Simultaneous DSC-TG and DTA-TG were used to investigate the calatytic effect of the metal on the thermal decomposition of
a cellulose matrix containing small copper particles. The techniques were also used to demonstrate the effect of the metal
particles on the subsequent activation of the carbon matrix, a process which develops the pore structure necessary to expose
the metal particles to the gas phase. Temperature programmed desorption was used to study the initial mass loss found on activation.
To quantify the catalytic effect of the copper particles on the activation process an estimate was made of the activation
energy of the catalysed and uncatalysed reactions. The work gives valuable information on the processes involved in the preparation
of a new range of metal-carbon catalysts.
Authors:R. H. Meinhold, H. Atakul, T. W. Davies, and R. C. T. Slade
The structural changes occurring during the dehydroxylation of kaolinite have been followed using flash calcination to produce kinetically frozen calcines. The percentage of dehydroxylation was varied by changing the furnace residence time or temperature and/or heating speed. These calcination conditions affected the reaction kinetics, but the products depended only on the extent of dehydroxylation.
Authors:Piotr Szterner, Bernard Legendre, and Mehrez Sghaier
The physicochemical properties of theophylline hydrate and anhydrous polymorphic forms I and II were evaluated using crystallographic
and calorimetric method. This study has been carried out with the following techniques: differential scanning calorimetry
(DSC), thermogravimetric analysis (TG) and X-ray diffractometry. The X-ray patterns on powder for investigated compounds are
Authors:N. Barros, J. Salgado, M. Villanueva, J. Rodriquez-Añón, J. Proupin, S. Feijóo, and M. Martín-Pastor
The environmental concern on soil exploitation, linked to global warming by the Kyoto protocol, is responsible for increasing interest in the understanding of the role of the composition and structure of the soil organic matter (SOM) on soil carbon, C, dynamics. Thermal analysis and nuclear magnetic resonance (NMR) are applied to study the thermal properties, the structure and composition of the SOM of six samples with different C contents in order to improve the interpretation of results given by thermal analysis. Results showed that the direct integral of the combustion peaks obtained by DSC and the percentage of SOM given by TG were both directly related to the quantity of total soil C. Thus, soils with higher C content showed higher energy content too. The combustion temperatures of the curves given by DSC are those reported for labile OM. NMR results indicated the presence of aliphatic C, carbohydrates, and a weak signal in the aromatic C band in all the samples that was not detected in the DSC curves. Only two samples showed carboxyl/carbonyl C which was not detected by DSC also.
Authors:Zongxue Yu, Yuxi Sun, Wenxian Wei, Lude Lu, and Xin Wang
Orthorhombic structural perovskite NdCrO3 nanocrystals with size of 60 nm were prepared by microemulsion method, and characterized by XRD, TEM, HRTEM, SEM, EDS and
BET. The catalytic effect of the NdCrO3 for thermal decomposition of ammonium perchlorate (AP) was investigated by DSC and TG-MS. The results revealed that the NdCrO3 nanoparticles had effective catalysis on the thermal decomposition of AP. Adding 2% of NdCrO3 nanoparticles to AP decreased the temperature of thermal decomposition by 87° and increased the heat of decomposition from
590 to 1073 J g−1. Gaseous products of thermal decomposition of AP were NH3, H2O, O2, HCl, N2O, NO, NO2 and Cl2. The mechanism of catalytic action was based on the presence of superoxide ion O2− on the surface of NdCrO3, and the difference of thermal decomposition of AP with 2% of NdCrO3 and pure AP was mainly caused by the different extent of oxidation of ammonium.
Authors:Anabela Coelho, Luís Costa, Maria Marques, Isabel Fonseca, Maria Lemos, and Francisco Lemos
High-density polyethylene (HDPE) was cracked over HZSM-5 and HY zeolites and the reaction was followed using simultaneous
thermogravimetry (TG) and differential scanning calorimetry (DSC) and was compared with the degradation of the same material
in the absence of an added catalyst. The products obtained in the degradation reaction were analyzed by gas chromatography.
The simultaneous use of the signals from the TG and DSC allowed an accurate description of the thermal and catalytic degradation
of the polymer by application of a novel kinetic model that correlates the two signals that are measured. The kinetic parameters
were estimated by fitting this model to the experimental data obtained by TG and DSC. For both zeolites, the polymer degradation
takes place at lower temperatures when compared with pure thermal degradation. It was also observed that the two zeolites
have a distinct influence on the product distribution.
Authors:A. S. Tompa, R. F. Boswell, P. Skahan, and C. Gotzmer
The dinitramide salts of ammonia (ADN), hexamethylenetetramine (HDN), potassium (KDN), and sodium (NaDN) showed a linear relationship between the DSC rate of decomposition at the peak maximum and the DEA tanδ value at the low temperature transition peak. As the cation basicity increased in the series ADN<HDN<KDN<NaDN, there was an increase in the low temperature transition peak, the energy barrier for relaxation, and the decomposition peak temperature, and a decrease in the tanδ value at the low temperature transition peak, specific heat capacity, and the rate and enthalpy of decomposition. The more basic salts were more thermally stable (i.e., higher decomposition temperature) and less energetic (i.e., lower enthalpy of decomposition). The more internal free volume (disorder) present in these salts, the higher the rates of relaxation and decomposition. Five aluminum powders of different surface areas were analyzed by DSC in platinum sample pans, and it was found that the enthalpy and rate of oxidation increased as the particle size of Al decreased while the enthalpy of the Al melt decreased. TG showed a two-step weight gain in the oxidation of Al with plateaus in the 650 and 1130°C regions and the percent weight gain increased as the particle size of Al decreased. Variable DSC and TG heating rate studies showed that the activation energies for the first step in the oxidation process increased as the particle size of Al increased.
Authors:K. Voloshchuk, I. Popovic, S. Martinov, A. Donskikh, G. Tseitlin, and J. Velickovic
The thermal behaviour of three aromatic polymers, poly(3,3-dioxy-4,4-diphenylmethane) (POA), poly(2,2-m-phenylene-5,5-dibenzoxazolemethane)
(PBO) and a commercial poly-(phenyleneisophthalamide) (Phenylon) was studied by thermal analysis, i.e. DSC and TG. PBO was
formed by the progressive thermocyclization of POA. By transforming POA into PBO the thermal stability was increased proportionally
to the degree of cyclization, due to the stiffening of the polymer chain. PBO was found to be more thermally stable than Phenylon.
The activation energies of the desorption of moisture, cyclization and thermal degradation of the polymers in both nitrogen
and air were determined from non-isothermal TG data.
Authors:A. Sykuła-Zając, E. Łodyga-Chruścińska, B. Pałecz, R. E. Dinnebier, U. J. Griesser, and V. Niederwanger
232.70 °C, heat of fusion 60.40 J g −1 ), and quartz (melting point 573.50 °C, heat of fusion 8.40 J g −1 ). A heating rate of 10 °C min −1 was routinely used.
A differential scanning calorimeter coupled with a Setaram DSC–TG 111
Thermal analysis methods are well-established techniques in research laboratories of pharmaceutical industry. The robustness
and sensitivity of instrumentation, the introduction of automation and of reliable software according to the industrial needs
widened considerably the areas of applications in the last decade. Calibration of instruments and validation of results follow
the state of the art of cGMP as for other analytical techniques. Thermal analysis techniques are especially useful for the
study of the behavior of the poly-phasic systems drug substances and excipients and find a unique place for new delivery systems.
Since change of temperature and moisture occur by processing and storage, changes of the solid state may have a considerable
effect on activity, toxicity and stability of compounds. Current requirements of the International Conference of Harmonisation
for the characterization and the quantitation of polymorphism in new entities re-enforce the position of thermal analysis
techniques. This challenging task needs the use of complementary methods. Combined techniques and microcalorimetry demonstrate
their advantages. This article reviews the current use of thermal analysis and combined techniques in research and development
and in production. The advantage of commercially coupled techniques to thermogravimetry is emphasized with some examples.