2023 - in-situ SEM reactor for synthesis of battery materials

For project TN02000020

The reactor design is intended to mimic the chemical vapor transport (CVT) reaction inside scanning electron microscope (SEM). CVT is the most utilized approach towards preparation of quantum nanoscale materials, including those for energy harvesting and storage. The developed instrument has been tested with regards to temperature, pressure and imaging requirements of the processes utilized in this project.

The reactor overview, as tested in atmospheric conditions, is shownabove. Reactor housing is made from stainless steel, cooled down by a labyrinth at the base. The reactor lid is removable, to allow for mounting, sample insertion and cleaning. The source heater is made in-house, by a rolled tungsten filament within a ceramic housing; the source itself is placed within a fused silica tube (similar to common CVT reactors). The sample heater utilizes pBN heating element, commercialized by Momentive. Gas flows are ensured via Swagelok-attached mountings to stainless steel tubes,

The source heater assembly was tested first independently. The resulting maximum operating temperature - 1000 °C – is limited by the material used. In principle, custom changes can be made to reach higher temperature. The sample heater is designed by manufacturer for temperatures up to 1000 °C as well. Both heaters are compatible even with ultra-high vacuum levels (down to 10-7 Pa). The crosstalk in between them cannot be avoided, but using well-set PID controller helped to achieve stable temperature levels during testing.

The vacuum level depends on the lid, which is used:

  • With fully closed lid, the reactor can be operated even as a tabletop CVT reactor, allowing to reach base pressure of 10-2 Pa with surrounding atmospheric conditions
  • In the evacuated SEM chamber (10-2 Pa) the pressure within the reactor can reach one range of magnitude higher if a lid with 1 mm opening is used.

Main characteristics of the reactor:

  • Vacuum compatibility: from atmospheric conditions down to 10-6 Pa; in-SEM operation granted with SEM pressures at 1.10-2 Pa
  • Temperature ranges: source heater up to 800 °C, sample heater up to 1000 °C
  • Possibility to observe the sample during reaction via different apertures in the lid

 

 

Projekt TN02000020 Centrum pokročilé elektronové a fotonové optiky je spolufinancován  se státní podporou Technologické  agentury ČR v rámci Programu Národní centra kompetence.