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Synthesis and Characterization of Alumina-Zirconia Nanopowders via an Oxalate Route
Chandradass, J.,Park, Hoy-Yul,Balasubramanian, M.,Bae, Dong-sik TaylorFrancis 2008 Materials and manufacturing processes Vol.23 No.8
<P> Nanocrystalline Al2O3-ZrO2 powder was synthesized by a simple method using oxalic acid as a chelating agent. The formation temperature of α - Al2O3 was investigated by differential thermal analysis. X-ray diffraction (XRD) analysis shows that t-ZrO2 was stabilized in alumina matrix with oxalic acid content 0.5 M and 1 M, respectively. In addition, the data from XRD showed α-Al2O3 and t-ZrO2 phase can be formed at 1100°C with 1 M oxalic acid content. Transmission electron microscope (TEM) micrograph of calcined powders revealed as the oxalic acid content in the precursor solutions is increased from 0.25 M to 0.5 M concentration. The obtained materials could be modified from segregated nanoparticles to agglomerated nanoparticles and finally to large agglomerate with 1 M concentration of oxalic acid. The Fourier transform infrared spectra (FTIR) confirms the formation of α-Al2O3 in corroboration with X-ray studies.</P>
Chandradass, J.,Dong Sik Bae, SAGE Publications 2009 Journal of reinforced plastics and composites Vol.28 No.10
<P>This article presents the experimental study of thermomechancial, free vibration, and damping characteristics by reinforcing barium titanate nanopowder (0, 1, 3 and 5 wt%) in the epoxy matrix using the resin casting method. Theoretical study is also carried out to study the vibration characteristics of barium titanate/epoxy nanocomposites. Dynamic mechanical analysis shows an increase in the storage modulus and glass transition temperature with a maximum value of 6400 MPa and 154U00B0;C for 3 wt% barium titanate nanopowder in epoxy polymer matrix. Dynamic results show that the second phase barium titanate nanopowder dispersion in the epoxy matrix enhances the internal damping of laminates up to 3 wt%.</P>
Chandradass, J.,Jun, B.,Bae, D.s. North-Holland 2008 Journal of non-crystalline solids Vol.354 No.26
In this research, a sol-gel autocombustion route has been proposed to synthesize alumina-zirconia nanopowder, using aluminium nitrate, zirconium oxychloride and various fuels such as citric acid, acetylacetone, oxalic acid and urea. The phase analysis and particle size in the presence of different fuel were compared. The results showed 100% tetragonal phase as well as particle size of ∼60nm in the presence of citric acid. FTIR confirms the formation of α-Al<SUB>2</SUB>O<SUB>3</SUB> in corroboration with X-ray studies.
Preparation and Properties of Barium Titanate Nanopowder/Epoxy Composites
Chandradass, J.,Bae, Dong-sik TaylorFrancis 2008 Materials and manufacturing processes Vol.23 No.2
<P> This article is focused on the preparation of barium titanate nanopowder/epoxy composites and studying the effect of barium titanate nanopowder on improving mechanical and thermal characteristics of the epoxy polymer. Composites are prepared by dispersing barium titanate nanopowder in epoxy resin and, subsequently, cross-linking by using diamino diphenyl methane (DDM) curing agents. Synthesis of barium titanate nanopowder/epoxy composites is carried out for different concentrations (1, 3, and 5 by weight) of barium titanate nanopowder at high temperature. High-temperature curing (HTC) involves mixing the resin-nanopowder solution followed by DDM hardener and curing at 120°C. Tensile, flexure, and impact results showed a maximum value of 72.7 MPa, 2.98 GPa, and 2 J/cm, respectively. DSC analysis revealed that curing occurs at low temperature in the presence of barium titanate nanopowder. Thermogravimetry analysis (TGA) showed the increased thermal stability in the nanoparticle filled epoxy composites as compared with the pure epoxy counterparts. Dynamic mechanical analysis (DMA) revealed, maximum storage modulus of 6400 MPa and glass transition temperature of 154°C for 3 wt% barium titanate nanopowder.</P>
Synthesis of calcium hexaaluminate (CaAl<sub>12</sub>O<sub>19</sub>) via reverse micelle process
Chandradass, J.,Bae, D.S.,Kim, K.H. North-Holland 2009 Journal of non-crystalline solids Vol.355 No.48
This letter describes the synthesis of CaAl<SUB>12</SUB>O<SUB>19</SUB> powders using micro reactors made of Igepal CO520/water/cyclohexane microemulsions. Characterization of the powder was done by DTA-TGA, X-ray diffraction, Scanning electron microscopy, Fourier Transform Infrared Spectroscopy. The XRD results show that the hexagonal CaAl<SUB>12</SUB>O<SUB>19</SUB> powders have been obtained at 1200<SUP>o</SUP>C for 2h. The SEM examination shows that the hexagonal CaAl<SUB>12</SUB>O<SUB>19</SUB> has plate-like grain morphology with most of the grain took the form of hexagonal platelets with-developed faces. The FTIR spectra show the lower frequency bands are assigned to AlO<SUB>6</SUB> octohedra and AlO<SUB>4</SUB> tetrahedra in CaAl<SUB>12</SUB>O<SUB>19</SUB>.
Chandradass, J.,Balasubramanian, M.,Kumar, S.,Bae, D.S.,Kim, K.H. Elsevier 2010 CURRENT APPLIED PHYSICS Vol.10 No.1
Observation of room temperature ferromagnetism in Fe doped In<SUB>2</SUB>O<SUB>3</SUB> samples (In<SUB>1-x</SUB>Fe<SUB>x</SUB>)<SUB>2</SUB>O<SUB>3</SUB> (0=<x=<0.07) prepared by co-precipitation technique is reported. Lattice parameter obtained from powder X software shows distinct shrinkage of the lattice constant indicating an actual incorporation of Fe ions into the In<SUB>2</SUB>O<SUB>3</SUB> lattice. X-ray diffraction data measurements show that the entire sample exhibits single phase polycrystalline behavior. SEM micrographs showed the prepared powder was in the range 25-36nm. SEM EDS mapping showed the presence of Fe and In ions in the Fe doped In<SUB>2</SUB>O<SUB>3</SUB> sample. The highest remanence magnetization moment (6.624x10<SUP>-4</SUP>emu/g) is reached in the sample with x=0.03.
J. Chandradass,M. Balasubramanian,샤런드라쿠마르,배동식,김기현 한국물리학회 2010 Current Applied Physics Vol.10 No.1
Observation of room temperature ferromagnetism in Fe doped In2O3 samples (In1-xFex)2O3 (0 6 x 6 0.07)prepared by co-precipitation technique is reported. Lattice parameter obtained from powder X software shows distinct shrinkage of the lattice constant indicating an actual incorporation of Fe ions into the In2O3 lattice. X-ray diffraction data measurements show that the entire sample exhibits single phase polycrystalline behavior. SEM micrographs showed the prepared powder was in the range 25.36 nm. SEM EDS mapping showed the presence of Fe and In ions in the Fe doped In2O3 sample. The highest remanence magnetization moment (6.624 × 10-4 emu/g) is reached in the sample with x = 0.03.
J. Chandradass,김기현 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.1
The effect of the Mg/Al ratio on the synthesis of MgAl2O4 nanoparticles by a reverse micelle process has been investigated in order to identify the phase composition in this system. Our study shows that the precursor ratio has significant effects on the structure and composition of the resulting nanoparticles. From the XRD analysis, a well-crystallized MgAl2O4 phase was formed at Mg/Al = 0.5 whereas at Mg/Al = 1, the crystallization of the nanoparticles was sluggish with MgAl2O4 and θ-Al2O3phases co-existing. By optimizing the Mg/Al ratio in the micelle solution, the average particle size of MgAl2O4 nanoparticles as determined from SEM and TEM were found to be 18 and 14 nm, respectively. The FTIR spectra show the lower frequency bands are assigned to metal-oxygen bonds (M–O–M). The thermal behavior of the precursor powders was characterized by DTA-TGA analysis.
Effect of Acidity on the Citrate-Nitrate Combustion Synthesis of Alumina-Zirconia Composite Powder
J.Chandradass,김기현 대한금속·재료학회 2009 METALS AND MATERIALS International Vol.15 No.6
Alumina-zirconia composite powders were produced by sol-gel autocombustion. 20 wt.% ZrO2-Al2O3 mixture precursor solutions were chelated by citric acid ions at different pH. DTA analysis shows sluggish decomposition at low pH, whereas there was rapid decomposition at high pH = 9. XRD patterns of the calcined powders showed that well crystallized powder with 100 % tetragonal phase and α-alumina phase is produced when pH = 0.58 (without ammonia addition). TEM characterization of composite powders revealed homogenous distribution of nanosized zirconia particles in the alumina matrix. FTIR analysis shows peaks at 590 cm−1 and 454 cm−1 , which are identified as the characteristic absorption bands of Zr-O and Al-O. Alumina-zirconia composite powders were produced by sol-gel autocombustion. 20 wt.% ZrO2-Al2O3 mixture precursor solutions were chelated by citric acid ions at different pH. DTA analysis shows sluggish decomposition at low pH, whereas there was rapid decomposition at high pH = 9. XRD patterns of the calcined powders showed that well crystallized powder with 100 % tetragonal phase and α-alumina phase is produced when pH = 0.58 (without ammonia addition). TEM characterization of composite powders revealed homogenous distribution of nanosized zirconia particles in the alumina matrix. FTIR analysis shows peaks at 590 cm−1 and 454 cm−1 , which are identified as the characteristic absorption bands of Zr-O and Al-O.