Test - lowercase jpg
Kaixin micro test
Test probe P100-M3
Electric Power Components,Multi-Function Power Instrument,Cckem6 Three-Phase Multi-Function,Three Phase Power Monitoring
ZHONG HAN INTERNATIONAL TRADE CO., LTD , https://www.cck-ht.com
Skip to content
![]()
![]()
![]()
![]()
![]()
![]()
(1) The dynamic method, also known as continuous flow chromatography, involves performing nitrogen adsorption in a flowing atmosphere containing nitrogen at liquid nitrogen temperature. This technique allows for achieving dynamic equilibrium of adsorption under varying nitrogen partial pressures. If the sample tube is removed from the liquid nitrogen and allowed to warm up to room temperature, all the adsorbed nitrogen will be released. To measure each pressure point, the sample tube must be repeatedly inserted into and removed from the liquid nitrogen cup, making this process both precise and time-consuming.
(2) This method relies on helium as the carrier gas, since helium is not adsorbed at liquid nitrogen temperatures. By adjusting the ratio of nitrogen to helium or controlling their flow rates without changing the total gas pressure, different nitrogen partial pressures can be achieved. The pressure of the flowing gas mixture is approximately atmospheric. The nitrogen partial pressure is calculated as the nitrogen flow rate divided by the total flow of helium and nitrogen. This partial pressure can range from 0 to nearly atmospheric pressure, and no vacuum conditions are required.
(3) Continuous flow chromatography gets its name from the use of a thermal conductivity detector to measure the amount of nitrogen adsorption. The sample tube is placed in series between the reference arm and the measuring arm of the thermal conductivity detector. When the sample adsorbs or desorbs nitrogen, it causes an imbalance in the thermal conductivity cell, resulting in an electrical signal. This signal produces an adsorption or desorption peak, with the area under the peak proportional to the amount of nitrogen adsorbed or desorbed. A standard reference sample is used to determine the exact amount of nitrogen. Due to the significant difference in thermal conductivity between helium and nitrogen, even small changes in nitrogen concentration greatly affect the thermal conductivity, increasing the sensitivity of the detector.
(4) One major advantage of the dynamic surface area meter is its ability to directly compare specific surface areas. This is done by using a standard sample with a known surface area. Under a fixed nitrogen partial pressure (typically a nitrogen/helium ratio of 0.2), the specific surface area of the unknown sample is calculated by comparing its desorption peak area with that of the standard. This method is fast and suitable for online testing in production environments. However, it does not account for differences in adsorption behavior between materials, which may lead to inaccuracies when the sample's adsorption characteristics differ significantly from the standard.
(5) The BET method addresses these limitations by allowing the adjustment of nitrogen partial pressure and reaching a steady state. A dynamic BET-specific surface area instrument can also perform direct comparison measurements by setting the nitrogen partial pressure to 0.2 or 0.3 and using a standard sample. This approach provides more accurate results by accounting for the adsorption behavior of the material, making it more reliable for a wide range of samples.