Graphite Purification
In RDE Optical Emission Spectroscopy (RDE-OES) used for lubricant and wear debris analysis, electrode purity is the baseline for measurement:
- Spectral Background Noise: If the RDE graphite disk contains trace contaminants (e.g., traces of iron, silicon, or copper), those elements will emit at the exact same wavelengths used to detect wear in the oil sample.
- Elevated Limits of Detection (LOD): Unpure electrodes result in a high background baseline, reducing the signal-to-noise ratio and making it impossible to detect low-level, early-stage engine wear.
- Calibration Drift: The presence of impurities introduces spectral interferences that disrupt the calibration curves of the spectrometer.
The raw materials are first preliminarily purified under high temperature and vacuum to eliminate volatile substances. Halogen-based gases are then fed into the system, with chlorine and fluorine serving as efficient reactants. The process runs at a maximum temperature of 2200 to 2400 °C. Such harsh operating conditions call for top-tier safety protocols and thorough knowledge of material characteristics.
Purity = 99.999868% (based on observed detection limits) TMI=1.32ppmwt
