A photopyroelectric technique has been used to simultaneously measure the critical behavior of specific heat, thermal conductivity, and diffusivity ${\mathrm{Cr}}_{2}$${\mathrm{O}}_{3}$ at antiferromagnetic-paramagnetic phase transition. An Ising-like found for \ensuremath{\Vert}${\mathit{t}}_{\mathrm{max}}$\ensuremath{\Vert}\ensuremath{\le}3\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}3}$ with \ensuremath{\alpha}=0.10\ifmmode\pm\else\textpm\fi{}0.02...

The thermal conductivity and the diffusivity of aligned $n\mathrm{CB}$ samples $(n=5,\dots{},9)$ has been measured with a photopyroelectric technique. An odd-even effect found in values these two quantities for homeotropic increasing $n.$ results can be interpreted terms model proposed by Urbach, Hervet, Rondelez. This model, which takes into account not only geometrical dimensions liquid crystal molecules but also their average mutual distances, used to observed anisotropy diffusivity.

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

The ability of disorder to reduce the coupling between distortion and tilt angle order parameters was tested over R(I)-R(V) phase transition by measuring specific heat in alkanes with different R(I) temperature range mixed various concentrations silica nanoparticles. It found that significantly affects character transition, driving it toward a second-order character. features about R(II)-R(I) were progressively attenuated for increasing both alkanes, becoming very faint largest particle...

Abstract We present an opto-thermal approach based on the use of active infrared thermography (IRT) for study texts hidden inside bookbinding structure ancient books. In particular we focus our investigation detection and characterization paper scraps, belonging to earlier handwritten or printed leaves, used making bookbindings lying between end papers cover. A qualitative description physical mechanisms allowing identification is proposed a comparative analysis results obtained by means...

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

The critical behavior of the specific heat, thermal conductivity, and diffusivity at smectic-A--nematic phase transition aligned octylcyanobiphenyl (8CB) has been studied with photopyroelectric technique. Though values transport parameters are substantially different for homeotropic planar alignment, it shown that is characterized by same exponent in two cases. This result suggests mode couplings govern dynamics associated isotropic. conductivity remains flat, only a minor increase close to...

The smecticA-hexaticB phase transition was studied in a homeotropic single domain sample and non-aligned of n-hexyl-4'-n-pentyloxybiphenyl-4-carboxylate liquid crystal compound to probe the effect different amount defects on transition. specific heat, thermal diffusivity enthalpy exchange were monitored over and, at same time, polarization microscopy observations could be carried out. during first cooling run found accompanied by considerably larger defect annealing than one, but critical...

The values of the thermal conductivity and optical absorption coefficient ion implanted Si GaAs have been measured in a nondestructive way by photoacoustic measurements. obtained for are good agreement with those found literature, while no data as function ions dose. value layers is more than two orders magnitude lower ones respective crystalline material. dose dependence parameters reported GaAs.

Photopyroelectric high resolution ac calorimetry has been used to study the nematic-isotropic phase transition in octylcyanobiphenyl liquid crystal incorporating an aerosil soft gel. We have found that sample is not thermodynamic equilibrium two coexistence region, as shown by frequency dependence of double peak specific heat and its thermal hysteresis. The results suggest dynamics system becomes slower it cooled over temperature. An explanation for formation a nematic glassy crystals with...

By means of specific heat spectroscopy, we have studied the dynamics nematic 8CB nucleated, in presence random disorder, as temperature is lowered across isotropic to phase transition such that crossover region dilution field regimes disorder strength explored. We show, terms frequency dependence, hysteretic behavior, and aging effects, out-of-equilibrium properties nucleated regime are strongly reminiscent bulk material while one grown shows a glassy behavior with leading slower dynamics....

High temperature resolution measurements of thermal conductivity, diffusivity, and specific heat, with simultaneous polarized light visual inspection the sample, have been performed at two different liquid crystal phase transitions: SmA-SmC (Smectic-A-Smectic-C) SmA-HexB (Smectic-A-hexatic-B) in racemic A7 [4-(3-methyl-2-chlorobutanoyloxy)-4(')-heptyloxybiphenyl] 65OBC (n-hexyl-4(')-n-pentyloxybiphenyl-4-carboxylate) compounds, respectively. In past, anomalies conductivity transitions...

The photopyroelectric technique has been used to study the specific heat, thermal conductivity, and diffusivity at smectic-$A$--nematic phase transition of homeotropic planar samples 4-$n$${\ensuremath{-}\mathrm{p}\mathrm{e}\mathrm{n}\mathrm{t}\mathrm{y}\mathrm{l}\mathrm{p}\mathrm{h}\mathrm{e}\mathrm{n}\mathrm{y}\mathrm{l}\mathrm{t}\mathrm{h}\mathrm{i}\mathrm{o}\mathrm{l}\ensuremath{-}4}^{\ensuremath{'}}$-$n$-octyloxythiolbenzoate (8\ifmmode\bar\else\textasciimacron\fi{}S5)...

Photopyroelectric measurements of the anisotropy in thermal conductivity $\ensuremath{\Delta}k$ vs temperature $n\mathrm{CB}$ $(n=5,\dots{},9)$ series are reported. The data have been used to deduce behavior orientational order parameter Q close nematic-isotropic $(N\ensuremath{-}I)$ and smectic A--nematic $(A\ensuremath{-}N)$ phase transitions, respectively. It has shown that near $N\ensuremath{-}I$ transition for 5CB 6CB consistent with so-called ``tricritical hypothesis,'' which predicts...

A photopyroelectric study of the specific heat and thermal conductivity small quartz sphere (aerosil) dispersions in heptylcyanobiphenyl (7CB) octylcyanobiphenyl (8CB) liquid crystals with a concentration rho(s)=0.005 g cm(-3) is reported. The data show that, even at this low concentration, elastic strain introduced crystal by aerosil particle not completely annealed nematic-isotropic (NI) phase transition. In 8CB, annealing has been found smectic-nematic transition, while case 7CB it occurs...

We have studied the hexatic-$B$--smectic-$A$ $(\mathrm{Hex}B\text{\ensuremath{-}}\mathrm{Sm}A)$ transition in $n$-hexyl-${4}^{\ensuremath{'}}\text{\ensuremath{-}}n$-pentyloxybiphenyl-4-carboxylate (65OBC) by means of a high-resolution ac photopyroelectric (PPE) calorimetric technique. A procedure for interpretation PPE data, which allows detection an internal heating source due to strain annealing and/or latent heat, has been applied. found that present sample depends on kinetics formation...

We have studied the specific heat and thermal conductivity in a 4-(n-octyl)-4'-cyanobiphenyl liquid crystal (LC)-photochromic molecules mixture, before, during, after photo-activation of dispersed photochromic molecules, over both smectic A-nematic nematic-isotropic phase transitions. The evaluation has enabled determination changes transition characteristics induced by photoisomerization, while that could be used to monitor modifications average LC molecular orientation. polarization...