Chemically produced nanostructured ODS-lanthanum oxide-tungsten composites sintered by spark plasma |
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Authors: | Mazher Ahmed Yar Sverker Wahlberg |
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Affiliation: | a Division of Functional Materials-ICT, Sweden b Royal Institute of Technology (KTH), Stockholm 164 40, Sweden c Department of Mechanical Engineering, American University in Cairo, Egypt d Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden |
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Abstract: | High purity W and W-0.9La2O3 (wt.%) nanopowders were produced by a wet chemical route. The precursor was prepared by the reaction of ammonium paratungstate (APT) with lanthanum salt in aqueous solutions. High resolution electron microscopy investigations revealed that the tungstate particles were coated with oxide precipitates. The precursor powder was reduced to tungsten metal with dispersed lanthanum oxide. Powders were consolidated by spark plasma sintering (SPS) at 1300 and 1400 °C to suppress grain growth during sintering. The final grain size relates to the SPS conditions, i.e. temperature and heating rate, regardless of the starting powder particle size. Scanning electron microscopy revealed that oxide phases were mainly accumulated at grain boundaries while the tungsten matrix constituted of nanosized sub-grains. The transmission electron microscopy revealed that the tungsten grains consist of micron-scale grains and finer sub-grains. EDX analysis confirmed the presence of W in dispersed oxide phases with varying chemical composition, which evidenced the presence of complex oxide phases (W-O-La) in the sintered metals. |
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