• 한국세라믹학회지
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• 제33권7호
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• pp.832-838
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• 1996

Thermite reaction products of MgO and Al were added to MgO-C refractory to improve the properties of corrosion against the attack of slag, oxidation and mechanical spalling. Corrosion rate of MgO-C-MgAl2O4 spinel refractory at the ratio of 3.3(CaO/SiO2) slag was smaller than that of MgO-C and MgO-C-Al refractory. The excellent corrosion resistance of the MgO-C-MgAl2O4 spinel refractory against the slag attack was appeared by Al and MgAl2O4 spinel with high melting point and corrosion resistance and the high thermal conductivity and low thermal expansion of AIN. Hot M.O.R at 140$0^{\circ}C$ and the resistance of oxidation weight loss at 90$0^{\circ}C$ were 210kg/cm2 and -12% respectively.

• 한국세라믹학회지
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• 제44권1호
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• pp.65-69
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• 2007

For self-developed alkali-alkaline earth-silicate and commercial glass melts for plasma display panel substrate, the corrosion behavior of fused casting refractory consisting of $Al_2O_3-ZrO_2-SiO_2$ was examined at the temperature corresponding to $10^2\;dPa{\cdot}s$ of melt viscosity by static finger methode. The corroded refractory specimens showed a typical concave shape due to interfacial convection of melts at their flux line. However, the corrosion thickness by commercial glass melts was $6\sim10$ times comparing to that by the self?developed melts. From the view point of the glass composition and the role of alkaline earth in glass network, it was discussed the effect of alkali/alkaline earth diffusion and temperature on the refractory corrosion.

• 한국재료학회지
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• 제24권1호
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• pp.53-59
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• 2014

The corrosion resistance of submerged entry nozzle (SEN) materials were investigated for high-class steel manufacturing. Composite samples were fabricated by mixing $ZrO_2$, $Al_2O_3$, MgO, mullite, spinel, and carbon. The raw materials were mixed with attrition milling, compacted in a uniaxial pressure of 200MPa and calcined at $1000^{\circ}C$ for 3 h in $N_2$ atmosphere. The bulk density and apparent porosity of the calcined samples were measured by the liquid displacement method in water using Archimedes's principle. The corrosion resistance of the samples were measured by cup test with mold powder at $1550^{\circ}C$ for 2 h. The microstructure and elemental analysis of samples were observed by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), and X-ray diffraction pattern (XRD). The XRD result shows that the starting raw materials were crystalline phase. The microstructure of fabricated specimen was investigated before and after corrosion tests at $1000^{\circ}C$ and $1550^{\circ}C$ for 2h. $ZrO_2$-C composite showed good resistance in the slag corrosion test. Among the composite oxide materials, $ZrO_2-Al_2O_3$-C and $ZrO_2$-MgO-C showed better resistance than $ZrO_2$-C in the slag corrosion test. The diameter variation index of $ZrO_2$-C refractory was 16.1 at $1000^{\circ}C$ for 2 h. The diameter variation index of the $ZrO_2-Al_2O_3$-C refractory was larger than that of the $ZrO_2$-C refractory at $1550^{\circ}C$ for 2 h.

• Nuclear Engineering and Technology
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• 제54권6호
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• pp.1954-1961
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• 2022

Lead-based fast reactor (LFR) has become one of the most promising reactors for Generation IV nuclear systems. A developing trend of LFR is high efficiency, along with operation temperatures up to 800 ℃ or even higher. One of key issues in the high-efficiency LFR is corrosion of cladding materials with lead at high temperatures. In this study, corrosion behavior of some refractory metals (Nb, Nb521, and Mo-0.5La) was investigated in static lead at 1000 ℃ for 1000 h. The results showed that Nb and Nb521 exhibited an intense dissolution corrosion with obvious lead penetration after corrosion, and lead penetration extended along the grain boundaries of the specimens. Furthermore, Nb521 showed a better corrosion resistance than that of Nb as a result of the elements of W and Mo included in Nb521. Mo-0.5La showed much better corrosion resistance than that of Nb and Nb521, and no lead penetration could be observed. However, an etched morphology appeared on the surface of Mo-0.5La, indicating the occurrence of corrosion to a certain degree. The results indicate that Mo-0.5La is compatible with lead up to 1000 ℃. While Nb and Nb alloys might be not compatible with lead for high-efficiency LFR at such high temperatures.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.441-444
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• 2007

The inside wall of a coal gasifier is lined with refractory, and the corrosion of the refractory by coal sag is an important parameter affecting the refractory lifetime and the replacement period. This paper examines the changes in microstructure of a chromia refractory due to chemical reactions with penetrating slag as a function of slag composition. The effects of CaO and $Fe_2O_3$ concentrations were studied using Datong and KIDECO slag. Static corrosion experiments were carried out, the percent slag penetration and changes in the microstructure were determined by SEM/EDX analyses. FactSage equilibrium calculations were carried out to determine the equilibrium products and the predictions were compared with experimental observations.

• 세라미스트
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• 제9권6호
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• pp.12-17
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• 2006

One of characteristic of $Cr_2O_3-containing$ refractory is excellent resistance to corrosion. However, there is a problem that hexa-valent chromium, which is noxious to the human body, is easily formed by reaction between the refractory and slag with CaO, $Na_2O$ and/or $K_2O$. In this article, the reason why the $Cr_2O_3-containing$ refractory has excellent corrosion resistance qualities, he conditions under which hexa-valent chromium formed, methods for suppressing generation of hexa-valent chromium and the possibility of the refractory components excluding $Cr_2O_3$ for the furnace are described as a base of development of further excellent refractories.

• The Korean Journal of Ceramics
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• 제1권1호
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• pp.29-34
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• 1995

Theoretical predictions were made for thermodynamically stable phases which formed when alkali(sodium and Potassium) vapors reacted with the 90% $Al_2O_3$-10% $Cr_2O_3$ refractory under coal gasifying atmosphere using the computer program of SOLGASMIX-PV. The calculation results showed that the stable compounds that formed were $X_2O$.$Al_2O_3$ and $X_2O$.$llAl_2O_3$(X=$Na^+$ or $K^+$), depending upon the alkali concentration. The presence of sulfur in gasifying atmospheres did not appear to affect the species of alkali reaction products. Alkali attack at high temperatures is likely to cause serious degradation at the hot face of the refractory, indicating that the alkali concentration is an important factor to affect the degradation of the refroctory.

• The Korean Journal of Ceramics
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• 제1권2호
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• pp.86-90
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• 1995

Theoretical predictions for thermodynamically stable phases which formed when alkali(sodium and potassium) vapors reacted with alumina-chromia refractories under coal gasifying atmosphere were confirmed experimentally using a laboratory-scale coal gasifying reaction system and a commercial alumina-chromia refractory using SEM, XRD, and EDAX. Alkali concentration profiles in the refractory as a function of time were also determined. The results showed that the compounds that formed were $X_2O{\cdot}Al_2O_3, X_2O{\cdot}Cr_2O_3, X_2O{\cdot}5Al_2O_3, X_2O{\cdot}7Al_2O_3, X_2O{\cdot}11Al_2O_3(X=Na^+ \;or\; K^+)$, depending upon the alkali concentration and time of exposure at high temperatures. The presence of sulfur in gasifying atmospheres did not appear to affect the alkali reaction produces. Alkali pentration into the alumina-chromia refractory was deep and the formation of the $Na_2O{\cdot}Al_2O_3/K_2O{\cdot}Al_2O_3$ compunds resulted in the serious deformation of the refractory due to the large volume expansion at the reaction surface. The hot face of the alumina-chromia refractory in service under an alkali environment is prone to failure by alkali attack.

• 에너지공학
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• 제13권4호
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• pp.281-290
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• 2004

석탄 가스화기에서 1000시간 이상 사용된 Cr$_2$O$_3$-Al$_2$O$_3$-ZrO$_2$ 내화물의 결정구조, 화학성분, 미세구조를 분석하여 석탄 슬래그에 의한 화학적 침식 메카니즘을 규명하였다 크로미아 내화물의 침식은 슬래그의 FeO와 $Al_2$O$_3$이 Cr$_2$O$_3$과 반응하며 일어나는 것으로 추정된다. 1차적으로 내화물의 슬래그 접촉면에서 슬래그의 FeO와 Cr$_2$O$_3$가 반응하여 FeCr$_2$O$_4$를 형성한다. 슬래그의 FeO가 모두 소모된 후 슬래그의 $Al_2$O$_3$이 Cr$_2$O$_3$ 입자와 반응하여 (Al, Cr)$_2$O$_3$를 형성하고, (Al, Cr)$_2$O$_3$상은 가장자리로부터 깨어져 미세한 입자를 형성한다. Cr$_2$O$_3$의 침식정도는 입자 크기와 치밀도에 따라 달라지며, 입자가 클수록, 치밀도가 높을수록 내침성이 증가하였다. ZrO$_2$는 화학적 성분의 변화 없었으나 슬래그 접촉면 부근에서 상 경계의 굴곡이 심해지거나 입자가 절단되는 물리적 침식의 영향을 받는다. 슬래그의 침투도는 일반적으로 석탄 주입구에서 아래로 내려갈수록 증가하나 슬래그 tap에서는 감소하였다.

• 한국세라믹학회지
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• 제35권2호
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• pp.129-136
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• 1998

The effects of MgO on the resistance to corrosion and oxidation of Al2O3-SiC-C refractory have been in-vestigated. The resistance to oxidation was improved as the amount of MgO increased. The resistance to corrosion was enhanced until 2 wt% MgO content but degraded over that content. From the dependence of temperatuer on the oxidation resistance oxidation was suppressed by the microstructural densification caused by spinel formation over 1200~130$0^{\circ}C$and the formation MgO-Al2O3-SiO2 liguid-phase over 130$0^{\circ}C$ The weight loss of specimens containing MgO with various purity at range of 95 to 99% and par-ticle size of -0.045 mm to -0.074 mm was examined. The oxidation resistance was not changed signficantly with the particle size and purity of MgO powders.