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Tajuelo Rodríguez, Javier

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0000-0002-4085-7610
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Tajuelo Rodríguez
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Javier
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2013 - 201962020 - 20213
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Mostrando 1 - 9 de 9
  • Miniatura
    Publicación
    BiconeDrag—A data processing application for the oscillating conical bob interfacial shear rheometer
    (Elsevier, 2019-06) Sánchez Puga, Pablo; Pastor Ruiz, Juan Manuel; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel
    BiconeDrag is a software package that allows one to perform a flow field based data processing of dynamic interfacial rheology data pertaining to surfactant laden air–fluid interfaces obtained by means of a rotational bicone shear rheometer. MATLAB and Python versions of the program are provided. The bicone fixture is widely used to transform a conventional bulk rotational rheometer into an interfacial shear rheometer. Typically, such systems are made of a bicone bob, which is mounted on the rheometer rotor, and a cylindrical cup. Usually, the experiment consists of measuring the response of the interface under an oscillatory stress. The program takes the values of the torque/angular displacement amplitude ratio and phase difference to compute the interfacial dynamic moduli (or complex viscosity) by consistently taking into account the hydrodynamic flow both at the interface and the subphase. This is done by numerically solving the Navier–Stokes equations for the subphase velocity field together with the Boussinesq–Scriven boundary condition at the interface, and no slip boundary conditions elsewhere. Furthermore, the program implements a new iterative scheme devised by solving for the complex Boussinesq number in the rotor’s torque balance equation.
  • Miniatura
    Publicación
    Asphaltene-induced spontaneous emulsification: Effects of interfacial co-adsorption and viscoelasticity
    (American Institute of Physics, 2020-07-01) Anand, Satyam; Yao, Zhen; Kannan, Aadithya; Fuller, Gerald G.; Rodríguez Hakim, Mariana; Tajuelo Rodríguez, Javier
    Asphaltenes are a class of high molecular weight aromatic compounds found in crude oil. They adsorb onto toluene-water interfaces and induce a spontaneous emulsification phenomenon, whereby stable water-in-oil emulsions form without the need of an external energy input. This work aims to control and understand the factors affecting spontaneous droplet formation in the presence of asphaltene adsorption. This is particularly useful for crude oil refining, where the presence of a stable emulsion hampers the efficiency of downstream processing operations. We explore the effect of the addition of copolymers designed as crude oil flow improvers as a means to control the extent of emulsion formation. We find that the polymers competitively adsorb onto the toluene-water interface and diminish spontaneous emulsification. We also conduct fluorescence microscopy experiments and measurements of the interfacial energy to determine the mechanism of spontaneous emulsification in asphaltene systems. We conclude that an emulsion forms via the diffusion of molecular water into the oil phase and subsequent binding with asphaltene aggregates, leading to the nucleation of micrometer-sized water droplets. We find that the polymer forms complexes with the dissolved asphaltenes, possibly hampering the ability of diffused water to bind to the asphaltenes and reducing the extent of spontaneous emulsification. Finally, we investigate the role of interfacial shear and dilatational viscoelasticity to better understand which fundamental interfacial properties are important in the emulsification of asphaltene-laden systems. We find that the rate of formation of an interfacial microstructural network is inversely correlated with the extent and rate of spontaneous emulsification.
  • Miniatura
    Publicación
    Reología Interfacial. Técnicas macro y microscópicas y su aplicación a la caracterización de monocapas de Langmuir
    (Universidad Nacional de Educación a Distancia (España). Escuela Internacional de Doctorado. Programa de Doctorado en Ciencias, 2017) Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel; Pastor Ruiz, Juan Manuel
    En esta memoria se aborda el diseño y desarrollo de técnicas experimentales para la caracterización de las propiedades reológicas de cizalla de sistemas cuasi-bidimensionales formados en interfases fluido-fluido, y su posterior aplicación en el estudio de la dependencia de los módulos dinámicos superficiales de monocapas de Langmuir de ácidos grasos respecto de dos de las variables termodinámicas del sistema, la temperatura y la presión superficial. En el momento del inicio del presente trabajo existían en la bibliografía diversas técnicas con similares objetivos, surgidas de manera continua a partir de mediados del s. XX. La influencia de las propiedades mecánicas de los sistemas interfaciales en multitud de procesos biológicos o industriales ha generado un creciente interés en esta rama científica, alentando la aparición de métodos experimentales cada vez más refinados. A pesar de este creciente esfuerzo, la medida de las propiedades mecánicas de sistemas con un espesor típico del orden de nanometros, formados en interfases y, por tanto, en contacto con al menos una fase líquida, es aún hoy un tema abierto. De hecho, los resultados obtenidos por medio de diferentes técnicas que, en función de su longitud característica, podemos clasificar en técnicas micro y macro-reológicas, son en muchos casos difícilmente comparables. El objetivo principal de la primera parte de esta memoria, en la que se describen los trabajos de diseño y construcción de los dispositivos experimentales y formulación de los modelos teóricos empleados, es, en primer lugar, refinar el funcionamiento del macro- Reómetro Interfacial de Aguja Magnética (ISR) mediante el empleo de sondas más pequeñas y ligeras que incrementan su resolución. Esta novedad introducida en la técnica, junto con un correcto tratamiento de la hidrodinámica del sistema, nos permite extender el rango de aplicación de este dispositivo a viscosidades superficiales mucho menores, haciendo posible la comparación directa con técnicas micro-reológicas. A partir de los conocimientos y experiencia adquiridos durante la ejecución de esta tarea, que se desarrolla en el Capítulo 1, abordamos en el Capítulo 2 el diseño y construcción de un nuevo ISR basado en el movimiento controlado de una trampa magnética formada por dos pequeños imanes. Gracias a este nuevo método de accionamiento, la importancia relativa de la resistencia hidrodinámica debida a la interfase aumenta significativamente, incrementando, así mismo, la resolución del dispositivo. En el Capítulo 3 aplicamos a una geometría distinta, el Reómetro Interfacial de disco cónico, una aproximación numérica análoga a la empleada en los capítulos anteriores para obtener el campo de velocidades en la subfasae y la interfase. La técnica macro-reológica de disco cónico está ampliamente extendida gracias a su versatilidad, puesto que está basada en un reómetro de torsión convencional adaptado para poder medir reología de cizalla en interfases mediante una geometría de sencilla construcción. Proponemos un nuevo esquema, basado en la resolución numérica del campo de velocidades, para obtener los módulos dinámicos superficiales a partir de los datos recogidos por el reómetro de torsión (par ejercido y ángulo girado), y comparamos los resultados obtenidos a través de dicho esquema con aquellos presentes en la bibliografía. Ello nos permite, de paso, establecer bajo qué condiciones la resolución numérica del campo de velocidades es necesaria para una correcta interpretación de los resultados. En la segunda parte de la memoria empleamos el ISR de trampa magnética en el estudio de la Reología Interfacial de monocapas de Langmuir de ácidos grasos. Las propiedades micro-estructurales de estos sistemas han sido ampliamente estudiadas durante las últimas tres décadas, pero el conocimiento sobre sus propiedades mecánicas es mucho menor, probablemente debido a las dificultades de esta rama científica mencionadas anteriormente. En el Capítulo 4 se presentan los resultados de un estudio pormenorizado de la dependencia de los módulos dinámicos respecto de la presión superficial y la temperatura de la monocapa, construyendo en última instancia un diagrama de fases a partir de la información obtenida en los experimentos reológicos.
  • Miniatura
    Publicación
    Flow field-based data analysis in interfacial shear rheometry
    (Elsevier, 2021-02) Sánchez Puga, Pablo; Pastor Ruiz, Juan Manuel; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel
    Developments in interfacial shear rheometers have considerably improved the quality of experimental data. However, data analysis in interfacial shear rheometry is still an active field of research and development due to the intrinsic complexity introduced by the unavoidable contact of the interface with, at least, one supporting bulk subphase. Nonlinear velocity profiles, both at the interface and the bulk phases, pervade the system dynamical behavior in the most usual experimental geometries, particularly in the case of soft interfaces. Such flow configurations demand data analysis schemes based on the explicit calculation of the flow field in both the interface and the bulk phases. Such procedures are progressively becoming popular in this context. In this review, we discuss the most recent advances in interfacial shear rheology data analysis techniques. We extensively review some recently proposed flow field-based data analysis schemes for the three most common interfacial shear rheometer geometries (magnetic needle, double wall-ring, and bicone), showing under what circumstances the calculation of the flow field is mandatory for a proper analysis of the experimental data. All cases are discussed starting at the appropriate hydrodynamical models and using the equation of motion of the probe to set up an iterative procedure to compute the value of the complex Boussinesq number and, from it, the complex interfacial viscosity or, equivalently, the complex interfacial modulus. Moreover, two examples of further extensions of such techniques are proposed, concerning the micro-button interfacial shear rheometer and the potential application of interfacial rheometry instruments, together with adapted flow field-based data analysis techniques, for bulk rheometry, particularly in the case of soft samples.
  • Miniatura
    Publicación
    Shear rheology of fluid interfaces: Closing the gap between macro- and micro-rheology
    (Elsevier, 2018-09) Guzmán Solís, Eduardo; Pastor Ruiz, Juan Manuel; González Rubio, Ramón; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel; Ortega Coloma, Francisco Javier
    For many years the determination of the shear viscosity of interfacial layers has been source of strong controversy. This is mainly because different techniques provided different values of such parameter, which leads in many cases to a puzzling interpretation of the experimental results. One possible explanation of this is the non-correct analysis of the hydrodynamic conditions of the measurement and, in particular, the assumption of some approximations that may not be necessarily valid in all cases. The introduction of hydrodynamic consideration in the study of interfacial shear rheology has helped to clarify some of the existing discrepancies between measurements performed using different devices, thus allowing one to establish clearly the viscosity range in which different techniques can operate with enough sensitivity for determining the interfacial shear viscosity. This review puts in perspective the most recent developments on the studies of the interfacial shear rheology of fluid/fluid interfaces, analyzing the strength and weakness of the different approaches.
  • Miniatura
    Publicación
    Flow field based data processing for the oscillating conical bob interfacial shear rheometer
    (American Institute of Physics, 2018-01-01) Pastor Ruiz, Juan Manuel; Tajuelo Rodríguez, Javier; Rubio Álvarez, Miguel Ángel
    A rotational rheometer can be used as an interfacial shear rheometer (ISR) by means of proper accessories that allow one to shear fluid-fluid interfaces in a controlled manner. One of the most used accessories, even commercially available, is based on a biconical bob geometry. However, recovering the correct values of the rheological variables is far from trivial. A strategy that has proved to be successful in other ISRs is to properly account for the interface and subphase drags by numerically finding the corresponding flow fields and, then, use an iterative scheme to recover the proper values of the complex Boussinesq number and, consequently, the dynamic surface moduli. Here, we propose to use such a scheme for the biconical bob oscillatory rheometer. We compare our solution with different well known previous approximations, and discuss under which conditions those approximations may lead to errors in the data processing. We have tested the performance of our design and numerical framework on several interfacial systems, comparing the results to those obtained through a magnetic needle rheometer (ISR). We demonstrate that, even for relatively low values of the Boussinesq number, the numerical flow field solution here proposed allows one to precisely reproduce the results obtained by the ISR, while those approximations based on a linear velocity decay at the interface may introduce spurious effects on the calculation of the dynamic surface moduli.
  • Miniatura
    Publicación
    Linear shear rheology of aging β-casein films adsorbing at the air/water interface
    (Elsevier, 2018-02-01) Martínez Pedrero, F.; Sánchez Puga, Pablo; Chulia Jordan, R.; González Rubio, Ramón; Tajuelo Rodríguez, Javier; Ortega Coloma, Francisco Javier; Rubio Álvarez, Miguel Ángel
    In this work, the viscoelasticity of fragile β-casein films has been followed using different macro- and microrheological techniques. The modulus of the complex surface viscosity varies with time, allowing for the monitoring of the protein adsorption and annealing. β-casein adsorption creates a soft glassy gel at the interface that experiences an aging process. Macrorheological experiments with multiple probe sizes in addition to microrheological experiments demonstrated the consistency of the surface rheological properties over a broad range of viscosities. Surface pressure measurements were performed to complement the characterization of the processes.
  • Miniatura
    Publicación
    Single bubble and drop techniques for characterizing foams and emulsions
    (Elsevier, 2020-12-01) Chandran Suja, V.; Fuller, G. G.; Rodríguez Hakim, Mariana; Tajuelo Rodríguez, Javier
    The physics of foams and emulsions has traditionally been studied using bulk foam/emulsion tests and single film platforms such as the Scheludko cell. Recently there has been a renewed interest in a third class of techniques that we term as single bubble/drop tests, which employ isolated whole bubbles and drops to probe the characteristics of foams and emulsions. Single bubble and drop techniques provide a convenient framework for investigating a number of important characteristics of foams and emulsions, including the rheology, stabilization mechanisms, and rupture dynamics. In this review we provide a comprehensive discussion of the various single bubble/drop platforms and the associated experimental measurement protocols including the construction of coalescence time distributions, visualization of the thin film profiles and characterization of the interfacial rheological properties. Subsequently, we summarize the recent developments in foam and emulsion science with a focus on the results obtained through single bubble/drop techniques. We conclude the review by presenting important venues for future research.
  • Miniatura
    Publicación
    Propiedades mecánicas de monocapas de Langmuir con reómetro interfacial de aguja
    (Universidad Nacional de Educación a Distancia (España). Facultad de Ciencias, 2013-07-16) Tajuelo Rodríguez, Javier