As penetration of gases into, release out and diffusion inside solids depend strongly on the structure of materials, nanostructured materials are expected to exhibit peculiar behaviour when they are exposed to gases. Moreover, some of the nanocrystalline composites empower chemical reaction among adsorbed gases, so applications in the field of catalysis can be considered. That’s why knowledge of the solubility and the diffusion coefficient is of great importance from practical point of view, recently.
Determination of the solubility and the diffusion coefficients is frequently performed through a measurement of gas contents in the considered material under well defined conditions and gas flow from the material during variation of the material temperature. An experimental system is described that enables to measure the flow of gas from a sample at various temperatures. The system consists of a uhv chamber containing a device for heating the sample according to a requested schedule, a mass spectrometer and an ionisation gauge. To the vacuum chamber is also connected another vacuum system where samples can be exposed by different gases at various temperatures and pressures. The flow of the released gas is estimated from time-pressure curves measured by a mass spectrometer. An amount of a gas that was previously contained in the sample is then obtained by integration of the time- pressure curves over the relevant time period.
Exploiting of the apparatus, a study of water vapour interaction with the MgO-based composites were studied. Nanopowder consisting of MgO, Fe-Ni intermetallic and small amount of Fe was prepared by spark erosion of pure Mg and Ni3Fe. Gas release at temperature variations was measured from samples as prepared or exposed to the natural atmosphere or water vapour at various temperatures and pressures. A huge adsorption capacity for water was found. Surprisingly, release of carbon dioxide from samples into vacuum even at the room temperature was observed when water was contained in the sample and the release was not stopped until water was depleted completely.
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