M. Marinelli

Simultaneous determination of specific heat, thermal conductivity and thermal diffusivity at low temperature via the photopyroelectric technique

The photopyroelectric effect has been used to measure simultaneously specific heat (c), thermal conductivity (k) and thermal diffusivity (α) at low temperatures. A calibration procedure which allows the use of a pyroelectric transducer at low temperatures is described. Simultaneous measurements of c, k, and α over a high Tc superconducting phase transition are reported.

Optically induced reorientational birefringence in an artificial anisotropic Kerr medium

Abstract A laser induced optical birefringence has been obtained for the first time in an anisotropic artificial Kerr medium. This consists of an aqueous suspension of dielectric microellipsoids which reorientate under electromagnetic and brownian torques. The measured effective optical Kerr coefficients, n 2 , is 4.0x10 -4 cm 2 /MW while the response time is 2.6 ms. These values agree with the ones obtained from a simple Debye model assuming rigid anisotropic rotors in a statistical environment.

Hidden Text Detection by Infrared Thermography / Anwendung der aktiven Infrarotthermographie (IRT) zur Erfassung von verdeckten Texten / Utilisation de la thermographie infrarouge (IRT) pour détecter des textes cachés

Abstract We present an opto-thermal approach based on the use of active infrared thermography (IRT) for the study of texts hidden inside the bookbinding structure of ancient books. In particular we focus our investigation on the detection and characterization of texts on paper scraps, belonging to earlier handwritten or printed leaves, used for the making of bookbindings and lying between the end papers and the cover. A qualitative description of the physical mechanisms allowing the identification of texts is proposed and a comparative analysis of the results obtained by means of different IRT experimental configurations is presented. The results show that active IRT can be a very useful tool for the detection and the identification of underlying texts whose reading can provide useful information on the specific history of ancient books. Zusammenfassung Die Anwendung von aktiver Infrarotthermographie (IRT) zur Erfassung von Texten, die in Einbandstrukturen verborgen sind, wird vorgestellt. Insbesondere wurden Texte auf Fragmenten, die fur die Buchdeckenherstellung verwendet wurden, beziehungsweise sich zwischen Vorsatz und Buchdeckel befinden. Eine Beschreibung der physikalischen Grundlagen fur die Texterfassung mit IRT wird gegeben ebenso wie die Prasentation ausgewahlter Untersuchungen an historischen Objekten. Die prasentierten Resultate zeigen, dass aktive Infrarotthermographie eine geeignete Methode fur die Erfassung von verdeckten Textfragmenten darstellt und wichtige Informationen zur Geschichte historischer Bucher beziehungsweise Bucheinbande liefern kann. Résumé Nous présentons une approche qui se base sur l’utilisation active de la thermographie infrarouge (IRT) pour l’étude de textes cachés à l’intérieur de la structure reliée des livres anciens. L’examen s’est centre surtout sur la détection et la caractérisation de textes sur les fragments de papier provenant de feuilles écrites auparavant à la main ou imprimées et qui ont servi dans la fabrication des reliures et qui se trouvent entre les dernières feuilles de garde et la couverture des livres. On présentera une description des mécanismes physiques permettant l’identification des textes et une analyse comparative des résultats obtenus au moyen de différentes configurations expérimentales d’IRT. Les résultats présentés démontrent que La thermographie infrarouge active s’avère être un outil très utile dans la détection et la caractérisation de textes sous-jacents dont la lecture peut fournir de précieuses informations sur l’histoire spécifique de livres anciens.

Latent heat investigation by photopyroelectric calorimetry

We report on an approach for photopyroelectric calorimetry enabling a frequency dependence detection of the specific heat and of the latent heat exchanged over first order transitions. It has been applied to the nematic-isotropic transition of 4-n-octyl-4′-cyanobiphenyl liquid crystal confined in a silica nanoparticles network, where the specific heat shows a double peak structure. The larger strain involved with the nematic nucleating over the low temperature peak induces a considerable lower latent heat than the one involved over the higher temperature peak. The frequency dependent measurements have shown a different dynamics of the nematic nucleating over the two peaks.

Thermographic analysis of bronze sculptures

In this work we investigate various aspects of the finishing process in ancient bronze sculptures by means of active infrared thermography (IRT). Active IRT provides information on surface and sub-surface features of the investigated artefact, by analysing the heat diffusion process induced within the sample by appropriate thermal stimulations usually produced by absorption of light emitted by different sources. The aim of this research is, in particular, to investigate the processing of bronze surfaces, revealing repairs like plugs, fillings, local castings and concealed marks.

Surface states studies in semiconductors by photothermal deflection spectroscopy

A method based on the analysis of both the amplitude and phase of the photothermal deflection spectroscopy signal which enables one to locate surface states on the front or rear surface of semiconductor wafers and to measure their absorption. The procedure also allows the determination of the sample thermal conductivity.

Picosecond relaxation and thermal diffusion in amorphous silicon

We have studied the time‐resolved reflectivity changes in the picosecond–nanosecond range induced by picosecond visible optical pulses in ion‐implanted amorphous silicon‐on‐sapphire. Illumination from the front side of the thin film probes the picosecond carrier relaxation processes. Heat release from trapped carriers in the 100‐ps range is shown to be significant. Illumination from the substrate side probes, in addition, the ultrafast diffusion of heat to the substrate. The derived thermal diffusivity is shown to correspond to a near‐surface layer much thinner than the optical absorption depth.

Photothermal deflection spectroscopy study of defects in semi-insulating GaAs

Subgab absorption measurements carried out by photothermal deflection spectroscopy in semi-insulating GaAs are used to study the concentration of defects found in as-grown and in heat treated material. Measurements carried out in ion-implanted and furnace-annealed samples prove to be a useful tool for monitoring the successful recovery of the ion implantation damage.

Photoacoustic monitoring of damage in ion implanted and annealed si layers

The photoacoustic technique has been used to characterize ion implanted Si layers, as a function of the implantation conditions of ion dose and energy and of thermal annealing conditions, through the determination of the material thermal conductivity and optical absorption coefficient. It was found that the technique can discriminate between amorphous material obtained under different implantation conditions. Regarding the annealed samples, different results have been obtained for amorphous as-implanted, fine grain polycrystalline, highly defective single crystalline and defect-free single crystalline materials.

Active infrared thermography applied to the study of a painting on paper representing the Chigi's family tree

Abstract In this work, active infrared thermography was applied to study a seventeenth-century painting on paper, namely the Chigis family tree, housed at Palazzo Chigi in Ariccia (Rome). Thermography was performed before and after restoration to obtain information used in planning the restoration and also to assess its effectiveness. Infrared thermography provided important information on the artifact structure, areas of damage, structural defects, and the state of adhesion between different layers of the composite artifact before and after the treatment.