Search Results
Abstract
An Al–4.4Cu–0.5Mg–0.9Si–0.8Mn alloy (IADS 2014 grade) in the solution annealed and peak aged condition was exposed at 170°C for relatively long times (up to about 1800 h) in order to check the stability of the alloy. The investigated aging temperature was in the frame of a research on the long-term mechanical behaviour of such alloy. Microstructure evolution was monitored via calorimetric analyses, metallographic inspections and hardness measurements. Further, X-ray analyses were carried out on selected samples. The attention was focused on differential scanning calorimetry performed at different scanning rates, with the aim of evaluating the kinetics of the precipitation phenomena. Notwithstanding the wide industrial diffusion of this alloy, literature survey showed that there is not a consensus view on the precipitation sequences and on calorimetric peak identification. The present results show the progressive evolution of calorimetric peaks, corresponding to that of strengthening particles towards more stable phases, proved by the disappearance of exothermic peaks. Activation energy from Kissinger kinetic analysis in the case of aged samples provided scattered values that could be reasonably attributed to an overlapping of transformation peaks. Moreover, in these samples transformations partially occurred before DSC scans, providing non-constant transformation fraction at signal peak temperatures and resulting in different activation energies.
Abstract
The vertical distribution of K, Rb, Cs, Ca, Sr, Ba, Fe, Cr, Co, Ni, Zn, Sc, Zr, Sb, Se and As was studied by means of instrumental neutron activation analysis in four sediment cores collected from the eastern shelf of tectonically active Baja California peninsula accompanied by 210Pb age-dating. 210Pb analysis was performed by extraction chromatography with measuring the ingrowing daughter 210Bi radioactivity by liquid-scintillation spectrometry. It was found that concentration variations of Se, As, Sb, Zr and Zn are probably controlled by the intensity and composition of the material supplied from the drainage basin constituted by volcanic and sedimentary rocks.
Abstract
In order to know the normal distribution of trace elements is rats, in terms of age, we have determined the elemental composition of different organs and body tissues by neutron activation analysis following an animal experiment during which the rats raised outside of any kind of pollution, were fed with a defined diet. The values observed for Co, Zn, Mn, Se, Fe, Cs, Rb, Hg, Cd in heart, body muscles, liver, kidney and testis are represented in table and figures. Except for renal accumulation of Hg and Cd, the more interesting fact revealed in this work, in the accumulation of Fe in body muscles and testis.
Summary
Ruthenium-106 and 137Cs have been separated from thermal-neutron irradiated UO3 targets aged for ~2.5 years by distillation and surface interactions in nitrate media of controlled chemical composition. After digestion of the aged targets with their aluminum wrapper in 2M NaOH solution, nitric acid was added to complete dissolution of the formed residue. The prepared fission product solution was separated from 129I and 91.8% 106Ru by sequential distillation from 20% and 40% HNO3 solutions containing H2O2 and KMnO4, as oxidants, and by boiling for 4 and 2.5 hours, respectively. The recovery yield of 106Ru collected in 0.1M NaOH solution was ~68.2% with a radionuclidic purity of ³99.99%. Thereafter, the fission product solution was brought to pH 9.5 by addition of NaOH solution to precipitate Al(OH)3, MnO2, and Na2U2O7 which selectively retained the remaining fission products leaving, mainly, 137Cs in the supernatant solution. The recovery yield of 137Cs was ≥97.3% with ~99.75% radionuclidic purity. The gamma-ray emitter contaminants which could be detected and identified in the recovered 137Cs solution, were ~0.25% 134Cs and ~1.4 . 10-3% 152,155Eu.
The main objective of this paper is to discuss the relationship between physical state, fracture mechanism, and texture for low moisture cereal-based foods. Experiments were also carried out to get a better understanding of the role of water. At room temperature, extruded bread and white bread (previously) dehydrated, then rehydrated in atmospheres with controlled humidities) exhibited a brittle behavior up to around 9% moisture. At 13.7% moisture, they were ductile. A significant loss in the crispness of extruded bread was observed between 8.5 and 10% moisture. The glass transition temperature (T g) was measured, using dynamic mechanical thermal analysis (DMTA), for samples with up to 40% moisture. The resultingT g curve showed that the important changes in fracture mechanisms and crispness occurred while the samples were still in the glassy state. The viscoelastic behavior of both extruded and white breads suggested that a secondary relaxation occurred around 10‡C. Another event was observed around 70‡C for low moisture sample, using DMTA. This event was attributed to disruption of low energy interactions.
Metastable effects on martensitic transformation in SMA
Part II. The grain growth effects in Cu-Al-Be alloy
Abstract
The efficiency of shape memory alloy (SMA) as damper and/or standard actuator is truly enhanced when the material can be cycled without any relevant accumulation of the permanent deformation (i.e. under 0.5% for several hundreds of cycles). The particular properties of the CuAlBe alloy permit relevant grain growth with reasonable reduction of mechanical properties (from 300–350 to 250–300 MPa at fracture). Samples prepared with an appropriate heat thermal treatment (HTT) and relevant mean diameter of grain avoids accumulative deformation for series of cycles (near 500) up to 3.5% of deformation. The analysis of different wires of CuAlBe alloy shows, in the first part of HTT, a proportionality between the grain surface and the time at 1123 K. In the last part of the HTT the grain growth shows an increased complexity related with interactions between the grain boundaries and the external surface of the samples.
A Szigetköz és a Mosoni-síkság eltemetett humuszos réteg folttérképének újabb pontosított változatát készítettük el 3 m mélységig terjedő fúrások segítségével. A jellemzőnek ítélt szelvények eltemetett humuszos rétegei mintáiból a radiokarbon kor vizsgálatokat az MTA ATOMKI Környezetanalitikai Laboratóriuma végezte. Több mint 2000 szelvény vizsgálata alapján megállapítottuk, hogy a szelvények kb. 25%-ában található eltemetett humuszos réteg, amelyeknek kevesebb, mint 20%-a van a felszín közelében. Azok a szelvények, amelyekben egynél több eltemetett humuszos réteget találunk a Dunaremetétől Lébényen át Győrzámolyig vezető félkör mentén helyezkednek el, délre eltávolodva a Mosoni-Duna jelenlegi vonalától. Ebben a sávban a talajképződést biztosító nyugalmi szakaszok után periodikusan visszatérő elöntések történtek. A félkör által határolt területen belül ilyen ciklikusság hatása nem volt megfigyelhető. A Duna és a Mosoni-Duna közelében az eltemetett humuszos rétegek kora 1–2 ezer év, távolabb a legrégebbi mért radiokarbon kor 4 ezer év körül volt. Ez közel azonos a Győr-tatai teraszvidéken egy lejtőhordalék talaj mélyen eltemetett humuszos rétegében mért korral. A Szigetközben a több eltemetett humuszos réteget tartalmazó zónában a periodikus nagy hordalékszállítási ciklusok 500–1000 évente ismétlődtek. A terület déli részén, Lébény környékén a viszonylag vékony, de ciklikusan megjelenő hordalékszállítások a korábbi 7–10 ezer éves hansági tőzegre rakódtak le. A vizsgálati adatok segíthetnek a terület földtani és emberi településtörténeti kutatásában is.
Abstract
SuperLig® 644 resin was exposed to simulated Hanford waste solution under air atmosphere or in protated inert environment, and in 0.5M HNO3 solution for 15 days and 45 °C. The degradation was evaluated by cesium batch distribution measurement.
