Desarrollo de proceso de nitruración interna de espumas de Fe y Fe–Nb.
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Date
2026
Authors
Castro Unda, Osvaldo Michel
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Abstract
Las espumas metálicas son materiales caracterizados por una fase de vacíos, denominada poro, cuya morfología, tamaño, distribución e interconectividad determinan propiedades tales como baja densidad, absorción de energía, amortiguación de vibraciones, permeabilidad y alta superficie específica. En sistemas de base Fe, la pulvimetalurgia mediante técnica de space holders permite obtener espumas con porosidad abierta e interconectada. Sin embargo, la presencia de poros produce una disminución significativa de las propiedades mecánicas debido al efecto concentrador de tensiones, lo que motiva el desarrollo de estrategias orientadas al reforzamiento local de la vecindad de estas cavidades. En este marco, la nitruración constituye una alternativa de interés para materiales ferrosos. Aunque este tratamiento ha sido estudiado en materiales compactos y en algunas espumas metálicas, la nitruración interna en espumas ferrosas abiertas, particularmente en sistemas Fe–Nb, ha sido escasamente abordada. En esta memoria se evaluó una ruta de nitruración interna basada en la impregnación de agentes nitrurantes en la red porosa. Para ello, se produjeron espumas de Fe y Fe–Nb por pulvimetalurgia utilizando NH₄HCO₃ como agente espaciador, y posteriormente se aplicó un tratamiento termoquímico, complementando el estudio con análisis termodinámico, caracterización por difracción de rayos X y medición de dureza local. Los resultados confirmaron la factibilidad preliminar de la ruta de procesamiento; no obstante, no permitieron demostrar de manera concluyente la incorporación efectiva de nitrógeno en la vecindad de los poros ni validar completamente la hipótesis de reforzamiento localizado. Por ello, el trabajo se enmarca como una evaluación preliminar de factibilidad de esta estrategia.
This study presents the development and characterization of insulating foams produced from Quillaja saponaria, incorporating two types of bicomponent fibers (PLA/PLA and PLA/PBS) as thermal bonding agents. These fibers act as thermal bonding agents through the melting of the PLA (polylactic acid) or PBS (polybutylene succinate) sheath, depending on the fiber type used. The preparation process of quillay fluff pulp is described using different wet and dry refining techniques. The fluff pulp was classified using sieves of different mesh sizes to compare various particle size ranges. To perform the fluffing process, two mixing strategies were evaluated: manual carding and air injection under suspension conditions. The appropriate amount of bicomponent fiber was determined according to the thermal insulation performance and mechanical properties of the resulting material. The thermal properties of the foam were evaluated through a one-dimensional transient heat conduction model solved using Fourier series with orthogonal bases. Due to the absence of ASTMstandard thermal conductivity equipment, this methodology was implemented to preliminarily estimate the thermal properties of the material from experimental measurements. The thermal characterization yielded average values of α = 1,664 × 10−7 m2/s, k = 0,0159W/(m·K), R = 21,4039 K/W (for an area of 0,09 m2), placing the material within the range of high-efficiency thermal insulators. An economic feasibility assessment of the project, considering OPEX, CAPEX, Payback Period, IRR, and NPV, yielded promising results, with an NPV of USD 1,188,683 $ USD and an IRR of 31.68 %. These results provide encouraging evidence that a short-fiber forestry residue can be transformed into a thermal insulation material into a lightweight, reproducible, and competitive thermal insulation material, demonstrating its potential as a sustainable alternative to conventional insulation materials in terms of economic performance as well as thermal and structural properties, establishing a solid basis for future optimization, scale-up, and standardization under ISO or ASTM regulations. Keywords
This study presents the development and characterization of insulating foams produced from Quillaja saponaria, incorporating two types of bicomponent fibers (PLA/PLA and PLA/PBS) as thermal bonding agents. These fibers act as thermal bonding agents through the melting of the PLA (polylactic acid) or PBS (polybutylene succinate) sheath, depending on the fiber type used. The preparation process of quillay fluff pulp is described using different wet and dry refining techniques. The fluff pulp was classified using sieves of different mesh sizes to compare various particle size ranges. To perform the fluffing process, two mixing strategies were evaluated: manual carding and air injection under suspension conditions. The appropriate amount of bicomponent fiber was determined according to the thermal insulation performance and mechanical properties of the resulting material. The thermal properties of the foam were evaluated through a one-dimensional transient heat conduction model solved using Fourier series with orthogonal bases. Due to the absence of ASTMstandard thermal conductivity equipment, this methodology was implemented to preliminarily estimate the thermal properties of the material from experimental measurements. The thermal characterization yielded average values of α = 1,664 × 10−7 m2/s, k = 0,0159W/(m·K), R = 21,4039 K/W (for an area of 0,09 m2), placing the material within the range of high-efficiency thermal insulators. An economic feasibility assessment of the project, considering OPEX, CAPEX, Payback Period, IRR, and NPV, yielded promising results, with an NPV of USD 1,188,683 $ USD and an IRR of 31.68 %. These results provide encouraging evidence that a short-fiber forestry residue can be transformed into a thermal insulation material into a lightweight, reproducible, and competitive thermal insulation material, demonstrating its potential as a sustainable alternative to conventional insulation materials in terms of economic performance as well as thermal and structural properties, establishing a solid basis for future optimization, scale-up, and standardization under ISO or ASTM regulations. Keywords
Description
Tesis presentada para optar al título de Ingeniero/a Civil de Materiales.
Keywords
Morfología, Metalurgia de polvos, Difracción