System and dynamic volumetric method for surface characterization of porous solids and powder materials using flowing gas

A system for surface characterization of a porous solid or powder sample using flowing gas, the system comprising:

• a first mass flow controller configured to deliver a controllable mass flow of a carrier gas;
• a second mass flow controller configured to deliver a controllable mass flow of an adsorptive gas;
• a mixer having an input coupled to the first and second mass flow controllers and configured to deliver a mixture of the carrier gas and the adsorptive gas to at least a first measurement channel;
• a plurality of measurement channels, each measurement channel coupled to the mixer and comprising:
• a capillary tube;
• a sample cell configured to contain an amount of the sample and flow the mixture over or through the sample;
• a dewar configured to contain liquid nitrogen and positionable to selectively immerse the sample cell in the liquid nitrogen;
• a concentration detector coupled downstream of the sample cell and configured to provide a signal indicative of adsorptive gas concentration in the mixture downstream of the sample cell;
• a delay loop;
• a valve configured to selectively route the mixture to either the concentration detector or the delay loop;
• a flow meter coupled to the concentration detector;
• and
• an atmospheric buffer coupled to the flow meter and atmosphere;
• and;
• a controller coupled to the first and second mass flow controllers, and the concentration detector of each of the plurality of measurement channels, the controller configured to control the first and second mass flow controllers to deliver a varying target concentration of the adsorptive gas in the mixture to the sample cell of each of the plurality of measurement channels and to determine an amount of the adsorptive gas adsorbed and desorbed by each sample cell in the plurality of measurement channels based on signals from the concentration detector in each of the plurality of measurement channels.