체를 합성하였다. 합성된 소결체의 조식특성을 SEM으로 조사하고, 액체항온조에서 $-50~+50^{\circ}C$ 온도영역에서의 측정 결과 $\beta$상수가 972~4005K의 값을 갖는 써어미스터 소결체를 얻었다. 이 소결체는 고공기온측정을 위한 라디오존데용 온도센서로 사용될 수 있다.

• 대한금속재료학회지
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• 제49권3호
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• pp.231-236
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• 2011

Nanopowder of $Fe_2O_3$, Al, Cr and Si was fabricated by high energy ball milling. A dense nanostuctured $A_2O_3$ and $6.06Fe_{0.33}Cr_{0.16}Al_{0.23}Si_{0.29}$ composite was simultaneously synthesized and consolidated using high frequency induction heated sintering method within 1 minute from mechanically activated powders of $Fe_2O_3$, Al, Cr and Si. The grain sizes of $Al_2O_3$ and $Fe_{0.33}Cr_{0.16}Al_{0.23}Si_{0.29}$ in composite are 80 and 18 nm, respectively.

• 암석학회지
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• 제2권2호
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• pp.63-73
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• 1993

The assemblage epidote and grandite garnet occurs in low-to medium-grade metabasites and calc schists of various geotectonic settings and in hydrothermally altered calcareous rocks in skarn deposits. The compositions of sixteen epidote-garnet paris have been analysed by means of electron microprobe. Al-Fe partitioning between coexisting grandite garnet and epidote is considered and measured at the grain boundaries on the supposition that the surface equilibrium was maintained in the following exchange reaction: 2$Ca_2Al_3Si_3O_12$(OH)+$Ca_3Fe_2Si_3O_12$=2$Ca_2A_l2FeSi_3O_12$(OH)+$Ca_3Al_2Si_3O_12$ Partition coefficients confirms the differences in thermal conditions between low-grade and medium-grade metamorphic rocks. $K_D$ values ($X_{$CO_2$}$=($Fe^{+3}$/Al)$^{Ep}$/($Fe^{+3}$/Al)$^{Gr}$, where Fe=$Fe^{+3}$) from greenschist facies rocks of the estimated metamorphic temperatures, 330~$390^{\circ}C$, range approximately between 0.02 and 0.17. Epidote-amphibolite facies rocks and calcareous skarns of the estimated temperatures, 400~$550^{\circ}C$, have $K_D$ values between 0.24 and 0.37. $K_D$ values from the rocks of the temperatures, 640~$700^{\circ}C$, range nearly between 0.58 and 0.75. The diagrams in Figs. 2 and 3 can serve as a mineralogic thermometer for relatively shallow rocks, assuming that the pressure dependence of partition coefficients for the iron-exchange reaction in the two minerals can be neglected.

• 한국재료학회지
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• 제21권8호
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• pp.439-443
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• 2011

The crystal structure and magnetic properties of a new solid solution type ferrite $(Fe_2O_3)_5-(Al_2O_3)_{3.4}-(Ga_2O_3)_{0.6}-SiO$ were investigated using X-ray diffraction and M$\"{o}$ssbauer spectroscopy. The results of the X-ray diffraction pattern indicated that the crystal structure of the sample appears to be a cubic spinel type structure. The lattice constant (a = 8.317 ${\AA}$) decreases slightly with the substitution of $Ga_2O_3$ even though the ionic radii of the Ga ions are larger than that of the Al ions. The results can be attributed to a higher degree of covalency in the Ga-O bonds than in the Al-O and Fe-O bonds, which can also be explained using the observed M$\"{o}$ssbauer parameters, which are the magnetic hyperfine field, isomer shift, and quadrupole splitting. The drastic change in the magnetic structure according to the Ga ion substitution in the $ (Fe_2O_3)_5(Al_2O_3)_{4-x}(Ga_2O_3)_xSiO$ system and the low temperature variation have been studied through a M$\"{o}$ssbauer spectroscopy. The M$\"{o}$ssbauer spectrum at room temperature shows the superpositions of two Zeeman patterns and a strong doublet. It shows significant departures from the prototypical ferrite and is comparable with the diluted ferrite. The doublet of spectrum at room temperature appears to originate from superparamagnetic clusters and also the asymmetry of the doublet appears to be caused by the preferred orientation of the crystallites. The M$\"{o}$ssbauer spectra below room temperature show various complicated patterns, which can be explained by the freezing of the superparamagnetic clusters. On cooling, the magnetic states of the sample were various and multi critical.

• 한국표면공학회지
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• 제45권2호
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• pp.61-69
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• 2012

Alloys of Fe-(5, 10, 15)Al and Fe-(10, 20, 30, 40)Cr were corroded at 700 and $800^{\circ}C$ for 70 hr in either atmospheric air or 1 atm of Ar+$1%SO_2$ gases. In these atmospheres, Fe-5Al and Fe-10Cr alloys displayed poor corrosion resistance. In atmospheric air, Fe-5Al alloys formed oxide nodules, while Fe-10Cr alloys formed thick scales and internal oxides. In Ar+$1%SO_2$ gases, Fe-5Al and Fe-10Cr alloys formed thick, nonadherent bi-layered scales, which grew primarily by the outward diffusion of Fe ions and inward diffusion of oxygen and sulfur ions. By contrast, in atmospheric air and Ar+$1%SO_2$ gases, Fe-(10, 15)Al and Fe-(20, 30, 40)Cr alloys displayed good corrosion resistance by forming $Al_2O_3$ and $Cr_2O_3$ layers on the surface, respectively.

• 한국세라믹학회지
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• 제39권2호
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• pp.199-203
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• 2002

소결 분위기가 금속입자분산 세라믹스기 복합체의 미세 조직 및 물성에 미치는 영향에 대하여 조사하고자 화학적 방법으로 합성한 $Al_2O_3$/Fe-Ni 나노복합분말을 수소 및 아르곤 가스 분위기, 또한 소결온도 등으로 제어하여 열간가압 소결하였다. 수소분위기에서 소결한 복합체는 아르곤분위기의 경우보다 반응상 $FeAl_2O_4$의 형성이 억제되었으며, 증가된 파괴강도 및 인성 값을 나타내었다. 또한, 소결 온도를 낮추었을 경우 기지상 및 금속 분산상의 미세화와 향상된 기계적 성질을 얻을 수 있었다. 소결 조건에 따른 기계적 특성의 변화는 주로 반응상의 형성과 관련된 미세조직 특성에 의존하는 것으로 해석하였다.