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Capillary Condensation Flow Porometer
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Description
The PMI Capillary Condensation Flow Porometer passes moist air through a sample held in the sample chamber. The amount of moisture in the air is increased until the pores in the sample are saturated, thus stopping the flow of the moisturized air through the sample. Pore size is determined by the pressure at which the moisture condenses into the pores.
Principles of Operation
At a given temperature, a vapor at a pressure less than the vapor pressure, Po, in equilibrium with its liquid can condense in pores of a material. Kelvin equation gives the diameter of the pore in which condensation can occur at the relative vapor pressure, (P/ Po).
where γ is the surface tension of condensed liquid, V is the molar volume of condensed liquid, θ is the contact angle of the liquid with the pore surface, D is the pore diameter, R is the gas constant, and T is the absolute test temperature. At the lowest relative vapor pressure, (P/ Po), condensation occurs in the smallest pore. On increase of relative vapor pressure condensation occurs in larger pores.
The instrument is maintained at the desired temperature. Vapor is introduced in to the sample chamber of known volume. The vapor pressure is monitored until the system comes to equilibrium. From the final pressure, the diameters of pores in which condensation occurs are computed. A small amount of vapor is added to one side of the sample in the sample chamber so as to raise the pressure on that side by about 10 %. The decay of pressure is monitored as a function of time. Gas flow rates through the pores of the sample which do not contain condensed liquid at the maintained pressure of the vapor are computed from the time rate of pressure change. From repeated determination of flow rates at a number of vapor pressures, the flow rate distribution is computed.
Applications
The PMI Capillary Condensation Flow Porometer has the unique ability to measure gas permeability and flow rate distribution in addition to measuring pore diameter of nanopore samples without using any toxic materials or extreme pressures and temperatures. No other instrument has such capabilities. It is utilized for characterization of porous membranes used in many industries such as:
without any fear of harmful effects of high pressures and extreme temperatures on samples. Fragile samples with small pores can be easily evaluated by this technique.
For more information about the applications please see our other technical papers.
Features
- Fully automated, simple to use & very little operator involvement
- Highly reproducible & accurate
- Pressure required is very small.
- Normally liquid nitrogen temperatures are not required
- A wide variety of samples can be investigated
- No toxic material like mercury is used. No health hazard. No disposal related cost.
Specifications
For more information see our Capillary Condensation Flow Porometer Brochure, Porometers Brochure, and Characterization of Pore Structure Brochure.
