Mots-clé
(Anglais)
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intermetallics; nanoparticles; magnetic properties; corrosion; local electrochemistry
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Programme de recherche
(Anglais)
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COST-Action MP0903 - Nanoalloys as advanced materials: from structure to properties and applications
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Description succincte
(Anglais)
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The objective of this research is to develop a method for the synthesis of intermetallic nanoparticles with specific properties and functionalities which can be suitable for technological and medical applications, with focus on magnetic properties. The synthesis method is based on a novel electrochemical selective phase dissolution technique, whose principle has already been demonstrated and now requires extensive fundamental local electrochemical study and further experimental developments to achieve the state-of-the-art.
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Autres indications
(Anglais)
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Full name of research-institution/enterprise: Eidg. Materialprüfungs- und Forschungsanstalt EMPA Laboratory for Corrosion and materials Integrity Abteilung 136
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Partenaires et organisations internationales
(Anglais)
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AT, BE, BG, CH, CZ, DE, DK, ES, FI, FR, IE, IL, IT, LT, PL, RO, RS, SE, SK, TR, UK
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Résumé des résultats (Abstract)
(Anglais)
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Nanoparticles of intermetallic alloys are of special interest because they have potential for several applications (data storage, magnetic tumor targeting, cell separation, drug delivery, hyperthermia and magnetic fluids). Intermetallic nanoparticles with tuned composition are not easily produced by conventional production routes. We developed a novel alternative method for the production of these intermetallic nanoparticles. This method involves two steps: i) production of suitable nano-sized precipitates in a two-phase bulk alloy by solid state diffusion reactions and ii) extraction of the nano-sized precipitates from the bulk alloy by an Electrochemical Selective Phase Dissolution technique (ESPD). The advantages of this method are that the compositions of multi-element nanoparticles are very homogenous, irrespective of their size, and mono crystalline defect-free particles can be produced in a wide size range (from a few nm to micrometer-size) with, for example, strong magnetization. The aim of this project was to further develop the ESPD technique in order to produce intermetallic nanoparticles of different phases having application-oriented properties, with particular focus on magnetic nanoparticles. Particular attention was devoted in this project to the optimization of nanoparticles size and comparison of properties of particles with different sizes. In particular, it was found that the composition and the ordered crystal structure of ý1-Ni3Si phase is maintained by particle size reduction down to 20 nm; this allows preserving the typical characteristics (low electrical resistivity, high corrosion and thermal resistance, mechanical strength) that make this silicide very attractive also in the miniaturized devices. A silica shell surrounding the nanoparticles can be an advantage for applications as it can protect from environmental degradation and also provide attachment sites for polymer, in case functionalization of particles surface is required for achieving stable colloidal suspensions. Recently the possibility of forming stable Co3(Al,W) precipitate phase in high-temperature Co-Al-W alloys has been reported. We investigated the possibility of changing the morphology of the meso-particles extracted from the CAW alloy by tuning the electrolyte pH. Our results demonstrate that superparamagnetic single-crystal Co3(Al,W) nanoparticles can be extracted. The particles are surrounded by an amorphous WO3 shell. Tungsten oxide is a material with interesting opto-electrical properties (electrochromism) and therefore makes these nanoparticles attractive for possible applications where electrochromic properties of the shell and magnetic properties of the core can be combined.
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Références bases de données
(Anglais)
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Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. +41 31 322 74 82 Swiss Project-Number: C11.0045
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