Nitrogen diffusion in the Nb-1.0wt%Zr measured by mechanical spectroscopy

The scientific and technological development in the area of new materials contributed to several applications of niobium and its alloys in nuclear power plants as well as in aerospace, aeronautics, automobile and naval industries. This paper presents the interstitial diffusion coefficients of nitrogen in solid solution in the Nb-1.0wt%Zr alloy using internal friction measurements obtained by mechanical spectroscopy, which uses a torsion pendulum operating at an oscillation frequency between 1.0 Hz and 10.0 Hz. The temperature range varies from 300K to 700K, at a heating rate of 1 K/min and vacuum better than 2 x 10(-6) Torr. The results showed an increase of the interstitial diffusion coefficient of nitrogen that was correlated with configurational considerations for the octahedral interstitials.

Assessment of liquid disposal originated by uranium enrichment at Aramar Experimental Center São Paulo-Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of the accumulated energy by thermal stratification of liquid inside storage tanks with porous layers

A mathematical model was developed in order to study the behavior of thermal stratification of liquid in a typical storage tank with porous medium. The model employs a transient stream function-vorticity formulation to predict the development of stream function and temperature fields in a charging process. Parameters analyzed include Biot, Darcy, Reynolds and Richardson numbers, position, and the thickness of the porous medium. The results show the influence of these physical parameters that should be considered for a good design of storage tanks with thermal stratification.

Obtenção de diesel verde por craqueamento termocatalítico de óleo de buriti (Mauritia flexuosa L.) sobre materiais nanoestruturados do tipo LaSBA-15

In order to obtain a biofuel similar to mineral diesel, lanthanum-incorporated SBA- 15 nanostructured materials, LaSBA-15(pH), with different Si/La molar ratios (75, 50, 25), were synthesized in a two-steps hydrothermal procedure, with pH-adjusting of the synthesis gel at 6, and were used like catalytic solids in the buriti oil thermal catalytic cracking. These solids were characterized by X-ray fluorescence (XRF), powder X-ray diffraction (XRD), thermogravimetric analysis (TG/DTG), infrared spectroscopy (FTIR), nitrogen porosimetry and ethanol dehydration, aiming to active sites identify. Taken together, the analyses indicated that the synthesis method has employed to obtain materials highly ordered mesostructures with large average pore sizes and high surface area, besides suggested that the lanthanum was incorporated in the SBA-15 both into the framework as well as within the mesopores. Catalytic dehydration of ethanol over the LaSBA-15(pH) products has shown that they have weak Lewis acid and basic functionalities, indicative of the presence of lanthanum oxide in these samples, especially on the La75SBA-15(pH) sample, which has presented the highest selectivity to ethylene. The buriti oil thermal and thermal catalytic cracking, realized from the room temperature to 450 ºC in a simple distillation system, has allowed obtaining two liquid fractions, each consisting of two phases, one aqueous and another organic, organic liquid (OL). The OL obtained from first fractions has shown high acid index, even in the thermal catalytic process. One the other hand, OL coming from second ones, called green diesel (GD), have presented low acid index, particularly that one obtained from the thermal catalytic process realized over LaSBA-15(pH) samples. The acid sites presence in these samples, associated to their large average pore sizes and high surface areas, have allowed them, especially the La75SBA-15(pH), to present deoxygenating activity in the buriti oil thermal catalytic cracking, providing an oxygenates content reduction, particularly carboxylic acids, in the GD. Furthermore, the GD comes from the second liquid fraction obtained in the buriti oil thermal catalytic cracking over this latest solid sample has shown hydrocarbons composition and physic-chemical properties similar to that mineral diesel, beyond sulfur content low

Effects of temperature, sestonic algae features, and seston mineral content on cladocerans of a tropical lake

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

The Use of Response Surface Methodology in Optimization of Lactic Acid Production: Focus on Medium Supplementation, Temperature and pH Control

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

Response surface optimization of D(-)-lactic acid production by Lactobacillus SMI8 using corn steep liquor and yeast autolysate as an alternative nitrogen source

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

Friction losses in valves and fittings for liquid food products

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

The effect of chain length on the melting temperature and size of dialkyldimethylammonium bromide vesicles

Differential scanning calorimetry (DSc) and dynamic light scattering (DLS) were used to obtain the gel to liquid-crystalline phase transition temperature (T-m) and the apparent hydrodynamic radius (R-h) of spontaneously formed cationic vesicles of dialkyldimethylammonium bromide salts (CnH2n+1)(2)(CH3)(2)N+center dot Br-, with varying chain lengths. The preparation of cationic vesicles from aqueous solution of these surfactants, for n = 12, 14, 16 and 18 (DDAB, DTDAB, DHDAB and DODAB, respectively), requires the knowledge of the surfactant gel to liquid-crystalline phase transition temperature, or melting temperature (T-m) since below this temperature these surfactants are poorly or not soluble in water. That series of cationic surfactants has been widely investigated as vesicle-forming surfactants, although C-12 and C-18, DDAB and DODAB are by far the most investigated from this series. The dependence of T-m of these surfactants on the number n of carbons in the surfactant tails is reported. The T-m obtained by DSC increases non-linearly with n, and the vesicle apparent radius R-h is about the same for DHDAB and DODAB, but much smaller for DDAB. (c) 2006 Elsevier B.V.. All rights reserved.

Kinetic asymmetry in the gel-liquid crystalline state transitions of DDAB vesicles studied by differential scanning calorimetry

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

Liquid crystalline formulations containing modified surface TiO2 nanoparticles obtained by sol-gel process

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

Effect of Ionic Liquid on the Determination of Aromatic Amines as Contaminants in Hair Dyes by Liquid Chromatography Coupled to Electrochemical Detection

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

The importance of excretion by Chironomus larvae on the internal loads of nitrogen and phosphorus in a small eutrophic urban reservoir

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

Orchid in vitro growth as affected by nitrogen levels in the culture medium

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Small-angle X-ray scattering and nitrogen adsorption study of the nanoporosity elimination in TEOS sonohydrolysis-derived xerogels

Small-angle X-ray scattering (SAXS) and nitrogen adsorption techniques were used to study the temperature and time structural evolution of the nanoporosity in silica xerogels prepared from acid- and ultrasound-catalyzed hydrolysis of tetraetboxysilane (TEOS). Silica xerogels present a structure of nanopores of fully random shape, size, and distribution, which can be described by an exponential correlation function gamma(r) = exp (-r/a), where a is the correlation distance, as predicted by the Debye, Anderson, and Brumberger (DAB) model. The mean pore size was evaluated as about 1.25 nm from SAXS and about 1.9 nm from nitrogen adsorption. The nanopore elimination in TEOS sonohydrolysis-derived silica xerogels is readily accelerated at temperatures around 900 degrees C probably by the action of a viscous flow mechanism. The nanopore elimination process takes place in such a way that the pore volume fraction and the specific surface are reduced while the mean pore size remains constant. (c) 2005 WILEY-VCH Verlag GmbH S Co. KGaA, Weinheim.