The thermal behavior for three homologous series of cationic geminis surfactants of the type n-2-n, alkanediyl-α,ω-bis(alkyldimethylammonium bromide), with n = 12, 14, 16, and 18, and sodium alkyl sulfates, SCmS, with m = 12, 14, and 16, is reported here. The cationic/anionic molar ratio is kept at 1:2 (equicharged mixtures), and salt is also
present. Polarizing light microscopy and differential scanning calorimetry show a stepwise fusion for the mixtures with appearance
of several mesophases between the crystalline structures and the isotropic liquid. A main endothermic transition is observed,
associated with partial chain melting and consequent loss of crystalline order, followed by a transition to a smectic liquid
crystal. The phase transition thermodynamics is interpreted in terms of an interplay between van der Waals chain–chain interactions
and ionic head group interactions.
Authors:J. Rincon, M. Romero, C. Díaz, V. Balek, and Z. Malek
The silica waste originating from a geothermal power plant in Mexico was investigated with the aim of finding its applicability
as a raw secondary material for ceramics production. The thermal behaviour of the original silica waste (containing NaCl and
KCl from marine brine) and of the purified silica was characterized by means of DTA/TG, emanation thermal analysis (ETA) and
thermodilatometry (TD). The reactivity of the purified silica waste mixed with CaCO3 (1.8 mass%) was characterized by means of ETA, DTA and TG. The microstructures and phase compositions of the final products
prepared by heating in air were tested by means of X-ray diffraction and of scanning electron microscopy coupled with electron
probe X-ray microanalysis. The thermal analysis methods allowed determination of the optimal conditions for thermal treatment
of the silica waste in order to obtain partly sintered porous materials for use as refractory bricks.
Authors:X. Zhang, Y. Ding, Y. Zhang, Y. Hao, G. Meng, and L. Zhang
Highly oriented single crystal antimony nanowire arrays have been synthesized within anodic aluminum oxide (AAO) template
by pulsed electrodeposition. Thermal behavior and oxidation analysis of the antimony nanowires have been investigated by means
of thermogravimetry and differential scanning calorimetry in Ar and air atmosphere, respectively. Compared to bulk antimony,
the antimony nanowires exhibit a lower sublimation temperature at 496.4°C. Evident oxidation of the Sb nanowires occurs at
429.8°C in air atmosphere and α-Sb2O4 nanowires have been obtained as the oxidation product. The results indicate that the sublimation and the oxidation of the
antimony nanowires in the AAO template is a slow multi-step process. The present results are of relevance when processing
antimony nanowries for thermoelectric applications at high temperatures.
Authors:A. González, J. J. Suńol, J. Bonastre, L. Escoda, and J. Caleya
Summary Several Fe-Ni-P-Si alloys were produced in an amorphous state by mechanical alloying and rapid solidification. Thermal behavior of the as prepared alloys was analyzed and compared with identical alloys stored during 1 and 2 years. During annealing time, several exothermic processes related to the structural relaxation were detected at low temperature and with further crystallization at high temperature. As increasing the storage time, the powdered samples were relaxed at lower temperatures. The activation energy, E, of the main crystallization process varies between 2.7 and 4.7 eV at.-1. The E values obtained remains similar with the storage time. Small contamination from the milling tools was found. Furthermore, powdered alloys are more sensible to oxidation processes than as quenched ribbons.
Authors:P. Pulišová, J. Boháček, J. Šubrt, L. Szatmáry, P. Bezdička, E. Večerníková, and V. Balek
Thermogravimetry-differential thermal analysis, emanation thermal analysis, mass spectrometry detection, Fourier transform
infrared and XRD were used to characterize thermal behaviour of titanium dioxide photocatalyst precursors prepared by precipitation
at various conditions from peroxotitanic acid sols. The transmission electron microscopy HRTEM technique was used to characterize
the surface microstructure. The sols contained TiO2 anatase particles of approximately 10 nm in diameter. During heating of the air dried samples, their chemical degradation
took place giving rise to anatase. On further heating, the crystallization of anatase and formation of rutile phase was observed.
To test the photocatalytic activity of the samples, the decomposition of 4-chlorophenol (4-CP) under ultraviolet and visible
irradiation was monitored. It was shown that photocatalytic activities of the samples are comparable to the Degussa P25 photocatalyst
Authors:G. Vlase, T. Vlase, N. Doca, M. Perţa, G. Ilia, and N. Plesu
Samples of an organic–inorganic hybrid were prepared by solvolysis and polycondensation in formic acid of tetraethoxysilane
and diethylbenzyl phosphonate, simultaneous with the oxidative polymerization of aniline. The thermal behavior of the samples
in dynamic air atmosphere and non-isothermal conditions was determined by a coupled thermogravimetric/evolved gas analysis.
Two significant thermal events were established: the elimination from the polymeric matrix of low mass molecules, respectively
the thermooxidative degradation of the organic part of the matrix. The kinetic analysis was performed with the Flynn-Wall-Ozawa,
Friedman and modified Non-Parametric-Kinetic methods. Only the last one allowed an objective analysis of the first process
as a process of two simultaneous thermally induced phenomena with the kinetic functions of the type αm(1 − α)n.
The thermal behavior of chitosan (CS)/natural rubber latex (NRL) blends has been studied by thermogravimetry (TG) and differential
scanning calorimetry (DSC). Decomposition behavior of CS changes with the addition of NRL. The effect of blend composition
on the amount of residue remaining at various temperatures has been studied. Activation energies of degradation have been
calculated using Horowitz-Metzger equation. From the activation energy values, it is found that among the series of the blend
compositions, CS15NRL85 exhibits better thermal stability. DSC studies reveals that the CS/NRL blends are thermodynamically incompatible. This is
evident from the presence of two glass transitions, corresponding to CS and NRL phases in the blend.
Authors:C. Radhakrishnan, A. Sujith, and G. Unnikrishnan
The thermal behaviour of styrene butadiene rubber (SBR)/poly (ethylene-co-vinyl acetate) (EVA) blends was studied by using
thermogravimetry (TG) and differential scanning calorimetry (DSC). The effects of blend ratio, cross-linking systems and compatibilization
on the thermal stability and phase transition of the blends were analyzed. It was found that the mass loss of the blends at
any temperature was lower than that of the components, highlighting the advantage of blending SBR and EVA. The addition of
compatibilizer was also found to improve the thermal stability. DSC studies indicated the thermodynamic immiscibility of SBR/EVA
system even in the presence of the compatibilizer. This is evident from the presence of two different glass transition temperatures,
corresponding to SBR and EVA phases in both compatibilized and uncompatibilized blends.
Authors:P. K. Singh, A. B. Mathur, and G. N. Mathur
The thermal behaviours of polystyrene (PS), polymethylacrylate (PMA), polyacrylonitrile (PAN), polystyrene-co-methylacrylate [P(S: MA)](alternate and random), polystyrene-co-acrylonitrile [P(S: AN)] (alternate) and a terpolymer of styrene, methylacrylate and acrylonitrile [P(S: MA: AN)] are discussed on the basis of non-isothermal thermogravimetric studies. The thermal stabilities of the copolymers have been found to be intermediate between of those of the individual homopolymers. The stability of the [P(S: AN)] copolymer is higher than those of the individual homopolymers. The activation energy values are also in accordance with the thermal behaviours of these polymers.
To reveal the fire injuring of parchment, the changes in the thermal behaviour of some goat parchments, obtained from skins
originating from different animals, as a result of thermal aging were determined by thermal analysis methods (DSC; simultaneous
TG/DTG, DSC; micro hot table (MHT)). Thermal aging of parchments was revealed to bring about the decrease in shrinkage temperature,
absolute value of enthalpy of denaturation in water and some changes in non-isothermal parameters characteristic for dehydration
process in static air atmosphere.
The results obtained by DSC analysis performed in N2 and O2 flows as well as those obtained by simultaneous TG/DTG, DSC analyses have shown that both softening (melting) process parameters
and parameters of thermo-oxidative processes have not been changed by thermal ageing. The results obtained by thermal analysis
methods were correlated with those obtained by microscopic investigation of parchment samples immersed in water and scanning
electron microscopy (SEM). The application of these microscopic techniques has revealed the morphology changes in the investigated
parchments as a result of thermal degradation.