Alumina-Based Functional Materials Hardened with Al or Ti and Al-nitride or Ti-nitride Dispersions
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Alumina-Based Functional Materials Hardened with Al or Ti and Al-nitride or Ti-nitride Dispersions José G. Miranda-Hernández1, Elizabeth Refugio-Garcia1, Elizabeth Garfias-García1 and Enrique Rocha-Rangel2 1 Departamento de Materiales, Universidad Autónoma Metropolitana Av. San Pablo No. 180, Col. Reynosa-Tamaulipas, México, D. F., 02200. 2 Universidad Politécnica de Victoria, Avenida Nuevas Tecnologías 5902, Parque Científico y Tecnológico de Tamaulipas, Ciudad Victoria, Tamaulipas, 87137, México
ABSTRACT The synthesis of Al2O3-based functional materials having 10 vol. % of fine aluminum or titanium and aluminum-disperse or titanium-dispersed nitride hardened-particles has been explored. Two experimental steps have been set for the synthesis; specifically, sintering of Al2O3-aluminum or Al2O3-titanium powders which were thoroughly mixed under high energy ball-milling, pressureless-sintered at 1400ºC during 1 h in argon atmosphere and then for the second step it was induced formation of aluminum nitride or titanium nitride at 500°C during different times (24, 72 and 120 h) by a nitriding process via immersion in ammoniac salts. SEM analyses of the microstructures obtained in nitride bodies were performed in order to know the effect of the ammoniac salts used as nitrating on the microstructure of aluminum or titanium for each studied functional material. It was observed that an aluminum nitride or titanium nitride layer growth from the surface into the bulk and reaches different depth as the nitriding time of the functional material was increased. The use of aluminum or titanium significantly enhanced density level and hardness of the functional materials.
INTRODUCTION Functionally Graded Materials (FGMs) are a new generation of composite materials which allow a more efficient use of existing homogeneous materials (composites) by introducing gradual gradients of composition, microstructure, texture, phase distribution or particle content in their structure [1-2]. Mainly the FGMs have hard phase in the surface and lower hard phase in the body [3]. The first industrial applications of the FGM concept have emerged in production of cermets cutting tools in 1996 by Sumitomo Electric Industries, Ltd [4]. Since then, the FGMs are also applied in where operating conditions are rigorous, for example, rocket heat shields, heat exchanger tubes, thermoelectric generators, heat-engine components, thermomechanical loads, biomaterials, electronic materials and electrically insulating metal/ceramic joints [5]. The FGMs can be constituted by carbide ceramics, oxide ceramics and metals, and they can be used in application at high temperatures such as in the construction of gas turbine engines in order to increase their thermal cycle efficiency. There are several methods in order to produce them, such as: chemical vapour deposition CVD, phisycal vapour deposition PVD, plasma spraying, powder metallurgy and selfpropagating high-temperature synthesis (SHS) [6-8]. It is well known that Al2O3-based ceramics possess excellent physical and
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