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.
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.
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.
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.
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.
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.
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.
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.
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.
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.