Heating of TEM specimens during ion milling

Area of Science:

• Materials Science
• Physical Metallurgy
• Analytical Chemistry

Background:

• Sample preparation for transmission electron microscopy (TEM) is crucial for accurate material analysis.
• Heating during ion milling can introduce artefacts, compromising the integrity of TEM observations, especially in two-phase materials like metal matrix composites.
• Traditional cooling methods like liquid nitrogen are incompatible with preserving substructure during milling of certain materials.

Purpose of the Study:

• To investigate and quantify sample heating during ion milling for TEM specimen preparation.
• To determine the peak temperatures reached by TEM specimens under conventional milling conditions.
• To analyze the heat transfer mechanisms responsible for specimen heating during ion milling.

Main Methods:

• Experimental determination of peak temperatures in TEM specimens using an age-hardenable aluminium alloy.
• Conducting a simplified one-dimensional heat transfer analysis.
• Investigating heat transfer along sample holder legs and across interfaces.

Main Results:

• Peak temperatures of approximately 650 K were observed with conventional ion milling parameters.
• Heat transfer along the sample holder and across interfaces were identified as critical parameters.
• Temperature differentials within the specimen can reach 60 K under usual milling conditions.

Conclusions:

• Ion milling requires cautious application for materials susceptible to heat-induced artefacts, such as metal matrix composites.
• Understanding and controlling heat transfer pathways is essential to mitigate artefacts during TEM specimen preparation.
• Minimizing specimen heating is vital for preserving substructure and ensuring the validity of TEM observations.