Papers by Author: Dorel Radu

Abstract: The paper presents a study of the industrial waste incorporating in glass in order to obtain decorative colored glasses. The influence of iron and chromium oxides from waste amount is discussed. The samples properties such as density, thermal expansion coefficient and viscosity are investigated. Including different oxides of heavy metals (obtained from sludge that contains chromium and iron) into the vitreous system leads to the obtaining of several decorative glasses. Their colour varies widely, to the added quantity and the atmosphere of the work place.

Abstract: The paper follows both the national preservation and durable managing policy, as well as the European laws for the area of environmental protection (UE’s Directive 1999/31/EC – „landfill of waste” an the Council’s Directive no. 94/62/CE regarding the packaging and the packaging waste, amended by the Council’s Directive no. 2004/12/CE). The proposed technologies lead to reducing the need of both raw materials and energy in the process of obtaining various types of glass. The study proposes new ways of retrieving and eliminating waste that contains heavy metals alongside borosilicate shards. This paper also aims to increase the responsibility of the waste generating companies and to make the potential users more sensible.

Abstract: Alkaline earth metal silicates as well as many polyvalent metals silicates can be obtained through aqueous solutions reactions between an alkaline silicate solution and the solutions of metal salts. The vitrifiation of the oxide compositions, established by the necessary molar ratios for the projected glass, is realised by calculating the concentration of chemical precursors, through their reaction directly on the substrate. The sodium silicate viscosity in aqueous solution and the viscosity of nitrogenated compounds or oxalates necessary in the silicates synthesis is compatible with the necessary viscosity for ink-jet cartridges. The necessary silicates forming reactions were studied directly on the deposition support, so that the functional characteristics of the multicompartment ink-jet cartridges were used. Compositions were realised, in which the colouring effect was obtained with ionic colorants. The vitrifiation and the quality of the obtained thin films were studied through Optical Microscopy and Scanning Electron Microscopy.

Abstract: In contrast with transitional metals whose spectra and color depends a lot of the ligands strength field, the sensitivity of the rare earth spectra is significantly weaker. This is the reason why the color of these ions is the same whatever the basic vitreous matrix. These properties permit to establish a relation for the determination of the concentration of these ions in vitreous matrix directly from the optical transmission spectra. The paper presents some samples of silica and phosphate glasses with lanthanides content for nonlinear optical applications synthesized at a laboratory scale. VIS-NIR transmission curves are presented, for several compositions. For the correlation of the lanthanides content with the specific optical absorption peak one used a method starting from the Lambert – Beer law. For the Nd2O3 concentration determination, it was used a method proposed by D.M. Dood and D.B. Fraser for the OH groups content, with an error of +4%. For specific peaks, expressions for lanthanides concentration in ppm, related to the optical transmission were found. A possibility appears to directly find the lanthanides concentration from the absorption coefficient at specific wavelengths for each vitreous matrix. The influence of matrix is discussed.

Abstract: In present paper there are presented such correlations for the silica-alkali systems (M2O – SiO2) where reliable thermodynamic data exists from the thermal equilibrium diagrams. It was observed that with the saturation of SiO2 tetrahedron with metal ions, the difference in basicity between the reactants is diminished, in the order SiO2 → disilicate → metasilicate → orthosilicate, and that confirms the role of driving force for these reactions of the acid-base interaction between oxides and the intermediate silicates formed. Also, there were proposed some correlations between the standard formation Gibbs free energy, (Gº298), and basicity percentage, pB, for the binary compounds from the same oxide systems. Considering the fact that for a system at equilibrium, reaction constant Kp depends on the reaction free Gibbs energy (rG0 298) and temperature, a correlation between basicity difference through basicity percentage, pB, and rG0 298 is proposed.