Preparation of Specimens for Bulk Analysis Using LECO Glow Discharge Spectrometers

Importance of the Topic

Glow Discharge Atomic Emission Spectrometry (GDS-AES) is a powerful technique for bulk elemental analysis of diverse materials, including metals, powders, thin films, and irregular geometries.

Its ability to analyze small or thin samples, perform depth profiling, and provide rapid, representative results makes it indispensable for materials characterization, quality control, and research in industrial and academic laboratories.

Objectives and Study Overview

This application note presents recommended procedures to prepare various sample types—blocks, powders, wires, thin sheets—for analysis on LECO GDS systems (GDS500A and GDS850A).
It aims to ensure proper vacuum sealing, electrical contact, and sample integrity to achieve accurate and reproducible analytical results.

Methodology and Sample Preparation Techniques

Sample preparation is critical for ensuring vacuum seal and electrical circuit completion. Key techniques include:

• Surface Flattening and Abrasion: Use belt grinders or wheel polishers to obtain a flat analytical face and remove coatings or treatments.
• Sectioning: Employ thin-blade metallographic saws to expose the largest flat area for analysis and conserve material.
• Mounting in Conductive Media: Embed small samples (<15 mm) in copper-filled diallyl phthalate to complete electrical contact and improve heat dissipation.
• Pressing: Use a hydraulic press to expand marginally sized samples or densify porous materials, improving contact area.
• Reusable Holders: Utilize custom holders for uniform rods and wires (>3 mm) to facilitate routine analysis.
• Forging: Consolidate wires or springs into a single mass before analysis using a peening hammer.
• Powder Pelleting: Press metal and non-metal powders into disks for direct analysis, ensuring lubricant removal via thermal treatment at 650 °C in inert atmosphere.
• Thin Sample Bonding: Adhere sheets <0.5 mm to conductive substrates with two-part epoxy to provide rigidity and cooling.

Used Instrumentation

• LECO GDS500A and GDS850A Glow Discharge Spectrometers
• Metallographic sectioning saws and X–Y tables
• LECO BG-30 belt grinder
• Hydraulic press (20 ton capacity)
• Metallographic mounting press (LECO PR-32)
• Thermosetting mounting media: copper-filled and blue diallyl phthalate
• LECO TGA muffle furnace for de-lubing powders
• Two-part quick-setting epoxy and conductive substrates for thin specimens

Main Results and Discussion

Proper sample preparation yields reliable vacuum sealing, consistent electrical contact, and reproducible spark initiation. Techniques tailored to sample morphology reduced failure rates associated with poor vacuum and overheating. Depth profiling capabilities were highlighted for coated materials, emphasizing the importance of surface removal to access bulk chemistry.

Benefits and Practical Applications

• Enables analysis of large, irregular, small, and thin samples without specialized instrumentation.
• Improves throughput by minimizing sample rejection due to poor seal or contact.
• Supports depth profiling of coatings and substrates for quality control in plating, galvanizing, and thin-film processes.
• Offers versatile powder analysis for metal and non-metal powders used in additive manufacturing and ceramics.

Future Trends and Opportunities

Advances in GDS software and hardware will further streamline sample preparation and depth profiling, enabling real-time coating analysis and automated handling of micro-samples. Development of novel conductive mounts and low-temperature bonding agents may expand analysis to temperature-sensitive materials. Integration with robotic sample loaders promises higher throughput in industrial QA/QC environments.

Conclusion

A systematic approach to sample preparation—flattening, sectioning, mounting, pressing, and bonding—ensures accurate and reproducible GDS-AES analyses across diverse material types. Careful attention to vacuum seal, electrical contact, and thermal management maximizes data quality, making LECO GDS systems a versatile tool for bulk and depth profiling applications.

Reference

• LECO Corporation. Glow Discharge Spectrometers Electronic Manual. Form No. 209-076-031 (2012).