Browsing by Author "Kaltzakorta, I."
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Item Effects of nanoparticle addition on hardening and tempering steel(2014-11-01) Callejo, L. M.; Kaltzakorta, I.; CIRMETAL; Tecnalia Research & InnovationThe effects of nanoparticle addition on the hardening and tempering 20MnCr steel have been investigated. Addition of oxide nanoparticles to the melt, through a new technology that ensures safe handling, was found to give as hardened steel hardness and tensile properties close to those of the conventional steel in the hardened and tempered condition. This has the potential to eliminate the tempering step in component production, with benefits for process efficiency. The effects on microstructure, hardness and tensile properties depend on the type and concentration of the nanoparticles added. The reduced tensile strength and hardness, and increased ductility, of the steels with nanoparticle additions are attributed to the presence of retained ferrite in these microstructures, in both the hardened and tempered condition. It is proposed that the application of this approach at an industrial scale has the potential to reduce energy consumption, cost and time in component production through the elimination of intermediate operations such as tempering.Item Synthesis and characterization of epoxy encapsulating silica microcapsules and amine functionalized silica nanoparticles for development of an innovative self-healing concrete(2015-09-01) Perez, G.; Erkizia, E.; Gaitero, J. J.; Kaltzakorta, I.; Jiménez, I.; Guerrero, A.; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Tecnalia Research & Innovation; CIRMETALSilica microcapsules encapsulating an epoxy compound (CAP) and silica nanoparticles functionalized by an amine group (NS) are synthesized to be used as self-healing system for smart cementitious composites. The innovative character of this system comes from the use of silica shell microcapsules to improve the durability and compatibility with the cement and from the use of functionalized nanosilica to obtain an amine functionalized cementitious matrix. Characterization of the particles indicates that they are amorphous and possess a proper morphology and size to be considered as additions to cement. The stability of the epoxy compound inside the microcapsules and the presence of amine groups bonded to silica nanoparticles are also confirmed. Moreover, NS shows a pozzolanic activity superior to that of the silica fume used as reference, while CAP is to a high degree stable upon reaction with lime. The results confirm that the synthesized particles are a suitable starting point to address the development of a smart self-healing concrete.