Influencia del tratamiento térmico en la cristalización y rugosidad de películas delgadas de LiNbO3 depositadas por el método Spin Coating

Lithium niobate (LiNbO3) thin films with 1/1 stoichiometry were prepared by a spin-coating from polymeric precursor method. The films deposited on silicon (100) substrates, were thermally treated from 400° to 600°C for 3 hours in order to study the influence of thermal treatment on the crystallinity, microstructure, grain size and roughness. X-ray diffraction (XRD) results showed that LiNbO3 phase crystallizes at low temperature (400°C). It was observed by scanning electron microscopy (SEM) that it is possible to obtain dense thin films at temperatures around 500°C. The atomic force microscopy (AFM) results showed that the grain size and roughness are strongly influenced by the annealing temperature.

Influence of thermal treatments in the corrosion behaviour of HVOF Cr 3C2-NiCr coatings

Thermal spray coatings as Cr3C2-NiCr obtained by high velocity oxy-fuel spraying (HVOF) are mainly applied due to their behaviour against aggressive erosive-abrasive and corrosive atmospheres and their thermal stability at high temperatures [1]. In order to increase the corrosion protection that it offers to the substrate trying to close the interconnected pores, it is possible to apply a thermal treatment with the gun during the spraying of the coating. This treatment could be applied in different ways. One of these ways consists of spraying only a few layers of coating followed by thermal treatment and finally the spray of the rest of layers. This thermal treatment on spraying is studied related to the corrosion properties of the system. The study comprises the electrochemical characterisation of the system by open circuit potential (OC), polarisation resistance (Rp), cyclic voltammetry (CV) and impedance spectroscopy measurements (EIS). Optical and scanning electron microscopy characterisation (OM and SEM) of the top and cross-section of the system has been used in order to justify the electrochemical results.

Photoluminescence in amorphous (PbLa)TiO3 thin films deposited on different substrates

Pb1-xLaxTiO3 thin films, (X=0.0; 13 and 0.27mol%) were prepared by the polymeric precursor method. Thin films were deposited on Pt/Ti/SiO2/Si(111), Si(100) and glass substrates by spin coating, and annealed in the 200-300°C range in an O2 atmosphere. X-ray diffraction, scanning electron microscopy and atomic force microscopy were used for the microstructural characterization of the thin films. Photoluminescence (PL) at room temperature has been observed in thin films of (PbLa)TiO3. The films deposited on Pt/Ti/SiO2/Si substrates present PL intensity greater than those deposited on glass and silicon substrates. The intensity of PL in these thin films was found to be dependent on the thermal treatment and lanthanum molar concentration. © 2002 Elsevier Science B.V. All rights reserved.

Effect of thermal treatments on tensile strength of commercially cast pure titanium and Ti-6Al-4V alloys

Heating titanium structures is assumed to relieve tensions induced by the casting process as well as possibly optimizing some mechanical properties. The aim of this investigation was to evaluate the effect of thermal treatments on tensile strength of commercially pure titanium (CP Ti) and Ti-6Al-4V alloy. Thirty dumbbell rods, with diameters of 3.0 mm at the central segment and lengths of 42 mm, were cast for each metal using the Rematitan System. CP Ti and Ti-6Al-4V specimens were randomly divided into three groups of ten: a control group that received no thermal treatment and two test groups. One (T1) was heated at 750°C for 2 h and the other (T2) was annealed at 955°C for 1 h and aged at 620°C for 2 h. Tensile strength was measured with a universal testing machine (MTS model 810). Tensile strength means and standard deviations were statistically compared using a Kruskal-Wallis test at a α = 0.05 significance level. No statistically significant differences in tensile strength were observed among CP Ti groups. For the Ti-6Al-4V alloy, the control and T1 groups revealed statistically higher tensile strengths when compared to the T2 group, with no significant difference between the control and T1 groups. © 2005 Springer Science + Business Media, Inc.

Effect of milk treatment on acidification, physicochemical characteristics, and probiotic cell counts in low fat yogurt

The effect of milk treatment (heat, high hydrostatic pressure - HHP, or combined heat and HHP) on acidification, physicochemical characteristics, and probiotic cell counts in low fat yogurt was studied. All samples were analyzed for fermentation time, pH, titratable acidity, total solids, water-holding capacity, syneresis, Hunter L*, a*, and b* values, Streptococcus thermophilus, Lactobacillus delbrueckii ssp bulgaricus, L. acidophilus, and Bifidobacterium longum. The application of HHP combined with thermal treatment resulted in yogurt gels with attractive physicochemical characteristics and high water-holding capacity. In addition to this, the milk treatment did not affect the probiotic bacteria growth. The balance of strains in the starter culture and level of inoculation influenced the yogurt fermentation and properties. The use of combined heat and HHP to treat milk before yogurt fermentation could be an alternative process for obtaining high quality, additive-free healthy products.

Infrared to visible up-conversion emission in Er3+/Yb 3+ codoped fluoro-phosphate glass-ceramics

Erbium Er3+ and ytterbium Yb3+ codoped fluoro-phosphate glasses belonging to the system NaPO3-YF 3-BaF2-CaF2 have been prepared by the classical melt-quenching technique. Glasses containing up to 10 wt% of erbium and ytterbium fluorides have been obtained and characterized using differential scanning calorimetry (DSC) and UV-visible and near-infrared spectroscopy. Transparent and homogeneous glass-ceramics have been then reproducibly synthetized by appropriate heat treatment above glass transition temperature of a selected parent glass. Structural investigations of the crystallization performed through X-ray diffractometry (XRD) and scanning electron microscopy (SEM) have evidenced the formation of fluorite-type cubic crystals based during the devitrification process. Finally, infrared to visible up-conversion emission upon excitation at 975 nm has been studied on the Er3+ and Yb 3+ codoped glass-ceramics as a function of thermal treatment time. A large enhancement of intensity of the up-conversion emissions-about 150 times- has been observed in the glass-ceramics if compared to the parent glass one, suggesting an incorporation of the rare-earth ions (REI) into the crystalline phase. © 2012 The American Ceramic Society.

Avaliação do tempo e métodos de aquecimento de toras de Eucalyptus grandis Hill ex-Maiden e sua influência no rendimento em laminação e na qualidade das lâminas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos do ultrassom de alta intensidade sob pressão na redução de Listeria monocytogenes em extrato de carne bovina

Pós-graduação em Engenharia e Ciência de Alimentos - IBILCE

Espectroscopia de impedância em vidros 22Na2O·8CaO·65SiO2·5MO2 (M = Si, Ti, Ge, Zr, Sn, Ce) sem e com troca iônica Ag+ Na+

Pós-graduação em Física - IGCE

Estudo de filmes supercondutores para aplicações em dispositivos eletrônicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação e caracterização de semicondutores de PbS e 'B IND. I 'IND. 2' 'S IND. 3' obtidos pelo método de deposição em banho químico

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

Recobrimentos cerâmicos bioativos pelo processo sol-gel sobre Ti c.p. modificado por laser empregados em implantes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação e caracterização de filmes finos Sr1-xMexTiO3(Me=Fe, Ni)

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Influência dos elementos de liga no encruamento proveniente do processo de aplainamento nos aços hadfield

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da formação de espumas cerâmicas à base de zircônio a partir do processo sol-gel

Pós-graduação em Química - IQ