Publication Reviews

Micro Materials Publication Reviews are designed to highlight some of the exciting work being carried out in the field of nano-mechanical testing using NanoTest systems. Taken from peer-reviewed papers, they concisely describe the instrument used, the research and the results obtained. They cover a diverse range of applications, often using unique capability that only Micro Materials can offer.

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Extreme nanomechanics: vacuum nanoindentation and nanotribology to 950 °C

 

Extreme nanomechanics: vacuum nanoindentation and nanotribology to 950 °C

Adrian J. Harris, Ben D. Beake and David E. J. Armstrong – Tribology – Materials, Surfaces & Interfaces 2015 VOL. 9 NO. 4 174-180

Suggested Audience:

  • Nuclear materials researchers
  • Silicon/microelectronics researchers
  • Tribologists
  • Wear-resistant coatings developers
  • High temperature materials researchers

The Instrument:

NanoTest Xtreme – nanomechanical testing in vacuum up to 950 °C

  • Vacuum levels of up to 10-6 mbar virtually eliminates oxidation of samples.
  • Independent, active heating of the sample and the indenter provides ultra-low thermal drift even at very high temperatures, allowing long-duration indentation tests to be carried out.

The Research:

Nanoindentation has already been used successfully to characterise near surface properties of tungsten (W) based alloys – one of the most promising potential materials for nuclear fusion reactor cladding. Until recently, 750 °C indentation was the practical limit for the technique of high temperature nanoindentation.

In this study high temperature nanoindentation measurements were performed on a single crystal tungsten sample at temperatures up to 950 °C within a vacuum environment. Experiments were performed at room temperature, 500 °C , 750 °C, 800 °C, 850 °C, 900 °C and 950 °C.

The Results:

The review highlights the capability to do measurements up to 950 ºC and also the importance of time-dependent behaviour (i.e. creep) at these high temperatures.

Low thermal drift is critical in accurately assessing time-dependent behaviour. Typical thermal drift at 950 ºC was 0.1 nm/s or less.

In addition to the work on tungsten, other findings included:

Silicon – a relatively strain-rate insensitive material at 25 ºC – is shown to behave completely differently at 500 ºC and above.
Increased creep on Solid Oxide Fuel Cell (SOFC) glass-ceramic materials above their glass transition temperature.

The wide range of nano and micro-tribology tests also possible at high temperature is also illustrated with some examples on hard coatings.

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