The decomposition processes of a carburised Fe–C alloy, a Fe–C, a Fe–Cr–C and commercial SAE 52100 cast alloys (with a C content
of about 1 mass%) have been studied by means of differential scanning calorimetry and dilatometry. The combination of these
two experimental techniques is very powerful and allows the identification of all the stages occurring during tempering. Activation
energies have been obtained by performing a Kissinger-like analysis and were used to infer the rate-determining step for each
stage of decomposition. This parallel investigation allowed to determine the effect of the alloying elements on the different
stages of tempering.
Authors:G. Baert, S. Hoste, G. De Schutter, and N. De Belie
Four paste mixtures with varying replacement level of the cement content by fly ash have been studied. Due to fly ash, the
acceleration period decreased and a third hydration peak was noticed with isothermal calorimetry. The total heat after 7 days
increased with increasing fly ash content. From 1 to 7 days, thermogravimetry showed a higher chemically bound water and Ca(OH)2-content for the pastes with fly ash. Between 7 and 14 days the calcium hydroxide started to be depleted due to the pozzolanic
reaction. A unique relation was found between calcium hydroxide and total heat development.
After a short survey of the development of adsorption calorimetry, the current position of this method is demonstrated in the light of some more recent results. A critical analysis is made of the areas in which adsorption calorimetry could be successfully applied in the future, either alone or, preferably, in combination with other techniques.
Authors:L. Bernazzani, C. Cardelli, G. Conti, and P. Gianni
The miscibility of blends of poly(vinyl-chloride) (PVC) with poly(ethylene-co-vinyl acetate) (EVA) was investigated through analog calorimetry and a group contribution procedure based on the UNIQUAC
model. The group contribution parameters quantifying the pair interactions between the structural features of the above polymers
were calculated from experimental excess enthalpies of a series of binary mixtures of chlorocompounds, esters and hydrocarbons.
Enthalpy data were also collected for the ternary mixtures (2-chloropropane+ethyl acetate+n-heptane) and (2-chlorobutane + methyl acetate+n-heptane), chosen as possible models for the studied macromolecular mixtures. The miscibility window of the PVC-EVA blends
is fairly predicted by the group contribution method. It is also acceptably predicted by the enthalpic behaviour of the first
ternary set, but only when the latter is calculated with binary data. A slightly narrower miscibility range is predicted by
the binary interaction model. The results of these procedures are compared and the higher reliability of the group contribution
procedure is emphasized in terms of its capability to reproduce the exact structure of the macromolecules and the non-univocal
choice of the model molecules involved in the analog calorimetry approach.
Authors:O. Elmokhtar, H. Said, M. Michel, M. Ganteaume, and R. Castanet
We report in this paper the results of our thermal and thermodynamic investigation on lithium cyclohexaphosphate, Li6P6O18·5H2O between 298 and 1007 K. The different transitions with respect to temperature (successive dehydrations, solid-solid transition
and melting) were studied with the help of differential thermal analysis and thermogravimetry. The different phases were characterized
by X-ray diffraction and by infrared absorption. Finally, the enthalpy of these phasesvs. temperature was measured by isothermal drop calorimetry. Their heat capacities as well as the enthalpies of dehydration,
of solid-solid transition and of melting were deduced.
We pointed out that the lithium cyclohexaphosphate loses a molecule of water at 333 K (54.3 kJ·mol−1), three molecules of water at 413 K (151 kJ·mol−1) and the last one at 488 K (50.6 kJ·mol−1). The anhydrous lithium cyclohexaphosphate, Li6P6O18, give the polyphosphate, LiPO3, at 708 K (second order transition) and melt at 933 K (24.6 kJ·mol−1).
Authors:Hideki Saitoh, Satoaki Ikeuchi, and Kazuya Saito
Summary Crystal structures of the room-temperature (RT) and low-temperature (LT) phases of p-methylbenzyl alcohol were reexamined by single-crystal X-ray diffraction method while paying special attention to detect structural disorder in the RT phase involved in successive structural phase transitions at 179 and 210 K. In the RT phase at 250 K, positional disorder of oxygen atoms was detected in contrast to the previous structure report. The structure of the LT phase coincided to the previous one. Heat capacities were measured by adiabatic calorimetry below 350 K, which covers the structural phase transitions and fusion at 331.87 K. The structural phase transitions were of first-order and required long time for completion. The combined magnitude of entropies of transition was ca. 5 J K-1 mol-1, a part of which can be ascribed to the positional disorder observed in the structure analysis. Standard thermodynamic functions are tabulated below 350 K.
Authors:E. Schmolz, S. Geisenheyner, B. Schricker, and I. Lamprecht
Heat production rates and flight speed of adult wax moths (Galleria mellonella) were investigated by means of direct calorimetry
at TA=20 and 30C. Specific heat production rates were not significantly different between males and females at TA=20C (pTH=747123.7 mW g-1, n=5 for males and pTH=791169 mW g-1, n=5 for females) even with females having a higher body mass (MB=83.821.6 mg, n=9 for males and MB=146.425.7 mg, n=11 for females) and wing load. In females, heat production rates were dependent on temperature with higher
heat production rates at TA=20C (pTH=791169 mW g-1, n=5) than at TA=30C (pTH=44174 mW g-1, n=6). Flight speed was also clearly correlated with TA. Both males and females flew more slowly at TA=20 than at 30C.
The response of temperature-modulated differential scanning calorimetry (TMDSC) to irreversible crystallization of linear polymers was investigated by model calculations and compared to a number of measurements. Four different exotherms were added to a typical modulated, reversible heat-flow rate in order to simulate irreversible crystallization. It was found that the reversing heat-flow rate of the TMDSC in response to such irreversible crystallization exotherms is strongly affected by tbe shape of the transition and the phase-angle where the exotherm occurs. A comparison with the experimental data gave valuable insight into the transitions, as well as the nature of the TMDSC response which is usually limited to an analysis of the first harmonic term of the Fourier series that describes the heat-flow rate.
Confinement of the glass-forming regions in the nanometer range influences the α-relaxation which is associated with the glass transition. These effects were investigated for semicrystalline poly(ethylene terephthalate) by dielectric spectroscopy and differential scanning calorimetry. The results are discussed within the concept of cooperative length, i.e. the characteristic length of the cooperative process of glass transition. Both experiments showed a dependence of the glass transition on the mean thickness of the amorphous layers. For the dielectric relaxation, the loss maximum was found to shift to higher temperatures with decreasing thickness of the amorphous layers, but no differences were observed in the curve shape for the differently crystallized samples. For the calorimetric measurements, in contrast, there was no correlation for the glass transition temperature, whereas the curve shape did correlate with the layer thickness of the mobile amorphous fraction. From the structure parameters, a characteristic length of approximately (2.5±1) nm was estimated for the unconfined glass relaxation (transition).
Authors:S. Aubuchon, L. Thomas, W. Theuerl, and H. Renner
40% w/w sucrose/water solutions were analyzed by Modulated Differential Scanning Calorimetry  in the sub-ambient temperature region. At these temperatures, the solutions exhibit a complex, two-step thermal event. The lower-temperature event is believed to be the glass transition of the amorphous sucrose phase. The nature of the higher-temperature event is the subject of controversy. This event has been shown to have distinct second-order characteristics, and as such is believed to be a second Tg. Others feel that this event is the onset of melting. The temperature region between these events contains a devitrification exotherm. Through the use of MDSC, both in scanning and stepwise quasi-isothermal modes, improved sensitivity and resolution of MDSC provides new insight into the nature of these transitions.