Waveform Jitter Caused by Local Heterogeneity in Tungsten Carbide Powder Samples and Its Suppression for Improved Carbon Quantification Reproducibility
Year: 2026
Type: article
Abstract: Tungsten carbide (WC) powder is widely used in cemented carbide tools, and tight control of carbon content is critical for quality. High-frequency induction combustion with non-dispersive infrared (NDIR) detection provides rapid and accurate carbon analysis, but high-carbon WC powders often show temporally non-uniform gas release during combustion. This causes waveform jitter in the NDIR signal and reduces quantitative reproducibility. In this study, particle size distribution measurements of a WC certified reference material appeared consistent, whereas SEM observations revealed run-to-run differences in local aggregation and mixing. This structure, which is macroscopically uniform in particle size distribution (PSD) yet microscopically heterogeneous due to local aggregation and mixing, is proposed as a plausible source of jitter via fluctuations in combustion progress and intermittent CO2 release. To suppress jitter, we increased the effective volume of the extraction gas line and tuned the system time constant (τ = V/v) to physically smooth the transient signal. For a WC certified reference material (C = 6.188%) measured in five replicates (n = 5), the RSD improved from 1.09% under baseline conditions to 0.10% after volume addition. Time-constant-based smoothing is therefore an effective design approach to enhance reproducibility in combustion–NDIR quantification of powder materials.
Institution: Horiba (Japan)
Language: English
Subfield: Analytical Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: diamond
OpenAlex ID: W7160065643