• 한국세라믹학회지
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• 제24권4호
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• pp.376-384
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• 1987

Kaolin was treated by HF and fired at high temperature in order to reduce silica and impurity minerals of kaolin, and eventually to increase the yield of mullite. The kaolin structure was destroyed by HF-treatment and transformed into mullite at lower temperature than those of non-treated kaolin. Not only the silica content of kaolin was reduced, but also the crystalline structure of it was destroyed by HF-treatment.

• 산업기술연구
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• 제5권
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• pp.15-20
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• 1985

The microstructure of sintered body of two component(kaolin-pottery stone) system after firing was examined with scanning electron microscope. At first the pottery stone was melted into glassy phase and the kaoline was decomposed to mullite and silica at higher temperature. The interlocked mullite crystals and silica surrounded by glassy phase are belived to increase strength.

• 한국세라믹학회지
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• 제38권2호
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• pp.199-206
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• 2001

납석-뮬라이트의 상변이 과정을 주로 에너지여과 투과전자현미경을 이용하여 연구하였다. 납석은 (OH)를 읽고 pyrophyllite dehydroxylate로 된 후 뮬라이트와 크리스토발라이트로 상변이한다. Pyrophyllite dehydroxylate의 장주기 질서는 105$0^{\circ}C$에서도 유지된다. 생성 초기단계에서 뮬라이트는 pyrophyllite dehydroxylate에 대해 topotaxy를 보이며, elongation direction이 c*인 침상 결정으로 자라기 때문에 textured ED pattern을 나타낸다. Pyrophyllite dehydroxylate는 120$0^{\circ}C$에서 완전히 분해되어 뮬라이트의 결정 성장과 비정질 실리카로부터 크리스토발라이트의 생성이 이루어진다.

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

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2000년도 추계총회,초청강연,특별강연,연구발표회
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• pp.36.2-36
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• 2000

• 자원리싸이클링
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• 제10권6호
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• pp.29-34
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• 2001

석탄회 분말을 다중자연낙하법에 의한 공기분급에 의하여 미립 및 조립의 분말로 정제 및 분급한 후 각각의 분말을 사용하여 뮬라이트 및 제올라이트를 합성하였다 평균 입경이 $6.5mu$m인 미립 석탄회에$ A12$ $O_3$를 첨가한 후 145$0^{\circ}C$ 이상의 온도에서 소성하여 뮬라이트 상의 소결체를 얻었다. 평균 입경 $56.3\mu$m인 조립 석탄회를 사용하여 3.5 M NaOH수용액과 $120^{\circ}C$에서 수열 반응시켜 phillipsite형 제올라이트를 합성하였다. 이와 같은 방법으로 모든 입도의 석탄회 분말을 무기재료의 합성에 이용할 수 있었다.

• 자원리싸이클링
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• 제29권6호
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• pp.73-78
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• 2020

선탄 폐석의 유리 소재 원료로의 활용을 위해 선탄 폐석의 고온 상 전위 거동 및 Na2CO3의 첨가에 따른 유리질(비정질)화 실험을 실시하였다. 실험 결과 700~1,100 ℃에서 소성된 선탄폐석에는 mullite가 생성되고, 1,450 ℃에서는 mullite와 cristobalite만이 존재하였다. 선탄 폐석의 유리질화는 Na2CO3 첨가됨에 따라 진행되었으며, Na2CO3 10 wt.% 첨가 후 1,450 ℃ 온도에서 소성된 선탄 폐석의 유리질화는 97.9 wt.%로 나타났다. 그러나 Na2CO3가 20 wt.% 첨가된 선탄 폐석의 시료의 경우, 1,100 ℃에서의 2차 재소성 과정에서 nepheline(Na2O·Al2O3·2SiO2)이 생성되었으며, 이를 통해 선탄폐석의 유리질화를 위한 최적의 Na2CO3 첨가량은 10 wt.%로 나타났다.

• 한국세라믹학회지
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• 제51권5호
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• pp.481-486
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• 2014

Environmental barrier coatings (EBCs) are used to protect SiC-based ceramics or composites from oxidation and corrosion due to reaction with oxygen and water vapour at high temperatures above $1000^{\circ}C$. Mullite ceramics have been studied for environmental barrier coatings for Si-based ceramics. More recently, rare earth silicate ceramics have been identified as more water vapour-resistant materials than mullite for environmental barrier coatings. In this study, we fabricate mullite and yttrium silicate ceramics by an atmospheric plasma spray coating method using spherical granules fabricated by spray drying. As a result, EBCs with thicknesses in the range of $200-300{\mu}m$ are successfully fabricated without any macroscopic cracks or interfacial delamination. Phase and microstructure analysis are conducted, and the basic mechanical properties, such as hardness and indentation load-displacement curves are evaluated.

• 방사성폐기물학회지
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• 제18권2호
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• pp.143-155
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• 2020

A reference electrode is important for controlling electrochemical reactions. Evaluating properties such as the reduction potential of the elements is necessary to optimize the electrochemical processes in pyroprocessing, especially in a multicomponent environment. In molten chloride systems, which are widely used in pyroprocessing, a reference electrode is made by enclosing the silver wire and molten salt solution containing silver chloride into the membranes. However, owing to the high temperature of the molten salt, the choice of the membrane for the reference electrode is limited. In this study, three types of electroceramic, mullite, Pyrex, and quartz, were compared as reference electrode membranes. They are widely used in molten salt electrochemical processes. The potential measurements between the two reference electrode systems showed that the mullite membrane has potential deviations of approximately 50 mV or less at temperatures higher than 650℃, Pyrex at temperatures lower than 500℃, and quartz at temperatures higher than 800℃. Cyclic voltammograms with different membranes showed a significant potential shift when different membranes were utilized. This research demonstrated the uncertainties of potential measurement by a single membrane and the potential shift that occurs because of the use of different membranes.

• 한국세라믹학회지
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• 제42권8호
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• pp.532-536
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• 2005

Thermal shock resistance of structural ceramics is a property that is difficult to quantity, and as such is usually expressed in terms of a number of empirical resistance parameters. These are dependant on the conditions imposed, but one method that can be used is the examination of density, Young's modulus and thermal expansion retention after quenching. For high temperature applications, long-annealing thermal durability, cycle thermal stability and residual mechanical properties are very important if these materials are to be used between $1000^{\circ}C$ and $1300^{\circ}C$. In this study, an excellent thermal shock-resistant material based on $Al_2TiO_5-mullite$ composites of various compositions was fabricated by sintering reaction from the individual oxides and adjusting the composition of $Al_2O_3TiO_2/SiO_2$ ratios. The characterization of the damage induced by thermal shock was done by measuring the evolution of the Young's modulus using ultrasonic analysis, density and thermal expansion coefficients.