Quantitative analysis of carbon in cementite using pulsed laser atom probe

Area of Science:

• Materials Science
• Analytical Chemistry
• Metallurgy

Background:

• Accurate carbon quantification in materials like cementite is crucial for understanding their properties.
• Pulsed-laser atom probe tomography (APT) is a powerful technique for nanoscale chemical analysis.
• Standardization of APT methods is essential for reliable material characterization.

Purpose of the Study:

• To quantify carbon in pure cementite using pulsed-laser APT.
• To investigate the influence of experimental parameters on carbon quantification accuracy.
• To identify potential sources of error in APT analysis of cementite.

Main Methods:

• Pulsed-laser atom probe tomography (APT) was employed for elemental analysis.
• Pure cementite specimens were analyzed under varying laser pulse energy, cryogenic temperature, and pulse frequency.
• Apparent carbon content was measured and compared to the stoichiometric ratio.

Main Results:

• All APT measurements yielded an apparent carbon content of 25.0±1.0at%.
• Carbon quantification showed no significant dependence on cryogenic temperature or laser pulse frequency.
• A strong correlation was observed between laser pulse energy and measured carbon content.
• Lower laser pulse energies led to overestimation of carbon, attributed to Fe(++) ion pile-up and loss.
• Higher laser pulse energies resulted in underestimation, linked to the detection of multiple carbon molecular ions.

Conclusions:

• Laser pulse energy is a critical parameter affecting carbon quantification in cementite by APT.
• Understanding ion detection artifacts, such as pile-up and multiple events, is vital for accurate APT analysis.
• The study highlights the need for careful optimization of APT parameters for reliable material quantification.