Local Er(III) environment in luminescent titanosilicates prepared from microporous precursors

The local environment of Er3+ ions in microporous titanosilicate ETS-10 and in synthetic narsarsukite and glassy materials obtained by calcination of ETS-10 has been investigated by EXAFS, Raman and photoluminescence spectroscopies. Er L-III-edge EXAFS studies of Er3+-doped ETS-10 support the view that the exchanged Er3+ ions reside close to the (negatively charged) TiO6 octahedra. In ETS-10, Er3+ is partially bonded to framework oxygen atoms and hydration water molecules. The Er...Ti distance (3.3 Angstrom) is similar to the Na...Ti distances (3.15-3.20 Angstrom) reported previously for Na-ETS-10. Although the exact location of the ErO6 units within the host structure of Er3+-doped synthetic narsarsukite is still an open question, it is most likely that Er3+ substitutes Ti4+ rather than Na+ ions. EXAFS spectroscopy indicates that no significant clustering of erbium atoms occurs in the titanosilicate samples studied. Evidence for the insertion of Er3+ ions in the framework of narsarsukite has been obtained by Raman spectroscopy. This is indicated by the increasing full-width at half-maximum (FWHM) of the 775 cm(-1) peak and the increasing intensity of the anatase peaks as the erbium content increases. In addition, as the narsarsukite Er3+ content increases a band at ca. 515 cm(-1) firstly broadens and subsequently a new peak appears at ca. 507 cm(-1).Er3+-doped narsarsukite exhibits a characteristic local vibrational frequency, (h) over bar omega ca. 330 cm(-1), with an electron-phonon coupling, g ca. 0.2, which constitutes additional evidence for framework Er3+ insertion. The number of lines in the infrared emission spectrum of synthetic narsarsukite indicates the presence of two optically-active erbium centres with very similar local environments and an average I-4(13/2) lifetime of 7.8 +/- 0.2 ms.

Observation of piezoelectric response on tungsten doped barium zirconium titanate ceramics

This study describes observation of piezoelectric response of Ba(Zr 0.10Ti 0.90.O3 ceramics modified with tungsten (BZT:2W) by the mixed oxide method. According to X ray diffraction analysis, the ceramics are free of secondary phases. Transmission electron microscopy (TEM) analyses reveals the absence of segregates in the grain boundaries indicates the high solubility of WO3 in the BZT matrix. The dielectric permittivity measured at a frequency of 10 KHz was equal to 6500 with dieletric loss of 0.15. A typical hysteresis loop was observed at room temperature. Electron Paramagnetic Resonance (EPR) analyses reveals that substitution of W6+ by Ti4+ causes distortion in the crystal structure changing lattice parameter. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning. Piezoelectric force microscopy images reveals that in-plane response may not change its sign upon polarization switching, while the out-of-plane response does. Copyright © 2010 American Scientific Publishers.

Synthesis and characterization of lead zirconate titanate (PZT) obtained by two chemical methods

Lead zirconate titanate (PZT) was synthesized at the ratio of Zr/Ti=52/48 using two synthesis methods: the polymeric precursor method (PPM) and the microwave-assisted hydrothermal method (MAHM). The synthesized materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size distribution by sedimentation, hysteresis measurements and photoluminescence (PL). The results showed that PZT powders are composed of tetragonal and rhombohedral phases. Different particle sizes and morphologies were obtained depending upon the synthesis method. From the hysteresis loop verified that PZT powders synthesized by the PPM have a typical loop of ferroelectric material and are more influenced by spatial charges while particles synthesized by the MAHM have a hysteresis loop similar to paraelectric material and are less influenced by spatial charges. Both samples showed PL behavior in the green region (525 nm) whereas the sample synthesized by the PPM showed higher intensity in spectra. © 2013 Elsevier Ltd and Techna Group S.r.l.

Estudos de materiais ferroelétricos por espectroscopia no infravermelho

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Atividade biológica e enzimática em solo tratado com cloreto e sulfato de bário

Pós-graduação em Agronomia (Produção Vegetal) - FCAV

Caracterização da deposição atmosférica e aporte de espécies químicas no principal corpo aquático da cidade de São José do Rio Preto, SP

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

Preparação de espumas cerâmicas de 'TIO IND. 2' a partir do processo sol-emulsão-gel

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Nitrogênio, arsênio, bário e estado nutricional de plantas de milho cultivadas em latossolos tratados com lodo de esgoto

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação da resistência ao cisalhamento e da durabilidade de união entre sistemas para reparo em metalocerâmicas e titânio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Síntese de cerâmicas ferroelétricas de PLZT–análise composicional e mecanismos de vacâncias

Pós-graduação em Ciência dos Materiais - FEIS

Effects of the addition of ions barium on the structural and electrical properties of PZT ceramic

Lead zirconate titanate, with Zr/Ti ratio of 53/47 was prepared by the polymeric precursor method. It was investigated the barium (II) modification at 0.0, 0.2, 0.4 and 0.6 mol% in substitution to the lead (II) cation in A site of perovskite structure. The powder samples were characterized by XRD and the diffraction patterns were used to Rietveld refinement. The percentages of tetragonal and rhombohedral phases and a systematic study of the effect of barium (II) on the morphology and the dielectric properties of PZT were carried out. The results showed that the tetragonal phase is favored and the ceramic density is improved with the barium (II) insertion. The Curie temperature (Tc) is increased besides the slight reduction of dielectric constant (Kc).

The TEL/platelet-derived growth factor β receptor (PDGFβR) fusion in chronic myelomonocytic leukemia is a transforming protein that self-associates and activates PDGFβR kinase-dependent signaling pathways

The TEL/PDGFβR fusion protein is the product of the t(5;12) translocation in patients with chronic myelomonocytic leukemia. The TEL/PDGFβR is an unusual fusion of a putative transcription factor, TEL, to a receptor tyrosine kinase. The translocation fuses the amino terminus of TEL, containing the helix-loop-helix (HLH) domain, to the transmembrane and cytoplasmic domain of the PDGFβR. We hypothesized that TEL/PDGFβR self-association, mediated by the HLH domain of TEL, would lead to constitutive activation of the PDGFβR tyrosine kinase domain and cellular transformation. Analysis of in vitro-translated TEL/PDGFβR confirmed that the protein self-associated and that self-association was abrogated by deletion of 51 aa within the TEL HLH domain. In vivo, TEL/PDGFβR was detected as a 100-kDa protein that was constitutively phosphorylated on tyrosine and transformed the murine hematopoietic cell line Ba/F3 to interleukin 3 growth factor independence. Transformation of Ba/F3 cells required the HLH domain of TEL and the kinase activity of the PDGFβR portion of the fusion protein. Immunoblotting demonstrated that TEL/PDGFβR associated with multiple signaling molecules known to associate with the activated PDGFβR, including phospholipase C γ1, SHP2, and phosphoinositol-3-kinase. TEL/PDGFβR is a novel transforming protein that self-associates and activates PDGFβR-dependent signaling pathways. Oligomerization of TEL/PDGFβR that is dependent on the TEL HLH domain provides further evidence that the HLH domain, highly conserved among ETS family members, is a self-association motif.

Crystallization behavior of (Cu60Zr30Ti10)(99)Sn-1 bulk metallic glass

The crystallization behavior and crystallization kinetics Of (CU60Zr30Ti10)(99)Sn-1 bulk metallic glass was studied by X-ray diffractometry and differential scanning calorimetry. It was found that a two-stage crystallization took place during continuous heating of the bulk metallic glass. Both the glass transition temperature T-g and the crystallization peak temperatures T-p displayed a strong dependence on the heating rate. The activation energy was determined by the Kissinger analysis method. In the first-stage of the crystallization, the transformation of the bulk metallic glass to the phase one occurred with an activation energy of 386 kJ/mol; in the second-stage, the formation of the phase two took place at an activation energy of 381 kJ/mol.

Precipitation studies on alloys from the system copper chromium zirconium

The precipitation reactions occurring in a series of copper-based alloys selected from the system copper-chromium-zirconium have been studied by resistometric and metallographic techniques. A survey of the factors influencing the development of copper-based alloys for high strength, high conductivity applications is followed by a more general review of contemporary materials, and illustrates that the most promising alloys are those containing chromium and zirconium. The few systematic attempts to study alloys from this system have been collated, discussed, and used as a basis for the selection of four alloy compositions viz:- Cu - 0.4% Cr Cu - 0.24. Zr Cu - 0. 3% Cr - 0.1% Zr Cu - 0.2% Cr - 0.2% Zr A description of the experimental techniques used to study the precipitation behaviour of these materials is preceeded by a discussion of the currently accepted theories relating to precipitate nucleation and growth. The experimental results are presented and discussed for each of the alloys independently, and are then treated jointly to obtain an overall assessment of the way in which the precipitation kinetics, metallography and mechanical properties vary with alloy composition and heat treatment. The metastable solid solution of copper-chromium is found to decompose by the rejection of chromium particles which maintain a coherent interface and a Kurdjumov-Sachs type crystallographic orientation relationship with the copper matrix. The addition of 0.1% zirconium to the alloy retards the rate of transformation by a factor of ten and modifies the dispersion characteristics of the precipitate without markedly altering the morphology. Further additions of zirconium lead to the growth of stacking faults during ageing, which provide favourable nucleation sites for the chromium precipitate. The partial dislocations bounding such stacking faults are also found to provide mobile heterogeneous nucleation sources for the precipitation reactions occurring in copper-zirconium.

Geoquímica de elementos maiores e traços de granitoides neoproterozoicos da província Borborema e sua correlação com propriedades físicas de rochas

This paper discusses the correlation of thermal conductivity, density and magnetic susceptibility with composition of major and trace elements of Neoproterozoic igneous bodies from Borborema Province, Northeastern Brazil. These properties were used as potential markers among the studied magmatic suites. For the correlation between petrophysical and geochemical properties it was considered a set of 195 chemical analyzes of granitoid rocks, separated by the degree of acidity in basic, intermediate and acidic. Major (SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O and TiO2) and some trace elements (Rb, Sr, Ba, Zr, Th and U) that are usually linked to the formation of the most common minerals of igneous rocks were used. The results show that SiO2 has the best positive correlation with the thermal conductivity, while Al2O3, CaO, Fe2O3, MgO and TiO2 exhibit negative correlation for the same property. The correlation with density is opposite to that one for these oxides with the thermal conductivity. The magnetic susceptibility did not correlate with the elements studied. The results for thermal conductivity and density indicate a tendency of SiO2 and oxides with higher affinity with mafic minerals (Al2O3, CaO, Fe2O3, TiO2 and MgO) in controlling these petrophysical parameters. The set of samples was divided into five different magmatic suites based on their lithogeochemical aspects into: i) peralkaline / alkaline; ii) alkaline; iii) calc-alkaline; iv) high potassium calcium alkaline; and v) shoshonitic. Data analysis showed that the thermal conductivity and density presented good results in the individualization of these suites, notably between peralkaline / alkaline, alkaline suites, calc-alkaline and shoshonitic. However, the high-K calc-alkaline suite overlapped with the other. In contrast, the magnetic susceptibility did not show effective results for separating the five chemical suites.