Materials with high surface areas and small particle size (nanophases), metastable polymorphs, and hydrated oxides are increasingly important in both materials and environmental science. Using modifications of oxide melt solution calorimetry, we have developed techniques to study the energetics of such oxides and oxyhydroxides, and to separate the effects of polymorphism, chemical variation, high surface area, and hydration. Several generalizations begin to emerge from these studies. The energy differences among different polymorphs (e.g., various zeolite frameworks, the - and -alumina polymorphs, manganese and iron oxides and oxyhydroxides) tend to be small, often barely more than thermal energy under conditions of synthesis. Much larger contributions to the energetics come from oxidation-reduction reactions and charge-coupled substitutions involving the ions of basic oxides (e.g., K and Ba). The thermodynamics of hydration involve closely balanced negative enthalpies and negative entropies and are very dependent on the particular framework and cage or tunnel geometry.
Authors:M. Angiuli, C. Ferrari, L. Lepori, E. Matteoli, G. Salvetti, E. Tombari, A. Banti, and N. Minnaja
Extra Virgin olive oils
(7 samples) originating from different areas of Tuscany, defective olive oils
(5 samples), commercial edible seed oils (4 samples) and two commercial samples
of olive oil (one declared ‘extra virgin olive oil’ and one ‘olive
oil’) were studied by different calorimetric techniques: high sensitivity
isothermal, differential scanning, and modulated scanning calorimetry. The
temperature interval (–60) – (+30)C was explored for monitoring: i) the main features of the liquid↔solid phase
transitions, ii) the nucleation and growth
rate of the polymorphous crystalline phases of the triacylglicerols, and iii) the melting process. This investigation was
planned for verifying the utility and effectiveness of calorimetry for screening
quality and origin of olive oil. To this end, the main calorimetric operation
modes have been applied, the experimental results reported and their utility
for developing an effective and reliable screening protocol discussed.
Authors:L. Núñez-Regueira, J. Rodríguez-Añón, J. Proupín-Castiñeiras, and C. Labarta-Carreño
This paper shows an application of bomb calorimetry used in the procedure of regeneration of waste industrial mineral oils.
Using the treatment here reported a recovery of nearly 50% of the used oils was achieved. Furthermore, the oils so recovered
contain concentrations of potentially contaminant elements far below the requirements of the European Union (EU). Generally
speaking, it can be said that the used oil treatment is based on the proper combination of two main procedures, namely the
addition and mixture of certain chemicals-precipitant, flocculant and demulsifying agents- in a permanently stirred reactor,
at high temperature, and the centrifugation of the mixture. This oil, recovered through the technique of oil regenerating,
cleaning, and fitness, can be used either as a raw material for the elaboration of new oils or as a fuel to be used for cogeneration
of thermal or electric energy. The treatment described is highly remunerative, both as regards to cost -used oil is subject
to a low-cost process, especially if compared to its elaboration from raw materials- and as regards to ecology, since it is
recycled, thus saving a great amount of raw materials.
A procedure is described for dealing with the error sources inherently present in any real calorimeter: work of powerPs input from stirrer and possibly temperature sensor, and heat exchange at a rate −G(T−Te) whereT andTc are the temperatures of calorimeter and surroundings respectively. The constantsPs andG are calculated from a period of thermal decay, and afterwards are used to correct the entire run. A calorimeter was designed
with high thermal homogeneity and used in a test. The curve of calculated temperature exactly traces the heater energy, even
after 5 h, with a standard deviation of about 1 mK. The relative error inCp is less than 1/1000.
Classical adiabatic methods for measuring specific heat in a wide temperature range are very suitable for homogeneous, well
defined materials. However, measurements on inhomogeneous materials require large samples, which makes using of adiabatic
treatments extremely expensive. In this paper, a nonadiabatic method for determining the specific heat of inhomogeneous building
materials within the wide temperature range of −30 to 1200°C is presented. The method is relatively simple, very cheap, and
sufficiently accurate for use with building materials. Tests of the new developed method on two typical building materials,
concrete and basalt fibreboards, demonstrate the method's applicability to practical measurements.
Authors:B. Wunderlich, A. Boller, I. Okazaki, and S. Kreitmeier
Temperature-modulated differential scanning calorimetry (TMDSC) is based on heat flow and represents a linear system for the measurement of heat capacity. As long as the measurements are carried out close to steady state and only a negligible temperature gradient exists within the sample, quantitative data can be gathered as a function of modulation frequency. Applied to the glass transition, such measurements permit the determination the kinetic parameters of the material. Based on either the hole theory of liquids or irreversible thermodynamics, the necessary equations are derived to describe the apparent heat capacity as a function of frequency.
In this work two aluminic pozzolans (metakaolins) and a non-pozzolan were added to two Portland cements with very different
mineral composition, to determine the effect on the rate of heat release and the mechanisms involved. The main analytical
techniques deployed were: conduction calorimetry, pozzolanicity and XRD.
The results showed that the two metakaolins induced stimulation of the hydration reactions due to the generation of pozzolanic
activity at very early stage, because of their reactive alumina, Al2O3r− contents, mainly. Such stimulation was found to be more specific than generic for more intense C3A hydration than C3S, at least at very early on into the reaction, and more so when 7.0% SO3 was added, and for this reason, such stimulation is described as ‘indirect’ to differentiate it from the ‘direct’ variety.
As a result of both stimulations, the heat of hydration released is easy to assimilate to a Synergistic Calorific Effect.
Modulated differential scanning calorimetry (MDSC) uses an abbreviated Fourier transformation ≼r the data analysis and separation of the reversing component of the heat flow and temperature signals. In this paper a simple spread-sheet analysis will be presented that can be used to better understand and explore the effects observed in MDSC and their link to actual changes in the instrument and sample. The analysis assumes that instrument lags and other kinetic effects are either avoided or corrected for.
Authors:L. Núñez-Regueira, J. A. Rodríguez-Añón, J. Proupín, B. Mouriño, and R. Artiaga-Diaz
Summary The European policy on energy focus on the search for alternative and renewable sources of energy where forest biomass plays a significant role. In this article, calorific values of different kinds of forest residues (leaves, thin branches, barks, etc.) are reported. These values were measured by combustion bomb calorimetry with the objective of understanding, through different risk indices, the behaviour of forest waste in the case of wildfires, and also to study the use of forest residues as raw materials to be used as energy sources. The study was complemented with determination of elemental analysis, flammability using a standard epiradiator, thermodegradation analysis, and different mechanical tests trying to get relationships between thermal behaviour and some physical properties. The study was carried out on Eucalyptus globulus Labill and Pinus pinaster Aiton, because these forest formations have both high economical and ecological interest in Galicia (NW Spain).