C. Roldán

Characterization of cobalt pigments found in traditional Valencian ceramics by means of laser ablation-inductively coupled plasma mass spectrometry and portable X-ray fluorescence spectrometry

In this work, a comparison of the performances of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS) and portable X-ray fluorescence (XRF) spectrometry for the characterization of cobalt blue pigments used in the decoration of Valencian ceramics is presented. Qualitative data on the elemental composition of the blue pigments obtained using both techniques show a good agreement. Moreover, the results clearly illustrate that potters utilized different kinds of cobalt pigments in different historical periods. While both techniques seem suitable for the proposed task, they show different strengths and weaknesses. Portable X-ray fluorescence spectrometry is a cheaper and totally non-destructive technique, capable of providing fast and reliable results at the mgg(-1) level. LA-ICPMS, on the other hand, offers a much higher detection power and better spatial resolution, but its use results in some sample damage (sample consumption at the mug level), while it is a more expensive and non-portable technique.

Study of inks on paper engravings using portable EDXRF spectrometry

Abstract The prints are fragile and delicate art objects that need for its examination a suitable technique for “in situ”, non-destructive and rapid analyses. The energy dispersive X-ray Fluorescence (EDXRF) spectrometry with portable instrumentation offers these analytical properties. In this work we present the EDXRF analyses of eight engravings elaborated with different techniques (etching and heliogravure) from the 17th to 20th centuries. The characterization of the paper is directly done from its EDXRF spectra, whereas the inks are characterized by the ink plus paper analysis after subtracting the background from the paper spectrum. Inorganic components of the paper engravings and inks have been identified from the EDXRF spectra and the results are discussed. Also, we present EDXRF analyses for the identification of inorganic components from six samples of modern inks.

X-ray fluorescence analysis of yellow pigments in altarpieces by Valencian artists of the XV and XVI centuries

XRF analysis has allowed a quick and precise detection and identification of the inorganic elements that compose the yellow pigments in altarpieces of the XV and XVI centuries painted by the Valencian artists Miguel Alcaniz, Vicente Macip, Juan de Juanes, Hernando Yanez de la Almedina and Hernando Llanos. The analyses have been carried out with an XRF portable system that consists of a tube of X-rays and detectors of Si(Li) and cadmium zinc telluride. This system has enabled a non-aggressive and non-destructive analysis of many pieces at the Museo de Bellas Artes of Valencia (Spain). Among the yellow pigments we have identified a pigment composed by lead and tin oxides named lead–tin yellow (Pb2SnO4), frequently used in European paintings from the XIV century until the first half of the XVIII century. This fact demonstrates the influence of elements and pictorial techniques from Europe to the region of Valencia.

A Monte Carlo based method of including gamma self-absorption for the analysis of environmental samples

We propose a new method to calculate the full-energy-peak efficiency of Ge(Hp) detectors, including gamma self-absorption, using a Monte Carlo technique. We have studied several samples geometries, which are the most commonly used in environmental radioactivity, Petri vial and Marinelli beakers, supposing different densities for the material in the sample, between 0.4 and 1.6 g/cm3. For each geometry we have found an important change of self-absorption on density and we have calculated the dependence of full-energy-peak efficiency on sample density for a set of energies between 100 and 2000 keV.

Backscattering and self-absorption corrections in the measurement of alpha-emitters in 2π geometry

Abstract Monte Carlo simulation has been developed to model the slowing down and scattering of alpha particles in amorphous media so that corrections for backscattered and absorbed particles can be determined for 2π geometry measurements. These calculations are based on the total stopping powers and the Rutherford scattering law, and the resulting energy spectra are in good agreement with experimental measurements.

Monte Carlo simulation of alpha spectra in low-geometry measurements

Abstract Monte Carlo simulation of alpha spectra obtained with semiconductor detectors in low-geometry has been developed. The proposed method reproduces adequately experimental spectra of alpha emitters by taking into account the energy losses and trajectory changes of alpha particles as consequences of their interactions in the source, backing and detector.

One-neutron transfer contribution to the elastic 32 S+ 32S scattering at Einc = 91.3 MeV☆

Abstract The elastic scattering differential cross section for 32 S incident on 33 S at E inc = 91.3 MeV has been measured. The observed backward oscillations are successfully described by explicit inclusion of a parity-dependent term in the real potential for the optical-model calculations of the elastic scattering. To investigate possible sources of the parity-dependent term, the backward oscillations were also interpreted as being produced by the interference between the elastic amplitude and the one-neutron elastic one-step transfer process.

RHEOLOGICAL BEHAVIOUR OF MICROCRYSTALLINE CELLULOSE HYDROGELS

ABSTRACT An extensive study was made of the rheological behaviour of microcrystal1ine cellulose-sodium carboxymethyl cellulose (MCC-NaCMC) gels at six different concentrations. The effect of agitation time, storage time, shear rate and temperature on the viscosity of these thixotropic gels was analysed, over 7200 resulting values of being available to this effect The pseudoplastic and thixotropic characteristics of the gels was established and a progressive decrease in gel viscosity with increasing storage time was observed, although retaining stability. On the other hand, constant agitation for five minutes was found to reduce gel viscosity by 40 to 50%, regardless of concentration.

Applications of the X-ray fluorescence analysis to the cultural patrimony of the Comunidad Valenciana (Spain): Painting, metal and paper

We present examples of the application of the X-ray fluorescence (XRF) to the study of the artistic and cultural patrimony of the Comunidad Valenciana in the following areas: a) Valencian paintings of the XV and XVI centuries; b) silver ornaments coming from Iberian towns (s. III b.C.); c) ink and paper samples in manuscripts and engravings of the XVII and XIX centuries. The non destructive analyses are carried out “in situ” using a XRF system that consists of a tube of X-rays of 50 kV and 1 mA, and a detector of Si(Li) with an energy resolution 140 eV (FWHM at 5.9 keV).

Folding model analysis of 32S + 32S elastic scattering at 70, 90, 97.09, 120 and 160 MeV

Abstract Angular distributions for the 32 S( 32 S, 32 S) elastic scattering have been measured at 70, 90, 97.09, 120 and 160 MeV incident lab-energies. The data have been analyzed with the folding model, using the M3Y and DDD interactions. A good reproduction of the data is obtained if a renormalization coefficient for the real part of the optical potential is introduced. Moreover the application of the dispersion relation proposed by Mahaux et al . and which uses the imaginary part does not seem to give renormalization coefficients as important as those found in the analysis of the data.