Authors:Ewa Kowalska, Elżbieta Czerwosz, Anna Kamińska, and Mirosław Kozłowski
Nanocomposite carbonaceous-palladium (Nc-C-Pd) films were synthesized by physical vapor deposition method (PVD). Scanning electron microscopy studies showed that they were composed of carbonaceous matrix containing Pd nanograins. Nc-C-Pd films were also characterized by thermogravimetric analysis, X-ray powder diffraction, and Fourier transform infrared (FTIR) spectral analysis. The content of Pd in films synthesized at different PVD conditions was determined based on TG measurements. Technological parameters of PVD process affected C/Pd ratio. FTIR spectra exhibited characteristic absorption bands for the precursors of carbonaceous-palladium samples (fullerene C60 and palladium acetate). The influence of hydrogen on electrical properties of the films was tested by measuring their resistance in the presence of hydrogen (1% H2/N2).
Authors:Dimitris Achilias, Maria Karabela, and Irini Sideridou
Thermal degradation kinetics of copolymers based on bis-phenol A ethoxylated dimethacrylate (Bis-EMA) with triethylene glycol
dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA) with TEGDMA in wt/wt ratios 30/70, 50/50, or 70/30 were investigated
using thermogravimetric analysis as a means to provide specific information regarding the internal structures of these resins.
Thermogravimetric scans were taken at four different heating rates to perform an isoconversional analysis to determine the
change of the effective activation energy as a function of conversion. A two-step degradation mechanism was found to occur
in almost all copolymer compositions attributed to the existence of inhomogeneities in the macromolecular structure and the
formation of weak links inside the polymeric network.
Authors:H. Bordeneuve, A. Rousset, C. Tenailleau, and S. Guillemet-Fritsch
Thermogravimetric analysis was used in order to study the reduction in air of submicronic powders of Co3−xMnxO4 spinels, with 0 ≤ x ≤ 1. For x = 0 (i.e. Co3O4), cation reduction occurred in a single step. It involved the CoIII ions at the octahedral sites, which were reduced to Co2+ on producing CoO. For 0 < x ≤ 1, the reduction occurred in two stages at increasing temperature with increasing amounts of manganese. The first step
corresponded to the reduction of octahedral CoIII ions and the second was attributed to the reduction of octahedral Mn4+ ions to Mn3+. From the individual weight losses and the electrical neutrality of the lattice, the CoIII and Mn4+ ion concentrations were calculated. The distribution of cobalt and manganese ions present on each crystallographic site of
the spinel was determined. In contrast to most previous studies that took into account either CoIII and Mn3+ or Co2+, CoIII and Mn4+ only, our thermal analysis study showed that Co2+/CoIII and Mn3+/Mn4+ pairs occupy the octahedral sites. These results were used to explain the resistivity measurements carried out on dense ceramics
prepared from our powders sintered at low temperature (700–750 °C) in a Spark Plasma Sintering apparatus.
Some manganese oxides are considered hyperactive under microwave irradiation because of their extremely high heating rates
in air. In order to further understand this hyperactivity, thermodynamic calculations, thermogravimetric analysis and both
real and imaginary permittivity determinations were performed for hausmannite (Mn3O4) as a function of temperature in an air atmosphere. The thermodynamic results demonstrated reasonable agreement with the
thermogravimetric analysis data. A comparison of the derivative thermogravimetric analysis data with the derivative of both
the real and the imaginary permittivities confirmed that the extremely high values of the permittivities were due to the conversion
of the hausmannite to bixbyite (Mn2O3). The microwave hyperactivity of the manganese oxides in air is explained in terms of the high permittivities of bixbyite.
Authors:M. N. Radhakrishnan Nair and M. R. Gopinathan Nair
Thermal stability of solution-cast blends of poly(vinylchloride) and NR-b-PU block copolymers of three different chain extender diols was studied by thermogravimetry. Thermal degradation of individual components and their blends were investigated with special reference to blend ratio. As the block copolymer content in the blends increased their thermal stability was also found to increase. Enhanced thermal stability of PVC is believed due to the favorable interaction with PVC and the PU hard segments of the block copolymer. DTG curves were used for the determination of different stages involved in the degradation. Activation energy for degradation was determined from Coats–Redfern plot.
Authors:T. Fujimura, N. Sarugaku, M. Tsuchiya, K. Ishimaru, and T. Kojima
The TG analyses are given for variously meta- and/or para-linked aromatic polyamides with various benzimidazolyl (BI)contents.
The TG curves of the polymers were evaluated within 600C by use of an equation for multiple events. The TG curves of BI-substituted
polymers are expressed for triple events, though the TG curves of unsubstituted polymer are expressed for double events. The
amount of residue of BI-substituted polymers at 800C is larger than that of unsubstituted polymers, perhaps because moieties
concerning BI degrade at higher temperatures.
Authors:H. Abematsu, M. Tsuchiya, Y. Iseri, and T. Kojima
The TG studies are presented for isomers of benzimidazolyl-substituted polyamides (BIPA). The TG data are compared with those
polyamides (PA) of identical backbones without substitution, in view of the mechanism of thermal degradation. The TG mass
loss curves divided to three temperature ranges reflect the decomposition reactions in the respective temperature ranges:
(1) cleavage of single bonds of nitrogen to aromatic ring, (2) random scission of single bonds, (3) condensation of the remained
rings. Liberation of benzimidazole rings occurs in the temperature range (2). The final product, char, contains benzimidazole
rings. Terephthaloyl-rich BIPA's retard liberation of benzimidazole from the decomposed polymer.