Micro-hole test common sense - Database & Sql Blog Articles

Microporous

Micropores refer to pores having a pore size of less than 2 nm;

2. Conventional test methods for micropores

â—Ž Instruments for measuring mesopores and

Mesoporous analysis

The basic assumption is that it extends in the direction of the micropore, and the pore size and filling pressure are still treated by the Kelvin equation; 2 the nitrogen filled in the pores takes the density of liquid nitrogen;

◎ The total pore volume and total internal surface area of ​​micropores below <2 nm can be obtained by t-graph method or D&R method;

The pore volume/pore size distribution between 2 nm and ~1 nm can also be roughly calculated by the MP method;

◎ The key is: to select the “standard isotherm”, you need a database with “standard isotherm” and the correct analysis method;

â—Ž Disadvantages: the basic assumptions of mesoporous analysis are still used to analyze micropores is not accurate; the isothermal adsorption curve and precise micropore pore volume/pore diameter distribution in the micropore region cannot be accurately determined;

3. Accurate test method for micropore distribution

â—Ž with the above

Test method

There are significant differences;

◎ Micro-hole precision test equipment has extremely high vacuum requirements. The actual vacuum of the test system needs to be ≤10 ^-3 Pa, and the relative pressure of nitrogen P/Po needs to be of the order of 10 ^-8 . Therefore, a two-stage vacuum system, that is, a mechanical pump is required. Make a foreline pump, plus a molecular pump (or other secondary vacuum pump) as a secondary vacuum system;

â—Ž Multi-stage pressure sensor with accurate measurement of 10 ^-3 Pa; precise control system with low pressure and lower pressure; the controllable point in P/Po<0.1 should exceed 100 points;

â—Ž Special microporous analysis software is required: HK, FS or NLDFT;

â—Ž The isothermal adsorption curve of P/Po between 10 ^-7 and 10 ^-1 can be accurately determined;

Accurate determination of total pore volume, pore volume / pore size from 0.35 to 2nm /

Pore ​​size distribution

And the most possible aperture.