Synthesis and characterization of glass-ceramic microspheres for thermotherapy

Glass microspheres containing radionuclides are used to treat liver cancer. A promising alternative therapy is being developed based on the magnetic hyperthermia which is related to the heat supplied by a magnetic material under an alternating current magnetic field. The advantage of this option is that most of killed cells are cancer cells which are more susceptible to the temperature raise. In the present work aluminum iron silicate glasses containing minor glass modifiers and nucleating agents were synthesized as irregular shape particles which were further transformed in microspheres by using a petrol liquefied gas-oxygen torch. The optimized processing parameters which lead to microspheres that give a response to the magnetic field were determined. The dissolution rate in water at 90 degrees C was determined to be 3 x 10(-8) g cm(-2) min(-1). The microsphere size distribution was determined by laser scattering. The crystalline phase responsible for the ferromagnetic response was identified as magnetite. Since this phase has a high saturation magnetization and high Curie temperature, it is potentially useful for biomedical applications. The hysteresis magnetic loop was measured for materials produced in different conditions, and some of them showed to be appropriated for thermotherapy. The ratio Fe(3+)/Fe(total) was determined by Mossbauer spectroscopy. (C) 2010 Elsevier B.V. All rights reserved.

Synthesis and characterization of phosphate glass microspheres for radiotherapy applications

Class microspheres containing the radioisotope (32)P, a beta(-) particle emitter, and half-life of 14.3 days, can be easily introduced in specific human organs such as liver, pancreas. and uterus to kill cancer cells. In the present work phosphate glass microspheres were produced with different compositions and particle size distribution in the range of 20- 30 mu m. Two different thermal processes were used to spherodize glass particles originally with irregular shapes. Samples were characterized by X-rays diffraction to check the amorphous structure, energy dispersive X-rays fluorescence spectroscopy to determine the final glass composition, and Fourier transformed infrared spectroscopy to determine the structural groups in the glass structure. The dissolution rate of glass samples in water was determined at 90 degrees C, and in simulated body fluid (SBF) at 37 degrees C. Classes with dissolution rates close to 10(-5) g/(cm(2) day) were obtained, which make them suitable for the present application. Scanning electron microscopy was used to evaluate the shape of the microspheres before and after the dissolution tests. The cytotoxicity tests showed that these microspheres can be used for biological applications. (C) 2008 Elsevier B.V. All rights reserved.

Oxide surface modification: Synthesis and characterization of zirconia-coated alumina

Four aluminas were used as Supports for impregnation with a zirconium oxide with the aim to achieve a coating, without phase separation, between Support and modifier. The Supports were impregnated with different concentrations Of zirconium aqueous resin, obtained through the polymeric precursor method. After impregnation the samples were calcined and then characterized by XRD, which led to identification of crystalline zirconia in different concentrations from each support used. Using a simple geometric model the maximum amount Of Surface modifier Oxide required for the complete coating of a support with a layer of unit cells was estimated. According to this estimate, only the support should be identified below the limit proposed and crystalline zirconium oxide Should be identified above this limit when a complete coating is reached. The results obtained From XRD agree with the estimated values and to confirm the coating, the samples were also characterized by EDS/STEM, HRTEM, XPS, and XAS. The results showed that the zirconium oxide oil the Surface of alumina Support reached the coating in the limit of 15 Zr nm(-2), without the formation of the ZrO(2) phase. (c) 2009 Elsevier Inc. All rights reserved.

Preparation and characterization of Cd(2)Nb(2)O(7) thin films on Si substrates

Thin Cd(2)Nb(2)O(7) films were grown on single-crystal p-type SiO(2)/Si substrates by the metallo-organic decomposition (MOD) technique. The films were investigated by X-ray diffraction, X-ray energy-dispersive spectroscopy, and field emission scanning electron microscopy, and showed a single phase (cubic pyrochlore), a crack-free spherical grain structure, and nanoparticles with a mean size of about 68 nm. A Cauchy model was also used in order to obtain the thickness and index of refraction of the stack layers (transparent layer/SiO(2)/Si) by spectroscopic ellipsometry (SE). The dielectric constant (K) of the films was calculated to be about 25 from the capacitance-voltage (C-V) measurements. (c) 2008 Elsevier Ltd. All rights reserved.

Structural and spectroscopic characterization of poly(styrene sulfonate) films doped with neodymium ions

This work reports the structural and spectroscopy characterization of poly(styrene sulfonate) (PSS) films doped with neodymium (Nd) ions. Nd-PSS films were processed using the acid of poly(styrene sulfonate) - H-PSS and neodymium nitrate - Nd(NO(3))(3); the maximum incorporation of Nd ions in the polymeric matrix was equal 19.3%. The absorption in the UV-Vis-NIR spectral region presents typical electronic transitions of Nd 3, ions, with well resolved peaks. The infrared spectra present the transition bands of PSS with characteristic line shape broadening, and the presence of vibrational modes of N-O groups in the range of 1400-720 cm(-1), prove the permanence of Nd(NO(3))(x), with x = 1, 2 and/or 3. in the H-PSS matrix. UV-Vis site selective photoluminescence data indicate that the incorporation of Nd 31 introduces a blue shift in PSS emission (325-800 nm), decreasing the interaction between adjacent PSS lateral groups (aromatic rings). Nd(3+) reabsorption and energy transfer effects between the PSS matrix and Nd(3+) were also observed. The IR emission of Nd-PSS films at 1076 rim ((4)F(3/2) -> (4)I(11/2)) present constant efficiency, independent on Nd(3+) concentration. The Judd-Ofelt theory was employed to analyze radiative properties. The excitation spectra prove the energy transfer between the polymeric matrix and Nd(3+). Complex impedance data was used to probe relaxation processes during the charge transport within the polymeric matrix. (C) 2008 Elsevier B.V. All rights reserved.

Fluorescent AlPO(4) gels and glasses doped with Rhodamine 6G: Preparation, structural and optical characterization

Fluorescent AlPO(4) xerogels doped with different amounts of Rhodamine 6G (Rh6G) laser dye were prepared by a one-step sal-gel process. In addition, mesoporous AlPO(4) glasses obtained from undoped gels were loaded with different amounts of Rh6G by wet impregnation. Optical excitation and emission spectra of both series of samples show significant dependences on Rh6G concentration, revealing the influence of dye molecular aggregation. At comparable dye concentrations the aggregation effects are found to be significantly stronger in the gels than in the mesoporous glasses. This effect might be attributed to stronger interactions between the dye molecules and the glass matrix, resulting in more efficient dye dispersion in the latter. The interaction of Rh6G with the glassy AlPO(4) network has been probed by (27)Al and (31)P solid-state NMR techniques. New five- and six-coordinated aluminum environments have been observed and characterized by advanced solid-state NMR techniques probing (27)Al-(1)H and (27)Al-(31)P internuclear dipole couplings. The fractional area of these new Al sites is correlated with the combined fractional area of two new Q(3Al)((0)) and Q(2Al)((0)) phosphate species observed in the (31)P MAS NMR spectra. Based on this correlation as well as detailed composition dependent studies, we suggest that the new signals arise from the breakage of Al-O-P linkages associated with the insertion process. (C) 2010 Elsevier B.V. All rights reserved.

Optical and electrical characterization of samaria-doped ceria

Ce(0.8)SM(0.2)O(1.9) and CeO(2) nanomaterials were prepared by a solution technique to produce an ultrafine particulate material with high sinterability. In this work, the structural characteristics, the photoluminescent behavior and the ionic conductivity of the synthesized materials are focused. The thermally decomposed material consists of less than 10 nm in diameter nanoparticles. The Raman spectrum of pure CeO(2) consists of a single triple degenerate F(2g) model characteristic of the fluorite-like structure. The full width at half maximum of this band decreases linearly with increasing calcination temperature. The photoluminescence spectra show a broadened emission band assigned to the ligand-to-metal charge-transfer states O -> Ce(4+). The emission spectra of the Ce(0.8)Sm(0.2)O(1.9) specimens present narrow bands arising from the 4G(5/2) -> (6)H(J) transitions (J = 5/2, 7/2, 9/2 and 11/2) of Sm(3+) ion due to the efficient energy transfer from the O -> Ce(4+) transitions to the emitter 4G(5/2) level. The ionic conductivity of sintered specimens shows a significant dependence on density. (C) 2009 Elsevier B.V. All rights reserved.

Electrodeposition and characterization of undoped and nitrogen-doped ZnSe films

Semiconducting films of (n-type) ZnSe and (p-type) nitrogen-doped ZnSe were electrodeposited by a linear-sweep voltammetric technique on to a substrate of fluorine-tin oxide (FM) glass ceramics. The films were characterized by scanning electron microscopy, energy-dispersive X-ray analysis and grazing-incidence X-ray diffraction. The results indicated that the material was deposited uniformly over the substrate, forming clusters when the Zn content of the bath was 0.1 mol L(-1) and a film when it was 0.2 or 0.3 mol L(-1). The effectiveness of doping the films with nitrogen by adding ammonium sulfate to the deposition solution was assessed by measuring the film-electrolyte interface capacitance (C) at various applied potentials (E(ap)) and plotting Mott-Schottky curves (C(-2) vs E(ap)), whose slope sign was used to identify p-type ZnSe. (C) 2009 Elsevier B.V. All rights reserved.

EFFECT of DIFFERENT SOLID AMOUNTS IN THE PHYSICAL and MICROSCOPICAL PROPERTIES of SiC POROUS CERAMICS

The presence of pores in ceramics is directly related to the chosen forming process. So, in the starch consolidation method, the ceramics show, after burning, pores with morphology similar to that presented by this organic material. on the other hand, the increase in solid load leads up to alterations in dispersion viscosity, increasing the thermal stresses during drying and sintering processes. In order to verify the solid percentage influence in ceramic final properties, samples were prepared with silicon carbide in different compositions using or not starch as binder agent and pore forming element. The characterization of the ceramic pieces was performed by superficial roughness measurements, porosity besides by optical and scanning electron microscopy. The results showed ceramics with SiC and starch presented physical and microscopic properties slightly higher in relation to those with only ceramic powder in their composition. The presence of organic material, agglomerated and foam during the forming were essential for the final properties of the studied samples.

Effect of lithium additive on the microstructure and electrical responses of 0.9PMN-0.1PT ceramics

Structural effects of lithium additive on 0.9PMN-0.1PT powders prepared by Ti-modified columbite route were studied. The substitution of Li+ ions for Mg2+ ions in the B-site sub-lattice of 0.9PMN-0.1PT perovskite structure was explained in terms of lead and oxygen vacancies generation originated as consequence of the ionic compensation of negatively charged Li'(Mg) sites. The rise in mass transport as consequence of the increasing of Pb2+ and O2- vacancies produces more agglomerated particles during the powder synthesis and changes the mechanical characteristics between grain and grain boundary of sintered ceramic. The relation between K-m and T-m values, the difference between ionic radii of B cation and the molar volume were used to explain the changes in the relaxor behavior and diffusiveness of phase transition as function of lithium doping, which are corroborated by the results obtained through the ferroelectric characterization.

Structural characterization of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) powders

The present work reports the effects caused by barium on phase formation, morphology and sintering of lead magnesium niobate-lead titanate (PMN-50PT). Ab initio study of 0.5PbMg(1/3)Nb(2/3)O(3)-0.5Ba(x)Pb((1-x))TiO(3) ceramic powders, with x = 0, 0.20, and 0.40 was proposed, considering that the partial substitution of lead by barium can reestablish the equilibrium of monoclinic-tetragonal phases in the system. It was verified that even for 40 mol% of barium, it was possible to obtain pyrochlore-free PMN-PT powders. The increase of the lattice parameters of PMN-PT doped-powders confirmed dopant incorporation into the perovskite phase. The presence of barium improved the reactivity of the powders, with an average particle size of 120 nm for 40 mol% of barium against 167 mn for the pure sample. Although high barium content (40 mol%) was deleterious for a dense ceramic, contents up to 20 mol% allowed 95% density when sintered at 1100 degrees C for 4 h. (c) 2007 Elsevier Ltd. All rights reserved.

Structural and magnetic characterization of MnxZn1-xFe2O4 (x=0.2; 0.35; 0.65; 0.8; 1.0) ferrites obtained by the citrate precursor method

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Synthesis, characterization, structural refinement and optical absorption behavior of PbWO(4) powders

The present paper describes the synthesis, characterization, structural refinement and optical absorption behavior of lead tungstate (PbWO(4)) powders obtained by the complex polymerization method heat treated at different temperatures for 2h in air atmosphere. PbWO(4) powders were characterized by X-ray diffraction (XRD), Rietveld refinement, Fourier transform Raman (FT-Raman) spectroscopy and ultraviolet visible (UV-vis) absorption spectroscopy measurements. XRD, Rietveld refinement and FT-Raman revealed that PbWO(4) powders are free of secondary phases and crystallizes in a tetragonal structure. The UV-vis absorption spectroscopy measurements suggest the presence of intermediary energy levels into the band gap of structurally disordered powders. (C) 2008 Elsevier B.V. All rights reserved.

Synthesis and characterization of mesoporous TiO2 nanostructured films prepared by a modified sol-gel method for application in dye solar cells

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of heat treatment on the generation of structural defects in LaTaO4 ceramics and their correlation with photoluminescent properties

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)