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Östermalm, Sweden

Eriksson M.,University of Stockholm | Radwan M.,Diamorph AB | Shen Z.,University of Stockholm
International Journal of Refractory Metals and Hard Materials | Year: 2013

Spark plasma sintering (SPS) is an extremely fast solidification technique for compounds that are difficult to sinter within the material group's metals, ceramics, or composites thereof. SPS uses a uniaxial pressure and a very rapid heating cycle to consolidate these materials. The heating is generated by Joule effect when a strong, pulsed electric current passes the conductive graphite die and also through the sample, if conductive. Cemented carbides (hard metals) are mostly used for metal cutting and drilling, wood cutting or rock drilling tools and are consolidated either by pressureless sintering (PLS), hot pressing (HP), or hot isostatic pressing (HIP). With SPS the main benefit is the ability to control the WC grain size due to the short sintering times at high temperature. In addition, unwished reactions between WC and cobalt to form other phases are minimized. By SPS the amount of cobalt can be reduced towards zero in fully dense WC materials. With this technique it is easy to prepare gradient materials where a ductile weldable metal can be joined with the cemented carbide part. © 2012 Elsevier Ltd.

Diamorph Ab | Date: 2011-09-27

The invention relates to a nitride nuclear fuel characterized in that the nitride fuel is a pellet of a material with a single-phase solid solution of elements comprising at least a nitride of americium (Am), and that the material has a density of around 90% of the theoretical density. The invention further relates to a method for producing the said nuclear fuel by using the steps: mixing of starting powders, sintering of the powders into a dense pellet and a subsequent heat treatment.

The invention relates to a functionally graded material shape (

Xu C.,CAS Shanghai Institute of Ceramics | Cai Y.,University of Stockholm | Flodstrom K.,Diamorph AB | Li Z.,University of Aarhus | And 2 more authors.
International Journal of Refractory Metals and Hard Materials | Year: 2012

Boron carbide (B4C) ceramics, with a relative density up to 98.4% and limited grain growth, were prepared at 1600-1800 °C by spark plasma sintering (SPS) technique. The effects of powder milling medium (water and 2-propanol) on the powders' surface characteristics and TiB2 addition on the sintering densification were investigated. The ball milling processing of B4C powders in water can promote the sintering of B4C ceramics. A B2O3 layer on B4C particle surface is concluded to promote the densification of the B4C ceramics at an early sintering stage. This B2O3 layer, which normally inhibits the densification process at the final stage of the sintering, can be reduced through reaction with TiB2 particles, resulting in further densification of the B4C ceramics. © 2011 Elsevier Ltd. All rights reserved.

Radwan M.,University of Stockholm | Radwan M.,Diamorph AB | Nygren M.,University of Stockholm | Flodstrom K.,Diamorph AB | And 2 more authors.
Journal of Materials Science | Year: 2011

This paper describes the preparation of crack-free stainless steel 316L/alumina functionally graded material (SUS316L/Al2O3 FGM) by spark plasma sintering (SPS). The sintering of individual powders and their composites was first studied to find an optimum SPS condition to get both materials and their mixtures highly dense. Sintering of cylindrical-shaped FGM pellets (φ20 mm) with various numbers of interlayers of 1, 2, 3, 4, and 9 was then carried out where the kind of and location of related cracking were carefully examined. The FGMs faced the problem of cracking mainly in the radial direction near the Al2O3-rich layers regardless of the number of layers or the gradient compositional profile. An yttrium-stabilized zirconia (3Y-ZrO2) was added thereafter to the gradient on the expense of Al2O3 content (up to 50 vol.%) and no radial cracking was found. Defects-free FGM pellets were successfully produced by interposing 19 interlayers between the SUS316L and Al2O3 ends. The Vickers hardness profile was determined throughout the cross-section of sintered FGM and it was varying steadily through the gradient from 2.0 GPa at the SUS316L surface to 14.4 GPa at the Al2O3 surface. © 2011 Springer Science+Business Media, LLC.

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