Trace Carbon Analysis in Steel Using Cryogenic Traps
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Solution Overview
Problem
Current methods for quantitative carbon analysis in steel materials are hindered by contamination issues, particularly when using electron microscopes, as residual gas components decompose and adhere to the sample, making it difficult to distinguish between target carbon and contamination, leading to inaccurate measurements.
Innovation Solution
A device and method combining a liquid nitrogen trap and a plasma or oxygen radical generator, along with multiple wavelength dispersive X-ray spectrometers, are used to reduce contamination and accurately quantify trace carbon by detecting characteristic X-rays, while a sample heating section and sputtering section are optionally employed to further mitigate contamination effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electron beam irradiation is used for carbon analysis, then local carbon concentration can be measured, but contamination adheres to the sample surface making accurate measurement difficult
Solution Approach 1:
The liquid nitrogen trap is activated before electron beam irradiation to pre-cryogenically condition the sample surface and trap residual gases. This preliminary cooling action prevents contamination adhesion during subsequent analysis, allowing accurate carbon concentration measurement without the harmful effects of carbon buildup on the sample surface.
Solution Approach 2:
Liquid nitrogen serves as an intermediary substance between the vacuum environment and the sample surface. By introducing liquid nitrogen vapor and cold zones, it mediates the interaction between residual gases and the sample, preventing direct adhesion of contaminant molecules to the sample surface during electron beam irradiation.
2Measurement precision
If analysis time is extended to improve quantification accuracy, then more precise carbon distribution data can be obtained, but contamination increases over time
Solution Approach 1:
The sample chamber is pre-cooled with liquid nitrogen before analysis begins, and the trap is activated in advance to establish a low-contamination environment. This preliminary preparation allows extended analysis times to proceed without the progressive contamination that would normally limit measurement duration, maintaining accuracy throughout the full analysis period.
Solution Approach 2:
The system employs periodic activation of the liquid nitrogen trap during analysis to maintain low contamination levels. By intermittently replenishing cold traps or reconditioning the vacuum environment, the system can sustain long analysis durations without cumulative contamination buildup, enabling both high precision and extended measurement time.
3Measurement precision
If multiple carbon detecting sections are added to improve measurement accuracy, then trace carbon can be quantified without contamination influence, but device complexity increases
Solution Approach 1:
The WDS system is segmented into multiple independent detecting sections, each equipped with its own analyzing crystal and detector optimized for specific carbon detection tasks. This segmentation allows simultaneous multi-point measurement or redundant verification of carbon signals, improving accuracy through spatial or spectral differentiation while maintaining modular device architecture that manages complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise quantitative analysis of trace carbon without contamination influence, improving sensitivity and accuracy in both point and area analyses, with reduced contamination over time, allowing for reliable determination of carbon distribution in steel materials.
Implementation Method 1
a liquid nitrogen trap configured to trap residual gas in the sample chamber through cooling using liquid nitrogen
Implementation Method 2
a plasma or oxygen radical generator configured to blow plasma or oxygen radicals onto a sample surface in the sample chamber
Implementation Method 3
carbon detecting sections each configured to detect a characteristic X-ray of carbon emitted from a sample irradiated with an electron beam
Implementation Method 4
the carbon detecting sections are each a wavelength dispersive x-ray spectrometer having an analyzing crystal (9) and an x-ray detector
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention makes it possible to analyze trace carbon in a sample without the effects of contamination. In an electron probe microanalyzer, a liquid nitrogen trap (6) and a plasma or oxygen radical generator are jointly used as a means for suppressing contamination, and two or more carbon detection units (9, 10) for detecting characteristic x-rays (8) of carbon in the sample (7) are provided.