Flowing Gas Surface Characterization With Dynamic Adsorptive Concentration
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Solution Overview
Problem
Current methods for surface characterization of porous solids and powder materials using flowing gas techniques are relative and inferior to static volumetric techniques, lacking accuracy and precision, and often result in plugging of surface pores due to constant adsorptive gas concentrations, which prevents the measurement of full isotherms.
Innovation Solution
A system and method utilizing controllable mass flow controllers for carrier and adsorptive gases, a mixer, and a thermal conductivity detector to deliver varying target concentrations of adsorptive gas, allowing for absolute measurements and preventing pore plugging by dynamically changing gas concentrations during adsorption and desorption steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flowing gas technique is used for surface characterization, then measurement time is reduced and operational cost is lowered, but measurement accuracy and precision deteriorate compared to static volumetric techniques
Solution Approach 1:
The patent dynamically changes the concentration of adsorptive gas in the flowing mixture during measurement. By varying the adsorptive gas concentration as a controlled parameter, the system achieves both rapid data acquisition (improving productivity) and accurate determination of adsorption isotherms (maintaining measurement precision), resolving the contradiction between speed and accuracy.
2Ease of operation
If constant adsorptive gas concentration is maintained in flowing gas technique, then measurement process is simplified, but pore plugging occurs preventing full isotherm measurement
Solution Approach 1:
The patent implements dynamic control of adsorptive gas concentration during the measurement process. The concentration is adjusted in real-time based on the measurement stage, transforming the static concentration approach into a dynamic one. This prevents pore plugging while maintaining operational simplicity through automated control, resolving the contradiction between ease of operation and measurement reliability.
3Measurement precision
If static volumetric technique is used for surface characterization, then measurement accuracy is maintained, but system complexity and operational difficulty increase due to UHV requirements
Solution Approach 1:
The patent extracts the requirement for ultra-high vacuum from the measurement system by using a flowing gas mixture approach. Instead of maintaining UHV conditions, the system uses controlled gas flow with varying adsorptive gas concentrations, eliminating complex vacuum equipment while preserving measurement accuracy through dynamic concentration control.
4Productivity
If flowing gas technique with thermal conductivity detector is used, then measurement speed increases, but measurement accuracy deteriorates due to relative measurement method
Solution Approach 1:
The patent implements a feedback control system where the thermal conductivity detector signal is continuously monitored and used to adjust the adsorptive gas concentration. This closed-loop feedback mechanism enables the system to maintain measurement speed while improving accuracy by dynamically optimizing the measurement conditions based on real-time detector responses.
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
Enables accurate and precise surface characterization with faster measurement times and lower operational costs, achieving results comparable to static volumetric techniques while minimizing pore plugging and improving measurement accuracy.
Implementation Method 1
This change in gas concentration is monitored, typically using a thermal conductivity detector (TCD)
Implementation Method 2
As the sample adsorbs and desorbs gas, the concentration of gas downstream of the sample is reduced and increased, respectively
Implementation Method 3
As the sample adsorbs and desorbs gas, the concentration of gas downstream of the sample is reduced and increased, respectively
Data Source
AI summary
A system and method for surface characterization of a porous solid or powder sample using flowing gas include mass flow controllers configured to deliver a controllable mass flow of a carrier gas and adsorptive gas to vary concentration of the adsorptive gas flowing through at least one measurement channel containing a sample cell. A concentration detector downstream of the sample cell provides a signal indicative of the adsorptive gas concentration to a controller that determines the amount of adsorptive gas adsorbed and/or desorbed to characterize the surface area, pore volume, pore volume distribution, etc. of the sample material. The detector may include a housing, heat exchanger, thermal conductivity detector, and a temperature regulator.