The capacity of metallic ions to form complexes depends on the electric charge and its mass and on the ligands nature. In this study we followed the coordination capacity of the uranyl ion (UO2(2+)) with a series of Schiff bases. The Schiff bases have been obtained through the condensation of some salicylic aldehyde derivates with a series of diamines. As a result of the reaction between these substances and the uranyl ions the mono-, bi-, or poly-nuclear complexes, depend on the nature of the ligands. The forming of the complexes is highlighted through ultraviolet-visible, Fourier transform infrared (IR), and fluorescence spectroscopy. In the IR studies the forming of the complexes is highlighted by the apparition of a new band at approximately 920 cm(-1,) characteristic to the O=U=O group. Also modifications of valence vibrations appear characteristic to the azomethinic groups, nu(C=N,) and the apparition of some new bands in the 300-500 cm(-1) domain, characteristic to forming of some new bonds U-O and U-N. The formed complexes represent tetragonal bipyramidal geometry. The study of the capacity coordination of uranyl ions is important in determining, dozing and precipitin of the ions in diverse used waters.
Paintings signed by Nicolae Grigorescu and Stefan Luchian, exponents of Romanian Modern Art were selected for a technical study on easel painting canvases. Both the physical integrity and the appearance of the artefacts derive mainly from the strength of the canvas and the physical and chemical characteristics of the fibres imparting their response to deterioration. In order to determine a deterioration pattern for canvases subjected to environmental stress, a simulation on flax fibres samples was performed using a climatic lab chamber. Structural changes of lignocellulosic materials were monitored by attenuated total reflectance infrared (ATR-FTIR) and FT-Raman spectroscopy. Changes in the intensity of FT-Raman signals of flax fibres indicate the evolution of the degradation phenomena due to environmental stress.
The deterioration of the natural polymers is a very complex process, and a problem that can be best addressed through modelling. The approach for modelling the rheological behaviour of different cellulose-based textile fibres (cotton, hemp, flax) when subjected to a hydrothermal treatment, followed by exposure to different doses of gamma-rays (5, 10, 15 and 25 kGy) is presented here. In order to predict the optimum radiation dose limit and hydrothermal aging time, the mathematical model was developed using MATLAB computational technique. To study the mechanical behaviour of the tested fibres, tensile tests were carried out using a TINIUS OLSEN dynamometer H5KT according to ISO 2062 norm. The model of correlation between the mechanical properties of the fibres and the independent variables was based on a polynomial second-degree equation, with the Least-Squares fitting approach that led to the coefficients of the mathematical model.
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