Ingeniería y Ciencia de los Materiales
URI permanente para esta colecciónhttp://54.81.141.168/handle/123456789/31431
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Ítem Texto completo enlazado Synthesis of Hydroxyapatite thin films on PMMA Printed Substrates(Pontificia Universidad Católica del Perú, 2018-01-19) Sauñi Camposano, Yesenia Haydee; Rädlein, Edda; Grieseler, RolfEach year millions of people suffer from bone defects resulting from trauma, tumors or bone-related injuries. Therefore there is a need to continuously develop new materials or improve the properties of the materials currently used, for bone replacement or implant applications. Polymethyl methacrylate (PMMA) has proven to be a promising alternative as a material for implants; however, there are still some limitations inherent to this material, particularly related to its surface properties. This thesis work is focused on the fabrication of hydroxyapatite (HAp) thin films on the surface of 3D printed PMMA substrates. 3D printing, particularly the Fused Deposition Modeling (FDM) technique was used to fabricate PMMA substrates with different surface porosity levels. FDM technique exhibits the potential for fabricating customized freeform structures for several applications including craniofacial reconstruction. HAp thin films were deposited by Radio Frequency Magnetron Sputtering (RFMS) and Ion Beam Sputtering (IBS) techniques, with a commercial target and an “in house” sintered target, respectively. A structural, chemical, mechanical, and morphological characterization was conducted in the generated surfaces by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and hardness and roughness measurements. The results of the XRD analysis revealed an amorphous structure for the films produced by both RFMS and IBS techniques on the PMMA substrates. The micrographs obtained by SEM showed a columnar morphology and a low density for the films produced by RFMS; the same technique revealed a structure of ridges of standing platelets with curved contours for the IBS deposited films. The amorphous structure and the morphology of the films, as well as the hardness and roughness can be propitious to improve surface properties and promote the osseointegration capabilities of PMMA. This work contributes to the basis for the development of a PMMA implant manufacturing process using 3D printing and HAp film deposition techniques, with improved osseointegration properties.Ítem Texto completo enlazado Preparation and characterization of sputtered hydroxyapatite thin films(Pontificia Universidad Católica del Perú, 2018-01-19) Ugarte Díaz, Jorge Alfonso; Grieseler, Rolf; Schaaf, Peter; Rumiche Zapata, Francisco AurelioIn this work, hydroxyapatite (HAp) thin films were fabricated using two different sputtering techniques: Radio frequency magnetron sputtering and ion beam sputtering. In the first case, the films were grown on Ti-6Al-4V substrates using a high-purity commercial HAp target, obtaining a thickness ~200 nm. For the second method, the film were grown on pure titanium substrates using a self-produced HAp target. This target was fabricated with powders (Ca/P = 1.628, sintered and crushed). Here, the thickness of the fabricated film was ~300 nm. The sintering tests for the target fabrication were carried out using two different heating regimens at a maximum temperature of 1200 °C (holding time of 2h and 4h) using various additives. As additives, water (H2O), polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were used to improve the mechanical strength of the green discs. The as-deposited films were amorphous in both cases. Therefore, the films were annealed to increase the crystallinity. Annealing was performed in air for 2h at temperatures: 400, 600 and 800 °C for RF-magnetron sputter samples; 600 and 800 °C for ion beam sputter samples. The result of the films shows in both cases that the crystallinity of HAp was improved only for the annealed samples fabricated with ion beam sputtering at 800 °C. In both cases energy dispersive X-ray spectroscopy measurements show a decrease in Ca/P ratio with increasing the temperature. Hardness results revealed an increase in this with the increase in temperature possibly due to the formation of titanium oxide. The roughness for the fabricated films with the RFmagnetron sputtering increases till an annealing temperature of 600 °C and then decreases till 800 °C, while the roughness for the fabricated films with ion beam sputtering is higher in the as-deposited samples and then this is reduced by increasing the annealing temperature.Ítem Texto completo enlazado Characterization of carbon based nanostructures for the detection of tuberculosis(Pontificia Universidad Católica del Perú, 2017-11-29) Muñante Palacin, Paulo Edgardo; Grieseler, RolfTuberculosis is a leading killing disease worldwide with more than 9 million people a ected per year. Current diagnostic methods exhibit several disadvantages; one of the most promising alternatives to overcome this is the development of nanostructured diagnostic systems which are able to detect molecules associated with certain diseases. Graphene since its discovery has been the focus for the development of these sensing elements due to its excellent electronic properties. In this work, a graphene-based eld e ect transistor (FET) has been developed for tuberculosis DNA detection, in order to set the basis for a diagnostic method that overcomes current limitations. The sensing elements composed of graphene monolayers were manufactured in the stages of annealing of the substrate, addition of the linker and functionalization with the addition of a probe DNA for tuberculosis detection. Additionally, two conditions for the sensing element were generated; one with the addition of a complementary DNA sequence (\DNA Target") and the other with a mismatched DNA sequence (\Non-complementary DNA"). The graphene and the transistor, in each stage of the manufacturing process, were structural, chemical and morphologically characterized by Raman Spectroscopy, Energy Dispersive X-ray Spectroscopy (EDS), Optical Microscopy, Laser Scanning Microscopy (LSM), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). The results indicated an appropriate functionalization of the graphene surface with the linker, the immobilization of the probe tuberculosis DNA and the hybridization with the corresponding \DNA Target", demonstrated by observation of di erent homogeneous morphologies and an appropriate increase in the roughness in each stage of the manufacturing process. Also by the presence of characteristic peaks of nitrogenous bases and in the variation of graphene bands in the Raman spectrum. On the contrary, the sensor element with the \Non-complementary" showed an agglomeration of the molecules and segregation of salts on a heterogeneous surface. The results of the characterization are consistent with the electronic characteristics previously determined. This investigation contributes to a basis for the development of a tuberculosis detection system based on nanotechnology for clinical application.Ítem Texto completo enlazado Anisotropy and humidity effect on tensile properties and electrical volume resistivity of fused deposition modeled acrylonitrile butadiene styrene composites(Pontificia Universidad Católica del Perú, 2017-09-06) Almenara Cueto, Carlos Ignacio; Grieseler, Rolf; Kups, ThomasEn la presente tesis, se estudió la influencia de la anisotropía y la humedad en las propiedades mecánicas a la tracción y la resistividad volumétrica de los compuestos de Acrilonitrilo Butadieno Estireno reforzado con Nano Tubos de Carbono y Acrilonitrilo Butadieno Estireno reforzado con Micro Fibras de Carbono impresos en 3D de por Deposición de Material Fundido. Para estudiar la influencia de la anisotropía, tres diferentes orientaciones de impresión de capa fueron comparadas (0°, 45° and 45°/-45°) esto para una altura de capa de 0.2 mm. Se concluyó que la influencia de la anisotropía es importante para el comportamiento mecánico de el Acrilonitrilo Butadieno Estireno con Micro Fibras de Carbono esto debido a la relación que existe entre la resistencia que realiza el refuerzo y el alineamiento que presentan las fibras respecto a la dirección de tracción. Por otro lado, no se encontraron mayor influencia de la anisotropía en las propiedades mecánicas del Acrilonitrilo Butadieno Estireno con Nano Tubos de Carbono. En la resistividad volumétrica para el Acrilonitrilo Butadieno Estireno con Nano Tubos de Carbono no se encontró mayor variación en los resultados debido a la anisotropía de las capas. El Acrilonitrilo Butadieno Estireno con Micro Fibras de Carbono no pudo ser ensayado debido a la alta resistividad que el material presentó. Para estudiar la influencia de la humedad, dos condiciones del filamento se compararon: seco y expuesto a la humedad. Se concluyó que la influencia de la humedad en el filamento es también importante en el comportamiento mecánico a la tracción del Acrilonitrilo Butadieno Estireno con Micro Fibras de Carbono esto debido a que la humedad absorbida por el filamento se elimina a través de burbujas de vapor que explosionan durante la impresión 3D empobreciendo así la adherencia entre la fibra y la matriz polimérica. Por otro lado, no se encontró tampoco mayor influencia en el comportamiento mecánico a la tracción del Acrilonitrilo Butadieno Estireno reforzado con Nano Tubos de Carbono debido a la humedad. En la resistividad volumétrica, se encontró que la humedad influye más en los resultados que la anisotropía, pero no llega a ser una influencia considerable. Esta influencia se debe principalmente a estructura menos uniforme que presenta el sólido impreso debido a las alteraciones producto de las explosiones de burbujas de vapor para eliminar la humedad absorbida como se mencionó anteriormente.