Publication: Caracterización de ferritas Ni-Zn obtenidas por compactación uniaxial y moldeo de inyección de polvos
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2014-04
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2014-07-11
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Abstract
En la presente tesis doctoral se ha estudiado y caracterizado una ferrita Ni-Zn comercial utilizando dos procesos de fabricación no convencionales en estos materiales como son el moldeo por inyección de polvos (PIM) y la sinterización solar. Como muestra de referencia se tomó la misma ferrita obtenida mediante compactación uniaxial y sinterización convencional.
En el caso de las muestras obtenidas mediante PIM se utilizaron 3 cargas en polvo diferentes (52, 55 y 58 % en volumen) a partir de un sistema ligante multicomponente. Están mezclas fueron caracterizadas reológicamente previo a su inyección. Una vez obtenidas las muestras estas fueron sinterizadas y caracterizadas microestructural, mecánica y magnéticamente. También se realizó un estudio de la superficie de fractura de las muestras con el objetivo de relacionar los resultados de las propiedades alcanzadas.
Por otra parte, se sinterizaron en un horno solar de la Plataforma Solar de Almería muestras compactadas unixialmente. Se realizó un estudio de la sinterabilidad de las ferritas variando la velocidad de calentamiento/enfriamiento (desde 15ºC/min hasta 60ºC/min), el tiempo de sinterización (desde 15 minutos hasta 1 hora) así como la temperatura (desde 1150ºC hasta 1300ºC). El estudio microestructural, mecánico y magnético se realizó de manera análoga al realizado en las ferritas inyectadas
Finalmente, se concluyó con el estudio de las propiedades eléctricas mediante espectroscopía de impedancia compleja de ferritas compactadas y su evolución con la velocidad de enfriamiento y la atmósfera. Con los resultados obtenidos se relacionó el comportamiento de las propiedades eléctricas con las propiedades magnéticas de las muestras -----------------------------------------------------------------------------------
The present PhD thesis is focused on the study and characterization of a commercial Ni-Zn ferrite using two non-conventional fabrication methods: Powder Injection Moulding (PIM) and Solar Sintering. As reference sample, the same ferrite was prepared by uniaxial pressing sintering in a conventional electric furnace. Three powder loading mixtures (52, 55 y 58% Vol.) from a multicomponent binder, were used to produce samples by PIM. The mixtures were rheological characterized previously to the injection. Once the samples were sinterized, a microstructural, mechanical and magnetic characterization was performed. A fractographic study was also made in order to analyze the final properties. On the other hand, uniaxial pressed samples were sintered in a Solar Furnace at Plataforma Solar in Almeria. A sinterability study was carried out varying the heating/cooling rate (from 15ºC/min to 60ºC/min), time (from 15 minutes to 1 hour) and temperature (from 1150ºC to 1300ºC). Similar mechanical, magnetic, microstructural and fractographic analysis were made as for PIM samples. Finally, the relationship between electrical properties, cooling rate and atmosphere during sintering were studied in uniaxial pressed samples by complex impedance spectroscopy. These results were used to explain the samples magnetic properties. The results were used to relate the behaviour of the electrical properties to the magnetic properties.
The present PhD thesis is focused on the study and characterization of a commercial Ni-Zn ferrite using two non-conventional fabrication methods: Powder Injection Moulding (PIM) and Solar Sintering. As reference sample, the same ferrite was prepared by uniaxial pressing sintering in a conventional electric furnace. Three powder loading mixtures (52, 55 y 58% Vol.) from a multicomponent binder, were used to produce samples by PIM. The mixtures were rheological characterized previously to the injection. Once the samples were sinterized, a microstructural, mechanical and magnetic characterization was performed. A fractographic study was also made in order to analyze the final properties. On the other hand, uniaxial pressed samples were sintered in a Solar Furnace at Plataforma Solar in Almeria. A sinterability study was carried out varying the heating/cooling rate (from 15ºC/min to 60ºC/min), time (from 15 minutes to 1 hour) and temperature (from 1150ºC to 1300ºC). Similar mechanical, magnetic, microstructural and fractographic analysis were made as for PIM samples. Finally, the relationship between electrical properties, cooling rate and atmosphere during sintering were studied in uniaxial pressed samples by complex impedance spectroscopy. These results were used to explain the samples magnetic properties. The results were used to relate the behaviour of the electrical properties to the magnetic properties.
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Industria metalúrgica, Ferritas, Moldeo por inyección de polvos, Sinterización solar, Propiedades de los materiales