Repository logo

Browsing by Author "Montoya Carvajal, Juan Fernando"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Estudio de la estabilidad de fases en el sistema Zn – Cr – O a partir de síntesis por combustión en solución
    (Corporación Universitaria Lasallista, 2017) Montoya Carvajal, Juan Fernando
    Introduction. Compounds with transition metals in their structure generate great interest due to their physical properties, especially their magnetic and electric ones. The spinel ZnCr O2 4 has been characterized by its potential uses as photocatalyst and as CO2 , sensing material, which has current relevance and has motivated to learn about new methods for obtaining it and for justifying studies that allow to understand the thermodynamic characteristics for its formation. Objective. Study phase stability ZnCr O2 4 with the coexistence of secondary phases formed through thermal treatments. Materials and methods. From the homogenization of glycine and nitrates (zinc and chrome), an amorphous compound was synthetized by combustion in solution. After thermal treatments (750, 850 and 950 °C), the compound presented crystalline ordering. Results. After obtaining the compound, the morphology of the powders was evaluated through scanning electronic microscopy (SEM) and their composition was also evaluated (EDS). The presence of organic material was determined and a thermal characterization was made (TGA and DSC) to define the phase formation temperature. Next, the structures were evaluated and compared through X-ray diffraction (XRD). Using simulations in the FactSage® software the results were compared to verify phase equilibrium. Conclusion. Through the solution combustion method, a noncrystalline structure is obtained, formed by Zn, Cr and O, confirming the presence of C associated to the organic component after combustion.
  • Thumbnail Image
    Item
    Reflexión desde la Entropía: un análisis de la realidad según la violencia en la sociedad.
    (Unilasallista Corporación Universitaria, Editorial Lasallista, 2022) Montoya Carvajal, Juan Fernando
    Introducción: la teoría del caos se usa para explicación de fenómenos complejos, cuya naturaleza no responde a comportamientos lineales y que a su vez no permite determinar con exactitud medidas y cálculos, pero que a pesar de ello se han logrado avances significativos en la ciencia, pudiéndose expandir además hasta las explicaciones de fenómenos sociales, siendo en este caso la violencia. Materiales y Métodos: se emplearon expresiones matemáticas para validar un modelo de realidad que describa aproximadamente índices de violencia a partir de datos reales. Resultados: se obtuvieron relaciones matemáticas que describen el comportamiento caótico, las cuales dependiendo de la tasa de violencia define si el valor tiende a cero, a un valor constante o un comportamiento caótico. Conclusiones: se obtuvo una relación matemática que describe el comportamiento entrópico de la violencia en sociedad, cuya tendencia caótica describe aproximadamente índices de violencia reales.
  • Thumbnail Image
    Item
    El sexo intermedio en Virginia Woolf.
    (Unilasallista Corporación Universitaria, Editorial Lasallista, 2022) Catullo MacIntyre, Luca Tommaso; Montoya Carvajal, Juan Fernando
    Los géneros literarios que los críticos han utilizado para calificar la obra de Virginia Woolf, Orlando, publicada en 1928, incluyen: la alegoría religiosa, la fábula, la novela policíaca, literatura de doppelgänger, cuentos diabólicos escoceses o la novela gótica. Todavía se discute si es un relato de ciencia ficción. Sin embargo, el tema principal es la identidad sexual del protagonista, quien cruza un “tiempo sin tiempo”, transformando su sexo y sexualidad a lo largo del recorrido de su alma. Este, es un claro rechace a la estructura de las novelas victoriana, en las cuales dominan los personajes masculinos y escasean los femeninos. Orlando nace hombre para luego, con el pasar de los siglos – desde 1600, últimos años de la Reina Isabel I, hasta el siglo XX, en el contexto político real de Inglaterra, el de las Sufragistas, cuando se da su transformación en mujer y sobre todo en escritora. Pese a lo apenas mencionado, esta novela no es sexista. En realidad, el fin de la obra es exponer las necesidades de una dama de la época isabelina, los tropiezos masculinos y femeninos de la sociedad victoriana y los obstáculos inherentes a las obsesiones del yo, en donde el lenguaje es determinante para la marcación de épocas. Según Woolf, la diferencia sexual viene dada por la educación, pero no pretende fomentar la dualidad hombre-mujer, sino redefinir la feminidad, proclamando a la vez que una mente debe ser andrógina.
  • Thumbnail Image
    Item
    Síntesis de la espinela ZnCrxFe2-xO4(0 ≤ x ≤ 1) por combustión en solución y estudio termodinámico de la estabilidad de fases
    (Corporación Universitaria Lasallista, Editorial Lasallista., 2018) Montoya Carvajal, Juan Fernando; Chavarriaga Miranda, Andrés; Villada Gil, Stiven
    Introduction. Spinels are metal oxides generally used for their chemical, electrical and magnetic properties. The occupation of transition metals in tetrahedral and octahedral positions generates characteristics of technological interest and the study of the interaction of the material with external fields is motivating and justifiable. The synthesis of spinels has commonly been using the traditional method (ceramic), but to obtain better control in the particle size alternative methods have been chosen, among them the method of combustion in solution. Objective. Synthesize the spinel by the combustion method in solution and study the phase transitions as a function of temperature. Materials and methods. The compound was synthesized (for x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) by combustion in solution, using metallic nitrates and glycine as fuel, generating an ignition around 1500 ° C approximately. Results The samples were characterized morphologically (SEM), compositionally (EDS), structurally (XRD), thermogravimetrically (TGA) and calorimetrically (DSC). The characterization was carried out for precalcined samples (without thermal treatment), heated to 750 and 850 ° C, this in order to compare the results obtained in the characterizations of the compounds and thereby identify the physical changes generated by the formation of secondary phases .
  • Thumbnail Image
    Item
    Síntesis y caracterización de la Espinela FeCr2O4
    (Corporación Universitaria Lasallista, 2015-08-03) Montoya Carvajal, Juan Fernando; Chavarriaga Miranda, Edgar Andrés; Villada Gil, Stiven; Muñoz García, Andrés Mauricio; Restrepo Baena, Óscar Jaime
    Introduction. Compounds with spinel structures are known for having cations in their tetrahedral and octahedral structures, a fact that gives them versatility for technological applications given their physical and chemical properties (Ziemniak, Anovitz, Castelli y Porter, 2007, 1474–1492). Ferrites and chromites are especially interesting due to their diverse physical properties and their consequent versatility for technological applications (Gopal y Spaldin, 2006, 094418-9; Singh y Rhee, 2010, 1233-1237). Objective. Synthetize, with the traditional ceramic method, the FeCr2O4 spinel and identify its main properties taking its structural, colorimetric and magnetic characterization as a base. Materials and Methods. By the use of reactions in the solid state at high temperatures, by means of the iron and chromium oxides (Cr2O3 and Fe3O4) at fixed proportions as precursors, the FeCr2O4 compound with a spinel type structure was synthetized. For the synthesis of different temperatures, a characterization of the material obtained was performed by means of X ray diffraction (DRX), UV-VIS-NIR spectroscopy, thermal analysis (DTA/TGA) and the magnetic susceptibility. Results. The results obtained agree with the reports and it can be seen that the changes in the reflectance spectrums are correlated with the base identified, with the crystallinity degree and with the magnetic response. Conclusions. The FeCr2O4 spinel was satisfactorily synthetized by the use of the traditional method for temperatures between 800 and 1300 °C, and samples with structural and optically stability were obtained.
  • Thumbnail Image
    Item
    Síntesis y caracterización de pigmentos tipo espinela CuCr2O4 a través del método autocombustión en solución
    (Corporación Universitaria Lasallista, 2012) Chavarriaga Miranda, Edgar Andrés; Betancur Granados, Natalia; Montoya Carvajal, Juan Fernando; Restrepo Baena, Óscar Jaime
    Introduction. In the industrial production of pigments, the solid state reaction has been traditionally applied as a method to obtain complex oxides, such as pigmenting application spinels (formula AB2O4), which are synthesized through alternative routes, aiming to reduce costs and energy consumption in the production process. In this research work, the spinel type pigment CuCr2O4 was synthesized by the use of the in solution auto combustion method, through the citrate-nitrate, urea-nitrate and glycine-nitrate routes. Objective. To obtain spinel type structures by the use of the citrate-nitrate, urea-nitrate and glycine-nitrate auto combustion methods. Materials and methods. For the synthesis of the pigments in the different routes, the compounds (Cu(NO3)2.3 H2O), (Cr(NO3)3.9 H2O), (CH2NH2CO2H), (CO(NH2)2), (C6H8O7), (CuCO3. Cu(OH)2) and finally (III) (Cr2O3), were used. The pigments obtained were characterized by the use of several techniques such as X ray diffraction (DRX), scanning electron microscopy (SEM) and UV-VIS spectrophotometry. Results and discussion.With the synthesis methods proposed, a control of size and morphology of the particles and of the purity of the phases, was achieved. Conclusion. The pigments obtained by the different routes have similar characteristics and characterization responses and, therefore, the pigment achieved is the same. This means that reducing costs in the synthesis is possible.