Irene Calliari

Cerium-based conversion layers on aluminum alloys

Abstract Mixed layers of Al and Ce oxides have been obtained in conversion coatings on two aluminum alloys (AA6061 and AA2618). The microstructure and the chemical composition of the protective films have been examined by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The corrosion resistance in NaCl solution was investigated and a comparison with a traditional chromate conversion coating on the same alloys is given. The coatings obtained by immersion in boiling solution of Ce(III) salts cover uniformly the alloys surface with a protective layer, whereas the H 2 O 2 –cerium conversion coating process produces a thick, but cracked layer with “dry-mud” morphology, which preferentially covers the intermetallic particles on the samples surface. The boiled cerium conversion coating treatments are as effective in corrosion resistance as the traditional chromating process, but the interest for industrial purposes is limited because of long application times. The H 2 O 2 –cerium conversion coating process produces effective corrosion resistance layers, thinner than the ones obtained by traditional processing, but very interesting for industrial applications due to the limited environmental impact.

Accuracy of Bioelectrical Impedance Analysis in Estimation of Extracellular Space in Healthy Subjects and in Fluid Retention States

Bioelectrical impedance analysis (BIA) is a noninvasive method recently introduced for body fluid evaluation in healthy subjects. The purpose of this paper is to verify the reliability of bioelectrical measurements in extracellular water (ECW) prediction in healthy subjects and in fluid retention states. We studied 40 subjects (19 males and 21 females) aged 21-81 years; 22 were healthy subjects, 12 were affected by chronic heart failure, and 6 by chronic renal failure. In all subjects resistance (R) and reactance (Xc) at 1 and 50 kHz corrected for height were compared with ECW measured by the bromide dilution method. Our results suggested a different behavior of the current in fluid-retention states with respect to healthy subjects. ECW was best predicted by resistance at 1 kHz corrected for height, group (considered as dummy variable), weight and gender (R2 = 0.89, p < 0.001, SEE = 1.7 liters). The bioelectrical impedance analysis at 50 kHz explained the 89% of ECW variability when resistance and reactance corrected for height are considered with gender group and weight (R2 = 0.89, p < 0.001, SEE = 1.7 liters). In conclusion, the bioelectrical method at 1 kHz can be considered sufficiently accurate in ECW prediction in healthy subjects and in fluid retention states. Also, the bioelectrical impedance analysis at 50 kHz is useful for predicting ECW, but his role must be further investigated.

Changes in Fluid Compartments and Body Composition in Obese Women after Weight Loss Induced by Gastric Banding

Background/Aims: Surgical gastric banding procedures induce considerable and rapid weight losses in obese subjects. Nevertheless changes in lean mass and body fluids following these surgical treatments are not well known. Methods: We studied 6 obese women aged 38–42 years, before, and 8 and 24 weeks after laparoscopic adjustable silicone gastric banding (LAP-BANDTM). Fat-free mass (FFM) and fat mass (FM) were investigated using dual energy X-ray absorptiometry (DEXA), while total body water (TBW) and extracellular water (ECW) were assessed by dilution methods. Results: The subjects showed a total weight loss of 16% of initial weight; the weight reduction was greater during the first 8 weeks. FFM decrease after 24 weeks was very limited and represented only 14% of the weight loss. The mean FFM changes per week were similar in the two periods of observation (0–8 and 8–24 weeks after LAP-BAND). TBW showed a global reduction of 2.2 ± 1.8 litres mainly due to a decline in intracellular water (ICW), while ECW remained constant during weight loss. As a consequence, the ECW/ICW ratio increased after LAP-BAND. Conclusion: LAP-BAND seems to achieve satisfactory weight losses while sparing FFM and causing only mild body fluid alterations.

Pd-based alloy nanoclusters in ion-implanted silica: Formation and stability under thermal annealing

Abstract In this work we report on the formation and stability under thermal annealing of Pd–Cu and Pd–Ag alloy nanoclusters obtained by sequential ion implantation in silica. The role of the annealing atmosphere on the alloy cluster formation and stability is investigated. A comparison is made with similar alloy-based systems obtained by sequential ion implantation in silica of Au–Ag or Au–Cu followed by annealing under similar conditions, in order to evidence the peculiar effect of the various metals in controlling the alloy evolution and/or decomposition.

Investigation of secondary phase effect on 2205 DSS fracture toughness

Abstract The fracture toughness properties of duplex stainless steels (DSS) are strongly reduced by intermetallic phases, precipitating at 600–1000°C. In this investigation, the embrittlement effect induced by a low content of these phases has been studied in a 2205 DSS, by means of instrumented Charpy V impact testing. Different contents of intermetallic phases have been produced by isothermal treatments at 800–950°C. The microstructure has been analysed by scanning electron microscope/backscattered electron images. The impact test results, the examination of the fracture surfaces and of the cross-sections close to the notch root allows us to elucidate the role of secondary phases contents in reducing impact fracture toughness. When the quantity of secondary phases is <0·5%, these precipitates are rare and insignificant, reducing the absorbed energy by facilitating a ductile fracture. When the content is >1%, the fracture is completely brittle. The plastic deformation at the notch root and in the resisting section provokes a secondary phase breakage with a high density microcrack formation, inducing an easy nucleation and propagation of the final fracture crack. When the content of secondary phases is between 0·5 and 1%, fracture is mixed. Both the sigma σ and chi χ phases have been found to be responsible for the embrittling of the 2205 DSS, and fracture toughness mainly depends on their density and dimension.

Microstructural and compositional characterization of Roman coins

Scanning electron microscopy (SEM) with energy-dispersive microanalysis (EDS) and energy-dispersive x-ray spectrometry (EDXRS) were used to investigate the composition and microstructure of some Roman coins from the Julius Caesar and Octavianus periods. The samples were Cu-based alloys with different surface conditions. The microstructural examination supported the chemical analysis data, explaining compositional changes from the surface to the bulk. Compositional data confirm the numismatic interpretation: coins issued by Julius Caesar were orichalcum (Cu-Zn alloy) coins whereas asses issued by Octavianus were Cu-Pb-Sn coins.

Trace elements in human scalp hair and soil in Irian Jaya.

Pb, Cd, and Ni contents were determined in the scalp hair of the Asmat of Irian Jaya (Indonesian New Guinea) on 35 adult subjects. These data are presented together with those of Al, Ca, Ti, Fe, Cu, Zn and Sr, which were determined in previous research on the same group. Hair samples were analyzed by EDXRS and ICP. Trace elements were also determined in 12 soil samples from the same area by EDXRS (Al, Si, K, Ca, Fe) and ICP (Cu, Sr, Ti), and by AAS (Cd, Ni, Pb). When hair element levels are compared and discussed with those of other New Guinea populations, acculturated and nonacculturated tropical groups, populations from Western countries and from polluted areas, and “recommended levels” in the literature, they greatly exceed Western levels and generally fit those of other New Guinea populations, stressing the importance of common environment, subsistence, and behavior. The results of soil analyses are consistent with the presence of those elements in hair, and their quantitative distribution follows a common trend. Metal mobility in soil, patterns of absorption, and transfer from soil to plants and to humans are considered here.

Metal determination by EDXRF in lichens. A contribution to pollutants monitoring.

Samples ofEvernia prunastri, collected in a mountainous zone, were exposed in urban and highly industrialized areas in order to monitor the atmospheric pollution. Amounts of Cr, Mn, Fe, Ni, Cu, Zn, and Pb were determined by EDXRF spectrometry in secondary target excitation mode and in the thin film approach. An increase in metal concentrations was noted on all sites with time exposition increases, but the highest final amounts were observed on those thalli mounted near a steel works. The washing procedure influenced the concentration of all the elements as previously verified onPseudevernia furfuracea.

Microstructural evolution of Udimet 720 superalloy

The microstructural evolution of the nickel-base superalloy Udimet 720 (Special Metals Corp., New Hartford, NY) aged at 850 °C for 1000 to 2000 h is presented. After aging, the γ′ precipitates change from cubic to globular morphology. Secondary γ′ particles and topologically close-packed phases were not found. The γ′ mean diameter increases with aging times, following the Lifshitz-Wagner model. The experimented aging times have no strong effects on mechanical properties of Udimet 720.

Roman bricks from the Lagoon of Venice: a chemical characterization with methods of multivariate analysis

From 18 archaeological sites of the Lagoon of Venice 75 bricks belonging to Roman and medieval building levels have been analysed. Chemical composition and geometric measures allow the characterization of a group of 24 Roman bricks of Imperial age. The group formed by means of fuzzy c-means cluster analysis applied on chemical data have been tested by principal component analysis and finally subjected to discriminant analysis to estimate the relative weights of original variables and classify new elements. Correlations among the data of the major chemical elements confirm the reliability of the complex of chemical data. The aim of this research was to obtain a chemical characterization of Roman bricks (and later, of the medieval ones) coming from the lagoon of Venice thus making it possible: 1) to recognize the age of a brick by means of its chemical analysis; 2) to date the layers of archaeological excavations or the ground where there are medieval building foundations by means of membership bricks; 3) to calculate the rate of local ground lowering in the elapsed years by the difference in level from one layer to another; 4) to estimate local rates of land subsidence by comparison with mean values already known.