Ernesto Marin | Instituto Politécnico Nacional (original) (raw)

Papers by Ernesto Marin

Respuestas, 2016

Reportamos el uso de la técnica fotoacústica resuelta en tiempo en el análisis de la evolución de... more Reportamos el uso de la técnica fotoacústica resuelta en tiempo en el análisis de la evolución de oxígeno fotosintético y el almacenamiento de energía en plantas verdes. Presentamos una aplicación de esta técnica al monitoreo de la fotosíntesis en la maleza acuática llamada comúnmente lirio acuático o jacinto de agua (Eichhornia Crassipes).Palabras Clave: Fotosíntesis; técnica fotoacústica; lirio acuáticoWe reported about the use of the time resolved photoacoustic technique for the analysis of the photosynthetic oxygen evolution and the energy storage in green plants. We present an application of this technique to the study of the photosynthesis in the aquatic vegetation, usually called aquatic lirium or water hyacinth (Eichhornia Crassipes). Keywords: Photosynthesis, photoacoustic technique, water hyacinth.

Revista Mexicana De Fisica E, 2016

In a recent article published in this journal [1] some considerations about thermal waves are pre... more In a recent article published in this journal [1] some considerations about thermal waves are presented, in particular about their velocity. It is showed that for thermal waves resulting from the solution of the parabolic heat diffusion equation (also known as second Fourier’s law, as it is a consequence of first Fourier’s law for heat conduction) for a semi-infinite one dimensional body with thermal diffusivity α and a sinusoidal heat source at its surface modulated at a frequency f , the group velocity,

AIP Conference Proceedings, 2007

The use of a photopyroelectric technique to obtain superficial and in-depth images, by means of t... more The use of a photopyroelectric technique to obtain superficial and in-depth images, by means of the interaction of thermal waves with the analyzed sample, has reached great interest due to its applications. In this paper we use photopyroelectric microscopy to obtain superficial and in-depth images of a dental piece. In the experimental setup a pyroelectric sensor and linear micro-positioners were used to obtain the photopyroelectric signal in each point of the sample which varies depending of the local, optical, and thermal, characteristics. Then it is possible by scanning the sample to obtain an image that reflects these local features.

We applied the Hot Wire (HW) technique and COMSOL Multiphysics software to study the heat transfe... more We applied the Hot Wire (HW) technique and COMSOL Multiphysics software to study the heat transfer of a homogeneous and isotropic solid material. The HW technique is based on the application of a linear power density modulated by a square pulse of heat in a specific time period. The power density is applied over the symmetry axis of the sample to produce a radial heat flux and then, to determine the thermophysical properties like specific heat, thermal conductivity and thermal diffusivity. In this work, the solutions of the transient heat transport equation by means of the finite element technique with appropriate boundary conditions are reported. Finally, we compared our simulated results with the experimental ones and some approximate mathematical models with a good agreement. These results show the utility of this methodology in the study of thermal properties in solids.

Resumen Utilizando el efecto fotoacústico se pretende diseñar un microscopio que ayude a generar ... more Resumen Utilizando el efecto fotoacústico se pretende diseñar un microscopio que ayude a generar imágenes de diversos materiales principalmente en el estudio de la cinética de crecimiento en películas delgadas.

Thin Solid Films, 2008

Bi doped cadmium telluride (CdTe:Bi) thin films were grown on glass-substrates by the close space... more Bi doped cadmium telluride (CdTe:Bi) thin films were grown on glass-substrates by the close space vapour transport method. CdTe:Bi crystals grown by the vertical Bridgman method, varying the nominal Bi concentration in the range between 1 × 10 17 and 8 × 10 18 cm − 3 , were used in powder form for CdTe:Bi thin film deposition. Dark conductivity and photoconductivity measurements in the 90-300 K temperature range and determination by photoacoustic spectroscopy of the optical-absorption coefficient of the films in the 1.0 to 2.4 eV spectral region were carried out. The influence of Bi doping levels upon the intergrain barrier height and other associated grain boundary parameters of the polycrystalline CdTe:Bi thin films were determined from electrical, optical and morphological characterization.

Rev. Mex. Fıs …, 2009

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En la técnica de relajación térmica una muestra es suspendida adiabáticamente en un recipiente al... more En la técnica de relajación térmica una muestra es suspendida adiabáticamente en un recipiente al vacío, mientras una de sus superficies se ilumina uniformemente al mismo tiempo que la temperatura, T, de su superficie posterior es monitoreada en función del tiempo, t. A partir de la dependencia T(t) puede determinarse el valor de la capacidad calorífica específica, C. En este trabajo calculamos T(t) en el caso de iluminación variable en el tiempo, específicamente aquel de una rampa de intensidad luminosa, I, de la forma I=I 0 t, donde I 0 es una constante. Sobre la base de simulaciones matemáticas se discuten las ventajas de esta variante con respecto al caso de iluminación constante. Palabras clave: Técnica de relajación térmica; Transferencia de calor; Calor específico; Propiedades térmicas In the thermal relaxation technique a sample is supported adiabatically in a recipient under vacuum conditions, while one of its surfaces is illuminated uniformly at the same time that the temperature, T, of the opposite surface is measured as a function of time, t. From the dependence T (t) the value of the specific heat capacity, C, can be determined. In this work we have calculated T (t) in the case of variable illumination, specifically for a ramp of light intensity I, of the form I=I 0 t, where I 0 is a constant. On the basis of mathematical simulations we have discussed the advantages of this variant when compared with the case of constant illumination.

The Physics Teacher, 2006

Inspired by a previously published TPT article,1 this paper describes the concept of thermal effu... more Inspired by a previously published TPT article,1 this paper describes the concept of thermal effusivity and the role of this parameter in understanding thermal physics concepts, in particular the fact that when we touch objects of equal temperature but of different materials we often feel that one body is “hotter” or “colder.”

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2007

The photo-induced charge transfer in four series of Prussian blue (PB) analogues was studied from... more The photo-induced charge transfer in four series of Prussian blue (PB) analogues was studied from photoacoustic spectra. In cobalticyanides the observed signals were assigned to a metal-to-ligand charge transfer, which appears as a shoulder below 450 nm, and to d-d transitions for Co(II), Ni(II) and Cu(II) complex salts. No evidence of metal-to-metal charge transfer was observed for this series, which is probably due to the high stability of low spin cobalt(III) in the hexacyanide complex. Photoacoustic spectra for ferricyanides are broad bands, which result particularly intense up to 750 nm. Such features were attributed to the overlapping of contributions from metal-to-ligand (<600 nm) and metal-to-metal charge transfer transitions, with probably also a minor contribution from d-d transitions in the outer metal. The spectra for the ferrocyanides series are dominated by the metal-to-ligand charge transfer band below 550 nm, approximately 100 nm above this transition in cobalticyanides. Within the studied solids, the most intense and broad metal-to-metal charge transfer bands were found for a series of low spin Co(III) high spin Co(II) hexacyanoferrates(II,III) and with similar features also for ferric ferrocyanide (Prussian blue), assigned to Fe(II) → Co(III) and Fe(II) → Fe(III) photo-induced transition, respectively. The first of these transitions requires of more energetic photons to be observed, its maximum falls at 580 nm while for Prussian blue it is found at 670 nm. Prussian blue analogues are usually obtained as nanometric size particles and many of them have a microporous structure. The role of surface atoms on the observed charge transfer bands in the studied series of compounds is also discussed.

Review of Scientific Instruments, 2003

The thermal wave interference technique (TWI) has been explored in recent years for the investiga... more The thermal wave interference technique (TWI) has been explored in recent years for the investigation of the thermal and transport properties of gases and liquids. In this article we address ourselves to the quantitative understanding of the transient thermal wave interference signal of air:hydrocarbon vapor mixtures. This is the situation one faces when placing a given portion of liquid hydrocarbon inside an initially air-filled thermal wave interference. What is observed in this case is the thermal wave interference signal decay as a function of the time as a result of the change of the gas thermal diffusivity with time due to the increase of the hydrocarbon vapor concentration in air. In this article we show that value of the thermal diffusivity of the saturated mixture is readily obtained from the saturation value of the normalized signal amplitude, without the need of performing the conventional L scan.

Journal of Physics D: Applied Physics, 2010

The photopyroelectric method has been recognized as a reliable and useful tool for the measuremen... more The photopyroelectric method has been recognized as a reliable and useful tool for the measurement of the thermal properties of condensed matter samples. Usually the photothermal signal is generated using intensity modulated light beams, whose amplitudes are difficult to maintain stable. In this paper we describe a variant of this technique that uses amplitude modulated electrical current as excitation source, via Joule heating of the metal contact on one side of the pyroelectric sensor. The possibilities of this method, called by us the electropyroelectric technique, for thermal effusivity measurements of liquid samples are shown using test samples of distilled water, ethanol and glycerine. The results obtained for this parameter agree well with the values reported in the literature. Our measurement uncertainties are about 3%, a fact that opens several possible applications.

Journal of Materials Science, 2011

In this paper a new and practical model for the determination of transport parameters of crystall... more In this paper a new and practical model for the determination of transport parameters of crystalline semiconductors, by means of the photoacoustic technique is reported. The model is based on the calculation of the photoacoustic signal for the so-called heat transmission configuration, and considers that the thermal response to periodical heating, due to light absorption, in semiconductor materials has mainly two contributions: (a) the vibrations of the crystal lattice (phonon contribution) and (b) the diffusion and recombination (bulk and superficial) of the photogenerated charge carriers. Considering these contributions as the heat sources, and using unmixed Dirichlet and Neumann boundary conditions, the solution of the heat diffusion equation, necessary for the calculation of the photoacoustic signal is obtained. In addition, an expression-describing a particular transport regime-that can be used as practical fitting function, for the more available experimental conditions, is developed. Finally, values of transport parameters for silicon wafers are obtained by fitting this model to the experimental data, showing a good agreement with the values quoted in literature.

Journal of Materials Science, 2007

We show that the Photo-Acoustic Spectroscopy (PAS) is an useful alternative method for the determ... more We show that the Photo-Acoustic Spectroscopy (PAS) is an useful alternative method for the determination of the optical-absorption coefficient of CdTe thin films, in the spectral region near to the fundamental absorption edge, ranging from 1.0 eV to 2.4 eV, using an open cell in the transmission configuration. We applied this method to the optical characterization of CdTe layers for several values of their thickness. These CdTe samples were deposited by closed-space vapor transport (CSVT) technique under different growth conditions.

Journal of Materials Science, 2004

SrTiO 3 and PbTiO 3 perovskites are combined to form the xPbTiO 3-(1 − x)SrTiO 3 (PST) solid solu... more SrTiO 3 and PbTiO 3 perovskites are combined to form the xPbTiO 3-(1 − x)SrTiO 3 (PST) solid solution. In this work, a study of its dielectric and thermal properties is reported as a function of PbTiO 3 content. The dielectric properties of the xPbTiO 3-(1 − x)SrTiO 3 solid solution are determined through a thermoelectric analysis technique and hysteresis measurements. Such measurements made at room temperature for all compositions show the influence of one component upon the other resulting in a response to the electric field that involves a strained lattice behavior. A limiting case of antiferroelectric-like behavior is observed for x = 0.5. The thermal properties such as the specific heat capacity (c) and thermal diffusivity (α) were determined using a photoacoustic technique (PA) and the temperature relaxation method (TRM). The thermal conductivity was calculated from the results obtained for c and α.

Journal of Applied Physics, 2010

In this work we study the influence of the thiourea/CdCl2 concentration ratio used for the chemic... more In this work we study the influence of the thiourea/CdCl2 concentration ratio used for the chemical bath deposition of CdS thin films on glass substrates, upon the CdS/CdTe interface recombination velocity in CdTe/CdS/glass structures, where the CdTe layer was grown on the CdS thin film by close space vapor deposition (CSVT)-hot wall technique. The interface recombination velocity was measured by means of the photoacoustic (PA) technique in a heat transmission configuration, in which minority carriers are photoexcited at the CdTe layer after illumination through the substrate and the CdS thin film. For data processing, a theoretical model was developed for the generation of the PA signal. We show a reduction in the value of the recombination velocity respecting those obtained for samples where CdS was grown by CSVT, and we observe that a minimal value appears for a thiourea/CdCl2 ratio in the CdS deposition solution equal to 5. These results show a good correlation with those of ele...

International Journal of Thermophysics, 2009

International Journal of Thermophysics, 2012

Recently the so-called electropyroelectric technique for thermal characterization of liquids has ... more Recently the so-called electropyroelectric technique for thermal characterization of liquids has been proposed (Ivanov et al., J. Phys. D: Appl. Phys. 43, 225501 (2010)). In this method a pyroelectric sensor, in good thermal contact with the investigated sample, is heated by passing an amplitude-modulated electrical current through the electrical contacts. As a result of the heat dissipated to the sample, the pyroelectric signal measured as a voltage drop across the electrical contacts changes in a periodical way. The amplitude and phase of this signal can be measured by lock-in detection as a function of the electrical current modulation frequency. Because the signal amplitude and phase depend on the thermal properties of the sample, these can be determined straightforwardly by fitting the experimental data to a theoretical model based on the solution of the heat diffusion equation with proper boundary conditions. In general, the experimental conditions are selected so that the thermal effusivity becomes the measured magnitude. The technique has the following handicap. As the result of heating and wear of the metal coating layers (previously etched to achieve a serpentine form) with time, their electrical resistance changes with time, so that the