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Journal of Thermal Analysis and Calorimetry
Authors:
E. T. Stepkowska
,
J. M. Blanes
,
A. Justo
,
M. A. Aviles
, and
J. L. Perez-Rodriguez

Summary Two hydrated and aged cement pastes from India (NCB), w/c=0.4, of a similar chemical composition but of a different specific surface and different strength (OPC, C-33 and C-43), hydrated at w/c=0.4 for 1 month, were studied by XRD after 1 year and 5-6 year ageing on contact with air. They were tested by static heating (SH) in fresh state, and by DTA/DTG/TG, IR and mass spectrometry (MS), after ageing, presented elsewhere. The main XRD peaks of (i) portlandite were decreasing with T and disappearing about 450°C, (ii) calcite peak at room T was small and broad, it increased gradually, especially after portlandite disappearance; above 600°C it was lowered and it was lost above 700°C. Important variation in the d(001) of portlandite with ageing was observed, exceeding the standard value of d(001)=4.895 Å (72-0156). It was higher in the paste C-33 (4.925-4.936 Å), containing more carbonates, than in the paste C-43 (4.916-4.927 Å). Small variations only were found in the value of d(101), i.e. 2.627-2.635 Å (nominally 2.622 Å), whereas the d(104) of calcite could be used as internal standard and other calcium carbonates (vaterite and aragonite) showed a small variation only. The increase ind(hkl) with temperature was straight linear (in portlandite ?d(001)=0.095 Å, at 30-400°C) and the thermal expansion coefficient estimated thereform was high (4.75-4.95·10-5 K-1). Close to the T of decomposition the ?d/?T became steeper. The thermal variation of d(104)=3.035 Å of calcite (?d=0.015 Å at 30-400°C) was smaller than that ofd(101) of portlandite (?d=0.025 Å at 30-400°C) and was similar in C-33 and C-43. The thermal expansion coefficient was 1.54 10-5 K-1, thus higher than the reported aa=0.65·10-5 K-1.

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Journal of Thermal Analysis and Calorimetry
Authors:
L. E. Garcia-Megias
,
E. Colacio-Rodriguez
,
A. Garcia-Rodriguez
,
J. Ruiz-Sanchez
, and
J. M. Salas-Peregrin

The thermal behaviour of 6-amino-5-formyluracil (HFU), 6-amino-1-methyl-5-formyluracil (1-MFU), 6-amino-3-methyl-5-formyluracil (3-HFU) and 6-amino-1,3-dimethyl-5-formyluracil (HDFU) is described. Only HDFU is shown to contain crystallization water. Dehydration and fusion enthalpy values have been calculated from the DSC curves. Likewise, the thermal behaviour of new complexes obtained by reaction between the above pyrimidine derivatives and Ni(II), Cu(II) and Pd(II) ions is reported.

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Journal of Thermal Analysis and Calorimetry
Authors:
J. Galán
,
J. Del Castillo
,
A. González-Pérez
,
V. Fuentes-Vázquez
, and
J. Rodríguez

Abstract  

The specific conductivities of dodecylpyridinium chloride have been determinated in water-butanol/pentanol/hexanol solutions in the temperature range of 10 to 35C, and butanol, pentanol and hexanol concentrations up to 0.05 mol kg–1. From these data the temperature dependence of the critical micelle concentration, (cmc), was determined. The molar fraction of alcohol in the micelle was estimated using the theory suggested by Motomura et al. for surfactant binary mixtures. The standard Gibbs free energy of solubilization of alcohols in the micelles was worked out using the phase separation model.

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Journal of Thermal Analysis and Calorimetry
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).

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Abstract  

We have studied the synthesis of polypyrrole-clay nanocomposites by the in situ oxidative polymerization of pyrrole in the interlayer space of vermiculites with different layer charges from Santa Olalla and Ojén, Spain. Moreover, the influence of different interlayer cations (Na+, Mg2+, Fe3+) on the interaction between pyrrole and the vermiculties was studied. The resulting materials were characterized by means of DTA-TG, XRD, FTIR and Mössbauer spectroscopy. In all samples polymerization of pyrrole was observed, presumably triggered by the structural iron. In most cases it was found to be externally deposited. An uptake of pyrrole in the interlayer space and PPy formation is observed in the case of the Fe3+-intercalated Ojén vermiculite, which has a lower layer charge than the Santa Olalla vermiculite.

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Journal of Thermal Analysis and Calorimetry
Authors:
M. Franquelo
,
M. Robador
,
V. Ramírez-Valle
,
A. Durán
,
M. Jiménez de Haro
, and
J. Pérez-Rodríguez

Abstract  

Roman ceramics of two hydraulic mortars used to build the pond and water channel of Mithraeum house from Mérida (Spain) have been studied. The sizes of the ceramic fragments found were different in both of the samples studied, showing different behaviour in the reactions with the lime. The X-ray diffraction of the ceramic shows the presence of quartz, mica (biotite), anorthite and hematite accompanied by amorphous phase, being observed scarce vitrification. The presence of mica confirms a firing temperature for manufacturing the ceramic below 900°C. In one of the ceramics studied, X-ray diffraction did not show calcite. However, in the FTIR appear bands that could be assigned to carbonates absorptions and likewise, carbonates were identified in the DTA-TG curves. Ca and small quantities of Si and Al were also identified by SEM-EDX on the surface of the pores that could be due to an amorphous phase formed in the reaction of lime with the Si and Al of the ceramic. On the other hand, in other ceramic samples carbonates (about 10%) were detected. The carbonates have been found filling the pores, sometimes accompanied by a new calcium-aluminium-silicate phase produced by the reaction between the lime and the amorphous phase of the ceramic. The carbonates and the new phases formed inside the pores are responsible for the decrease of the porosity and for the formation of new phases during the heating of the ceramics.

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Summary  

The differences on the thermal behaviour (DTG-DTA) of antigorite sample measured before and after sonication have been studied. Sonication treatment produces negligible changes in the structure of the material but substantial textural modifications. These modifications produce changes in the thermal behaviour of antigorite sample. Thus, it has been observed a decrease in the dehydroxylation temperature as measured by DTG and DTA effects. For sonication treatments longer than 20 h, two new effects of dehydroxylation are observed, the intensity of these two new effects increases with the sonication time showing a modification in the release of structural OH. It has been also observed that the formation of forsterite takes place simultaneously with the dehydroxylation of the antigorite. The high temperature exothermic effect is due to the recrystallization of forsterite and not to the formation of forsterite as traditionally assumed. Modifications in the thermal dehydroxylation of antigorite observed in this study are related to the pronounced decrease in particle size obtained by sonication.

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Journal of Thermal Analysis and Calorimetry
Authors:
L. Núñez-Regueira
,
J. A. Rodríguez-Añón
,
J. Proupín-Castiñeiras
, and
O. Núñez-Fernández

Summary Soil productivity and health were analyzed using an experimental procedure designed for this kind of studies. The continuous loss of fertile soil obliged the Food and Agriculture Organization (FAO) to declare soil as an item to be protected as a support of the world society welfare. The procedure here described is in accordance with the premises necessary for a rational and sustainable development of soil and the resources it contains and can be used to study any soil all over the world. The study was carried out using soil microbial population as a bioindicator of soil health. Microbial activity was followed using the microcalorimetric technique. The microcalorimetric study can be complemented through a deep analysis of soil physical, chemical and biological properties together with a study of the environmental properties that have a strong influence on the afore mentioned properties and, thus on the microbial activity in soil. The different properties follow different ASTM, ISS/FAO, USDA, etc. well defined standards. The experimental procedure reported in this work could be very helpful to create a data basis that could be useful to quantify and control soil potentiality or design soil decontamination and recovery systems.

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Journal of Thermal Analysis and Calorimetry
Authors:
E. Stepkowska
,
J. Bijen
,
J. Perez-Rodriguez
,
A. Justo
,
P. Sanchez-Soto
, and
M. Aviles

Abstract  

A simple water sorption/retention (WS/WR) test, followed by stepwise static heating, was applied to the study of cement quality and the reactivity of its grain surface. The physically bound water and hence the specific surface both in the unhydrated and in the hydrated state were estimated as a function of the hydration time. Rehydration after heating at 220°C and contact with air was different inWS from that inWR samples, which indicates a difference in microstructure. XRD proved the formation of portlandite during the sorption test and eventual heating at 200°C, and its transformation into carbonates on contact with air, especially on heating at 400°C. The contents of these compounds were estimated from the mass difference between 400 and 800°C, which was compatible with the mass change between 220 and 400°C and this indicates surface reactivity. The test may serve for the routine study of cement.

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