Comparison of Copper Diallyl Phthalate and Conductotherm 3000 Sample Mounting Media

Importance of the Topic

Small or irregularly shaped samples often fall below the minimum diameter required for direct analysis in glow discharge spectrometry. Properly chosen conductive mounting media ensure vacuum integrity, stable electrical contact, and effective heat dissipation during analysis on instruments such as the GDS500A. This directly impacts data accuracy, instrument safety, and workflow efficiency.

Objectives and Study Overview

This application note evaluates two conductive mounting materials—copper diallyl phthalate and Conductotherm 3000—under various lamp configurations of the GDS500A glow discharge spectrometer. The goal is to compare their thermal management, electrical performance, ease of use, cost, and influence on analytical results.

Methodology and Instrumentation

Instrument:

• GDS500A glow discharge spectrometer with direct‐current lamp
• 4 mm lamp (standard), optional 2 mm anode, and separate 2 mm lamp

Mounting Workflow:

• Place sample in metallographic mounting press with analytical surface facing down
• Add mounting media, run heat and pressure cycle per manufacturer instructions
• For bulk analysis, grind or polish the mounted surface flat; skip further prep for depth profiling
• Secure the mount over the lamp anode, verify sputter crater location to confirm sample coverage

Main Results and Discussion

Comparison of Media Performance:

• Copper Diallyl Phthalate
  • Dense copper content provides superior thermal conductivity, reducing sample overheating
  • Maintains vacuum seal and electrical path, but can deposit copper signal if media is sputtered
  • Higher material cost and requires thorough cleaning of press platen due to sticking
• Conductotherm 3000
  • Graphitic, carbon‐based medium with good electrical conductivity at lower cost
  • Less effective at heat dissipation, prone to cracking under 4 mm lamp conditions, leading to vacuum leaks or arcing at anode edge
  • Elevated carbon background can appear if sample overheats

Benefits and Practical Applications

Selecting the appropriate mounting medium enhances analytical accuracy and instrument longevity. Recommended material amounts per mount diameter:

• Copper Diallyl Phthalate (PN 811-138, PN 811-139)
  • 50 g for 1.25 in mount; 80 g for 1.5 in mount
• Conductotherm 3000 (PN 812-233)
  • 20 g for 1.25 in mount; 30 g for 1.5 in mount

General Mounting Tips:

• Ensure full encapsulation of tall samples; grind a flat surface before mounting when possible
• Center the sample in the press and add media evenly around it
• Implement dust safety precautions during handling and grinding

Future Trends and Applications

Research in mounting media is moving toward customized composite formulations that balance electrical conductivity, thermal management, and minimal spectral interference. Advances in automated mounting presses and integration with in situ surface conditioning may further streamline glow discharge workflows. Additionally, additive manufacturing techniques could enable bespoke mounts for complex geometries.

Conclusion

The choice between copper diallyl phthalate and Conductotherm 3000 depends on analytical priorities: copper‐based mounts excel in heat dissipation and vacuum integrity but at a higher cost, while carbon-based mounts offer cost savings and ease of cleaning but may introduce overheating risks under high‐power lamp configurations. Proper media selection and adherence to mounting best practices ensure reliable glow discharge analysis.

References

• LECO Corporation. Spectroscopy Performance Note, Form No. 209-076-049, Revision 0, 2017.