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RISS 인기검색어
- 검색키워드
- 저자 : Suhanda Sutardi (검색결과 4 건)
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Preparation of nano mullite from activated kaolin and gibbsite at a low temperature
Suhanda Sutardi 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.3
Nanomullite powders were successfully prepared from activated kaolin and gibbsite. Kaolin activation was performed by the thermal treatment at 800 o C and sulfuric acid treatment. The activation process has changed kaolin structure to produce alumina, silica, and aluminosilicate phases, as given by XRD result. The XRD result was corroborated and was proved by the result of electron diffraction TEM analysis, the activated kaolin consisted of a-Al2O3, quartz, and mullite phases. Nanomullite was prepared from the activated kaolin, gibbsit, and sulfuric acid and was calcined at 400 o , 600 o , 800 o , and 1200 o C. Crystallization of the as-prepared mullite in the temperature range of 400 o -1200 o C produced mullite, α-Al2O3, and spinel phases at 400 o C. A further phase transformation of the mullite sample maintained mullite and α-Al2O3 phases at 1200 o C. The grain sizes of mullitepowders are found to be less than 100 nm at a calcination temperature of 1200 o C. The electron diffraction (ED) patterns of the calcined mullite are indexed to the mullite phase with the crystal plane orientations of (310), (030), (101), (001), (201), (040) and (121). These results are in agreement with the XRD result for the calcined mullite at 1200 o C.
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Rifki Septawendar,Bambang Sunendar Purwasasmita,Suhanda Sutardi,Naili Sofyaningsih,Wahyudi Kristanto 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.3
Zirconia nanopowder was successfully prepared using sugar and citric acid by a precursor calcination process, in which sugar was used as a gelling agent and citric acid as a catalyst. The effect of citric acid on this zirconia preparation is found out by the variable time of addition of citric acid on the preparation, namely SZG (before sugar) and SGZ (after sugar). The calcinations were conducted at 600οC and 800οC. XRD results show that at 600οC, t- and m-ZrO2 phases are identified in SZG, whereas t-ZrO2 is the only phase in SGZ. XRD analysis finds that both of the zirconia samples having had crystallites below 20 nm. At a high temperature of 800οC, two phases of zirconia are identified as t- and m-ZrO2 in both of the samples with different intensities. A Quanta FEG SEM study shows both of the zirconia samples at 800οC have homogenous microstructures and grain sizes less than 100 nm. A high resolution sophisticated SEM investigation shows that the SZG sample at 800οC has an average grain size below 50 nm. However, the effect of the citric acid addition time on the zirconia preparation is clearly visible in the zirconia phase transformation. The earlier addition of citric acid on the preparation gives two phases of zirconia in the final product at 600οC; and by contrast, the later addition of the acid after sugar on the preparation produces only t-ZrO2 phase.
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Hernawan,Rifki Septawendar,Naili Sofiyaningsih,Suhanda Sutardi 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.5
Nano-ZrO2 was succesfully prepared by calcining a precursor of a zirconium gel-emulsion in oleic acid. The gel-emulsion process was started with the preparation of a gel zirconium hydroxide. The hydroxide gel was then mixed with oleic acid at various ratios and heated at 200 oC to give zirconia precursors. These precursors were succesfully calcined at 800 oC, 1000 oC,and 1200 oC, to give zirconia powder. The crystal structure and the particle morphology of the calcined powder were identified using XRD, SEM, and TEM. The XRD results show that monoclinic zirconia is formed dominantly with crystallite sizes ranging from 46.2 to 55.3 nm at 800 oC. Meanwhile, the SEM micrographs of the zirconia calcined at 800 oC show particles with a homogenous morphology having sizes below 100 nm. The TEM results indicate that that the individual grain diameters of ZrO2 were less than 60 nm. A lower oleic acid concentration leads to a more alkaline condition and more monoclinic zirconia formed; and a higher calcination temperature leads to a larger size of crystallites.
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Dede Taufik,Mikrajuddin Abdullah,Hernawan,Suhanda Sutardi,Rifki Septawendar 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.10
Nanocrystallines of calcia-stabilized zirconia are known to reveal excellent mechanical and high ionic conductivity propertieswhose depend on the calcia concentration. In this work, nanocrystallines of calcia-stabilized zirconia were synthesized fromzircon precursor and 7.5 weight % CaO at 1000 oC, 1200 oC, and 1400 oC. Phase transformation and microstructure evolutionwere investigated by an X-ray diffraction and a scanning electron microscopy. Another un-doped zirconia was also synthesizedfrom the local zircon by following the same procedure for comparison. A fully cubic form of the calcia-stabilized zirconia andcalcium zirconate were obtained at 1200°C having the crystallite sizes ranging from 55 to 87 nm and remained stable at1400 oC. Meanwhile, un-doped zirconia consisted of pure the monoclinic zirconia at 1200 oC and 1400 oC. High agglomerationis found in the calcia-stabilized zirconia particles at 1000 oC, whereas grain boundaries and interconnect are observed at1400 oC. The cubic crystal of zirconia has specific and different finger print characteristics in the infra-red spectrum comparedto the monoclinic zirconia.
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