22 research outputs found
Influence of Dopants, Temperature and Atmosphere of Sintered on the Microstructure and Behavior of Lead Free Ceramics
Effect of oxidizing and reducing atmospheres on Ba(Ti0.90Zr0.10)O3:2V ceramics as characterized by piezoresponse force microscopy
The effect of annealing atmospheres (At amb, N2 and O2) on the electrical properties of Ba(Ti0.90Zr0.10)O3:2V (BZT10:2V) ceramics obtained by the mixed oxide method was investigated. X-ray photoelectron spectroscopy (XPS) analysis indicates that oxygen vacancies present near Zr and Ti ions reduce ferroelectric properties, especially in samples treated in an ambient atmosphere (At amb). BZT10:2V ceramics sintered in a nitrogen atmosphere showed better dielectric behaviour at room temperature with a dielectric permittivity measured at a frequency of 10 kHz equal to 16800 with dielectric loss of 0.023. Piezoelectric force microscopy (PFM) images reveal improvement in the piezoelectric coefficient by sintering the sample under nitrogen atmosphere. Thus, BZT10:2V ceramics sintered under a nitrogen atmosphere can be useful for practical applications which include nonvolatile digital memories, spintronics and data-storage media
Novel approaches of nanoceria with magnetic, photoluminescent, and gas-sensing properties
The modification of CeO2 with rare-earth elements opens up a wide range of applications as biomedical devices using infrared emission as well as magnetic and gas-sensing devices, once the structural, morphological, photoluminescent, magnetic, electric, and gas-sensing properties of these systems are strongly correlated to quantum electronic transitions between rare-earth f-states among defective species. Quantitative phase analysis revealed that the nanopowders are free from secondary phases and crystallize in the fluorite-type cubic structure. Magnetic coercive field measurements on the powders indicate that the substitution of cerium with lanthanum (8 wt %), in a fluorite-type cubic structure, created oxygen vacancies and led to a decrease in the fraction of Ce species in the 3+ state, resulting in a stronger room-temperature ferromagnetic response along with high coercivity (160 Oe). In addition to the magnetic and photoluminescent behavior, a fast response time (5.5 s) was observed after CO exposure, indicating that the defective structure of ceria-based materials corresponds to the key of success in terms of applications using photoluminescent, magnetic, or electrical behaviors.Fil: Rocha, Leandro S.R.. Universidade Federal do SĂŁo Carlos; BrasilFil: Amoresi, Rafael A.C.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Moreno, Henrique. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Ramirez, Miguel A.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Ponce, Miguel Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales. Universidad Nacional de Mar del Plata. Facultad de IngenierĂa. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales; ArgentinaFil: Foschini, Cesar R.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Longo, Elson. Universidade Federal do SĂŁo Carlos; BrasilFil: SimĂ”es, Alexandre Z.. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi
Tailoring Bi2MoO6 by Eu3+ incorporation for enhanced photoluminescence emissions
Here, an experimental study is presented on the structural, electronic, and optical properties of Bi2-xMoO6:xEu3+ (x = 0, 0.5, 1.0, 2.0, and 4.0 mol%) materials, synthesized by means of the microwave-assisted solvothermal method using ethylene glycol as a solvent. Different characterization techniques (X-ray diffraction measurements with Rietveld refinements, Raman and ultravioletâvisible diffuse reflectance spectroscopy, field emission scanning electron microscopy, and photoluminescence emissions) have been employed to examine the structural and electronic properties, energy transfer and defect evolution which control the performance of the as-synthetized materials. Present findings provide deep insights into the substitution of Eu3+ cations in Bi2MoO6, with focus on their influence on process that dictate the superior optical properties.Funding for open access charge: CRUE-Universitat Jaume
Electrical properties of calcium doped BiFeO3 films on LaNiO3 coated Pt substrates
Pure and calcium-modified (CaxBi1-xFeO3, x = 0.0, 0.1, 0.2, 0.30) thin films were fabricated on Pt(111)/Ti/SiO2/Si substrates by the soft chemical method using LaNiO3 as the bottom electrode. Highly (200)-oriented BFO film was coherently grown on LNO at 500 °C. Ca-doped BiFeO3 films have a dense microstructure and rounded grains. The conventional problem of the leakage current for the highest doped film was reduced from 10-5 to 10-10 with remarkable improvement in the film/electrode interface, chemical homogeneity, crystallinity, and morphology of the BFO film. Enhanced ferroelectricity was observed at room temperature due to the bottom electrode. Fatigue-free films were grown on LaNiO3 bottom electrodes with no degradation after 1Ă1010 switching cycles at an applied voltage of 5 V with a frequency of 1 MHz. After several tests the capacitors retained 77% of its polarization upon a retention time of 104 s. Room temperature magnetic coercive field measurements indicate that the magnetic behaviour is influenced by the nature of the bottom electrode
Electrical transport mechanisms of Neodymium-doped rare-earth semiconductors
This study reports the electrical properties of Nd-doped cerium oxide (CeO2) films synthesized by microwave assisted hydrothermal using a two-point probe technique. Positron annihilation lifetime spectroscopy studies evidenced that, as the Nd content rises, a structural disorder occurs. This is caused by an increase in oxygen vacancies surrounded with Nd (defective clusters), with the mean lifetime components ranging between 290 and 300 ps. Particle size estimation showed values from 8.6 to 28.9 nm. Along with the increase of neodymium impurities, also the conductivity increases, due to the hopping conduction mechanism between defective species. This gives rise to a response time of only 6 s, turning these materials candidates to realize gas sensor devices. Ab initio investigations showed that the improved electric conduction is boosted mostly by the reduced Nd2+ than the Ce3+, where the oxygen vacancies play a fundamental role.Fil: Vaz, Isabela C. F.. Federal University of ItajubĂĄ; BrasilFil: Macchi, Carlos Eugenio. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Somoza, Alberto Horacio. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; ArgentinaFil: Rocha, Leandro S. R.. Universidade Federal do SĂŁo Carlos; BrasilFil: Longo, Elson. Universidade Federal do SĂŁo Carlos; BrasilFil: Cabral, Luis. Universidade Estadual de Campinas; BrasilFil: da Silva, Edison Z.. Universidade Estadual de Campinas; BrasilFil: SimĂ”es, Alexandre Zirpoli. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Zonta, Giulia. UniversitĂ di Ferrara; ItaliaFil: Malagu, Cesare. UniversitĂ di Ferrara; ItaliaFil: Desimone, Paula Mariela. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales. Universidad Nacional de Mar del Plata. Facultad de IngenierĂa. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales; ArgentinaFil: Ponce, Miguel Adolfo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales. Universidad Nacional de Mar del Plata. Facultad de IngenierĂa. Instituto de Investigaciones en Ciencia y TecnologĂa de Materiales; Argentina. Universidad Nacional de Mar del Plata; ArgentinaFil: Moura, Francisco. Federal University of ItajubĂĄ; Brasi
Estudo da formação de aderĂȘncias e da cicatrização de anastomoses colĂŽnicas em ratos com sepse peritoneal induzida
OBJETIVO: Avaliar os efeitos da sepse abdominal sobre a formação de aderĂȘncias e a cicatrização de anastomoses colĂŽnicas em ratos. MĂTODOS: 40 ratos distribuĂdos em dois grupos contendo 20 animais, para anastomose do cĂłlon esquerdo na presença (grupo S) ou
ausĂȘncia (grupo N) de indução de sepse por ligadura e punção do ceco (CLP). Cada grupo foi dividido em subgrupos para eutanĂĄsia no
terceiro (N3 e S3) ou sĂ©timo (N7 e S7) dia de pĂłs-operatĂłrio (DPO). Foi avaliada a quantidade de aderĂȘncias e removido um segmento
colĂŽnico contendo a anastomose para anĂĄlise histopatolĂłgica, força de ruptura, hidroxiprolina e conteĂșdo de colĂĄgeno tecidual. RESULTADOS: Os animais submetidos Ă CLP apresentaram maior quantidade de aderĂȘncias intra-abdominais tanto no 3° DPO
(p=0,00) quanto no 7° DPO (p=0,00). Tiveram menores valores de força de ruptura no 3° DPO (p=0,00), porém maiores valores no 7°
DPO (p=0,00). NĂŁo houve diferença na variação da concentração de hidroxiprolina, conteĂșdo de colĂĄgeno e histopatologia. CONCLUSĂES: A infecção peritoneal desencadeada por CLP aumentou a quantidade de aderĂȘncias intra-cavitĂĄrias. Houve diminuição da resistĂȘncia de anastomoses cĂłlicas no 3° DPO, com posterior aumento no 7° DPO, sem efeito sobre os outros parĂąmetros da cicatrização. ________________________________________________________________________________ ABSTRACTPURPOSE: To evaluate the effects of abdominal sepsis on adhesion formation and colon anastomosis healing in rats.
METHODS: Forty rats were distributed in two groups containing 20 rats each for left colon anastomosis in the presence (Group S) or
absence (Group N) of induced sepsis by cecal ligation and puncture. Each group was divided into subgroups for euthanasia on the third
(N3 and S3) or seventh (N7 or S7) post-operative day. The amount of adhesions was evaluated and a segment of the colon was removed
for histopathologic analysis, bursting strength assessment, hydroxyproline and the determination of tissue collagen.
RESULTS: The subjects which underwent cecal ligation and puncture presented a higher amount of intra-abdominal adherences in
both third (p=0,00) and seventh (p=0,00) post-operatory days. Smaller bursting strengths were found in the S3 subgroup, and greater
bursting strengths were found in the S7 subgroup. There was no difference in the variations on the concentrations of hydroxyproline,
tissue collagen and histopathology.
CONCLUSIONS: The peritoneal infection which was developed by cecal ligation and puncture raised the amount of intra-cavitary
adhesions. There was a decrease in the amount of colonic anastomosis on the third post-operatory day with a following raise on the
seventh without any effects on other healing parameters