11th International Ceramics Congress

Volume 45

doi: 10.4028/www.scientific.net/AST.45

Paper Title Page

Authors: E.C.C. Souza, E.N.S. Muccillo
Abstract: Indium oxide, a wide band gap transparent conductor, is of great interest for many device applications due to its unusual combination of high transparency in the visible region and high electrical conductivity. Several methods, comprising all three phases, namely, the solid phase, the solution phase, as well as the vapor phase, have been used for the preparation of In2O3 powders and thin films. In this work, indium oxide nanoparticles were synthesized by homogeneous precipitation using hexamethylenetetramine as ligand and indium nitrate or indium chloride as precursor materials. Thermogravimetry and differential thermal analysis results evidenced the relatively low temperature for crystallization of indium oxide. Spherical clusters consisting of about 8 nm of diameter indium oxide nanoparticles were obtained after thermal decomposition at 400 °C for 2 h, as revealed by X-ray diffraction experiments and nitrogen adsorption measurements. Transmission electron microscopy observations confirm the single-crystalline nature of the prepared nanoparticles. This material exhibits photoluminescence emission at room temperature with peak onset at 315 nm as a consequence of the small size of the particles.
248
Authors: Jai Joon Lee, Jun Tae Kim, Kum Jin Park, Kang Heon Hur, Sang Man Koo
Abstract: We have investigated a novel synthesis for highly spherical and ultrafine barium titanate (BaTiO3) powders using a peptized titania (TiO2) nano-sol as a precursor. The obtained TiO2 nano-sol had the size less than 10 nm, which could be easily converted to BaTiO3 under 100 °C. The size of the resulting BaTiO3 powder could be controlled from 42 to 167 nm by lowering the solution concentration from 1.00 M to 0.15 M. BET analysis indicated that the as-prepared BaTiO3 powders had some porosity which was increased with the particle size. It was also found that the as-prepared BaTiO3 with smaller size had higher tetragonality and less intra-granular pores after annealing.
254
Authors: Antônio Hortêncio Munhoz Jr., Leila Figueiredo de Miranda, G.N. Uehara
Abstract: A pseudoboehmite was obtained by sol-gel synthesis using aluminum nitrate as precursor. It was used a 2n full factorial design for studying the effect of the temperature of synthesis, the concentration of ammonium hydroxide, and the radiation dose in the product of sol-gel synthesis. The product of the synthesis was analyzed by scanning electron microscopy, x-ray diffraction of the product (after firing the pseudoboehmite at different temperatures), and it was also analyzed the temperature of endothermic and exothermic transformations using the thermo gravimetric analysis (TG) and differential scanning calorimetry (DSC). The X-ray diffraction data show that α-alumina was obtained at 1100o C.
260
Authors: E. Tkalcec, H. Ivankovic, J. Macan, A. Hriberski
Abstract: Gels with cordierite stoichiometry, Mg2Al4Si5O18, were prepared by sol-gel technique using three different starting aluminum sources: nano-sized γ-Al2O3, aluminium nitrate nonahydrate and Al-sec-butoxide, as aluminum sources, using tetraetoxysilane (TEOS) and magnesium nitrate hexahydrate in all three gels as sources for silicon and magnesium. The influence of Al-precursors on formation mechanism and sintering behavior of gels was studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dilatometry. Gels calcined at 700°C were characterized by different specific surface area, pore sizes and different crystallization sequences. For gel with nano-sized γ-Al2O3 α-cordierite was formed at 1220°C through intermediate MgAl2O4 phase. If aluminum was introduced as Al-sec-butoxide μ-cordierite crystallized in two steps (760 and 1070°C) and the transformation μ-cordierite→α-cordierite occurred at 1250°C. When Al(NO3)3·9H2O was introduced as intermediate phase crystallized MgAl2O4 at ~870°C and μ- cordierite at ~950°C. Both phases reacted with amorphous silica forming α-cordierite at ~1210°C. Compacts prepared from gels with aluminum-nitrates and Al-sec-butoxide, respectively, sintered between 700 and 1000°C, whereas the gel derived from γ-Al2O3 sintered in two steps; between 700- 1000°C and 1010 and 1250°C.
266
Authors: T. Stoyanova, F. Matteucci, Anna L. Costa, M. Dondi, F.J. Carda
Abstract: Ceramic pigments with Cr-doped sphene structure (CaSn1-xCrxSiO5, CaTi1-xCrxSiO5) were synthesized by both spray drying an aqueous solution of precursor salts plus further calcining the resulting powders and conventional ceramic method. The thermal evolution of products was studied by X-Ray Powder Diffraction (XRPD). The powder morphology and chemical composition were analyzed by SEM-EDX. The color efficiency of pigments was evaluated by colorimetric analysis (CIELab system). Results showed that the spray drying process decreased the maximum firing temperature and increased the color efficiency of Cr-doped sphene pigments therefore enhancing a higher reactivity of powders compared with the solid state process.
272
Authors: Ewa Stobierska, Jerzy Lis, Mirosław M. Bućko, Agnieszka Gubernat
Abstract: The results of preliminary investigation on preparation of perovskite pigments by solid state reaction are presented. The effects of different raw materials used as component carriers on formation of colored pigments were examined. Pigment composition, optimum chromophore addition, type of mineralizer and the conditions of synthesis were determined experimentally as well as the resulting color, phase composition and morphology of powders. The wet method of preparation of starting mixtures was also analyzed.
276
Authors: Takamasa Ishigaki, Ji Guang Li, Yusuke Moriyoshi
Abstract: Fe- and Eu-doped TiO2 nanocrystals were synthesized via Ar/O2 thermal plasma oxidation of liquid precursor mists. The use of mists ensures atomic level mixing of the elements and high supersaturation of the evaporated species upon plasma oxidation, which favors nanocrystal formation upon condensation. Iron-doped TiO2 nanopowders with controlled iron to titanium atomic ratios (RFe/Ti) ranging from 0 to 20%, were synthesized by oxidative pyrolysis of liquid-feed metallorganic precursors containing titanium tetra-n-butoxide (TTBO) and ferrocene. Europium doped TiO2 luminescent nanocrystals were also synthesized via RF thermal plasma oxidation of liquid precursor mists containing TTBO and europium nitrate.
281
Authors: C.M. Wang, S.L. Chung
Abstract: This investigation was aimed at preparing nanocrystalline TiO2 powder by self-propagating-high-temperature synthesis. Titanium (IV) n-butoxide was hydrolyzed to obtain titanl hydroxide [TiO(OH)2], and titanyl nitrate [TiO(NO3)2] was obtained by reaction of TiO(OH)2 with nitric acid. Finally, the aqueous solution containing titanyl nitrate [TiO(NO3)2] and a fuel, urea, were mixed and combusted to obtain the nano-sized titania. The anatase TiO2 nanocrystalline ( ~56nm) with high BET surface area( 280 m2g-1) and narrow band gap energy( 2.7 eV) were thus obtained.
285
Authors: M. Ivanov, V. Osipov, Yu. Kotov, V. Lisenkov, V. Platonov, V. Solomonov
Abstract: Oxide nanopowders Y2O3, ZrO2, YSZ (Y2O3-stabilized ZrO2), Ce0.8Gd0.2O2 and Y2O3- Al2O3 compounds were prepared with the help of laser evaporation and subsequent vapor condensation in the flow of buffer gas. An efficient technology and setup to produce high purity weakly agglomerated nanopowders are demonstrated. The output rate, alteration of elemental composition, size distribution and crystalline structure of the nanopowders depending on parameters of laser radiation and buffer gas flow are reported.
291
Authors: Ludosław Stobierski, Jerzy Lis, Agnieszka Gubernat
Abstract: The activation of silicon carbide by boron and carbon is required to obtain dense monophase sintered body from SiC powder. The presence of carbon renders casting from aqueous suspension impossible. The SiC powders with boron and extra carbon were prepared by combustion method (SHS), where carbon was bound to SiC particles in a stable way. The experiments showed that this powder could be used for processing by casting of aqueous suspension. Finally nearly dense polycrystals were obtained by pressureless sintering.
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