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  • Author or Editor: V. Popescu x
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Abstract  

In order to evidence the ligand influence on the thermal stability for Co(II) complex combinations, we have synthesized five complex combinations of this metal with Schiff bases obtained by condensation of ethylenediamine with acetylacetone and benzoylacetone; phenylenediamine with benzoylacetone and also anthranilic acid with benzaldehyde.

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Thermal analysis methods and X-ray diffractometry provided data on and permitted practical use of the eutectic mixture between Na2O·2SiO2 and SiO2, which melts at 790°C. Based on this, water glass was used as a binder to obtain artificial cluster granules, ceramically hardened by heating at 800°C. The process of water glass hardening in the presence of hardening reagents such as Na2SiF6, NH4Cl, silica gel and ultra-fine silica was studied by thermal analysis. In the first stage, gelification of the SiO2 sol takes place by neutralization of the NaOH deflocculant, while the second stage involves tridimensional cross-linking by polycondensation, promoted by powders rich in SiO2.

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Thermal analysis up to 1550 °C on natural and synthetic materials containing CaSO4 revealed the temperature ranges of dehydration, impurity content decomposition and CaSO4 decomposition. CaSO4 decomposition starts above 1200 °C and proceeds in several steps, depending on the CaO content. CaSO4 forms several eutectic compositions with CaO (at 1340, 1390, 1410 and 1450 °C), each decomposition step being preceded by the formation and fusion of a eutectic composition, the decomposition taking place in the melt.

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Abstract  

The thermal analysis methods (TG, DTG and DTA) were used for the investigation of the thermal degradation of some recent manufactured tanned leathers, leathers that are supports of cultural or historical objects (leather from book covers (XVII-XIX centuries); leather from an Austrian belt (Franz Joseph period), Cordoba leather (XVII century), lining leathers), recent and patrimonial parchments and recent extracted collagen (sorts of collagen obtained from bovine leather at different pH-values, bovine collagen with different hydration degree). At progressive heating, all investigated materials exhibit two main successive processes, associated with the dehydration and thermo-oxidative degradation. Each analyzed material has a characteristic thermal analysis curve (TG, DTG and DTA) that can be considered a material 'fingerprint'. This result suggests the use of the thermal analysis methods to identify of leathers from which the patrimonial objects are manufactured. The rate of thermo-oxidation of recent manufactured tanned leathers is substantially higher than the rate of the same process corresponding to naturally aged leathers that exhibit values of the thermo-oxidation rate appropriate to those obtained for parchments and collagens. The rate of thermo-oxidation of leather can thus be used as a criterion to distinguish between recent manufactured leather and patrimonial one.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: F. Bunuş, V. Domocoş, R. Bulâceanu, P. Dumitrescu, and G. Popescu

Abstract  

In order to determine uranium from raw phosphoric acid solutions, resulted by the sulphuric acid attack of phosphate rocks and the strip solutions of the solvent extraction process for uranium recovery, two classes of analytical methods were established: one for low uranium content in phosphoric acid, and the other for higher uranium concentration in the same medium. The study was based on specific methods, therefore interference probability with other impurities in phosphoric acid medium is low. In the first class, X-ray fluorescence and spectrophotocolorimetric methods were used. X-ray fluorescence was applied on direct raw phosphoric acid solution and raffinate. The last one was associated with solvent extraction [di-(2-ethylhexyl) phosphate + triocylphosphine oxide] on the U(IV)-Arsenazo III complex in strip. The methods of the second class, were used for strip uranium concentrated solutions: X-ray fluorescence isotopic dilution and mass spectrometry, spectrophotocolorimetry and activation analysis associated with gamma-spectrometry. Here spectrophotocolorimetry involves two methods. The first one is based on the U(IV)-Arsenazo III complex and the other on direct U(IV)—phosphoric acid solutions measurements. A good agreement was obtained in each case for all comparative measurements involving various methods.

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Attenuation specific from Vrancea intermediate-depth focus toward SE is revised at length in order to re-evaluate the seismic hazard at the nuclear power plant (NPP) Cernavoda. To this aim, we took into consideration all the strong motion data available for the region and test a large range of relationship types. Since the instrumental data are limited as magnitude and  depth intervals, the extrapolation based on the attenuation laws deduced from these data to great magnitudes is very instable and must be carefully considered. The extrapolation outside the characteristic domain of the available database leads to large deviations, especially at large magnitudes and for the relations which contain the depth as independent parameter.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: V. Morozov, N. Morozova, N. Lebedev, D. Filosovof, T. Bădică, Gh. Căta-Danil, D. Deleanu, D. Ghiţă, S. Pascu, and I. Popescu

Abstract  

It is shown for the first time that the ASCSTS technique we have introduced several years ago for lifetime measurements can be also used for measuring low level activities. A good example with practical relevance in this respect is 90Sr isotope. In order to apply this technique the radioactive isotope must have an isomeric state with a lifetime spanning the ns–μs range. This method is adequate for measuring weak activities with high detection efficiency in a geometry close to 4π. It is experimentally demonstrated that ASCSTS method is a reliable, high efficiency technique for measuring absolute radioactivity in the long radioactive chains.

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