Determination of Moisture and Ash in Graphite (TGA801)

Significance of the Topic

Graphite is a critical material in applications ranging from batteries to aerospace due to its unique conductive and mechanical properties. Accurate determination of moisture and ash content is essential to assess purity and performance in these high-value markets.

Study Objectives and Overview

This application note demonstrates two modified ASTM-based thermogravimetric methods for quantifying moisture and ash in graphite. The goal is to compare a standard multi-step ash protocol with an accelerated single-step approach while verifying precision and consistency.

Instrumentation

• LECO TGA801 macro thermogravimetric analyzer capable of analyzing up to 19 samples in parallel
• Ceramic crucibles and sample scoops
• Controlled atmosphere flow: air for moisture steps and oxygen for ash steps
• Nominal sample mass of 2.0 g to optimize sensitivity for low ash levels

Methodology

Samples were ground to <1.0 mm for uniformity. Two methods were executed on the TGA801:

• Method 1 follows moisture removal at 110 C under air, then two ash steps up to 750 C under oxygen
• Method 2 uses a faster moisture ramp and a single combined ash stage from 110 C to 950 C
• Key parameters include ramp rates (6 to 15 C/min), hold times (2 to 60 min), and flow rates (8 to 10 L/min)

Main Results and Discussion

Both methods produced comparable moisture values (0.03 to 0.12%) and ash contents (0.08 to 0.97%) across three sample types. Method 2 reduced total analysis time by nearly half (4 h vs. 7.5 h) while maintaining repeatability (standard deviation <= 0.02%).

Benefits and Practical Applications

• Robust quality control for battery-grade graphite and carbon fibers
• Improved throughput with accelerated ash protocol
• Reliable monitoring of purity levels critical to performance and compliance

Future Trends and Opportunities

Advances may include integration of real-time data analytics, coupling TGA with evolved gas analysis, and further automation to enhance throughput and material characterization depth.

Conclusion

The LECO TGA801, combined with modified ASTM C561 and C562 methods, delivers accurate moisture and ash measurements for graphite. The optimized single-step ash protocol offers a faster alternative without sacrificing data quality.

References

• ASTM C561: Standard Test Method for Ash in a Graphite Sample
• ASTM C562: Standard Test Method for Moisture in a Graphite Sample