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  • Author or Editor: M. Popescu x
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Thermal analysis coupled with the measurement of temperatures at which colour changes are observed in situ was used to test various inorganic pigments with the aim of introducing them into the compositions of thermo-indicating paints. Through a reversible or irreversible modification of the colour these can indicate an undesired increase in temperature of a fluid in a metallic enclosure. Three such pigments are described, which indicate temperatures of 110, 300 and 400°C. The paint contains the thermo-indicator pigment, soluble glass as binder and either ultrafine silica or silica gel, or a mixture of Na2SiF6 and finely-ground sand as hardener. Such paints are used for damage warning.

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Abstract  

In this paper we generalise the mathematical model which describes the stability conditions of the human body considered as a big cybernetic system that lives in the normal condition by feed-back. Starting by a linear approximation, we generalise the stability's conditions in the polynomial case of dependencies between trace elements determined in organs of the human body. We tested this model on traces of: Fe, Zn and Co. These elements were determined in breast tissues samples which have different diseases.

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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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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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Abstract  

A number of dibenzobicyclo[2.2.2]octane derivatives have been studied due to the interest of such compounds as ligands for coordination compounds with potential biological activity. Their thermal behaviour has been analyzed in order to find out more information about their fragmentation. A connection between the bridge substituents and the fragmentation process has been observed.

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Abstract  

This paper reports on the synthesis of various iron oxides by the IR laser processing of different iron salts. X-ray diffraction techniques were used to characterize the reaction products. Some differences in terms of crystallite size and isotropy between these oxides and those obtained from the same salt by thermal means are described and explained.

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