Authors:M. Birzescu, M. Niculescu, Raluca Dumitru, P. Budrugeac, and E. Segal
The paper presents the experimental results of the structural investigations and thermal analysis of copper(II) oxalate, a
polynuclear coordination compound, obtained by a new method, through the reaction of 1,2-ethanediol with Cu(NO3)2·3H2O.
The reaction between 1,2-ethanediol and Cu(NO3)2·3H2O occurs, under some working conditions, with the oxidation of 1,2-ethanediol to the oxalate anion (L). The synthesized polynuclear
coordination compound, [CuL·0.3H2O]n, was characterized by chemical analysis, electronic and vibrational spectra and thermal analysis. The thermal properties
of the polynuclear coordination compound have been investigated by TG, DTG and DSC. The obtained decomposition product is
Powder XRD (X-ray diffraction), IR spectroscopy and TEM (transmission electron microscopy) were used to characterize the composition,
the crystalline structure and the surface morphology of the copper oxide obtained through thermolysis. The thermal conversion
product, copper(II) oxide, has a microporous structure with a large specific area.
Authors:M. Bîrzescu, M. Niculescu, Raluca Dumitru, Oana Carp, and E. Segal
The homopolynuclear coordination compound [CoL · 2.5H2O]n with L=C2O42− was synthesized by a new unconventional method. It consist in the redox reaction between 1,2-ethanediol and cobalt nitrate
in presence of nitric acid. The coordination compound was characterized by chemical analysis, electronic and vibrational spectra
respectively, thermal analysis. In the coordination compound the Co(II) ion exists in a high spin octahedral configuration
and oxalate anion acts as double-bridge ligand, tetradentate, similar as in CoC2O4 · 2H2O obtained by the classical method. Nonstoichiometric oxide, Co3O4+0.25 with deficit in cobalt and normal spinel Co3O4 where identified as thermal decomposition intermediates. As final product of decomposition, the oxide CoO was obtained.
Authors:Raluca Dumitru, Oana Carp, P. Budrugeac, M. Niculescu, and E. Segal
The authors present their results concerning the decomposition in air of the homopolynuclear coordination compound [CoC2O4·2.5H2O]n. In the temperature range 20–300 °C, the heating curves TG, DTG and DTA allowed to evidence three decomposition steps. The kinetic analysis was performed on the second step which proved to be the only workable one. The application of nonlinear regression procedure shows that this is a complex process consisting in three successive steps. The checking of the mechanism and corresponding kinetic parameters for quasi-isothermal data (T = 150 °C) shows that the obtained results could be used for prediction of the thermal behaviour of the investigated compound in both isothermal and non-isothermal conditions.
Authors:A. Rotaru, Catalin Constantinescu, P. Rotaru, Anca Moanţâ, M. Dumitru, Margareta Socaciu, Maria Dinescu, and E. Segal
A new synthesized 4CN type azomonoether, exhibiting dying properties, crystalline nature and generating interest as a material
for non-linear optical applications was investigated. Modern devices incorporating liquid crystals tend to use thin films
of such materials because of their special characteristics. Thermal stability studies are indispensable before attempting
any deposition experiment.
We have investigated the thermal behaviour of 4-[(4-chlorobenzyl)oxy]-4′-cyano-azobenzene (TG, DTG, DTA and DSC) in inert
flow atmosphere, under non-isothermal conditions. The phase transitions were studied by repeated heating-cooling regimes,
with intercalated isothermal steps. The thin films were deposited on silicon and quartz substrates by matrix assisted pulsed
laser evaporation (MAPLE) using a Nd:YAG laser working at 266 nm. FTIR spectroscopy of the obtained thin films confirmed the
preservation of the compound’s structure.
Authors:Maria Crişan, Ana Brăileanu, D. Crişan, Mălina Răileanu, N. Drăgan, Diana Mardare, V. Teodorescu, Adelina Ianculescu, Ruxandra Bîrjega, and M. Dumitru
Among the great number of sol-gel materials prepared, TiO2 holds one of the most important places due to its photocatalytic properties, both in the case of powders and coatings. Impurity
doping is one of the typical approaches to extend the spectral response of a wide band gap semiconductor to visible light.
This work has studied some un-doped and Pd-doped sol-gel TiO2 nanopowders, presenting various surface morphologies and structures. The obtained powders have been embedded in vitreous
TiO2 matrices and the corresponding coatings have been prepared by dipping procedure, on glass substrates. The relationship between
the synthesis conditions and the properties of titania nanosized materials, such as thermal stability, phase composition,
crystallinity, morphology and size of particles, and the influence of dopant was investigated.
The influence of Pd on TiO2 crystallization both for supported and unsupported materials was studied (lattice parameters, crystallite sizes, internal
strains). The hydrophilic properties of the films were also connected with their structure, composition and surface morphology.
The methods used for the characterization of the materials have been: simultaneous thermogravimetry and differential thermal
analysis, powder X-ray diffraction, electron microscopy (TEM, SAED) and AFM.