Processing and sintering of yttrium-doped tungsten oxide nanopowders to tungsten-based composites

• Published in: Journal of materials science Vol. 49; no. 16; pp. 5703 - 5713
• Main Authors: Yar, Mazher Ahmed, Wahlberg, Sverker, Abuelnaga, Mohammad Omar, Johnsson, Mats, Muhammed, Mamoun
• Format: Journal Article
• Language: English
• Published: Boston Springer US 01.08.2014; Springer; Springer Nature B.V
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Composite materials; Composite materials industry; Crystallography and Scattering Methods; Density; Grain growth; Grain size; Homogeneity; Hydrogen; Hydrogen reduction; Inclusions; Materials Science; Morphology; Nanostructure; Organic chemistry; Plasma sintering; Polymer Sciences; Rare earth elements; Rare earth metals; Reduction; Sintering; Sintering (powder metallurgy); Solid Mechanics; Spark plasma sintering; Tungsten; Tungsten compounds; Tungsten oxides; Yttrium oxide; Spark Plasma Sinter; Tungsten Powder; Powder Layer; Y2O3; Tungsten Oxide
• ISSN: 0022-2461; 1573-4803; 1573-4803
• DOI: 10.1007/s10853-014-8289-x

Innovative chemical methods are capable of fabricating nanoscale tungsten oxide compounds doped with various rare-earth elements with high purity and homogeneity, which can be processed under hydrogen into nanostructured oxide-dispersed tungsten composite powders having several potential applications. However, hydrogen reduction of doped tungsten oxide compounds is rather complex, affecting the morphology and composition of the final powder. In this study, we have investigated the reduction of tungstic acid in the presence of Y and we provide the experimental evidence that Y 2 O 3 can be separated from Y-doped tungstic acid via hydrogen reduction to produce Y 2 O 3 -W powders. The processed powders were further consolidated by spark plasma sintering at different temperatures and holding times at 75 MPa pressure and characterized. The optimized SPS conditions suggest sintering at 1400 °C for 3 min holding time to achieve higher density composites with an optimum finer grain size (3 µm) and a hardness value up to 420 H V . Major grain growth takes place at temperatures above 1300 °C during sintering. From the density values obtained, it is recommend to apply higher pressure before 900 °C to obtain maximum density. Oxides inclusions present in the matrix were identified as Y 2 O 3 ·3WO 3 and Y 2 O 3 ·WO 3 during high resolution microscopic investigations.