Science photo awarded prize

IPP scientist Johann Riesch wins NuMart Image Competition

January 28, 2019
A specimen of tungsten-fibre-reinforced tungsten after a breaking test, viewed through an electron microscope. The plastically deformed and ruptured tungsten fibres in the brittle, broken tungsten matrix reveal the processes that contribute to enhancement of the material’s fracture toughness. The fibres have a diameter of 150 micrometres.

First prize in Elsevier’s “NuMart Image Competition” has been awarded to IPP scientist Dr. Johann Riesch from the Plasma Edge and Wall research division. Applicants had been requested to submit their most interesting materials photos. Of the 20 photos shortlisted Johann Riesch’s entry was declared winner by the 800 participants at the Nuclear Materials Conference in Seattle, USA, in October 2018.

The winning photo features an electron-microscopic image of tungsten-fibre-reinforced tungsten after a breaking test. The composite material developed by Johann Riesch and colleagues consists of a tungsten matrix in which thin tungsten wires 150 micrometres in diameter are embedded. The photo, taken by Dr. Martin Balden, impressively shows how these fibres enhance the fracture toughness of the tungsten metal.

Cover of Journal of Nuclear Materials, Jubilee issue 2019

The background to this work is the search for a material for the heavily stressed parts of the vessel enclosing the hot fusion plasma. This is where tungsten comes in, being the metal with the highest melting point. It, however, involves the disadvantage of high brittleness. Any punctual stress – tension, stretching or pressure – cannot be circumvented by tungsten slightly yielding. Cracks form instead. In the search for structures capable of distributing local tension IPP took their cue from fibre-reinforced ceramics and came up with the solution: tungsten-fibre-reinforced tungsten. As documented by the winning photo, it affords greatly improved material properties. If the tungsten matrix fails under stress, the tungsten fibres can bridge the crack and stop it.

Since January last year’s winning photo has now adorned the cover of the jubilee issue of journal of Nuclear Materials. The Journal, published by Elsevier, is appearing in 2019, its 60th year.

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