Preparation of nano α-Al2O3 from kaolin belitung by liquid polish milling

Rifki Septawendar 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.1

Nano α-Al2O3 powders were successfully prepared from Indonesian local kaolin, kaolin Belitung. Nano α-Al2O3 powders were prepared by alumina extraction processes through liquid polish milling of the calcined kaolin with a H2SO4 solution, thus producing kaolin derived aluminum sulfate. Calcination treatments were conducted at 600 ο C and 800 ο C. The greatest alumina extracted was about 70.90% for the local kaolin calcined at 800 ο C. The aluminum sulfate was neutralized with a NH4OH solution until pH 7-8 to form white sols of Al(OH)3. Sugar was added into the mixture to mask the sols, thus producing gels. The gel was dried at 200 ο C and then was calcined at 900 ο C for 5 hours, which resulted in the formation of alumina. The calcined alumina was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The alumina phases consisted of a γ- Al2O3 phase of about 47.6% having crystallite sizes of about 4-5 nm and an α-Al2O3 phase of about 52.4% having crystallite sizes of about 19-26 nm. The SEM result shows that the average grain sizes of the alumina powder were less than 250 nm.

Roles of alumina, a base catalyst, a fine particle effect on the metastable phase Stabilization of the tetragonal zirconia at temperatures of 600-800 ℃

Rifki Septawendar,Suhanda,Soesilowati,Bambang Sunendar Purwasasmita 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.4

Nanoparticles of the tetragonal alumina-stabilized zirconia were synthesized from zirconium salt of ZrOCl2 • 8H2O and approximately 23 wt % alumina stabilizer with ammonia as a base catalyst and sucrose as a gelling agent at a room temperature. In the preparation process of nanoparticles of alumina-stabilized zirconia, the calcination was conducted at temperatures of 500-800 ℃. The calcined powder was analyzed and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) studies. The tetragonal phase of ZrO2 started to crystallize at a low temperature of 500 ℃. Further phase transformation of the alumina-stabilized zirconia maintained the tetragonal ZrO2 at 600 ℃. Besides, the addition of sucrose by weight ratio of 1 : 6 to the total weight precursors produced nanoparticles of alumina-stabilized zirconia less than 20 nm in size at that temperature. The tetragonal phase of ZrO2 was stable and no transition alumina was identified at 800 ℃. It is suggested that alumina is in solid solution in the tetragonal zirconia polymorph at that temperature. The typical SEM images show high agglomeration of ultrafine microstructures of alumina-stabilized zirconia nanoparticles at that temperature. The results indicate that the method represents an effective methodology for the preparation of alumina-stabilized zirconia nanoparticles at a lower temperature than 800 ℃.

Nanocrystalline α-Al2O3 powder preparation with sucrose as a template through a chemical route

Rifki Septawendar,Suhanda,Frank Edwin 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.4

Nanocrystalline α-Al2O3 powder was prepared through a chemical route via a reaction between aluminum nitrate nona hydrate with a sucrose template in variation ratios of the salt to the organic namely 1 : 2, 3 : 1, and 6 : 1 at a heating temperature of 200 oC. The homogenization process of the nanopowder was assisted by milling a“charcoal precursor” in a non polar solvent for 24 hours, which was then successfully calcined at temperatures of 900 oC and 1100 oC. The products were evaluated by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optimum condition was obtained at a ratio of the aluminum salt to the organic compound of about 6 : 1, at a calcination temperature of 900 oC, which produced a 100% pure α-Al2O3 phase with a crystallite size of 44.6 nm. The SEM micrographs showed the particle sizes of nanocrystalline α-Al2O3 powders were found to be near 100 nm at 1100 oC. The TEM results indicate that nanocrystalline α-Al2O3 powders calcined at 900 oC had grain sizes below 50 nm. An increase of the sucrose concentration leads to smaller crystal sizes, meanwhile an elevation of the calcination temperature from 900 oC to 1100 oC leads to the formation of larger particle and crystal sizes of alumina.

Alumina phase transformation behavior on titania-doped nano α-alumina by a solid liquid process

Rifki Septawendar,Soewanto Rahardjo,Suhanda,Wisnu Hardik Pratomo 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.6

Alumina phase transformation behavior on titania-doped nano α-Al2O3 powder by a solid liquid process was investigated under various conditions, such as different solvent concentrations and calcining temperatures. Three batches of the precursor powders were calcined at three different temperatures of 600 oC, 750 oC and 900 oC for 5 h and a final product of titania-doped nano α-Al2O3 powder was obtained. The product has been identified by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The XRD results show that the alumina phases of the powders were determined to be γ-Al2O3 and α-Al2O3. The optimum calcination temperature of the precursor powder for crystallization of nano α-Al2O3 was found to be 900 oC for 5 h. A higher concentration of solvent used for the sample preparation leads to the formation of a uniform and very smooth particle morphology, and smaller particle grains. The TEM images indicate that the average size of α-Al2O3 grains was ≤ 50 nm and larger grains of TiO2 with 50-250 nm sizes.

Low-temperature crystallization at 700 oC of magnesium aluminate nanospinel Using nitrate precursors by masking-gel calcination process

Rifki Septawendar 한양대학교 세라믹연구소 2014 Journal of Ceramic Processing Research Vol.15 No.6

Nanoparticles MgAl2O4 spinel with the cubic crystal structure was successfully prepared through masking-gel calcination process, using aluminum and magnesium nitrates as spinel precursors and sugar as a masking-gel agent. Calcination treatment was performed at 600 o C, 700 o C, 800 o C, 900 o C, and 1000 o C. X-ray diffraction analysis, transmission electron microscopy and scanning electron microscopy studies were conducted to identify the crystalline phase and the microstructure of the spinel product. The metal nitrate precursors were found to crystallize completely as MgAl2O4 spinel at a low temperature of 700 o C having crystallite sizes below 15 nm. The average particle sizes of the spinel powder at that temperature were less than 75 nm. The microstructure analysis of the spinel sample at the calcination temperature of 1000 o C shows the particle sizes below 100 nm and high formation of agglomerates.

Nanocrystalline ZrO2 powder preparation using natural cellulosic material

Rifki Septawendar,Bambang Sunendar Purwasasmita,Suhanda,Leanddas Nurdiwijayanto,Frank Edwin 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.1

Nanocrystalline zirconia powder has been successfully prepared using a precursor calcination process involving hydrolysis of zirconium(IV) isopropoxide and utilizing Oryza Sativa pulp (Merang Pulp) as the cheapest natural template. The potential of Oryza Sativa pulp as a template in the preparation of nanocrystalline zirconia is investigated in this research. It is also shown that the presence of the pulp can produce zirconia in nanocrystallites because the agglomeration tendency has been reduced in the as-synthesized ZrO2 particles. The effect of the calcination temperature on this zirconia preparation is found out by variation of the applied calcination temperature. XRD characterization shows monoclinic zirconia as a fully dominant phase,and the largest ZrO2 crystallite is found to be 42.7 nm. However, the zirconia crystallite size will increase with an elevation of the calcination temperature.

Effect of sugar and citric acid as precursors in ZrO2 nanopowder preparation at low calcination temperatures

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.

The zirconia phase transformation in the preparation of nano zirconia by calcining a gel-emulsion precursor

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.

Mineral phase, microstructure, and Infra-Red characteristics of calcia-stabilized zirconia nanocrystallines synthesized from local zircon and slaked lime

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.

Geopolymer–carbonated apatite nanocomposites with magnesium and strontium trace elements for dental restorative materials

Dahlia Sutanto,Mieke Hemiawati Satari,Bethy S. Hernowo,Bambang Pontjo Priosoeryanto,Rifki Septawendar,Lia A. T. W. Asri,Bambang Sunendar Purwasasmita 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.5

Geopolymer and carbonated apatite are potential materials for dental restoration. We reported the synthesis of geopolymer– carbonated apatite nanocomposite, highlighting the infl uence of trace elements in carbonated apatite toward mechanical, leachability and cytotoxicity properties. Various carbonated apatites were combined with metakaolin, followed by geopolymerization. The study revealed that with addition of Mg 2+ and Sr 2+ , the geopolymer–carbonated apatite nanocomposites have the tendency to have lower mechanical properties. Geopolymer and geopolymer–carbonated apatite showed higher hardness, compressive strength, and modulus elasticity compared with geopolymer–carbonated apatite containing Mg 2+ and/ or Sr 2+ . Nevertheless, all samples showed mechanical properties that could be applied as dental restoration materials. Leaching assay confi rmed the release of Na + in all samples, originating from unreacted alkali activator. The Na + concentration decreased signifi cantly after 96 h of total washing, with the lowest value of 1 ppm. Cytotoxicity test was evaluated toward mouse embryonic fi broblast cells, indicating that all samples were not toxic to cells.