My main research interests include thermal wave physics and related photothermal techniques and their applications, thermal properties measurement techniques, heat transport studies as well as physics education. Thermal waves can be defined as solutions of the heat diffusion equation in the presence of periodical and pulsed heat sources. Thermal wave basic properties have found important applications in the so-called photothermal techniques. These are methods suitable for optical (spectroscopic) and thermal characterization of condensed matter and gaseous materials, and related applications.
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.
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,
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.”
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.
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.
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...
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.
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,
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.”
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.
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.
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...
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