Specific surface area analyser: Sorbtometer–M

  The main methods of adsorption value determination are volumetric and gravimetric methods, and also a method of thermal desorption. They have several advantages compared with static methods: they do not require vacuum equipment, the device is easy to install, does not use mercury, which is always used in standard methods. What is more, it is automated, what to great extent determines high productivity.

  The main procedure of analyser is based on the method of the adsorbate (nitrogen) thermal desorption in dynamic conditions. In this method, the fixed stream of helium-nitrogen (or other gas mixture) with adjusted structure passes through the adsorber with the sample. Before the experiments with samples start the decontamination is required. It is the process when the sample is heated in permanent stream of gas with the fixed temperature with the aim of removing the previously adsorbed gases from the surface of the sample.

  During the experiments the following operations are held:

·         Adjustment of gas mixture.

·         Adsorption of the gas on the surface of the sample from the stream of mixed gases with the temperature of liquid nitrogen until the balance of the adsorbate gas contents in gas and adsorption phases are not reached.

·         Desorption of the adsorbed gas, heating the sample up to the temperature of full desorption of the adsorbed gas.

  During the adsorption-desorption processes the volumetric part of the adsorbed gas in mixture changes. This process is recorded using thermal conductivity detector (TCD). TCD's output signal is a peak of higher concentration of the adsorbed gas, transformed in the electrical signal during its thermal desorption from the sample's surface. The integral area of this peak value is proportional to the volume of the gas, desorbed from the sample. Thus, as a result of the experiments, the volume of the gas, adsorbed by cooling (adsorption) and desorbed by heating, is measured. The result of measuring the volume of the gas, adsorbed at the temperature of liquid nitrogen at different content of gas mixture, is the adsorption-desorption isotherm.


  Although the goals of sorbtometrics are quite monotonous - the study of the porosity of the sample, namely sorption characteristics, may the best to show the internal structure of the material.

  For the example, adsorption curve of porous anodic aluminum oxide and desorption curve of porous anodic titanium oxide can be brought.

  Thus, the main area - is the study of porous nanostructures.