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Summary  

Liquid scintillation counting of the alpha-radionuclides after pre-concentration by cation-exchange represents a simple and robust method for the determination of total alpha-radioactivity in seawater. The total efficiency and the minimum detectable activity were calculated to be 95% and 30 mBq, respectively, for a liter sample and 1000-minute measuring time. The method has been applied successfully for the determination of alpha-radioactivity in seawater from five different coastal areas in Cyprus. The average alpha-radioactivity and uranium concentration were found to be 124±8 mBq . l-1 and 3.2±0.2 mg . l-1, respectively.

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Abstract  

A data acquisition system and the SAD2 software, that provide characteristic cooling curves, in combination with microstructure analysis were used to study precipitates formation in the AA380.0 aluminium alloys modified by adding extra magnesium. The samples were solidified with distinct cooling rates caused by carrying out the solidification in shell and permanent molds. The mathematics processing of the cooling curves in agreement with the microstructure analysis have confirmed the remarkable presence of both the Al–Si dendrite network and the Mg2Si interdendritic phase in the alloys with the addition of extra magnesium.

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Abstract

Mixed LaREO3 (RE ≡ Dy, Ho, Er, Tm, Yb, Lu) and NdGdO3 oxides were prepared by thermal decomposition of the corresponding co-precipitated mixed oxalates. The decomposition of La/RE and Nd/Gd oxalates was studied by means of differential thermal analysis and thermogravimetric (DTA-TG) measurements; in particular the last step, consisting of the loss of a CO2 molecule from the corresponding oxycarbonate, has been thoroughly investigated, as it is particularly interesting for the study of the formation temperature of mixed rare earth oxides. After the release of CO2, the oxides crystallize in a distorted perovskitic cell or one of the structures typical of rare earth sesquioxides, depending on the cationic size difference and on the average cationic radius. The mixed rare earth oxycarbonate decomposition has been studied in comparison to the decomposition of single rare earth oxycarbonates. A trend of the mixed oxides formation temperature as a function both of the average cationic size and of the cationic sizes difference has been observed and compared to the behaviour of single rare earth oxides.

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Abstract  

The aim of the present work is to study the thermal decomposition of the mixed oxalates (Ce1–xGdx)2(C2O4)3 nH2O. The mechanisms of decomposition of Ce and Gd oxalate are different, and mixed oxalates behave in an intermediate way. Their dehydration stages are more similar to those of Gd oxalate, as not all the molecules of water are equivalent like the cerium oxalate. The decomposition leads to (Ce1–xGdx)O2–x/2. For x close to 0 or to 1 two solid solutions exist, while for the central composition, the presence of a biphasic region can not be excluded.

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In food science, colour is a fundamental property for the evaluation of freshness, quality and conformity. One of the most important attributes indicating sweet cherry freshness is stem colour and shape. Fruit post-harvest cool storage retards respiration and colour ripening changes. The common technology of refrigeration is based on active cooling determining high evapotranspiration for the passage of air over the products surface. An innovative preservation system, such as the Passive Refrigeration System (PRS™), could guarantee perfect shelf-life preservation maintaining optimal temperature and relative humidity close to 100%, minimizing colour changes in medium-long storage range. There is the need to numerically quantify cherry stem thickness and colour changes to compare fruit postharvest conditions under the two systems. The use of the Thin-Plate Spline 3D warping (TPS3D) in the 3-dimensional-RGB colour space allowed an efficient colour calibration. Sweet cherry stem images belonging to the two different storage systems (active and passive refrigeration) were acquired before and after 7 days to preservation through a professional high resolution scanner. Thickness and colour (after calibration) were measured. Results indicate, in terms of sweet cherry quality of preservation, that the ones preserved in passive refrigerator after 7 days appears similar to the fruits at the beginning of the experiment.

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Abstract  

Several (Gd1−xNdx)2[C2O4]3·nH2O samples (0≤x≤1) were prepared by a coprecipitation method: the precipitation is quantitative and all the samples are homogeneous in stoichiometry. XRD analyses have shown that a complete solid solution is formed over the whole range of compositions. The dried Gd rich oxalates have initially a low water content which gradually increases with the Nd content. All the oxalates decompose in O2 around 700°C either into a single mixed oxide or in a mixture of oxides through several steps, which can be ascribed to the loss of water and CO2.

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Summary  

Trace elements were determined in the surface waters of tributaries of the Sepetiba Bay, Brazil (Piraquê, Itá, São Francisco, Guarda, Guandu Mirim, Vala do Sangue and Engenho Novo rivers) by total reflection X-ray fluorescence using synchrotron radiation (SRTXRF). Eighteen trace elements could be determined in the dissolved and the suspended particulate phases: Al, Si, P, S, Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr and Pb. The elemental concentration values were compared to the values recommended by the Brazilian legislation.

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Journal of Thermal Analysis and Calorimetry
Authors:
C. Costa
,
S. Crispim
,
S. Lima
,
C. Paskocimas
,
E. Longo
,
V. Fernandes
,
A. Araújo
, and
I. Santos

Abstract  

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Journal of Thermal Analysis and Calorimetry
Authors:
C. Xavier
,
C. Costa
,
S. Crispim
,
M. Bernardi
,
M. Maurera
,
M. Conceiçăo
,
E. Longo
, and
A. Souza

Abstract  

The pigments used in ceramic applications are of nature predominantly inorganic and they should be thermally stable, insoluble in glazing, resistant to the chemical and physical agents' attacks. This work aimed at the synthesis by the polymeric precursor method of ZrO2-based inorganic pigments, doped with Fe, Ni, Co, Cr and Cu cations. The fired pigments were characterized by thermogravimetry (TG), differential thermal analysis (DTA) and X-ray diffraction (XRD). Among the metals used to zirconium-doping, the best result was achieved with the cations Cu, which presented the monophase pigment, even as 20 mol% of dopant. Up to the temperature of 1000C the pigments presented a good thermal stability.

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Summary A thermal study was performed on the RuSr2GdCu2O8 (Ru-1212) magnetic superconductor phase to investigate the effect of the annealing treatments in flowing O2 on the stability limit of the phase and on its structural, magnetic and transport properties. DTA-TG measurements were utilized to determine the decomposition process and the dependence of the decomposition temperature on the annealing atmosphere. The decomposition of the Ru-1212 phase was found sensitive to the oxygen partial pressure and increases with PO2 and the annealing time. The annealing treatments exert a depressing effect on the strength of the magnetic interaction, an enhancement on the superconductive properties and the vanishing of the magnetostriction. A decomposition reaction of Ru-1212 phase was proposed and discussed.

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