Authors:M. Reháková, K. Jesenák, S. Nagyová, R. Kubinec, S. Čuvanová, and V. Fajnor
Copper forms of synthetic zeolite ZSM5 containing ethylenediamine (en) were characterised by methods of thermal analyses - TG, DTA and DTG in the temperature range 20-1000C, in air and in argon
atmosphere. Mass spectroscopy was used for the study of the released gas products of thermal decomposition. The results of
thermal analyses of three Cu(en)xZSM5 zeolitic products with different composition (x depends on the mode of preparation) checked their different thermal properties.
The main part of the decomposition process occurs at considerably higher temperatures than the boiling point of ethylenediamine
of all three products, it proves strong bond and irreversibility of en-zeolite interaction. According to the results of the
mass spectroscopy method the decomposition process in inert atmosphere is characterised by the development of a large spectrum
of products with atomic mass from 28 to 178 atomic mass units, and there is a correlation between the mode of sample preparation
and the spectrum of the released products.
Three interesting new compounds formed as a result of phenols-iodine redox reactions were investigated by mass spectral fragmentation (MS) and thermal analyses (TA) as well as some other physicochemical methods as microanalysis and infra-red spectroscopy to elucidate their structures. The characterization of the compounds was satisfactorily achieved by using the above analytical tools and their proposed general formulae, were found to be C24H15O8I (PC-IO
), C24H14O12 I2 (PG-IO
) and C12H8O6I2 (PG-IO
).The fragmentation pathways of PC-IO
have been examined using electron ionization (EI) mass spectrometry in comparison with thermal analyses (TG and DTA). Both decomposition modes were investigated, and the fragmentation pathways were suggested. The combined application of mass spectrometry and thermogravimetry (MS and TG) in the analysis of the products allowed the characterization of the fragmentation pathway in MS.The major pathway in both techniques of PC-IO
is due to the loss of CHO followed by CH3I+2H2O. It is due to the loss of 2H2O followed by the loss of 2CH3I for PG-IO
. While for PG-IO
it is related to the loss of 2H2O followed by loss of 2CH3I molecule stepwise. Different stabilities for initial products and some fragments are discussed.
Heat capacities (Cp) of solid benzene, biphenyl,p-terphenyl,p-quaterphenyl, and poly-p-phenylene were analyzed using the ATHAS Scheme of computation. The calculated heat capacities based on approximate vibrational
spectra of solid benzene and the series of oligomers containing additional phenylene groups were compared to experimental
data newly measured and from the literature to identify possible additional large-amplitude motion. The skeletal heat capacity
was fitted to the Tarasov equation to obtain the one- and three-dimensional vibration frequencies Θ1 and Θ3 using a new optimization approach. Their relationship to the number of phenylene groupsn is: Θ1=426.0−150.3/n; and Θ3=55.4+81.8/n. Except for benzene, the quantitative thermal analyses do not show significant contributions from large-amplitude
motion below the melting temperatures.
Authors:Rodica Olar, Mihaela Badea, Dana Marinescu, and Ramona Mardale
New complexes of type [Cu(L1)2(OH2)]·4H2O (1), [Cu(L2)(OH2)]·0.5H2O (2) and [Cu3(L3)2(OH2)3]·0.5H2O (3) were synthesized by [1 + 1], [1 + 2] and [1 + 3], respectively, template condensation of 2,4,6-triamino-1,3,5-triazine and salicylic aldehyde in the presence of copper(II). The features of complexes have been established from microanalytical, IR and UV–Vis data. The thermal analyses have evidenced the thermal intervals of stability and also the accompanying thermodynamic effects. Processes as water elimination and oxidative degradation of the organic ligands were observed. After water elimination, complexes revealed a similar thermal behaviour. The final product of decomposition was copper(II) oxide as powder X-ray diffraction indicated.
Authors:Y. Sawada, K. Omika, Y. Ito, F. Muta, and M. Momota
The formation process of a ceramic (indium oxide) thin film (thickness: approximately 20 nm to several microns) was investigated
by thermal analyses. Thermal changes of an organic precursor, indium(III) 2-ethylhexanoate, dip-coated on a glass substrate
was successfully detected by DSC in air. Exothermic phenomena were observed at marked lower temperatures for the thin films
than for the bulk material; thinner films had slightly lower peak temperatures. The reaction mechanism is discussed with reference
to mass spectra of the evolved gases.
The thermal characterization of polypropylene (PP) composites containing untreated and treated zeolite with different silane
coupling agents was carried out using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) to investigate
the effects of natural zeolite and surface modifiers on melting, crystallization and degradation behaviour of PP. 3-aminopropyltriethoxysilane
(AMPTES), methyltriethoxysilane (MTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) were used as surface modifiers at four
different concentrations (0.5–2.0 mass%). Thermal analyses indicated that silane treatment and 2–6 mass% zeolite addition
have no significant effect on the melting and degradation temperatures of the composites. The crystallization temperatures
of the composites were increased due to the nucleating effect of the zeolite. The influence of the modifiers on the interactions
between PP and zeolite was determined by the activities of untreated and treated zeolite. The maximum interactions leading
to good adhesion were observed in the AMPTES treated composites. Also, non-isothermal crystallization kinetics of the composites
was analyzed using Avrami and Kissinger models.
The thermal decomposition of the polypropylene and liquid paraffin mixtures with inorganic additives was studied in dynamic
conditions. Thus, typical thermal analyses were carried out and thermal decomposition of samples in a specially designed apparatus
was also processed. One can observe for samples of sufficiently low mass that thermal analysis allows clear distinction of
samples that contain and do not contain liquid paraffin, respectively. Moreover, it is possible to separate two stages of
the decomposition process. The relationship between the logarithm of conversion degree and temperature (so called three-parameter
model) was used for the description of these processes. Relations between coefficients in three-parameter equation in micro-scale,
and characteristic temperatures of thermal decomposition in laboratory scale were observed in spite of meaningful differences
in the course of the processes.
Authors:Paola Bassani, E. Gariboldi, and D. Ripamonti
Heat-treatable aluminium alloys are widely used for structural applications. Their strength is obtained through age hardening
phenomena, that are sensitive to microalloying.
In the present paper the results of thermal analyses on the ageing behaviour of an Al-Cu-Mg-Si alloy with silver and zirconium
additions are presented. Specimens were water quenched after solution heat treatment, then aged at 453 K and a hardness-versus-time
plot was drawn. Samples representative of different ageing conditions were subjected to DSC scans.
Peaks were identified taking into account θ and Q phases precipitation sequences. Solution treated samples showed GP/θ″/θ′/Q
sequence, while in peak aged condition GP and θ″ precipitation peaks disappeared and a reduction of θ′ peak area was observed,
witnessing the concurrent presence of θ″ and θ′ phases at peak hardness condition. Experimental data were compared with results
from analogous investigations performed on a conventional commercial Al-Cu-Mg-Si alloy.
Authors:T. Hashimoto, M. Yoshinaga, Y. Ueda, K. Komazaki, K. Asaoka, and S. Wang
The phase transitions of Ba2-xSrxIn2O5 were investigated with various thermal analyses and high-temperature X-ray diffraction. It was clarified that crystal structure
of Ba2-xSrxIn2O5 with x=0.0~0.4 varies from brownmillerite through distorted perovskite to another distorted perovskite with increase of temperature.
The phase transition from brownmillerite to distorted perovskite was revealed to be first order, whereas transition from distorted
perovskite to another one was second order. The specimen with x≥0.5 showed only one first order phase transition from brownmillerite to distorted perovskite. The phase diagram of Ba2-xSrxIn2O5 was established and existence of tricritical point at ~1100C with x=0.4~0.5 was suggested.
Authors:M. Olguin, M. Solache-Rios, D. Acosta, P. Bosch, and S. Bulbulian
The capacity of bentonite and purified bentonite to remove UO
ions from aqueous solutions has been investigated. The UO
uptake in these clays was determined for 0.2 and 0.002M uranyl nitrate solutions. It was found that under these conditions (0.2M) the maximum UO
uptake was 1.010±0.070 meq UO
/g of bentonite and 0.787±0.020 meq UO
/g of purified bentonite. In purified bentonite UO
sorption is irreversible up to 50 hours as no desorption was observed. Such is not the case in the natural bentonite. X-ray diffraction, thermal analyses, and transmission electron microscopy were used to characterize the solids. The uranium content was determined by neutron activation analysis.