Authors:N. Doca, Gabriela Vlase, T. Vlase, and G. Ilia
The thermal behavior of Cd2+ and Co2+ phenyl-vinyl-phosphonates was studied using two different experimental strategies: the coupled TG-EGA (FTIR) technique by
decomposition in nitrogen respectively air, and the kinetic analysis of TG data obtained in dynamic air atmosphere at four
heating rates. In nitrogen two decomposition steps were observed: the loss of crystallization water, respectively the decomposition
of the phenyl-vinyl radical. In air, the same dehydration was observed as the first step, but the second one is a thermooxidation
of the organic radical with formation of the pyrophosphoric anion.
The kinetic analysis of the TG non-isothermal data was performed by the isoconversional methods suggested by Friedman and
Flynn, Wall and Ozawa, as well as by the non-parametric (Sempere-Nomen) method. All processes put in evidence in TG curves
exhibit strong changes of the activation energy values with the conversion degree, which mean that these processes are complex
ones. Assuming that each of these processes consists in two steps, the application of non-parametric method leads to average
values of the activation energy close to the average values of this parameter obtained by isoconversional methods.
Authors:V. Balek, H. Mitamura, T. Banba, M. Beneš, Z. Málek, I. N. Beckman, I. M. Bountseva, H. Haneda, and T. Mitsuhashi
Summary Emanation thermal analysis (ETA) was used to characterize thermal behaviour of the perovskite ceramics designed as a matrix for the encapsulation of high level radioactive waste. The perovskite ceramics (composition CaTiO3 where small admixtures of Nd and Ce simulated the radioactive elements Cm and Pu, respectively) was prepared from sol-gel precursors by hot pressing at 1250°C/29 MPa for 2 h. The chemical durability of the ceramics was tested by leaching in the solution with pH 2 at 90°C/2 months. ETA results of ‘as-leached’ and ‘as-prepared’ perovskite ceramics samples were compared and evaluated by means of a mathematical model. Three temperature ranges of the annealing of structure defects in the ‘as-prepared’ sample were determined from the decrease of radon release rate in the ranges 280-560, 800-960 and 960-1200°C, respectively. One annealing step was determined for the ‘as-leached’ sample from the decrease of radon release rate in the range of 800-950°C.
Differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) were used to study the thermal behaviour of (50-x)Na2O-xTiO2-50P2O5 and 45Na2O-yTiO2-(55-y)P2O5 glasses. The addition of TiO2 to the starting glasses (x=0 and y=5 mol% TiO2) resulted in a nonlinear increase of glass transition temperature and dilatation softening temperature, whereas the thermal
expansion coefficient decreased. All prepared glasses crystallize under heating within the temperature range of 300–610°C.
The contribution of the surface crystallization mechanism over the internal one increases with increasing TiO2 content. With increasing TiO2 content the temperature of maximum nucleation rate is also gradually shifted from a value close to the glass transition temperature
towards the crystallization temperature. X-ray diffraction measurements showed that the major compounds formed by glass crystallization
were NaPO3, TiP2O7 and NaTi2(PO4)3. The chemical durability of the glasses without titanium oxide is very poor, but with the replacement of Na2O or P2O5 by TiO2, it increases sharply.
Authors:A. Aouad, M. Benchanâa, A. Mokhlisse, and A. Arafan
Thermogravimetry (TG), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) were used
to study the thermal behaviour of the organic matter in the natural phosphate and its concentrate kerogen from the Moroccan
deposit. The TG analysis showed that both the investigated samples exhibited a one-step thermal oxidation in the main mass
loss area, between 160 and 540C, attributed to the hydrocarbon material. When DSC analyses of oxidation as well as pyrolysis
yielded two evolutionary stages of the hydrocarbon in this temperature range : the first one at 160-360C and the second one
above 360C. Pyrolytic kerogen decomposition was monitored by measuring changes in the principal FTIR organic bands. The results
showed, in the first stage, the progressive decrease of signals due to CH2 and CH3 vibrations as well as the carbonyl and carboxylic bands, and their subsequent disappearance at 300C. In the second stage
above 400C, the signal due to the aromatic components (1600 cm-1) appeared but decreased with increasing temperature up to 540C.
CaAl12O19 was synthesised using three different precursors: (a) a polyesteric type precursor resulted from the traditional Pechini method; (b) a polyesteric type precursor resulted from the reaction between citric acid and calcium and aluminum nitrates; and (c) a polymeric type precursor resulted from the reaction between acrylic acid and calcium an aluminum nitrates. The thermal behavior of the three precursors used in the CaAl12O19 synthesis was monitored to underline the thermal effects associated to the CaAl12O19 formation. Thermal analyses performed on precursors do not reveal clear differences regarding the thermal effects assigned to calcium aluminates formation, at temperatures over 800 °C. In contrast, thermal analysis of samples pre-fired at 200 °C, and especially at 600 °C, show clear differences between samples obtained in different ways. It is noted that in samples obtained from acrylic acid and nitrates, and citric acid and nitrates, CA6 is practically single phase after calcination at 1,200 °C. However, in the sample obtained from citric acid, ethylene glycol, and nitrates, calcined at 1,200 °C, CA6 is present along with CA2 and α-Al2O3.
Authors:S. Musić, G. Štefanić, N. Vdović, and A. Sekulić
Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected toγ-irradiation up to a final
dose of 20 MGy. The effects of the γ-irradiation were examined by X-ray powder diffraction, laser Raman spectroscopy, differential
scanning calorimetry and microelectrophoretic measurements. It was found that γ-irradiation had no influence on the behaviour
of zirconium hydroxide during calcination and subsequent cooling. The results of microelectrophoretic measurements showed
that γ-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium
hydroxide precipitated at pH 2 proved to be the most susceptible to γ-irradiation, while the sameγ-irradiation had very little
(if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After γ-irradiation, the electrophoretic
mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase
in its adsorption capacity. The analogy observed between the pH-dependence of the effects of γ-irradiation on the electrokinetic
behaviour of zirconium hydroxide and the influence of ball-milling on the thermal behaviour of zirconium hydroxide  suggested
that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH.
The number of the cities with canalized water and sewage treatment stations has increased lately and consequently having in
mind the great concern on environment preservation and the quality of the water used by society. However, these stations are
nowadays causing another kind of problem: a huge quantity of sludge as residue. Due to the implication of the residue on the
environment and, consequently, to human life quality, performing of an accurate investigation about the components of such
sludge, as well as the thermal stability of this residue in the environment become necessary. This paper presents a study
on sludge from water and sewage treatment station, as well as the thermal characterization of residue. Such study was performed
through FTIR, atomic absorption, thermoanalytical (TG/DTG, DTA) techniques, that made it possible to observe that the main
components of the sludge are clay, carbonates and organic substance, presenting a low rate of metals and a unique thermal
behavior since the sludge from the treatment station has a higher thermal stability.
Thermal, chemical and rheological properties of ultraviolet aged asphalt binder were characterized by differential scanning
calorimetry (DSC), Fourier transform infrared (FTIR) and dynamic shear rheometer (DSR), respectively. Asphalt binder samples
were made with different film thickness (50, 100, 200 and 500 μm) and suffered different ageing time (0, 48, 96 and 144 h),
at a certain UV radiant intensity of 20 w m–2 in a self-made accelerated ageing oven. The results indicate that the UV light ageing would lead to the improvement of thermal
behavior and the growth of the glass transition temperature of asphalt binder. This type of ageing can be also reflected from
the FTIR spectra in terms of the characteristic peaks of the carbonyl groups and sulphoxides. The UV light ageing can change
some rheological parameters of asphalt binder, such as complex modulus and phase angle. The ageing degrees of asphalt binder
by this type of ageing test are mainly related to the ageing time and film thickness of the sample.
Ammonium nitrate (AN) is one of the main nitrogen fertilizers used in fertilization programs. However, AN has some serious
disadvantages — being well soluble in water hardly 50% of the N-species contained are assimilated by plants. The second disadvantage
of AN is associated with its explosive properties. The aim of this paper was to clarify the influence of different lime-containing
substances — mainly Estonian limestone and dolomite — as internal additives on thermal behaviour of AN.
Commercial fertilizer grade AN was under investigation. The amount of additives used was 5, 10 or 20 mass%, or calculated
on the mole ratio of AN/(CaO, MgO)=2:1 in the blends. Experiments were carried out under dynamic heating condition up to 900°C
(10°C min−1) in a stream of dry air or N2 by using Setaram Labsys 2000 equipment coupled to Fourier transform infrared spectrometer (FTIR).
The results of analyses of the gaseous compounds evolved at thermal treatment of neat AN indicated some differences in the
decomposition of AN in air or in N2. At the thermal treatment of AN’s blends with CaCO3, MgCO3, limestone and dolomite samples the decomposition of AN proceeds through a completely different mechanism — depending on
the origin and the content of additives, partially or completely, through the formation of Mg(NO3)2 and Ca(NO3)2.
Authors:Rodica Olar, Mihaela Badea, Oana Carp, Dana Marinescu, Veronica Lazar, Carmen Balotescu, and Anca Dumbrava
The investigation concerning the synthesis, spectrochemical and biological properties as well as thermal stability of some
tiosulfato-and sulfato copper(II) complexes of type [Cuphen(S2O3)(H2O)n]·mH2O (phen: 1,10-phenanthroline; (1): n=2, m=0; (2): n=2, m=0.5) and respectively [Cuphen(OSO3)(H2O)n] ((3): n=0; (4): n=2) are presented in this paper. The bonding and stereochemistry of the complexes have been characterised by IR and electronic
studies. The in vitro qualitative and quantitative assays of the antimicrobial activity of the tested compounds vs. planktonic and adherent Gram negative bacterial strains isolated from different surfaces in the hospital environment demonstrated
that all compounds exhibited very good antimicrobial activity vs. Escherichia coli, Klebsiella sp. and Enterobacter sp. with very low M.I.C. values.
The thermal analysis has evidenced the thermal intervals of stability and also the thermodynamics effects that accompany them
both in synthetic air and argon. The thermal behaviour is complex according to DTG and DSC curves including dehydration as
well as thiosulfate and phenanthroline decomposition.