In-Situ Nanomechanical Testing

SEM and TEM Heating

Direct measurements and observation of thermally initiated material transformations

With most modern materials, it is not enough to simply measure mechanical properties at room temperature when the material is processed at, or put into service in non-ambient temperatures. To advance understanding of the mechanical behavior of materials at elevated temperatures or in harsh environments, Bruker has developed sample heating upgrade options designed specifically for the SEM and TEM Series PicoIndenter instruments.

Bruker offers two heating options for the Hysitron PI Series instruments at temperatures up to 400°C and 800°C. In-situ heating up to 400°C is accomplished through the use of a resistive MEMS heater. This activates a variety of deformation mechanisms for nanomechanical study, such as the brittle-to-ductile transition in glasses and polymers. Due to the small size of the heating element, the region of elevated temperature is highly localized which minimizes extraneous heating of system components and provides the maximum level of stability for mechanical testing. Temperature is actively measured and feedback-controlled to ensure that the desired value is achieved.

For the PI 85L and PI 89 SEM PicoIndenter instruments, a newly developed heating option enables high resolution in-situ nanomechanical characterization of mechanical properties as a function of temperature. Such testing benefits applications (aerospace, automotive, nuclear, fusion, etc.) which demand high temperature materials capable of reliable performance in extreme operational environments. Featuring active tip heating and a liquid cooled heat sink, the system was designed to maximize the testing temperature, while minimizing drift and heat transfer to the microscope chamber.

Morphology of the bond coating pillars after compression at RT (top-left) and 800°C (top-right). Transgranular cracking can clearly be seen in the pillars tested at room temperature, while intergranular cracks appear only at high temperatures. The stress-strain curves (bottom) indicate major strain hardening at RT, which is more limited at higher temperatures.