• Title/Summary/Keyword: mullite

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Mullitization of Al-Kaolin Mixture (Al-Kaolin 혼합물의 Mullite화 반응)

  • 박정현;조정식;배원태
    • Journal of the Korean Ceramic Society
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    • v.20 no.2
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    • pp.123-128
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    • 1983

  • This research is aimed to synthesize the mullite by adding Al powder of $Al_2O_3$ to kaolin. Specimens fired at 1400, 1450 and 150$0^{\circ}C$ were compared in their X-ray diffraction patterns quantitative analysis of mullite formed and fine microstructures with those containing reactive $Al_2O_3$ activated $Al_2O_3$ as alumina source The experiment of Al oxdiation was also performed by measuring the weight increase of specimens. Two different shapes of mullites acicular and chunky were observed by SEM and the yield of mullites were in-creased by the order of adding activated $Al_2O_3$ reactive $Al_2O_3$ and Al powder to kaolin.

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The Study on Material Characteristics of the By-Products of the Production of Bronze during the Goryeo Dynasty Excavated from the Sinpung Site, Wanju, Jeollabuk-do, South Korea (완주 신풍유적 출토 고려시대 청동생산 부산물의 재료학적 특성)

  • Choi, Nam Young;Cho, Nam Chul;Kang, Beoung Sun
    • Journal of Conservation Science
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    • v.35 no.5
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    • pp.392-402
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    • 2019

  • This study interpreted the characteristics of the site and provenance of raw material by performing material characteristics analysis of the slags and tuyeres excavated from the Sinpung site in Wanju, Jeollabuk-do. The major chemical compositions suggested that the slags and tuyeres were created when Cu-Sn-Pb was alloyed. Metal microscope and scanning electron microscopy-energy dispersive spectrometer analyses revealed that the slags and tuyeres were by-products formed in the alloying process. This alloy, created by adding galena to copper and tin ingots, was an intermediary material used in making the finished products. According to the lead isotope ratio analysis result, slags could be made using galena of the southern Zone III region of Korea. Based on the decomposition of mica group minerals and the formation of mullite detected through X-ray diffraction analysis, it is possible to conclude that the tuyeres operated at approximately 1,000℃ as, the mullite was detected on the outside of the tuyeres.

  • https://doi.org/10.12654/JCS.2019.35.5.02 인용 PDF KSCI

Cracks in Tape Cast Oxide Laminar Composites (테이프 캐스팅 산화물 층상 복합체에서의 균열)

  • Kim, Ji-Hyun;Yang, Tae-Young;Lee, Yoon-Bok;Yoon, Seog-Young;Park, Hong-Chae
    • Journal of the Korean Ceramic Society
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    • v.39 no.5
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    • pp.484-489
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    • 2002

  • Hot-pressure sintered laminar composites with alumina/zirconia or mullite/zirconia as an outer layer and alumina/zircon (resulting in reaction-bonded mullite/zirconia during sintering) as an inner layer were fabricated by tape casting and lamination. Various forms of crack were observed in sintered laminar composites, these cracks included channel cracks in the outer layer, transverse cracks in the inner layer and interface cracks debonding interlayer. Based on detailed microscopic observations, the cracks were attributed to thermal expansion mismatch between the oxides consisting of the each layer. In particular, the interlayer and transverse cracks were confirmed in the laminates consisted of the mullite/zirconia system as the outer layers, however, those cracks were not observed in the alumina/zirconia system used. In addition, the crack propagation did not exhibit same behavior in the two kinds of outer layer when the indentation load was applied.

  • https://doi.org/10.4191/KCERS.2002.39.5.484 인용 PDF KSCI

Mineralogical Characterization and Thermal Behaviours of Kaolins from the Southern Parts of Korea (한반도 남부지역에서 산출되는 카올린광물의 고온영역에서의 광물학적 특성 연구)

  • Lee, Su-Jeong;Moon, Hi-Soo
    • Economic and Environmental Geology
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    • v.29 no.3
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    • pp.269-279
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    • 1996

  • Dehydroxylation and mullitization of primary and secondary kaolins were investigated in order to compare and understand the differences in thermal behaviours by DTA and TG up to $1,100^{\circ}C$. Chemical analyses and EPMA of the samples revealed nearly ideal unit-cell formulae of kaolins. The weight losses of dickite and halloysite are 14% and 12.5% on the average, respectively. The activation energies of dehydroxylation of kaolin minerals were calculated according to Kissinger's approach which uses various heating rates in DTA to estimate the activation energy of thermal reactions. The activation energies of dehydroxylation of halloysites from Daemoung and Buksam mines are about $163kJmor^{-1}$ (white), $168kJmor^{-1}$ (pink), and $176kJmor^{-1}$ respectively. The activation energies of dickites collected from Sungsan and Ogmae mines are about $166kJmor^{-1}$ and $387kJmor^{-1}$. The asymmetric shape of endothermic peak in DTA, the relative intensities of OH-stretching bands in FTIR spectroscopy and the existence of residual XRD peaks of the samples which were heated at $550^{\circ}C$ for 2 hours indicate that Sungsan dickite may be more disordered than Ogmae dickite. The new phase formed in thermally treated samples in the range of $900^{\circ}C$ to $1,100^{\circ}C$ was identified as mullite by XRD on the basis of disappearing of the characteristic peaks of kaolins and increasing of amorphous background upon heat treatment. On further heating, loss of more water from dehydroxylate resulted in the formation of mullite and the characteristic X-ray diffraction patterns of mullite began to appear at about $900{\sim}1,000^{\circ}C$ in kaolins.

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