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© 2019, Akadémiai Kiadó, Budapest, Hungary. Low-temperature DSC on a wide range of opal-A and opal-CT samples was carried out to estimate the proportion of crystallisable water and to determine the size of water-filled cavities. A wide range of crystallisable water contents in the range 4.9 to 41.9% of the water contained in opals were observed, although the proportion of crystallisable water did not correlate with structure. Pore size and pore size distribution were estimated from the melt temperature depression and heat flow data, respectively. Opal-CT was observed to have smaller water-filled pores (radii < 2 nm) than opal-A (radii from 2.5 to 4.9 nm), suggesting that molecular water may be contained between nanograins in the microstructural units (spheres or lepispheres). A narrower pore size distribution was calculated for opal-CT, and no melting of the crystallisable water was observed where bulk water would be expected to melt, suggesting the absence of larger voids. The melting peaks for opal-A, on the other hand, transitioned into the melting of bulk water suggesting the presence of significantly larger water-filled pores, an observation consistent with the microstructure observed in SEM micrographs.

Samples of electrolytic manganese dioxide (EMD) were chemically reduced using 2-propanol under reflux (82°C) for 1, 2, 3, 6 and 24 h intervals. XRD analysis showed that the γ-MnO2 structure was preserved although the lattice dimensions were observed to increase with increasing degree of reduction to accommodate the intercalation of protons. The exception was the 24 h reduced sample which contained two phases; γ -MnO2 and γ -MnOOH. Three regions of decomposition in the range of 50 to 1000°C were observed using thermogravimetric analysis coupled with mass spectrometry (TG-MS) and were accounted for as water removal below 390°C, reduction of MnO2 to Mn2O3 between 400 and 600°C, and Mn2O3 to Mn3O4 between 600 and 1000°C. Again the exception proved to be the 24 h reduced sample which was observed to decompose predominantly in one step between 400 and 600°C directly to Mn3O4. © 2005 Akadémiai Kiadó Budapest.

The mechanism and stability of dimethylol urea (DMU) to polycondensation were investigated using thermogravimetric analysis coupled with mass spectroscopy (TG-MS) for evolved gas analysis and a non-isothermal model-free induction period kinetic analysis using three temperature functions; the Arrhenius function and two non-Arrhenian functions. The polycondensation was observed to occur through a two-step process of condensation followed by elimination of formaldehyde during structural rearrangement as has been reported in the literature. The rate equations for each temperature function were evaluated and extrapolated to room (23 °C) and refrigerator (4 °C) temperature to estimate the length of the induction period for the onset of polycondensation for storage life prediction. Based on experience, estimates of the length of the induction periods and, hence, storage life, were most realistically predicted by the non-Arrhenian temperature functions. © Akadémiai Kiadó, Budapest, Hungary 2011.

The deleterious interaction of some traditional sulphide artists pigments and copper ions results in the formation of black copper sulphides, in particular, covellite (CuS), and, hence, the discolouration of valuable artworks. In this paper the interaction of malachite, a source of copper(II) ions, with the pigment cadmium yellow, a sulphide pigment comprising of a solid solution of cadmium and zinc sulphides, is investigated by XRD and TG-MS. XRD showed the presence of the copper sulphide and cadmium carbonate phases, produced by a simple ion exchange mechanism. TG-MS showed the complexity of the range of metastable phases produced. The identification of these phases, however, requires further work. © Springer-Verlag 2007.

Cold pressed linseed oil and paints prepared using the inorganic pigments; lead white and red lead, were characterized using non-isothermal differential scanning calorimetry (DSC) in an air atmosphere to determine the effect of the pigment on the oxidative polymerisation of the drying oil medium. For each paint sample, the onset temperature for oxidation was reduced from 166°C to the range 50 to 60°C when a heating rate of 5 K min-1 was used. In order to determine the rate of drying, the non-isothermal experiments were carried out using a range of heating rates. A change in the mechanism oxidative polymerization was observed as the heating rate was increased. © 2005 Akadémiai Kiadó, Budapest.

The DSC characterisation of the morphology of the metastable a phase of stoichiometric nickel sulphide was carried out using two calorimeters; a TA Instruments 2920 MDSC and a Perkin Elmer DSC-7, and two quenching histories. Based on these quenching histories, significant differences were observed in the heat flow curves, including the observation of a second exothermic peak which is tentatively assigned to be a metastable phase to metastable phase transformation. The kinetic constants for the α to β recrystallisation were determined as a function of degree of conversion using a mechanism free isoconversional model. Variations in the values of the kinetic constants were also ascribed to the quenching histories. Although the differences in morphology observed were ascribed to the processing history, the shift in the position of the α to β recrystallisation peak was partially attributed to the thermal resistances of the instruments used.

Museum specimens of pyrite are known to undergo oxidation even during storage. Characterisation of the oxidation products is however not always simple due to amorphous character and varying degrees of hydration of the oxidation products, This paper presents an alternative approach to the characterisation of oxidation products by identifying their presence from their characteristic thermal decomposition processes using thermogravimetric and evolved gas analysis. Four pyrite specimens were characterised with varying degrees of oxidation. Iron(II) and iron(III) sulphates were also characterised for comparative purposes. The degradation products were observed to correlate well with the presence of iron(II) sulphate even though there was found to be some discrepancy in the higher temperature decomposition reactions.

An incremental integral isoconversional method for the determination of activation energy as a function of the extent of conversion is presented. The method is based on the treatment of experimental data without their transformation so that the resulting values of activation parameters should not be biased. The method was tested for recovering the activation energies from simulated data and employed for the treatment of experimental data of the NiS recrystallisation.

Compression moulded plaques of a range of poly(ether ether ketone) (PEEK)- poly(tetrafluoroethylene) (PTFE) blends (100, 92, 48, 29, 9.5 and 0 mass% PEEK) have been characterised using differential scanning calorimetry (DSC) and wide angle X-ray crystallography (WAXD). A shift in the melting peak of the PEEK phase from 347 to 358°C was observed with increasing proportion of PTFE in the blend. A narrowing of the melting range was also observed. Correspondingly, WAXD measurements showed a reduction in the d-spacings. The observed changes in morphology are rationalised in terms of a higher degree of order imparted on the PEEK crystalline phase by the transmission of an applied 'hydrostatic' pressure by the presence of the PTFE.

Naturally occurring opals from three different regions in Australia were studied for their thermal characteristics. All the opals showed initial expansion followed by contraction in thermomechanical analysis (TMA) although the temperature at which the change from expansion to contraction occurred depended on their provenance. Thermogravimetric analysis (TG) revealed different rates and temperatures of dehydration for these opals. A general correlation between the temperature at which there was a zero thermal expansion and that of the maximum rate of dehydration was observed. A dehydration-sintering mechanism is proposed with the effect of sintering being more pronounced following total dehydration.

The degradation of poly(vinyl alcohol) was investigated using TG analysis and Fourier transform infrared spectroscopy to determine the effect of atmosphere on the process of degradation. In the spectra, four vibrational modes were identified that characterised the major steps of the degradation process. These were the O-H, C-H, C=O and C=C stretching modes. The mechanism observed for degradation in an inert atmosphere was in accordance with the accepted mechanism of elimination followed by pyrolisation. Evidence of conjugated polyenes, however, was not observed. For the air atmosphere, oxidation in both steps of the degradation process was observed.

Toughened glass panels used as a glazing material in multistorey buildings are known to fracture prematurely when they contain nickel sulfide inclusions as a result of the α-β phase recrystallisation in nickel sulfide. The kinetics of this recrystallisation were studied by differential scanning calorimetry (DSC) under isothermal and non-isothermal conditions. The recrystallisation was observed to be a two-step process with an induction period followed by the phase change. A two-stage kinetic model was used to estimate the recrystallisation time under ambient conditions. These values were found to correlate well with the observed time to failure for glass panels installed in multistorey buildings.