To cite this article: J. M. Contreras, A. Jiménez-Morales & J. M. Torralba (2010) Experimental and theoretical methods for optimal solids loading calculation in MIM feedstocks fabricated from powders with different particle characteristics, Powder Metallurgy, 53:1, 34-40 To link to this article: http://dx.The aim of this work is to investigate the influence of the particle characteristics of powder to the mixing stage of the powder injection moulding process to identify the best procedure with which to evaluate the optimal solids loading for feedstock fabrication. To perform the present study, powder blends that are made from three bronze and four Inconel 718 powders, with different particle size distributions and morphologies, are mixed with a binder system that is based on polyethylene and wax. Powder-binder blends are prepared by varying the powder content to study how the powder characteristics affect the optimal solids loading. In addition, a new method is presented for determining the optimal solids loading in powder injection moulding feedstocks through the activation energy calculation of powder-binder blends that are prepared with different powder contents. This novel method is compared with the optimal loading values that have been determined by other ways as torque rheometry, determination of the tap-real density ratio and through rheological models.

To cite this article: José M. Contreras, Antonia Jiménez-Morales & José M. Torralba (2008) Improvement of rheological properties of Inconel 718 MIM feedstock using tailored particle size distributions, Powder Metallurgy, 51:2, 103-106 To link to this article: http://dx.

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The MIM technology is an alternative process for fabricating near net shape components that usually uses gas atomised powders with small size (< 20 μm) and spherical shape. In this work, the possibility of changing partially or totally spherical powder by an irregular and/or coarse one that is cheaper than the former was investigated. Different bronze 90/10 components were fabricated by mixing three different types of powder: gas atomised spherical powder (usual MIM powder < 22 μm) and two water atomised irregular powders (size < 35 μm and < 140 μm). The blends were made by using only two types of powder in each mixture with the following volume proportions (100/0, 67/33, 33/67, 0/100). The influence of the particle size and shape on the powder packing density and sintering stage was analyzed through the apparent density of the powder blends, as well as, densification, hardness and porosity of the sintered parts. The addition of irregular and/or coarse powder was found to affect the moulding process, although good densifications and hardnesses were obtained in the sintering step. Therefore it could be a promising way to diminish production costs in this technology.

Los recursos tecnológicos en la estadística bidimensional en los textos españoles de bachillerato Technological Resources in Bidimensional Statistics in High School Textbooks Os recursos tecnológicos na estadística bidimensional nos textos espanhóis do Ensino MédioResumen Los currículos actuales recomiendan el uso de los recursos tecnológicos en la enseñanza de la estadística, por la ventaja que suponen en el cálculo y representación gráfica, el trabajo con datos reales y el aprendizaje de conceptos a través de la simulación. En esta investigación se analizan los recursos tecnológicos que los libros de texto sugieren para la enseñanza y aprendizaje de la estadística bidimensional en bachillerato (organización y representación de datos bidimensionales, correlación y regresión). La importancia de este aspecto se debe a que extiende la dependencia funcional a situaciones aleatorias y proporciona al alumno oportunidades de modelizar numerosas aplicaciones. Por otro lado, la investigación didáctica muestra dificultades de comprensión y concepciones erróneas en esta área. Mediante un análisis de contenido se han estudiado dieciséis libros de texto españoles, ocho libros de cada una de las dos especialidades de bachillerato que incluyen "Humanidades y Ciencias Sociales" y "Ciencia y Tecnología". En dichos libros se estudia el uso que se hace de recursos tecnológicos en los problemas y procedimientos propuestos, los tipos de recursos que se referencian para trabajar con internet y el contenido de un CD que acompaña a la mayoría de estos textos. Los resultados muestran una escasa presencia de recursos tecnológicos en los textos analizados, a la vez que una gran variabilidad de los recursos descritos. La referencia a recursos en internet se suele restringir a unidades didácticas y no a conjuntos de datos que puedan usarse en proyectos o a simuladores que faciliten la comprensión conceptual. El CD que acompaña a los textos a veces reproduce el mismo texto o se reduce a colecciones de ejercicios tradicionales; son minoría los problemas y procedimientos que usan recursos tecnológicos. Se concluye con algunas recomendaciones para la mejora de estos textos, teniendo en cuenta dichos recursos. Palabras clave:Estadística bidimensional, libros de texto, bachillerato, recursos tecnológicos. TED AbstractCurrent curriculums recommend the use of technological resources in the teaching of statistics, due to the help they represent in the calculation and production of graphs, the work with real data and the learning of several concepts through simulation. In this research, we analyse the different technological resources suggested in high school textbooks for teaching and learning bi-dimensional statistics in high school (organization and representation of bi-dimensional data, correlation and regression).The importance of this issue is due to the fact that it extends functional dependence to random situations and provides students with opportunities to model numerous applications. On the other hand, previous research shows many diffic...