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  • Author or Editor: C. Tomasi x
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Abstract  

An archaeometric investigation on plaster samples taken from the cellars of the Visconti Castle in Pavia has brought out the existence of several layers and colour films of various periods. The oldest plaster spread over the masonry is formed with three main layers. Above them, one film of bluish-black colour can be found on the arcs and on the bearing walls. On this black layer, a white film of calcitic composition, containing also apatite fragments, was spread. These ancient materials were subsequently covered in more recent times with plasters having different compositions and textures. In the present paper the properties of the three main plaster layers and those of the black film are reported in detail. The thermal behaviour of these materials was studied by means of differential thermal analysis and thermogravimetric analysis. The study was completed with scanning electron microscopy,microprobe analysis and X-ray diffraction on powders. The results obtained provide interesting clues for advancing reasonable hypotheses both on the methods adopted in ancient building yards, and on the techniques for the production of the pigments employed.

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Abstract  

Plasters and mortars taken from the walls of the ancient hospital ‘San Matteo’ of Pavia (Italy), were investigated with thermal and other techniques. From the data collected, two groups of materials were brought out: the first one, containing the plasters, is remarkably richer in calcite than the second group, formed by the mortars. These findings allow one to relate these groups to two historical periods: the middle of the XV century, and the end of the XVIII century. Some hypotheses may also be made on the compositions of the binding/inert fractions adopted in preparing these materials in the building yards of the two periods.

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Poly(ethylene oxide) (PEO) based-polymeric solid electrolytes are of growing interest for their applications in electrochemical devices. Their major limitations are structural and electrochemical stability, and low cationic transport number. A possible response to these problems is given by composite or nanostructured materials. We present sol-gel synthesis, thermal and electrical characterization of new electrolytes made of a composite glass-polymer matrix doped with LiClO4 and LiBF4. Emphasis to the critical aspects of preparation is given. We obtain a conductivity at room temperature better than 10−5 ohm−1 cm−1, which is high enough to envisage technological applications.

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Journal of Thermal Analysis and Calorimetry
Authors:
C. Tomasi
,
M. Scavini
,
A. Speghini
,
M. Bettinelli
, and
M. Riccardi

Abstract  

The devitrification of glassy PbGeO3 was studied and interpreted by means of isothermal and non-isothermal Johnson-Mehl-Avrami equations. In the case of the non-isothermal approach, several approximated equations proposed by various authors were considered in order to obtain both the activation energy E a and the Avrami morphological coefficient n of the crystallisation process. A critical discussion of the Avrami coefficient on the basis of experimental morphological evidence is also presented.

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The formation of the Ba(CuOx)1−y(CO3)y

A new phase in the Ba-Cu-C-O system: thermal analysis results

Journal of Thermal Analysis and Calorimetry
Authors:
A. Tomasi
,
P. Scardi
,
F. C. Matacotta
, and
P. Nozar

Carbocuprate compounds are generally described as multiple perovskites with CO3 2- and Cu-O alternating layers containing Ba and/or Sr; they have gained an unexpected importance in the high temperature superconductivity field, because many compounds with transition temperature above 100 K belong to this class of materials.

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